Serrano-León Hernán, Nitschke Renate, Scherer-Lorenzen Michael, Forrester David I
Chair of Silviculture, Faculty of Environment and Natural Resources, University of Freiburg, Tennenbacherstr. 4, Freiburg im Breisgau 79106, Germany.
Geobotany, Faculty of Biology, University of Freiburg, Schänzlestraße 1, Freiburg im Breisgau 79104, Germany.
Tree Physiol. 2022 Feb 9;42(2):253-272. doi: 10.1093/treephys/tpab109.
Variability in functional traits (FT) is increasingly used to understand the mechanisms behind tree species interactions and ecosystem functioning. In order to explore how FT differ due to interactions between tree species and its influence on stand productivity and other ecological processes, we examined the effects of tree species composition on the intra-specific variability of four widely measured FT: specific leaf area, leaf nitrogen content, leaf angle and stomatal conductance response to vapor pressure deficit. This study focused on three major central European tree species: European beech (Fagus sylvatica L.), Sessile oak (Quercus petraea Liebl.) and Norway spruce (Picea abies [L.] H. Karst.). Each species was examined in monoculture and two-species mixtures in the 13-year-old tree biodiversity experiment BIOTREE-Kaltenborn. Trait distributions and linear mixed models were used to analyze the effect of species mixing, tree size and stand variables on the intra-specific FT variability. A significant effect of branch height on most traits and species indicated a vertical gradient of foliar trait frequently related to light availability. Beech and oak showed a high overall trait variability and sensitivity to species mixing and stand basal area, while the trait variability of spruce was limited. Greater shifts in trait distributions due to mixing were found in specific leaf area for oak and leaf nitrogen content for beech. Thus intra-specific variability of key leaf traits was already influenced at this young development stage by inter-specific interactions. Finally, we used the 3-PG (Physiological Processes Predicting Growth) process-based forest growth model to show that the measured intra-specific variability on single FT values could influence stand productivity, light absorption and transpiration, although the net effect depends on the considered trait and the species composition of the mixture. The results of this study will aid better understanding of the effects of inter-specific competition on intra-specific FT variability, which has implications for the parameterization of process-based forest growth models and our understanding of ecosystem functioning.
功能性状（FT）的变异性越来越多地被用于理解树种相互作用和生态系统功能背后的机制。为了探究功能性状如何因树种间相互作用及其对林分生产力和其他生态过程的影响而有所不同，我们研究了树种组成对四种广泛测量的功能性状种内变异性的影响：比叶面积、叶片氮含量、叶角以及气孔导度对蒸汽压亏缺的响应。本研究聚焦于中欧的三种主要树种：欧洲山毛榉（Fagus sylvatica L.）、无梗花栎（Quercus petraea Liebl.）和挪威云杉（Picea abies [L.] H. Karst.）。在有13年树龄的树木生物多样性实验BIOTREE - Kaltenborn中，对每个树种进行了纯林种植以及两树种混交种植的研究。利用性状分布和线性混合模型分析了物种混交、树大小和林分变量对种内功能性状变异性的影响。枝条高度对大多数性状和树种有显著影响，表明叶性状存在垂直梯度，这通常与光照可用性有关。山毛榉和栎树表现出较高的总体性状变异性以及对物种混交和林分基部面积的敏感性，而云杉的性状变异性则较为有限。混交导致的性状分布变化在栎树的比叶面积和山毛榉的叶片氮含量方面更为明显。因此，在这个早期发育阶段，关键叶性状的种内变异性就已经受到种间相互作用的影响。最后，我们使用基于过程的森林生长模型3 - PG（预测生长的生理过程）表明，单个功能性状值上测量到的种内变异性可能会影响林分生产力、光吸收和蒸腾作用，尽管净效应取决于所考虑的性状以及混交林的树种组成。本研究结果将有助于更好地理解种间竞争对种内功能性状变异性的影响，这对基于过程的森林生长模型参数化以及我们对生态系统功能的理解具有重要意义。
