栗钙土不同土地利用方式下有机碳和无机碳剖面分布特征

栗钙土是半干旱地区典型的地带性土壤,主要分布在内蒙古自治区。文章以内蒙古自治区乌兰察布盟(简称乌盟)和锡林河流域为例,分析了栗钙土有机碳和无机碳含量及其密度的剖面分布特征,旨在了解不同土地利用方式下土壤碳库的储量和分布特点及其成因与机理。结果表明:土壤无机碳在剖面上的分布有两种类型:高—低—(高)—(低)型和低—高—(低)—(高)型,后者可能是由于土壤侵蚀引起的碳酸盐再分布所形成的。100cm深的土壤有机碳密度的平均值为8.48kg·m-2,退耕地>耕地>干旱半干旱草原>典型草原,主要分布在表层,0～30cm土壤有机碳密度为0～100cm的43%左右;而土壤无机碳密度的平均值为7.10kg·m-2,退耕地>典型草原>耕地>干旱半干旱草原,主要分布在下层土壤,50～100cm无机碳密度为0～100cm的58%左右。     

马鬃岭自然保护区土壤碳蓄积的研究

以金寨马鬃岭自然保护区为研究对象,布置56个采样点,分析该区森林土壤有机碳质量分数时空分布特征和碳储量。结果表明：研究区有机碳含量丰富,随着土壤深度、植被类型、海拔高度的变化而变化。0~20cm土层有机碳质量分数最高为90.88 g·kg-1,平均为32.47 g·kg-1,土壤有机碳质量分数随着深度的增加而递减,表层有机碳变化幅度高于深层土壤,不同测点递减的程度不同;有机碳质量分数随海拔高度的增加呈递增趋势;土壤有机碳质量分数存在明显的季节变化,表层土壤秋季有机碳质量分数最高,冬春季次之,夏季最低,越往表层季节变化越明显。0~20 cm土层有机碳密度平均为6.52 kg.m-2,0~100 cm土层有机碳平均密度为23.26 kg.m-2,有机碳密度分布与有机碳质量分数分布基本一致。0~20 cm土层土壤碳储量为2.258×105~2.265×105 t,0~100 cm土层土壤碳储量为6.91×105~8.76×105 t,碳储量丰富。最后提出该自然保护区封山育林,对温室气体减排意义重大。     

江西省表层土壤有机碳库储量估算与空间分布特征

土壤中碳较小幅度的变化能引起全球气候较大的变化,而表层土壤有机碳库易受人类活动的影响而发生变化,因此估算土壤有机碳库储量,对土壤碳库变化及土壤固碳潜力的研究具有重大意义.根据2006年江西省各县市典型土壤GPS定点采样样点的理化分析数据计算出有机碳密度并进行空间插值,利用江西省第二次土壤普查相关数据建立土壤空间数据库,结合各土壤类型分布面积,估算表层(0～20 cm)土壤有机碳密度和储量,并探讨其空间分布特征.研究表明:江西省表层土壤平均有机碳密度介于2.655～6.877 kg·m-2之间,有机碳库总储量为640 355.653×106 kg,其中,仅红壤和水稻土的土壤有机碳储量已占90.71%.表层土壤有机碳密度具有高度的空间变异性,赣西、赣东如萍乡、宜春、上饶地区土壤有机碳密度较高,赣南、赣北地区如九江、赣州等地区土壤有机碳密度较低,总体上呈东西走向高,南北走向低的趋势.江西省是一个农业大省,人类干扰下的土壤碳库研究却很少,其碳库动态变化还值得进一步的探讨.     

