高纬度多年冻土物理力学性质研究

冻土具有相变性、流变性和蠕变性等特点,其工程性质异常复杂多变。为确保多年冻土地区公路路基的稳定性,就要了解地表下多年冻土的物理力学性质。依托《漠大线伴行路多年冻土地区路基及桥梁建设关键技术》项目,选取典型冻土路段对路基下多年冻土进行取样,通过室内土工试验分别测定冻土的总含水率、密度、颗粒分析、液塑限、比重、抗剪强度、抗压强度等指标,并对试验结果进行分析。得出:随着深度的增加冻土含水率呈现下降趋势,冻土的密度随着含水率的增加而减小;未冻水和冰对冻土抗剪强度影响显著,总含水率低的冻土抗剪强度高;富冰冻土总含水率超过土体饱和状态的含水率,冻土抗压强度随着总含水率增加而降低。进而为大兴安岭多年冻土地区修建公路和路基沉降变形病害分析提供可靠的理论参考。     

寒区公路路基阻水防渗技术研究

本文通过对大兴安岭多年冻土地区公路路基融沉原因的分析、提出了采用塑编袋装填粘土的保温阻水防渗技术。通过生产性试验,并经五年长期监测,证实路基处于稳定状态。     

大兴安岭南瓮河湿地多年冻土活动层地温研究

【目的】本文利用黑龙江嫩江源森林国家生态系统定位观测研究站冻土观测场2012-2013年冻土活动层与土壤热通量观测资料,分析了大兴安岭南瓮河湿地多年冻土活动层地温变化规律,以期为大兴安岭地区冻土观测研究提供合理的科学依据。【方法】用地温传感器(109,CSI,USA)和土壤含水量传感器(CS616,CSI,USA)分别测量不同深度(5、10、20、30、40、50、60、70、80、100、120、140、160、180 cm)土壤温度和土壤体积含水量;用空气温湿度传感器(HMP45C,Vaisale,USA)测量地上150 cm处空气温度和相对湿度;用土壤热通量(HFP01SC,Hukseflux,USA)测量5和10cm深度的土壤热通量。通过数据采集器(CR1000,Campbell,USA)采集,每10 min自动记录一次平均值。【结果】多年冻土活动层地温与气温的变化规律相一致,气温对土壤温度的影响具有一定的时滞,滞后时间随着土壤深度的增大而增大;在整个年度冻融循环中,土壤各层都经历降温、开始冻结、完全冻结、升温、开始融化、完全融化的过程。不同深度开始冻结的时间相差不大,但融化时间相差较大,在冻融循环中,冻结过程耗时明显小于融化过程;多年冻土活动层土壤热通量与表层温度均呈现周期性变化。在表层冻结过程中,土壤热通量变化剧烈,完全冻结全变化趋于平缓。【结论】通过研究南瓮河湿地多年冻土活动层地温的动态变化,对该区冻土活动层地温变化过程及规律有了初步了解,为进一步研究湿地冻土奠定基础。     

古莲河露天煤矿采坑内冻土环境对开采活动的影响

古莲河露天煤矿从1991年投入生产以来,由于在大片连续多年冻土区内进行露天采煤活动。使多年冻土发生退化,对开采活动产生了不利的影响。如何减小多年冻土对开采所带来的不利影响,本文从多年实践经验出发对其进行论述。     

多年冻土退化及其趋势初步评估综述

多年冻土分布在广大寒区,该区的生态系统是一个对环境极为敏感的系统。受气候变暖和人为活动的共同影响,过去的几十年中已发生了不同程度的变化,随着人类活动的增强,变化必将加剧,冻土问题也将显得日益突出。文章介绍了冻土的分布,冻土退化的特征,冻土退化对生态系统产生的影响,以及在全球变化条件下,对未来冻土变化趋势的评估。     

基于土体冻结理论在地铁施工中的应用

针对南方某些富水地层下的地铁施工问题,结合某地铁联络道冻结法施工的工程实例,采用低温盐水冻结法对富水地层进行冻结施工,分析了该案例中冻结施工所需要的设备、施工方案的确定以及监控量测的作用。结果表明:在冻结时间40d前后土体开始交圈,冻胀压力开始降低;50d后冻结壁厚度1.8m,土体平均温度-10℃,满足冻结指标,成功解决了由于地铁施工中土壤含水率较大而无法正常进行加固的问题。同时由于该工法对土壤加固属于临时加固且土体本身存在冻胀融沉现象,建议今后的研究重点放在此问题的防治措施上。本文案例中地铁联络道冻结法的成功应用,可供类似地下工程进行参考,具有一定的借鉴意义。     

