短期增温对修复过程中藏北高寒退化草地生产力的初期影响

Initial effects of short-term warming on the productivity of alpine degraded grassland in northern Tibet during the restoration process

为了探讨气候变暖对修复过程中藏北高寒草地生产力的影响,以藏北地区自然恢复草地(NR)、免耕补播草地(S)和翻耕补播草地(TS)为研究对象,原生重度退化草地为对照(CK),采用被动式增温法—开顶式气室法(OTC)进行模拟增温,探究植物群落特征、生物量和物种多样性对短期增温的响应。结果表明:1)增温使表层土壤温度平均上升1.34℃,土壤湿度平均下降4.18%。2)经短期增温后,植物群落盖度显著增加(P<0.05),高度显著降低(P<0.05);原生重度退化草地生物量向地下部分转移,自然恢复草地、免耕补播草地和翻耕补播草地生物量向地上部分转移;翻耕补播草地地上生物量显著降低(P<0.05)。3)短期增温使禾草的地上生物量和重要值降低(P<0.05),杂草的地上生物量和重要值增加(P<0.05)。4)增温使原生重度退化草地的物种丰富度指数、ShannonWiener指数和Simpson指数显著增加了17.65%、18.54%、11.52%(P<0.05),S处理Pielou指数显著降低(P<0.05)。5)短期增温后,地上生物量与物种多样性指数呈极显著负相关(P<0.01);地下生物量与物种多样性指数、群落特征无显著相关性。综上所述,短期增温对藏北原生重度退化草地物种多样性的恢复具有一定积极作用,并使自然恢复草地和免耕补播草地的生产力有所恢复,而抑制并降低了翻耕补播草地的生产力。

Climate warming is expected to affect the productivity of alpine grassland in northern Tibet,and this may affect the grassland restoration process.The aim of this study,therefore,was to determine the effects of a shortterm temperature increase on the productivity of alpine grassland during restoration.Natural restored grassland(NR),no-tillage replanted grassland(S),and tilled replanted grassland(TS),with native heavily degraded grassland as the control(CK),were subjected to a warming treatment using the open top chamber method.The changes in the plant community,biomass,and species diversity in response to this short-term temperature increase were determined.The results showed that:1)Warming increased the surface soil temperature by an average of 1.34℃and decreased the soil moisture content by an average of 4.18%.2)After short-term warming,the plant community cover increased significantly(P<0.05)and the height of plant community decreased significantly(P<0.05);the biomass of vegetation in CK transferred to the underground plant parts,the biomass of vegetation in NR,S,and TS shifted to the aboveground plant parts;and the aboveground biomass decreased significantly in TS(P<0.05).3)Short-term warming decreased the aboveground biomass and importance value of grasses(P<0.05)but increased the aboveground biomass and importance value of forbs(P<0.05).4)In CK,warming significantly increased the species richness index,Shannon-Wiener index,and Simpson index by 17.65%,18.54%,and 11.52%,respectively(P<0.05).In S,the warming treatment resulted in a significant decrease in the Pielou index(P<0.05).5)After short-term warming,the above-ground biomass showed a highly significant negative correlation with the species diversity index(P<0.01);however,the below-ground biomass showed no significant correlation with the species diversity index or community characteristics.In conclusion,short-term warming had a certain positive effect on the recovery of the species diversity in native heavily degraded grassland in northern Tibet.Short-term warming restored the productivity of naturally restored grassland and no-tillage replanted grassland,but suppressed the growth and reduced the productivity of tilled replanted grassland.