Contribution of increasing CO2 and climate to carbon storage by ecosystems in the United States

The effects of increasing carbon dioxide (CO2) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895-1993 were modeled with new, detailed historical climate information. For the period 1980-1993, results from an ensemble of three models agree within 25%, simulating a land carbon sink from CO2 and climate effects of 0.08 gigaton of carbon per year. The best estimates of the total sink from inventory data are about three times larger, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO2 and climate. The modeled sink varies by about 100% from year to year as a result of climate variability.     

云杉人工林材性变异的初步研究

研究了云杉人工林主要材性指标与林龄、海拔梯度及林木等级间的关系，比较了人工林与６０～１００年天然林主要材性指标的差异。结果表明，１５，２０和３０年人工林主要材性指标差异不显著；不同林分密度人工林纤维长宽比差异显著；不同海拔梯度人工林及不同林木等级间基本密度差异显著。人工中幼林与天然林主要材性指标差异不明显，均是优良纸浆原料。初步认为云杉纸浆材培育周期为２５年。     

Beyond deforestation: restoring forests and ecosystem services on degraded lands

Despite continued forest conversion and degradation, forest cover is increasing in countries across the globe. New forests are regenerating on former agricultural land, and forest plantations are being established for commercial and restoration purposes. Plantations and restored forests can improve ecosystem services and enhance biodiversity conservation, but will not match the composition and structure of the original forest cover. Approaches to restoring forest ecosystems depend strongly on levels of forest and soil degradation, residual vegetation, and desired restoration outcomes. Opportunities abound to combine ambitious forest restoration and regeneration goals with sustainable rural livelihoods and community participation. New forests will require adaptive management as dynamic, resilient systems that can withstand stresses of climate change, habitat fragmentation, and other anthropogenic effects.     

河川径流年内分配不均匀性的量化研究

提出了一种河川径流年内分配不均匀性的定量化方法。该方法以年内各时段平均流量的均方差与年平均流量的比值作为径流年内分配的不均匀系数 ,用标准的统计量定量描述径流年内分配的不均匀性 ;通过实例分析了不均匀系数的变化规律 ;探讨了将不均匀系数作为水资源决策指标的可能性     

Improved surface temperature prediction for the coming decade from a global climate model

Previous climate model projections of climate change accounted for external forcing from natural and anthropogenic sources but did not attempt to predict internally generated natural variability. We present a new modeling system that predicts both internal variability and externally forced changes and hence forecasts surface temperature with substantially improved skill throughout a decade, both globally and in many regions. Our system predicts that internal variability will partially offset the anthropogenic global warming signal for the next few years. However, climate will continue to warm, with at least half of the years after 2009 predicted to exceed the warmest year currently on record.     

岷江上游油松人工林对降水的截留分配效应

为了评估人工油松林的水源涵养服务功能 ,选择岷江上游典型的 2 3年生油松人工林 ,定位监测了冠层对 1年中共 136次降水事件的截留分配效应 .观测期降水总量为 80 5 8mm ,林冠截留、茎流和穿透水量分别是 2 97 892、6 7 771和 4 4 0 137mm ,林冠截留率、茎流率、穿透率分别为 36 97%、8 4 1%、5 4 6 2 % .林外降水量大于 0 3mm时才观测到林内穿透雨 ,而大于 2 8mm时 ,才观测到树干茎流 .林冠对降水的截流分配与降水量、降水形态以及林分特征密切相关 .冠层截留量、茎流量和穿透量与降水量均呈显著的线性正相关 ,但冠层截留率与降水量呈对数负相关 ,而茎流率和穿透率呈对数正相关 ;林冠对降雪的截留强于降雨 ,而降雨的穿透量强于降雪 .同一降水事件下树干茎流量随着胸径的增大而增加 .松针自身吸水对降水有一定的截流分配作用 .综合分析表明 ,岷江上游 2 3年生油松人工林较其他油松林林冠对降水有更好的截留率 .     

