三工河流域琵琶柴群落特征与土壤因子的相关分析

琵琶柴(Reaumuria soongorica)是我国荒漠地区分布最广的地带性植被类型之一,对维系荒漠地区生态系统的稳定性具有重要作用。以三工河流域两个琵琶柴群落为对象,在2010年主要生长季节(6—10月),通过群落和土壤调查,采用土钻法、土柱法、地上收割法对两个琵琶柴群落的土壤性质、生物多样性、细根生物量、地上生物量、生物多样性与土壤性质的关系进行研究,结果表明:两个琵琶柴群落在冠幅、盖度、多度和物种多样性等方面均存在显著差异。在0—100 cm土壤层内,两个群落土壤电导率、pH值、容重、含水量存在显著差异。除土壤容重外,群落2各个土壤因子的值均大于群落1,并随土壤深度的增加表现出类似的趋势。两个群落物种多样性指数、地上生物量、细根生物量存在显著差异,从6月到10月呈现先下降再上升的趋势。由于7、8月群落1有大量夏雨型短命植物和类短命草本植物的出现,Shannon-Wiener多样性指数、Pielou均匀度指数急剧降低,Simpson指数表现出相反的变化趋势。群落2土壤电导率和pH值较高,草本植物鲜有出现,多样性指数和均匀度指数变化均较为平缓。两个群落的Sorenson相似性系数较低,群落差异明显。相关和回归分析表明土壤环境因子是导致两个琵琶柴群落特征、生物多样性和生物量不同的主要因素。较高的土壤含水量可以增加琵琶群落的生物多样性,较高的土壤容重抑制琵琶柴群落细根的生长,轻度的干旱胁迫促进地上生物量的积累,一定浓度的土壤pH值和土壤盐分可以促进琵琶柴群落细根的生长。

Correlation between characteristics of Reaumuria soongarica communities and soil factors in the Sangong River basin

Reaumuria soongarica is one of the most widely distributed plant species in arid regions of China and has an important role in maintaining the stability of the desert ecosystem. On the basis of field data, including the species composition, number of species, plant height, coverage and abundance, and selected soil properties (electrical conductivity, pH, bulk density and moisture content), the fine root biomass and aboveground biomass of two R. soongarica communities in the Sangong River basin were investigated over the course of the main growing season (from June to October) of 2010. In addition, by calculation of derivative biodiversity indices comprising Pielou's evenness index, Simpson's dominance index, the Shannon-Wiener diversity index, and Sorenson's similarity index, the relationships between fine root biomass, biodiversity and soil properties of the two communities were analyzed. The results showed that the crown area, coverage, abundance, species number, Pielou's evenness index, Simpson's dominance index, Shannon-Wiener diversity index, aboveground biomass, fine root biomass, and the soil electrical conductivity, pH, bulk density and moisture content in the 0-100 cm soil layer of two R. soongarica communities were significantly different. Except for soil bulk density, the values of all soil properties of Community 2 were higher than those of Community 1, and showed similar trends with increment in soil depth. Except for species number and Simpson's dominance index, the other biodiversity indices decreased initially and thereafter increased from June to October, whereas the aboveground biomass and fine root biomass increased initially and thereafter decreased from June to October. Owing to the appearance of a large number of summer rain-dependent herbs in July and August in Community 1, the Shannon-Wiener diversity index and Pielou's evenness index showed sharp reductions over the growing season, whereas Simpson's dominance index showed the opposite trend. Compared with Community 1, Community 2 had higher soil electrical conductivity and soil pH, and few summer rain-dependent herbs, and therefore the Shannon-Wiener diversity index, Pielou's evenness index and Simpson's dominance index changed only moderately. In addition, Sorenson's similarity coefficient was small and the difference between the two communities was significant. Regression analysis showed that soil properties were determinants of the differences in biodiversity and biomass of the two communities. High soil moisture content increased biodiversity, high soil bulk density inhibited fine root growth, and certain soil pH and soil salt contents promoted fine root growth in R. soongarica communities. We concluded that soil salt content and soil pH are the main factors that restrict biodiversity, community structure, and growth of R. soongarica in the Sangong River basin. Differences in microenvironments, especially in soil characteristics, could induce strong differences in two communities with identical dominant species in the same climatic zone. These findings provide a scientific base for management of natural R. soongarica communities and rehabilitation of degraded communities, as well as for improvement of soil salinization in arid regions of China.