Abstract: Based on assessment of climatic ecological adaptability of leguminous grass in returning farmland to forest,a case study on effects of tree-grass models on climate resource efficiency in Zhongyang County of Shanxi Province was conducted,compared with the tree-weed model.The results showed that the leguminousgrasses,such as Astragalus adsurgens、Melilvtus suaveolens and Medicago sativa were suitable to plant in young plantations of experimental area.The growing stage of Astragalus adsurgens was longest among the three leguminous grasses,and its hydrothermal coefficient was the highest.During the growing stage of leguminous grasses in 2002 and 2003,for three tree-grass complex systems of Platycladus orientalis-Astragalus adsurgens(M3),Platycladus orientalis-Melilvtus suaveolens(M3) and Platycladus orientalis-Medicago sativa(M3),the utilization efficiency of solar energy was increased by 49.1%(2002),66.0%(2003);66.2%,85.1% and 76.6%,97.2% respectively.The efficiency of thermal resource was increased by 73.4%(2002),66.2%(2003);94.8%,85.1% and 97.6%,85.8% respectively.The precipitation use efficiency was increased by 79.3%(2002),81.2%(2003);116.9%,100.4% and 77.3%,64.0% respectively.And comprehensive using efficiency of the climate resource was increased by 70.6%(2002),81.3%(2003);104.7%,100.5% and 71.7%,69.2% respectively.The climate resource time efficiency(TE) of M2 and M3 was slightly lower than the control,but that of M3 was higher than the control.The TE of M1 during the growing stage in 2002 and 2003 was increased by 16.1% and 16.7%,compared with the control model.

Key words: Leguminous grass, Leguminous grass, Climatic ecology, Loess hilly and gully region, Returning farmland to forest, Climate resource use efficiency