广东省土壤有机碳储量及分布特征

区域土壤有机碳调查在构建全球土壤碳循环的认识中具有重要作用。利用211个广东省土壤剖面数据,通过计算各剖面土壤有机碳密度,合理评估广东省不同土壤类型和土地利用方式的土壤有机碳储量。结果显示,广东省土壤有机碳总储量为1.25 Pg,其中,A层土壤(表层土壤,平均土层厚度为17 cm)有机碳储量为0.41 Pg,B层(平均土层厚度为29.5 cm)为0.51 Pg,C层(平均土层厚度为48.9 cm)为0.33 Pg。依据土壤发生学分类,研究区铁铝土土壤剖面有机碳碳储量为0.976Pg,占土壤有机碳总储量的78.1%。按土地利用方式,研究区林地土壤剖面有机碳储量为1.01 Pg,占土壤有机碳总储量的80.3%。统计结果表明,底层土壤(B层+C层土壤)有机碳储量是表层土壤有机碳质量分数的2倍以上,是研究区土壤有机碳的主要碳库。相关分析结果显示,底层有机碳质量分数与表层土壤有机碳质量分数呈显著的相关性,这种相关性是区域尺度上表层土壤有机碳向下迁移的表现。此外,每年由土壤退化侵蚀造成的直接进入周边水体的土壤有机碳流失量为13.3 Tg,约占表层土壤有机碳储量的3.2%,同时每年有20.9 Tg有机碳在研究区土壤中重新分布。研究结果可为合理评估研究区土壤有机碳储量和土壤环境管理提供科学支撑。     

桂北地区桉树林及其他三种森林类型土壤有机碳含量及密度特征

以桂北地区桉树（Eucalyptus grandis×E.urophylla）林、杉木（Cunninghamia lanceolata）林、马尾松（Pinus massoniana）林和毛竹（Phyllostachys edulis）林的土层0~60 cm土壤为研究对象,对比分析了4种森林类型的土壤有机碳质量分数及密度分布特征。结果表明：（1）在4种森林类型土层中,有机碳质量分数的最大值[（49.49±1.16）g·kg-1]和最小值[（4.50±0.52）g·kg-1]分别出现在毛竹林土层0~15 cm和马尾松林土层45~60 cm。土层0~60 cm有机碳质量分数平均值按大小顺序排列为：毛竹林（28.16g·kg-1）〉杉木林（25.10 g·kg-1）〉桉树林（14.52 g·kg-1）〉马尾松林（9.56 g·kg-1）。桉树林、杉木林、马尾松林和毛竹林土层0~15 cm有机碳质量分数所占的比例分别为28.29%、39.14%、55.44%和43.94%。（2）4种森林类型土层中有机碳密度的最大值[（6.71±1.72）kg·m-2]和最小值[（1.14±0.11）kg·m-2]分别出现在杉木林土层0~15 cm和马尾松林土层40~60 cm。土层0~60 cm的有机碳密度平均值按大小顺序排列为：杉木林（19.60 kg·m-2）〉毛竹林（18.85 kg·m-2）〉桉树林（12.91 kg·m-2）〉马尾松林（8.47kg·m-2）。桉树林、杉木林、马尾松林和毛竹林土层0~15 cm有机碳密度所占的比例分别为25.12%、34.25%、52.07%和32.64%。4种森林类型土壤有机碳质量分数和有机碳密度均随着土层深度的增加呈降低的趋势。     

宁夏贺兰山三种植被下土壤有机碳密度的比较

干旱、半干旱地区的土壤有机碳库是全球土壤碳库的重要组成部分,在全球碳循环的研究中有着重要作用.本文以宁夏贺兰山国家级自然保护区的油松(Pinus tnbulaeformis Carr.)、灰榆(Ulmus glaucescens Franch.)和灌丛三种植被下的土壤为研究对象,比较分析了这三种土壤不同层次有机碳含量和有机碳密度的变化情况.结果表明:三种土壤的有机碳含量均随着深度的增加而减少;油松植被下土壤的有机碳密度最高(11.30±0.36 kg·m-2),灰榆植被下土壤的有机碳密度次之(4.34±0.13kg·m-2),灌丛植被下土壤的有机碳密度最低(2.50±0.07 kg·m-2);油松、灰榆和灌丛三种植被下的土壤表层(0-5 cm)有机碳储量分别占其土壤有机碳总储量的10.32%±0.07%、23.43%±0.69%和26.80%±0.20%,灰榆和灌丛植被下的土壤发育情况较差,其有机碳相对较多地储存在表层土壤中;发育较好的土壤,其有机碳总储量也较高.为减少土壤表层CO2的排放,我们应加强对地表植被的保护,这对减缓全球变暖趋势具有重要意义.     

