黄土丘陵区植被恢复对深层土壤有机碳储量的影响

Effects of revegetation on organic carbon storage in deep soils in hilly Loess Plateau region of Northwest China

以黄土丘陵区不同恢复年限的人工刺槐林、人工柠条林和自然撂荒地为对象,以0～100cm(浅层)土壤为对照,研究了不同植被类型下100～400cm(深层)土壤有机碳(SOC)储量的剖面分布特征和累积动态.结果表明:随土壤深度增加,浅层SOC储量显著降低,深层SOC变化趋势不明显,但储量很高,约占0～400cm剖面SOC的60%.80～100cm土层的SOC储量与深层100～200和200～400cm的SOC储量呈显著线性相关,是0～100cm5个土层中与深层SOC储量变化相关性最强的一层,可用以估算深层SOC储量.人工刺槐林、柠条林、撂荒地表层(0～20cm)SOC储量显著高于坡耕地,而深层SOC储量在不同利用类型间差异不显著.随植被恢复年限的增加,深层SOC储量呈上升趋势,人工刺槐林和人工柠条林100～400cmSOC平均累积速率分别为0.14和0.19t·hm-2·a-1,人工柠条林与浅层SOC累积速率相当.在估算黄土丘陵区植被恢复的土壤固碳效应时,应考虑深层土壤有机碳累积量,否则会严重低估植被恢复的土壤固碳效应.

Taking the Robinia pseudoacacia woodlands,Caragana korshinskii shrublands,and abandoned croplands with different years of revegetation in the hilly Loess Plateau region of Northwest China as test objects,this paper studied the profile distribution and accumulation dynamics of organic carbon storage in deep soil （100-400 cm）,with those in 0-100 cm soil profile as the control.In 0-100 cm soil profile,the organic carbon storage decreased significantly with the increase of soil depth;while in deep soil,the organic carbon storage had a slight fluctuation.The total organic carbon storage in 100-400 cm soil profile was considerably high,accounting for approximately 60% of that in 0-400 cm soil profile.The organic carbon storage in 80-100 cm soil layer had a significant linear correlation with that in 100-200 and 200-400 cm soil layers,and among the organic carbon storages in the five layers in 0-100 cm soil profile,the organic carbon storage in 80-100 cm soil layer had the strongest correlation with that in 100-400 cm soil profile,being able to be used to estimate the organic carbon storage in deep soil in this region.The organic carbon storage in 0-20 cm soil layer in the three types of revegetation lands was significantly higher than that in slope croplands,but the organic carbon storage in deep soil had no significant difference among the land use types.The organic carbon storage in deep soil increased with the increasing years of revegetation.In R.pseudoacacia woodlands and C.korshinskii shrub lands,the average increasing rate of the organic carbon storage in 100-400 cm soil layer was 0.14 and 0.19 t·hm-2·a-1,respectively,which was comparable to that in the 0-100 cm soil layer in C.korshinskii shrublands.It was suggested that in the estimation of the soil carbon sequestration effect of revegetation in hilly Loess Plateau region,the organic carbon accumulation in deep soil should be taken into consideration.Otherwise,the effect of revegetation on soil carbon sequestration would be significantly underestimated.