Study On Decomposition Characteristics And Soil Enzyme Activity Of Litter In Gahai Degraded Swamp Meadow Wetland

Wetland litter is an important part of wetland ecosystem,which plays an important role in the nutrient cycle of wetland ecosystem.Litter decomposition is not only an important part of wetland ecosystem nutrient cycling,but also an extremely important part of the decomposition of carbon cycling,and it is connected with the organisms of photosynthesis,decomposition of organic matter and release of nutrient elements.Swamp meadow wetland is a typical wetland.In recent years,a serious of vegetation degradation and the decomposition process of litter arised from the unreasonable activities of swamp meadow wetland.Therefore swamp meadow wetland with different degrees of vegetation were selected to research the decomposition rate,the organic carbon,other nutrients content of litter and soil enzyme during different vegetation degradation process from May to September in2016,based on field sampling and laboratory analysis.The following conclusions are obtained:(1)The decomposition rate of litter decreased with vegetation degradation,and the difference was significant(p<0.01).According to the Olson model,the decomposition rate constants were obtained as follows: ungradation(0.0051)> lightly degradation(0.0047)> moderately degradation(0.0042)> severe degradation(0.0039).Residual rate of litter dry matter showed that ungradation<lightly degradation<moderately degradation<severe degradation,that is the faster the decomposition rate,the more the dry matter loss.(2)With the degree of degradation increased,carbon concentration of litter is significantly(p=0.006< 0.05,F=4.77);overall carbon concentration of litter decreased,the mean carbon concentration were 377.81±37.7 g/kg,314.36±32.62 g/kg,231.23±23.99 g/kg,243.11±22.7 g/kg,showed that ungradation>lightly degradation >moderately degradation > severe degradation.At the same degree of degradation,organic carbon concentration of litter was 30 d > 60 d > 90 d > 120 d.In general,litter carbon absolute content decreased with decomposition time increases,difference of carbon absolute content significantly(p<0.05,F=15.278);litter carbon absolute content also decreased with degradation,difference of carbon absolute content significantly(p=0.031<0.05,F=3.324),mean value of carbon absolute content was3.85±0.5g,3.22±0.39 g,2.74±0.26 g,2.31±0.25 g,showed ungradation > lightly degradation > moderately degradation > severe degradation.(3)The concentration of nitrogen in the litter of the swamp meadow wetland increased with the degree of degradation,and there was no significant difference(p>0.05,F=0.556).But with the longer decomposition time,there was significant difference change in the concentration of nitrogen litter(p=0.003<0.01,F=5.526).There was no significant difference in the absolute content of nitrogen in litter(p>0.05,F=0.516).There was a significant difference in the absolute content of nitrogen(p=0.011<0.05,F=4.155),with the increase of decomposition time.With the increase of decomposition time and the degree of degradation,the absolute content of nitrogen was 30 d>60 d >90 d >120 d.The absolute content of N element is 30 d > 60 d > 90 d > 120 d.(4)With the degree of degradation deepened and the decomposition time increased,the change of phosphorus concentration showed a decreasing trend and the change of phosphorus concentration in litter was significantly different(p<0.05,F=10.895;p<0.05,F=9.468).With the degree of degradation strengthened and the decomposition time increased,the change of the absolute content of phosphorus element showed a decreasing trend and the absolute content of the change was significantly different(p<0.05,F=16.601;p=0.004<0.05,F=5.196).(5)The litter decomposition rate was negatively correlated with litter organic carbon content and C: N,and the litter decomposition rate was positively correlated with total nitrogen content,total phosphorus content and C: P.The C: N of the four vegetation degradation stages decreased in different degrees,that is,the value of C: N was always 30 d > 60 d> 90 d > 120 d in the litter at the same degradation stage.With the degree of degradation intensified,C:N showed severe degradation > moderately degradation > lightly degradation > ungradation in general.The change of C: P also showed a decreasing trend and all reached the maximum at the beginning of decomposition.(6)Amylase and sucrase activity were weakened with the depth of soil layer.At the depth of the same soil layer,in the 0~10 cm,10~20cm,20~40 cm soil layers,the activity of amylase was decreased and the activity of invertase was fluctuated with the increase of litter decomposition time,and the change was significant(p<0.05).There was a significant positive correlation between soil amylase and sucrose activity,decomposition rate of litter,organic carbon content,total nitrogen and total phosphorus.That is,soil enzyme activity on the decomposition rate of litter,organic carbon and other nutrients play a catalytic role.