| According to the relevant theory of ecological stoichiometry,the soil of the karst rocky desertification ecosystem in Huajiang,Guanling – Zhenfeng was taken as the main research object by used the method of space instead of time,and were studied its ecological stoichiometry of C,N and P under different grades of rocky desertification(no rocky desertification,potential rocky desertification,mild rocky desertification,moderate rocky desertification,intensive rocky desertification),different seasons(autumn,spring)and different soil layers(0-5cm,5-10 cm,10-15cm).The spatial and temporal distribution characteristics of soil C,N and P ecological stoichiometry in karst rocky desertification ecosystem and the sources of overall spatial and temporal variability were analyzed.And combined with various ecological data statistics and analysis methods,the coupling relationship between the ecological stoichiometry characteristics of soil C,N and P in different soil layers and environmental factors was discussed.On this basis,combined with the ecological stoichiometry of plants,litter C,N and P of the study area,the correlation of stoichiometric characteristics among plant-litter-soil and their variation in different rocky desertification environments in the study area were discussed in order to further understood the nutrient cycle law and system stability mechanism among the various components of the fragile karst rocky desert ecosystem in southwest China and provided a scientific theoretical basis for soil and water conservation and vegetation restoration of karst rocky desertification ecosystem.The main results were as follows:(1)The spatial and temporal distribution characteristics of soil C,N and P contents and their stoichiometry in karst rocky desertification ecosystem.In different grades of rocky desertification environment,with the deepened of rock desertification succession,soil C and N content showed a trend of decreased first and then increased in different soil layers;Soil TP and C:N showed a trend of increased first and then reduced and then increased;soil C:P and N:P value mostly showed a trend of reduced first,then increased and then decreased.Except for P,C: P and N: P of some soil layers had significant spatial differences in different rocky desertification environments,most of soil stoichiometry indicators had no significant spatial differences in each rocky desertification environment.In different soil profiles,the contents of soil C and N were as follows: upper layer > middle layer >lower layer,and the surface aggregation effect was obvious.In different seasons,soil SOC,C:N,C:P values showed that spring > autumn;TP,TN,N:P values showed that autumn > spring.The soil C:N value has a small coefficient of variation in each soil layer in different seasons,and it was relatively stable.Affected by seasonal factors,the significant correlation indexes between soil nutrient indicators and stoichiometric were more in spring than in autumn.Sources of temporal and spatial variability of soil C,N,P and their stoichiometric ratios in karst rocky desertification ecosystem indicated that single temporal or spatial factor has a greater impact on soil C,N,P content and stoichiometric ratio in the study area,and the interaction among multiple temporal and spatial factors had smaller impact on them,and it was not significant.(2)The relationship between different environmental factors and the ecological stoichiometry of soil C,N and P in each soil layer.Several ecological statistical methods showed that the seven environmental factors had certain effects on soil nutrients and stoichiometric ratios in the study area,but the degree of impact was different.The intensity of human activity,land-use types,landform types and percentage of exposed rock had greater influence,while the influence of altitude,slope and aspect were weaker.Among them,human activity intensity,land-use types and landform types were the three most important environmental factors that affected soil nutrients and stoichiometric ratios in the study area.(3)The correlation of stoichiometric characteristics of plant-litter-soil continuum and its stoichiometric characteristics responded to the evolution of rocky desertification.There was a significant correlation among plants,litter and soil C,N and P in the rocky desertification ecosystem of the study area.Among the three components,the indicators of significant correlation between plants and litter were far more than that between plant and soil,litter and soil.The correlation between soil nutrient contents and stoichiometric ratios and plant and litter was not significant.In different grades of rocky desertification environment,the nutrient distribution patterns of the three components were plant> litter> soil,and the stoichiometric ratios showed litter>plant>soil.With the succession process of rocky desertification,the nutrient and stoichiometric ratios of plant-litter-soil continuum changed in varying degrees.The contents of C and N in soil were less affected by the habitat difference of different grades of rocky desertification,and the change range was smaller in the process of rocky desertification evolution.The P content of each component changed significantly under different rocky desertification environments.The stoichiometric ratios of plants and litter showed the similar change rules in the process of rock desertification succession,and they all decreased first,then increased and then decreased.Affected by its own nutrient contents,the soil C:N and N:P values have no significant spatial difference in different rocky desertification environments.The C: P value was only significantly different in the nil rocky desertification environment and the mild rocky desertification environment. |
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