Pierre Tattevin
email: pierre.tattevin@chu-rennes.fr

Jean-Luc Mainardi

2015 pour la prise en charge des endocardites infectieuses Analysis of the 2015 American and European guidelines for the management of infective endocarditis

Keywords: endocardite infectieuse, recommandations, Staphylococcus aureus, Streptococcus sp., tomographie par émission de infective endocarditis, guidelines, Staphylococcus aureus, Streptococcus sp., positron emission tomography

Résumé

La prise en charge optimale des endocardites infectieuses nécessite le recours à des expertises multiples (infectiologues, cardiologues, microbiologistes, chirurgiens cardiaques, réanimateurs). En l'absence de haut niveau de preuves pour la plupart des étapes de cette prise en charge, les recommandations internationales ont toujours été particulièrement attendues dans ce domaine, et dans l'ensemble plutôt bien respectées. L'analyse rigoureuse des données de la littérature, et les expertises qui composent les groupes multidisciplinaires chargés de ces recommandations, font en général autorité.

Dans ce contexte, la publication à quelques semaines d'écart, en 2015, des révisions des recommandations américaines et européennes, a semé le trouble. On y retrouve des discordances nettes sur des propositions thérapeutiques importantes comme le traitement empirique (pénicilline M + pénicilline A + gentamicine pour les européens dans les endocardites aiguës sévères ; pénicilline A + inhibiteur de bêta-lactamases + gentamicine pour les américains), ou le traitement de première intention des endocardites à Staphylococcus aureus, principal pathogène responsable d'endocardites en 2016 (triméthoprime-sulfaméthoxazole + clindamycine en alternative dans les recommandations européennes, tandis que ce régime n'est pas même mentionné dans les recommandations américaines). D'autres différences sont observées, moins radicales : la place de la tomographie par émission de positons marquée au 18

A c c e p t e d m a n u s c r i p t

Abstract

The optimal management of infective endocarditis requires a broad range of expertise (infectious disease specialists, cardiologists, microbiologists, cardiac surgeons, and intensivists). Given the low level of evidence currently available to support the management of infective endocarditis, international guidelines have always been particularly awaited and rather well implemented. Their cautious analysis of the medical literature and the range of expertise combined within the groups in charge of these guidelines are usually broadly acknowledged and respected.

The publications, a few weeks apart, of the 2015 updates of the American and European guidelines, was quite disturbing. Indeed, several discrepancies on major therapeutic propositions were observed, including empirical treatment (penicillin M + penicillin A + gentamicin for Europeans in acutely ill patients; penicillin A + beta-lactamase inhibitor + gentamicin for Americans), or first-line treatment for the most common pathogen responsible for endocarditis in 2016, Staphylococcus aureus (trimethoprimsulfamethoxazole + clindamycin as an alternative in European guidelines, while this regimen is not even mentioned in the American guidelines). Other discrepancies were observed, although less significant: the role of positron emission tomography labelled with 18 F-fluorodeoxyglucose and administration modalities for aminoglycosides.

We aimed to detail the main changes brought upon by these guidelines, their discrepancies, and the 'pros' and 'cons' that may help you select the best treatment regimen for your patients.

A c c e p t e d m a n u s c r i p t

The simultaneous publication of the American [START_REF] Baddour | Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association[END_REF] and European [START_REF] Habib | ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC)Endorsed by: European Association for Cardio-Thoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM)[END_REF] guidelines on infective endocarditis highlights, for the first time, the arbitrary choices made to compile these recommendations. Although based on the same literature analysis and drafted by experts used to share knowledge, the American and European guidelines do not put forward the same treatment suggestions. Discrepancies could already be observed in previous versions but they were less significant than the ones observed in the 2015 guidelines, and could partly be justified by the development of scientific knowledge that took place in-between the publication dates (American guidelines: 2005; European guidelines: 2009). This kind of argument cannot be advanced with the 2015 updates as both guidelines were drafted and published at the same time.

A) American guidelines [START_REF] Baddour | Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association[END_REF] The new recommendations:

-take into consideration the growing complexity and diversity of these diseases, and advocate for a multidisciplinary and individual management of patients presenting with a suspicion of endocarditis; -highlight that this complexity has led experts to no longer recommend a "universal" empirical antibiotic therapy for endocarditis. The American updates rather suggest to consider characteristics on a case-by-case basis and suggest using a specific table

(Epidemiological factors influencing the etiological diagnosis of infective endocarditis).

The main causes for each specific situation are summarized in this table, which must be used for empirical antibiotic therapy decision when indicated; -stress that the need for an urgent initiation of antibiotic therapy in case of an endocarditis suspicion remains rare and that the most common mistake lies in excessive prescriptions that lead to problematic situations of undocumented endocarditis.

Antibiotic therapies recommended in the 2015 updates come as no surprise. The main modifications suggested were already implemented by many physicians given the publication date of the previous guidelines. The authors of the latter guidelines admitted that they ought to be updated on a more regular basis in light of the evolution of resistance profiles and scientific progress. We aimed to highlight the main discrepancies A c c e p t e d m a n u s c r i p t between the 2015 and 2005 American guidelines. As we did not always agree on the recommendations, we decided to discuss them on the basis of pros and cons arguments.

1) Antibiotic therapy a) S. aureus endocarditis and aminoglycosides

The 2015 American and European updates no longer suggest using aminoglycosides in the treatment of native valve staphylococcal endocarditis, regardless of the sensitive or resistant nature of the strain to methicillin. American and European guidelines both recommend to keep using gentamicin during the first two weeks of treatment for prosthetic valve staphylococcal endocarditis: two or three injections/day for Americans, and one or two injections/day for Europeans.

Pierre Tattevin (Pro). It was time to make official what was already implemented by many experts: the efficacy of aminoglycosides has never been proven in staphylococcal endocarditis, even when evaluated in a randomized study [START_REF] Ribera | Effectiveness of cloxacillin with and without gentamicin in short-term therapy for right-sided Staphylococcus aureus endocarditis. A randomized, controlled trial[END_REF]. Conversely, recent data demonstrated their deleterious effect, even when administered for a few days [START_REF] Cosgrove | Initial low-dose gentamicin for Staphylococcus aureus bacteremia and endocarditis is nephrotoxic. Clinical infectious diseases : an official publication of the[END_REF].

Jean-Luc Mainardi (Con).

Suggesting to no longer use aminoglycosides in the treatment of staphylococcal endocarditis is based on the lack of evidence supporting the benefit of the two-drug combination therapy versus monotherapy on mortality [START_REF] Watanakunakorn | Prognostic factors in Staphylococcus aureus endocarditis and results of therapy with a penicillin and gentamicin[END_REF].

However, adding gentamicin to a beta-lactam or a glycopeptide regimen is associated with a good in vitro synergy rapidly leading to bactericidal activity [START_REF] Sande | Antimicrobial therapy of experimental endocarditis caused by Staphylococcus aureus[END_REF], especially as glycopeptides alone have a slow bactericidal activity [START_REF] Grohs | In vitro bactericidal activities of linezolid in combination with vancomycin, gentamicin, ciprofloxacin, fusidic acid, and rifampin against Staphylococcus aureus[END_REF]. The results of studies based on animal models, conducted as early as 1975 by Sande & Johnson, also demonstrated that an aminoglycoside + beta-lactam combination therapy was associated with a more rapid bacterial eradication from blood cultures and vegetations compared with a beta-lactam regimen alone [START_REF] Sande | Antimicrobial therapy of experimental endocarditis caused by Staphylococcus aureus[END_REF].

Considering these arguments, many facilities involved in the management of patients presenting with native valve staphylococcal endocarditis are expected to keep on using the beta-lactam or glycopeptide + gentamicin combination during the initial phase (3 to 5 days) as the benefit of this regimen has been demonstrated during this phase in the animal model. Conversely, it should be noted that aminoglycosides are still being recommended for the first 14 days of prosthetic valve endocarditis treatment, while there is no major evidence supporting such regimen. In my opinion, administering A c c e p t e d m a n u s c r i p t aminoglycosides twice daily (instead of three times a day due to an increased risk of toxicity) seems to be adequate to obtain a synergistic effect.

b) Streptococcal endocarditis and aminoglycosides

Gentamicin must be administered with a single daily dose of 3 mg/kg for streptococcal endocarditis.

Pierre Tattevin (Pro). This is once again a retrospective validation of an already widely implemented (especially in France [START_REF] Beraud | A survey on the use of gentamicin in infective endocarditis. European journal of clinical microbiology & infectious diseases[END_REF]), evidence-based practice (better tolerability and effectiveness of aminoglycosides with a single daily administration).

Jean-Luc Mainardi (Con). Aminoglycosides do not have any inherent activity against

Streptococcus species due to their naturally low level of resistance, with a minimum inhibitory concentration (MIC) ranging from 0.5 to 2 mg/L. Aminoglycosides are not used to obtain an optimal peak concentration, but rather to obtain a synergy with a betalactam or a glycopeptide. As aminoglycosides have a biological half-life of approximately two hours, the once daily administration does not allow patients with a normal renal function to maintain a sustained blood concentration of gentamicin over 24 hours as well as a sustained synergy over a 24-hour period. Therefore, administering aminoglycosides twice daily seems to make more sense to obtain a sustained synergy over 24 hours.

c) Daptomycin and methicillin-resistant staphylococcal endocarditis

The European and American guidelines suggest using daptomycin as a first-line alternative in the treatment of methicillin-resistant staphylococcal endocarditis. They advocate for a higher dose than the one recommended in the product marketing authorization: 10 mg/kg/day in Europe and >8 mg/kg/day in the United-States.

Jean-Luc Mainardi, Pierre Tattevin (con).

