Water-holding characteristics and accumulation amount of the litters under main forest types in Xinglong Mountain of Gansu, Northwest China

By the methods of field survey and laboratory soaking extraction, an investigation was conducted on the accumulation amount, water-holding capacity, water-holding rate, and water-absorption rate of the litters under six main forests (Picea wilsonii forest, P. wilsonii - Betula platyphlla forest, Populus davidiana - B. platyphlla forest, Cotonester multiglorus - Rosa xanthina shrubs, Pinus tabulaeformis forest, and Larix principis-rupprechtii forest) in Xinglong Mountain of Gansu. The accumulation amount of the litters under the forests was 13.40-46.32 t·hm-2, and in the order of P. tabulaeformis forest P. wilsonii - B. platyphlla forest L. principis-rupprechtii forest P. wilsonii forest C. multiglorus-R. xanthina shrubs P. davidiana - B. platyphlla forest. The litter storage of coniferous forests was greater than that of broadleaved forests, and the storage percentage of semi-decomposed litters was all higher than that of un-decomposed litters. The maximum water-holding rate of the litters was 185.5%-303.6%, being the highest for L. principis-rupprechtii forest and the lowest for P. tabulaeformis forest. The litters’ water-holding capacity changed logarithmically with their soaking time. For coniferous forests, un-decomposed litters had a lower water-holding rate than semi-decomposed litters; whereas for broadleaved forests, it was in adverse. The maximum water-holding capacity of the litters varied from 3.94 mm to 8.59 mm, and was in the order of P. tabulaeformis forest L. principis-rupprechtii forest P. wilsonii - B. platyphlla forest P. wilsonii forest C. multiglorus - R. xanthina shrubs P. davidiana - B. platyphlla forest. The litters’ water-holding capacity also changed logarithmically with immersing time, and the half-decomposed litters had a larger water-holding capacity than un-decomposed litters. The water-absorption rate of the litters presented a power function with immersing time. Within the first one hour of immersed in water, the water-absorption rate of the litters declined linearly; after the first one hour, the litters’ water-absorption rate became smaller, and changed slowly at different immersed stages. Semi-decomposed litters had a higher water-absorption rate than un-decomposed litters. The effective retaining amount (depth) of the litters was in the order of P. wilsonii - B. platyphlla forest (5.97 mm) P. tabulaeformis forest (5.59 mm) L. principis-rupprechtii forest (5.46 mm)P. wilsonii forest (4.30 mm) C. multiglorus - R. xanthina shrubs (3.03 mm)P. davidiana - B. platyphlla forest (2.13 mm).