三江平原残存湿地斑块特征及其对物种多样性的影响

景观破碎化是当前一个突出的生态学问题,破碎斑块的大小和形状特征对物种多样性具有重要影响。选取三江平原别拉洪河流域为研究区,通过调查残存湿地斑块的面积、形状和植物物种丰富度,利用相关分析和回归分析等方法研究了残存湿地斑块特征及其对物种多样性的影响。研究结果表明:在强烈的人为活动干扰下,三江平原湿地破碎化严重,残存湿地斑块面积较小,斑块形状规则、边界简单。斑块形状指数、分维数、形状特征点数和斑块面积、物种丰富度均没有显著相关关系,而斑块面积、周长和周长面积比对物种丰富度具有显著影响。但是斑块周长和周长面积比均受面积的直接影响,所以斑块面积是决定物种丰富度的主要因素,这点需在湿地生物多样性保护中予以重视。虽然斑块形状特征点数是农业景观物种丰富度的一个很好预测指标,但是该指标不适用于形状规则的残存湿地斑块物种丰富度预测。另外,对于残存湿地斑块种-面积关系的机理还有待进一步研究。

The patch characteristics of wetland remnants in the Sanjiang Plain and its influence on plant species richness

Landscape fragmentation leads to patch size and shape changes, and many studies proved that patch size and patch shape have important influence on species diversity. The Sanjiang Plain is the largest freshwater wetlands in China. However, the wetland had been fragmented into a patchy mosaic of isolated remnants as a result of anthropogenic activity since the 1950s. In this study, the patch characteristics and plant species richness on wetland remnants in the Bielahong River basin, a typical region in the Sanjiang Plain, were investigated. The study results show that the wetland had been seriously fragmented into small wetland remnants under the intense anthropogenic activity. Most remnant patches are less than 2hm2, with regular shape and simple boundary. Three indices of patch shape complexity, including shape index (SI), fractal dimension (Fd) and the number of shape characterizing points (NSCP), are uncorrelated with patch size and plant species richness, but plant species richness is significantly associated with path size, perimeter and the ratio of perimeter and area (P/A). As patch size controls the variance of patch perimeter and P/A, it is the main determinant of plant species richness. Although the NSCP proposed by Moser et al. is a good predictor for plant species richness in agricultural landscape, it was not applicable in the regular wetland remnants. However, exploring the mechanisms for the significant species-area relationship would help us understand species diversity pattern in wetland remnants, which needs to be considered in further studies.