Dissimilation of soil humus in forest with pure stands and its relationship with other bio-chemical properties in the semi-arid windy region of the Loess Plateau, China

Dissimilation of soil humus in 7 typical forests with pure stands in the semiarid windy region of the Loess Plateau in China was investigated. In addition, its relationships with other bio-chemical characteristics were assessed by canonical correlation analysis. The results was as follows: (1) Pinus tabuliformis Carrière forest had the lowest humus content and the worst stability among 7 forests with pure stands; Populus simonii Carrière forest had low humus content and worse stability; Robinia pseudoacacia L. forest had moderate humus content but the best stability; Salix matsudana Koidz. forest had moderate humus content and bad stability; Hippophae rhamnoides L. forest had high humus content and the best stability; Caragana microphylla Lam. forest had high humus content and moderate stability; Amorpha fruticosa L. forest had the highest humus content and benign stability; (2) Large microbial biomass and sufficient available P would accelerate the formation of humic acid and fulvic acid, respectively. High available N, P and Fe contents and high urease and protease activity were conducive to increase the humus stability. The particularity of community environment and litter properties of pure stands were identified as the key reasons for the humus dissimilation, thus mixed-reformation or establishing ground vegetation would be feasible ways to improve humus properties in forest with pure stands.