黄羊滩人工防风固沙林生态效益研究

Study on Ecologyical Efficiency of Wind-breaking and Sand-fixing forest in Huangyangtan

全面准确评价人工固沙林的生态效益,是人工固沙林可持续经营的理论依据。该文按照树种、林龄和配置模式,选择了京津风沙源南部区黄羊滩的18个有代表性的林分（草地）进行研究,选取了防风固沙、改良土壤、调节气候和物种多样性等方面的7个指标因子,运用灰色系统理论关联度分析法对人工林生态效益进行了综合评价。研究结果表明：防风固沙林的建立,降低了林地输沙率,固沙效益明显。13a生白榆林、7a生白榆林、26a生柠条和黄柳林等输沙率为0,固沙目标全面实现。进入退化阶段的沙打旺人工草地不能维持有效防护结构,输沙率为18.9g/cm·d,其它林分输沙率在0~10g/cm·d之间;防风固沙林也具有明显的小气候效应。除沙打旺草地外,其它林分均发挥不同程度的增加湿度和减缓温度变化的作用。其中17a生侧柏林相对湿度比空旷地提高了7.7个百分点,为湿度效应最大值,13a白榆林比空旷地温度日较差降低了2.8℃,为温度效应最大值;17a侧柏林、13a白榆林、26a柠条林、5a柠条林、沙地柏林、7a白榆林等6个林分与理想林分最为接近,这6个林分生态效益最好。沙打旺人工草地关联度最低,其综合生态效益最差;即侧柏、白榆、柠条和沙地柏营造的人工固沙林综合生态效益最好,可以在黄羊滩及周边地区大面积推广。沙打旺是流动、半流动沙地无可替代的先锋物种,生长衰退出现前,应及时引进功能更强的灌木树种进行改良。年龄较大的侧柏林、白榆林和柠条生态效益最明显,说明人工固沙林需要较长时间的恢复,生态效益才能充分发挥。

It＇s a theoretical basis for the sustainable management of sand-fixation plantations to comprehensively and accurately evaluate the ecological efficiency of the plantations. According to species, age and allocation model, this paper selected18 representative stands（grasslands）for research in Huangyangtan, and comprehensively evaluated the ecological efficiency with grey correlation analysis system theory through 7 index factors, such as windbreak and sand fixation, soil improvement, climate regulation, species diversity and so on. The results showed that it could reduce the sediment transport rate and had obvious sand-fixing effects to build sand-fixation plantations. The sand fixation target was fully realized with the sediment transport rate was 0 in 13 a Ulmuspumilaplantation, 7a Ulmuspumilaplantation, 26 a Caragana Korshinskii plantation and Salix gordejevii plantation. Astragalus adsurgens artificial grassland, in degradation stage, couldn＇t maintain an effectiveprotective structure, with the sediment transport rate18.9gocm-1·d-1. The others ranged from 0 to 10 gocm-1·d-1. The study also displayed thatsand-fixation plantations hadobviousmicroclimate effects. Except Astragalusadsurgensartificial grassland, the other stands played roles at different degrees in increasing the moisture and slowing down the temperature change. The humidity effectreached maximum in 17 a Platycladus orientalis plantation, with the relative humidity increasing by 7.7 compared withthe open area. While the temperature effectreached maximum in 13 a Ulmus pumila plantation, with the daily range of temperature decreasing by 2.8℃, compared with the open area. The ecological efficiency was the best in 17 a Platycladus orientalis plantation, 13 a Ulmus pumila plantation, 26 a Caragana Korshinskii plantation, 5a Caragana Korshinskii plantation, Sabina vulgaris plantation, and 7a Ulmus pumila plantation, which were the most close to an ideal stand. The correlation degree of Astragalusadsurgensartificial grassland was the lowest and the comprehensive ecological efficiency was also the worst.Platycladusorientalis plantation, Ulmus pumila plantation, Caragana Korshinskii plantation and Sabina vulgaris plantation had the best comprehensive ecological efficiency and could be popularized widely in huangyangtan and surrounding areas.On shifting sandy land and semi-shifting sandy land, Astragalus adsurgens was an irreplaceablepioneer species. After the growth peak, the flowing sand surface got fixed, and then shrub species should be introduced in time for improvement. Platycladus orientalisplantation, Ulmus pumila plantation and Caragana Korshinskii plantation in older age had the best ecological efficiency, suggesting that sand-fixation plantations needed a longer time forrecovery to create ecological efficiencyadequately.