侵蚀逆境下土壤有机碳的迁移

土壤有机碳是陆地碳库的重要组成部分。土地利用和土地覆盖变化使得土壤中有机碳的含量发生很大的变化。土壤侵蚀是陆地碳库衰减的主要动力之一，也是陆地碳汇与海洋碳汇相互作用的重要过程。文章对土壤活性有机碳以及不同土地利用方式对土壤有机碳的影响作了介绍。     

Modeled carbon sequestration variation in a linked erosion–deposition system

Unraveling the consequences of hydrologic transport on carbon (C) storage will help identify feedbacks between land management alternatives, climate change, and soil-vegetation-atmospheric-transfers (SVATs) of C. There is a need for theoretically driven models of erosion and deposition that includes transport induced mineralization to better understand the controls on SVATs of C. Here we present a model developed using a systems-dynamic approach that coupled C-SVATs at a 2-day resolution with a discrete event erosion–deposition model occurring with a prescribed return interval. Five possible mass-balance transformations of C occurring between the two patches were explicitly modeled: net primary production (NPP), decomposition, erosion, transport induced mineralization, and deposition. The net C-SVAT, NPP minus decomposition, exhibited three stable points of no net C flux. Starting with arbitrary initial C pool in each patch above the bifurcation point, the model approached a quasi-steady state, which included both the short-term and longer term consequences of erosion; in the baseline simulation 5080 g C m⁻² was stored prior to erosion and 100 years of low intensity erosion 4840 g C m⁻² SOC remained. Low intensity erosion also generated spatial heterogeneity; from an initial homogeneous distribution to 40% of the C stored in the eroded patch and 60% of the C stored in the deposition patch. Erosion reduction resulted in a corresponding increase in total soil C content that was positively related to the magnitude of erosion reduction. In conjunction with providing a modeling framework for reducing the uncertainty in C-SVAT, this model is a prototype of a growing theory of ecosystem processes within spatially explicit landscapes, a meta-ecosystem model.     

北京山区典型流域不同海拔椴树种群的空间点格局分析

采用点格局分析法对不同海拔的椴树（Tilia miqueliana Maxim.）种群进行分布格局及其种间关系进行了研究。结果表明：整体上群落内以中龄树个体数为最多,小树次之,成年树个体最少。随着海拔的增加可以看出：小树（d≤5 cm）随着海拔的增加而减少,中树（5 cm20 cm）的规律不明显;椴树种群的空间分布格局与空间尺度（25 m内）有密切关系,在较小的空间尺度上倾向于非随机分布,具有明显的空间相关性;在〉15 m或25m的某临界尺度时却倾向于随机分布,同时空间关联变得微弱。随着海拔的增加,各物种聚集分布的尺度有逐渐减小的趋势。种间关系随着海拔的增加,物种间的正相关尺度有增加的趋势。     

北京山区典型流域不同海拔椴树种群的空间点格局分析

采用点格局分析法对不同海拔的椴树(Tilia miqueliana Maxim.)种群进行分布格局及其种间关系进行了研究。结果表明:整体上群落内以中龄树个体数为最多,小树次之,成年树个体最少。随着海拔的增加可以看出:小树(d≤5 cm)随着海拔的增加而减少,中树(5 cm20 cm)的规律不明显;椴树种群的空间分布格局与空间尺度(25 m内)有密切关系,在较小的空间尺度上倾向于非随机分布,具有明显的空间相关性;在>15 m或25m的某临界尺度时却倾向于随机分布,同时空间关联变得微弱。随着海拔的增加,各物种聚集分布的尺度有逐渐减小的趋势。种间关系随着海拔的增加,物种间的正相关尺度有增加的趋势。     

SWOT analysis for socio-ecological landscape variation as a precursor to the management of the mountainous Kanshi watershed,Salt Range of Pakistan

