Data from: Plant traits of propagule banks and standing vegetation reveal flooding alleviates impacts of agriculture on wetland restoration

1. Restoration of degraded plant communities requires understanding of community assembly processes. Human land use can influence plant community assembly by altering environmental conditions and species' dispersal patterns. Flooding, including from environmental flows, may counteract land use effects on wetland vegetation. We examined the influence of land use history and flood frequency on the functional composition of wetland plant communities along a regulated river. 2. We applied fourth corner modelling to determine species' trait-based responses to flooding and land use by combining data on i) the occupancy and abundance of species in propagule banks and standing vegetation, ii) species traits, and iii) environmental conditions of 22 standing vegetation and 108 soil propagule bank study sites. We used analysis of deviance to test how well each dataset characterised trait–environment interactions, and generalised linear models to identify traits related to species' responses. 3. The occupancy and abundance of native species in the propagule bank and standing vegetation increased with flood frequency and decreased with duration of agricultural land use. Species in standing vegetation with water-borne propagule dispersal (hydrochory) showed similar trends. In contrast, species with higher specific leaf area were associated with longer land use duration. 4. Identifying trait–based differences in the propagule bank and standing vegetation can help disentangle effects of dispersal and environmental filters. The occupancy and abundance of hydrochorous species in standing vegetation were negatively related to land use duration, but hydrochorous species were positively related to land use duration based on their abundance in the propagule bank. This suggests that land use does not limit plant dispersal, but acts as an in situ abiotic filter limiting species presence in standing vegetation. 5. Synthesis and applications. Land use duration and flood frequency have opposite effects on plant community traits in floodplain wetlands of the Macquarie Marshes, Australia. Legacies of agriculture can impede restoration of plant communities. Environmental flows that increase flooding may alleviate these impacts, especially in areas that have been used for agriculture for over 20 years, by providing dispersal and environmental filters that favour native wetland species. More flooding will likely be required to restore floodplains with longer histories of agricultural land use compared to floodplains less impacted by agriculture.04-Apr-2017

1. 退化植物群落的恢复需明确群落构建过程（community assembly processes）。人类土地利用可通过改变环境条件与物种扩散模式，对植物群落构建产生影响。包括环境流量（environmental flows）引发的洪水在内的淹水事件，或可抵消土地利用对湿地植被的负面影响。本研究针对一条受调控河流沿岸的湿地植物群落，探讨了土地利用历史与洪水频次对其功能组成（functional composition）的影响。
2. 我们采用四角落模型（fourth corner modelling），结合三类数据集开展分析：① 繁殖体库（propagule bank）与现存植被（standing vegetation）中物种的占据度与多度数据，② 物种功能性状数据，③ 22个现存植被样地与108个土壤繁殖体库样地的环境条件数据。通过偏差分析（analysis of deviance）评估各数据集对性状-环境互作的表征效果，并借助广义线性模型（generalised linear models）筛选与物种响应相关的功能性状。
3. 繁殖体库与现存植被中的本土物种占据度与多度随洪水频次升高而增加，随农业土地利用时长增加而降低。现存植被中具有水媒传播（hydrochory）繁殖体的物种也呈现出相似趋势。与之相反，比叶面积（specific leaf area）更高的物种则与更长的土地利用时长显著相关。
4. 明确繁殖体库与现存植被间基于性状的差异，有助于厘清扩散过滤（dispersal filters）与环境过滤（environmental filters）的作用机制。现存植被中水媒传播物种的占据度与多度与土地利用时长呈负相关，但基于繁殖体库多度的水媒传播物种则与土地利用时长呈正相关。这表明土地利用并未限制植物扩散，而是作为一种原位非生物过滤因子（in situ abiotic filter），阻碍了本土物种在现存植被中的定植与存续。
5. 综合与应用。澳大利亚麦夸里沼泽（Macquarie Marshes）泛滥平原湿地中，土地利用时长与洪水频次对植物群落功能性状的影响恰好相反。农业活动遗留效应会阻碍植物群落的恢复。通过提升洪水频次的环境流量，可为本土湿地物种提供适宜的扩散与环境过滤条件，从而缓解这些负面影响，尤其适用于已有20年以上农业利用历史的区域。相较于受农业影响较轻的泛滥平原，恢复农业利用历史更长的泛滥平原植被，需要更为频繁的洪水干预。
2017年4月4日