Although cohort studies demonstrated the good outcome associated with the use of daptomycin in the treatment of left-sided endocarditis [START_REF] Carugati | High-dose daptomycin therapy for left-sided infective endocarditis: a prospective study from the international collaboration on endocarditis[END_REF][START_REF] Kullar | A multicentre evaluation of the effectiveness and safety of high-dose daptomycin for the treatment of infective endocarditis[END_REF], it should be reminded that it has only been approved in the treatment of right-sided endocarditis where it only demonstrated a non-inferiority versus conventional treatments [START_REF] Fowler | Daptomycin versus standard therapy for bacteremia and endocarditis caused by Staphylococcus aureus[END_REF].

d) Enterococcal endocarditis

A c c e p t e d m a n u s c r i p t

Enterococcal endocarditis may either be treated with a combination of penicillin (A or G) and gentamicin (2-3 injections/day, 3 mg/kg) for four to six weeks, or with a combination of penicillin A (12 g/day) and ceftriaxone (2 g twice daily) for six weeks.

Pierre Tattevin, Jean-Luc Mainardi (Pro). We expected this combination of two betalactam antibiotics to be recommended as a first-line alternative in light of the Spanish publications following studies showing evidence of an in vitro synergy between amoxicillin and third-generation cephalosporins (cefotaxime, ceftriaxone) by inhibition synergy on targets [START_REF] Mainardi | Synergistic effect of amoxicillin and cefotaxime against Enterococcus faecalis[END_REF]. However, we cannot help but notice that the American guidelines did not take into consideration Scandinavian publications that strongly suggested discontinuing aminoglycosides after two weeks of treatment when favoring the penicillin-gentamicin combination for enterococcal endocarditis. The European guidelines are rather more innovative on that matter [START_REF] Habib | ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC)Endorsed by: European Association for Cardio-Thoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM)[END_REF].

2) Imaging techniques

Apart from antibiotic therapy, the American guidelines did not stress the importance of 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET) as much as the European ones [START_REF] Habib | ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC)Endorsed by: European Association for Cardio-Thoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM)[END_REF]. Indeed, the latter decided to define FDG PET as a major Duke criterion in the presence of hyperactivity near a prosthetic valve implanted >3 months earlier.

Pierre Tattevin, Jean-Luc Mainardi (Con)

The cautious approach adopted by the American guidelines may be justified by the still limited data available on the diagnostic benefit of FDG PET. However, ongoing studies (e.g., national hospital programs for clinical research: ENDOPET and TEPvENDO in France) should provide robust data on the use of this technique. It should also be noted that Duke criteria were approved on the basis of thorough studies evaluating their efficacy in various populations. New imaging techniques have yet to be validated by this kind of studies. Defining the PET results as "major Duke criteria" for the diagnosis of prosthetic valve endocarditis is quite premature.

3) Anticoagulation

The American guidelines sometimes promote a more audacious approach than the European ones, especially when suggesting to "discontinue all anticoagulation in patients with S. aureus prosthetic valve IE who have experienced a recent central A c c e p t e d m a n u s c r i p t nervous system embolic event for at least the first two weeks of antibiotic therapy" (all the while admitting to the low level of evidence -C -supporting this recommendation [START_REF] Baddour | Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association[END_REF]).

Jean-Luc Mainardi and Pierre Tattevin do not agree with this item. B) Particularities of the European guidelines a) Trimethoprim-sulfamethoxazole + clindamycin combination therapy

The main particularity of the European guidelines lies in their promoting as an alternative, and regardless of intolerance, allergy, or resistance, the high dose combination of trimethoprim-sulfamethoxazole (960 mg/day of trimethoprim, 4,800 mg/day of sulfamethoxazole) for six weeks with clindamycin (1,800 mg/day) for one week in the treatment of native valve S. aureus endocarditis.

Pierre Tattevin, Jean-Luc Mainardi (con). This combination is not mentioned in the American guidelines, but Europeans justify its use by the positive opinion of some experts and put forward the results of a single center observational study of 31 patients [START_REF] Casalta | Treatment of Staphylococcus aureus endocarditis with high doses of trimethoprim/sulfamethoxazole and clindamycin-Preliminary report[END_REF]. However, the authors of two larger randomized studies strongly suggest that co-trimoxazole is not as effective as vancomycin in the treatment of S. aureus bacteremia [START_REF] Markowitz | Trimethoprim-sulfamethoxazole compared with vancomycin for the treatment of Staphylococcus aureus infection[END_REF][START_REF] Paul | Trimethoprim-sulfamethoxazole versus vancomycin for severe infections caused by meticillin resistant Staphylococcus aureus: randomised controlled trial[END_REF], and that treating endocarditis with clindamycin could be associated with an increased risk of early relapse due to resistance selection [START_REF] Watanakunakorn | Clindamycin therapy of Staphylococcus aureus endocarditis. Clinical relapse and development of resistance to clindamycin, lincomycin and erythromycin[END_REF]. Moreover, the potential hematotoxicity of trimethoprim-sulfamethoxazole during six weeks when administered at such high doses (similar dosing as the one recommended in the curative treatment of pneumocystis but over a treatment period twice as long) is mentioned neither in the original publication of the regimen [START_REF] Casalta | Treatment of Staphylococcus aureus endocarditis with high doses of trimethoprim/sulfamethoxazole and clindamycin-Preliminary report[END_REF] nor in the guidelines [START_REF] Habib | ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC)Endorsed by: European Association for Cardio-Thoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM)[END_REF].

However, this hematotoxicity is quite significant if we take into consideration the tolerability profile of the combination therapy.

b) Empirical treatment of endocarditis

The other major discrepancy between the European and American guidelines lies in the empirical treatment of severe presentations of acute community-acquired endocarditis.

The 2015 European updates recommend the use of penicillin A (ampicillin, 12 g/day) + penicillin M (cloxacillin or oxacillin, 12 g/day) + gentamicin (3 mg/kg/day) [START_REF] Habib | ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC)Endorsed by: European Association for Cardio-Thoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM)[END_REF], while A c c e p t e d m a n u s c r i p t the 2009 guidelines recommended combining amoxicillin-clavulanic acid or ampicillinsulbactam (12 g/day) with gentamicin (3 mg/kg/day) [START_REF] Habib | Guidelines on the prevention, diagnosis, and treatment of infective endocarditis (new version 2009): the Task Force on the Prevention, Diagnosis, and Treatment of Infective Endocarditis of the European Society of Cardiology (ESC). Endorsed by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and the International Society of Chemotherapy (ISC) for Infection and Cancer[END_REF].

Pierre Tattevin (con). The modification is based on a single evidence: the results of a retrospective cohort study suggesting that treating multidrug-susceptible S. aureus bacteremia with antistaphylococcal beta-lactams (cloxacillin or cefazolin; n=131) would be associated with a better survival versus treatment with a combination of beta-lactam + beta-lactamase inhibitor (n=98) [START_REF] Paul | Are all beta-lactams similarly effective in the treatment of methicillin-sensitive Staphylococcus aureus bacteraemia? Clinical microbiology and infection : the official publication of the[END_REF]. The benefit of a combination with two high dose penicillins has barely been studied, but several French centers have reported an increase in acute renal failure caused by high dose beta-lactams over the past few years in elderly patients presenting with comorbidities. Most patients presenting with endocarditis in 2016 correspond to this profile. Similar to the new treatment regimen with co-trimoxazole at high doses and clindamycin, we should mention the discrepancies between the factors that brought upon the updates (hypotheses supported by a low level of evidence) and the risks associated with the suggested alternatives (understudied risks with potential major consequences).

Jean-Luc Mainardi (Pro).

Acute severe endocarditis is often caused by S. aureus. This three-drug combination therapy including a penicillin M has the advantage of covering S. aureus and getting rid of the problem related to the potentially insufficient diffusion of beta-lactamase inhibitors (clavulanic acid) in vegetations. It is thus quite useful to stress that more than 90% of S. aureus strains produce a penicillinase. The tolerability of a treatment regimen with two beta-lactams is a real issue, but it is useful to remind that: i) the empirical treatment of acute endocarditis is usually of short duration as diagnosis is established within 48 hours in more than 95% of cases; and that ii) Spanish studies of enterococcal endocarditis did not report any increase in the risk of renal failure with the combination regimen of ampicillin (12 g) and ceftriaxone (4 g) when administered for six weeks [START_REF] Fernandez-Hidalgo | Ampicillin plus ceftriaxone is as effective as ampicillin plus gentamicin for treating enterococcus faecalis infective endocarditis. Clinical infectious diseases : an official publication of the[END_REF][START_REF] Pericas | Changes in the treatment of Enterococcus faecalis infective endocarditis in Spain in the last 15 years: from ampicillin plus gentamicin to ampicillin plus ceftriaxone. Clinical microbiology and infection : the official publication of the[END_REF].

Although the 2015 European and American updates both insist on the importance of a multidisciplinary and individual approach by an "endocarditis team" consisting of cardiologists, cardiac surgeons, infectious disease specialists, microbiologists, and anesthesiologists, the predominance of cardiac specialties among the authors of the 2015 European guidelines must be pointed out. Noteworthy, unlike the 2009 updates "Two-week regimen": penicillin G or ceftriaxone + gentamicin (single daily dose) "Four-week regimen": penicillin G or ceftriaxone "Two-week regimen": penicillin G or amoxicillin or ceftriaxone + gentamicin (single daily dose) "Four-week regimen": penicillin G or amoxicillin or ceftriaxone

Susceptible enterococcal endocarditis

Regimen "A": penicillin G or ampicillin + gentamicin (2 or 3 uptakes/day) for 4 to 6 weeks Regimen "B": ampicillin + ceftriaxone for 6 weeks Regimen "A": amoxicillin (4 to 6 weeks) + gentamicin (single daily dose for 2 to 6 weeks) Regimen "B": ampicillin + ceftriaxone for 6 weeks * Including endocarditis of prosthetic valve implanted >1 year earlier. ** Rifampicin is only indicated in the presence of a prosthetic valve and, according to some experts, should be introduced later on (5 to 7 days after antibiotic therapy initiation).

