金沙江干热河谷人工生态林的林分环境分析

 金沙江干热河谷尽管分布区域不大,但对金沙江流域的生态环境质量具有十分重要的影响,是金沙江水土保持生态环境建设的核心区。由于其异常干热的气候特点,使得人工生态林建设更为艰难。在干热河谷典型地段——元谋的试验观测表明:现有人工乔木生态林的林分微环境较差,赤桉林Fan林内光辐射仅比林外空旷地减小了20.7％;Fan的日平均气温（27.37℃）和地表土壤温度的日平均值（32.54℃）分别比林外只低0.14和3.31℃;林分F1、F2和F3春季0～100cm土层内平均含水率分别为6.84％、5.83％和9.16％,林分Fan也只有9.83％,相比之下,以扭黄茅群落为主的自然草坡这一季节的土壤水分则可高达13.20％。由此而导致林木生长缓慢,对于10年生赤桉林,F1的平均树高和平均胸径分别为9.46m和8.68cm;F3的平均树高只有7.22m,平均胸径更小（3.97cm）,表现出明显的生长不正常。高密度的人工乔木生态林在干热河谷地区不能形成合理的林分结构,低密度的稀树或零星分布的散生木生长良好。

Forest Environment of Artificial Eco-forest of Jinshajiang Dry-hot Volley

Although the range of distribution of Jinshajiang dry-hot volley is not universal, it has a very important influence on ecological environmental quality of Jinshajiang watersheds and is the key area in the construction of Jinshajiang e-cological environment. Due to the characteristics of extremely hot and dry climate, it is hard to build the artificial eco-forest. The environmental determination in the typical sector of dry-hot volley Yuanmou showed that the forest s micro-environment of the existing arboreous eco-forests was not good. The irradiation intensity, the daily average value of air-temperature (27.37℃) and the surface soil temperature (32.54℃) in forest F_an was only 20.7% , 0.14℃and 3.31℃ less than open field respectively. The average soil moisture of 0 - 100 cm soil layer in F₁, F₂ and F₃ in spring was 6.84%, 5.83% and 9.16%. It was only 9.83% in forest F_an also. The soil moisture of natural grass slop with Cheteropogoh cantortus community in this season was 13.20% in comparison with the artificial eucalyptus forest. As a result , the trees grew slowly. Take the ten-year-old forest (Form Eucalyptus camaldulensis) for example, the average tree height in the forest F₁ was 9.46 m and the average diameter at breast height 8.68 cm; on the contrary, the average height in the forest F₂ was only 7.22 m and average diameter was even smaller (3.97 cm) . The growth of trees in larger density forest wasn' t evidently normal. The optimum forest structure couldn' t be built in the high density artificial arboreous eco-forest in dry-hot volley area. The growth status of sparse trees and disperse trees was all right.