Study On Spatial Heterogeneity Of Soil Particles Of 'Fertile Islands' Of Three Types Of Desert Vegetation In Xinjiang

Through a large number of field typical survey and sampling,in combination with geostatistics methods,fractal theory and GIS,soil particles characteristics of 'fertile island' of three types of typical desert vegetation(populus euphraticu,haloxylon ammodendron and tamarix) in Xinjiang were studied.Result shows:(1)For 'fertile island' of populus euphraticu,silt content were highest and sand content were higher than clay content in the different stages.The main soil particles were sand and clay.The bigger and smaller populus' sand and clay content were higher under the canopies than those in outside canopies,but silt content was less under the canopies than that outside the canopies.The moderate's sand content outside the canopies was higher than that under the canopies,but silt and clay content were higher under the canopies than that outside the canopies;For 'fertile island' of haloxylon,sand content were highest and silt content were higher than clay content in the different stages.The main soil particles are sand.Sand and silt content in the different stages and the moderate's clay in the root were higher than those in the canopies edge and those in the canopies edge were higher than those in outside canopies.The bigger and smaller haloxylon's clay content in the canopies edge was higher than that in outside canopies and clay content in outside canopies were higher than that in the root;For 'fertile island' of tamarix in Tahe,in the different growth stages,sand content was equal to silt content roughly and they were higher than clay content.In the soil,sand and silt are mainly.In the different growth stages,sand content were higher in the root and in the canopy edge than that in outside canopies.Silt content increased from the root to the canopies edge to outside canopies approximately.Except the smaller tamarix,clay content in outside canopies was higher than that in the root and in the canopies edge.For 'fertile island' of tamarix in Fukang,sand content were highest and silt content were higher than clay content in the different stages.Sand content were higher in the root than that in the canopy edge and in outside canopies.Silt content was higher in the canopy edge than that in the root and in outside canopies.Clay content in outside canopies was higher that in the root and in the canopy edge.(2)Using geostatistics methods and Kringing map,results shows:populus and tamarix's soil particles variation in Tahe and Fukang was caused by self-relation,but haloxylon' soil particles variation was caused by structural and random factors commonly.Three types of typical desert vegetation's sand,silt and clay content's spatial variation scale extended out of the canopies area and did not reflect shrub's partial effect.Kringing map showed that three types of typical desert vegetation's soil particles did not form apparent 'island' shape.(3)The spatial changes of soil particle size distribution and its fractal features as well as the characteristics of soil chemical properties were studied in the 'fertile island' of Populus euphratica and haloxylon Ammodendron.Results showed:for 'fertile island' of Populus euphratica,fractal dimension of soil particle under the canopies slightly smaller than that of outside canopies,this meant soil texture under the canopies was slightly coarser than that of outside canopies.For' fertile island' of haloxylon Ammodendron,fractal dimension of soil particle under the canopies bigger than that of outside canopies,this meant soil texture under the canopies was finer than that outer of coronal breadth.The distribution of soil fractal dimension was a significant negative correlation with sand content,and positive correlation with proportion content of silt and clay.So,soil fractal dimension can be considered to be one of quantitative indices for evaluating shrub 'fertile island'.But the correlation between the distribution of soil fractal dimension and organic matter,total salinity was not significant.