土壤表层CO_2的释放与土壤水分波动

贵州虽地处雨量充沛、气候潮湿的亚热带,但近年来旱地土壤往往出现明显的干湿循环现象,这是因为：１）森林植被遭到破坏,使其对气候的调节功能大不如前,导致出现多年气候异常,最大的年降雨量与最小的年降雨量之间相差５００ｍｍ以上,旱涝灾害频繁;２）喀斯特地貌土...     

Distribution patterns of SOC/TN content and their relationship with topography,vegetation and climatic factors in China’s north-south transitional zone

Journal of Geographical Sciences - The spatial distributions and variation mechanism of key soil indices in the Qinling-Daba Mountains are important indicators for the identification of the...     

模拟气候变化和CO2增加对高寒草原土壤有机碳的影响

本研究的1／1标是利用CENTURY模型分析气候变化、大气CO2浓度倍增、气候变化与大气CO2浓度倍增共同作用对藏北高原高寒草原土壤有机碳的影响。结果表明：未来50年不同气候变化情景下土壤表层（0-20cm）有机碳呈降低趋势,变化率为49．77％-52．36％。P1T0情景（降水增加．温度不变）、POT1情景（降水不变,温度增加）和P1T1情景（降水增加,温度增加）下的模拟结果相近。其中P1T1情景下高寒草原土壤有机碳损失的最多（模拟结束时的土壤有机碳为844．40gCm^-2）,POT1情景下土壤有机碳损失49．77％。相对CO2不变情景而言,CO2倍增情景下土壤有机碳增加12．87％。CO2增加对土壤有机碳的影响大于气候变化单独作用对土壤有机碳的影响。气候变化与大气CO2浓度倍增共同作用导致土壤有机碳降低。未来50年P1T1＋2×CO2情景下土壤有机碳降低52．39％,POT1＋2×CO2情景下土壤有机碳降低49．81％,P1T0＋2×CO2情景下土壤有机碳降低52．317）％。因此,高寒草原土壤有机碳含量随降水、温度和大气CO2浓度的变化而变化。     

Characteristics of carbonaceous aerosol in a two-week campaign at Ny-lesund

The concentrations of organic carbon(OC)and elemental carbon(EC)in total suspended particle(TSP)were investigated at Ny-Alesund,Svalbard in atwo-week campaign.The levels of OC and EC are 0.86±0.27μgm~(-3)(mean±standard deviation)and 0.19±0.10μgm~(-3),respectively.Back trajectory analy-sis of air masses arriving at Ny-lesund reveals that long-range transport of pol-luted air play insignificant role in OC and EC levels,to which the potential influ-ence of the local contamination were ascribed.The average OC/EC ratio is 5.41,suggesting the presence of the secondary organic aerosols.The estimated second-ary organic carbon(SOC)in TSP is 0.59μg/m~3,accounting for 64% of the totalorganic carbon.     

Age-related changes of carbon accumulation and allocation in plants and soil of black locust forest on Loess Plateau in Ansai County,Shaanxi Province of China

The effects of reforestation on carbon(C) sequestration in China′s Loess Plateau ecosystem have attracted much research attention in recent years. Black locust trees(Robinia pseudoacacia L.) are valued for their important use in reforestation and water and soil conservation efforts. This forest type is widespread across the Loess Plateau, and must be an essential component of any planning for C sequestration efforts in this fragile ecological region. The long-term effects of stand age on C accumulation and allocation after reforestation remains uncertain. We examined an age-sequence of black locust forest(5, 9, 20, 30, 38, and 56 yr since planting) on the Loess Plateau to evaluate C accumulation and allocation in plants(trees, shrubs, herbages, and leaf litter) and soil(0–100 cm). Allometric equations were developed for estimating the biomass of tree components(leaf, branch, stem without bark, bark and root) with a destructive sampling method. Our results demonstrated that black locust forest ecosystem accumulated C constantly, from 31.42 Mg C/ ha(1 Mg = 10~6 g) at 5 yr to 79.44 Mg C/ha at 38 yr. At the ′old forest′ stage(38 to 56 yr), the amount of C in plant biomass significantly decreased(from 45.32 to 34.52 Mg C/ha) due to the high mortality of trees. However, old forest was able to accumulate C continuously in soil(from 33.66 to 41.00 Mg C/ha). The C in shrub biomass increased with stand age, while the C stock in the herbage layer and leaf litter was age-independent. Reforestation resulted in C re-allocation in the forest soil. The topsoil(0–20 cm) C stock increased constantly with stand age. However, C storage in sub-top soil, in the 20–30, 30–50, 50–100, and 20–100 cm layers, was age-independent. These results suggest that succession, as a temporal factor, plays a key role in C accumulation and re-allocation in black locust forests and also in regional C dynamics in vegetation.     

