| Wetlands,as one of the three major ecosystems in the world,account for only about 4% to6% of the global total land area,but store more than 30% of the global carbon.They are one of the largest carbon pools in the world and play an important role in the global carbon cycle.Inland saline-alkali wetland is a relatively special type of wetland,which has both the commonalities of wetlands and its own unique attributes.Therefore,in order to provide theoretical basis for the study of carbon biogeochemical cycles in inland saline-alkali wetlands,and also provide scientific basis for the rational utilization and scientific restoration of soda saline-alkali wetland,We conducted our research in the spring and summer of 2021-2022 at the National Wetland Park,Niuxin Taobao Inland Saline Alkali Wetland,Da’an City,JilinTwo areas were set up for the experiment,namely alkali spot land improvement for rice planting and saline alkali reed wetland restoration and utilization.Among them,four sample plots were selected for the saline alkali reed wetland restoration and utilization area,namely alkali spot land(degraded wetland,A1),reed wetland restoration(A2),reed wetland restoration+fish and crab aquaculture A(10 years of use,A3),and reed wetland restoration+fish and crab aquaculture B(5 years of use,A4);A total of four sample plots(B4)were selected from the degraded wetland improvement rice planting area,including alkali spotted land(degraded wetland,B1),paddy field(B2),paddy field crab farming(B3),and paddy field+organic fertilizer application.The soil SOC(organic carbon)content,DOC(soluble organic carbon)content,EOC(readily oxidizable organic carbon)content and stable carbon content in the soil layer(0-60cm)of the sample plot were measured,and the soil CPMI index(carbon pool management index)was calculated.The main research findings are as follows:1.1.1.Restoration and utilization of saline alkali reed wetlands:(1)A2,A3,and A4 have a certain promoting effect on reducing the p H and EC values of alkali spotted soil.The soil N content in A2 was significantly higher in all profiles than in the other three plots(p<0.05),indicating that restoration measures can effectively improve soil N content;There was no significant difference in P content among the four plots,while the S content of A1 soil was significantly higher than that of other plots.(2)The content of SOC and DOC in A2 soil is the highest,and the difference in EOC content among the four sample areas is relatively small.The EOC content shows a "wave" pattern of first decreasing,then increasing,and then decreasing with the increase of soil depth,which may be related to the growth and distribution of plant roots in the sample area;The stable carbon content of A2 in the 0-30 cm soil layer was significantly higher than that in the alkali patch soil P.(3)According to the four organic carbon components,the content of each organic carbon component in A2 soil is significantly higher than that in the other three sample areas,which indicates that the restoration measures in A2 have a significant role in improving the soil in alkaline patches.Due to the reed harvesting,the Total organic carbon reserves of A3 and A4 in the 0-60 cm soil layer are less different from A1.(4)Both A2 and A3 can significantly increase soil CPMI,but their pathways are not the same.A2 increases the CPMI index by increasing soil organic carbon content,while A3 increases the CPMI index by increasing soil activity.(5)There is a positive correlation between soil CPMI and EOC at the p<0.001 level,indicating that the soil in the experimental area mainly affects the carbon pool management index through changes in EOC content;There is a positive correlation between soil steady-state carbon and SOC at the p<0.001 level.Increasing soil SOC content has a certain promoting effect on improving soil stability in the sample area.At the same time,soil SOC and DOC have a positive correlation at the p<0.001 level and a positive correlation with N at the p<0.05 level.There is a positive correlation between S and EC at the p<0.001 level,which may be related to the formation of a large number of disulfide bonds in Suaeda salsa to adapt to saline alkali environments.2.Improving rice cultivation through degraded wetlands:(1)B2,B3,and B4 alkaline spot land utilization methods have a certain promoting effect on reducing the p H value of surface soil,among which B3 treatment has the most significant reduction in soil p H value;The three utilization methods of alkali spot land can significantly reduce the EC value of 0-20 cm soil layer(p<0.05),indicating that the three utilization methods have a significant promoting effect on reducing soil salinity and alkalinity.The three utilization methods of alkali spot land are all beneficial for increasing the N content of deep soil,but have little impact on the P content of soil.The S content of alkali spot land is significantly higher than the other three sample plots.(2)The utilization methods of B2,B3,and B4 for alkali spot land all have a positive effect on improving the soil SOC content of alkali spot land.Among them,the increase in SOC content in each soil layer of B4 is the most significant,while the increase in B2 treatment is relatively small;The three utilization methods of alkali spot land did not significantly increase soil DOC content;B4 treatment can effectively increase the EOC content of 20-40 cm soil layer;Three types of alkaline spot land utilization methods can all increase the soil steady-state carbon content,among which B3 and B4 treatments have a significant promoting effect on increasing the soil steady-state carbon in the 0-30 cm soil layer,while B2 treatment has a promoting effect on the soil 30-60 cm soil layer.(3)B2,B3 and B4 alkali patch land utilization can effectively increase the organic carbon storage and stable carbon storage of 0-60 cm,of which A4 has the most significant increase;The DOC carbon storage of the three types of alkali patch land utilization decreased in varying degrees compared with that of the alkali patch land;The soil readily oxidized organic carbon storage of A3 and A4 were higher than that of B1.(4)The utilization methods of B2,B3,and B4 alkaline patches can all improve soil CPMI.Among them,salt B4 treatment has relatively high CPMI values in all soil layers,so B4 treatment measures have a significant promoting effect on improving overall soil quality.Overall,B4 treatment mainly improves soil CPMI by increasing CPI,while B2 and B3 mainly affect soil CPMI through two pathways,CPI and CPA,relative to alkaline patches.(5)There is a positive correlation between soil CPMI and EOC at the p<0.001 level,indicating that the soil in the experimental area mainly affects the carbon pool management index through changes in EOC content;There is a positive correlation between soil steady-state carbon and SOC at the p<0.001 level,while there is a positive correlation between EOC and DOC at the p<0.05 level;There is a significant negative correlation between soil N content and p H(p<0.01),while there is a significant positive correlation with Eh(p<0.05).There is a positive correlation between S and EC at the p<0.001 level. |
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