植被对黄土高原沟壑区坡地土壤有机碳的影响

选取高原沟壑区王东沟流域内典型的治理坡段,研究不同植被条件下土壤有机碳、氮的含量变化和坡面分布特征。结果表明:与荒草(白羊草)群落相比,油松群落条件下,土壤有机碳含量提高9.3%(P>0.05),而果园土壤有机碳含量降低40.1%(P<0.05)。沙棘、侧柏和刺槐群落下,土壤有机碳含量虽低于荒草群落,但尚未达到显著水平(P>0.05)。果园和刺槐群落下坡面有机碳变化趋势不明显;杏树群落下表现为坡中部含量高,上部和下部低;白羊草群落下坡面有机碳含量从上到下逐渐增加。不同植被条件下土壤全氮与土壤有机碳存在极显著(R²=0.925)的相关关系。

Effect of Vegetation on Soil Organic Carbon of Slope Land in Gully Region of Loess Plateau

Vegetation recovery is an important measure to mitigate soil erosion and improve soil quality in the Loess Plateau.To understand the impact of vegetation recovery on soil quality,soil organic carbon (SOC) and total soil nitrogen(TSN)level and distribution characteristics along a slope under vegetation conditions were investigated on slope of Wangdonggou Watershed in Gully Region of Loess Plateau.Five experiment sites were set up along Fanjialiang.Site I to site Ⅳ along the eastern slope of Fanjialiang was Xingniugua,Dujiaping,Baiyanggua east and Bai-yanggua west,being adjacent to each other with similar slope and aspect.The vegetations were Prunus armeniaca L,orchard(Malus pumila),Robinia pseudoanacia and grass(Bothriochloaischaem- um(L.)Keng),respectively.Soil samples(0～20cm)at each site were taken from the upper slope,middle slope,lower slope and the foot slope,respectively.Site V at the western slope of Fanjialiang was Shaozhongwan with six vegetation types including Robinia pseudoanacia,arborvitae(Platycl- adus orientalis Endl.)、Chinese pine(P. tabulaeformis Carr),Hippophae rhamnoides L. subsp,Malus pumila and grass.Soil samples(0～60cm)were taken under vegetations.Types,population,and height of plants of each site were surveyed. The results demonstrated that compared with grassland,SOC content increased by 9.3%(P>0.05)for Chinese pine and decreased by 40.1%(P<0.05)for orchard.SOC content under Hippophae rhamnoides L.subsp.,arborvitae,and Robinia pseudoanacia was lower than that of grassland,but the difference was not significant(P>0.05).The level of SOC decreased with depth.For the site under grass,the content of SOC at lower slope and foot slope was respectively 47.6% and 62.9% higher than that at the upper slope with 7.8g·kg^-1.For the site of orchard,SOC content was 6.17g·kg^-1～6.69g·kg^-1 at the middle and foot slope,higher than that at the upper (5.54g·kg^-1).For the site of Robinia pseudoanacia,content of SOC varied from 8.55 to 10.50g·kg^-1,similar SOC along slope changes under orchard and Robinia pseudoanacia.For the site of Prunus armeniaca L.the content of SOC varied from 9.79g·kg^-1 to 14.41g·kg^-1,higher in the middle along the slope.In addition,there was a significant(R²=0.925)correlation between TSN and SOC. Intensive human disturbance resulted in lower SOC content in the region.Planting orchard on the slope significantly improved the productivity of soil,but it is not profitable to SOC accu-mulation.Some suggestions on vegetation construction in the region were put forward:1)vegetation types should be considered fully when vegetation regeneration and rehabilitation were carried out on the slopes in the region. 2)To adjust the growth conditions and increase input of SOC is essential to enhance SOC accumulation in the region.