Carbon fluxes in soil: long-term sequestration in deeper soil horizons

Terrestrial ecosystems represent the second largest carbon reservoir, and the C balance in terrestrial ecosystems can be directly impacted by human activities such as agricultural management practices and land-use changes. This paper focuses on the C-sequestration in soil. Although many studies showed that the concentration of SOC is much higher in the shallow soils (0-30 cm), the deeper horizons represent a much greater mass of soil and represent a huge C-storage pool. The process of preferential retention of more strongly adsorbing components, along with competitive displacement of weakly binding components are the key processes that enhance the movement of organic carbon to deeper soil horizons. DOC represents the most dynamic part of organic carbon in soils, and thus can be used as a timely indicator of the short-term change of C-sequestration. Long-term experiments have demonstrated that higher SOC levels in shallow soils would lead to increased fluxes of DOC to deeper horizons, but more data on a wider range of soils and treatment strategies are needed to fully evaluate the linkages between changes in SOC in shallow soil, vertical fluxes of DOC to deeper soil horizons, and enhanced C-inventories in deeper, slow-turnover SOC pools.     

中国南北过渡带土壤碳氮空间特征及暖温带与亚热带界限

秦巴山区是中国南北过渡带的主体,过渡带分界划分在学界一直存在争议,确定和改进划分指标对构建中国生态地理格局有重要作用。土壤作为过渡带的核心部分,其关键指标的空间分布及变异机制对识别过渡效应和区域特征有指示作用。本文基于土壤二普资料,采用空间模拟和地统计方法分析土壤有机碳/全氮空间特征及与主要自然地理要素的关系。结果显示,秦巴山区有机碳/全氮含量空间分布趋势一致,存在3个高值区、1个次高值区和1个低值区。高值区分布在秦岭、大巴山高海拔区域和嘉陵江以西山地,含量分别为15.03~71.04 g/kg、1782.61~7710.00 mg/kg;低值区沿秦岭北坡的渭河谷地、南五台山和伏牛山分布,含量分别为0.64~6.50 g/kg、110.00~885.96 mg/kg;次高值区主要在汉江两侧、秦巴山地之间海拔< 1000 m及嘉陵江两侧略高于1000 m的山体,含量介于以上二者之间,自西向东呈南北向宽幅逐渐增大的“喇叭状”趋势。综合考虑地形—植被—气候作用,发现秦岭南坡—大巴山北坡有机碳/全氮次高值区分布范围与1000 m等高线、暖温带落叶阔叶林带（含常绿成分）和亚热带常绿落叶阔叶混交林带上限、1月0 ℃等温线、7月24 ℃等温线较一致,区内1月、7月、季节和全年气温变化较小,各季降雨变幅大,该区是亚热带向暖温带过渡的主体,北界大致沿都江堰—茂县—平武—文县和秦岭南坡1000 m等高线分布,南以都江堰—北川—青川和大巴山北坡1000 m等高线为界。有机碳/全氮空间变化为亚热带—暖温带的划界提供一定依据,进一步识别典型区土壤过程及生态效应,将全面揭示土壤多维过渡特征及其变异机理。     

南亚热带森林植被恢复演替中土壤有机碳组分及其稳定性

以鼎湖山森林植被恢复演替过程中的松林(初期)、混交林(中期)和季风林(后期)为研究对象,通过测定其土壤总有机碳(TOC)、易氧化有机碳(ROC)和不易氧化有机碳(NROC)及凋落物13C-NMR分析,以期阐明森林植被恢复演替过程中土壤有机碳组分变化规律及其原因。结果表明:(1)3个森林土壤ROC含量差异不显著;由松林向季风林演替过程中,ROC占TOC的比例下降。松林新鲜凋落物层的烷氧基碳含量(57.03%)高于季风林(49.10%)和混交林(54.50%)。(2)3个森林土壤NROC含量差异显著,大小顺序为:季风林混交林松林。混交林和季风林凋落物半分解层和已分解层的惰性指数明显高于松林。TOC趋势与NROC一致。南亚热带森林由松林向季风林恢复演替过程中,土壤有机碳的稳定性增加,惰性有机碳的持续积累可能是季风林和混交林土壤TOC积累的一个重要过程。     

北极圈数据库及为何需要

Many factors, such the great changes of temperature, which will be expected at the high latitudes, increased pressure from humans to extract the natural resources in cold regions, seriously affect the cold environment. Many meetings have been held about the classification of cold soils, ideas and concepts of cold soils. These facilitate the need for developing a database of soils of the circumpolar region. The database can help offering information for potential problems in cold regions and for selecting the best areas for placement of new road and towns.     

扰动强度递增斜坡动力学演变规律的振动台试验

“5.12”汶川大地震和“4.20”芦山地震均触发了大量的崩塌、滑坡。实震资料显示,不同地震烈度区地震触发崩塌滑坡规模的整体分布规律会发生变化。这一统计层面的认知亟待得到物理试验的验证。在自组织临界状态理论的概念框架下,开展了振动台砂堆模型试验。试验表明：输入地震波峰值加速度（PGA）为0.075g～0.125g时,落砂量与发生频率的关系可用幂律描述;PGA增加到0.15g～0.25g时,该关系服从对数正态分布;PGA增加到0.35g～0.45g时,该关系具有正态分布特征。元胞自动机模拟试验结果表明,随扰动强度增加,砂堆模型的动力学特性也经历了幂律-幂律弱化-正态分布的演变过程。按照物理学中的普适性原理,汶川、芦山地震Ⅸ度区崩塌滑坡规模与出现频率之间所呈现负幂律分布的现象,以及汶川地震Ⅺ度区所呈现的对数正态分布,可能是具有普适性意义的规律。这些认识可望为不同烈度区地震触发崩塌滑坡灾势预测提供科学依据。