A state-transition approach to understanding nonequilibrium plant community dynamics in Californian grasslands
A state-transition approach to understanding nonequilibrium plant community dynamics in Californian grasslands
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DOI：
10.1023/a:1020363603900
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发表时间：
2002-09-01
期刊：
影响因子：
1.7
通讯作者：
Bartolome, JW
中科院分区：
文献类型：
--
作者：
Jackson, RD;Bartolome, JW
使用一个空间和时间上重复的数据集，我们建立了一个加州草原的状态转换模型。我们通过允许TWINSPAN对地块级别进行分类来描绘植被状态（约10 m（2））的物种覆盖数据收集了连续3至5年的9个地点在一个实验设计，其中包括5个残留干物质（RDM）的处理水平代表的范围放牧管理处方为这一类型（0，280，560，841，1121公斤RDM.公顷（-1））。我们确定并描述了一个新的加州一年生草原亚型海岸山脉草原，这是不同于以前描述的沿海草原和山谷草原。分类和回归树（CART）分析正确分类63%的TWINSPAN创建的植被过渡状态之间的相互作用网站和每月的气候平均值作为主要驱动因素。RDM变量（放牧强度的替代品）是重要的模型改进，但只有在几个网站x年的组合和预测很少归因于放牧强度梯度。基于平衡的结论，放牧强度的操纵创建独特的社区结构是有限的，在应用程序中的几个网站。结果表明，平衡模型可能是适当的预测系统的生产力，但不是社区的组成，其中的细节需要一个非平衡的方法。非平衡状态转换模型提供了相当大的潜力，以改善发展和测试的假设植被变化和管理控制的局限性，但将需要相对较大的空间和时间复制的数据集。
Using a spatially and temporally replicated dataset, we built a state-transition model for Californian grasslands. We delineated vegetation states by allowing TWINSPAN to classify plot-level (approximate to10 m(2)) species cover data collected over 3 to 5 consecutive years on 9 sites in an experimental design that incorporated 5 residual dry matter (RDM) treatment levels representative of the range of grazing management prescriptions for this type (0, 280, 560, 841, 1121 kg RDM.ha(-1)). We identified and described a new California annual grassland subtype-Coast Range Grassland-that is distinct from the previously described Coastal Prairie and Valley Grassland. Classification and regression tree (CART) analysis correctly classified 63% of TWINSPAN-created vegetation transitions among states with interactions among site and monthly climate averages as the main driving factors. The RDM variable (a surrogate for grazing intensity) was important in model refinement, but only at a few site x year combinations and predictions were rarely attributable to the grazing intensity gradient. The equilibrium-based conclusion that grazing intensity manipulation creates distinctive community structure was restricted in application to a few sites. The results suggest that equilibrium models may be appropriate for predicting system productivity but not the community composition, details of which require a nonequilibrium approach. The nonequilibrium state-transition model offers considerable potential for improving the development and testing of hypotheses about vegetation change and the limitations of management controls, but will require relatively large spatially and temporally replicated datasets.