ABSTRACT
Cropland soil organic carbon density (SOCD) is an important indicator for measuring soil fertility and soil quality. To understand the spatial differentiation characteristics of cropland SOCD and its influencing factors across China, a dataset on the cropland SOCD of 19 typical stations during 2005-2015 was collected from the China Ecosystem Research Network. The geodetector method was used to analyze the influencing factors affecting the spatial patterns of cropland SOCD. The results indicated that the mean cropland SOCD ranged from 0.83 kg·m-2 to 4.97 kg·m-2 in different stations across China, and was higher in humid monsoon regions than in arid and semi-arid regions. Under different land use patterns, the SOCD of paddy fields was higher than that of other croplands and showed a tendency of significant increase from 2005 to 2015, reaching 0.13 kg·(m2·a)-1. The soil physical and chemical properties and precipitation were important influencing factors that affected the spatial patterns of cropland SOCD. In particular, the soil alkaline nitrogen content had the greatest impact on the cropland SOCD patterns. Furthermore, the interaction forces between the soil alkaline nitrogen content and latitude, soil type, precipitation, and soil pH were clearly strengthened. The findings can provide an important scientific basis for reducing cropland greenhouse gas emissions and increasing soil carbon sequestration across China.
ABSTRACT
Based on the MODIS/MOD11A2 data from 2001 to 2013, this paper researched the characteristics of land surface temperature (LST) of Tianshan Mountains area. The results indicated that the average of LST in the study area was 1.73 °C , and LST was much higher in the east than in the west. The inter-annual variation range of LST in the northwest was significantly large than in other regions, with the largest above 0.55 °C in some areas. The LST tended to slowly increase with time, and the increase rate was 0.147 °C . a-1. It showed a significant seasonal difference, and the fluctuation of winter was significantly larger than in other seasons with the coefficient of variation reaching 12.7%. The LST difference of day time was greater than that at night, and that in summer was greater than in other seasons. The LST differed with land use types, and the fitted results were inconsistent between the LST and NDVI. With the increase of NDVI of woodland and grassland, the LST decreased dramatically. The LST of construction land and cropland under the influence of human activities had higher sensitivity with NDVI than other land types.