基于气候年型的河南省冬小麦产量预测

气候变化是影响小麦产量的重要因素,因此科学划分气候年型,对于准确预测小麦产量至关重要。利用河南省15个气象站点（市、县）1984—2018年的温度数据划分暖温年、平温年、冷温年,依据降雨数据划分湿年、平水年、干年,组合成9种气候年型并分析其规律;结合小麦产量数据划分出丰产年、平产年、低产年,分析气候年型和产量年型的关系。然后结合地形土壤、气象等因素把河南划分为豫北麦区、豫中东部麦区、豫西麦区、豫南麦区和南阳盆地5个麦区。在此基础上,利用HP滤波法分离出气象产量和趋势产量,以气象因子驱动并利用BP神经网络构建模型预测气象产量,利用一元线性回归模型建模得到趋势产量,把两者产量叠加得出实际产量,从而实现小麦产量的预测。结果表明：河南省积温年型以暖温年、正常年型为主,降雨年型分布比较均匀,气候年型中以正常年和干年为主,暖湿年小麦高产频率最高,为76.9%,冷湿年小麦低产频率最高,为67.9%;积温是影响小麦产量波动的主要因素,暖年年型下小麦更容易丰产,冷年时小麦低产概率较高;利用气象产量和趋势产量分别建模叠加得出的小麦产量和实际产量相比,豫北、豫中东、豫西、豫南和南阳盆地五大麦区各模型的平均相对误差分别为0.31%、0.36%、0.58%、0.48%、0.38%,说明利用HP滤波和BP神经网络技术预测小麦产量是可行的。     

雷竹保护地栽培林分立竹结构的初步研究

在浙江省临安市高虹镇、东天目乡调查的４４个样地材料表明：竹林的平均立竹度为１．７万株·ｈｍ－２,变异系数为３１．１％,各样地间立竹度变异极大;连续实施覆盖栽培时间越长,竹林开花越严重,覆盖３ａ或３ａ以上竹林高达１１％的立竹开花。为使覆盖栽培竹林具有良好的竹林结构,保持雷竹的持续丰产,应采用２ａ覆盖１ａ休闲的方法留养母竹,覆盖年份少留养,休闲年份多留养,并使雷竹立竹度保持在１．６５万株·ｈｍ－２左右。     

耕作干扰下喀斯特土壤有机碳损失主要途径及其影响因素

西南喀斯特生态系统原生土壤有机碳(SOC)含量较高,但在开垦后急剧损失,然而目前对SOC损失过程、途径和机制仍缺乏充分认知。本研究基于不同频率翻耕处理(分别隔6、4、2、1个月翻耕一次,以免耕为对照)的原位控制试验,以土壤团聚体为切入点,通过对土壤CO_2排放和可溶性有机碳(DOC)淋失通量进行为期一年的连续监测,探讨了SOC损失的主要途径及其影响因素。结果发现:翻耕导致表层(0～10 cm)土壤SOC和5～8 mm粒级团聚体显著降低;一年后,各翻耕处理平均损失15.4%～27.6%的SOC,土壤DOC淋失量仅占SOC损失量的0.05%～0.10%,而土壤以CO_2形式释放的碳占SOC损失总量的22.7%～35.5%,是土壤碳损失的重要途径之一;SOC损失量与Ca~(2+)、Mg~(2+)淋失总量均呈显著正相关,说明在岩溶作用下以HCO_3-形式淋失是SOC损失的另一重要途径;土壤CO_2排放速率与5～8 mm粒级团聚体含量呈显著负相关,说明翻耕干扰导致5～8 mm团聚体崩解、受团聚体保护的闭蓄态SOC释放后迅速矿化是喀斯特SOC损失的主要机制。     

2010年大同市主要天气气候事件及特征

2010年,大同市年平均气温较常年偏高0.2℃,春季气温为1971年以来历史同期次低值,夏季气温为次高值;年降水量418.9mm,比常年偏多5%,秋季降水量为1971年以来历史同期第二多。年内,极端天气气候事件频发,多项气象要素突破极值。冬春季持续低温致春播延期、作物发育推迟;夏季全市高温破历史纪录,阶段性干旱明显,局地冰雹及洪涝灾害偏多;秋季连阴雨天气造成涝灾及作物贪青晚熟,春季全市出现大范围大风沙尘天气,给社会经济和人民生活带来较大的损失和影响,其中干旱、冰雹及洪涝造成的损失较为严重。     

