Landscape Analysis of the Forest-Tundra Ecotone in Rocky Mountain National Park,Colorado∗

Landscapes in the ecotone between forest and tundra contain a mosaic of patches of trees, meadows, lakes, disturbed areas, and other features. The structure of this mosaic affects species habitat and potential ecotone response to global change. However, the alpine forest-tundra ecotone may be insensitive to climatic change if it is a climatic relict or is frequently disturbed. We used GIS and multivariate statistics to (1) analyze landscape structure in transects across the ecotone in Rocky Mountain National Park, (2) identify the major variants of forest-tundra ecotone, and (3) identify the influence of the environment and natural disturbances on variation in the landscape structure of the ecotone. There are six major types of ecotone varying in the amount of natural disturbances, permanent features (e.g., lakes), closed forest, patch forest, and krummholz. Variation is primarily related to slope, elevation, aspect, and geology associated with the morphology of the mountains and the disturbances they produce. The ecotone is not strongly structured by natural disturbances; thus, it may be more strongly controlled by and sensitive to climatic change than in areas where disturbance is more prevalent. Monitoring of potential ecotone response to global change is feasible, if tailored to the types of ecotone and their expected response.     

Dynamics of the Alpine Treeline Ecotone under Global Warming: A Review

The alpine treeline ecotone is defined as a forest-grassland or forest-tundra transition boundary either between subalpine forest and treeless grassland, or between subalpine forest and treeless tundra. The alpine treeline ecotone serves irreplaceable ecological functions and provides various ecosystem services. There are three lines associated with the alpine treeline ecotone, the tree species line (i.e., the highest elevational limit of individual tree establishment and growth), the treeline (i.e., the transition line between tree islands and isolated individual trees) and the timber line (i.e., the upper boundary of the closed subalpine forest). The alpine treeline ecotone is the belt region between the tree species line and the timber line of the closed forest. The treeline is very sensitive to climate change and is often used as an indicator for the response of vegetation to global warming. However, there is currently no comprehensive review in the field of alpine treeline advance under global warming. Therefore, this review summarizes the literature and discusses the theoretical bases and challenges in the study of alpine treeline dynamics from the following four aspects: (1) Ecological functions and issues of treeline dynamics; (2) Methodology for monitoring treeline dynamics; (3) Treeline shifts in different climate zones; (4) Driving factors for treeline upward shifting.     

气候变化和人类活动对南方红壤丘陵区森林生态系统影响模拟研究——以江西泰和县为例

在全球气候变化和人类活动的影响下,森林生态系统结构、功能以及空间格局都将发生不同程度的变化。明晰景观尺度上未来森林的动态变化,对森林可持续发展具有重要意义。选择江西省泰和县为研究区,综合利用土地利用模型（CA-Markov）和森林景观动态模型（LANDIS-II）,并结合生态系统过程模型（PnET-II）,模拟气候变化、土地利用、采伐以及综合情景下未来40年（2010-2050年）阔叶林、针叶林的面积及生物量变化。结果表明：① 气候变化对森林面积影响较小,采伐使森林面积显著减少,土地利用变化使森林面积的变化更加剧烈;② 针叶林和阔叶林对不同干扰方式的响应表现出较强差异,针叶林对采伐的响应更加剧烈;③ 多模型综合模拟方法有助于区域森林管理,为南方红壤丘陵区森林结构优化和功能提升提供科学建议。     

Forest transition and biogeographic meaning of the current laurel forest landscape in Canary Islands,Spain

This study provides a geographical synthesis of the current natural landscape dynamics of the Canarian laurel forest based on the results of a biogeographic study of its structure, composition, and dynamics. Historical socioeconomic changes and recent environmental conservation strategies have led to natural forest dynamics that make it necessary to change our current scientific conception of the Canarian laurel forest landscape. According to the forest transition theory, in the protected areas of Anaga and Teno Rural Parks (Tenerife) and Garajonay National Park (La Gomera), the forest reaction to the gradual abandonment of economic activity reveals how strongly human activity has shaped the features of the laurel forest, which traditionally has been considered to be relatively untouched by humankind. How natural disturbances have affected this forest over the past few years has also contributed to a better understanding of its dynamics. This study explains the key patterns of spontaneous dynamics in the Canarian laurel forest to enrich our understanding of this forest and its landscape, while highlighting the importance of human activity as the catalyst for its current vigorous dynamics.     

