| Wetland ecosystems have a variety of ecological functions,which are closely linked to the survival and development of human beings.The unreasonable development and utilization by human beings could lead to degradation of wetland ecological function.How to protect and restore the degraded wetland ecological function is one of the hot spot of academic research.Taking the Dashanbao Black-necked Crane National Nature Reserve in Yunnan Province as study area,chose peat soil of the forbidden graze land,mild graze land,moderate graze land,severe graze land as the research object,and analyzed the connections between different graze intensity and soil ecological function of peat soil.The main contents and conclusions are as follows:1.Physical properties and water storage capacity of the peat soil.The average bulk density decreased with the decrease of graze intensity.From the cultivated land to the forbidden graze land,the average of soil's bulk density has decreased from1.11±0.03g/cm3 to 0.63±0.06g/cm3.In the vertical direction,with the depth increased,the soil's bulk density became larger,the average of bulk density from top to bottom were:0.756±0.05g/cm3,0.99±0.04g/cm3,1.11±0.08g/cm3;the average of total porosity increased with the graze intensity,from arable land to the forbidden graze land,increased from 23.85±1.85 % to 58.83±2.89 %,and the porosity decreased in the vertical direction.The average porosity was 31.33±1.23%,35.30±1.78 the water storage capacity increased from 238.5±18.5 t/hm2 to 588.3 ± 28.9t/hm2.Average unit area saturated water storage capacity has increased from 238.5±18.5t/hm2 to368.5±18.5t/hm2.2.Erosion resistance of surface peat soil.After returning farmland to wetland,the stability of soil water stable aggregates were improved,and the average weight diameter(EMWD)of water-stable aggregates in surface peat soil increased with the decrease of graze intensity,from 2.83 mm of cultivated land to 5.09 mm of forbidden graze land.With the reduction of grazing intensity,the ELT of surface peat soil weredecreased from 41.39% of the cultivated land to 14.78% of the forbidden graze land,which was 64.28% lower than that of the graze land.The structural grain index and the soil physical stability index of the surface peat soil has improved after returning farmland to wetland.With the decrease of graze intensity,the clay content increased,and the structural grain index under different graze intensity was increased from 0.114 to 0.505,increase of 342.98%.The soil physical stability index also increased with the decrease of farmland and graze intensity,from 11.494 in cultivated land to 89.205 in strict graze,increased of676.1%.3.Chemical properties of peat soil and carbon pool.After returning farmland,the pH value,organic matter and humic acid of peat soil were restored.The pH value of peat soil in returning farmland showed a decreasing trend with decreasing graze intensity: pH value decreased from 5.3 of cultivated land to ban 4.75 of the graze land,organic matter increased from 53.445g/kg to 440.183g/kg,humic acid increased from4.268% to 28.405%.It is shown that with the decrease of graze intensity,the fertility of peat soil in returning farmland has been greatly restored.After the conversion of cropland,the carbon stock index(CPI)and the carbon management index(CPMI)of peat soil increased with the decrease of graze intensity,showing an increasing trend,and the different tillage intensity was forbidden.Under mild,moderate and severe graze Soil(CPMI)compared with the farmland,the largest increase of 205.6%.After the conversion of cropland,the contents of total N decreased with the increase of graze intensity,and the content of available N was decreased,but the changes was not regular.After returned farmland to wetland,the content of phosphorus decreased,but with the decrease of graze intensity,rising trend.The highest prohibition of graze land was 19.32% and 291.61% higher than that of the lowest graze land respectively after returned farmland to wetland.The total potassium content of peat soil decreased after returning farmland,and the highest graze to198.08% higher than the lowest prohibited graze land.The highest graze land is523.5.4% higher than the lowest prohibited graze land.4.Correlation between chemical and chemical properties.The correlationbetween physical properties and chemical properties of peat is mainly related to the significant positive correlation between porosity and carbon,nitrogen and potassium,and the total porosity is related to organic carbon,total nitrogen and available nitrogen(p <0.05)(P <0.01),the correlation coefficient was-0.42,and the porosity was the main index to reflect the water retention capacity of peat soil.The correlation coefficient was 0.852,0.867 and 0.486,respectively,and there was a significant negative correlation with total potassium The correlation is focused on the pH,between humic acid and carbon,nitrogen,and potassium.5.The reduction of graze intensity can improve the physical and chemical properties of pet soil,improves its water conservation ability,improves soil's corrosion resistance and fertility.Therefore,it is important to reduce the graze intensity of wetland which was returned form farmland to improve the productivity and soil and water conservation capacity of wetland soil,enhance the peat's function such as "carbon sink" and "carbon sequestration" and promote the sustainable development of returning farmland wetland. |
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