丹江口水库水滨带植物群落空间分布及环境解释

探讨了环境因素对丹江口水库(南水北调中线水源地)水滨带植物群落空间分布的影响。通过对水滨带植物群落和环境因素的实地调查,用双向指示种分析(TWINSPAN)对201个水滨带植物群落进行分类;结合地形、土壤和水文因素用除趋势典范对应分析法(DCCA)分析环境因素对水滨带植物群落的影响;并对环境因素的解释能力进行定量分离。结果表明:(1)水滨带植物群落包括7种类型,分别是萹蓄群落、苘麻群落、细叶水芹+狗牙根群落、狗牙根群落、响叶杨-狗牙根群落、杜梨-白刺花-狗牙根群落和侧柏-牡荆-三穗苔草群落;(2)海拔和水淹影响对水滨带植物群落空间分布具有主导作用。海拔升高,水淹影响减弱,植物群落呈现由草本植物群落向木本植物群落变化的格局;(3)土壤因素的解释能力大于地形因素,水文因素的解释能力最小。各类环境因素之间存在交互作用,地形、水文和土壤因素三者间的交互作用最大,地形和土壤因素之间的交互作用最小。环境因素共解释水滨带植物群落空间分布的21.99%,未解释部分为78.01%。结果证明环境对植被的解释能力是由植被的复杂程度决定的,植被越复杂,环境的解释能力越低。

Spatial distribution of plant communities and environmental interpretation in the riparian zone of Danjiangkou Reservoir

Riparian vegetation performs important ecological functions in protecting water quality, stabilizing the bank, maintaining habitats connectivity and enhancing local biodiversity. Yet, riparian vegetation has been degraded severely throughout the world mainly due to anthropogenic disturbances. This study focused on the riparian vegetation communities and the impact of environmental factors on spatial distribution of plant communities in the riparian zone of Danjiangkou Reservoir, the water source for the Middle-Route of the South-to-North Water Transfer Project. Field survey was carried out from April to May, 2011. The 201 plant communities were investigated. And three topographic factors (elevation, slope and aspect), eight soil factors (soil thickness, soil texture, soil pH, organic matter, total nitrogen, total phosphorus, available nitrogen, and available phosphorus), and two hydrological factors (flooding duration and flooding frequency) were measured. On the basis of the investigation of riparian plant communities and environmental factors, the 201 plant communities were classified into different community types by means of Two Way Indicator Species Analysis (TWINSPAN); the impact of environmental factors on riparian plant communities were analyzed by using Detrended Canonical Correspondence Analysis (DCCA) combined with topographic, hydrologic and soil factors. And the explanatory power of environmental factors on the riparian plant community was quantitatively partitioned. The results showed that (1) the riparian plant communities were classified into seven types of Polygonum aviculare community, Abutilon theophrasti community, Oenanthe dielsii var. stenophylla + Cynodon dactylon community, Cynodon dactylon community, Populus adenopoda-Cynodon dactylon community, Pyrus betulifolia-Sophora davidii-Cynodon dactylon community and Platycladus orientalis-Vitex negundo var. cannabifolia-Carex tristachya community; (2) the results of DCCA indicated that riparian vegetation and environmental factors had a significant correlation. The first axis had a significant correlation with elevation, flood duration and flood frequency, it indicated that elevation and flooding played a dominant role in spatial distribution of the riparian plant communities. Soil organic matter content, pH and total nitrogen content presented a significant correlation with the second axis, which indicated that soil nutrient also played a role in spatial distribution of the riparian plant communities. (3) the effects of soil factors, hydrology factors, topographic factors and their interaction on the total variation of riparian vegetation were quantitatively partitioned and showed that the contribution rate of the soil factors was 10.24% separately, and the contribution rate of the topographic factors was 3.15% and the hydrological factors was 3.04% separately. 0.73% for soil factors coupled with topographic factors, 1.22% for topographic factors and hydrological factors, 0.75% for hydrology factors with soil factors, and the interactive effect of topographic, soil and hydrological factors was 2.86%. The collected environmental factors accounted for 21.99% of spatial distribution of the riparian plant communities, the unexplained portion for 78.01%. Our results demonstrated that the explanatory power of environmental factors was determined by the complexity of vegetation, and the more complexity of vegetation, the less explanatory power by environmental factors. The riparian zone is a typical ecotone, and environment and vegetation are complicated and varied. These caused that the explanatory power of environmental factors was low. The unexplained portion may be caused by climate, biotic interaction, interference and random factors.