Mapping Ecotone Movements: Holocene Dynamics of the Forest Tension Zone in Central Lower Michigan,Usa

This paper presents a novel method for detecting and mapping movements of ecotone boundaries, over both time and space, using existing fossil pollen data. The method combines existing statistical techniques, including discriminant analysis and spatial interpolation, to generate statistically robust maps of ecotone boundaries over time. This method was applied to provide a comprehensive vegetative history of the forest tension zone in the Lower Peninsula of Michigan during the last 10,000 years. Pollen data for nine lakes in the Lower Peninsula were analyzed with discriminant analysis and spatially interpolated with inverse distance weighted to track ecotone movements of the forest tension zone. The forest tension zone has been in existence over the last 10,000 years and has been highly variable over space and time, with at least three major latitudinal shifts, spanning 320 km and 6° of latitude, as well as several less pronounced shifts. These shifts occurred primarily in response to millennial-scale oscillations in climate such as the warmer and dryer conditions associated with the mid-Holocene. A slighter shift was evident in association with the cooler and drier conditions of the Little Ice Age (600-100 cal yr BP). This research demonstrates the sensitivity of Great Lakes forest communities to Holocene climate change and suggests a similar sensitivity of future ecotone dynamics in response to modern global warming.     

伊犁河三角洲景观结构的影响机制研究

在遥感和水文数据的支持下,根据伊犁河三角洲作为典型的中亚干旱区内陆河流域尾闾区域特点,确定了伊犁河三角洲的景观分类系统。通过采用景观结构梯度分析法、景观干扰度指数和景观Kappa指数等方法,系统地分析了近32 a（1975-2007）伊犁河三角洲景观结构的时空演变特征,并对景观结构的影响机制做了充分地探讨。结果表明：（1）沿着一定的地形梯度和水文梯度,伊犁河三角洲流域景观表现出特殊的纵向结构、横向结构的梯度特征和景观内部特征,与地表水直接关联的景观类型表现尤为明显,如湖泊、沼泽、漫滩。（2）在人为活动和自然环境的双重影响下,近32 a伊犁河三角洲景观结构的空间变化具有一定的周期性和不稳定性,主要体现为景观类型面积和空间位置的变化,其中以湿地景观类型的变化最为显著。（3）生态干扰对景观结构的影响因景观类型的不同存在显著的差异性和时空变异性,以湖泊和沼泽受干扰作用最为明显。高、中、低三种干扰强度区域的空间分布及面积变化同样具有一定的周期性和不稳定性。（4）水利工程建设和自然环境是影响伊犁河三角洲景观结构的主要驱动力。水利工程对伊犁河的拦蓄引起景观结构变化的作用最为深远,它通过改变三角洲上游的水文情势直接影响整个区域的景观结构。而自然环境因素中的地形和水文条件主要影响湿地景观类型的时空分布,气候因子则直接影响河川径流量。     

