Carbon Questration Of Saline Farmland And Their Response To Climate Change In The Eastern Helan Mountains

In order to cope with global changes,more and more countries have incorporated carbon peaking and carbon neutrality into their national development strategies.Saline soils in the northwest of China have a large distribution area,which restricts the development of agriculture.Studies have shown that there may be a large potential for carbon sequestration in arid areas,so it is important to study how to restore the productivity of saline soils and enhance the carbon sink of arid ecosystems.To clarify the carbon "source/sink" effect of agricultural soils in China under future climate change is the basis for rational carbon neutral policy formulation.Based on this paper,an experimental study on the physiological and ecological conditions of farmland soils and maize was conducted from 2017 to 2021 at the experimental site of Zhenbeibao in the eastern foothills of the Helan Mountains in Ningxia,and the main findings of the study are as follows:(1)Soil organic carbon was significantly positively correlated(P<0.01)with soil porosity,soil total nitrogen,soil total phosphorus,soil alkaline nitrogen,soil fast-acting phosphorus and soil fast-acting potassium,and negatively correlated(P<0.01)with soil bulk weight.The strength of the relationship between soil physical and chemical properties and soil organic carbon was as follows:soil total nitrogen>capacity=soil porosity>soil total phosphorus>soil alkaline soluble nitrogen>soil fast-acting phosphorus>soil fast-acting potassium;as the content of soil organic carbon increased,the content of soil nutrients also increased.(2)The spatial distribution of SOC was higher in the center areas and lower in the surrounding areas;whereas the spatial distribution patterns of total salt,Ca2+,Mg2+,Na+,SO42-,Cl-were similar,that is,they were symmetrically distributed along the center of the experimental area,and the high value area was roughly distributed on both sides of the north-south diagonal.The soil pH was distributed in strips,with a distribution characterized by a high center and low surrounding areas.With the increase of SOC content,the contents of soil total salt,soil pH,Ca2+,K+,Mg2+,Na+,Cl-,SO42-,CO32-,and Clshowed a trend of fluctuating increase and then decrease.When the SOC content was greater than 7.00 g·kg-1,it was beneficial to improve the soil salinization problem.(3)SOC content was at a more lacking level,and ΔSOC was increasing in most of the area of the test area,and the central part was the high value area of ΔSOC increase;SOCD showed a trend of more north and less south in 2017 and 2021,and the distribution of more SOC appeared to shift north.Soil carbon sequestration rate basically showed an increasing trend,and the increase in the low value area of SOCD was obvious than the high value area;SOC storage showed a trend of increasing,then decreasing and then increasing with the increase of years,and the overall trend of fluctuating increase;soil carbon pool in the experimental area in the past five years was changing between "carbon source" and "carbon sink" In the past five years,the soil carbon pool in the experimental area alternated between "carbon source" and "carbon sink";the carbon content and carbon storage in the above-ground part were higher than those in the below-ground part;the average annual carbon storage was 2.30×107 kg,and the average carbon density of maize was 0.98 kg·m-2;maize in this area has a high carbon sequestration potential.There may be a trend of organic carbon transfer from soil to crop in agricultural fields.(4)From 2022 to 2051,the farmland ecosystem in the eastern part of Helan Mountains is in a state of "carbon sink".Soil carbon sequestration rate tends to increase and then decrease with increasing temperature in the single climate factor;soil carbon sequestration rate increases when rainfall increases or decreases by 15%;the effect of temperature on soil carbon sequestration is greater than that of rainfall in the single climate change and interaction mode.The effect of increasing rainfall on soil carbon sequestration was greater than that of decreasing rainfall.Soil organic carbon loss was greatest when precipitation and temperature increased simultaneously.Therefore,appropriate changes in temperature(0.5℃ warming)and precipitation(15%reduction)can help promote the "carbon sink"effect of soils in the test area.Soils in the eastern part of Helan Mountains showed the "carbon sink"effect under all climate change models,and the Helan Mountains farmland ecosystem has a large carbon sequestration potential.