半干旱草地不同植物枯落物分解对放牧和封育的响应

Abstract

为探究放牧和封育对半干旱草地植物枯落物分解的影响，选取赖草、牛枝子及其混合物为研究对象，调查了不同网孔分解袋中宁夏半干旱草地植物枯落物分解特征及对放牧和封育的响应规律。结果表明：（1）放牧样地250目网孔中，枯落物质量残留率表现为牛枝子显著高于赖草和混合物（P<0.05），而在放牧样地30目网孔、封育样地2种网孔中，枯落物质量残留率均表现为3种枯落物间无显著差异。（2）250目网孔中，放牧和封育样地枯落物分解衰减常数均表现为混合物显著高于牛枝子，而赖草居中；并且，牛枝子枯落物分解衰减常数表现为封育样地显著高于放牧样地。30目网孔中，放牧和封育样地枯落物分解衰减常数均表现为赖草、混合物显著高于牛枝子（P<0.05）；并且，牛枝子枯落物分解衰减常数表现为封育样地显著高于放牧样地（P<0.05）。（3）在放牧样地，仅牛枝子枯落物R_m表现为30目显著低于250目网孔（P<0.05），k表现为30目显著高于250目网孔（P<0.05）；土壤动物对枯落物分解的贡献率表现为混合物显著低于牛枝子，赖草居中（P<0.05）。而在封育样地，仅牛枝子枯落物k表现为30目显著高于250目网孔（P<0.05）；土壤动物对枯落物分解的贡献率表现为混合物和牛枝子均显著高于赖草，且混合枯落物的土壤动物贡献率表现为封育样地显著高于放牧样地（P<0.05）。（4）枯落物残留率与其初始N、P、木质素/N、C/P呈显著相关性（P<0.05）；枯落物分解衰减常数与其初始N、P、木质素、N/P、C/P和木质素/P间均呈显著相关性（P<0.05）。研究表明，植物种类组成显著影响枯落物的残留率和分解衰减常数。放牧与封育管理通过影响网孔中土壤动物分布来调控半干旱区草地植物枯落物的分解，而且封育管理更有利于促进土壤动物对低质量枯落物（牛枝子）的分解。;This present study was to explored litter decomposition of different plant species under grazing and enclosure management in semi-arid grassland ecosystems. The remaining mass and decay constant (k) of Leymus secalinus, Lespedeza potaninii litter, and their mixture were investigated within 30-and 250-mesh litterbags in semiarid grasslands under grazing and enclosure management in Ningxia. In addition, the contribution of litter arthropods to decomposition was analyzed in order to discuss the effects of grazing management on decomposition process. The results showed that:(1) there was a significant higher final litter mass remaining rate (R_m) in L. potaninii than in L. secalinus and mixture from 250-mesh litterbags in grazing grasslands, whereas there were no significant differences in R_m of plant litter either from 30-mesh litterbags in grazing grasslands, or from both size-mesh treatments in enclosure grasslands. (2) In 250-mesh litterbags, the k was significantly higher in the mixture than in L. potaninii in both grasslands under grazing and enclosure managements, with the intermediate values in L. secalinus litter (P<0.05). But the k of L. potaninii was significantly higher in enclosure than in grazing grasslands (P<0.05). In 30-mesh litterbags, the litter decay constant (k) was significantly higher in L. secalinus and mixture than in L. potaninii in both grasslands under grazing and enclosure managements; the k of L. potaninii litter was significantly higher in enclosure than in grazing grasslands (P<0.05). (3) In grazing grassland, the R_m of L. potaninii was significantly higher in 250-mesh than 30-mesh (P<0.05), while k was significantly higher in 30-mesh than in 250-mesh. There were significantly lower values in the mixture than in L. potaninii, with the intermediate values in L. secalinus (P<0.05). In enclosure grassland, the k of L. potaninii was significantly higher in 30-mesh than 250-mesh (P<0.05), while the contribution rate of litter arthropods to litter decomposition was significant higher in the mixture and L. potaninii than in L. secalinus. The contribution rate of litter arthropods to mixture litter decomposition was significantly higher in enclosure than in grazing grasslands (P<0.05). (4) The R_m indicated a positive correlation with litter lignin/N and litter C/P, but it indicated a negatively correlation with litter initial N and P content. And the k indicated a positive correlation with litter initial N and P, while it indicated a negatively correlation with litter lignin, N/P, C/P and lignin/P. It was suggested that plant species composition presented a significant effect on the litter final mass remaining and decay constant. The effect of grazing management on litter arthropod distribution between different mesh-size litterbags induced the decomposition differences between various species of plant litter. In conclusion, the enclosure management was conducive to promoting the contribution of litter arthropods to low-quality litter (i.e., L. potaninii) decomposition in semi-arid grasslands.