模拟增温对青藏高原高寒草甸根系生物量的影响

在青藏高原高寒草甸布设模拟增温实验样地,采用土钻法于2012—2013年植被生长季获取5个土层的根系生物量,探讨增温处理下根系生物量在生长季不同月份、不同土壤深度的变化趋势及其与相应土层土壤水分、温度的关系。结果表明:(1)根系生物量在2012年随月份呈增加趋势,其中7—9月较大,其平均值在对照、增温处理下分别为3810.88 g/m~2和4468.08 g/m~2;在2013年随月份呈减小趋势,其中5—6月较大,其平均值在对照、增温处理下分别为4175.39 g/m~2和4141.6 g/m~2。增温处理下的总根系生物量高出对照处理293.97 g/m~2,而各月份总根系生物量在处理间的差值均未达到显著水平。表明在增温处理下根系生物量略有增加,但在生长季不同月份其增加的程度不同,致使年际间的增幅出现差异。(2)根系生物量主要分布在0—10 cm深度,所占百分比为50.61%。在增温处理下,0—10 cm深度的根系生物量减少,减幅为8.38%;10—50 cm深度的根系生物量增加,增幅为2.1%。相对于对照处理,增温处理下0—30 cm深度的根系生物量向深层增加,30—50 cm深度的根系生物量增加趋势略有减缓。可见,在增温处理下根系生物量的增幅趋向于土壤深层。(3)根系生物量与土壤水分呈极显著的递减关系,在增温处理下线性关系减弱;与土壤温度呈极显著的递增关系,在增温处理下线性关系增强。表明土壤水分、温度都可极显著影响根系生物量,但在增温处理下土壤温度对根系生物量的影响较土壤水分更为敏感而迅速。

Effects of experimental warming on the root biomass of an alpine meadow on the Qinghai-Tibetan Plateau, China

The Qinghai-Tibetan Plateau (QTP) has been considered an ideal region in which to study the responses of terrestrial ecosystems to climate change. The alpine meadow, a typical vegetation type of the QTP, is extremely fragile and highly sensitive to climate change. Once destroyed, reestablishing these meadows in a short timeframe has proven to be very difficult; their loss would result either in landscape degradation or desertification. Therefore, an understanding of the dynamic changes to the alpine meadow vegetation of the QTP caused by climate change is extremely important and urgently needed. In previous research, we chose an alpine meadow in the QTP as our study area and established 20 experimental plots with a randomized block design, comprising five replicates and four treatments: a control, warming alone, clipping alone, and a combination of warming and clipping. In this study, we tested the control and the warming plots independently and sampled root biomass using a soil auger with an inner diameter of 7 cm. Samples were collected from soil layers of 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, and 40-50 cm during the growing season, from May to September in 2012 and 2013. This study explored variations in root biomass occurring in different months and at different soil depths during the growing season, as well as correlations between biomass and the moisture and temperature of the corresponding soil layers. The results show that (1) root biomass tended to increase over time in 2012, peaking from July to September and with the mean being 3811 g/m² and 4468 g/m² in the control and warming treatments, respectively. However, root biomass decreased over time in 2013, peaking in May and June with an average value of 4175 g/m² and 4142 g/m² in the control and warming treatments, respectively. Total root biomass was larger in the warming treatments than in the control, with a mean difference of 293.97 g/m². Conversely, there were no significant differences in total root biomass between treatments in the various months. Warming treatments resulted in slightly increased root biomass, but the magnitude of the increase varied widely among months in the growing season, which resulted in differences in the increase in inter-annual root biomass. (2) The root biomass was primarily distributed at depths of 0-10 cm, where 50.61% of all roots were localized. In the warming treatments, root biomass declined by 8.38% in the 0-10 cm soil layer, whereas it increased by 2.1% in the 10-50 cm soil layer. Relative to the control treatments, the root biomass at depths of 0-30 cm tended to increase in the deeper soil layers, with the increasing trends being slightly less pronounced at depths of 30-50 cm. Therefore, in warming treatments, the root biomass tended to be greater in deeper soil layers. (3) Warming treatments caused a highly significant decrease in root biomass and soil moisture. However, root biomass increased very significantly with increase in soil temperature, which was elevated in the warming treatments. This illustrates that soil moisture and temperature both had highly significant effects on root biomass, but the effects of soil temperature were more intense and took effect more rapidly than the effects of soil moisture.