黄土高原油松和辽东栎林下植物β多样性差异及影响因素

Understory β diversity differences and influential factors between Pinus tabulaeformis plantation and natural Quercus wutaishanica forest on the Loess Plateau

关键词:  生境异质性, 扩散限制, 人工林, 种内聚集, 典范变异分解

Key words:  habitat heterogeneity, dispersal limitation, plantation forest, intraspecific aggregation, canonical variation partitioning

摘要:

β多样性是生态学研究的热点论题,相同的β多样性格局可能由不同的生态过程所决定。该文通过构建零假说模型和典范变异分解的方法,比较了黄土高原油松人工林(Form. Pinus tabulaeformis)和辽东栎天然林(Form. Quercus wutaishanica)林下植物群落β多样性,确定了环境过滤和扩散限制在β多样性形成过程中的相对重要性。结果表明:(1)油松人工林和辽东栎天然林的林下群落均具有相似的β多样性大小,均呈现明显的种内聚集过程。(2)环境和空间共同解释了两种林型林下物种组成的较大变化(草本层[E+S]为33%～45%; 灌木层[E+S]为21%～35%),且主要以环境解释量为主(包括纯环境变量[E | S]和空间化的环境变量[E ∩ S])。(3)油松人工林和辽东栎天然林林下群落β多样性形成的不同过程主要体现在生境异质性差异以及特定的环境因子间,例如,海拔梯度、枯落物厚度以及土壤养分(速效氮和速效钾)是引起两种林型林下物种差异的显著环境因子。综上结果认为,黄土高原的油松人工林和辽东栎天然林的群落构建均由确定性的环境过滤为主导,但两种林型的环境过滤过程并不一样,主要表现为生境异质性的差异和不同的环境限制因子。对于黄土高原区域生态环境建设,首先应该保证不同群落的生境异质性,同时不能忽视扩散限制及其与生境异质性二者交互作用对β多样性的影响。

Abstract:

Beta diversity is a hot topic in ecology, and the same patterns of β diversity may be determined by different ecological processes. Null model and canonical variation partitioning methods were used to determine the relative importance between environmental filter and dispersal limitation on community assembly between Pinus tabulaeformis plantation and natural Quercus wutaishanica forest. The results were as follows:(1)The understory communities of Pinus tabulaeformis plantation and natural Quercus wutaishanica forest had similar β diversities and similar β deviations with strong intraspecific aggregations of most species.(2)Environmental and spatial variables jointly explained the great variation of species composition of understory plant community in the two forest types(Herb layer: [E + S] was 33%-45%; Shrub layer: [E + S] was 21%-35%), and dominated by the environmental explanations(including pure environmental variables [E | S] and spatial environmental variables [E ∩ S]).(3)Although Pinus tabulaeformis plantation and natural Quercus wutaishanica forest on the Loess Plateau were both dominated by environmental filter, β diversities in both forests reflected dissimilar mechanisms of community assembly. It was mainly reflected in the differences of habitat heterogeneity and specific environmental factors between these two forests. Such as, altitude, litter depth and soil nutrients(available nitrogen and available potassium)were significant environmental factors that caused species differentiation between the two forest types. Therefore, it suggests that even if the same environmental filter process, it is necessary to compare the differences of regional environmental heterogeneity and further analyze the differences of the specific environmental factors that cause environmental filter. To restore species diversity effectively on the Loess Plateau, habitat heterogeneity is an important guarantee. At the same time, dispersal limitation caused by geographical distance should not be neglected, and special attention should be paid to interaction between dispersal limitation and habitat heterogeneity on β diversity.