Multiple abiotic and biotic drivers of aboveground biomass shift with forest stratum
Multiple abiotic and biotic drivers of aboveground biomass shift with forest stratum
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地上生物量随森林地层变化的多种非生物和生物驱动因素
DOI：
10.1016/j.foreco.2019.01.007
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发表时间：
2019-03-15
影响因子：
3.7
通讯作者：
Yan, En-Rong
中科院分区：
文献类型：
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作者：
Ali, Arshad;Chen, Han Y. H.;Yan, En-Rong
深入了解森林各层(即上层和下层)多样性-生物量关系的基本生态机制，对于理解垂直分层对天然林生态系统功能的重要性至关重要。然而，目前尚不清楚多种非生物(即土壤养分)和生物(即生物多样性、功能特性和林分结构复杂性)因素如何同时决定每一个体林层和整个群落的地上生物量。为了解决这一认识差距，我们分离了土壤养分(土壤肥力假说)、分类学、功能性状和进化多样性(生态位互补假说)、林分结构复杂性(基于树木大小的生态位分化假说)和群落加权平均性状值(质量比假说)对跨森林层级和整个群落的地上生物量的相对影响。利用中国东部125个亚热带森林样地的森林资源清查、功能性状和环境因子数据。用多元线性回归模型选择每个生物类群内的最佳预测因子，并用结构方程模型来评估多个非生物和生物驱动因素如何决定地上生物量。在富营养化土壤上，地上生物量与树高(即功能优势度)和林分密度的群落加权平均值呈正相关，与功能均匀度呈负相关。在林下植被中，地上生物量与系统发育物种丰富度和林分平均直径呈正相关，而与贫瘠土壤物种多样性呈负相关。林下生物量还受林分结构和功能优势度的影响，通过林下生物驱动的直接和间接作用决定。这些结果表明，功能优势度和林分结构复杂性是地上生物量的主要生物驱动因素。而林下植被的功能优势和林分结构的复杂性、土壤养分以及林下物种间生态位的互补性决定了林下地上生物量。整个群落的地上生物量可能是由于上层功能优势的优势作用而产生的。这项研究强调生态位互补性、质量比和土壤养分效应对驱动地上生物量是重要的，但以不同的方式跨越天然亚热带森林的上层和下层。我们认为，生物多样性丧失对地上生物量的相对影响取决于特定林层中丧失物种的功能和进化同一性。通过在复杂的天然林中分别考虑上层和下层，可以更好地了解森林管理和生物多样性保护。
Insights into the underlying ecological mechanisms for diversity-biomass relationships across forest strata (i.e., overstorey and understorey) are crucial to understand the importance of vertical stratification on ecosystem function in natural forests. Yet, it remains unclear how multiple abiotic (i.e., soil nutrients) and biotic (i.e., biodiversity, functional identity and stand structural complexity) factors simultaneously determine aboveground biomass in each individual forest stratum and whole-community. To address this knowledge gap, we disentangled the relative effects of soil nutrients (soil fertility hypothesis), taxonomic, functional trait and evolutionary diversity (niche complementarity hypothesis), stand structural complexity (niche differentiation hypothesis based on tree sizes), and community-weighted mean trait values (mass ratio hypothesis) on aboveground biomass across forest strata and whole-community. We used forest inventory, functional traits and environmental factors datasets from 125 subtropical forest plots in Eastern China. Multiple linear regression models were performed for the selection of best predictors within each biotic group, and structural equation modelling was used to evaluating how multiple abiotic and biotic drivers determine aboveground biomass. In the overstorey, aboveground biomass was positively related to the community-weighted mean of tree height (i.e., functional dominance) and stand density but was negatively related to functional evenness on nutrient-rich soils. In the understorey, aboveground biomass was positively related to phylogenetic species richness and stand-level tree mean diameter (i.e., a proxy for forest growth) but was negatively related to Shannon's species diversity on nutrient-poor soils. Understorey aboveground biomass was also determined by overstorey stand structure and functional dominance through direct and indirect effects via understorey biotic drivers. These results suggest that functional dominance and stand structural complexity are the main biotic drivers of overstorey aboveground biomass. Whereas, functional dominance and stand structural complexity of overstorey, soil nutrients, and niche complementarity among understorey species with the conservative strategy determine understorey aboveground biomass. Whole-community aboveground biomass might be resulting from the superior role of overstorey functional dominance. This study highlights that the niche complementarity, mass ratio and soil nutrients effects are important for driving aboveground biomass, but in different ways across overstorey and understorey strata in natural subtropical forests. We argue that the relative effect of biodiversity loss on aboveground biomass depends critically on the functional and evolutionary identity of the lost species in the specific forest stratum. Better insights can be gained into forest management and biodiversity conservation by considering overstorey and understorey strata separately in complex natural forests.