放牧和围封对藏北高寒草原紫花针茅群落生物量分配及碳、氮、磷储量的影响

草地围封工程是改善退化草原生态环境和促进牧区经济可持续发展的一项重大举措。以典型高寒草原紫花针茅(Stipa purpurea)群落为研究对象,选取自由放牧、围封4年和围封8年3块样地,比较分析不同草地管理方式下群落生物量分配和碳(C)、氮(N)、磷(P)储量差异。结果表明,自由放牧、围封4年和围封8年的群落地上生物量分别为46.12、146.40和256.44 g·m-2,0-15 cm土层根系生物量分别为274.74、214.87和764.59 g·m-2,15-30 cm土层根系生物量分别为17.80、17.56和31.64 g·m-2;围封显著促进了植被群落的增长(P<0.05),其中对围封4年的优势种紫花针茅和青藏苔草(Carex moorcroftii)总生物量影响最显著(P<0.05)。围封显著提高了植物群落地上部分C、N、P储量,其中围封8年样地营养元素储量最高(P<0.05)。研究结果有助于揭示草地围封工程对藏北高寒草原紫花针茅群落物质分配的影响,为评估该区域退牧还草的生态效应提供了基础数据。

Effects of grazing and fencing on Stipa purpurea community biomass allocation and carbon,nitrogen and phosphorus pools on the northern Tibet Plateau alpine

The “grassland enclosure project” is an important measure to improve ecological and environmental quality of degradation grassland and promote economy sustainable development of pastoral area. In the present study, the Stipa purpurea community biomass allocation and carbon(C), nitrogen(N) and phosphorus (P) pools were investigated in three utilization management blocks including free grazing grassland (FG), four years enclosed grassland(F4) and eight years enclosed grassland (F8) on the northern Tibet Plateau alpine. The results showed that aboveground biomass of S. purpurea community in FG, F4 and F8 were 46.12, 146.40 and 256.44 g·m-2, respectively. Root biomasses in layer of 0-15 cm were 274.74, 214.87 and 764.59 g·m-2 and root biomasses in layer of 15-30 cm were 17.80, 17.56 and 31.64 g·m-2 for these three treatments, respectively. These results suggested that enclosure significantly increased (P<0.05) the community growth. S. purpurea and Carex moorcroftii had the highest biomass in F4 (P<0.05). Enclosure significantly increased plant C, N and P pools of S. purpurea community and F8 had the highest nutrient pools (P<0.05) among the three blocks. Our research provide basic data for revealing plant biomass and nutrient allocation response to grassland utilization management and evaluating ecological effects of “grassland enclosure project”.