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| 返青期休牧对高寒草地植物群落和土壤特征的研究
摘 要
青藏高原高寒草地作为我国重要的草地生态系统与放牧生态系统，在环境保护和创造经济价值方面发挥着重要的作用，由于人口增长引起的放牧家畜数量的快速增加导致放牧对草地的危害进一步扩大以致草地退化等问题出现。为探究休牧对川西北高寒草地植物群落和土壤理化性质的影响，为退化草地探索有效的恢复措施，本研究在青藏高原东南缘四川省阿坝州红原县典型高寒草地设置了3个不同放牧处理(对照：全年休牧；传统放牧：5月底-9月底放牧，放牧强度为3头牦牛/公顷；返青期休牧：6月底-9月底放牧，放牧强度为3头牦牛/公顷)。研究内容有：植物群落总盖度与各科植物的分盖度、群落的总生物量与各科植物的生物量以及地下生物量、生物多样性以及土壤的物理和化学指标在0-10、10-20、20-30cm土层的变化情况。研究得出以下结果：
草地在休牧后，植被得以休养生息的机会，显著提高了群落的总盖度与禾本科的分盖度(P<0.05)，对莎草科、豆科、菊科以及其他杂类草植物的盖度无显著性影响(P>0.05)。
全年休牧显著提高了群落的总生物量以及禾本科植物与杂类草植物的生物量(P<0.05)；而返青期休牧与传统放牧显著降低了杂类草的生物量(P<0.05)，对莎草科与菊科的生物量无显著性影响(P>0.05)；地下生物量对休牧无显著性响应(P>0.05)。
返青期休牧对shannon-wiener多样性指数和Pielou均匀度指数无显著性差异(P>0.05)，但显著增加了物种数(P<0.05)。
休牧对土壤含水率无显著性影响(P>0.05)，对0-10、10-20cm土层的土壤容重无显著性影响(P>0.05)，而在20-30cm土层返青期休牧显著降低的土壤容重(P<0.05)。
全年休牧与返青期休牧对0-10、10-20cm土层的有机质与有机碳无显著性影响(P>0.05)，显著提高了20-30cm土层的有机质与有机碳含量(P<0.05)。不同放牧处理对0-10、10-20cm土层的pH值无显著性影响，而传统放牧土壤pH值显著高于全年休牧(P<0.05)。全年休牧与返青期休牧提高了0-10、10-20cm的全氮含量(P>0.05)，在20-30cm土层达到显著水平(P<0.05)；休牧对土壤全磷含量无显著性影响(P>0.05)；全年休牧极显著提高了土壤全钾含量(P<0.01)。返青期休牧样地的有效氮含量在0-10cm土层极显著高于全年休牧样地(P<0.01)，显著高于传统放牧样地P<0.05)，10-20cm土层返青期休牧样地显著高于全年休牧样地(P<0.05)，20-30cm土层返青期休牧样地显著高于传统放牧(P<0.05)。有效磷含量在三个土层都是返青期休牧样地极显著高于全年休牧样地(P<0.01)，0-10、10-20cm土层传统放牧样地显著高于全年休牧样地(P<0.05)，20-30cm土层传统放牧样地与全年休牧样地无显著差异(P>0.05)。土壤速效钾含量在返青期休牧样地极显著高于全年休牧样地(P<0.01)，0-10、20-30cm土层返青期休牧样地极显著高于传统放牧样地(P<0.01)，全年休牧与传统放牧差异不显著(P>0.05)。土壤C/N、C/P、N/P在0-10、10-20cm土层无显著性差异(P>0.05)。20-30cm土层C/N在传统放牧样地显著高于返青期休牧样地(P<0.05)，C/P、N/P在休牧样地显著高于传统放牧样地(P<0.05)。
关键词：休牧；放牧；植物群落；土壤理化性质
Abstract
As an important grassland ecosystem and grazing ecosystem in my country, the alpine grassland on the Qinghai-Tibet Plateau plays an important role in environmental protection and creating economic value. The rapid increase in the number of grazing livestock caused by population growth has led to further expansion of the damage to the grassland by grazing. Problems such as grassland degradation have emerged.In order to explore the effects of rest grazing on the plant community and soilphysical and chemical properties of the alpine grassland in northwestern Sichuan, and to explore effective restoration measures for degraded grasslands,this study set up three different typical alpine grassland in Hongyuan County, Aba Prefecture, Sichuan Province on the southeastern edge of the Qinghai-Tibet Plateau. Grazing treatment (control: year-round no grazing;traditional grazing: grazing from the end of May to September, the grazing intensity is 3 yaks/ha; returning to the green period: grazing from the end of June to the end of September, the grazing intensity is 3 yaks/ha).The research contents include: total coverage of plant communities and sub-coverages of plants of various families,total biomass of communitiesand biomass of plants of various families, and underground biomass of plant communities, biodiversity, and the changes of soil physical and chemical indicators in the 0-10, 10-20, 20-30cm soil layer. The study has the following results:
After the grassland is closed for grazing,the vegetation has the opportunity to cultivate and live, which significantly improves the total coverage of the community and the sub-coverage of the Poaceae (P<0.05).There was no significant effect on the coverage of Cyperaceae, Fabaceae, Asteraceae and Others (P>0.05).
