Evaluation of litter and soil water-holding capacity of typical stand in Datong, Qinghai

Background  Since the implementation of the Grain for Green Program in Datong county of Qinghai province, the existing forest area has been growing steadily, but due to the single forest structure, poor stability and lack of tending and management, the ecological service functions such as water conservation and soil and water conservation in this region are weak. It is of great significance for rational management of plantation and improvement of water conservation function of forest ecosystem to understand and evaluate the water-holding capacity of each forest stand.

Methods  Six typical forest stand types of Populus cathayana, Betula platyphylla, Picea crassifolia, Larix principis-rupprechtii, Picea crassifolia & Betula platyphylla, Picea crassifolia & Larix principis-rupprechtii in Ta′ergou watershed of Datong county, Qinghai province were taken as the research objects. PCA (principal component analysis) was used to select the main influencing factors and construct the evaluation index system, and then fuzzy matter element method was applied to give objective weight. Finally, the water-holding capacity of 6 typical forest stand types in Ta′ergou watershed of Datong county was evaluated by comprehensive scoring method.

Results  The thickness and volume of litters in coniferous forests were the largest. The maximum water-holding capacity of litter ranged from 58.91-107.84 t/hm², and that of the P. crassifolia & L. principis-rupprechtii was the largest. The effective water-holding capacity of litter ranged from 31.74-60.14 t/hm². The P. crassifolia & B. platyphylla was the largest, and the maximum value was 1.89 times as much as the minimum value. 2) Soil physical properties were generally mixed conifer-broadleaf forest > broad-leaved forest > coniferous forest. The variation range of field water-holding capacity in 0-20 cm soil layer was 40.58-63.15 t/hm², and the P. crassifolia & B. platyphylla was the largest, which had significant difference with other stands (P < 0.05). 3) The weight value of soil layer accounted for 66%, which was higher than that of litter layer (34%). Soil layer was the main influence layer on water-holding capacity of forest land. 4) The water-holding capacity of each forest type was as follows: P. crassifolia & B. platyphylla > B. platyphylla > P. crassifolia > P. crassifolia & L. principis-rupprechtii > L. principis-rupprechtii > P. cathayana.

Conclusions  The P. crassifolia & B. platyphylla was the best stand of water conservation capacity in Datong county, Qinghai province. This study screened out the best stand type and obtained the mechanism of the difference of stand water holding function, which provided a theoretical basis for the near-natural management of plantations in the eastern part of Qilian Mountains.