Variations in geo-environmental attributes differ strongly from those of urban anthropogenic structures. Similarly, these types of structures are self-directed and arranged and prone to abrupt process-related changes and modifications. Thus, there are many reasons why planned urbanization forms in association with disturbances in ecosystem mobility. The current research highlights these variations in the context of social–cultural assessments within the Jhelum River watershed, which strongly expresses urbanization structure development mechanisms. The climate ranges from semi-arid to subhumid subtropical and sub-mountainous climate, though the extreme temperatures may rise as high as 49.4°C in June and may drop as low as ?1.6°C in January. The rainfall is low in the southwest and gradually increases towards the northeast, whereas the Salt Range is the major topographic feature that controls climatic impacts and promotes sustainable development. Cross-disciplinary methods are adopted in this investigation to assess the social–ecological landscape system (SELS) in terms of its mobility and degree of urbanization. The Sustainable Development Goals of the 2030 Agenda recognize that human livelihoods and the management of natural resources cannot be addressed separately. Investing in the sustainability of mountain communities and ecosystem conservation and protection will provide benefits for humanity as a whole. It pertains to the commensurate development of the SELS and its response to interruptions. Thus, a reliable SWOT analysis for management approaches is introduced that may enable the development of competencies that promote and lead towards rapid improvements in the sustainability of retrograde urban infrastructure, including watersheds.     

珠江流域土壤中碳库的存量与通量

通过对珠江流域各主要环境介质中不同形态碳含量的分析和计算,得出该流域0~1.0m范围内土壤碳库的存量为1.36×1013kg,占中国陆地碳库总量的9.51%,全球碳库总量的0.907%;流域净碳输入量为4.141×1010kg/a,碳通量912.74kg/(hm2·a),初步计算表明珠江流域可能是陆地生态系统的一个碳汇区。另一方面,人类活动造成流域内有机碳的大量流失,其中,水土流失损失的碳8.01×109kg/a,植物收割及森林砍伐从土壤-植物系统中携带出的有机碳高达6.26×1011kg/a,这将造成土壤有机质含量的降低,因此促进陆地生态系统有机碳存储是提高本流域土地质量的关键。     

退耕土壤的碳、氮固存及其对CO2、N2O通量的影响

采样分析陇中黄土高原地区农田退耕种植苜蓿3 a、5 a、8 a后0～5、5～10、10～20 cm土层土壤有机碳(SOC)、全氮(TN)、活性有机碳(SAOC)及矿质氮(NO3-N、NH4-N)含/储量的变化,并用静态箱-气质联用法对样地的COO2、NO2O排放通量进行了测定,研究碳氮变化对土壤CO2、N2O排放通量的影响.结果表明:(1)SOC、TN基础含量很低的贫瘠土壤退耕后表现出明显的碳、氮固存效应,有很强碳、氮固存潜力.与未退耕休闲农田相比,退耕3 a、5 a、8 a后0～20 cm SOC储量分别提高了9.12%、20.18%、34.39%,SOC平均固存率分别为0.17、0.23、0.25mg/(hm2·a).TN储量在5～10、10～20 cm增加不明显,在0～5 cm退耕3 a、5 a、8 a后储量分别提高14.29%,35.71%和64.29%,各退耕年限0～20 cm TN平均固存率均为0.2 mg/(hm2.a);(2)退耕后各年限草地土壤活性有机碳(SAOC)含量有所增加,但各层含量变化不明显,其增加量远小于SOC的增加,说明退耕初期阶段积累了较多的土壤惰性碳;NO3-N含量增加明显,0～5、5～10 cm土壤各退耕年限含量达5%的显著性差异,但退耕前后NH4-N含量无明显变化.(3)土壤CO2通量与SOC含量、SAOC含量、TN含量及N2O通量显著正相关;N2O通量与SOC含量、矿质氮含量及CO2通量显著正相关.说明在环境因素稳定的条件下,退耕后土壤碳、氮含量的增加会导致CO2、N2O排放的加剧,表现出大气CO2、N2O的"源"效应.     

