新疆杨树/紫花苜蓿林草复合系统中根系分布特征及生产力

为了解杨树（Populus L.）/紫花苜蓿（Medicago sativa L.）林草复合系统中两种植物根系的分布及相互关系，利用WinRHIZOTM对3 a生紫花苜蓿和7 a生杨树在单作和间作条件下0~60 cm土层中的根长密度（RLD）、平均根直径（ARD）和比根长（SRL）的分布进行测定分析。结果表明：间作紫花苜蓿RLD降低了10.01%~54.29%，20~60 cm土壤中紫花苜蓿ARD降低了11.15%~37.30%, 间作苜蓿的SRL比单作苜蓿高10.52%~28.78%；间作增加了 0~40 cm土层中杨树ARD的20.36%~28.08%，增加了苜蓿种植区域0~20 cm土层中杨树RLD的15.51%~34.23%。杨树SRL受到的影响较小，仅在8月5日的0~20 cm 土层中测得单作和间作SRL存在差异，单作杨树SRL比间作杨树高14.46%。单作和间作苜蓿的最高产量均在第一次收获时期，间作降低了苜蓿的产量，在第一次、第二次和第三次收获中产量分别降低了24.7%、30.9% 和 43.7%，与单作苜蓿相比，杨树/紫花苜蓿林草复合系统中苜蓿的总产量减少了31.2%。通过计算土地当量比，发现杨树与紫花苜蓿复合经营为杨树林带增加了额外来自紫花苜蓿的收入，能够提高系统41%的生产力。综上所述，林草复合系统中紫花苜蓿根系分布及生长受到了不利影响，而杨树根系受到了有利的影响。相比单作种植，林草复合系统有较高的生产力和资源利用效率，具有提高新疆地区防护林带生态和经济回报率的潜能。

Root distribution characteristics and productivity in a poplar/alfalfa silvopastoral system

In order to investigate the root distribution and relationship of a poplar (Populus L.)/alfalfa (Medicago sativa L.) silvopastoral system, the spatial distributions of root length density (RLD), average root diameter (ARD), and specific root length (SRL) of 3-year-old alfalfa and 7-year-old poplar in the 0~60 cm soil depth in sole and intercropping systems, were determined and analyzed by WinRHIZOTM software. The result showed that intercropping reduced 10.01%~54.29% RLD of alfalfa, and reduced 11.15%~37.30% of ARD of alfalfa in the 20~60 cm soil layer. The specific root length (SRL) of intercropped alfalfa was 10.52%~28.78% higher than that of sole alfalfa. Oppositely, intercropping increased 20.36%~28.08% of ARD of poplar in the 0~40 cm soil layer, and increased 15.51%~34.23% of the RLD of poplar in the alfalfa grown areas in the 0~20 cm soil layer. The poplar SRL was less affected, and the difference between sole|cropped and intercropped SRL was determined only in the 0~20 cm soil depth on August 5, the sole|cropped poplar SRL was 14.46% higher than intercropping. The highest yield of sole|cropped or intercropped alfalfa was both at the first harvest stage, and intercropping reduced the yield of alfalfa. In the first, second, and third harvests, the yield decreased by 24.7%, 30.9%, and 43.7%, respectively. The total yield of alfalfa in the poplar/alfalfa silvopastoral system was reduced by 31.2%, compared with the sole cropping. According to the land equivalent ratio, the combination of poplar and alfalfa added additional income from alfalfa, and it increased the productivity rate by 41%. In summary, the root distribution and growth of alfalfa in forest and grass complex system were adversely affected, and the root system of poplar was beneficially affected. Compared with the sole cropping, the silvopastoral system had higher productivity and resource utilization efficiency, and had the potential to improve the ecological and economic return of the shelter belt in Xinjiang.