Climatic dependency of soil organic carbon isotopic composition along the S-N Transect from 34°N to 52°N in central-east Asia

We explored the relationships between surface-soil (1-20 cm) organic carbon isotopic signatures and associated climatic factors in central-east Asia in an attempt to develop transfer functions that can be used to retrieve the paleoclimatic information stored in the thick eolian-paleosol sequences within the area. Our analysis shows that the negative correlation between the surface-soil organic delta C-13 values and the mean annual precipitation is robust (R-2 =0.45: n =196; p < 0.05) and the negative correlation with the growing-season (April-September) precipitation is more significant (R-2 = 0.4966; n = 196; p < 0.05). Our study further shows that the positive correlation between the surface-soil organic delta C-13 values and mean growing-season aridity is most significant (R-2 = 0.5805; n = 196; p < 0.05). We have smoothed both the organic delta C-13 values and the mean growing-season aridity values using a 3-point moving-window average-filter method in an attempt to remove some of random errors and found that the positive correlation between the two is further increased (R-2 = 0.7784; n= 192- p<0.05). These robust linear relationships demonstrate their value in reconstructing paleoclimate changes in the study area. he documented climatic dependency of the surface-soil carbon isotopic composition in the study area might have resulted both from the humidity-related isotopic enrichment processes of the dominant C-3 plants (stomatal conductance and photosynthetic discrimination) and from the aridity-related abundance Of C-4 plants (mainly Chenopodiaceae species) along the S-N bioclimatic gradient. (c) 2007 Elsevier B.V. All rights reserved.