粤北山区近25年来耕地表层土壤有机碳变化分析

以粤北山区典型区的连州市为例,利用第二次土壤普查资料和2007年耕地地力调查样点分析结果,对研究区耕地表层（0~20 cm）土壤有机碳质量分数和有机碳密度的变化特征进行了分析。结果表明：25年以来,连州市耕地表层有机碳质量分数和密度有所增加,分别从1982年的16.3 g·kg-1、40.88 t·hm-2上升到2007年的17.37 g·kg-1、43.31 t·hm-2。土壤有机碳随土壤类型的不同而变化复杂,土壤有机碳呈上升趋势的有潴育型水稻土、淹育型水稻土、渗育型水稻土,而沼泽型水稻土、潜育型水稻土和矿毒田呈下降趋势,主要旱地土壤类型（黄壤、红壤、红色石灰土、酸性紫色土）表层土壤有机碳质量分数呈上升趋势。从土地利用类型综合考量,水田、旱地表层土壤有机碳质量分数和密度都呈上升趋势,其中水田的有机碳质量分数和密度分别由80年代初期的18.30 g·kg-1、44.80 t·hm-2上升到2007年的18.78 g·kg-1、46.21 t·hm-2;旱地的有机碳质量分数和密度分别由80年代初期的10.46 g·kg-1、29.27 t·hm-2上升到2007年的13.17 g·kg-1、34.67 t·hm-2。粤北山区耕地表层土壤总体上表现为碳汇。     

潮滩湿地土壤有机碳储量及其与土壤理化因子的关系——以崇明东滩为例

基于上海崇明东滩2013年3月的实测数据,借助ArcGIS软件进行Kriging空间插值,运用SPSS 21.0软件进行相关分析及通径分析,研究了崇明东滩表层30 cm深度土壤有机碳含量以及环境因子的空间分布特征,并对土壤有机碳储量进行了估算.结果表明,崇明东滩表层30 cm深度土壤有机碳密度介于1.02～5.22kg· m-2之间,平均值为2.32 kg·m-2,土壤有机碳储量为1.15×10s kg.土壤有机碳含量、土壤全盐量、含水量和NDVI指数的空间分布规律类似,呈现北高南低、高潮滩高而低潮滩低的趋势.中值粒径和容重的空间分布规律类似,表现为北低南高,高潮滩小于低潮滩.高程和pH值的空间分布规律不明显,空间变异性较小.7项环境因子与土壤有机碳含量都存在显著相关性,其中土壤全盐量是影响崇明东滩表层土壤有机碳含量的最主要因子.     

黄河下游灌区土壤碳储量及碳密度分布

土壤碳（C）,特别是土壤有机碳（SOC）,对于提高作物产量和减少温室气体排放具有重要影响,深入理解 SOC 空间分布特征对于未来区域生态环境和农业的可持续发展也具有重要作用。黄河下游引黄灌区是我国重要的粮、棉生产基地,具有50年以上的引黄灌溉历史,长期引黄灌溉对区域土壤C储量和分布的改变毋庸置疑。以往关于土壤C的估算多集中于较大尺度,受采样数据量和大区域环境因素复杂变异影响,结果经常出现较大差异,并且对于大型水利灌溉对土壤 C 分布的长期影响研究较少,尤其对于我国黄河下游引黄灌区土壤 C 分布的研究稀缺。本文通过收集黄河下游鲁、豫灌区相关统计资料,灌区土壤、水文资料等,分7层（0～5 cm、5～10 cm、10～20 cm、20～40 cm、40～60 cm、60～80 cm、80～100 cm）采集0～1 m剖面土壤样品,利用GIS空间差值、空间统计方法,分析不同土层、土地利用、土壤类型碳储量和碳密度（CD）空间分布特征,为研究区长期引黄灌溉条件下生态农业的发展提供依据。结果表明研究区（面积54153 km2）1 m土层总碳（TC）储量为1045.13 Tg,SOC储量达815.76 Tg,其0～20 cm,20～40 cm,40～60 cm,60～80 cm和80～100 cm分别占23.44%,20.06%,18.95%,18.83%,18.72%。估算1 m土层耕地和荒地SOC储量分别约为610 Tg和18.99 Tg,而草地和林地仅为25.97 Tg和16.41 Tg;不同土壤成土类型之间,半水成土所占的比例最大（约77.82%）,初育土最小（约5.49%）。1 m土层平均总碳密度（TCD）为（19.37±1.48） kg·m^-2,而平均有机碳密度（SCD）为（15.12±1.14） kg·m^-2,其变化范围从荒地的（14.98±0.91） kg·m^-2到林地的（16±1.15） kg·m^-2,同一或不同土地利用类型各层储量变化略有不同,主要是受人类活动、植被凋落物输入以及地下水环境等影响。不同的土壤类型间SCD则介于?     

