Water-holding capacity of different forestlands 20 years after converted from farmland in loess region,western Shanxi Province.

To compare the water conservation capacity of four typical forest stands converted from farmland 20 years ago in loess region, western Shanxi Province, the maximum water-holding capacity (WCm) and effective water-holding capacity (WCe) of litter and soil layers in secondary forest (SF),Pinus tabuliformis plantation(P),Robinia pseudoacacia plantation (R) and P. tabuliformis × R. pseudoacacia plantation (P×R) were examined based on field investigations and laboratory analyses in July 2013,with the farmland as a control (CK). The results were as follows: 1) WCm and WCe of litter layer in secondary forest were 201.20 and 154.32 t/ha, respectively, which were 1.35-2.14 times and 1.33-2.06 times of those in the plantations. Both WCm and WCe showed the trend as P × R R P. 2) The WCe of the soil layer in four forest stands ranged between 5 102-5 563 t/ha, and the WCe was 1 007-1 251 t/ha, which were significantly higher than 4 695 and 812 t/ha of the farmland (CK), respectively. The WCe showed the trend as SF P × R P R, while WCm as SF P × R R P. 3) The WCe of the forestlands increased about 32.9%-73.1% and much higher than the WCm increment about 10.7%-22.8%, which was consistent with the changes of non-capillary porosity. This implied more significant effects of the conversion of farmland to forest (CFF) on WCethan WCm. 4) The water-holding capacity of the converted forestlands showed the trend as SF P × R R P with significantly higher WCmand WCe than the farmland. This was mainly resulted from the improvement of soil characteristics and then the increase of water-holding capacity in the soil, and also certain water-holding effect of litter layers. In general, the water-holding ability has been significantly improved through the CFF in loess area of western Shanxi Province. The water-holding capacity of the secondary forest was better than the other three plantations, indicating that the secondary forest should be the main type of vegetation restoration in CFF program in the loess region.