Spatial Variation Characteristics of Soil Nutrients in Shrub-grass Econtone in the Lower Lhasa River Basin

PANG Li; QU Xingle; YIN Wenjie; FANG Jiangping; LUO Daqing

doi:10.15933/j.cnki.1004-3268.2015.04.017

Abstract：The ecotone of shrub and herbaceous plant in the subalpine zone of semi-arid region of the downstream of Lhasa River was used as the survey region,and the nutrient contents of the soil collected from the shrub, shrub-grass and grass land in both the southern and the northern slopes. The results showed that the pH value of the soil was between 6. 6 and 8. 5,which was neutral and slightly alkaline and suitable for the growth of neutral and slightly alkaline plants,and the relations between the soil pH values of shrub land in the sourthern and northern slope,grass land in the sourthern slope and the soil depth could be fitted by the quadratic function. The soil organic content was between 15. 15 g / kg and 43. 74 g / kg,the order of average content of organic matters in the soil layer of 0—40 cm was grass land >shrub-grass land > shrub land in the southern slope and shrub-grass land > shrub land > grass land in the northern slope,and the relations between the soil organic content of shrubs and grass lands in the southern and northern slopes,shrub-grass land in the northern slope and the soil depth could be fitted by quadratic function. The total nitrogen content of soil was 0. 72—2. 15 g / kg,the orders of total nitrogen content in the southern slope and the northern slope were grass land > shrub-grass land > shrub land and shrub land >shrub-grass land > grass land respectively,and the total nitrogen content of shrub land in the southern and northern slopes,shrub-grass land in the southern slope,were apparently negatively correlated with the soil depth,the relations between them conformed to the quadratic function. However,there was no apparent correlation between total nitrogen content of grass land in the southern and northern slopes and the soil depth. The total phosphorus content of the soil was 0. 22—0. 54 g / kg,the orders of total phosphorus con-tents in the southern slope and northern slope were grass land = shrub-grass land > shrub land and shrub land > grass land > shrub-grass land respectively. The total phosphorus content of shrub-grass land had no apparent correlation with the soil depth in the southern slope,while which had apparently positive correla-tion with soil depth in the northern slope,and the relations between total phosphorus contents of shrub-grass land in the southern and northern slopes and the soil depth could be fitted by the quadratic func-tion. The total potassium content of soil was 2. 70—4. 59 g / kg,the orders of total potassium contents in the southern and northern slopes were grass land > shrub-grass land > shrub land and shrub-grass land >grass land > shrub land respectively. The total potassium contents of shrub,shrub-grass and grass lands had no apparent correlations with the soil depth in the southern and northern slopes. It was suitable to use the quadratic function to fit the relationship between total potassium contents of the shrub land in the southern and northern slopes and the soil depth. Generally,soil nutrient contents were apparent different between the southern slope and the northern slope; the contents of organic matters,total nitrogen,total phosphorous and total potassium of the shrub land and shrub-grass land in the southern slope were lower than that in the northern slope; with respect to the grass land,the contents of all nutrients except total phosphorous in the southern slope was higher than that in the northern slope.