中国生态过渡带分布的空间识别及情景模拟

在全球变化及其生态环境效应研究中,如何对生态过渡带的空间分布格局及变化情景进行空间定量识别和模拟分析,对揭示气候变化和人类活动对全球变化的响应及反馈具有指示性意义。在对HLZ模型进行修正和拓展的基础上,建立了生态过渡带类型的空间识别方法。并基于1981—2010年的全国782个气候观测站点数据,在实现全国生态过渡带类型及分布的空间识别基础上,结合3种气候情景数据CMIP5 RCP 2.6、RCP 4.5和RCP 8.5,实现了T0（1981—2010年）、T1（2011—2040年）、T2（2041—2070年）和T3（2071—2100年）4个时段内全国生态过渡带的空间分布格局及其未来情景模拟。另外,引入平均中心空间分析模型,对全国生态过渡带平均中心的时空偏移趋势进行了定量分析。结果显示：在T0~T3时段内,全国共出现41种生态过渡带类型,约占全国陆地面积的18%;冷温带草原/湿润森林与暖温带干旱森林过渡带（564238.5 km²）、冷温带湿润森林与暖温带干旱/湿润森林过渡带（566549.75 m²）、北方湿润/潮湿森林与冷温带湿润森林过渡带（525750.25 km²）是最主要的3种生态过渡带类型。面积占到全国生态过渡带总面积的35%;2010—2100年期间的冷温带荒漠灌丛与暖温带荒漠灌丛/有刺草原过渡带的增加速度最快,在3种情景RCP 2.6、RCP 4.5和RCP 8.5下,其面积将分别增加3604.2 km²/10a、10063.1 km²/10a和17242 km²/10a;寒冷型生态过渡带类型总体上呈向暖湿型过渡带类型增加的趋势;北方潮湿森林与冷温带湿润/潮湿森林过渡带的平均中心偏移幅度最大,在4个时段内整体向东北方向偏移,其偏移幅度将超过150 km。另外,随着气温的逐渐上升和降水量的增加,中国北方的生态过渡带整体呈向北偏移趋势,南方生态过渡带则逐渐减少且平均中心呈现逐渐向高海拔地区退缩的趋势,气候变化对青藏高原区生态过渡带时空格局的影响日益显著。     

Spatial Ecology of Pre –Euro‐American Fires in a Southern Rocky Mountain Subalpine Forest Landscape

Natural disturbances such as fires have been widely studied, but less is known about their spatial ecology than about other aspects of them. We reconstructed and mapped pre–Euro‐American fire history in a subalpine forest landscape in southeastern Wyoming, and analyzed the fires using GIS. Mean fire interval varies little with topography (elevation, aspect, slope) and is spatially autocorrelated at distances of at least 2 km. Fires often spread downslope, and spread more than expected from the north and south and less than expected from the west, under the influence of particular synoptic climatic conditions. The landscape of 1868 a.d., at the time of Euro‐American settlement, was strongly influenced by fires. However, it contained large patches of connected forest and few high‐contrast edges, unlike the modern landscape, which is fragmented by industrial forestry and roads. The spatial ecology of the natural fire regime may be a useful guide for management.     

History of forestry in a central Norwegian boreal forest landscape: Examples from Nordli,Nord-Tr⊘ndelag

Analysing forest history is crucial to understanding how shifting harvesting methods have different effects on forest landscape structure. Two main harvesting regimes in a Norwegian boreal forest landscape over a period of 150 years were detected by the study. A homogeneous impact regime resulting from selective logging changed the forest structure by logging the oldest and largest trees evenly throughout the forest, resulting in a homogeneous landscape structure. However, population growth in the 19th century led to a substantial increase in traditional subsistence forestry to obtain building materials, firewood, etc. The most intensive stage of this regime started in c.1860 when farmers began selling logging contracts to companies and timber traders. Despite this being termed a homogeneous landscape impact, the actual exploitation of the forest was strongly influenced by local factors such as the location of farms, summer farms, lakes, and rivers. Clear-cutting from the 1950s has resulted in a new heterogeneous impact regime, giving a landscape structure dominated by patches of even-aged stands. This regime still predominates. The analysis is based on a study of Nordli and the Sand?la drainage basin in Nord-Tr?ndelag. Such studies should give a better understanding of the interaction between natural ecological conditions in and human impact on boreal forest landscapes.     

