Figure 1.
Map of China (top) showing location of Henan Province and counties (bottom) within Henan Province used in this study.
Figure 2.
Average annual, maximum, and minimum temperature from 1971 to 2004 in Henan Province, China (A), and (B) average temperature and rainfall from 1975 to 2006 in different counties within Henan Province, China (B).
See Table 1 for key to county name abbreviations. All these counties were arranged in English alphabetical order.
Figure 3.
Wheat yield and total crop production (including wheat, maize, millet,) in Henan Province from 1978–2009 (A), and wheat yield and total crop production in different counties within Henan Province in 2009 (B).
See Table 1 for key to county name abbreviations.
Table 1.
Basic geographic coordinates for each county, along with climate data for 19 counties within Henan Province, China.
Table 2.
Spatial variation in soil (0–40 cm depth) properties, soil organic C (SOC), total soil N (TSN) concentration (g kg−1), and C/N in the 0–40 cm soil layer in 19 counties within Henan province, China.
Table 3.
Total C (TSOCS) and N (TSNS) stores in the surface soil layer (0–40 cm) of soils in 19 counties in Henan Province, China.
Figure 4.
Linear regression analysis of total crop production in each county (ton ha−1) with SOC and TSN (A) and with soil C and N store (0–40 cm) (B), and the total crop production of each county (10000 ton) with their soil C and N stock (C) (n = 19).
Figure 5.
Principle components analysis of environmental and soil variables for agricultural soils in 19 counties within Henan Province.
Length of arrows is directly proportional to their importance in explaining spatial patterns in the counties. Direction of the arrows indicates increasing values. Thus, the x-axis is primarily a gradient in soil C, whereas the y-axis is primarily a gradient in soil N and rainfall and secondarily a gradient in soil N. See Table 1 for key to county name abbreviations.