  Ffluorodésoxyglucose et les modalités d'administration des aminosides. Nous détaillerons les principaux changements apportés par ces recommandations, leurs désaccords et les arguments pour et contre qui peuvent vous aider à sélectionner le meilleur traitement pour vos patients.

Tableau 1 .

 1 Principales antibiothérapies de première ligne dans les recommandations européennes et américaines 2015 de prise en charge des endocardites infectieuses

A

  c c e p t e d m a n u s c r i p t

Table 1 .

 1 Main first-line antibiotic therapies included in the 2015 European and American guidelines for the management of infective endocarditis

		2015 American guidelines	2015 European guidelines
	Empirical	Depends on symptom evolution	Community-acquired (severe
	antibiotic	and epidemiological factors	presentation): * ampicillin +
	therapies		(cl)oxacillin + gentamicin
			Nosocomial:
			vancomycin + gentamicin +
			rifampicin **
	Native valve	Methicillin-susceptible:	Methicillin-susceptible:
	staphylococcal	(cl)oxacillin	(cl)oxacillin
	endocarditis	Methicillin-resistant:	Methicillin-resistant:
		vancomycin or daptomycin	vancomycin or daptomycin
			Alternative (in both of the above
			situations):
			trimethoprim-sulfamethoxazole
			+ clindamycin
	Prosthetic valve	Methicillin-susceptible:	Methicillin-susceptible:
	staphylococcal	(cl)oxacillin + gentamicin (2 or	(cl)oxacillin + gentamicin (1 or 2
	endocarditis	3 uptakes/day) + rifampicin	uptakes/day) + rifampicin
		Methicillin-resistant:	Methicillin-resistant:
		vancomycin + gentamicin (2 or	vancomycin + gentamicin (1 or
		3 uptakes/day) + rifampicin	2 uptakes/day) + rifampicin
	Susceptible
	streptococcal
	endocarditis

and the 2015 American guidelines, the 2015 European updates have not been approved by any infectious disease society before being published.

Conflicts of interest

The authors report no conflict of interest.

Contributions

PT and JLM equally contributed to writing the article after vigorous but always friendly debates.

A c c e p t e d m a n u s c r i p t


Maud Deniau
email: maud.deniau@sfr.fr

Vincent Jung

Cécile Le Lann

Thibault Morra

Phil J Murray

Andreas Prinzing

Janzen-Connell patterns are not the result of Janzen-Connell process: oak recruitment in temperate forests

Keywords: budburst, community dynamics, intraspecific and interspecific facilitation, leaf herbivory, plant population, Quercus sp

Highlights

• Janzen-Connell suggests high enemy pressure on seedlings close to conspecific adults • However, conspecific adults also improve the microenvironment for seedlings

• Heterospecific adults are refuge for seedlings, not conspecific adults a danger

• JC-like patterns may result from non-JC processes, with very different consequences

Introduction

A major challenge in community ecology is to understand mechanisms promoting species diversity in forests. Many mechanisms have been suggested [START_REF] Wright | Plant diversity in tropical forests: a review of mechanisms of species coexistence[END_REF], but the Janzen-Connell (JC) hypothesis [START_REF] Connell | On the role of natural enemies in preventing competitive exclusion in some marine animals and in rain forest trees[END_REF][START_REF] Janzen | Herbivores and the number of tree species in tropical forests[END_REF] remains widely used. According to the JC hypothesis, seedlings will suffer from proximity to conspecific adult trees (or closely related adults, see [START_REF] Liu | Experimental evidence for a phylogenetic Janzen-Connell effect in a subtropical forest[END_REF] because of high pressure from specialized natural enemies. Seedlings of other species will thus be able to establish under the adult tree, thereby increasing species diversity of communities. The JC hypothesis has been confirmed multiple times in both tropical (e.g. [START_REF] Bagchi | Pathogens and insect herbivores drive rainforest plant diversity and composition[END_REF][START_REF] Clark | Spacing dynamics of a tropical rain forest tree: evaluation of the Janzen-Connell model[END_REF][START_REF] Comita | Testing predictions of the Janzen-Connell hypothesis: a meta-analysis of experimental evidence for distance-and density-dependent seed and seedling survival[END_REF] and temperate forests (e.g. [START_REF] Comita | Testing predictions of the Janzen-Connell hypothesis: a meta-analysis of experimental evidence for distance-and density-dependent seed and seedling survival[END_REF][START_REF] Masaki | Seedling demography of Swida controversa: effect of light and distance to conspecifics[END_REF][START_REF] Packer | Soil pathogens and spatial patterns of seedling mortality in a temperate tree[END_REF][START_REF] Seiwa | Pathogen attack and spatial patterns of juvenile mortality and growth in a temperate tree, Prunus grayana[END_REF] but does not always hold true and is still debated [START_REF] Hyatt | The distance dependence prediction of the Janzen-Connell hypothesis: a meta-analysis[END_REF]. One aspect that has been largely overlooked is that a JC pattern (i.e. a decline of seedlings close to conspecific or closely related adults) might also result from other processes: (1) heterospecific adults might positively affect seedlings (rather than negative effect of conspecific or closely related adults), and (2) conspecific (or closely related) adults might negatively affect seedlings by causing a deterioration of the microenvironment (rather than by increasing enemy pressure).

A JC pattern may result from a reduced enemy pressure close to heterospecific adults, rather than from an increased enemy pressure close to conspecific adults. An adult tree is a reservoir of specialized enemies, aggregating nearby the adult tree [START_REF] Connell | On the role of natural enemies in preventing competitive exclusion in some marine animals and in rain forest trees[END_REF][START_REF] Janzen | Herbivores and the number of tree species in tropical forests[END_REF]. Hence, a heterospecific adult attracts its own specialized enemies, which are not able to attack proximate focal seedlings due to a conservatism of biotic interactions (see [START_REF] Winkler | The phylogenetic dimension of insect/plant interactions: a summary of recent evidence[END_REF]. Heterospecifics might even hinder the detection of focal seedlings by their enemies [START_REF] Jactel | Non-host volatiles disrupt the response of the stenographer bark beetle, Ips sexdentatus (Coleoptera: Scolytidae), to pheromonebaited traps and maritime pine logs[END_REF]. Heterospecific adults may thus represent a refuge for focal seedlings by decreasing enemy pressure, thereby improving seedling survival. Overall, a reduction of the enemy pressure close to heterospecific adults could be a non-JC process inducing a JC-like pattern, but with very different consequences: seedlings of focal species would establish below heterospecifics instead of heterospecifics below focal species (see also [START_REF] Rutten | Plant-soil feedback in East-African savanna trees[END_REF].

A JC pattern may also result from a deterioration of the microenvironment of seedlings by conspecific adults, or from an improvement of the microenvironment of seedlings by heterospecific adults. Adult trees might affect some or all of the following aspects of the microenvironment all influencing seedling survival; litter decomposition and chemistry, the physical structure of the microenvironment, and the microclimate and composition of the herbaceous layer. Moreover, the effect of adult trees on the microenvironment may be species-specific, resulting in a detrimental microenvironment under conspecific adult trees and in a beneficial microenvironment under heterospecific adult trees. This is often the case during ecological succession when a plant species improves the microenvironment for heterospecific seedlings and late-successional species profit from the microenvironments produced by early-successional species depending on repetitive disturbances.

For instance, soil characteristics might differ between tree species due to the physical and chemical properties of their litter [START_REF] Binkley | The influence of tree species on forest soils: processes and patterns[END_REF]. Different tree species might also differ in soil moisture because rain interception depends on species-specific tree characteristics (e.g. branch angle, bark type; [START_REF] Crockford | Partitioning of rainfall into throughfall, stemflow and interception: effect of forest type, ground cover and climate[END_REF]. Finally, evolutionary distant adult trees might have a very different impact on their microenvironment compared to the focal species. For example, Gymnosperms produce less litterfall than Angiosperms, and also a more acidic litter hence resulting in a lower soil pH [START_REF] Sariyildiz | Effects of tree species and topography on soil chemistry, litter quality, and decomposition in Northeast Turkey[END_REF]. The stemflow is also very low for Gymnosperms [START_REF] Crockford | Partitioning of rainfall into throughfall, stemflow and interception: effect of forest type, ground cover and climate[END_REF]. If the impact of adult trees on their proximate microenvironment changed gradually with evolutionary position, the resulting effect on seedling survival may be more similar between a conspecific adult and a closely related than a distantly related adult. Overall, a deterioration of the microenvironment by conspecific (or closely related) adults, and an improvement of the microenvironment by heterospecific (or distantly related) adults could both be non-JC processes inducing a JC pattern.

The impact of a tree on proximate seedlings might be reinforced with the size of that tree.

Larger adult trees have a larger crown and a larger root system, so they could accumulate more specialized enemies than smaller adults (see Packer andClay, 2000, referring to Janzen, 1970).

Moreover, larger adult trees are mostly older and have affected their microenvironment for a longer period, intensifying their specific microenvironmental conditions. Also, the impact of a large adult tree on proximate seedlings potentially extends over a greater spatial distance. Size may even impact seedlings more strongly than distance does. Overall, the visibility of a JC pattern might be reinforced with the size of the tree (see Packer andClay, 2000, referring to Janzen, 1970), regardless of the process involved: the negative effect of a large conspecific adult may increase with the size of that tree, just as the positive effect of a heterospecific adult.

