Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
J Environ Qual. 2011 May-Jun;40(3):815-24. doi: 10.2134/jeq2010.0137.
Assessing environmental effects of shelter forests is primarily necessary for realizing their greatest protective benefits. The Three-North Shelter Forest Program (TNSFP), the largest ecological afforestation program in the world, has been operated for three decades in China but so far lacks comprehensive assessment of its environmental impacts. Horqin Sandy Land (HSL) in Northeast China is one of the key areas in the TNSFP implementation. To identify the principal contributors to environmental changes in HSL, we evaluated impacts of variations in landscape features, shelter forest areas, climatic factors, and social factors on changes in sandy land areas from 1978 to 2007, by using Gray Relational Analysis. Our analysis showed that during the period 1978 to 2007, the sandy land area decreased by 3.9% in low aeolian dunes, 14.5% in low mountains and hills, and 98.9% in high elevation alluvial flats of HSL. Factors with Gray Correlation Degrees >0.9 were identified as the patch shape index (PSI) and the landscape isolation index (LII) of grasses in low aeolian dunes, PSI of grasses in mountains and hills, and area of broadleaved forests and LII of shrubs in alluvial flats. It is concluded that establishment of the shelter forests has played a significant role in controlling the expansion of sandy land in HSL. To sustain the long-term environmental benefits of the shelter forests in the remaining period for TNSFP construction, suitable tree species should be selected and planted at appropriate densities based on the local precipitation, groundwater and landform conditions, and the system stability of the total landscape.
评估防护林的环境影响对于实现其最大的保护效益至关重要。三北防护林体系建设工程（TNSFP）是世界上最大的生态造林工程，在中国已经运行了三十年，但迄今为止，其环境影响仍缺乏全面评估。中国东北科尔沁沙地（HSL）是 TNSFP 实施的重点区域之一。为了确定 HSL 环境变化的主要驱动因素，我们采用灰色关联分析评估了景观特征、防护林面积、气候因素和社会因素变化对 1978 年至 2007 年沙化土地面积变化的影响。分析表明，1978 年至 2007 年间，HSL 的低风成沙丘、低山丘陵和高海拔冲积平原的沙化土地面积分别减少了 3.9%、14.5%和 98.9%。灰色关联度大于 0.9 的因素被确定为低风成沙丘的斑块形状指数（PSI）和草地景观隔离指数（LII）、山地丘陵的 PSI 和阔叶林面积以及冲积平原的灌木 LII。研究结果表明，防护林的建立对控制 HSL 沙化土地的扩展起到了重要作用。为了在 TNSFP 建设的剩余时间内维持防护林的长期环境效益，应根据当地的降水、地下水和地形条件以及整个景观的系统稳定性，选择适宜的树种，并以适当的密度进行种植。