A simulation model for lead movement in a watershed

A simulation model of the movement and accumulation of automotively emitted lead in a watershed of Central Illinois is presented. The model is composed of four parallel terrestrial subsystems or zones based on traffic volume, and an aquatic system in series. The model is used to estimate historical accumulations of lead within the watershed and to compare different scenarios of reductions of lead emissions. Since the introduction of leaded gasoline an estimated 570, 000 kg of lead has been emitted in the watershed. Of this total about 36% remained airborne and left the watershed, and 3% left the watershed via the quatic system.Lead is found to be a significant pollutant in urban areas and near major highways. Without emission controls lead is expected to cause environmental problems after about 25 years.     

纳版河流域土地利用方式对土壤总有机碳以及活性有机碳的影响

近年来,不同土地利用方式下的土壤碳循环备受关注。土壤活性有机碳变化可以作为土壤碳变化的指示指标。文章以自然林、玉米地、水稻田、不同种植年限橡胶林土壤为研究对象,探讨了纳版河流域土地利用方式的改变对土壤总有机碳(TOC)、土壤微生物量碳(SMBC)、土壤可溶性总碳(DOC)、土壤易氧化碳(ROC)以及土壤颗粒有机碳(POC)在土壤中的质量分数及其分配比例的影响。结果显示:较之自然林(ck),玉米地的TOC、SMBC、DOC、ROC以及POC质量分数分别显著下降了35.04%、42.86%、42.33%、34.39%以及45.91%(P<0.05);水稻田的TOC、SMBC、DOC、ROC以及POC质量分数分别显著下降了38.46%、57.90%、58.56%、27.14%以及39.94%;1、5、10、15、20 a以及25 a橡胶林TOC以及SMBC质量分数均显著降低,TOC质量分数降幅分别为29.05%、24.78%、20.08%、20.08%、23.07%以及34.18%,SMBC质量分数降幅分别为53.44%、43.17%、66.68%、23.84%、30.96%以及27.25%;1、5、10 a以及15 a橡胶林DOC质量分数分别显著下降了47.24%、27.91%、71.35%以及21.77%;一年以及五年橡胶林ROC质量分数分别显著下降14.35%和22.81%;1、5、10、15、20 a以及25 a橡胶林POC质量分数分别显著下降了29.39%、38.54%、22.48%、22.42%以及23.71%;水稻田、1、5 a以及10 a橡胶林SMBC的分配比例显著降低了31.36%、34.16%、24.20%以及58.18%;水稻田、玉米地、1 a、5 a橡胶林DOC的分配比例显著降低了32.92%、11.55%、25.91%以及64.28%;玉米地以及5 a橡胶林POC的分配比例显著降低了16.74%以及18.29%。相关和回归分析表明:TOC与POC之间呈显著(P<0.05)正相关关系;SMBC与DOC之间呈极显著(P<0.01)正相关;ROC与POC之间极显著正相关;SMBC以及DOC均与土壤pH呈极显著的负相关关系;TOC、ROC以及POC均与土壤表层5 cm平均温度呈极显著负相关关系。土地利用方式由自然林向农用地(玉米地和水稻田)和橡胶林的转变降低了土壤的碳汇功能。     

Soil particle-size composition and coastal erosion and accretion study in Soc Trang mangrove forests