We tested the above hypotheses on alternative processes inducing a JC pattern, using oaks (Quercus) as study model, in a temperate forest. Natural regeneration of temperate forests is usually described as depending on light and thus on the creation of canopy gaps (about gap theory, see [START_REF] Yamamoto | The gap theory in forest dynamics[END_REF]. Creation of canopy gaps induces a gradient of light quality and hence of regeneration niches. Some of those niches will correspond to the high-light requirement of temperate oak trees, known to be relatively shade-intolerant [START_REF] Ellenberg | Zeigerwerte von Pflanzen in Mitteleuropa[END_REF]. We studied seedlings because it is at this stage that the JC signal has been described to be the strongest [START_REF] Comita | Testing predictions of the Janzen-Connell hypothesis: a meta-analysis of experimental evidence for distance-and density-dependent seed and seedling survival[END_REF][START_REF] Connell | On the role of natural enemies in preventing competitive exclusion in some marine animals and in rain forest trees[END_REF][START_REF] Hyatt | The distance dependence prediction of the Janzen-Connell hypothesis: a meta-analysis[END_REF]. We planted oak seedlings as phytometers in order to avoid bias due to local acclimatization or selection. We measured seedling mortality and processes controlling seedling mortality (budburst and leaf herbivory). Mortality decreases with physiological performance, and a core characteristic of performance in seedlings is budburst and particularly an early budburst [START_REF] Augspurger | Early spring leaf out enhances growth and survival of saplings in a temperate deciduous forest[END_REF][START_REF] Besford | Photoperiod effect on bud burst in Prunus is phase dependent: significance for early photosynthetic development[END_REF][START_REF] Seiwa | Advantages of early germination for growth and survival of seedlings of Acer mono under different overstorey phenologies in deciduous broad-leaved forests[END_REF], allowing photosynthesis and nutrient acquirement during the best light conditions, before the closure of the canopy. Mortality of seedlings also increases with leaf herbivory [START_REF] Moles | What do seedlings die from and what are the implications for evolution of seed size?[END_REF][START_REF] Wada | Effects of herbivore-bearing adult trees of the oak Quercus crispula on the survival of their seedlings[END_REF] by removing photosynthetic tissues. Even low levels of herbivory may strongly increase seedling mortality given their small overall leaf area. Firstly, we tested the classical prediction of JC hypothesis, i.e. that proximity to conspecific adult tree increases seedling mortality, lack and delay of budburst and leaf herbivory. Secondly, we expanded the classical JC hypothesis to other aspects of adult neighbourhood by testing whether heterospecifics or distant relatives decrease seedling mortality, lack and delay of budburst and leaf herbivory, and whether size of trees reinforces the effect of distance or exerts an independent effect. Thirdly, we opened JC hypothesis to the microenvironment. We tested if adults affect litter decomposition and chemistry, physical structure of microenvironment, microclimate and composition of herbaceous layer, in order to estimate if previously identified effects of neighbourhood on seedlings are directly determined by the neighbourhood (potentially due to enemy pressure) or mediated by the microenvironment.

Material and methods

SITE DESCRIPTION

The study was conducted between 2013 and 2015 in the Forest of Rennes, Brittany, France (48°12' N, 1°33' W, ca. 90 m altitude), a semi-natural managed forest with oceanic climate, mean annual temperature of 11.3 °C and cumulated annual rainfall of 836 mm. The soil is a brown-leached soil. This forest is composed of two parcel types dominated by either oak (Quercus petraea hybridizing with Quercus robur) and beech (Fagus sylvatica) or Scots pine (Pinus sylvestris) interspersed with other Angiosperms. The other main tree species in the overstorey are typical from European temperate oceanic lowland forests: Ilex aquifolium, Castanea sativa, Sorbus torminalis, Abies alba and Carpinus betulus (see [START_REF] Yguel | Phytophagy on phylogenetically isolated trees: why hosts should escape their relatives[END_REF] Ten pairs of two adult oak-trees (ca. 60 years old) were selected within the forest (used by [START_REF] Yguel | Phytophagy on phylogenetically isolated trees: why hosts should escape their relatives[END_REF]. Each pair had one tree in the more oak-dominated parcel and one in the more pinedominated parcel, separated by distances of less than 150 m. Selecting adult oak-trees in both types of parcels ensured a large range of evolutionary distance between seedlings and their adult neighbours.

Trees of the same pair were of the same oak species (Q. petraea or Q. robur, not strictly speaking distinct species are always partly hybridized; Yguel personal communication). This blocked design was essential to control for variation among pairs due to different macroenvironments or different sources of seedlings [START_REF] Legendre | Effects of spatial structures on the results of field experiments[END_REF], we thus used 'tree pair' as random factor in further analyses.

EXPERIMENTAL DESIGN

For each of the ten pairs, twenty oak-seedlings (Q. petraea or Q. robur or hybrids) were harvested in January 2013 around the adult oak-tree located in the more oak-dominated parcel (seedlings were too rare in the more pine-dominated parcel). Seedlings were carefully chosen in order to be approximately of the same height/age (ca. 1 year old), morphology, no longer dependent upon stored seed reserves (no acorn attached), have no visible signs of pathologies or damage, and have intact buds. Seedlings were then immediately planted along a 5 m transect perpendicular to the stem of each focal adult oak, with seedlings planted every 50 cm (Fig. 1). A transect length of 5 m ensured that the focal oak was usually the closest conspecific while ensuring also sufficient variation in distance.

CHARACTERIZATION OF ADULT NEIGHBOURS

As we worked inside a forest, each transect of seedlings was surrounded by adult trees other than the focal adult oak, most of which being heterospecifics (Fig. 1). For each seedling, we determined the spatial distance to the stem position of the closest conspecific and of the closest heterospecific adult tree (> 2 m height), hereafter respectively referred as 'conspecific' and 'heterospecific'. Distance to conspecific adult ranges from 0.3 m to 5.0 m (mean 2.5 ± 1.3 m) and distance to heterospecific adult ranges from 0.2 m to 6.8 m (mean 2.4 ± 1.4 m). Note that distance to conspecific and distance to heterospecific adults are not correlated (-0.023; P= 0.74, d.f.= 198). Hence, a seedling which is distant to a conspecific adult is not necessarily close to a heterospecific adult. A seedling can thus be close (or distant) to both conspecific and heterospecific adults. As a proxy of tree size we measured circumference at breast height, which is also related to crown size. When two adult trees were equally close, the average distance and circumference ('size' from hereon) was taken. The evolutionary distance between each focal seedling and the spatially closest adult tree was also quantified (see Appendix A for explanation of the procedure). Again, when two trees were equally close to a seedling, the respective mean evolutionary distance was calculated. Evolutionary distance varies continuously from 0 to 140 million year before present.

MEASUREMENTS OF SEEDLING MORTALITY, BUDBURST AND LEAF HERBIVORY

'Seedling mortality' was quantified for the second year only ( 2014), because we expected that for the first year part of the mortality was due to transplantation. We hence excluded seedlings which died in the first year from analyses. We described seedlings as 'dead' or 'alive'. The cause of the death was not assessed as we were interested in explaining the overall seedling mortality by the microenvironment, without distinction. Seedlings were considered as dead when they were dry and brittle or unearthed or broken at the base (the latter two often occurring due to the seedlings being dry and brittle before).

'Lack of budburst' and 'budburst delay' were estimated in the second year (2014) only to avoid bias due to transplantation, with the survey beginning in February when all seedlings had closed buds, and ceasing in late June when most of the seedlings had burst. We assessed the 'lack of budburst' by noting whether seedlings had burst (i.e. developed a fully-opened bud with leaves) or not during the season of survey. The 'budburst delay' was assessed by following the phenology: seedlings were screened for a fully-opened bud every 3 days until the end of May and approximately every week until the end of June. Day zero of budburst delay was defined as the day the first seedling had burst ( 5March 2014, note that buds of adults burst later). Budburst delay was then calculated as the number of days from day zero necessary for a seedling to develop a fully-opened bud. Only seedlings that had burst during the survey (between February and late June) were accounted for in the budburst delay variable.

'Leaf herbivory' was estimated in the second year (2014), with survey starting when the leaves from the first bud had burst (5 March 2014) and ceasing in late September, when most of the leave damages have occurred [START_REF] Wada | Effects of herbivore-bearing adult trees of the oak Quercus crispula on the survival of their seedlings[END_REF]. Herbivores were mainly Lepidopteran larvae, the major cause of oak defoliation in temperate forests [START_REF] Southwood | Seasonality, abundance, species richness and specificity of the phytophagous guild of insects on oak (Quercus) canopies[END_REF], most of them being monophagous or oligophagous (see [START_REF] Yguel | Phytophagy on phylogenetically isolated trees: why hosts should escape their relatives[END_REF] for a list of the Lepidoptera species found on the focal adult oaks). The number of leaves per seedling was recorded every 3 days until the end of May, and once per month from thereon until September. Such a high temporal resolution of the screening allowed us to identify cases where an entire leaf had been consumed. In late September, the leaf area loss on the remaining leaves of each seedling was visually estimated by the same observer.

For each seedling, total 'leaf herbivory' hence included the leaf area loss on the remaining leaves and the number of leaves totally consumed during the season, following the formula: % leaf herbivory = 100 * (number of leaves totally consumed + (number of remaining leaves * proportion of area consumed from these remaining leaves)) / (number of leaves totally consumed + number of remaining leaves).