西双版纳山地不同森林景观鸟类多样性

研究了在不同形式人类经济活动下的森林景观变化与西双版纳地区鸟类多样性的关系．同时对发展生产时的用地布局和维护森林景观的动态发展与提高人们生活质量和持续发展的关系进行了讨论．     

A 25-year Survey of Geoecological Change in the Scandes Mountains of Sweden

The paper reviews various kinds of geoecological change in the tree-limit ecotone of the Scandes Mountains during the period 1970–95. The focus of the study is a part of a regional network of sites intended for long-term tree-limit monitoring, with special stress on effects of climatic variability. The elevational tree-limits of Betula pubescens sp. Sortuosa, Picea abies and Pinus sylvestris, which rose in response to the climatic amelioration earlier this century, now show clear symptoms of increasing climatic stress and disturbance. This manifests as defoliation, growth recession and reproductive failure, locally leading to some initial elevational tree-limit retraction (unbalanced mortality). Defoliation was preceded by decades of weak summer cooling and an increasingly maritime climate, but recently it correlates significantly with low winter soil temperatures, causing death of needles, shoots and buds. In some habitats, Betula pubescens has suffered from mechanical stress and disturbance by increased snow accumulation. Tree-limit decline is paralleled by analogous responses of high-elevation boreal forests as well as the ground cover, encompassing elevational range-limit retraction of certain plant species, deterioration of alpine/subalpine dwarf-shrub heaths and terricolous lichen mats. These processes coincide with indications of enhanced periglacial activity, chiefly wind deflation of frost-heaved top-soils at exposed sites. Presumably, reindeer trampling and grazing play a certain role in the latter context, although this disturbance interacts with climate cooling and increased storminess. Short-term extreme events, particularly concerning winter climate (e.g. ground frost), represent previously underrated disturbance mechanisms in cold-stressed, high-altitude boreal forest. The results suggest mechanisms of tree-layer regression, which lag behind the most severe stresses and disturbances by decades and make cold-marginal trees increasingly sensitive to climatic extremes and, in addition, unable to respond progressively to later positive weather anomalies, due to major defoliation and hypothetical xylem cavitation. The recorded changes are logical in consequence of the irregular climatic cooling and a more maritime climate since the late 1930s. In a wider perspective, the results fit a current pattern of natural geoecological destabilization and rapid vegetation change in the North Atlantic region. In addition, the results are discussed in the perspective of global climate change and biogeographical records over the past few decades.     

三种主要干扰造成中国森林植被向大气中的碳排放量

对重要干扰过程导致森林植被向大气中的碳排放量进行评估,对于合理评估森林碳汇功能及其在应对全球气候变化中的作用是有重要意义的。本文基于有关森林干扰发生情况的林业统计资料和有关干扰引起生物量C转移过程与比例的假设条件,估算了近20年来采伐、火灾与病虫鼠害三种主要干扰每年从森林植被直接排放到大气中的C量。结果表明,近20年来,中国森林遭受了比较强烈的采伐、火灾与病虫鼠害干扰,并且这三种干扰在进入21世纪后有着比较明显的增加趋势。相应地,在1990-2009年间,采伐、火灾与病虫鼠害的C排放量年均分别为3425.16万tC、161.29万tC、428.80万tC,合计为4015.24万t。三种干扰的总C排放量在1990-1999年间年均为3079.40万t,在2000-2009年间年均为4951.09万t。从不同森林类型分布区的排放来看,中国森林主要干扰的年均C排放量及其年代际变化呈现比较明显的区域特征。干扰对中国森林碳平衡有着重大影响,针对干扰的森林管理可能具有较大的增汇潜力,并且在未来有关森林与陆地生态系统碳收支的模型研究中需考虑主要干扰的影响。     

Many a little makes a mickle: Cumulative land cover changes and traditional land use in the Kyrö reindeer herding district,northern Finland

