乡土植物生活型构成对川渝地区边坡植被水土保持效益的影响

乡土植物灌木化建植是高速公路边坡防护的重要生态模式。为了探讨生态恢复过程中乡土植物的生活型构成对边坡植被水土保持效益的影响,揭示乡土植物生活型-物种多样性-生态系统功能间的偶合关系,借助3个物种配置试验,于2009年4月构建了以草本、灌木或乔木为主体的草本型、灌木型、乔木型绿化配置及草-灌-乔混合型试验区。自建植次年(2010年)起,对试验区进行持续5a生态监测。结果表明:1)边坡植被的物种丰富度与乡土植物的生活型有关,呈现乔木型灌木型草-灌-乔混合型草本型趋势;2)植被的物种多样性(Shannon-Wiener指数、Pielou指数)与乡土植物生活型构成及建植年限有关:建植后第1、第2年,多样性水平呈草本型草-灌-乔混合型灌木型乔木型变化趋势;自建植后第三起(2012—2014年),呈草-灌-乔混合型草本型灌木型乔木型波动;3)植被的水土保持性能(径流系数、侵蚀模数)与群落的物种多样性密切相关:多样性水平越高,水土保持性能越强。可见,乡土植物的生活型构成对提高边坡植被的物种多样性、改善生态性能至关重要。

Effect of life form composition of indigenous plant species on soil and water conservation on slopes in Sichuan-Chongqing region

Reconstruction of plant communities on superhighway side slopes using native shrubs is an important ecological practice that is employed for stabilization of the slopes. To advance the ecological restoration process of slope vegetation, we evaluated the impacts of the life form composition of indigenous plant species on soil and water conservation properties on the slopes using three representative ecosystems, Miscanthus sinensis + Buchloe dactyloides, Neosinocalamus affinis + Indigofera pseudotinctoria, and Cupressus funebris + Leucaena leucocephala, in southwest China. Four ecological models represented by tree-, shrub-, and herb-dominated experimental plots (AAX_i, SSX_i, and HHX_i, respectively), which were composed of one of the three ecosystems and one of the indigenous dominant species (Buchloe dactyloides, Lolium perenne, Vitex negundo, Amorpha fruticosa, Ailanthus altissima, and Robinia pseudoacacia), and by herb-shrub-tree-dominated experimental plots (HSA), which were composed of three dominant species, were reconstructed via a three-species assembly experiment in April, 2009. The generation of surface runoff and soil erosion were investigated in the plots and the correlation between the life forms of indigenous species, species diversity, and levels of soil and water conservation in the ecosystems were analyzed from 2010 to 2014. The results showed that the fluctuation in plant species richness between communities of the same age decreased in the order of AAX_i > SSX_i > HAS > HHX_i from 2010 to 2014. Shannon-Wiener index and Pielou''s index indicated that life forms of the indigenous species growing on the slopes affected plant species diversity, which fluctuated with community phases. From 2010 to 2011, these indices varied in the following order HHX_i > HSA > SSX_i > AAX_i, and from 2012 to 2014, they varied in the order of HSA > HHX_i > SSX_i > AAX_i. Of the four ecological models tested, the runoff coefficient and erosion in the period from 2010 to 2011 was the lowest in HHX_i plots, followed by HSA plots, whereas from 2012 to 2014, the HSA plots manifested a more prominent soil and water conservation compared to other ecological models, while these properties continued being the lowest in HHX_i plots. The plant species diversity of the slope vegetation was closely related to its capacity for soil and water conservation as indicated by the determination coefficient of more than 0.951; the higher species diversity in a given community, the smaller the runoff coefficient and erosion modulus. The results from this study suggested that the life form of indigenous species plays an important role in increasing plant species diversity and improving soil and water conservation properties of side slopes.