西藏人工造林作业区土壤养分特征研究

Characterization of Soil Nutrient Status of Areas to be Afforested in Tibet,China

为了掌握西藏拟造林作业区的土壤养分状况,对6个地市524个造林作业区的土壤样本进行了养分测定和分析。结果表明:(1)土壤全钾、有效磷、有机质和速效钾均处在"稍缺―极缺"水平:平均含量分别为6.26 g kg^(-1)、8.7 mg kg^(-1)、17.81 g kg^(-1)和83.6 mg kg^(-1),全氮和全磷处在"中等―稍缺"水平:平均含量分别为1.39 g kg^(-1)和0.72 g kg^(-1),碱解氮条件最好:平均含量为214.1 mg kg^(-1),全钾条件最差。(2)6地市除碱解氮外,土壤中分别存在2至5个养分元素的缺乏,多数作业区全钾、速效钾和有效磷不足。阿里地区最缺有机质,仅5.08 g kg^(-1),日喀则市、拉萨市和林芝市最缺全钾,仅5.19~6.42 g kg^(-1),山南市和昌都市最缺有效磷,仅3.9~5.4 mg kg^(-1)。此外,拉萨市、山南市和阿里地区多数作业区全氮不足,阿里地区、日喀则市和昌都市全磷不足,除昌都市外各地市有机质不足的作业区居多。(3)地市间土壤养分含量差异显著,但速效钾、有机质在日喀则市、拉萨市和山南市间差异均不显著。总体而言,西藏造林作业区土壤养分状况较差,通过对西藏造林作业区土壤养分的特征分析,可为作业区造林后树木生长状态的成因查寻提供科学依据,为进一步提高造林质量提供基础数据。

【Objective】This research aims to understand soil nutrient status of areas to be afforested in Tibet,China,so as to design optimal afforestation technologies.【Method】Soil samples were collected from 524 areas to be afforested in 6 regions of Tibet for analysis of eight soil nutrient elements.【Result】Results show that：（1）the soil samples were 6.26 g kg^（-1）,8.7 mg kg^（-1）,17.81 g kg^（-1） and 83.6 mg kg^（-1） in total potassium,available phosphorus,organic matter and available potassium,respectively,all falling into the level of＂Slightly^Extremely Deficient＂,and 1.39 g kg^（-1） and 0.72 g kg^（-1） in total nitrogen,and total phosphorus,both being sorted into the level of＂Moderate^Slightly Deficient＂,with alkaline nitrogen ranking on the top and being 214.1 mg kg^（-1） on average,and total potassium ranking in the bottom;（2）the soils in the six regions suffered deficiency in 2~5 of the nutrient elements,except for alkaline nitrogen;the soils in most of the afforesting areas were deficient in total potassium,readily available potassium,and available phosphorus;the soils in Ngari were extremely deficient in organic matter,being only 5.08 g kg^（-1）;the soils in Shigatse,Lhasa,Nyingchi were extremely deficient in total potassium,being only 5.19~6.42 g kg^（-1）;and the soils in Shannan and Qamdo were extremely deficient in available phosphorus,being only 3.9~5.4 mg kg^（-1）.Besides,the soils in Lhasa,Shannan and Ngari were insufficient in total nitrogen;the soils in Lhasa,Shannan and Ngari were insufficient in total phosphorus;and in all the regions,except for Qamdo,the soils in most afforesting areas were insufficient in organic matter;and（3）the soils varied sharply in soil nutrient content from region to region,but the soils in Shigatse,Lhasa and Shannan did not differ much in readily available potassium and organic matter.【Conclusion】The findings of this study demonstrate that the soils in most of the afforesting areas in Tibet are quite poor in soil nutrient status.Through characterizing the soil nutrient status in the afforesting areas in Tibet,the study may provide a scientific basis for investigation of factors affecting growth of the trees planted,and fundamental data,as well,for further improving quality of the afforestation.