宁夏东部杨柴生态修复区短期水氮添加对草本植物群落的影响

Effects of short-term water and nitrogen addition on herbaceous plant community in ecological restoration area of Corethrodendron fruticosum var.mongolicum in eastern Ningxia

为研究短期水氮添加对杨柴生态修复区草本植物群落数量特征及其多样性的影响,在宁夏白芨滩国家级自然保护区杨柴生态修复区进行水氮添加试验,采用随机区组设计试验,每个区组设置4个水添加梯度(W0:未添加水分;W1:添加多年平均降水量的33%;W2:添加多年平均降水量的66%;W3:添加多年平均降水量的100%)和4个氮添加梯度(氮添加量分别为N0:未添加氮素;N1:5 g·m^(-2)·a^(-1);N2:10 g·m^(-2)·a^(-1);N3:20 g·m^(-2)·a^(-1))两两随机组合的16个水氮添加处理,共4个区组。结果表明:(1)不同水氮添加使植物群落结构发生了显著变化,与对照(W0N0)相比,草本层优势种狗尾草的重要值在中氮不施水(W0N2)、低水耦合高氮(W1N3)、中水不施氮(W2N0)、中水耦合中氮(W2N2)几种处理下达到最大值,其峰值为0.46,狗尾草集群分布明显,表明在中度水平的单一水、氮或中度水平的水氮耦合措施下群落聚集效应明显。(2)在不同水氮添加处理下,从不施氮(N0)到高氮水平(N3),草本植物群落物种丰富度、Shannon-Wiener多样性指数、Simpson优势度指数以及Pielou均匀度指数均随着氮水平的增加呈先增大后减小的趋势,且都在中水耦合低氮(W2N1)处理下有最大值。(3)氮添加对于生态修复区植物的物种丰富度、Simpson优势度指数以及Shannon-Wiener多样性指数均有显著影响(P<0.05)。综上,适量的水和氮添加更有利于生态修复区植被恢复,W2N1处理能够最好地改善杨柴生态修复区草本层植物群落物种多样性,从而有效地促进了沙漠化逆转进程。

In order to study the effects of short-term water and nitrogen addition on the quantitative characteristics and the diversity of herbaceous plant communities in ecological restoration area of Corethrodendron fruticosum var.mongolicum,a water and nitrogen addition experiment was conducted in ecological restoration area of Corethrodendron fruticosum var.mongolicum in Baijitan National Nature Reserve in Ningxia,and a random block design experiment was adopted in the present study.Sixteen coupled water and nitrogen addition treatments which were 16 pairs of random combinations of one water addition gradient and one nitrogen addition gradient from 4 water addition gradients(W0:no water added;W1:adding 33%of the annual average precipitation;W2:adding 66%of the annual average precipitation;W3:adding 100%of the annual average precipitation)and 4 nitrogen addition gradients(N0:no nitrogen added,N1:5 g N·m^(-2)·a^(-1);N2:10 g N·m^(-2)·a^(-1);N3:20 g N·m^(-2)·a^(-1))were set in each block.Four blocks in total were carried out in the present study.It was found that Water and nitrogen addition caused significant changes in plant community structure.Compared with the control(W0N0),the importance value of the dominant species of Setaria viridis in the herbaceous plant layer reached the maximum value under the treatments of moderate nitrogen without water addition(W0N2),low water coupling with high nitrogen(W1N3),moderate water without nitrogen application(W2N0)and moderate water coupling with moderate nitrogen(W2N2),and the peak value was 0.46.The aggregated distribution of Setaria viridis indicated that the community aggregation effect was obvious under the moderate level of single water or nitrogen,or the moderate level of water and nitrogen coupling measures.Under all the treatments of water and nitrogen addition,from no nitrogen application(N0)to high nitrogen level(N3),the species richness,Shannon-Wiener index,Simpson index and Pielou index of herbaceous plant community all increased first and then decreased with the increase of nitrogen level,and all of them had the maximum value under the treatment of moderate water coupling with low nitrogen(W2N1).Nitrogen addition had significant effects on plant species richness,Simpson index and Shannon-Wiener index(P<0.05).Collectively,appropriate amount of water and nitrogen addition was more conductive to vegetation restoration in ecological restoration areas.The treatment of W2N1 could best improve the species diversity of herbaceous plant community in the ecological restoration area of Corethrodendron fruticosum var.mongolicum,thus effectively promoted the process of desertification reversal.