Differential response of radial growth and δ^(13)C in Qinghai spruce(Picea crassifolia) to climate change on the southern and northern slopes of the Qilian Mountains in Northwest China

Tree radial growth can have significantly differ-ent responses to climate change depending on the environ-ment.To elucidate the effects of climate on radial growth and stable carbon isotope(δ^(13)C)fractionation of Qing-hai spruce(Picea crassifolia),a widely distributed native conifer in northwestern China in different environments,we developed chronologies for tree-ring widths and δ^(13)C in trees on the southern and northern slopes of the Qilian Mountains,and analysed the relationship between these tree-ring variables and major climatic factors.Tree-ring widths were strongly influenced by climatic factors early in the growing season,and the radial growth in trees on the northern slopes was more sensitive to climate than in trees on the southern.Tree-ring δ^(13)C was more sensitive to climate than radial growth.δ^(13)C fractionation was mainly influenced by summer temperature and precipitation early in the growing season.Stomatal conductance more strongly limited stable carbon isotope fractionation in tree rings than photosynthetic rate did.The response between tree rings and climate in mountains gradually weakened as climate warmed.Changes in radial growth and stable carbon isotope fractionation of P.crassifolia in response to climate in the Qilian Mountains may be further complicated by continued climate change.

Comparison and analysis of three estimation methods for soil carbon sequestration potential in the Ebinur Lake Wetland,China

Based on soil under seven vegetation types,the carbon sequestration potential in the Ebinur Lake wetland was estimated using the maximum value method,the saturation value method,and the classification and grading method.Results indicated that:1)Soil carbon sequestration results for the top 20 cm soil layer were about 1.88 Mt using the maximum value method;the middle level standard of the classification and grading method result was 1.71 Mt.2)Soil carbon sequestration potential in the top 20 cm layer under different vegetation types,evaluated using the saturation value method and the classificationgrading method,ranged from 0.45 to 0.67 Mt,accounting for about 5/16 of the ideal carbon sequestration potential.3)Carbon sequestration potential calculated using the saturation method and the classification method(middle level standard),combining the soil organic carbon increment under different vegetation types in Ebinur Lake wetland,recorded an average growth rate of soil organic carbon around 0.7-1 kg/(hm^2·a).Time required to reach its carbon sequestration potential was 41 to 144 a.These results indicate that soil organic carbon content dynamically changes,and different forms of land use affect soil organic carbon content.The potential and ability of soil carbon sequestration and its mechanism of dynamic change are investigated,providing a scientific basis for understanding regional carbon cycle and climate change in wetlands.