Long-term studies of secondary succession and community assembly in the prairie-forest ecotone of eastern Kansas, Hay meadow restoration experiment

Local and regional-scale processes interact to govern the assembly, diversity and
functioning of ecological communities. Evaluating the interplay of these differently-scaled
processes in the regulation of ecological systems is a challenging problem, but is crucial
towards understanding and predicting the potential effects of accelerated human activity on
biological diversity and ecosystem sustainability. Since 2000, two long-term field
experiments have been underway in grasslands of eastern Kansas to investigate the interplay
of soil resource availability, species interactions and regional processes governing plant
secondary succession, community assembly, biodiversity, and ecosystem functioning. Both
experiments involve manipulations of soil nutrients in permanent grassland study plots and
employ multi-species seed addition treatments to evaluate the contribution of dispersal
limitation and regional constraints on local species pools to the regulation of plant
community dynamics. Hay meadow restoration experiment, previously funded by USDA, was established in 2000
in a section of the field that was left unplowed at the start of the experiment. Thus
Experiment 2 was initiated in the context of secondary succession on recently abandoned
cool-season hayfield where hay grass species were dominant at the start of the study. In
this experiment we have been monitoring plant community change annually since 2001 in
response to two aspects of hay management important in our area: annual fertilization and
annual haying. The experimental design involves factorial manipulations of nutrient supply
(two levels of NPK fertilization), annual haying (two levels: hayed; not hayed) and
propagule input achieved by adding seeds of 41 native prairie species to half of the plots.
Experiment 2 parallels Experiment 1 with manipulations of soil resources and species pools,
but does so in the contexts of hay management and native prairie hay meadow restoration.

局域与区域尺度的生态过程相互作用，共同调控生物群落的组装、物种多样性与生态系统功能。解析这类不同尺度生态过程在生态系统调控中的协同效应，是一项兼具挑战性与重要性的研究课题——其结果对于理解、预测人类活动加剧对生物多样性与生态系统可持续性的潜在影响至关重要。自2000年起，美国堪萨斯州东部的草原区域已启动两项长期野外实验，旨在探究土壤资源可获得性、物种间相互作用，以及调控植物次生演替、群落组装、生物多样性与生态系统功能的区域过程之间的相互关系。两项实验均通过在永久性草原样地中操控土壤养分条件，并采用多物种种子添加处理，以解析扩散限制与区域物种库约束对植物群落动态调控的贡献。
此前由美国农业部（United States Department of Agriculture, USDA）资助的干草甸恢复实验，于2000年在实验初始阶段未被翻耕的地块区域启动。因此，实验2依托于近期弃耕的冷季型干草场开展次生演替研究——该研究初始阶段以禾本科牧草为优势物种。本实验自2001年起每年监测植物群落动态变化，以探究当地两项核心干草管理措施的影响：年度施肥与年度刈割。实验设计采用析因操控方案：养分供给（设置2个NPK施肥水平）、年度刈割（设置2个水平：刈割组与未刈割组），以及通过向半数样地添加41种本土草原物种种子实现的繁殖体输入操控。实验2与实验1的核心操控内容一致，均针对土壤资源与物种库开展操控，但实验2的研究背景为干草管理与本土草原干草甸恢复场景。