The annual rest grazing significantly increased the total biomass of the community and the biomass of Poaceae and Others (P<0.05); while rest grazing and traditional grazing significantly reduced the biomass of Others (P<0.05), no significant effect on the biomass of Cyperaceae and Asteraceae(P>0.05); underground biomass has no significant response to no grazing (P>0.05).
There was no significant difference between the shannon-wiener diversity index and the Pielou evenness index during the whole year's rest grazing (P>0.05), while the rest grazing during the returning period significantly increased the number of species (P<0.05).
Rest grazing has no significant effect on the soil moisture content (P>0.05), and has no significant effect on the soil bulk density of the 0-10, 10-20cm soil layer (P>0.05), while in the 20-30cm soil layer the soil bulk density was significantly reduced during rest grazing during the returning period (P<0.05).
The whole year's rest grazing and the rest grazing during the returning period have no significant effect on the organic matter and organic carbon in the 0-10, 10-20cm soil layer (P>0.05), and significantly increased the organic matter andorganic carbon content in the 20-30cm soil layer (P<0.05).Different grazing treatments had no significant effect on the pH value of 0-10 and 10-20cm soil layers,while the pH value of traditional grazing soil was significantly higher than the annual rest grazing (P<0.05).The whole year's rest grazing and the rest grazing during the returningperiod increased the total nitrogen content of 0-10cm and 10-20cm (P>0.05), reaching a significant level in the soil layer of 20-30cm (P<0.05);Grazing rest had no significant effect on the total phosphorus content of the soil (P>0.05); the whole year's rest grazing significantly increased the total potassium content of the soil (P<0.01).The available nitrogen content of the rest grazing sample plot in the returning green period is extremely significantly higher than the annual rest grazing sample plot in the 0-10cm soil layer (P<0.01), and significantly higher than the traditional grazing sample plot (P<0.05),The rest grazing plot in the 10-20cm soil layer was significantly higher than the annual rest grazing plot (P<0.05),The grazing rest sample plot in the returning green period was significantly higher than traditional grazing in the 20-30cm soil layer (P<0.05).The available phosphorus content in the three soil layers is the re-greening rest grazing plot is extremely significantly higher than the annual rest grazing plot (P<0.01), the 0-10, 10-20 cm soil layer traditional grazing plot issignificantly higher than the whole year rest grazing plot (P<0.05), there was no significant difference between the traditional grazing plot in the 20-30cm soil layer and the annual rest grazing plot (P>0.05).The content of soil available potassium during the re-greening period was extremely significantly higher than that of the annual rest grazing plot (P<0.01).The 0-10, 20-30cm soil layer returning to the green period of the grazing restplot is extremely significantly higher than the traditional grazing plot (P<0.01) There was no significant difference between the annual rest grazing and traditional grazing (P>0.05).There is no significant difference in soil C/N, C/P and N/P in 0-10 and 10-20cm soil layers (P>0.05).The C/N of the 20-30cm soil layer was significantly higher inthe traditional grazing plot than in the rest grazing plot (P<0.05), and the C/P and N/P in the rest grazing plot were significantly higher than those in the traditional grazing plot (P<0.05).
Key words：Rest-grazing; Grazing; Plant community; Soil physical and chemical properties
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