Mortality of silver fir and Norway Spruce in the Western Alps — a semi-parametric approach combining size-dependent and growth-dependent mortality

Abstract

Abstract• Question: Tree mortality can be modeled using two complementary covariates, tree size and tree growth. Tree growth is an integrative measure of tree vitality while tree diameter is a good index of sensitivity to disturbances and can be considered as a proxy for tree age which may indicate senescence. Few mortality models integrate both covariates because classical model calibration requires large permanent plot data-sets which are rare. How then can we calibrate a multivariate mortality model including size and growth when permanent plots data are not available?• Location: To answer this question, we studied Abies alba and Picea abies mortality in the French Swiss and Italian Alps.• Method: Our study proposes an alternative semi-parametric method which includes a random sample of living and dead trees with diameter and growth measurements.• Results: We were able to calibrate a mortality model combining both size-dependent and growthdependent mortality. We demonstrated that A. alba had a lower annual mortality rate (10%) than P. abies (18%) for low growth (< 0.2 mm year −1 ). We also demonstrated that for higher diameters (DBH ≥ 70 cm), P. abies had a higher mortality rate (0.45%) than A. alba (0.32%).• Conclusion: Our results are consistent with the mechanisms of colonization-competition trade-off and of successional niche theory which may explain the coexistence of these two species in the Alps. The method we developed should be useful for forecasting tree mortality and can improve the efficiency of forest dynamics models. Mots-clés :Abies alba / probabilités conditionnelles / modèles non-paramétriques / Picea abies / mortalité des arbres Résumé -Mortalité du sapin pectiné et de l'épicea commmun dans les alpes occidentales -une approche semi-paramétrique combinant la mortalité dépendant de la taille et de la croissance.• Question : Il est possible de modéliser la mortalité des arbres en utilisant deux covariables complé-mentaires : la taille et la croissance de l'arbre. La croissance est une mesure synthétique de la vitalité alors que le diamètre est un bon indicateur de la sensibilité aux perturbations et est très fortement corrélé à l'âge de l'arbre, qui détermine la sénescence. Peu de modèles de mortalité intègrent les deux covariables, car cela nécessite, pour les approches classiques, une calibration à partir de données de placettes permanentes qui sont rares. Comment obtenir un modèle de mortalité multivarié, incluant la taille et la croissance, lorsque des données de placettes permanentes ne sont pas disponibles ?• Localisation géographique : Pour répondre à cette question, nous avons étudié la mortalité du sapin pectiné (Abies alba) et de l'epicéa commmun (Picea abies) dans les Alpes suisses françaises et italiennes.• Méthode : Notre étude propose une méthode semi-parametrique alternative s'appuyant sur un échantillon d'arbres morts et vivants avec des mesures de diamètre et de croissance.• Résultats : Nous avons obtenu un modèle combinant la mortalité dépendant à la fois de la taille et de la...

Using the Viability Theory to Assess the Flexibility of Forest Managers Under Ecological Intensification

“…As we assume that the limiting basal area for growth is 60 m 2 , we assume that this state also induces a 5 % yearly mortality, which is compatible with previous observations in mountain forests (Vieilledent et al 2010a), and thus gives us z = 5 %/60 = 0.008; and • the potential growth parameter b is set (by simple calibration method) to 0.75 in order to obtain a reasonable forest structure as observed in the Vercors (Redon et al (2014) and unpublished data): for a mean removal of 6 m 3 year -1 ha -1 , we have about a 25 m 2 basal area in stratum 1 and a 5 m 2 basal area in stratum 2.…”

“…Green [80 %. Where there is no color, the states are not viable, which puts local flexibility at 0 ðd 1 ; h 1 ; m 1 Þ 0.16 (0.45,25,2.29)(Vieilledent et al 2010a) and(Vallet et al 2006) for computations of m 1 and m 2 g 2 ðd 2 ; h 2 ;…”

Growth patterns and sensitivity to climate predict silver fir decline in the Spanish Pyrenees

“…Our findings underscore that tree decline is driven by the individual growth sensitivity. Such intra-specific variability may have deep consequences for tree growth and survival leading to the selective mortality of the most sensitive trees (Clark 2003) as has been evidenced in silver fir (Vieilledent et al 2010;Rathgeber et al 2011). Future studies on forest decline should deal with the consideration and quantification of intra-specific variability at the tree level considering both local and regional scales.…”

“…Radial growth, used here as a proxy of whole plant carbon gain (Litton et al 2007), may be used to identify those trees with the highest probabilities of severe defoliation, decline and death (Wunder et al 2008;Vieilledent et al 2010;Carnicer et al 2011). Several studies have shown that tree defoliation, mean radial growth and radial growth trends are, to some extent, inversely related (Buchman et al 1983;Kobe and Coates 1997;Wyckoff and Clark 2000;van Mantgem et al 2003).…”

Weak competitive ability may explain decline of Taxus baccata

“…Similarly, strong competitive abilities of A. alba were found in the western Alps. Silver fir was more resistant to low growth and had lower mortality in comparison with Picea abies (Vieilledent et al 2010). However, the decline of Abies alba in natural ecosystems is more often observed (Thomas et al 2002;Camarero et al 2011;Ficko et al 2011;Klopcic and Boncina 2011).…”