MEASUREMENTS OF THE MICROENVIRONMENT

Methodology and justifications of these measurements are given in Appendix B. In short, 26 parameters were studied in the proximity of each seedling: litter decomposition and chemistry, physical structure of the microenvironment, microclimatic conditions and composition of the herbaceous layer: thicknesses of Oi and Oe horizon; decay of oak-leaves and of a standard substrate (cellulose); soil pH; carbon/nitrogen (C/N) ratio in the Oa horizon where seedlings root. The presence of major roots, fine roots, stones and dead wood close to each seedling was characterized, and the relative elevation of the litter surface was determined. Soil temperature and moisture and the percent of canopy openness were measured just before budburst of seedlings. Finally, vegetation cover was assessed around each seedling. Microenvironmental parameters were measured at the beginning of the growing season. Soil temperature and moisture were recorded in the second year (the year of the survey of seedling mortality, budburst and leaf herbivory), as they might vary from year to year. The other remaining parameters are more structural and compositional and less variable and were hence only measured in year 1.

DATA ANALYSIS

All statistical analyses were performed using R version 3.1.1 (R Core Team, 2014) and the following packages: lme4 [START_REF] Barton | Fitting linear mixed-effects models using lme4[END_REF], MuMIn [START_REF] Barton | Fitting linear mixed-effects models using lme4[END_REF], nlme [START_REF] Pinheiro | R: A language and microenvironment for statistical computing[END_REF], piecewiseSEM [START_REF] Lefcheck | piecewiseSEM: piecewise structural equation modelling in R for ecology, evolution, and systematics[END_REF], RVAideMemoire [START_REF] Hervé | RVAideMemoire: diverse basic statistical and graphical functions[END_REF]. We checked for multicollinearity among variables that would be predictive (i.e. among variables characterizing adult neighbours and among variables characterizing the microenvironment), inferred from strong correlations (> unsigned 0.7) among variables, and found none. The experimental design used blocks, thus mixed models were always utilized, with 'tree pair' as random factor. Generalized Linear Mixed Models (GLMMs) were utilized for explaining binomial variables (seedling mortality and lack of budburst) with the binomial error distribution and a logit link function; Linear Mixed Models (LMMs) were utilized for explaining budburst delay and leaf herbivory. The adequacy of the model to data was always checked graphically with residuals-vs-fitted values plot and QQ-plot of the residuals.

We tested the effect of lack of budburst, budburst delay and leaf herbivory on seedling mortality with GLMMs. Budburst delay affected seedling mortality only slightly (z= 1.68, P= 0.094, R²m= 0.039, R²c= 0.039, n= 93), and was hence not considered in the following analyses.

First, seedling mortality, lack of budburst and leaf herbivory were explained by distance to the closest conspecific alone, testing for a classical JC pattern. Variance explained by each model was estimated by calculating the marginal R² (i.e. variance explained by fixed factors only) and the conditional R² (i.e. variance explained by both fixed and random factors) [START_REF] Nakagawa | A general and simple method for obtaining R² from generalized linear mixed-effects models[END_REF].

Secondly, seedling mortality, lack of budburst and leaf herbivory were each explained by all characteristics of the adult neighbourhood included in a single mixed model: distance and size of closest conspecific and closest heterospecific, the corresponding distance:size terms, and evolutionary distance to closest adult, using GLMMs or LMMs as explained above. In order to reduce the number of predictor variables, we conducted best subset research. The best selected model was the one with the lowest corrected Akaike Information Criterion (AICc; [START_REF] Hurvich | Regression and time series model selection in small samples[END_REF]. AICc is recommended instead of AIC when n(sample size)/k(estimated parameters)< 40 [START_REF] Burnham | Model selection and multimodel inference: a practical information-theoretic approach[END_REF]. We verified that conditional R² of the selected model was close to that of the full model containing all independent variables and hence variable selection was unambiguous and did not result in a major loss of information.

Finally, we evaluated whether the effects of neighbouring adults on seedling mortality, or processes controlling seedling mortality (lack of budburst and leaf herbivory) were direct or indirect through the influence of the neighbourhood on the microenvironments. For this purpose, we used piecewise SEM (Structural Equation Modelling) as it allows the use of mixed models and thus the random factor 'tree pair'. We built our piecewise SEM on the linear mixed models explained above and included all neighbourhood variables that significantly influenced either seedling mortality, lack of budburst or leaf herbivory. In a first approach we included all microenvironmental variables significantly influenced by any of the retained neighbourhood variables (in separate regression analyses, see Appendix C). However, such a model contained a high number of variables (29) for the sample size (n= 93), and the fit statistics revealed that the resulting model was not acceptable (Fisher's C statistic, P< 0.05). We thus proceeded with a stricter selection among microenvironmental variables, including only those significantly influencing seedlings (either their mortality, lack of budburst or leaf herbivory). This selection was conducted with mixed models including 'tree pair' as random factor, and the best model was selected according to AICc (see Appendix D for details). A piecewise SEM based on these variables still yielded a bad fit of the model (Fisher's C statistic, P< 0.05), suggesting that important paths were missing. We added those 4 missing paths (detailed in Appendix E) and obtained a good overall fit of the model (Fisher's C statistic, P> 0.05): no paths were missing and the model represented the data well. We refrained from calculating compound paths as some of the underlying models had non-normal error distributions, rendering the precise estimates of parameters incompatible among models.

Results

We observed major variations in budburst delay (from 0 to 106 days, average 48 days) and leaf herbivory (from 0 to 100%, average 60%). Mortality was 64.7% (117/181), after exclusion of the 19 seedlings which died in year one.

Seedling budburst (lack and delay) and leaf herbivory were hypothesized to be processes controlling seedling mortality. Seedling mortality was increased by a lack of budburst (z= 5.98, P< 0.001, R²m= 0.33, R²c= 0.36, n= 181) and by a delayed budburst (z= 1.68, P= 0.094, R²m= 0.039, R²c= 0.039, n= 93). Lack of budburst was much more strictly related to mortality than budburst delay and so we kept lack of budburst only in the analyses. Seedling mortality was increased by a high leaf herbivory (z= 3.02, P= 0.0026, R²m= 0.13, R²c= 0.13, n= 97). Lacking budburst and leaf herbivory are thus processes that contribute to seedling mortality.

WAS THERE A CLASSICAL JANZEN-CONNELL PATTERN?

Proximity to conspecific adult did not influence the mortality of seedlings (z= 1.10, P= 0.27, R²m= 0.0091, R²c= 0.044, n= 181).

Proximity to conspecific adult influenced one of the processes controlling seedling mortality:

seedling budburst lacked at proximity of the conspecific adult (z= 2.10, P= 0.036, R²m= 0.031, R²c= 0.049, n= 181). However, proximity to conspecific adult did not influence the leaf herbivory (t= 0.67, P= 0.50, R²m= 0.0044, R²c= 0.11, n= 97).

DID NEIGHBOURING ADULTS INFLUENCE SEEDLING MORTALITY, LACK OF BUDBURST AND LEAF HERBIVORY?

Accounting for all five variables characterizing adult neighbourhoods allowed us to detect a distinct relationship between neighbourhood and mortality, lack of budburst and leaf herbivory (Table 1): proximity to conspecific adults, again, increased lack of budburst, whatever the size of conspecific adults. Proximity to heterospecific adults decreased leaf herbivory on seedlings, whatever the size of heterospecifics. Finally, having an evolutionary proximate neighbour tended to increase seedling mortality.

WERE EFFECTS OF NEIGHBOURING ADULTS ON SEEDLINGS DIRECT OR MEDIATED BY THE MICROENVIRONMENT?

Proximity to conspecific adult indirectly promoted budburst where there was a lower M. caerulea cover (Fig. 2). We note that the proportion of explained variance for lack of budburst was distinctly increased when considering microenvironment (Table 1 vs. Fig. 2), and that lack of budburst no longer affected seedling mortality.

Proximity to heterospecific adult decreased directly leaf herbivory (Fig. 2), and indirectly through a lower number of F. sylvatica seedlings. Moreover, a low level of leaf herbivory reduced seedling mortality. Proximity to heterospecifics also tended to inhibit budburst through a high M. caerulea cover.

Finally, the evolutionary proximity with the closest adult no longer affected seedling mortality (directly or indirectly), when considering microenvironmental and neighbouring variables (Table 1 vs Fig. 2).

Discussion

In our study system using a simple regression analysis, we did not detect a classical JC pattern, i.e. negative effects of proximate adults on seedlings. However, once we accounted for heterospecifics and evolutionary distances (Table 2) we did detect multiple JC-like patterns. Some of these JC-like patterns (frequent lack of budburst close to conspecifics; high seedling mortality close to closely related adults) were consistent with the JC process (i.e. negative effect of proximity to conspecific or closely related adult) but could be respectively counteracted by a favourable microenvironment or weak with little explained variance. Other JC-like patterns were due to non-JC processes, such as heterospecific adults reducing leaf herbivory and hence decreasing mortality of proximate seedlings. Specifically, reduced leaf herbivory close to heterospecifics was partially explained by a beneficial microenvironment. To our knowledge, this is the most comprehensive characterization of processes that potentially can induce a JC pattern, and the first observation that JC-like patterns could result from processes other than a direct negative effect of the conspecific (or closely related) adult (but see [START_REF] Rutten | Plant-soil feedback in East-African savanna trees[END_REF]. This study demonstrates that JC patterns are mostly the result of non-JC processes, and that the JC process did not result in distinct JC patterns. Spatial pattern of tree recruitment could result from mechanisms other than the one suggested by JC: heterospecific adults constitute refuge from enemies, and these refuges may in some cases be close to conspecifics as distances to con-and heterospecifics are uncorrelated. The result would be establishment of oaks below non-oaks and ultimately a decrease of beta diversity between adult neighbourhoods rather than an increase alpha diversity within.