Coastal erosion results in loss of land, which impacts the economy, coastal residents and settlement plans, especially in the context of rising sea levels caused by climate change. Studying soil particle-size fractions in mangrove forests will help provide a better understanding of the relationship between soil proportions and coastal processes as well as the role of mangrove forests to support coastal planning and management. Soil samples were collected at 26 sampling plots at depths of 10 cm and 40 cm in the Cu Lao Dung (CLD), Long Phu (LP) and Vinh Chau (VC) mangrove forests in Viet Nam’s Soc Trang Province. The soil proportions based on six different particle-sizes (<0.074 mm, 0.074–0.1 mm, 0.1–0.25 mm, 0.25–0.5 mm, 0.5–1.0 mm, and >1.0 mm) were measured using a dry sieving method. Analysis showed that soil particle-sizes ranging between 0.074 and 0.5 mm made up 75–95 % of the soil sample weight at both depths. The high standard deviation values of soil proportions of each given particle-size among sampling plots indicated the soil proportions by particle-size varied widely across the sampling plots. Cluster analysis found similar pattern of soil particle-size proportions for samples collected in CLD and VC, and different pattern of soil particle-size proportions in samples collected at LP, which is more impacted by the Mekong River flow and has a thin mangrove forest belt.?Non-metric dimension scaling (NMDS) analysis showed that sampling plots across the landward sites of the three mangrove forest areas were distributed in the nearby locations (Stress?=?0.11). This indicated that soil proportions of particle-sizes of samples collected from areas of the natural forest composed of different species were more similar. Such similarities were not found, however, in samples collected from middle and seaward plots dominated by single-species plantations.     

南亚热带针阔混交林土壤热通量研究

运用土壤热通量板、常规微气象观测系统等设施对鼎湖山针阔混交林的土壤热通量和微气象因子进行了系统研究,结果表明,不同热通量板测值之间的差异可达10%以上。在中小时间尺度(≤1月)上,土壤热通量板上方土壤贮热均不能忽略,否则所测算的表层土壤热通量会产生较大误差,甚至发生热通量传递方向逆转的情况。5cm深度处和表层土壤热通量的日变化均呈“S”形,且前者相位后移0.5～1h。旱季土壤为热源而雨季为热汇,表层土壤年总热通量为-0.44MJ·m-2,说明就全年尺度而言,土壤是热源。表层土壤热贮量月变动范围为-0.14~0.20MJ·m-2,是5cm深度处土壤热通量的-11.0%~1.3%。表层土壤热通量月总值占净辐射的比例变动范围为-12.0%~3.3%,由于能量平衡大多在较小时间尺度上进行比较,故必须准确考察土壤热通量的变化,否则会极大地影响能量平衡。在0.5h尺度上,表层土壤热通量与2.5h前的冠层净辐射回归方程相关性最好,达极显著水平,说明鼎湖山针阔混交林土壤热通量对冠层净辐射的反馈要延滞约2.5h。     

Dissolved organic carbon concentrations and fluxes in forest catchments and streams: DOC-3 model

Dissolved organic carbon (DOC) concentrations in south-western Nova Scotia streams, sampled at weekly to biweekly intervals, varied across streams from about 3 to 40 mg L⁻¹, being highest mid-summer to fall, and lowest during winter to spring. A 3-parameter model (DOC-3) was proposed to project daily stream DOC concentrations and fluxes from modelled estimates for daily soil temperature and moisture, year-round, and in relation to basin size and wetness. The parameters of this model refer to (i) a basin-specific DOC release parameter “k_DOC^”, related to the wet- and open-water area percentages per basin, (ii) the lag time “τ” between DOC production and subsequent stream DOC emergence, related to the catchment area above the stream sampling location; and (iii) the activation energy “Ea”, to deal with the temperature effect on DOC production. This model was calibrated with the 1988-2006 DOC concentration data from three streams (Pine Marten, Moosepit Brook, and the Mersey River sampled at or near Kejimkujik National Park, or KNP), and was used to interpret the biweekly 1999-2003 DOC concentrations data (stream, ground and lake water, soil lysimeters) of the Pockwock-Bowater Watershed Project near Halifax, Nova Scotia. The data and the model revealed that the DOC concentrations within the streams were not correlated to the DOC concentrations within the soil- and groundwater, but were predictable based on (i) the hydrologically inferred weather-induced changes in soil moisture and temperature next to each stream, and (ii) the topographically inferred basin area and wet- and open-water area percentages associated with each stream (R² = 0.53; RMSE = 3.5 mg L⁻¹). Model-predicted fluxes accounted 74% of the hydrometrically determined DOC exports at KNP.     