粤北山区近25年来耕地表层土壤有机碳变化分析

以粤北山区典型区的连州市为例,利用第二次土壤普查资料和2007年耕地地力调查样点分析结果,对研究区耕地表层(0~20 cm)土壤有机碳质量分数和有机碳密度的变化特征进行了分析。结果表明:25年以来,连州市耕地表层有机碳质量分数和密度有所增加,分别从1982年的16.3 g·kg-1、40.88 t·hm-2上升到2007年的17.37 g·kg-1、43.31 t·hm-2。土壤有机碳随土壤类型的不同而变化复杂,土壤有机碳呈上升趋势的有潴育型水稻土、淹育型水稻土、渗育型水稻土,而沼泽型水稻土、潜育型水稻土和矿毒田呈下降趋势,主要旱地土壤类型(黄壤、红壤、红色石灰土、酸性紫色土)表层土壤有机碳质量分数呈上升趋势。从土地利用类型综合考量,水田、旱地表层土壤有机碳质量分数和密度都呈上升趋势,其中水田的有机碳质量分数和密度分别由80年代初期的18.30 g·kg-1、44.80 t·hm-2上升到2007年的18.78 g·kg-1、46.21 t·hm-2;旱地的有机碳质量分数和密度分别由80年代初期的10.46 g·kg-1、29.27 t·hm-2上升到2007年的13.17 g·kg-1、34.67 t·hm...     

Edge Effects and Isolation: Red-Backed Voles Revisited

Abstract:  We examined demographic responses of California red-backed voles ( Clethrionomys californicus ) to forest fragmentation in southwestern Oregon at sites where this species has previously shown negative responses to fragmentation. Voles were captured in live traps and released. Voles were rarely caught in clearcuts surrounding 11 forest fragments, but relative vole density did not decrease from the forest-fragment interiors to edges. The first result agrees with previous findings at these sites 6 years earlier, but the latter result does not. There was no evidence that vole response to edge changes with fragment age. Two years of intensive mark-recapture efforts at two forest-fragment sites and two unfragmented (control) sites did not show negative effects of fragmentation on vole survival, an important demographic rate. Vole capture probabilities varied greatly across space and time on these four sites, which may explain the differences in vole responses to edge seen between this and the previous study. These results suggest that reliable appraisal of edge effects may be difficult for many species on small fragments because the data necessary to apply population estimators require great efforts to obtain and the use of indices leads to a confounding of detection probabilities with demographic change.     

Development of an integrated decision-support model for density management within jack pine stand-types

The objectives of this study were to (1) develop a modular-based structural stand density management model (SSDMM) and corresponding algorithmic analogue for natural (naturally regenerated stands without a history of density regulation) and managed (naturally or artificially regenerated stands with a history of density regulation) jack pine (Pinus banksiana Lamb.) stand-types, and (2) demonstrate the utility of the model in operational density management decision-making. Employing an Ontario-centric database consisting of 262 and 221 tree-list measurements obtained from 91 and 139 permanent and temporary sample plots situated within natural and managed stand-types, respectively, combined with data derived from density control experiments and sawmill simulation studies, six integrated estimation modules were constructed: Module A consisted of the parameterization of the core yield–density relationships which together drive the entire yield prediction system (e.g., size–density relationships for quadratic mean diameter, dominant height, mean volume, and mean live crown ratio, and site-specific height–age relationships); Module B consisted of the development of Weibull-based parameter prediction equation systems for recovering diameter distributions and composite height-diameter equations for height estimation; Module C consisted of the development of composite taper equations for predicting log products and stem volumes; Module D consisted of the development of allometric-based composite biomass equations for each above-ground component (bark, stem, branch and foliage) from which biomass estimates and associated carbon-based equivalents were derived; Module E consisted of the development of sawmill-specific composite equations for estimating chip and lumber volumes; and Module F consisted of the development of composite equations for estimating wood density and mean maximum branch diameter. The utility of the model was demonstrated by simultaneously contrasting a set of complex density management regimes (commercial thinning and variable planting densities) in terms of a broad array of stand-level yield outcomes and performance measures: overall productivity, log-product distributions, biomass production and carbon yields, recoverable products (chip and lumber volumes) and associated monetary values, economic efficiency, duration of optimal site occupancy, structural stability, and fibre attributes (wood density and mean maximum branch diameter). In summary, the modular-based SSDMM provides the analytical foundation for evaluating the likelihood of realizing a multitude of stand-level objectives when designing density control regimes for jack pine stand-types.     