LIMITATIONS OF OUR STUDY

Our study clearly has limitations, including the ontogenetic stage and time window. First, we found no evidence for classical JC process on the seedling stage, but we cannot exclude that JC process act on other stages (e.g. seeds), as we studied only seedlings. However, a stronger JC process on seeds rather than on seedlings seems unlikely as the study of [START_REF] Connell | On the role of natural enemies in preventing competitive exclusion in some marine animals and in rain forest trees[END_REF] and the meta-analyses of [START_REF] Comita | Testing predictions of the Janzen-Connell hypothesis: a meta-analysis of experimental evidence for distance-and density-dependent seed and seedling survival[END_REF] and [START_REF] Hyatt | The distance dependence prediction of the Janzen-Connell hypothesis: a meta-analysis[END_REF] have found the strongest JC effects on the seedling stage. Second, our study was conducted on a limited window of time (2 years). We cannot exclude that the JC process become detectable after many years of pressure by enemies. In fact, the mortality in year 2 (excluding seedlings which possibly die from transplantation) was 64.7 %, which suggests that many seedlings are still to die as not all those remaining seedlings could become adults. At the same time, the number indicates that what we observed during this 2-year time window is far from irrelevant.

JANZEN-CONNELL PATTERNS RESULTING FROM THE JANZEN-CONNELL PROCESS

EXIST BUT TEND TO BE WEAK OR OVERLAID BY THE MICROENVIRONMENT Consistent with a JC pattern, seedlings were negatively affected by proximity to conspecific adult through a reduction of their budburst (Table 1). This result is consistent with [START_REF] Packer | Soil pathogens and Prunus serotina seedling and sapling growth near conspecific trees[END_REF] showing that proximity to conspecific adults not only affects mortality but also reduces seedling growth. Whilst we found no effect of distance to conspecific adult on leaf herbivory, soil pathogens could be implicated. [START_REF] Packer | Soil pathogens and Prunus serotina seedling and sapling growth near conspecific trees[END_REF] showed that soil pathogens explained the reduced growth of seedlings proximate to a conspecific adult. It has also been shown that some soil pathogens have a detrimental effect on seedling budburst (e.g. [START_REF] Taylor | Root canker in stone fruit caused by fungus Peniophora sacrata[END_REF], hence potentially explaining the reduced budburst of seedlings with proximity of a conspecific adult.

However, we note that the result disappears after accounting for microenvironmental conditions.

Microenvironment overlays (rather than explains) the negative direct effect of conspecific adults, and hence counters the JC process, i.e. pressure by natural enemies: conspecific adults created a favourable microenvironment by reducing M. caerulea cover at their proximity, thus enhancing seedling budburst. M. caerulea could reduce seedling physiological performance because it is an efficient competitor of tree seedlings [START_REF] Balandier | Designing forest vegetation management strategies based on the mechanisms and dynamics of crop tree competition by neighbouring vegetation[END_REF] by developing a dense root system and forming very dense tufts [START_REF] Taylor | Molinia caerulea (L.) Moench[END_REF]. Conspecific adults might hence both exert JC effects and mask them by creating a favourable microenvironment that counters the direct negative effect of the conspecific adult, potentially explaining why the JC pattern has not always been detected.

Consistent with a phylogenetic JC pattern [START_REF] Liu | Experimental evidence for a phylogenetic Janzen-Connell effect in a subtropical forest[END_REF], seedling mortality was increased by closely related adults (or decreased by distantly related adults), but this effect remains weak (Table 1). This relationship is consistent with other studies showing an increased survival of seedlings close to distantly related neighbours [START_REF] Paine | Phylogenetic density dependence and microenvironmental filtering predict seedling mortality in a tropical forest[END_REF][START_REF] Webb | Phylodiversity-dependent seedling mortality, size structure, and disease in a Bornean rain forest[END_REF]. Whilst we did not find evolutionary close relatives to increase leaf herbivory, there might be an increased pressure by soil pathogens [START_REF] Liu | Experimental evidence for a phylogenetic Janzen-Connell effect in a subtropical forest[END_REF]: closely related neighbours might increase the risk for the focal seedling to encounter enemies, because many enemies feed only on a set of closely related host-tree species [START_REF] Gossner | Native fauna on exotic trees: phylogenetic conservatism and geographic contingency in two lineages of phytophages on two lineages of trees[END_REF]. However, the inclusion of microenvironmental variables and others descriptors makes the negative effect of closely related adults disappear (Fig. 2), suggesting that the effect of evolutionary proximity on seedlings is weak or, again, mediated by the microenvironment or by a specific combination of con-and heterospecifics rather than an impact of close relatedness. We also note that, in the case of evolutionary proximity, we cannot distinguish between a negative effect of proximity and a positive effect of distance. Overall, a closely related adult has a weak negative effect on seedlings (or a distantly related adult a positive one), consistent with both phylogenetic JC pattern and process, but evolutionary proximity is far from being the major determinant of seedling recruitment.

JANZEN-CONNELL PATTERNS RESULT FROM NON-JANZEN-CONNELL PROCESSES

Consistent with a JC pattern, seedlings were positively affected by proximity to heterospecific adults through a lowered leaf herbivory, which reduced seedling mortality (Table 1; Fig. 2). However, the JC process would predict negative effect of proximate conspecific adults; heterospecific adults per se improving seedling recruitment is not considered in the classical JC process. Consistently with our results, some studies have shown an increased survival of seedlings with increasing heterospecific density [START_REF] Comita | Local neighbourhood and species' shade tolerance influence survival in a diverse seedling bank[END_REF][START_REF] Peters | Neighbour-regulated mortality: the influence of positive and negative density dependence on tree populations in species-rich tropical forests[END_REF] and an increased survival beneath the crown of heterospecifics compared to conspecifics [START_REF] Zywiec | Seedling survival under conspecific and heterospecific trees: the initial stages of regeneration of Sorbus aucuparia, a temperate fleshy-fruited pioneer tree[END_REF]. This JC pattern, due to beneficial effect of heterospecific adults rather than negative effect of conspecifics, is explained by enemies: we found that proximity to heterospecific adults reduce leaf herbivory (Table 1; Fig. 2). Positive effects of heterospecifics on seedlings support the species herd protection hypothesis [START_REF] Peters | Neighbour-regulated mortality: the influence of positive and negative density dependence on tree populations in species-rich tropical forests[END_REF][START_REF] Wills | A genetic herd-immunity model for the maintenance of MHC polymorphism[END_REF], which is an extension of the classical JC hypothesis. According to the herd protection hypothesis, increased heterospecific density will be beneficial for seedling survival because it reduces the risk of encountering species-specific enemies. Among others, odors from heterospecific adults might mask the odors from oak-seedlings and thereby reduce their detectability for enemies (e.g. [START_REF] Jactel | Non-host volatiles disrupt the response of the stenographer bark beetle, Ips sexdentatus (Coleoptera: Scolytidae), to pheromonebaited traps and maritime pine logs[END_REF]. Here, we go further by demonstrating that proximity to a single heterospecific is beneficial, so that each heterospecific adult acts as a refuge for seedlings. We recall that the seedling is a potential future competitor of the heterospecific adult and that adults, by providing refuges that favour heterospecifics, to some degree prepare their own competitive replacement. Moreover, we found support for a mediation of this JC pattern by the microenvironment (Fig. 2): heterospecific adults reduced leaf herbivory on proximate seedlings, partly due to a lower density of F. sylvatica seedlings. Quercus and Fagus are evolutionary related genera and thus share many enemies [START_REF] Gossner | Native fauna on exotic trees: phylogenetic conservatism and geographic contingency in two lineages of phytophages on two lineages of trees[END_REF]; a high density of F. sylvatica seedlings may hence contribute to attract enemies of oak seedlings. Overall, we detected a JC pattern due to a non-JC process, the support by heterospecific adults and this support operates via protection from enemies, partly due to a beneficial microenvironment.

SIZE OF ADULT TREES DOES NOT REINFORCE JANZEN-CONNELL PATTERNS

We found no support for stronger JC patterns with increasing size of adults (Table 1). Size per se of conspecific adult was not considered in the classical JC but was suggested to interact with distance by intensifying the JC pattern (see Packer andClay, 2000, referring to Janzen, 1970). Here, we found no effect of size per se controlling seedling recruitment (mortality, lack of budburst and leaf herbivory), independently or in interaction with distance. Larger trees do not appear to accumulate more enemies than younger ones, nor to intensify their specific microenvironmental conditions. Overall, within the ontogenetic time window we studied, the impact of a tree on proximate seedlings is not reinforced with the size of that tree.

IMPLICATIONS FOR FOREST MANAGEMENT

Oaks are a major source of quality wood, but regeneration is increasingly difficult in Europe [START_REF] Humphrey | Factors affecting the natural regeneration of Quercus in Scottish oakwoods. II. Insect defoliation of trees and seedlings[END_REF][START_REF] Thomas | Abiotic and biotic factors and their interactions as causes of oak decline in Central Europe[END_REF]. First, we demonstrated that seedling survival and processes driving seedling survival are mostly depending on neighbours other than conspecifics. In particular, heterospecifics constitute an efficient refuge for oak seedlings by reducing leaf herbivory and hence increasing their survival. In order to facilitate oak regeneration at the seedling stage, foresters may thus ensure to maintain species diversity in forest stands, as heterospecifics can directly improve seedling survival and reduce leaf herbivory. Second, we also detected a negative effect of cover by M. caerulea on seedling performance. An expansion of this grass species could be detrimental to the natural regeneration of understory species, including oak seedlings. Foresters may thus ensure to control this species by limiting its spread.

