乌兰巴托-锡林浩特样带草地植被特征与水热因子的关系

2012年夏季,研究人员对蒙古高原长约1100km的乌兰巴托—锡林浩特草地样带开展考察,获取了46个样地的物种数量、地上生物量等数据;基于全球GHCN(全球历史气象网络)数据集,提取了样带夏季(6—8月)月均温度和降水总量;继而根据自然地理和行政区边界,将草地样带大致分成北部(蒙古国乌兰巴托—蒙古国艾日格)、中部(蒙古国艾日格—中国苏尼特左旗)和南部(中国苏尼特左旗—中国锡林浩特),开展了分析。研究表明:(1)样带夏季平均温度的空间分布形态呈现明显的倒"U"型分布,南北两端温度较低,中部温度较高;夏季降水量在空间上的分布形态则与之相反,呈现南北两端降水量较高,中部降水量较低的正"U"型分布;(2)样带上植物物种数量、地上生物量的空间分布形态均呈现正"U"型分布,即在生态景观类型为典型温性草原的样带南部和北部地区,其生物多样性、地上生物量明显好于呈现为温性荒漠草原、温性荒漠景观的样带中部地区。(3)相关分析体现了大尺度(高原样带尺度)上植被特征与水热环境因子间的关系:植物物种数量、地上生物量与夏季月均温度均呈现负相关,而与夏季降水总量则呈现正相关关系。(4)偏相关分析反映了局地小尺度上植被特征与水热环境因子间的关系:温度和降水要素对于植物物种数量、地上生物量均呈现正相关。

The relationship between vegetation characteristics and hydro-thermic factors along the Ulanbattar-Xilinhot Grassland Transect of the Mongolian Plateau

During August of 2012, the research team carried out a field exploration of the Ulanbattar-Xilinhot Grassland Transect on the Mongolian Plateau. The transect was split into three parts according to the physical geographical conditions and practical administrative boundaries: the northern section (from Ulanbattar to Airag), the central section (from Airag to Sunitezuoqi), and the southern section (from Sunitezuoqi to Xilinhot). Along the 1100 km transect, 46 sample areas, 136 grass yield quadrats, and about 500 species-frequency plots were surveyed in detail and a series of species number data and above ground biomass data were then measured. Using GIS software and the GHCN datasets (The Global Historical Climatology Network), the historical meteorological data along the above transects were then extracted. The monthly average temperatures and total precipitation during the summer season (i.e., June, July and August) were calculated. Based on the vegetation characteristics data and hydro-thermic factor data, the correlation and partial correlation were analysed. The results show that: (1) the distribution of monthly average temperatures in summer are presented as an inverted "U" pattern along the transect, i.e., the northern and southern sections showing lower temperatures, while the central section maintained a high temperature level. Conversely, the distribution of total precipitation in summer is shown as an upstanding "U" pattern, i.e., high precipitation in the northern and southern sections, with low precipitation in the central section; (2) the distribution of numbers of plant species and above ground biomass are both depicted as an upstanding "U" shape along the transect. In the southern and northern regions, where the ecological type is typically warm steppe, both the bio-diversity and aboveground biomass are significantly better than those in the central region, where the ecological type is usually warm temperate desert grassland or temperate desert; (3) simple correlation analysis normally reflects the relationship between vegetation characteristics and hydro-thermic environmental factors over large scales (for example, plateau transect). In this study, the numbers of plant species and above ground biomass are negatively correlated with the summer monthly average temperature and are positively correlated with the summer precipitation; (4) the partial correlation analysis is inclined to reflect the relationship among different factors over a local scale (for example, small watershed). In this study, both the temperature and precipitation factors have positive effects on the number of plant species and the ground biomass.