| In order to understand the site conditions of afforestation,identify the possible restrictive factors in the growth of forest trees,construct a site quality evaluation system for farmland shelter forests in the old course of the Yellow River in Jiangsu Province and provide basic theories for scientific construction of farmland shelterbelts,improvement of management efficiency of shelter forests,and upgrading of regional farmland shelterbelts.This paper,in the old course of the Yellow River in Funing County and Binhai County of Jiangsu Province,analyzed the topographical features by remote sensing technology,chosen 42 farmland shelterbelts and 15 non-forest plots as samples to investigate the soil characteristics,and used mathematical theories including multivariate statistical analysis,quantitative theory I,etc.,to carry out the study of site surveying,classification and quality evaluation of the old road of the Yellow River in Jiangsu Province.The results were as follows:(1)Analysis of Site ConditionsThe terrain of the study area was gentle,the soil texture was mainly silt soil,the soil compaction was high,and the soil pH appreciated as weakly alkaline or alkaline.The soil in the study area was non-saline soil determined by conductivity;according to relevant standards,the content of alkali nitrogen and effective P in soil in the study area was in a lack of level,and the available K content was relatively abundant.Soil bulk density,saturated water content,pH value,total nutrient,organic carbon,and effective P content had no significant difference in space,and exhibited low level variation in each distance interval;soil conductivity,mechanical composition,alkali-soluble nitrogen and quick-acting K were significantly different in space,and showed moderate or high level variation in each distance interval.The 500 m away from the old road of the Yellow River was a turning point of soil properties.(2)Site classificationSoil saturated water content,pH,conductivity,and total P were only significantly correlated with a small number of factors,and the factors such as total N,total K,alkali nitrogen,quick-acting K,elevation,slope,and river distance were closely related.Selecting 6 factors as dominant factors of site classification in the old road of the Yellow River,which were soil mechanical composition,total N content,saturated water content,electrical conductivity,total P content,and altitude.According to 6 dominant factors,42 farmland shelterbelts and 15 forestless land can be divided into 8 types of site types,and considering the geographical location and topographical features of the study area,this paper defined the study area as the main site type of the Yellow River,including two site type groups,in which the apex area of the alluvial fan contained three types of site types,alluvial fan slope areas contained 5 site types.(3)Site quality evaluationThe contribution rate of each factor to the site quality was as follows: soil texture>saturated water content>conductivity>volume weight>soil nutrient>altitude.Five different site index prediction equations with 2-6 factors were obtained,and the correlation coefficient was 0.623.0.743,0.861,0.877,0.916.According to the prediction equation,a five-level evaluation table for the quality of farmland protection forests in the old road of the Yellow River was compiled.The accuracy was determined by the number of evaluation factors.When using the 6-factor evaluation,the site quality classification was: 23.47~18.76(I),18.76~14.05(II),14.05~9.33(III),9.33~4.62(IV),4.62~0(V).Conducting site quality evaluation of no forest land in the study area,these area mainly got grade II and III.This evaluation system has good practical value. |
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