陕北黄土丘陵沟壑区人工刺槐林土壤养分背景和生产力关系研究

The Study on the Relation between Soil Nutrient and Productivity of Plantation Robinia pseudoacacia Forest in the Loess Plateau and Gully Area of Northern Shaanxi

通过对陕北黄土丘陵沟壑区半阴坡、半阳坡、阳坡11龄人工刺槐林土壤有机质、全氮、有效氮、速效磷、速效钾含量、土壤含水量和刺槐的株高、冠幅、胸径、新枝进行测定分析,结果表明:(1)该区土壤肥力水平偏低,有效养分缺乏。(2)整个生长季内,三个立地条件的土壤养分含量是:生长初期>生长中期>生长末期,说明林地自肥能力弱,地力在逐渐的衰退;(3)不同立地类型之间,土壤养分含量差异不显著,三个立地条件下的人工刺槐林土壤含水量差异显著,而三个立地条件下的刺槐生长量却有差异,因此认为,引起刺槐林生产力差异的主要原因是土壤含水量,土壤养分的缺乏,更加恶化了刺槐的生长条件。要想彻底改变刺槐生长“小老树”的局面,必须从根本上改变人工刺槐林的水肥条件;(4)三个立地条件之间,刺槐的生长量、土壤养分含量和土壤含水量大小均为:半阴坡>半阳坡>阳坡,所以,在建造人工刺槐林时,在半阴坡、半阳坡、阳坡三个立地类型之中,宜选择在立地条件好的半阴坡进行。基于上述分析,在陕北黄土丘陵沟壑区进行林草植被建设时,必须慎重考虑不同立地条件下的土壤水分生态环境和土壤养分背景。

Through the investigation and analysis about the contents of soil organic matter, total mtrogen, available nitrogen, available phosphorous, available potassium, plant height, crown width, breast diameter and new branch in the 11 years＇ plantation Robinia pseudoacacia forest in the loess plateau and gully area of northern Shaan Xi. The results showed that： （1） the soil fertility is inclined to low, and available nutrient is scarce in this area. （2） In the whole growth season, the contents of soil nutrient in the three different site conditions： growth initial stages 〉 growth metaphase 〉 growth telophase, which indicated by the consuming of the whole growth season, the nutrient of deadwood and defoliate etc. returned to the soil is few, the self-supply capacity of the forest land is weak, and the soil fertility is declining gradually. （3） In the experimental plots, among the different site types, the difference of the contents of soil nutrient is insignificant, but the growth quantity is significant. According to my survey data to analyze the soil water content in the plantation Robinia pseudoacacia forest in the site condition above mentioned, the difference of soil water content is significant, which the order from large to smallness： half shady slope 〉 half sunny slope 〉 sunny slope, therefore primary conclude, the main reason that arose the productivity difference of Robinia pseudoacacia forest is soil water content and the shortage of soil nutrient, which will deteriorate the growth condition of Robinia pseudoacacia. If we hope to change the “short-old tree” situation completely, we should radically improve the water and fertility condition of the plantation Robinia pseudoacacia forest. （4） Among the three site conditions, the order of Robinia pseudoacacia growth quantity, the soil nutrient content and water content： half shady slope 〉 half sunny slope 〉 sunny slope. Therefore, when we plant the plantation Robinia pseudoacacia forest, we should choose a better site condition, namely, the half shady slope to plant among the half shady slope, half sunny slope and sunny slope. According to the above-mentioned analysis, when we plant the forest grass vegetation in the loess hilly and gully area of northern Shaan Xi, we must consider cautiously the soil water and nutrient in different site conditions.