黄土高原退耕还草地C、N、P生态化学计量特征对植物多样性的影响

为探讨退耕还草地生态化学计量特征随恢复年限的变化以及其对植物多样性的影响，选取黄土高原不同恢复年限退耕还草地为研究对象，分别为农田（对照）、恢复8 a、15 a、25 a和35 a，测定了植物地上部分和土壤C、N、P含量，并分析了其C：N：P化学计量特征与植物多样性之间的关系。结果表明：（1）总体上，随着恢复年限的增加，植物地上部分C、N、P含量呈现增长趋势，而其C：N、C：P以及N：P呈现降低趋势，其中C含量在恢复35 a时达到最大值（434.95 g/kg）；N含量在农田阶段最高（2.29 g/kg），P含量在恢复25 a时达到最高（1.23 g/kg）。（2）土壤C、N、P含量及N：P随恢复年限的增加总体上呈现增加趋势，C：N呈现降低趋势，而C：P基本保持不变；土壤C、N、P含量的最大值均出现在恢复35 a，其值分别为10.94 g/kg、0.07 g/kg、0.06 g/kg。（3）随着植物地上部分C含量和C：N的增加，Shannon-Weiner指数降低；植物地上部分C含量和土壤P含量是影响Simpson指数的主要因子，其与植物地上部分C含量负相关，而与土壤P含量显著正相关；Pielou均匀度指数与土壤N含量、N：P、C：P以及植物地上部分C含量等因子正相关；Margalef指数与植物地上部分N含量、P含量等因子正相关。研究表明草地恢复中植物和土壤C：N：P化学计量特征对植物多样性具有重要的影响。

Effects of carbon, nitrogen, and phosphorus ecological stoichiometry characteristics on plant diversity since returning farmland to grassland on the Loess Plateau

In order to study the change of the ecological stoichiometric characteristics since returning farmland to grassland with restoration years and its influence on plant diversity, this study examined the changes in the C, N, P stoichiometry characteristics of aboveground part of plant and soil, and explored the relationships between them and the plant diversity with a chronosequence of 8, 15, 25, and 35 years since returing farmland to grassland (farmland as the control) on the Loess Plateau. The results showed that: (1) overall, the content of C, N and P in the aboveground part of plants all increased with the increase of the recovery years, while the C:N, C:P and N:P decreased. The content of plant C reached the maximum value (434.95 g/kg) at 35 years of grassland restoration, the content of plant N reached the maximum value (2.29 g/kg) at the farmland stage, and the content of plant P reached the maximum value (1.23 g/kg) after 25 years of grassland restoration. (2) The content of C, N and P in the soil and N:P showed an increasing trend with the increase of recovery years, while C:N showed a trend of decreasing and C:P remained unchanged basically; all of the maximum values of C, N, P contents appeared in the 35 years, the values are 10.94 g/kg, 0.07 g/kg and 0.06 g/kg, respectively. (3) Shannon Weiner index decreased with the increase of C content and C:N in the aboveground part of plants; the content of C in the aboveground part of plants and soil P are the main factors affecting Simpson index, which showed a negative correlation with C in the aboveground part of plants and a positive correlation with the P content in the soil; Pielou index was positively correlated with the soil N content, N:P, C:P and the C content of the aboveground part of plants; Margalef index was positively correlated with the N and P contents of the aboveground part of plants. The results showed that the C, N, P stoichiometric characteristics of plants and soil had important effect on plant diversity in the grassland restoration.