Community assembly and shifts in plant trait distributions across an environmental gradient in coastal California
Community assembly and shifts in plant trait distributions across an environmental gradient in coastal California
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DOI：
10.1890/07-1134.1
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发表时间：
2009-02-01
影响因子：
6.1
通讯作者：
Ackerly, David D.
中科院分区：
文献类型：
--
作者：
Cornwell, William K.;Ackerly, David D.
社区组装过程被认为是塑造社区内的功能性状值的平均值，传播和间隔。已经提出了两大类的组装过程：第一，一个栖息地过滤器，限制了可行的战略范围和第二，分区的微型网站和/或资源，导致限制共存物种的相似性。这两个过程的强度可能取决于特定地点的条件，并可能沿着非生物梯度变化。我们在44个地块中取样了环境变量和植物群落，这些地块横跨沿海加州景观的不同地形。我们对54种木本植物的14个叶、茎和根性状进行了表征，包括两个性状的详细种内数据，目的是了解在各种环境条件下性状和组装过程之间的联系，我们研究了群落内性状值的平均值、极差、方差、峰度和其他间隔度量。在这种景观中，有一个地形介导的梯度水的可用性。在这个梯度上，我们观察到小区水平的平均性状值和社区内性状值的变化都发生了强烈的变化。性状的趋势与环境的手段，主要是由于物种的营业额，种内变化发挥较小的作用。与光的垂直分区相关的性状表现出更大的范围和方差在潮湿的土壤，而单位面积的氮，这是与水的利用效率，表现出更大的传播在干燥的土壤上，我们发现强非随机模式的特征分布与预期的基础上，性状介导的社区组装。有一个显着减少的范围内的11个叶和茎功能性状值相对于一个空模型。对于特定的叶面积（SLA），我们发现一个显着的甚至间距的性状值相对于空模型。对于种子大小，我们发现一个更platykurtic分布比预期的。这些结果表明，栖息地过滤器和限制共存物种的相似性可以同时塑造当地植物群落的特征和组装的分布。
Community assembly processes are thought to shape the mean, spread, and spacing of functional trait values within communities. Two broad categories of assembly processes have been proposed: first, a habitat filter that restricts the range of viable strategies and second, a partitioning of microsites and/or resources that leads to a limit to the similarity of coexisting species. The strength of both processes may be dependent on conditions at a particular site and may change along an abiotic gradient.We sampled environmental variables and plant communities in 44 plots across the varied topography of a coastal California landscape. We characterized 14 leaf, stem, and root traits for 54 woody plant species, including detailed intraspecific data for two traits with the goal of understanding the connection between traits and assembly processes in a variety of environmental conditions.We examined the within-community mean, range, variance, kurtosis, and other measures of spacing of trait values. In this landscape, there was a topographically mediated gradient in water availability. Across this gradient we observed strong shifts in both the plot-level mean trait values and the variation in trait values within communities. Trends in trait means with the environment were due largely to species turnover, with intraspecific shifts playing a smaller role. Traits associated with a vertical partitioning of light showed a greater range and variance on the wet soils, while nitrogen per area, which is associated with water use efficiency, showed a greater spread on the dry soils.We found strong nonrandom patterns in the trait distributions consistent with expectations based on trait-mediated community assembly. There was a significant reduction in the range of six out of 11 leaf and stem functional trait values relative to a null model. For specific leaf area (SLA) we found a significant even spacing of trait values relative to the null model. For seed size we found a more platykurtic distribution than expected. These results suggest that both a habitat filter and a limit to the similarity of coexisting species can simultaneously shape the distribution of traits and the assembly of local plant communities.