| The change of physicochemical properties of wetland soils can reflect the change of soil environment in wetland.By changing the habitats of animals and plants in wetlands,we can influence the changes of animals and plants,and ultimately lead to changes in the entire wetland ecosystem.This paper took the wetland soil of the abandoned farmland in Yunnan Dashanbao Grus Nigricollis National Nature Reserve as the research object,and selected 6 sample plots in the representative regional wetlands.In September of 2015,2016,and September 2017,soil samples at0 cm to 10 cm and 10 cm to 20 cm depths for each sample were collected,and index of physical property and chemical property,including the soil organic matter,NPK,available nitrogen phosphorus and potassium,ammonium nitrogen,nitrate nitrogen,soil natural water content,bulk density,particle composition,was also collected.These data gained was measured,based on the experiment.Below are results:(1)Soil Chemical Properties:The content of soil organic matter,total potassium,available phosphorus,and potassium increased with the increase of years of ecological restoration,and both two layers showed a gradually increasing trend.From2015 to 2017,the minimum content of organic matter increased by about 3 times;total potassium increased by about 3.5 times;available phosphorus increased by about 9 times;and available potassium increased by about 4 times,which was closely related to the restoration of vegetation in protected areas and the reduction of human factors.The content of the total nitrogen and nitrate nitrogen increased first and then decreased with the increase of years of ecological restoration.However,the difference between the upper and lower layers of ammonium nitrogen was more obvious,the surface layer increased year by year,and the subsurface layer stabilized for three years;The content of the total phosphorus showed a trend of decreasing first and then increasing,which may have something to do with the large-scale excavation of peat and drainage in the protected area history.(2)Comparison of Available Nutrients Between Dry Season(March)and Wet Season(September):All transects of the contents of alkali-hydrolyzed N and available P were significantly higher in the wet season(27.47-32.74 mg·kg-1)than that in the dry season(3.5-12.30 mg·kg-1)and the surface assembly both in dry and wet seasons were relatively obvious;While the content of the available potassium showed the opposite phenomenon,and that was,the content in wet season(58.00~124.29 mg·kg-1)was significantly smaller than that in the dry season(98.32~279.01 mg·kg-1).(3)Three-year Trend of Soil Stoichiometric Features:C:N and C:P tended to increase year by year,with the increase of years of ecological restoration.While N:P tended to increase first and then decrease.Compared with the mean value of Chinese wetland soils(18.22±7.51),C:N was lower than mean value of Chinese wetland(18.22±7.51)soil average in 2015(12.92±2.66),but in 2016(27.28±13.99),the annual average of 2017(36.62±8.91)is higher than the mean value of Chinese wetland soils.However,C:P(12.93±6.57)and N:P(0.41±0.38)were all far less than the mean value of soils in Chinese wetlands(245.22±227.52 and 13.60±16.81).All these data illustrated that the accumulation of C in the reserve was enough,but the accumulation of N and P was not.(4)Soil Physical Properties:With the increase of years of ecological restoration,the soil volume weight showed a trend of decreasing year-on-year,and among them,the volume weight of surface layer with a smaller reduction,reduced from 1.11g·cm~-33 in 2015 to 0.96 g·cm~-33 in 2017,indicating that the capability of preserving soil,water,and nutrient was enhanced;The three-year change trend of the natural moisture content in two layers showed an tendency of increase first and then decrease,from55.08%in 2015 to 71.07%in 2016,and finally to 64.43%in 2017.The bulk density slowly increased,the clay content slowly decreased,and these changes in vertical directions were not very obvious.(5)Correlation Analysis of Physicochemical Properties of soil:Organic matter had very significant positive correlation with quick-acting alkali-hydrolyzed nitrogen phosphorus and potassium,C/N,C/P;Total nitrogen had very significant positive correlation with nitrate nitrogen,available phosphorus and alkaline hydrolysis nitrogen;total phosphorus had very significant positive correlation with the clay content,C/N,C/P;total potassium had very significant positive correlation with organic matter,alkali-hydrolyzed nitrogen,and quick-acting phosphorus and potassium,C/N;available phosphorus had very significant positive correlation with C/N,C/P;clay content had very significant positive correlation with bulk density;N/P had very significant positive correlation with C/N,N/P;C/P had very significant positive correlation with bulk density N/P;alkaline nitrogen had very significant positive correlation with available phosphorus k and the clay content;available phosphorus had very significant positive correlation with available potassium(p<0.01).organic material had very negative correlation with total nitrogen,clay content and bulk density;bulk density had very negative correlation with natural water content,nitrate nitrogen,C/N and C/P;Ammonium nitrogen had very negative correlation with nitrate nitrogen(p<0.01).Available phosphorus had significant positive correlation with nitrate nitrogen(p<0.05).available potassium had negative correlation with bulk density and nitrate nitrogen;C/N,C/P had negative correlation with clay content and grit;total potassium,available phosphorus had negative correlation with clay content and bulk density;total phosphorus had negative correlation with C/N and C/P(p<0.05).(6)Soil comprehensive fertility level:the change trend of soil comprehensive fertility level under the scale of all kinds of land and big mountain bag is consistent,basically showing as follows:2015(23.87)<2016(30.42)<2017(39.82),fertility level increases year by year with the recovery years. |
PDF Full Text Request