浙江红壤区经济林坡地氮素径流流失特征研究

以浙江省永康市方山柿经济林坡地为试验区,依据不同地形条件及林下管理措施,设置7个径流小区和沉砂池,定期采集沉砂池水样,测定径流中不同形态氮素浓度。通过为期一年的监测分析,得到如下结论:(1)试验区氮素流失与水文年内降水具有明显的同步性,氮素流失多发生在降水集中的梅雨和台风季节。这两个季节的降水量占全年降水的66.2%,TN、NO-3-N和NH+4-N流失量分别占全年总流失量的80.3%、78.2%和83.0%。(2)坡顶、凸坡和凹坡径流小区的氮素流失符合养分流失的"临界坡度"规律,临界坡度在坡顶(10.22°)与凹坡(18.55°)之间。水文年内TN和NO-3-N流失量关系为坡顶凹坡凸坡,NH+4-N流失量关系为凹坡坡顶凸坡。三种地形径流小区的年内氮素累积流失量均呈幂函数型增加。(3)对照林下管理措施不同的6号(林下除草)和7号(林下不除草)径流小区,发现草被覆盖对减少经济林坡地氮素径流流失具有明显效果。保留草被覆盖的7号小区比除草的6号小区的TN、NO-3-N和NH+4-N径流流失分别减少了22.1%、36.2%和44.1%。     

窟野河流域河川基流量变化趋势及其驱动因素

河川基流量的变化是区域气候变化与人类活动的综合反映,其对维持生态系统健康具有重要的意义.以黄土高原水蚀风蚀交错区典型流域窟野河流域为研究对象,利用1959-2005年实测水文、气象资料,基于Chapman-Maxwell数字滤波法的基流量计算,分析窟野河流域河川基流量的变化趋势与演变特征,从气候变化和人类活动两方面探讨了河川基流量变化的驱动因素.结果表明:(1)近50年来,流域内7个时段(全年;春季、夏季、秋季、冬季;汛期、非汛期)的基流量均表现为极显著减少趋势,全年基流量的减少量为0.628 mm/a,并在1980和1996年发生两次明显的突变;(2)与基准期(1959-1979年)相比,水土保持效应期(1980-1995年)的全年日基流量在5％,50％和95％的频率上相对减少率分别为30％,38％和54％,煤炭开发期(1996-2005年)的全年日基流量在5％,50％和95％的频率上相对减少率分别为57％,68％和100％;(3)流域河川基流量减少是气候变化和人类活动共同作用的结果,降水量的变化一定程度影响基流量,但主要驱动因素是流域内大面积连片开采煤炭资源和过量开发利用地下水.     

Arbuscular mycorrhizal fungi increase organic carbon decomposition under elevated CO2

The extent to which terrestrial ecosystems can sequester carbon to mitigate climate change is a matter of debate. The stimulation of arbuscular mycorrhizal fungi (AMF) by elevated atmospheric carbon dioxide (CO(2)) has been assumed to be a major mechanism facilitating soil carbon sequestration by increasing carbon inputs to soil and by protecting organic carbon from decomposition via aggregation. We present evidence from four independent microcosm and field experiments demonstrating that CO(2) enhancement of AMF results in considerable soil carbon losses. Our findings challenge the assumption that AMF protect against degradation of organic carbon in soil and raise questions about the current prediction of terrestrial ecosystem carbon balance under future climate-change scenarios.     

Global warming and marine carbon cycle feedbacks on future atmospheric CO2

A low-order physical-biogeochemical climate model was used to project atmospheric carbon dioxide and global warming for scenarios developed by the Intergovernmental Panel on Climate Change. The North Atlantic thermohaline circulation weakens in all global warming simulations and collapses at high levels of carbon dioxide. Projected changes in the marine carbon cycle have a modest impact on atmospheric carbon dioxide. Compared with the control, atmospheric carbon dioxide increased by 4 percent at year 2100 and 20 percent at year 2500. The reduction in ocean carbon uptake can be mainly explained by sea surface warming. The projected changes of the marine biological cycle compensate the reduction in downward mixing of anthropogenic carbon, except when the North Atlantic thermohaline circulation collapses.     

Can food security and low carbon be achieved simultaneously? —An empirical analysis of the mechanisms influencing the carbon footprint of potato and corn cultivation in irrigation areas

Irrigated agriculture has tripled since 1950, accounting for 20% of the global arable land and 40% of food production.  Irrigated agriculture increases food security yet has controversial implications for global climate change.  Most previous studies have calculated carbon emissions and their composition in irrigated areas using the engineering approach to life-cycle assessment.  By combining life cycle assessment (LCA)-based carbon emissions accounting with econometric models such as multiple linear regression and structural equation modeling (SEM), we conducted an interdisciplinary study to identify the influencing factors and internal mechanisms of the carbon footprint (CFP) of smallholder crop cultivation on irrigation reform pilot areas.  To this end, we investigated corn and potato production data in the 2019–2020 crop years for 852 plots of 345 rural households in six villages (two irrigation agriculture pilot villages and four surrounding villages as controls) in Southwest China.  The crop CFP in the irrigation agriculture pilot areas was significantly lower than in non-reform areas.  Irrigation reforms mainly impacted the crop CFP through four intermediary effects: the project (implementation of field irrigation channels), technology (improving adoption of new irrigation technologies), management (proper irrigation operation and maintenance), and yield effects.  All effects inhibited the CFP, except for the project effect that promotes carbon emissions.  Among them, yield increase has the greatest impact on reducing CFP, followed by management and technology effects.  Furthermore, planting practices, individual characteristics, and plot quality significantly impacted the crop CFP.  This study has policy implications for understanding the food security–climate nexus in the food production industry.     

