近30年古尔班通古特沙漠短命植物的时空格局

基于1985—1999年的GIMMS-NDVI数据和2000—2014年的MODIS-NDVI数据提取短命植物的时空格局,结合野外调查数据和1985—2014年气象站点气温和降水数据,从不同时空尺度上分析了古尔班通古特沙漠短命植物的时空变化及其对气候变化的响应。结果表明:(1)古尔班通古特沙漠中短命植物层片整体表现出物种组成简单,优势度高、多样性和覆盖度低等特征,且层片特征主要是由优势物种所主导,在早春至盛夏期间,由于短暂的生活史造成层片整体在物候上有一个明显的起伏差异。(2)沙漠中短命植物覆盖度最高的区域为南部和中东部,北部次之,西部最少。就时间变化趋势而言,受近30年早春温度和冬春降水增加的影响,短命植物覆盖的区域面积呈现出明显的增加趋势。(3)1985—2014年间3、4月温度和冬春两季降水量呈上升趋势,而反映短命植物长势的NDVI值与冬春两季降水量也呈正相关性,但就相关性程度而言,冬季降水量与NDVI呈显著性相关(P0.05,r=0.405),而春季降水由于时滞效应并未表现出显著相关性。

Analysis of spatio-temporal patterns of ephemeral plants in the Gurbantünggüt Desert over the last 30 years

Ephemeral plants are a special plant synusia in the Gurbantünggüt Desert, which has attracted attention from ecologists due to its diverse species and significant role in ecology. To our knowledge, no research has analyzed the spatio-temporal patterns of ephemeral plants on a large-scale. Taking the Gurbantünggüt Desert -located in the central region of the Junggar Basin, northwest China-as the study area, and using remote sensing data, meteorological data, and field survey, this study explored the dynamic change in ephemeral plant cover in response to climate change on different spatio-temporal scales over the last 30 years. The results showed that, as far as the ephemeral plants synusia in the Gurbantünggüt Desert is concerned, the vegetation cover is low with simple community composition, high dominance, and low diversity, and the whole synusia undergoes an evident fluctuation in phenological change from early spring to summer. In addition to the phenological change in the ephemeral plant synusia, the normalized difference vegetation index (NDVI) in the desert also clearly fluctuates from early spring to summer, which is related to the life cycle of ephemeral plants. Using the phenological change characteristics of the ephemeral plant synusia, we extracted the NDVI during the phenological phases of ephemeral plants, and analyzed the spatio-temporal change of ephemeral plant cover from 1985 to 2014. In terms of spatial distribution, the highest cover area was in the south of the desert, followed by the mid-east and northern regions, with the western area showing the lowest cover area. With respect to temporal tendency, statistical analysis of the cover area showed that the ephemeral plant cover had a gradually increasing trend, which was attributable to an increase in temperature and precipitation during the research period. The highest cover area was in the oasis-desert ectone, which was due to the agricultural land located in this area. The artificial oases can supply sufficient surface water, which is beneficial for the growth of ephemeral plants. Conversely, the central desert region showed a low cover distribution pattern, which may be related to the lack of surface runoff and deep groundwater; the growth of ephemeral plants in the desert is completely reliant on atmospheric precipitation recharge. With respect to climate change, the spring temperature and precipitation showed an obvious increase from 1985 to 2014, and there was also an increase in winter precipitation. These notable increases in precipitation and temperature are of benefit to ephemeral plants. For yearly variation, the linear correlation coefficient indicated that NDVI was positively correlated with spring precipitation and winter precipitation. However, in terms of correlation coefficients, the NDVI was significantly positively correlated with winter precipitation (P < 0.05, r=0.405), whereas spring precipitation showed a weak positive correlation due to a time-lag effect. Moreover, according to an analysis of spatial differentiation of soil water content, climate change was not the key factor affecting the spatio-temporal change of ephemeral plants, but that the impact of human disturbance on the spatial distribution of ephemeral plants in local areas should be taken into consideration when assessing the large-scale spatio-temporal distribution of ephemeral plants. Therefore, in order to obtain a more accurate analysis of the dynamic change trends of ephemeral plants, future research will focus on human influence in local areas.