不同耕作方式对土壤性质与玉米生长的影响研究

通过种植前对土壤进行不同耕作处理试验,探讨不同耕作方式和耕作深度（30 cm,35 cm,45 cm）对土壤理化性状及玉米（Zea mays L）根系生长的影响。结果表明,三种耕作方式对土壤容重、土壤含水量、土壤微生物总量、玉米根系生长的影响表现为：深松耕作〉传统耕作〉免耕。其中,深松耕作对表层土壤（0～25 cm）容重降低作用大于深层土壤（25～45 cm）;对增加土壤含水量、增加土壤微生物总量、促进玉米根系生长方面的作用,深层土壤大于表层土壤;从不同耕作深度进行比较,深松45 cm〉深松35 cm〉深松30 cm〉传统耕作,即耕作越深,对土壤物理性状和作物根系生长影响越大。不同耕作处理间玉米产量无显著性差异。综合研究区的土壤性质、作物生长、自然环境等因素,雨养农区可采用免耕—深松的循环耕作模式,改良土壤性质,提高经济效益。     

Calculation of Entrainment in Density Jumps

The density jump in a two-layer channel flow of miscible fluids, in which one of the layers is infinitely deep and at rest, is analyzed using the momentum flux and mass flux conservation equations. The analysis yields simple equations relating the heights upstream and downstream of the jump with the upstream Froude number and the rate of entrainment into the moving layer, as well as a relation between the maximum possible entrainment and the upstream Froude number. The analysis also shows that when the flow down-stream of the jump is controlled by an obstruction or a contraction, the entrainment rate into the jump depends solely on the dimensionless obstruction height contraction ratio and the upstream Froude number.     

Carbon monoxide levels at a toll plaza near Durban, South Africa

Reliable measurements of pollutant levels in the vicinity of a toll plaza appear to be rare. In order to assess the exposure of toll booth operators to carbon monoxide, a continuous carbon monoxide monitor was installed at head height in the booth of a medium density traffic lane at the Mariannhill toll plaza, situated on a busy highway near Durban, South Africa. Measurements in excess of 500 ppmv were recorded and the high daily mean carbon monoxide concentrations may account for some of the symptoms such as headaches and general malaise that have been reported by workers in the booths. Generally, carbon monoxide levels recorded far exceed the recommended limit set by the South African authorities. These results have led to recommendations regarding the structure of new and existing toll booths to minimize the exposure of toll booth workers to adverse effects of vehicle-emitted pollutants.     

Vertical Buoyant Jets in a Linearly Stratified Ambient Cross-Stream

In this study a numerical simulation is performed to investigate the effect of ambient density stratification on the characteristic of a vertical buoyant jet in a stably linearly stratified ambient cross-stream. Based on the ensemble integral method, the theoretical formulation for such a flow field consists of a set of elliptic Reynolds-averaged equations incorporating with the k– transport equations for the turbulence closure. An oscillating motion can be observed in the computed jet trajectory, and the corresponding alternative variation of dominant quantities for the induced momentum and buoyancy of the jet are examined by direct integration on a cross-section along the jet axis. The influences on the jet development both by the ambient cross-stream and the stratification are investigated. The oscillation characteristic shows that a linear relation holds between the wavenumber of jet trajectory, crossflow velocity and the Brunt–Väisälä frequency of ambient stratification. Computational results indicate that the formation of the secondary and a third pairs of vortices, which are not induced in the unstratified environment, causes the jet flow oscillation from its maximum height-of-rise in the flowing direction. The ambient stratification prohibits the growth of the plume radius and reduces the mixing rate as well as the plume rise. The developed flow indicates the transformation of entrainment mechanism in stratified crossflow.     

