不同覆盖措施对土壤水分和当年造林成活率的影响

为了研究覆盖措施在干旱陡坡造林中对土壤水分蒸发量、土壤含水量及当年造林成活率的影响,并筛选出效果最佳的覆盖措施,在山西吉县蔡家川流域布设试验,分析了地表覆膜、地表覆草、土中覆草3种覆盖措施对土壤蒸发量、含水量、密度和孔隙度及当年造林成活率的影响。结果表明:造林初期连续蒸发20d后,地表覆膜、地表覆草、土中覆草处理的栽植穴土壤累积水分蒸发量分别比对照减少11.50、5.64、20.96mm。不同覆盖处理的栽植穴土壤含水量,4—6月减少量:对照>地表覆草>地表覆膜>土中覆草;6—8月增加量:土中覆草>地表覆草>地表覆膜>对照;8—10月减少量:对照>地表覆草>地表覆膜>土中覆草。生长季结束后,对照、地表覆膜、地表覆草、土中覆草土壤密度分别减少了0.79%、1.59%、3.17%、9.26%,总孔隙度分别增加了0.04%、0.31%、1.57%、3.58%。地表覆膜、地表覆草、土中覆草处理的苗高生长量分别是对照的3.52、4.11、4.44倍;当年新枝生长量分别是对照的1.50、1.65、1.90倍;当年造林成活率较对照分别提高了10.3%、6.8%、12.9%。可见在晋西黄土区干旱陡坡造林中,土中覆草是一种更有效的覆盖措施。 

Effects of different mulching measures on soil moisture and the first-year survival rate of afforestation

We investigated the effects of different soil surface mulching measures, i. e. , grass and plastic film, on evaporation, soil moisture content and the first-year survival rate of afforestation, in order to select appropriate mulching measures for afforestation in semi-arid and steep slope areas in the Caijiachuan Watershed, Jixian County, Shanxi Province. It was found that the cumulative evaporations for areas mulched with grass in soil, grass and plastic film on the surface were reduced by 20. 96,11. 5 and 5. 64 mm, respectively, compared with areas without mulching treatment, in the early 20 days after afforestation. From April to June of 2015, the reduction of soil moisture content of areas that received different mulching treatments was ranked as non-mulching > grass mulching on the surface > plastic film mulching on the surface > grass mulching in soil. However, the increase in soil moisture content of areas that received different mulching treatments from June to August was ranked as grass mulching in soil >grass mulching on the surface > plastic film mulching on the surface > non-mulching. From August to October, the reduction of soil moisture content of areas that received different mulching treatments was ranked in the same order as that from April to June. After the growing season ( April to October) ,the soil particle density in the area that received non-mulching, mulching of plastic film and grass on the surface
and mulching of grass in soil treatments decreased by 0. 79%,1. 59%,3. 17% and 9. 26%,and the total porosity of them increased by 0. 04%,0. 31%,1. 57% and 3. 58%, respectively. The average heights of trees planted in the soils that received mulching of plastic film and grass on the surface and mulching of grass in soil were, respectively, 2. 52,3. 11 and 3. 44 times higher, the mass growths of new branches were 0. 50,0. 65 and 0. 90 times larger, and the first-year survival rates were increased by 10. 3%, 6. 8% and 12. 9%, respectively, compared with those of the trees planted in soils that received non-mulching treatment. It can be concluded from the comparison that, the treatment of grass mulching in soil is helpful in improving soil moisture conditions and increasing the first-year survival rate of afforestation in semi-arid and steep slope areas in the Loess Plateau area of western Shanxi Province.