Conclusions

JC patterns were not produced by the JC process: they were the result of heterospecifics rather than conspecifics, and they were the result of both the microenvironment and enemies. In other cases, microenvironment-mediated processes partly countered the JC process. At least in our study system, heterospecifics are the most important predictor of seedling survival by exerting strong positive effects. These effects facilitate the establishment of oaks below non-oaks without hindering their establishment below oaks, hence contributing to ecological succession. Our results suggest that diversity in forests might be maintained not because proximity to conspecific is very unfavourable but because proximity to heterospecifics is particularly beneficial.

FIGURES (black-and-white print)

Fig. 1. Ten oak seedlings (grey squares) were transplanted every 0.5 m along a 5 m transect perpendicular to the stem of each focal adult oak tree. Light grey circles represent conspecific adults (i.e. oaks) and dark grey circles represent heterospecific adults. We measured the spatial distance between each seedling and the spatially closest conspecific adult (e.g. the focal adult oak for the enclosed seedling), also measuring the size of this conspecific adult; and the distance between each seedling and the spatially closest heterospecific adult (e.g. the upper heterospecific adult for the circled seedling), also measuring the size of this heterospecific adult. We also determined the evolutionary distance between each oak seedling and the spatially closest adult (e.g. the species of the upper heterospecific adult for the circled seedling).

Fig. 2 .

 2 Fig. 2. Structural equation model representing effect of neighbouring adults on seedling mortality and

Acknowledgements

We thank Valérie Gouesbet and Stéphanie Llopis from Ecolex for their help on data collection, and the Office National des Forêts for logistic support. We also thank Guillaume Bouger for the preparation of the measuring equipment. We are grateful to Jonathan S. Lefcheck for his helpful advice about piecewise SEM.


Nicolas Guillou
email: nicolas.guillou@developpement-durable.gouv.fr

Georges Chapalain
email: georges.chapalain@developpement-durable.gouv.fr

-Guillou and Chapalain -Multiphysics and Multiscale Couplings for Wave Height Modelling in Le Havre Harbour MULTIPHYSICS AND MULTISCALE COUPLINGS FOR WAVE HEIGHT MODELLING IN LE HAVRE HARBOUR

Keywords: tidal currents, Port 2000, Seine estuary, MISTRAL, COHERENS, TELEMAC, TOMAWAC, ARTEMIS New trends in simulation

A sensitivity study is performed to investigate the importance of multiphysics and multiscale couplings for modelling wave height in the outer Seine estuary (English Channel), the harbour of Le Havre and its new infrastructures Port 2000. Multiphysics coupling focuses on the effects of the tide in terms of time-varying water depths and currents on wind-generated surface-gravity waves. Simulations are based on the coupling of phase-averaged wave-propagation modules with circulation modules. This coupling is evaluated by comparing numerical results of the significant wave height with field data collected in November 2008 at two wave buoys moored in the access channel to Le Havre harbour. Predictions confirm a periodic local increase reaching 30 % of the wave height induced by current refraction. Multiscale coupling focuses on the importance of nested computational domains for predicting wave heights in the inner basin of Port 2000. A phase-resolving wave module is set up at this ultimate scale. Need of coupling this module with simulations at the scale of the outer Seine estuary is evaluated by comparing wave-agitation modellings driven by spatially-uniform and spatially-varying forcings with measurements in the inner basin. This comparison highlights the sensitivity of predictions to the directions of waves approaching the harbour entrance.

INTRODUCTION

Reliable predictions of wave conditions in coastal areas are of leading practical interest to coastal engineering applications associated with harbour/inlet maintenance and nearshore morphologic change. In the last decades, theoretical developments have refined our understanding of nearshore wave evolution focusing on the modifications of wind-generated surface-gravity waves by ambient currents [START_REF] Longuet-Higgins | Changes in the form of short gravity waves on long waves and tidal currents[END_REF][START_REF] Huang | Interactions between steady non-uniform currents and gravity waves with applications for currents measurements[END_REF][START_REF] Jonsson | Wave-current interactions[END_REF]. Modelling systems have reached a high standard integrating this multiphysics coupling. Accuracy of numerical results increased also with standard use of multiscale embedded computational domains. Whereas high performance computations allow to enrich simulations very easily, the questions of incorporating multiphysics and multiscale couplings are raised to optimize simulations.

The purpose of the present study is to investigate the importance of both couplings for modelling the wave height in the outer Seine estuary (southern central English Channel), the harbour of Le Havre and its new infrastructures Port 2000 (Fig. 1). The area of interest is characterized by strong interactions between wave and tide with (i) spring tidal range of 7 m and current amplitude of 1.5 m s -1 [START_REF] Shom | Courants de marée en Baie de Seine de Cherbourg à Fécamp[END_REF] and (ii) annual wave height over 5 m offshore [START_REF] Lesourd | Processus d'envasement d'un estuaire macrotidal : zoom temporel du siècle à l'heure; application à l'estuaire de la Seine[END_REF]. Sensitivity to multiphysics coupling focuses on the effects of the tide-induced time-varying water depths and currents on wave height in the outer Seine estuary. Multiscale coupling investigates the importance of nested computational domains for predicting wave-height agitation within Port 2000 inner basin. 1 Regional modelling is based on the coupling of phase-averaged wave-propagation modules with circulation modules at the scales of the English Channel and the North Sea, the bay of Seine and the outer Seine estuary (section 2.1.1). Local modelling consists in running a phase-resolving wave module at the scale of the harbour inner basin (section 2.2.2). Multiphysics and multiscale couplings are evaluated by comparing wave-height predictions with measurements characterized by noticeable semi-diurnal variations in the access channel to Le Havre harbour and its inner basin (sections 2.2 and 3.1). Tidal currents are found to have a significant influence on semi-diurnal wave-height variations in the access channel to Port 2000 exhibiting the importance of multiphysics coupling (section 3.2). Benefits of multiscale coupling are emphasized by the sensitivity of wave-agitation predictions to the direction of waves approaching the harbour entrance (section 3.2).

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MATERIALS AND METHODS

Models Description and Setup

Modelling relies on regional and local computations dedicated to the analysis of multiphysics and multiscale couplings, respectively. Regional simulations are performed with the two nested modelling systems: (1) MISTRAL ("Modélisation Intégrée pour la Simulation des TRAnsports Littoraux") [START_REF] Guillou | Rôles de l'hétérogénéité des sédiments de fond et des interactions houle-courant sur l'hydrodynamique et la dynamique sédimentaire en zone subtidale -application en Manche Orientale et à la pointe de la Bretagne[END_REF] in the English Channel and the North Sea and (2) TELEMAC [START_REF] Benoit | Development of a third generation shallow-water wave model with unstructured spatial meshing[END_REF][START_REF] Hervouet | Hydrodynamique des écoulements à surface libre. Modélisation numérique avec la méthode des éléments finis[END_REF] in the Bay of Seine (Fig. 1-a). Each modelling system couples circulation and phase-averaged wave-propagation modules. MISTRAL is based on the coupling of the wave propagation module SWAN (Simulating WAves Nearshore) [START_REF] Booij | A third generation wave model for coastal regions 1. Model description and validation[END_REF] with the three-dimensional (3D) circulation module COHERENS (COupled Hydrodynamical Ecological model for RegioNal and Shelf seas) [START_REF] Luyten | COHERENS: A COupled Hydrodynamical Ecological model for RegioNals and Shelf seas -Part III -Model Description (Available on CD-ROM[END_REF]. TELEMAC couples the wave propagation module TOMAWAC [START_REF] Benoit | Development of a third generation shallow-water wave model with unstructured spatial meshing[END_REF] with the bidimensional horizontal (2DH) circulation module TELEMAC 2D [START_REF] Hervouet | Hydrodynamique des écoulements à surface libre. Modélisation numérique avec la méthode des éléments finis[END_REF]. The coupling procedure is restricted to (1) the modifications of the wave fields by the time-varying water depths and currents and (2) the interaction between wave and current bottom boundary layers ignoring the generation of currents by waves. Preliminary tests showed the moderate impact of the second type of interaction on hydrodynamics computed by the circulation module. This makes it easier to investigate the effects of the first type of interaction. Further details about these two modelling systems, the numerical resolution, as well as the implementation at the regional scales are available in [START_REF] Guillou | Modeling the tide-induced modulation of wave height in the outer Seine estuary[END_REF].

The analysis of multiphysics coupling relies on two numerical configurations: (1) case A in which waves modules are run without the effects of the tide on the wave field and (2) case B in which the effects of the tide on the wave field are implemented. Differences between both simulations are quantified with the average of the absolute differences in wave height predictions.

Local Modelling

Local modelling is based on the phase-resolving wave-agitation module ARTEMIS (Agitation and Refraction with Telemac on a MildSlope) [START_REF] Aelbrecht | ARTEMIS 3.0: a finite element model for predicting wave agitation in coastal areas and harbours including dissipation[END_REF] of the modelling system TELEMAC. ARTEMIS is implemented on a domain covering the inner basin of Le Havre harbour and its access channel (Fig. 1-b). Whereas numerical developments have been achieved in incorporating tidal-current in wave-agitation computations [START_REF] Chen | On the modeling of wave-current interaction using the elliptic mild-slope wave equation[END_REF], the present modelling ignored theses effects, focusing on the modulation induced by penetration of tide-influenced waves within the harbour basin. Time-varying water depths are however integrated from TELEMAC 2D numerical results. Open boundaries conditions (significant wave height, period and direction) are extracted from TOMAWAC regional predictions. Further details about ARTEMIS setup and parametrizations of coastal boundary conditions (reflection coefficients, direction of approaching waves and phase shift) within Port 2000 inner basin are available in [START_REF] Guillou | Modeling penetration of tide-influenced waves in Le Havre harbor[END_REF].