Population dynamics of farmland ladybug resources and dominant species in Nyingchi,Tibet, China北大核心CSCD

捕食性瓢虫是重要的天敌昆虫,有利于害虫的生物防治.为查清西藏林芝地区农田瓢虫资源与种群现状,明确优势种类及种群动态和规律,对林芝不同生态区域的青稞、小麦、油菜3种作物农田开展瓢虫资源调查研究,同时选取固定样地定期进行种群动态分析.结果显示:林芝地区农田瓢虫分为2个亚科4个族10个属,共13种,其中11种为捕食性瓢虫.主要优势瓢虫种类为横斑瓢虫、多异瓢虫、二星瓢虫.其中横斑瓢虫在全部调查样地中均有分布,在农田中总体优势度指数、相对多度为最高.3种优势瓢虫在不同作物中种群动态变化规律存在差异,其中横斑瓢虫虫口密度长期高于其余优势瓢虫,且与蚜虫密度曲线有较为明显的重合现象.横斑瓢虫种群密度峰值主要集中在6月中旬至7月上旬,但在不同作物农田中具体峰值时期存在差异.可见,林芝地区农田不同种类瓢虫之间有较大数量差异,在不同生态区域与作物环境下具有不同的种群特征,但是优势瓢虫种类与种群规律较为明确,可用于农田蚜虫生物防治;结果可为保护当地重要昆虫资源及开展生物防治提供基础数据支撑.(图4表6参23)     

春玉米种植密度对土壤有机碳组分的影响

通过西辽河灌区连续3 a的田间试验,研究春玉米不同种植密度（60 000、75 000和90 000株·hm-2）下土壤有机碳组分的质量分数及空间分布特征,阐明了春玉米种植密度对不同层次土壤有机碳组分的影响机制。结果表明：高、低密度均增加土壤0～40 cm土层有机碳质量分数,中密度下促进土壤微生物生物量碳增加。随着种植密度的加大土壤中活性有机碳增加,轻组有机碳减少。玉米生长主要促进10～20 cm土层有机碳的耗损,高密度下促进犁底层（20～40 cm）土壤有机碳质量分数及其活性,使其轻组有机碳减少,微生物生物量碳增加。低密度下主要增加表层（0～10 cm）土壤有机碳质量分数。种植密度通过影响根系群体生物量及其分布,调节土壤微生物活性、残落物碳输入影响土壤有机碳组分。适当的增加春玉米种植密度有利于春玉米农田高产固碳。     

Techno-economic analysis for the electrocoagulation of fluoride-contaminated drinking water

Electrocoagulation (EC) technique was adopted for the treatment of fluoride-containing drinking water in a 3?L capacity batch reactor. Experimental investigation was carried out to observe the effect of different operating parameters, such as initial fluoride concentration, current density, inter-electrode distance, on the removal of fluoride from the fluoride-rich drinking water. Aluminum flat sheet was used as the electrode material. It was observed that with an increase in current density, percentage removal of fluoride increased. It was seen that at electrode distance of 0.005?m, removal of fluoride attained its maximum compared to the other performances obtained at different inter-electrode distances. Life time of the aluminum electrodes was estimated from the electrode corrosion observed during the experiment. Total operating cost was estimated as a combination of energy cost and electrode cost. The total operating cost was evaluated as 0.38?US$?m^?3 to remove fluoride from the solution with an initial fluoride concentration 10?mg?L^?1. Characterizations of the electrochemically generated by-products were carried out by powder X-ray diffraction, Fourier transform infra-red Raman spectroscopy, scanning electron microscopy image and corresponding elemental analysis.     

Sorption of heavy metals in strongly weathered soils: an overview

Current knowledge of sorption processes in tropical soils is reviewed. Landscapes throughout the tropics are dominated by oxisols which occupy extensive areas of potentially highly productive soils. These soils are dominated by low-activity sesquioxide minerals and clays that have variable charge surfaces. The limited information on tropical soils available suggests that the composition of the ambient soil solution can influence sorption through changes in particle surface-charge density. Thus the observed decrease in sorption in the presence of divalent index cations may be related to the effect of ionic charge on the double-layer thickness which is manifested through a change in surface-charge characteristics. However, much work needs to be done to differentiate the effect of cation charge on surface-charge density from the competitive effect between the index cation and heavy-metal ions for the sorption sites. The effects of inorganic and organic ligands on adsorption of Cd by variable charge surfaces are also reviewed.