Spatial Distribution Characteristics Of Soil Chemical Properties In The Middle Reaches Of Heihe River

The ecological environment of wetland in Heihe reserve is deteriorating.According to the survey of Zhangye city forestry department.In recent years,the artificial forest of Heihe river is dying and the area is 17.66 thousand hm2,the desertification area increased by 60.04 thousand hm2,the total grassland coverage decreased about 25%-35%,the wetland area decreased more than 10.2 thousand hm2.It is difficult to bear the task of economy and ecology given by national rapidily development.The marsh wetland in Heihe are degrading.Three typical wetlands(riverine wetland,lake wetland and marsh wetland)in middle reach of heihe as research object.Heihe wetland,a nationl nature reserve in Zhangye,using field investigation,soil sample collection and laboratory analysis.Inspatial distributions instead of time succession,descriptive statistics and linear regression were adopted in vertical distribution of soil organic matter,available nitrogen,phosphorus and potassium.The results show that :(1)The variation degree of soil organic matter,available nitrogen,available phosphorus,available potassium and total salt content in Ganzhou marsh wetland were moderate variation(13.76 ~ 94.43%),the variation range of each index were large except p H.Variation tendency of soil organic matter content and available nitrogen content was same,their vertical differentiation were significant.With the increase of soil depth,the content of soil organic matter increased significantly,The distribution pattern is low content of upper layer and high content of lower layer.The distribution of phosphorus and potassium levels are consistent in horizontal distribution,content may vary with the terrain.At the same time,surface aggregation phenomenon was obviously showed.With the increase of soil depth,available phosphorus and available potassium content was significantly decreased.in all experimentation area,the vertical variation trend is similar.The spatial variability of p H value was not significant,but the self-correlation of p H was obvious.Most of the soil in the experimentation area was strongly alkaline,and the spatial distribution was affected by structural factors.The spatial variation of available P and available K,organic matter,p H,total salt and available potassium were significant.p H had a great influence on the absorption and transformation of soil organic matter and available nutrients.Significant correlation between organic matter and p H value was exist.Indicated water level of the wetland is decreasing,the aerobic microorganism has strong respiration and frequent activity at present stage.(2)The coefficient of variation range about 6 soil factors in Linze County river wetland was 3.88%-102.70%.The variation of organic matter,available nitrogen,available potassium and total salt content were moderate intensity variation,variation of p H is weak,variation of available phosphorus is strong,the content of each index varies greatly.The variation tendency of soil organic matter content in horizontal direction was decreased with the number of samples.The vertical differentiation was significant,with the increase of soil depth content of soil organic matter was significantly increased.Both in horizontal distribution and vertical distribution,the content of available nitrogen,available phosphorus and available potassium were consistent.The content of available nitrogen decreased sharply with the increase of soil depth.The distribution pattern is high content of upper layer and low content of lower layer.Content of available nutrients is likely to change with the topography,and surface aggregation phenomenon was obvious.With the increase of soil depth,the content of available nitrogen,phosphorus and potassium were significantly decreased.The vertical variation trendency is consistent in whole experimentation area.The spatial variability of p H was not significant,whereas,self-correlation of p H was obvious.There was no neutral sample and alkaline sample,salinization was serious in river wetland.Spatial distribution was affected by structural factors.There were significant positive correlation between soil available phosphorus and total salt content,available potassium content and salt content;available potassium content and available phosphorus content was also significantly related.In the middle layer,potassium content is significantly related to the total salt.(3)The variation of soil available nitrogen,phosphorus and potassium,high organic matter and total salt content in Gaotai lake wetland was moderate intensity variation(17.93-90.24%),the variation range of each index were large except p H,content of each index variation are large.In horizontal direction,the variation tendency of soil organic matter content decreased with the content of different sample.There was vertical differentiation of soil organic matter,which increased with soil depth.The content of available nitrogen,available phosphorus and available potassium were consistent both in horizontal distribution and vertical distribution.with the increase of soil depth,the content of nitrogen decreased sharply.The distribution pattern is high content of upper layer and low content of lower layer.Content of available nutrients is likely to change with the topography,and surface aggregation phenomenon was obvious.With the increase of soil depth,available nitrogen,available phosphorus,available potassium content was significantly decreased,vertical trendency is semilar in the experimentation area.p H value of spatial variation is not obvious,but p H value has obviously autocorrelation.75%of experimentation area was salinization serious,Distribution pattern of total salt content in the whole study was high content of upper layer and low content of lower layer.Soil organic matter and available nitrogen had significant negative correlation;total salt and p H in the middle and bottom layer are significantly negatively;available potassium and organic matter in the middle layer and the bottom layer has significant negative correlation;p H and available P had extremely significant negative correlation;the organic matter and p H value in the presence of significant the underlying.(4)Available nitrogen and organic matter of marsh wetland is accelerated under the influence of drought and high temperature.The spatial distribution in river wetland of available nutrients,organic matter,p H value and total salt content showed that the marsh wetland in Ganzhou area was in a weak stage.The spatial distribution of available nutrients,organic matter,p H value and total salt content showed that the growth and development of Linze river wetland were good.The spatial distribution in Lake wetland of soil available nutrients,organic matter,p H and total salt content showed that the growth and development of the Gaotai lake wetland were severe.