小兴安岭冻土工程地质性质及勘察要点

季节冻土的冻胀性,多年冻土的融沉性对工程建设危害程度很大,小兴安岭又是冻土的多发区域,因此详细了解和认真研究冻土工程地质的性质以及冻土的勘察要点对冻土工程地质勘察是十分重要的,本文仅就小兴安岭多年的冻土勘察经验提出自已的理解和认识。     

季冻区边坡表层粉质粘土力学指标影响因素室内试验研究

本文通过室内三轴试验研究冻融作用下边坡表层粉质粘土土体随含水量、密实度、冻融次数、是否存在植物根系等不同条件下土的力学指标变化规律,对提高季冻区边坡防护效果具有一定的理论指导意义。研究结果表明:(1)土体主应力差在植物根系作用下明显提高,在含水率13%左右提高明显;加根土主应力差随土的密实度增加而显著提高。(2)含水率较小时,土体黏聚力随含水率的增加而增大,当含水率在13%左右时,黏聚力最大,当含水率大于13%后,黏聚力开始随含水率增加而减小。植物根系作用下粘聚力随土体密实度增加而增大。(3)随含水率增加土体内摩擦角减小,含水率越大内摩擦角减小幅度越大。含水率较大时植物根系对土体内摩擦角影响较小;含水率较小和密实度较大时植物根系对提高土内摩擦角作用明显。     

关于我国北部寒温带冻土森林可持续发展问题及对策的商榷

大兴安岭自开发建设以来,由于森林火灾、森林采伐及各种人为对森林的破坏,再加之气候变暖多种原因,导致林区多年冻土的不断退化。以兴安落叶松的特殊性为例。提出可操作性的对策。     

昆明市西华公园水生态植物修复与保护

介绍了水生态修复技术在昆明市西华公园湖塘治理的应用和对公园经济发展的助推作用,并对治理后湖塘水生态修复情况进行了监测,结合后期运行管理,总结了存在的问题,并由此提出了相应的建议。以供参考。     

Study of landscape change under forest harvesting and climate warming-induced fire disturbance

We examined tree species responses under forest harvesting and an increased fire disturbance scenario due to climate warming in northern Wisconsin where northern hardwood and boreal forests are currently predominant. Individual species response at the ecosystem scale was simulated with a gap model, which integrates soil, climate and species data, stratified by ecoregions. Such responses were quantified as species establishment coefficients. These coefficients were used to parameterize a spatially explicit landscape model, LANDIS. Species response to climate warming at the landscape scale was simulated with LANDIS, which integrates ecosystem dynamics with spatial processes including seed dispersal, fire disturbance, and forest harvesting. Under a 5 °C annual temperature increase predicted by global climate models (GCM), our simulation results suggest that significant change in species composition and abundance could occur in the two ecoregions in the study area. In the glacial lake plain (lakeshore) ecoregion under warming conditions, boreal and northern hardwood species such as red oak, sugar maple, white pine, balsam fir, paper birch, yellow birch, and aspen decline gradually during and after climate warming. Southern species such as white ash, hickory, bur oak, black oak, and white oak, which are present in minor amounts before the warming, increase in abundance on the landscape. The transition of the northern hardwood and boreal forest to one dominated by southern species occurs around year 200. In the sand barrens ecoregion under warming conditions, red pine initially benefits from the decline of other northern hardwood species, and its abundance quickly increases. However, red pine and jack pine as well as new southern species are unable to reproduce, and the ecoregion could transform into a region with only grass and shrub species around 250 years under warming climate. Increased fire frequency can accelerate the decline of shade-tolerant species such as balsam fir and sugar maple and accelerate the northward migration of southern species. Forest harvesting accelerated the decline of northern hardwood and boreal tree species. This is especially obvious on the barrens ecoregion, where the intensive cutting regime contributed to the decline of red pine and jack pine already under stressed environments. Forest managers may instead consider a conservative cutting plan or protective management scenarios with limited forest harvesting. This could prolong the transformation of the barrens into prairie from one-half to one tree life cycle.     

城市热岛效应对气候变暖和植物物候的影响

城市热岛效应与全球气候变暖的关系及其对植物物候的影响是当今全球气候变化研究领域关注的焦点。文中综述了国内外关于城市热岛的形成机制及其特征、对气候变暖的时空尺度效应以及对植物物候的影响等方面的最新研究进展, 提出城市热岛效应研究中存在的问题及未来应加强的研究工作。     

Mapping forest dynamics under climate change: A matrix model

Global climate change may be affecting forests around the world. However, the impact of climate change on forest population dynamics, especially at the landscape or regional level, has hardly been addressed before. A new methodology was proposed to enable matrix transition models to account for climate impact on forest population dynamics. The first climate-sensitive matrix (CSMatrix) model was developed for the Alaska boreal forest based on observations from over 15 years of forest inventory. The spatially explicit model was used to map climate-induced forest population dynamics across the region. The model predicted that the basal area increment in the region under natural succession would be hindered by global warming, more so for dry upland areas than for moist wetlands. It was suggested that temperature-induced drought stress could more than offset a predicted increase of future precipitation in the region to lower overall forest productivity. At the same time, stand diversity would increase across the region through transient species redistribution. Accounting for climate conditions made the CSMatrix model more accurate than conventional matrix models.     