Modeling seasonal course of carbon fluxes and evapotranspiration in response to low temperature and moisture in a boreal Scots pine ecosystem

Environmental conditions act above and below ground, and regulate carbon fluxes and evapotranspiration. The productivity of boreal forest ecosystems is strongly governed by low temperature and moisture conditions, but the understanding of various feedbacks between vegetation and environmental conditions is still unclear. In order to quantify the seasonal responses of vegetation to environmental factors, the seasonality of carbon and heat fluxes and the corresponding responses for temperature and moisture in air and soil were simulated by merging a process-based model (CoupModel) with detailed measurements representing various components of a forest ecosystem in Hyytiälä, southern Finland. The uncertainties in parameters, model assumptions, and measurements were identified by generalized likelihood uncertainty estimation (GLUE). Seasonal and diurnal courses of sensible and latent heat fluxes and net ecosystem exchange (NEE) of CO₂ were successfully simulated for two contrasting years. Moreover, systematic increases in efficiency of photosynthesis, water uptake, and decomposition occurred from spring to summer, demonstrating the strong coupling between processes. Evapotranspiration and NEE flux both showed a strong response to soil temperature conditions via different direct and indirect ecosystem mechanisms. The rate of photosynthesis was strongly correlated with the corresponding water uptake response and the light use efficiency. With the present data and model assumptions, it was not possible to precisely distinguish the various regulating ecosystem mechanisms. Our approach proved robust for modeling the seasonal course of carbon fluxes and evapotranspiration by combining different independent measurements. It will be highly interesting to continue using long-term series data and to make additional tests of optional stomatal conductance models in order to improve our understanding of the boreal forest ecosystem in response to climate variability and environmental conditions.     

Water and carbon fluxes above European coniferous forests modelled with artificial neural networks

Artificial neural networks are used to select a minimal set of input variables to model water vapour and carbon exchange of coniferous forest ecosystems, independently of tree species and without detailed physiological information. Neural networks are used because of their power to fit highly non-linear relations between input and output-variables. Radiation, temperature, vapour pressure deficit and time of the day showed to be the dynamic input variables that determine ecosystem water fluxes. The same variables, together with projected leaf area index are needed for modelling CO₂-fluxes. The results for the individual sites show that the neural networks found mean water and carbon flux responses to the driving variables valid for all sites. The sensitivity analysis of the derived neural networks shows that the LAI-effect of the CO₂-flux model is overfitted because of the low variability of LAI. However, the predictions of CO₂-fluxes of sites not included in the calibration set indicate that the LAI-response of the network is reliable and that results can be used as a first estimate of the net ecosystem carbon exchange of the forest sites. Independent predictions of forest ecosystem vapour fluxes were equally satisfying as empirical models specifically calibrated for the individual sites. The results indicate that both short term water and carbon fluxes of European coniferous forests can be modelled without using detailed physiological and site specific information.     

Land use change and nitrogen enrichment of a Rocky Mountain watershed.

Headwater ecosystems may have a limited threshold for retaining and removing nutrients delivered by certain types of land use. Nitrogen enrichment was studied in a Rocky Mountain watershed undergoing rapid expansion of population and residential development. Study sites were located along a 30-km transect from the headwaters of the Blue River to Lake Dillon, a major source of drinking water for Denver, Colorado. Ground water in residential areas with septic systems showed high concentrations of nitrate-N (4.96 +/- 1.22 mg/L, mean +/- SE), and approximately 40% of wells contained nitrate with delta15N values in the range of wastewater. Concentrations of dissolved inorganic nitrogen (DIN) in tributaries with residential development peaked during spring snowmelt as concentrations of DIN declined to below detection limits in undeveloped tributaries. Annual export of dissolved organic nitrogen (DON) was considerably lower in residential streams, suggesting a change in forms of N with development. The seasonal delta15N of algae in residential streams was intermediate between baseline values from undeveloped streams and stream algae grown on wastewater. Between 19% and 23% of the annual N export from developed tributaries was derived from septic systems, as estimated from the delta15N of algae. This range was similar to the amount of N export above background determined independently from mass-balance estimates. From a watershed perspective, total loading of N to the Blue River catchment from septic and municipal wastewater (2 kg x ha(-1) x yr(-1)) is currently less than the amount from background atmospheric sources (3 kg x ha(-1) x yr(-1)). Nonetheless, nitrate-N concentrations exceeded limits for safe drinking water in some groundwater wells (10 mg/L), residential streams showed elevated seasonal patterns of nitrate-N concentration and ratios of DIN to total dissolved phosphorus, and seasonal minimum concentrations of nitrate-N in Lake Dillon have increased exponentially to 80 microg/L over the last decade from an initial value near zero. Results suggest that isotopic ratios in autotrophs can be used to detect and quantify increases in N enrichment associated with land use change. The biotic capacity of headwater ecosystems to assimilate increases in inorganic N from residential development may be insufficient to prevent nitrogen enrichment over considerable distances and multiple aquatic ecosystems downstream.     

