Soil Respiration Characteristics Of Different Land Use Patterns In The Loess Plateau During The Past 30 Years

Soil is an important source of greenhouse gases?such as CO₂,CH₄ and N₂O?.Soil respiration is the largest carbon source for soil carbon storage to release CO₂ into the atmosphere.Therefore,studying soil respiration is essential for CO₂ emission reduction and exchange.In this study,loess tableland was used as the research object,and soil respiration was calculated.The topography?DEM,slope,aspect?,meteorological factors?temperature,precipitation?,soil organic carbon density,land use type,the relationship between soil type and soil respiration.Mainly got the following conclusions:?1?Soil respiration increases year by year.From 1985 to 2006,the increase of soil respiration in Baojitai District was larger,and the soil respiration area of other Taiwanese carp decreased greatly.The spatial distribution of soil respiration in 2006-2015 was just the opposite of 1985-2006.In the past 30 years,soil respiration in most areas has increased significantly over time.?2?In terms of spatial distribution,the temperature in 1985,2006 and 2015 increased gradually from north to south in space,while the spatial distribution pattern of precipitation is more distinct.The precipitation trends in 1985 and 2015 are the same,but different from 2006;in the past 30 years,the temperature in the Loess Plateau increased continuously,and the increase of soil respiration increased first and then decreased.Soil respiration and precipitation showed a linear growth relationship.?3?Compared with the soil type,the bauxite area is the largest,and the average soil respiration is 82.13 g C/?m²·month?,followed by the yellow loess soil?average soil respiration is 79.92 g C/?m²·month??,and the saline soil area is the smallest?average soil respiration was 77.84 g C/?m²·month??.The average respiration of different soil types in 1985,2000 and 2015 was 71.90,82.76 and 93.86 g C/?m²·month?,respectively.?4?In the past 30 years,in several major land types,the types of land use are different,and the changes in soil respiration are also different.From 1985 to 2006,the increase rate of soil respiration per unit area of forest land was 16.45%,the increase rate of grassland was 14.67%,the increase rate of cultivated land was 14.22%,and the increase rate of garden land was 14.24%.In 2006-2015,the increase of cultivated land was 15.67%,the increase of garden land was 15.58%,the increase of grassland was 12.90%,and the increase of forest land was 12.37%.The land use patterns are different,and the changes in total soil respiration vary.The total soil respiration of grassland decreased gradually.In 2006,it decreased by 0.34×10³?g C·km²/?month??,which was 2.67%.In 2015,it decreased by 0.49×10³?g C·km²/?month?.?,the decrease is 4.00%;the total soil respiration of cultivated land is gradually increasing.In 2006,it increased by 11.64×10³?g C·km²/?month??,the increase rate was 17.12%,and the increase in 2015 was 6.47×10³ compared with 2006.?g C·km²/?month??,the increase rate was 8.12%;the total soil respiration of forest land increased gradually.In 2006,it increased by 0.95×10³?g C·km²/?month??in 1985,an increase of 105.80%,2015 Compared with 2006,it increased by 7.05×10³?g C·km²/?month??,with an increase of 379.75%.The total soil respiration of gardens increased first and then decreased.In 2006,it increased by 0.17×10³?g C·km²/?month?compared with 1985.?),the increase rate is 25.24%,which was 0.22×10³?g C·km²/?month??in 2015,a decrease of 24.93%.?5?In the past 30 years,soil respiration has gradually increased,and it is mainly concentrated in the slope of 2⁶°.The area of loess platform slope <2° accounted for 24.37% of the total area,the soil respiration average was 81.49 g C /?m²·month?;the slope area of 2⁶° accounted for 43.24%,and the soil respiration average was 81.16 g C /?m²·month?;the area of slope with 6¹5° is 23.70%,the average soil respiration is 80.90 g C /?m²·month?;the area of slope with 15²5° is 6.51%,the average value of soil respiration It is 80.85 g C /?m²·month?;the area of slope >25° is 2.18%,and the average soil respiration is 81.31 g C /?m²·month?.Soil respiration content is different in different slope directions.In the past 30 years,the soil respiration on the shady slope was 81.50 g C /?m²·month?,and the soil respiration on the semi-positive slope was 81.72 g C /?m²·month?.On the whole,the soil respiration content increased gradually,and both reached the maximum between the shady slope of 22.5°⁶7.5° and the semi-positive slope of 225°²70°?and the soil respiration value of the semi-sunny slope is always greater than the yin Slope soil respiration value?.?6?Correlation analysis of soil respiration and environmental factors showed that there were positive correlations between the six environmental factors and soil respiration.The absolute value of correlation was air temperature > soil organic carbon density > precipitation > soil type > land use > DEM.According to the path analysis,the soil organic carbon density affects soil respiration indirectly through temperature and precipitation.Principal component analysis showed that the contribution rate of temperature and precipitation to soil respiration was greater than 70%.