Assessing the impacts of climate change and nitrogen deposition on Norway spruce (Picea abies L. Karst) growth in Austria with BIOME-BGC

The aim of this paper is to determine whether a detectable impact of climate change is apparent in Austrian forests. In regions of complex terrain such as most of Austria, climatic trends over the past 50 years show marked geographic variability. As climate is one of the key drivers of forest growth, a comparison of growth characteristics between regions with different trends in temperature and precipitation can give insights into the impact of climatic change on forests. This study uses data from several hundred climate recording stations, interpolated to measurement sites of the Austrian National Forest Inventory (NFI). Austria as a whole shows a warming trend over the past 50 years and little overall change in precipitation. The warming trends, however, vary considerably across certain regions and regional precipitation trends vary widely in both directions, which cancel out on the national scale These differences allow the delineation of 'climatic change zones' with internally consistent climatic trends that differ from other zones. This study applies the species-specific adaptation of the biogeochemical model BIOME-BGC to Norway spruce (Picea abies (L.) Karst) across a range of Austrian climatic change zones, using input data from a number of national databases. The relative influence of extant climate change on forest growth is quantified, and compared with the far greater impact of non-climatic factors. At the national scale, climate change is found to have negligible effect on Norway spruce productivity, due in part to opposing effects at the regional level. The magnitudes of the modeled non-climatic influences on aboveground woody biomass increment increases are consistent with previously reported values of 20-40 kg of added stem carbon sequestration per kilogram of additional nitrogen deposition, while climate responses are of a magnitude difficult to detect in NFI data.     

Large-scale permafrost degradation as a primary factor in Larix sibirica forest dieback in the Khentii massif,northern Mongolia

The objective of this study is to investigate the potential causes of widespread Larix sibirica Ledeb.mortality observed in the Khentii massif of northern Mongolia.The ratio of deadwood to living trees in affected stands in the Goricho region,the southernmost study site situated close to the Gobi Desert,was as high as 3.6:1.Moisture fluctuations monitored over 2 years using electrical impedance spectrometry revealed that the Goricho study site had higher soil moisture levels than the two less affected sites Barun Bayan and Dzun Bayan.High soil moisture was recorded in an area characterized by highly skeletal soils,ones with more than 35%by volume of rock fragments,and comparatively shallow soil horizons,from valley to mountains.The layer of permafrost influencing hydrogeological processes is much deeper in the Goricho region compared to the undisturbed study sites.Redundancy analysis confirmed a significant number of dead L.sibirica on sites with developed soils.Live forest stands,however damaged,grow in this region on well-drained scree slopes or on rocky bastions.The mass mortality observed for L.sibirica may be directly linked to accelerated permafrost thaw in the area bordered by the Tuul and the Terelj Rivers.Our assumption is that L.sibirica root system necrosis occurred as a result of long-term waterlogging of developed soils with high spatial heterogeneity,normally able to absorb high quantities of groundwater.The areas unaffected were scree fields and rocky bastions characterized by adequate drainage.All of our findings support the primary stages of large-scale permafrost thaw,i.e.,correlating increases in soil moisture with increasing permafrost active layer thickness.     

Warming effect on growth and physiology of seedlings of Betula albo-sinensis and Abies faxoniana under two contrasting light conditions in subalpine coniferous forests of western Sichuan, China