Modeling carbon sequestration under zero tillage at the regional scale. I. The effect of soil erosion

Zero tillage is recognized as a potential measure to sequester carbon dioxide in soils and to reduce CO₂ emissions from arable lands. An up-scaling approach of the output of the Environmental Policy Integrated Climate (EPIC) model with the information system SLISYS-BW has been used to estimate the CO₂-mitigation potential in the state of Baden-Württemberg (SW-Germany). The state territory of 35,742 km² is subdivided into eight agro-ecological zones (AEZ), which have been further subdivided into a total of 3976 spatial response units. Annual CO₂-mitigation rates where estimated from the changes in soil organic carbon content comparing 30 years simulations under conventional and zero tillage. Special attention was given to the influence of tillage practices on the losses of organic carbon through soil erosion, and consequently on the calculation of CO₂-mitigation rates. Under conventional tillage, mean carbon losses through erosion in the AEZ were estimated to be up to 0.45 Mg C ha⁻¹ a⁻¹. The apparent CO₂-mitigation rate for the conversion from conventional to zero tillage ranges from 0.08 to 1.82 Mg C ha⁻¹ a⁻¹ in the eight AEZ, if the carbon losses through soil erosion are included in the calculations. However, the higher carbon losses under conventional tillage compared to zero tillage are composed of both, losses through enhanced CO₂ emissions, and losses through intensified soil erosion. The adjusted net CO₂-mitigation rates of zero tillage, subtracting the reduced carbon losses through soil erosion, are between 0.07 and 1.27 Mg C ha⁻¹ a⁻¹ and the estimated net mitigation rate for the entire state amounts to 285 Gg C a⁻¹. This equals to 1045 Gg CO₂-equivalents per year with the cropping patterns in the reference year 2000. The results call attention to the necessity to revise those estimation methods for CO₂-mitigation which are exclusively or predominantly based on the measurements of differential changes in total soil organic carbon without taking into account the tillage effects on carbon losses through soil erosion.     

Empirical modeling of atmospheric deposition in mountainous landscapes.

