Responses Of Soil Respiration And Hydrolase Activities Of Plant Communities To Simulated Precipitation And Plant Diversity

Global climate change affects the cycling process of carbon,nitrogen,phosphorus,and other elements in grassland ecosystems.Soil enzyme is the biocatalyst that controls the process and rate of nutrient cycling in the ecosystem,and it is essential for soil microbial community and plant nutrient supply.Although a large number of studies have pointed out that precipitation patterns and plant diversity change are key factors in the global change that affect the element cycle in the grassland ecosystem.However,the responses and mechanism of soil respiration and soil enzyme activity to the change in precipitation pattern and plant diversity,as well as the interaction between them,are not clear yet.In this study,the plant communities that have been constructed by six common perennial plants in the Songnen grassland,including Leymus chinensis,Lespedeza daurica,Vicia amoena,Gramineae hierochloeglabra,Carex duriuscula,and Kalimeris integrtifolia,were selected as the research objects.The responses of soil respiration and soil hydrolase activity to the changes of precipitation gradient,plant diversity gradient,and their interactions were studied by simulating the different graduates of the precipitation and plant diversity.During the experiment,the gradient of precipitation treatment are:WO(the average natural precipitation in 20 years),W1(the natural precipitation decreased by 30%),W2(the natural precipitation increased by 30%).The gradient of plant diversity is:no plant,1 species plant(Leymus chinensis),3 species plants(Leymus chinensis,Lespedeza daurica,Vicia amoena),6 species plants(Leymus chinensis,Lespedeza daurica,Vicia amoena,Gramineae hierochloeglabra,Carex duriuscula,Kalimeris integrtifolia).Soil respiration and the activities of seven hydrolases in soil,including ?-1,4-glucosidase(?G),?-1,4-glucosidase(?G),?-1,4-xylosidase(?X),Cellobiohydrolase(CBH),L-leucine aminopeptidase(LAP),?-1,4-N-acetylglucosaminidase(NAG)acid Phosphatase(?P)were detected.Meanwhile,the physical and chemical characteristics of soil and the quantitative characteristics of plant community were measured.The following questions are going to be answered:(1)What affects the precipitation and plant diversity and their interaction on soil respiration and soil enzyme activity?(2)What are the effects of precipitation,plant diversity and their interaction on soil physical and chemical characteristics?(3)What are the key factors which influence soil respiration and enzyme activity of plant communities?(4)What is the relationship between soil respiration and hydrolase activity in soil?After a two-years experiment,the main conclusions are as follows:(1)The increasing precipitation treatment had the trend of increasing soil respiration rate,but it was significantly higher than the average precipitation and reducing precipitation treatment under only one plant condition(P<0.05).High plant diversity resulted in high soil respiration rate.However,the interaction of plant diversity and precipitation had no significant effect on soil respiration rate.(2)The effects of plant diversity on the activities of seven soil hydrolases were all highly significant(P<0.01),but the responses of different kinds of enzyme activities to plant diversity were different.In addition to LAP,the effect of precipitation treatment on the activity of other six enzymes was significant(P<0.05)or extremely significant(P<0.01).Among them,the activities of ?G,?G,?X and NAG were inhibited by precipitation increasing treatment.The interaction of plant diversity and precipitation treatment had significant(P<0.05)or extremely significant(P<0.01)effects on the activities of ?G,?X,?P and CBH.Therefore,the activities of soil hydrolase were generally sensitive to plant diversity and precipitation graduates,and the interaction between high plant diversity and precipitation treatment had a greater impact on the activities of soil hydrolase.(3)The effects of plant diversity treatment on soil temperature,soil moisture,pH,TN,AN,AP and MBC were all extremely significant(P<0.01),while the effects of high plant diversity treatment(6 species plant)on EC,TN and MBC decreased.And the effect of precipitation treatment on EC,TC and MBC was significant(P<0.05)or extremely significant(P<0.01).The interaction of plant diversity and precipitation had extremely significant(P<0.01)effect on pH and TN.(4)The results of multiple stepwise regression analysis showed that AN was the key factor which affects soil respiration,so does MBC affects the changes of ?G,?X,NAG activity;TN and EC were the main factor that affects the changes of LAP activity.Moreover,?P was the key enzyme that affects soil respiration rate among the seven hydrolases.In conclusion,simulated graduates in precipitation,plant diversity and their interaction have different effects on soil respiration,soil hydrolase activity and soil physical and chemical characteristics.Overall,increasing precipitation treatment has the trend of increasing soil respiration rate,high plant diversity supports higher soil respiration rate,and soil hydrolase activity is sensitive to plant diversity treatment and precipitation treatment.In addition,the response of different enzyme activities,soil physical and chemical parameters to the interaction between plant diversity and precipitation is more complex,which implies the necessity of paying attention to multi-factor interaction in the study of global change.This study provides the experimental evidence of the impact of plant diversity and graduates in precipitation on soil respiration and enzyme activity,which has important reference value for predicting the response trend and mechanism of grassland ecosystem to global precipitation and plant diversity change in the future.