去除干扰对内蒙古典型草原植物叶片功能属性的影响

以内蒙古典型草原为研究对象,选取放牧和割草、去除放牧、去除放牧和割草样地进行群落调查和叶片属性测量,比较分析各样地土壤性质、群落生产力及主要物种的比叶面积(SLA,Specific Leaf Area)、叶片干物质含量(LDMC,Leaf Dry Matter Content)、叶片氮含量(LNC,Leaf Nitrogen Concentration)在个体、功能群和群落水平对去除干扰的响应。结果表明,1)去除干扰处理在短期对土壤特性和群落生产力的影响不显著;2)多数物种在放牧和割草样地SLA较低,说明典型草原多数物种的SLA表现为放牧逃避;3)不同功能群植物叶片属性对去除干扰的响应不一致,去除放牧后,多年生杂类草的SLA和LDMC不受影响,但LNC变小;多年生禾草的SLA增加,而LDMC和LNC无显著变化。一年生植物在去除放牧和割草后,LNC显著增加。去除割草后,多年生禾草SLA减小,而多年生杂类草SLA、LNC增加,LDMC减小;4)在群落水平,放牧和割草样地由于较占优势的多年生禾草SLA较低,群落比叶面积最低,在去除放牧和割草样地,群落叶片氮含量显著增加;5)在内蒙古典型草原,LDMC能够很好地将多年生禾草和多年生杂类草区分,SLA在个体、功能群和群落水平均比LDMC敏感。

Effect of disturbance removal on leaf functional traits of plants in the Inner Mongolia steppe

Grassland is the primary vegetation type throughout the world, and covers approximately 40% of land in China, most of which has been damaged because of intensive livestock use or mowing. The management of grassland is in need of tools to diagnose the state of the vegetation, and for this reason, ecologists have begun to study plant functional traits. Among plant functional traits, specific leaf area (SLA, the ratio of leaf area to leaf dry mass), leaf dry matter content (LDMC, the ratio of leaf dry mass fresh mass) and leaf nitrogen concentration (LNC) appear to be associated with plant growth and nutrition cycles.Numerous experiments have tested the effect of grazing and mowing on grassland function and structure, few attempts focusing on grassland that have been taken out of grazing or mowing. In this study, three types of sites were selected in different management areas:the control site affected by grazing and hay harvesting, the site with no grazing, and the site lacking grazing and hay harvesting. Within each site, community characteristics were investigated in August of 2012 and 2013. The leaf traits measured included; SLA, LDMC, and LNC of 14-15 of the most dominant species in each site. Our main goals in this study were to examine:1) whether removal of the disturbance had a significant effect on soil and community productivity, 2) how plant leaf functional traits are affected by reduced disturbances at the species, functional group, and community level, and 3) the sensitivity of specific leaf area(SLA) and leaf dry matter content (LDMC) to the removal of disturbances.The results showed that the removal of a disturbance had significant effects on plant leaf traits and community structure but not on soil or community productivity. Most of species in control site had low SLA, which indicated species usually avoided grazing on the Inner Mongolia steppe. Leaf traits of species belonging to different functional groups responded differently to the removal of disturbances. There was no change in the SLA and LDMC of any perennial forbs when grazing was removed. LDMC and LNC of perennial grasses did not change in response to the removal of disturbances, while SLA of the species from these functional groups changed significantly after the disturbance removal. The LNC of annual herb increased when there was a removal of grazing and hay harvesting. At the community level, the control site had the lowest community-aggregated SLA value, which was due to a lower SLA in its dominant functional group (perennial grass), while the remove grazing and hay harvesting site had the highest overall community LNC value. In addition, it was easy to distinguish perennial grasses and forbs by the LDMC values, and SLA was more sensitive to the reduction of disturbances than the LDMC at the species, functional group, and community levels.