Atmospheric deposition has long been recognized as an important source of pollutants and nutrients to ecosystems. The need for reliable, spatially explicit estimates of total atmospheric deposition (wet + dry + cloud) is central, not only to air pollution effects researchers, but also for calculation of input-output budgets, and to decision makers faced with the challenge of assessing the efficacy of policy initiatives related to deposition. Although atmospheric deposition continues to represent a critical environmental and scientific issue, current estimates of total deposition have large uncertainties, particularly across heterogeneous landscapes such as montane regions. We developed an empirical modeling approach that predicts total deposition as a function of landscape features. We measured indices of total deposition to the landscapes of Acadia (121 km2) and Great Smoky Mountains (2074 km2) National Parks (USA). Using approximately 300-400 point measurements and corresponding landscape variables at each park, we constructed a statistical (general linear) model relating the deposition index to landscape variables measured in the field. The deposition indices ranged over an order of magnitude, and in response to vegetation type and elevation, which together explained approximately 40% of the variation in deposition. Then, using the independent landscape variables available in GIS data layers, we created a GIS-relevant statistical nitrogen (N) and sulfur (S) deposition model (LandMod). We applied this model to create park-wide maps of total deposition that were scaled to wet and dry deposition data from the closest national network monitoring stations. The resultant deposition maps showed high spatial heterogeneity and a four- to sixfold variation in "hot spots" and "cold spots" of N and S deposition ranging from 3 to 31 kg N x ha(-1) x yr(-1) and from 5 to 42 kg S x ha(-1) x yr(-1) across these park landscapes. Area-weighted deposition was found to be up to 70% greater than NADP plus CASTNET monitoring-station estimates together. Model-validation results suggest that the model slightly overestimates deposition for deciduous and coniferous forests at low elevation and underestimates deposition for high-elevation coniferous forests. The spatially explicit deposition estimates derived from LandMod are an improvement over what is currently available. Future research should test LandMod in other mountainous environments and refine it to account for (currently) unexplained variation in deposition.     

燕山典型流域两种造林树种生态系统碳储量及固碳潜力研究

选择燕山典型流域6个林龄序列的小叶杨（Populus simonii）和5个林龄序列的山杏（Prunus sibirica）主要造林树种为研究对象,利用时间替代空间样地测量法量化退牧还林后生物量碳储量、凋落物碳储量和土壤碳储量及生态系统碳储量的变化规律,同时以各组成碳库-林龄序列中的最大碳储量之和作为生态系统饱和碳储量,以未退牧的天然草地生态系统碳储量作为初始植被类型的碳储量,分析总结了退牧还林对生态系统碳储量和碳循环的影响。结果表明,退牧还林后生态系统的生物量碳储量、凋落物碳储量基本随退牧年限的增加而增加,土壤碳储量随退牧年限的增加呈现先减小后增加的趋势。在没有人为干扰的情况下,9、15、18、22及29 a生小叶杨林的生态系统碳储量分别为7147.45、7461.67、7509.895、8468.375及8247.85 g·m^-2,9、15、18、22及26 a生山杏林的生态系统碳储量分别为6695.44、6700.82、8011.86、8001.92及7981.92 g·m^-2;9、15、18、22、29及36 a生小叶杨林的生态系统固碳潜力分别为757.08、1071.3、1119.53、2078.01、1857.48及1312.21 g·m^-2,9、15、18、22及26 a生山杏林的生态系统固碳潜力分别为310.45、1621.49、1611.55、1591.55及757.08 g·m^-2。长期来看,研究区退牧还林对提高生态系统碳汇能力是可观的、积极的。研究结果对提高造林对碳汇影响的估测能力提供数据支持,也为政府参与国际全球气候变化的谈判提供一个很好的案例研究和科学根据。     

Phenanthrene sorption to environmental black carbon in sediments from the Song-Liao watershed (China)

Black carbon (BC) in ten contaminated sediments from the Song-Liao watershed, NE China, was isolated upon treatments using a combustion method at 375°C, and the isolates’ sorption isotherms for phenanthrene (Phen) were determined. All sorption isotherms were nonlinear and fitted well by the Freundlich model. A negative relation was found between Freundlich sorption nonlinearity parameter (n values) and BC/total organic carbon (TOC) content of the original sediments (r²=0.687, p<0.01), indicating the dominance of BC in Phen sorption nonlinearity. The BC isolates from this industrialized region had n values of 0.342 to 0.505 and logK_FOC values of 6.02 to 6.42(μg·kg⁻¹·OC⁻¹)/(μg·L⁻¹) ⁿ for Phen. At a given C_e, the BC had higher K_oc value than the original sediments, revealing a higher sorption capacity for BC. BC was responsible for 50.0% to 87.3% of the total sorption at C_e=0.05 S_w, clearly indicating the dominance of BC particles in overall sorption of Phen by sediments.