青藏高原高寒草甸夏季植被特征及对模拟增温的短期响应

A research on summer vegetation characteristics & short-time responses to experimental warming of alpine meadow in the Qinghai-Tibetan Plateau

以青藏高原高寒草甸为研究对象,研究了草甸植被夏季生长动态特征;同时采用红外辐射器模拟增温的方法,探讨了草甸植被对增温的短期(1a)响应。结果表明:(1)高寒草甸夏季植被高度与地下生物量、总生物量相关性不显著,盖度与二者相关性极显著;高度对地上生物量影响较大(R=0.892,P<0.01),盖度对地下生物量(R=0.883,P<0.01)和总生物量(R=0.888,P<0.01)影响较大。(2)高寒草甸夏季植被地上部分和地下部分表现出不同的生长模式,地上部分近似等速生长(幂指数为1.011),地下部分则表现为异速生长(幂指数为0.459),但整体呈现异速生长(幂指数为0.473)。(3)高寒草甸夏季植被地上生物量(P<0.05)在6月份较地下生物量(P>0.05)对环境更为敏感,且一年之后地上-地下生物量均呈减小趋势,这与空气温度、土壤温度和土壤水分的显著减小密切相关。(4)红外辐射器在高寒草甸的增温度效果较好,空气、地表、土壤温度都随增温幅度增强而增加;短期增温对高寒植被有正效应(T0—T1),而温度持续升高则对植被产生负效应(T1—T2);各植被指标的方差分析都未达到显著水平,表明短期增温对该植被影响不显著。

Climate warming has become a credible fact due to the increase of greenhouse gases. It is generally believed that the responses of ecosystem to elevated temperature are greatly sensitive and swift in high-latitude and high-elevation regions, especially in the Qinghai-Tihetan Plateau （QTP） , which has been considered as an ideal region to study the responses of terrestrial ecosystem to global climate changes. Some relevant researches have revealed that the QTP has a warming trend at the rate of 0. 032 °C per year. As one of the typical vegetation types in the QTP, alpine meadows are extremely fragile and significantly sensitive to climate warming. Once destroyed, it would he very difficult for them to recover in a short time, which would result in their degrading or desertification. Therefore, it is extremely important and urgent to become aware about the dynamic changes of alpine meadow vegetation due to climate warming in the QTP. In this study, infrared radiator heaters were used for experimental warming research job. And the results from this study are as follows： （1） Vegetation characteristics of alpine meadow in summer. In summer, there was no significant correlation between vegetation height and belowground biomass （P〉0.05）. However, vegetation height was more correlated with ahovegroundbiomass （ R = 0. 892, P〈0.01 ） , while vegetation coverage was more related to belowground biomass （ R = 0. 883, P〈0.01 ） and total biomass （R = 0. 888, P〈0.01 ）. The vegetative above-and belowground parts of alpine meadow showed different growth patterns, owing to the larger differences among their environments, especially the larger difference between ground and air temperature. The aboveground parts approximated the pattern of isometry with the power exponent of 1.011 and the belowground parts had a pattern of allometry with the power exponent of 0. 459, but the whole presented an allometry pattern with the power exponent of 0. 473. The vegetative above-and belowground biomass of alpine meadow tended to decrease after one year （2010-6---2011-10） and aboveground biomass （P〈0.05） was more sensitive to surrounding environments than belowground biomass （ P 〉 0.05 ） in June, which were related to the significant decrease of soil temperature, soil water content and air temperature （P〈0.05）. Therefore, the responses of aboveground biomass to temperature and water content were stronger than belowground biomass after one year and the inter-annual variation of biomass was large. （2） Responses of environment and vegetation of alpine meadow to wanning after one year. The warming effects of infrared radiators were better in alpine meadow with the increase of air, surface, soil temperature of 0.07 °C （ at 20 cm height）, 1.66 °C, 1.23 °C （at 20 cm depth） respectively in T1 warming treatment （the warming degree is 1 °C ）, and 0. 29 °C （at 20 cm height）, 2.18 °C, 2.34 °C （at 20 cm depth） respectively in T2 warming treatment （the degree is 3 °C ）. Warming affected soil temperature at the 0--40 cm layer （ P〈0.05 ） much more than the 60--100 cm layer （ P〉 0.05 ）. The warming effects on soil temperature were weakened with soil depth, while the effects on soil water content were enhanced with soil depth. Warming pushed most soil water at the 0--40 cm layer down to deeper soil layers and was significantly different at the 100 cm depth. The warming effects on vegetation varied in different months. In a short time, warming enhanced vegetation height, coverage, above-and belowground biomass at early stage （ T0--T1 ）, and weakened them at later stage （T1--T2）. Overall, warming had a positive effect on the vegetation of QTP, but it may turn negative with increasing temperature. However, the both warming effects were not significant, so the effects of warming on the vegetation of QTP alpine meadow were not significant over a short time.