土地利用变化与土壤养分的变化——以河北省遵化县为例

Land use changes and soil nutrient changes:a case study in Zunhua County,Hebei Province

土地利用变化可以引起土壤养分的变化。以河北省遵化县为例 ,研究该县 1 980年到 1 999年土地利用变化及土壤养分的变化。结果表明 ,近 2 0 a来 ,旱地、草地、水田面积大幅度减少 ,林地和村镇用地大幅度增加。旱地转换为林地 ,土壤有机质提高了 2 1 % ,全氮提高了 1 0 % ,碱解氮提高了 65% ,速效磷提高了 1 7% ,速效钾提高了 1 7%。旱地转换为草地 ,土壤有机质提高 3 8% ,全氮提高了 3 7% ,碱解氮提高了 71 % ,速效磷提高了 2 % ,速效钾提高了 2 8%。退耕还林还草不仅改变了土地覆被 ,而且提高了土壤养分。

Land use Change is the results of interactions between physical factors and human activities.Land ues change may influence many natural phenomena and ecological processes,including soil nutrient and soil water change,runoff and soil erosion,biodiversity and biogeochemical cycle.Land use changes can results in land degradation,such as water and soil loss,land desertification.It also can control water and soil loss,land desertification,and improve soil quality.Since late 1970s,the new land policy “Household Responsibility System” was implemented in the Chinese countryside,which has advanced China's agriculture and led to great changes in land use structure.Land use change has resulted in some changes in soil nutrients.This paper took Zunhua County,a typical agricultural area in northern China as a case study to analyze the relationship between land use changes and soil nutrient changes.The objectives are (1)to identify land use change within two typical periods of 1980 and 1999.(2)to examine soil nutrient changes between 1980 and 1999,and (3)to analyze the relationships between land use changes and soil nutrient changes. Land use change from 1980 to 1999 shows:(1)the area of farmland,grassland and paddy field decreased by 40%～50%;(2)the areas of forest,residential land,and water field increased by over 60%;(3)unutilized land had been transformed to farmland,forest,and residential land.The results of a transition matrix reflected the area increase or decline of each land use type.Between 1980 and 1999,29%,10%,and 10% of cultivated farmland were converted to forest,residential land and grassland respectively.About 64% of grassland was transformed to forest.About 59% of unutilized land was transformed to grassland,and 31% was transformed to forest. The soil nutrient status of farmland in 1999 increased significantly( p <0.10%)compared to 1980.The increase in organic matter content was because of an increase in straw incorporation.The differences in organic matter content for forest between 1980 and 1999 were not statistically significant.Except for avaliable P, soil nutrient levels for grassland improved significantly between 1980 and 1999.Soil nutrient changes could be related to large changes from grassland to forest and from farmland to forest and grassland.The introduction of forest grassland may have reduced the loss of soil nutrients by erosion and leaching. Land use changes have resulted in soil nutrient changes in the study area.The soils under forest in 1999 transformed from farmland in 1980 increased in organic matter by 21%,total nitrogen by 18%,available nitrogen by 65%,avaliable phosphorus by 17% and available potassium by 17%.Similarly,in the area which was converted from farmland in 1980 to grassland in 1999,soil organic matter,total nitrogen,available nitrogen,available phosphorus,and available potassium increased by 38%,37%,71%,2%,28%,respectively.Changes from farmland to forest and grassland not only changed land cover but also improved soil fertility and probably reduced soil nutrient losses.