黄土丘陵区人工沙棘林水土保持作用机理及效益

Effects of artificial seabuckthorn forest on soil and water conservation in loess hilly region

沙棘是我国半干旱地区用于水土保持造林的主要生态 经济型树种,在“三北”地区生态环境建设中发挥重要作用.对野外试验资料分析表明,7～10龄沙棘林冠年平均截留率为8 5 % ,6～10龄沙棘林地枯落物层单次可截留0 89mm降水;沙棘林通过改善土壤理化性质,具有提高土壤入渗和抗冲性能作用,其中土壤中毛根数量是决定土壤抗冲能力的主要指标.沙棘林的水土保持作用随林龄变化明显,幼林(2～3龄)阶段的作用很小,降水特性是决定林地产流产沙量的主要因素;成林(4～5龄)阶段,产流产沙量受降水和林分生长的共同影响;成林后(6～12龄)阶段,降水特性的影响很小,林地产流产沙量维持相对稳定,年径流深与侵蚀模数分别为0 3～3 4mm、0～6 75t·km-2 .幼林至成林(2～5龄)阶段,径流含沙量急剧减少,成林后(6～12龄)阶段,径流含沙量趋于稳定,含沙量变化在0～5 0 9kg·m-3 .

Seabuckthorn is regarded as a main eco-economical tree species,and plays an increasing important role in eco-environmental construction in Northwest,Northeast and North China.Our study on artificial seabuckthorn forest in loess hilly region showed that the average rainfall interception rate of 7～10 ages seabuckthorn canopy was 8.5%,and the litter layer of 5～10 ages seabuckthorn forest could intercept 0.89 mm rainfall.Seabuckthorn forest could improve soil infiltration and anti-strike ability through improving soil physical and chemical properties,and the numbers of its hair roots and the depth of its litter layer were the main indices of soil anti-strike ability.The effects of seabuckthorn forest on soil and water conservation increased with its increasing age.In 2～3 ages stage,the effects were weak,and the runoff and sediment were mainly affected by the characters of rainfall.In 4～5 ages stage when the forest became maturing,the annual runoff depth and annual erosion modulus were 1.8～3.2 mm and 24.64 t·km~ -2,respectively.In 6～12 ages stage when the forest matured,the runoff and sediment on seabuckthorn woodland changed slowly,the annual runoff depth and annual erosion modulus being 0.3～3.4 mm and 0～6.75 t·km~ -2,respectively,and the characters of rainfall had much less effect on them.In the stage from young (2～5 ages) to mature forest,the sediment charge in runoff changed sharply,ranged from 77.31 kg·m~ -3 to 9.12 kg·m~ -3,but in 6～12 ages stage,the sediment content in runoff changed very slowly,and the range was 0～5.09 kg·m~ -3.