The subalpine coniferous forests on the eastern Qinghai-Tibet Plateau provide a natural laboratory for studying the effect of climate warming on terrestrial ecosystems. Research on differences between tree species in their responses to experimental warming can provide insights into their regeneration behavior and community composition under a future warmer climate. We used open-top chamber (OTC) to determine the short-term effect of two levels of air temperature (ambient and warmed) and light (full light and ca. 10% of full-light regimes) on the early growth and physiology of Betula albo-sinensis and Abies faxoniana seedlings. The OTC manipulation increased mean air temperature and soil surface temperature by 0.51 and 0.34°C, respectively, in a 60-year-old plantation and 0.69 and 0.41°C in forest openings, respectively. Warming generally increased plant growth, biomass accumulation, and advanced physiological processes for seedlings of both species. In response to warming, both tree species allocated relatively more biomass to foliage and had significantly decreased root/shoot ratios (R/S), which might provide the two species with an adaptive advantage when other environmental factors were not limiting. Warming may enhance photosynthesis in the two seedlings by increasing efficiency of PSII in terms of increases in F _v/F _m, photosynthetic pigment concentrations, and apparent quantum yield (Φ). However, the effects of warming on seedling growth and physiological performance varied by light conditions and species. For B. albo-sinensis seedlings, the effects of warming were pronounced only under full-light conditions, while the growth and physiological responses of A. faxoniana seedlings to warming were found only under low-light conditions. Competitive and adaptive relationships between the two species may be altered as a result of response differences to warming manipulation. The shortterm beneficial impact of warming on the early growth and development of the two species suggests that global warming may lead to changes in regeneration dynamics and species composition in subalpine coniferous forest ecosystems.     

气候变化与中国北方森林恢复和经营

全球气候变暖已经成为一个不争的事实。在全球气候变化背景下,我国的气温不断增高,降水和极端天气气候事件不断增多。根据气候变化现状和趋势,文章从陆地生态系统的可能响应、北方森林的分布变化、生产力、生物地球化学循环、火干扰等方面分析了气候变化对中国北方森林生态系统的可能影响,并提出了我国北方森林应对气候变化的适应性对策。     

Integration of albedo effects caused by land use change into the climate balance: Should we still account in greenhouse gas units?

Due to impacts of albedo on climate change, benefits of afforestation/reforestation regimes are under debate. In this paper we investigate how to incorporate albedo changes in a carbon accounting tool to show the net effect of land use change on the climate. Using a study area in southern Europe, albedo and carbon sequestration modelling results are linked to determine the combined radiative forcing balance. The results show that under specific circumstances afforestation/reforestation measures may not automatically have positive impacts in a global warming context because the cooling effect of most of the carbon sequestered is neutralized by the warming effect of albedo changes. However, sensitivity analyses lead to the conclusion that improved albedo data from satellite images (MODIS) could influence and enhance outputs significantly. The paper points out that accounting based exclusively on GHG units does not, in the case of land use change, reflect the entire picture. It is highly recommended that in future global warming impacts of land use systems and biogenic products (e.g. solid biomass, liquid biofuels) should be studied using life cycle assessments (LCA) and should include these additional—non-GHG effects—on climate change.     

Regional impact assessment on forest structure and functions under climate change—the Brandenburg case study

A forest simulation model has been applied in a regional impact assessment to investigate impacts of climate change on forest structure and function in the Federal state of Brandenburg, Germany. The forest model FORSKA-M was linked to a GIS that included soil, groundwater table and land-use maps. Two climate scenarios (current climate and a climate change of 1.5 K temperature increase which is combined with a precipitation decrease of 10–20% on average) for 40 meteorological stations in and around Brandenburg were used to assess the sensitivity of species composition to climate change. Furthermore, the implications of vegetation changes for other forest functions were analysed by means of several indicators. To evaluate the impacts of climate change on biodiversity, measures of species diversity (Shannon’s and Simpson’s index) and habitat and structural diversity (Seibert’s index) were applied. The evaluation of impacts on groundwater recharge of natural and managed forests was carried out using the soil water balance model of FORSKA-M.At first, model simulations of the potential natural vegetation (PNV) on the whole area of Brandenburg with different climate scenarios were analysed. The results indicated that climatic warming would lead to a shift in the natural species composition in Brandenburg towards more drought tolerant species. The simulated diversity of the forests would be reduced, and groundwater recharge would be decreased.The majority of forests in the state of Brandenburg have been managed intensively in the past. At present, large areas of Brandenburg’s forests are dominated by pure stands of Scots pine, but current forest management practice aims at increasing the share of deciduous and mixed forests. In order to analyse the possible consequences of climate change on forest management, forest inventory data were used to initialise FORSKA-M with representative forest stands. Simulation experiments with three different management scenarios showed that the short to mid-term effects of climatic change in terms of species composition were not as severe as expected. However, the comparison of different diversity measures indicates a decrease in the species diversity in contrast to an increase in habitat diversity under climate warming. Furthermore, a decrease in productivity and groundwater recharge was simulated under the climate change scenario.The regional impact assessment corroborated the high sensitivity of natural forests in the region to the projected climatic change and it underlined the importance of adaptive management strategies to help forestry to cope with climatic change.     

温室效应、全球变暖与林业

本文综述了当前受到国内外普遍重视的全球变暖和气候变化以及与林业有关的问题。简要介绍了目前对森林在全球碳平衡中的作用, 气候变化可能对林业的影响, 以及林业对策的研究现状和展望。