坡耕地黑土有机碳和全氮的迁移与累积平衡

本文利用137CS示踪技术计算东北黑土坡耕地土壤再分布速率,结合表层土壤有机碳(SOC)和全氮(TN)含量动态,探索典型漫岗坡地SOC和TN流失量的空间分布特征,据此计算研究区近50年来SOC和TN迁移、累积平衡。研究结果表明:研究区土壤再分布速率介于-24.61~33.56 T/HM2/A,绝大部分地区处于中度和轻度侵蚀状态,约占研究区总面积的83.66%,沉积面积占总面积的15.62%。SOC和TN的流失量与土壤再分布速率相一致,坡肩部位SOC和TN流失量最大,侵蚀损失率分别为407.57 KG/HM2/A和39.94 KG/HM2/A;其次为坡背和坡顶,平均流失量分别为244.2 KG/HM2/A和17.93 KG/HM2/A;坡脚和坡趾表现为累积,平均累积量分别为-207.2 KG/HM2/A和-20.56 KG/HM2/A。整个研究区SOC和TN的相对流失量>50%的面积分别占10.45%和11.21%。整个研究区48年来土壤净迁移泥沙量为45.54 T/A,其中,SOC流失量为612.62 KG/A,TN流失量为47.20 KG/A。考虑迁移泥沙对土壤有机质的富集作用,迁移损失的SOC和TN量比原计算值高52%。     

坡耕地土壤有机碳再分布特征及其迁移累积平衡

利用137Cs和飞灰示踪技术,研究坡耕地黑土近50年和近100年来土壤再分布过程,计算坡耕地土壤有机碳(SOC)迁移和累积平衡。结果表明:利用SOC的深度分布特征鉴定坡脚和坡足原始埋藏土壤的表面分别位于地表下70和80cm,其埋藏层的SOC含量分别比与其接壤的上覆土层SOC含量高5.2和0.4gkg。坡顶、坡肩和坡背均遭受侵蚀,年平均侵蚀的土壤厚度为0.2、5.0和2.2mmyr。坡脚和坡足部位飞灰到达的深度分别为70和80cm,与埋藏层表面相吻合。坡脚飞灰出现于埋藏A层之中,表明沉积区在蒸汽机车开始使用前已被开垦为农田(或已有侵蚀和堆积发生)。根据137Cs和飞灰分布深度构建了不同年代的坡型,结果表明侵蚀部位剥蚀的土壤多堆积在坡脚和坡足,且搬运的土壤物质先累积于坡脚,随着景观坡度变缓,土壤累积逐渐向坡足过渡。研究区(1m宽)坡顶、坡肩和坡背近百年来由于土壤侵蚀共失去683kgSOC,其中60%(418kgSOC)沉积在坡脚和坡足等低洼部位,其中有257kgSOC是近50年累积的。     

ASSESSMENT OF LAND COVER CHANGES AND THEIR EFFECT ON SOIL ORGANIC CARBON AND SOIL TOTAL NITROGEN IN DAQING PREFECTURE,CHINA

The aim of this study was to examine the influence of land cover changes on soil organic carbon (SOC) and soil total nitrogen (STN) in the Daqing Prefecture of China, where heavy industrialisation in the form of dense oil wells has impacted the environment. Time‐series presentations for the period 1978 to 2008 of remotely sensed data and soil survey data were used to assess the extent of the changes. The study revealed soil degradation under all land cover types and in all soil types, grassland retreat (−15 per cent), swampland retreat (−45 per cent) and increases in the area of farmland (+19 per cent), sand land (+1450 per cent) and alkaline land (+52 per cent). Depletion of the SOC pool occurred in swampland (−64 per cent) both because of the decrease in the area of swampland and because of a decrease in SOC density (−34 per cent). An increase in the SOC pool occurred in alkaline land because of the increase in the area and also because of an increase in SOC density (+297 per cent), but there was little change in the SOC pool in farmland because the increase in area was largely offset by a decrease in SOC density (−14 per cent). The decrease in the STN pool was substantial (−44 per cent), with the largest contributor being the decrease in swamplands (−74 per cent), partly because of the decrease in the area of swampland and partly because of a decrease in STN density (−52 per cent). Large decreases in the STN pool also occurred in farmland (−22 per cent) and grassland (−41 per cent). The direct impacts of construction associated with the expansion of the oil industry were overshadowed by indirect impacts such as interference with water flows and water levels resulting in salinisation of soil. The study also revealed that land cover changes are much more dynamic than a simple analysis would reveal, and because of lag times in the loss of SOC, soil degradation will continue even if land cover changes cease. Copyright © 2012 John Wiley & Sons, Ltd.     

137Cs在灌耕灰棕漠土腐殖质各组分的分布

研究了新疆灌耕灰棕漠土腐殖质组分及其性质,并利用凝胶过滤法室内研究了外源137Cs与土壤腐殖质各组分的结合性能.结果表明:在研究条件下,137Cs与粘土矿物的结合率最高,占总量的78.37%;21.63%的137Cs积累于腐殖质中,其中与胡敏酸、富啡酸、胡敏素结合的分别为5.78%、6.60%和9.25%.腐植酸与13...     

利用燃煤飞灰作为时间标记物评价坡耕地黑土侵蚀物质和有机碳的再分配

燃煤飞灰(以下简称飞灰)作为时间标记物克服了放射性同位素137Cs示踪方法不能鉴定大气核爆炸之前的土壤再分布过程这一缺陷。本文利用土体中的飞灰研究坡耕地黑土有机碳的时空再分布特征。尝试建立飞灰在土壤中分层的方法,根据飞灰和土壤有机碳(SOC)随土壤深度的分布特征鉴定土壤堆积厚度,以及堆积土壤的相对年代。结果表明:用飞灰示踪技术鉴定的埋藏土壤表层与SOC含量随深度变化确定的埋藏表层吻合较好,景观中低洼部位在飞灰出现前就有一定的土壤堆积。各地貌部位坡肩侵蚀最为严重,有机碳含量最低;坡顶坡度较小,侵蚀微弱;坡脚和坡足发生沉积。土壤沉积速率在1.01~5.56mm a-1之间。研究结果还表明堆积部位埋藏层的SOC含量较高,说明有相当数量的有机碳被隐遁在目前的耕作层之下。因此,在评价农田土壤作为大气CO2“源”或“汇”时应该考虑景观中土壤物质迁移和埋藏作用的影响。     

137Cs应用于我国西部风蚀地区土地退化的初步研究─-以新疆库尔勒地区为例

本文以新疆库尔勒地区为例,首次运用＾１３７Ｃｓ示踪分析法对我国西部风蚀地区土壤侵蚀的强度与区域分布进行了研究,分别计算出该地区荒地,耕地,草地等土地利用类型的土壤侵蚀数平均值为５９８７．２１吨／平方公里;年,３５３７．２９吨／平方公里．年３１７１．３１吨／平方公里．年,其土壤侵蚀强度依次为荒地－耕地－草地。并据此探讨了不同土地利用类型与土地退化之间的相关关系有空间特征。