平茬处理对小叶锦鸡儿灌丛邻居植物群落空间格局的影响

Effects of pruning Caragana microphylla shrubs on the spatial distribution patterns of neighbouring plant communities

近几十年来,内蒙古典型草原小叶锦鸡儿(Caragana microphylla)灌丛化现象普遍发生,严重影响了草地生产力。平茬作为灌丛化草地主要管理方式之一,已受到广泛关注;然而平茬如何影响灌丛邻居植物群落的格局动态及其下土壤理化性质变化,仍缺少相应研究。以内蒙古草原小叶锦鸡儿灌丛化草地为研究对象,进行平茬处理,并依据距离小叶锦鸡儿灌丛的远近位置(远-2.5 m,近-0.5 m)设置样方进行植物群落调查和土壤样品的采集,经分析发现:(1)平茬处理显著提高了灌丛邻居植物群落均匀度及邻居植物群落下土壤全碳、全氮含量。(2)借助零模型(Null-model)分析,得出未平茬处理条件下,距离灌丛远近两种位置群落均表现为竞争性格局;而平茬处理条件下,群落竞争性格局作用弱化,且距离灌丛2.5 m位置处群落表现为促进性格局。(3)调查群落中物种间的关系多为中性作用;仅有少数物种对表现为显著正(或负)相互作用关系,且多由群落中优势物种组成;平茬处理条件下群落中显著负相互作用关系物种对比例下降,支持群落整体竞争性格局弱化这一结论。所得结果不仅为小叶锦鸡儿灌丛平茬处理条件下邻居植物群落及土壤环境的动态变化的探讨提供了实验依据,而且对灌丛化草地的恢复具有一定的实践指导意义。

Over recent decades, the Inner Mongolia Steppe has degraded seriously owing to global climate change and extreme human activities, and the population of Caragana microphylla(a native leguminous shrub) spread quickly in the degraded regions. To relieve the pressure of shrub-encroachment and promote the restoration of degraded grasslands, several measures, such as pruning, have been carried out. However, little is known about how pruning affects the community patterns and soil physical and chemical properties. In the present study, we selected a C. microphylla-dominated grassland in Zhenglan Banner, Inner Mongolia Autonomous Region, and set up pruning and non-pruning(control) plots with a combination of sites at different distances to the shrub edge(0.5 and 2.5 m distances, named 0.5 and 2.5 m-site), as treatments to investigated the soil characteristics and spatial distribution patterns of neighbouring plant communities by Null-model. The results were as follows.(1) Soil total carbon, soil total nitrogen, and Pielou evenness index were significantly(P < 0.05) influenced by pruning treatments, but not by sites, being significantly higher under pruning treatments than those under non-pruning treatments;(2) Under non-pruning treatments, the community spatial distribution patterns were dominated by competition;however, under pruning treatments, community spatial distribution patterns showed less competition, and the 2.5 m-site under the pruning treatments was dominated by facilitation;(3) Only a few pairwise species were detected to have significant negative or positive interactions(the Standardized Effect Size was greater than 2 or less than-2), and they consisted of the dominant species of their communities. However, they still played a key role in explaining community spatial distribution patterns. The number of pairwise species that have significant negative interactions under pruning treatments was less than that under non-pruning treatments, suggesting less competition in pruning communities. The results not only provided an experimental basis for exploring variations in community spatial distribution patterns by pruning C. microphylla, but also provided practical guidance for the restoration of shrub-encroached grasslands.