烟台市气候变化及其对旅游业影响分析

为了定量分析烟台市气候改变对旅游行业的影响,采用气候倾向率方法,分析了烟台市近年来的气候改变特征;运用气候舒适度评价方式,分析了烟台市天气舒适的等级状况;运用相关性统计方法,进一步分析了气候舒适度和旅客线上关注度的关联程度。通过分析得到结果：烟台市年均降水、相对湿度和风速为逐年下降变化倾向,倾向率依次为：5.77 mm/(10 a)、0.56%/(10 a)、0.25 m/(s ·10 a),年均气温以1.18℃/(10 a)倾向率上升;烟台市以5、6、9、10 月为最佳旅游期;以4、7、8、11 月为适宜旅游期;以1、2、12月为不适宜旅游期;烟台市气候的舒适度和旅客线上的关注度呈显著关系,关联系数为0.986,气候的弹性系数为0.128%。研究表明,烟台市近年来气候要素在逐年变化,气候舒适度对旅游业有显著影响作用,烟台市旅游气候舒适度参数每改变1个单位,旅客线上关注度月指数就会增长或降低0.128%。     

Groundwater: Flow Toward an Effluent Stream

Hydrodynamic, topographic, and geologic factors control flow of groundwater toward an effluent stream. Features of such flow are illustrated by a hydraulic model that simulates the stream and surrounding consolidated rocks. Colored ink in the flow system marks progress toward the stream. Visual analysis shows that groundwater moves into the effluent stream along curvilineal flow lines. The total head of groundwater beneath the stream increases with depth.     

广西LUCC过程与气候波动对农田生产潜力的影响

【目的】分析近20年广西土地利用／土地覆盖变化（Land Use and Land Cover Change,LUCC）过程与气候波动对农田生产潜力的影响。【方法】基于20世纪80年代末至2010年的5期土地利用遥感监测数据,分析近20年广西耕地资源的变化过程;结合1990～2010年的逐日气象资料,采用环境因子逐步订正方法估算农田生产潜力。【结果】根据遥感监测结果,近20年广西耕地面积净减少了20843．81ha。在1990～2010年平均气候条件下,广西林地变耕地动态对农田生产潜力总值增加贡献最大,占新开垦耕地农田生产潜力总值的80．73％;耕地变建设用地动态使农田生产潜力总值减少最多,占流失耕地农田生产潜力总值的74．39％。当耕地保持20世纪80年代末状态不变时,气候波动使1990-2010年广西水田生产潜力均值变化总体上呈上升趋势,但旱地生产潜力均值变化总体上呈下降趋势。【建议】广西新开垦耕地的农田生产潜力不及流失耕地的农田生产潜力,优质耕地面积减少。因此要求在强调耕地占补平衡的同时,注重耕地质量的平衡,一方面要防止优质耕地面积的减少,另一方面要通过改土改水、节水灌溉等措施提高粮食综合生产能力,弥补由优质耕地减少和气候变化给粮食产量带来的损失。     

岩溶地区开挖隧道对水资源的影响--以渝合高速公路隧道为例

中梁山位于重庆市的近郊区,是净化城区污染空气,调节主城区气候环境的重要地带。渝合高速公路隧道横穿中梁山,破坏了地下水的循环过程,引起泉水和地表水的枯竭。水源枯竭面积7.2 km2。隧洞每年渗漏水量283.9万m3,有21个泉(井)受到影响,其中17个泉(井)完全干枯,有5口堰塘全年都无水可蓄。造成4个自然村、748户居民、2 247人失去了饮用水,143 hm2耕地失去灌溉用水。     

Carbon pools and flux of global forest ecosystems

Forest systems cover more than 4.1 x 10(9) hectares of the Earth's land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 +/- 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 +/- 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 +/- 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.