东北温带森林树种和功能多样性对生态系统多功能性的影响

Effect of tree species and functional diversity on ecosystem multifunctionality in temperate forests of northeast China

生物多样性对维持多种生态系统功能和提高群落抵抗扰动能力具有重要意义。选择效应和生态位互补效应是被广泛讨论的维持生态系统功能的两种机制。然而,对于两种机制在气候变化背景下如何维持森林生态系统多功能性(EMF)的理解还不充分。该研究基于分布在中国东北寒温带和中温带天然森林的样地,以功能性状多样性(FD_(q=0))、单个和多维性状功能分散指数(FDis)代表生态位互补效应,群落加权平均性状值(CWM)代表选择效应,使用多元线性模型和偏最小二乘法路径模型(结构方程模型),探究气候变化背景下不同气候区内EMF的主要影响因子和驱动机制。主要结果有:(1)在中温带森林中,生物多样性的两种属性(树种多样性(SR)和FD_(q=0))都对EMF有显著的正效应,但FD_(q=0)比SR更重要。在寒温带森林中,没有识别到生物多样性与生态系统多功能性之间的显著关系(BEMF)。(2)中温带森林群落SR对EMF的正效应被性状差异和群落加权平均最大树高(CWM_(H_(max)))介导,选择效应和生态位互补效应两种机制同时维持EMF,选择效应略高于互补效应。CWM_(H_(max))是影响寒温带森林EMF的主要生物因素,选择效应是寒温带森林EMF的主要维持机制,SR对EMF的促进作用不显著,性状差异与EMF无关。(3)由于生物多样性的“保险效应”,中温带森林抵抗气候变化的能力更强,气候因素对SR、性状差异、CWM_(H_(max))和EMF的影响都不显著。寒温带森林对气候变化敏感,气候是影响EMF的重要非生物因素。更高的年平均气温和降水量显著改变了群落的性状组成(CWM_(H_(max))),稀释了具有高竞争力和适应力性状(例如,最大树高(_(H_(max))))的物种对生态系统功能的贡献,降低了选择效应。该研究结果强调了生物多样性对维持森林EMF的重要性,证明了选择效应和生态位互补效应都是中国东北温带森林EMF的驱动机制,并表明气候变化可能会通过改变寒温带地区森林群落性状组成(例如,CWM_(H_(max)))间接影响EMF。

Aims Biodiversity is important for maintaining multiple ecosystem functions and enhancing community resilience to disturbance.Selection effect and niche complementarity effect are two widely discussed mechanisms for maintaining ecosystem function,but the understanding of how these two mechanisms maintain forest ecosystem multifunctionality(EMF)under climate change is still limited.It is essential to deepen our understanding of these mechanisms,particularly in assessing whether there are differences in their effectiveness across different climatic zones.Methods Based on plots distributed in natural forests of middle temperate and cold temperate zones in northeastern China,we used functional trait diversity(FD_(q=0)),single and multidimensional trait functional dispersion indices(FDis)to represent the niche complementarity effect,and community weighted mean trait values(CWM)to represent the selection effect.We also explored the driving force of EMF to climate change by using multivariate linear models and partial least squares path modeling(PLS-PM;structural equation model).Important findings(1)In middle temperate forests,two attributes of biodiversity(tree species diversity(SR)and FD_(q=0))had significant positive effects on EMF,and FD_(q=0) had stronger effects than SR.In cold temperate forests,no significant relationship between biodiversity and EMF(BEMF)was found.(2)In middle temperate forest communities,the effects of SR on EMF were mediated by trait differences and community weighted mean maximum tree height(CWM_(H_(max)))value.Both selection effect and niche complementarity effect simultaneously maintained EMF in middle temperate forests,with selection effect slightly higher than complementarity effect.CWM_(H_(max)) was the main biotic factor influencing cold temperate forest EMF,and selection effect was the main driving force on EMF in these forests.SR and trait differences did not have a significant promoting effect on EMF.(3)Due to the“insurance effect”of biodiversity,middle temperate forests had a stronger resistance to climate change.Climate factors had no significant impact on SR,trait differences,CWM_(H_(max)) and EMF.However,cold temperate forests were sensitive to climate change,and climatic factors were important abiotic factors affecting EMF.Higher annual mean air temperature and precipitation significantly altered community trait composition(e.g.,CWM_(H_(max))),diluting the contribution of species with high competitiveness and fitness traits(e.g.,maximum tree height(H_(max))trait)to ecosystem functions,and reducing the strength of the selection effect.This study highlights the importance of biodiversity for maintaining forest EMF,and demonstrates that both selection effect and complementarity effect are driving forces for temperate forest EMF in northeastern China.