Need of multiscale coupling between ARTEMIS and TOMAWAC is evaluated by comparing predicted wave agitations driven by spatially-varying and spatially-uniform forcings. The latter configuration is equivalent to drive ARTEMIS by external measurements at a single location in the entrance channel. A series of seven positions is retained to evaluate the possibility to drive the wave-agitation module by spatially-uniform forcings. This corresponds to six points titled A to F evenly spaced along ARTEMIS open boundary and the measurement point H1 (Fig. 1-b). Time series of significant wave height, period and direction are extracted from TOMAWAC simulation in case B (with tide) at each location. Differences between observations and predictions of each configuration are quantified through the standard statistical parameters of bias (positive bias represents in this investigation underestimates by the model), average of the absolute differences and root mean square error (RMSE).

Experiment Description

Measurements used here are provided by the "Grand Port Maritime du Havre" (G.P.M.H.). Measurements were made at three wave buoys H1, H2 and H3 in the access channel to Le Havre harbour and its inner basin (Fig. 1-b). The wave buoys H1 and H2 were implemented in the access channel as part of an observational system to regulate the ship routing. The wave buoy H3 was set up to complete measurements in the inner harbour. The period analyzed here is the month of November 2008. It is characterized by (1) a maximum significant wave height of 2.8 m in November 23, 2008 at point H1 and (2) a maximum tidal range of 7 m in November 14, 2008 at the tide gauge of the harbour. Further details about the instrumentation system are available in [START_REF] Guillou | Modeling the tide-induced modulation of wave height in the outer Seine estuary[END_REF] and [START_REF] Guillou | Modeling penetration of tide-influenced waves in Le Havre harbor[END_REF].

RESULTS AND DISCUSSION

Comparison of Model Predictions with Point Measurements

TOMAWAC predicted time series of wave height are compared with measurements at points H1 and H2 (Fig. 2). The comparison is not extended to point H3 as phase-averaged modules fail in simulating wave penetration within harbour basin. When the effects of the tide are integrated (case B), the numerical results reproduce the semi-diurnal variation of the wave height. An overall agreement is thus obtained between predictions and measurements. Numerical results tend to slightly overestimate the wave height at point H2 during the storms on November 21 and 24, 2008. This tendency is however reduced at location H1 with a difference less than 12 % on November 21, 2008. Comparison of wave-agitation predictions with measurement is restricted to November 19-27, 2008 characterized by higher wave periods in order to satisfy the mesh-size constraints of the numerical resolution [START_REF] Guillou | Modeling penetration of tide-influenced waves in Le Havre harbor[END_REF] (Fig. 3). Numerical results reproduce the semi-diurnal modulation of the wave height from the entrance channel till the inner harbour. Predictions approach the evolution of the significant wave height at point H3 while underestimating measurements at the beginning of the simulation from 19 to 20 November, 2008. Whereas predicted-storm wave-height of November 23 falls in the range of observed values, it presents a 30 min-time lag compared to measurements. Nevertheless, ARTEMIS computations constitute a satisfactory numerical approach of wave-height conditions at the measurement site within the harbour basin.

Sensitivity to Multiphysics Coupling

The comparison of predictions at points H1 and H2 between cases A and B exhibits the importance of the tide in the semi-diurnal wave-height modulation near the harbour of Le Havre (Fig. 2). The wave height [START_REF] Longuet-Higgins | Changes in the form of short gravity waves on long waves and tidal currents[END_REF] increases by approximately 30 % at high tide and (2) diminishes by about 10 % at low tide in the access channel to Port 2000. Further investigations integrating separately the effects of the time-varying waterdepths and currents show that current-induced refraction is one of the main mechanism responsible for the tidal variation of the wave height in the access channel [START_REF] Guillou | Modeling the tide-induced modulation of wave height in the outer Seine estuary[END_REF]. Outer modulations of the wave height are thus associated with changes in the approaching-wave direction exposing periodically the harbour entrance to high wave conditions. This analysis is extended at the scale of the outer Seine estuary with a mapping of the areas where the wave heights are modified by the tide (Fig. 4). This mapping is based on the average of the absolute differences in wave heights between cases A and B. The spatial distribution of this criterion confirms the influence of the tide at the scale of the outer Seine estuary. Its average values is 0.12 m with maximum over 0.20 m in shallow waters and the access channels to the Seine River. Minimum values are obtained in areas of low agitation at the mouth of the Seine River.

Sensitivity to Multiscale Coupling

Weak differences are denoted in the evolution of predicted waves components at points C, D, E and F on November 19-27, 2008. It is restricted to slight variations in the time series of the approaching wave directions. Four locations are thus retained to perform the sensitivity analysis: A, B, C and H1. Table 1 compares the statistical results of the estimation of the observed wave height at location H3. Positive biases are obtained in all simulations, exhibiting the tendency of numerical predictions to slightly underestimate wave-height measurements. This tendency is associated with TOMAWAC predictions along the open boundary of ARTEMIS computational domain (Fig. 2). Best results are obtained with forcings at points C and H1. The associated average of the absolute differences and root mean square errors are similar to those obtained with spatially-varying forcings. Estimate of the bias is even better for the simulation driven by forcings at point C.

Further investigation is conducted by displaying the predicted maximum wave height in November 19-27, 2008 from simulations driven by spatially-varying forcings and spatially-uniform forcings at points C and H1 (Fig. 5). In the eastern part of the harbour basin, wave agitations obtained with spatially-uniform forcings are quite similar to initial numerical estimates with spatially-varying forcings. Significant differences are however exhibited at the western entrance. Prediction driven by forcings at point C is thus presenting a band with a width of 150 m directed towards the southern breakwater where the wave height exceeds 2.1 m. Simulation driven with forcings at point H1 results in lower maximum wave height at the western entrance with a weaker exposition of the southern breakwater than in the reference situation. Time series of waves components extracted from TOMAWAC simulations at points C and H1 vary mainly in the prediction of the approaching wave direction. Differences between Figures 5-a, b and c may result from the sensitivity of model predictions to the direction imposed along ARTEMIS open boundary. Further measurements are however required to approach the variability of the approaching-wave direction in the access channel to Le Havre harbour and the wave height in the western area of the inner basin. The present investigation underlines the difficulty to drive the agitation module by external measurements at a single location.

ARTEMIS boundary conditions

CONCLUSIONS

Nested regional and local modelling systems based on the coupling of wave propagation and circulation modules have been used to investigate the importance of multiphysics and multiscale couplings in the outer Seine estuary and the harbour of Le Havre. The main outcomes of the present study are the following.

(1) Multiphysics coupling associated with the interaction between waves and tidal currents is fundamental for an accurate estimate of the wave height in complex coastal areas. Current-induced refraction is thus one of the main mechanisms responsible for the local tidal waves height variation in the access channel to Port 2000. Changes in the incident wave directions modulate the exposure of the measurement points increasing by approximately 30 % and decreasing by approximately 10 % the wave height.

(2)

Multiscale coupling associated with the nesting of a phase-resolving wave module with a phaseaveraged wave module remains the most appropriate method to approach wave agitation within the harbour basin. Driving the wave agitation module by external measurements at a single location suffers from the sensitivity of predictions to the approaching-wave directions in the western area close to the harbour entrance.

Figure 1 :

 1 Figure 1: (a) TOMAWAC and TELEMAC 2D computational domains. (b) Close-up of the computational mesh near the harbour of Le Havre with ARTEMIS computational domain and the locations of (1) points A-F along its open boundary and (2) wave buoys H1, H2 and H3. Coordinates are indicated in meters according to the French system "Lambert I Nord".

SimHydro 2012 :

 2012 New trends in simulation, Hydroinformatics & 3D modelling, 12-14 September 2012, Sophia Antipolis -Guillou and Chapalain -Multiphysics and Multiscale Couplings for Wave Height Modelling in Le Havre Harbour

Figure 2 :

 2 Figure 2: Measured and TOMAWAC computed for cases A and B time series of the significant wave height at locations H1 and H2 in November 2008 (from [11]).

Figure 3 :

 3 Figure 3: Measured and ARTEMIS computed time series of the significant wave height at locations H1 and H3 in November 19-27, 2008 (from [14]).

Figure 4 :

 4 Figure 4: Average of the absolute differences between significant wave heights predicted from cases A and B in November 2008.

Figure 5 :

 5 Figure 5: ARTEMIS predicted maximum wave height in November 19-27, 2008 in the inner basin of Le Havre harbour from simulations driven by (a) spatially-varying forcings and spatially-uniform forcings at points (b) C and (c) H1.

  SimHydro 2012:New trends in simulation, Hydroinformatics & 3D modelling, 12-14 September 2012, Sophia Antipolis -Guillou and Chapalain -Multiphysics and Multiscale Couplings for Wave Height Modelling in Le Havre Harbour

Table 1 :

 1 Statistical results of ARTEMIS estimations of observed wave height at location H3 with various open boundary conditions.

			Bias (m)	Av. abs.	RMSE (m)
				diff. (m)
	Spatially-	Reference	0.039	0.084	0.11
	varying forcings	simulation
		Point A	0.101	0.110	0.14
	Spatially-uniform forcings	Point B Point C	0.045 0.014	0.094 0.085	0.12 0.11
		Point H1	0.034	0.087	0.11

ACKNOWLEDGEMENTS

We are particularly grateful to Ronan Schubel ("Grand Port Maritime du Havre", France) for providing us with bathymetry and wave buoys measurements in the harbour computational domain. The present study has been achieved in research projects HERMES/AZOLIM and HERMES/APORT of the Laboratory of Coastal Engineering and Environment (http://memphys-lgce.fr.ht).