黑河下游荒漠河岸林典型样带植被空间异质性

应用地统计学的理论与方法,分析了黑河流域下游荒漠河岸林主要种群,即老林胡杨(Popu luseuphratica)、幼林胡杨、柽柳(Tamarix chinensis)和苦豆子(Sophora alopecuroides)的空间异质性程度、异质性组成及尺度依赖问题.结果表明:黑河下游荒漠河岸林种群斑块格局明显,斑块内部异质性较小,斑块之间异质性增强,出现空间异质性变化较大的尺度为430m.而斑块内部因不同种群而变化,苦豆子和柽柳具有较大的空间异质性尺度,分别为43m和55m.老林和幼林胡杨种群的空间异质性尺度(8m和13m)较小,但异质性存在多尺度变化.采用30m分辨率的遥感数据能够较好地分析种群斑块格局,但是对种群内的空间异质性分析需要更高的分辨率.

Characteristics of Spatial Heterogeneity of the Desert Riparian Forest in the Hei River Basin

Geo-statistical techniques are used to evaluate spatial characteristics of the desert riparian forest at the down stream of the Hei River in the arid area of northwest China. Spatial structures of different vegetation populations were characterized by means of nugget, range and sill parameters of spherical or exponent model variograms. Model variograms reveal that different vegetation populations have distinctive spatial properties, which are quantified effectively by the parameters of the models. Model variograms were fitted to the experimental variograms, which were calculated from width of plant bosom and vegetation coverage measured at 1 sampling transect of 2 000 m×5 m, 5 sampling transects of 500 m×5 m and 3 sampling transects of 200 m×2 m. Transects of 2 000 m×5 m were laid out between river and desert, the other transects were laid out in different vegetation populations. Desert riparian forests in the Hei River Basin show the spatial distributive pattern of patchiness, the main populations are older Populus euphratica; younger Populus euphratica; Tamarix chinensis; Sophora alopecuroides and so on. The maximum model variogram range was 55 m for all populations, suggesting that transects must at least be such long to classify the riparian forests unambiguously into the populations currently recognized. Experimental variograms were calculated for all plants in each of four mapped vegetation populations. The Tamarix chinensis and Sophora alopecuroides populations have distinctively long range, but the spatial heterogeneity of Populus euphratica populations has multiscale changes. At the scale of community, spatial heterogeneity of vegetation increases and also has multiscale changes. According to analyses, the spatial heterogeneity of community has distinctive change at the scale of 400 m, and this is also the scale of population patchiness turnover. These findings support use of high-resolution remote sensors and geostatistics for determining vegetation community structure of desert riparian forests. Spatial pattern information produced by these methods could improve broad scale vegetation classifications produced by low-resolution remote sensing systems.