Traditional land use systems are threatened by land use intensification and resulting land cover transitions in northern areas. This article examines cumulative land cover changes and their impacts on reindeer grazing grounds in the Kyrö reindeer herding district in northern Finland. Land cover transitions were studied using Landsat TM and OLI images and topographic maps. The results showed that the herding district has experienced notable land cover changes during the past decades, and most of these changes were directly related to forestry. The proportion of continuous coniferous forests of the total forest cover declined from 92% to 78% between 1987 and 2013. Approximately one third of the forests outside current conservation areas were disturbed by forest management by 2013, and remaining forests were notably more fragmented than forests within conservation areas. The extent of the road and path networks expanded considerably between 1960s and 2010 as a result of increasing logging and tourism. Accumulation of disturbances gradually results in loss of key resources and declined quality of the landscape mosaic from the reindeer herding perspective, which can pose a serious threat to long-term sustainability of the livelihood. Rapid land cover changes in non-protected areas highlight an increasingly important role of conservation areas in maintaining resources for reindeer husbandry in the face of intensifying land use. Sustainable management of resources outside conservation areas requires careful participatory planning and efficient cumulative impact assessment of different land use activities.     

南岭国家级自然保护区森林景观格局变化与动态模拟

基于eCogntion、ArcGIS 和IDRISI 软件,采用景观格局指数分析广东南岭国家级自然保护区1988~2009 年景观类型数量及空间格局的变化;运用CA-Markov 模型模拟流域2010年的景观格局,预测2021 年的景观格局。结果表明,研究区森林景观类型以常绿阔叶林和针叶林为主;景观破碎度增加,斑块复杂程度提高,各景观类型的分布更加趋于复杂化;CA-Markov模型预测表明,2010~2021 年景观破碎度有所降低,多样性增加。     

Late-Holocene equatorial environments inferred from deposition processes,carbon isotopes of organic matter,and pollen in three shallow lakes of Gabon,west-central Africa

Seven vibro-cores were collected from three shallow lakes of the Gabon (Kamalété, Nguène, Maridor) along a 300-km west–east transect close to the Equator. These lakes are located in very distinct landscapes: coastal forest-savanna mosaic, rain forest and savanna with colonising forest, respectively. Core chronologies were established by radiocarbon dating. Study of these lacustrine archives (textural variables, clay minerals, organic matter components, δ¹³C, pollen) allowed comparison of late Holocene environmental changes recorded at each site and with results from other studies. Lake Kamalété indicates minor climatic deterioration (increased drying and greater seasonality) between 1,410 and 500 cal. years BP, which is also recognised in southern Cameroon and east-central Africa. Lake Nguène was surrounded by dense moist forest throughout the last 4,110 years, but shows significant deterioration from ~2,800 cal. years BP, a phenomenon seen at nearby sites. Lake Maridor shows a decline of forest initiated a little after 3,800 cal. years BP, which indicates timing that is distinct from the two other sites. This was probably a response to local conditions (i.e. outlet damming). Although the three lakes display generally parallel climatic trends perhaps linked to SST oscillations, there is not perfect coherence between these three sites. Differences among the three basins may be attributable to local factors like groundwater hydrology and slope instabilities of such shallow lake systems in this equatorial region.     

太白山高山带环境特征

对比国内外关于高山带景观划分的多种观点，采用气候树线以上部分为高山带的划分方法，重点讨论太白山高山带自然环境，包括第四纪冰川遗迹和现代冰缘作用影响下的高山、亚高山地貌，研究区内主要气候要素的分布状、特别气温和降水的时空分配分布格局，土壤有机质的空间分异，以及在这种环境条件下高山带的植物区系和植被分布格局。太白山高山带的各种环境要素之间密切相关，是表现特殊的自然综合体。在全球气候变化背景下，其自然环境特点及变化值得密切关主。     

退耕还林（草）背景下中国北方农牧交错带土地利用及碳储量变化

为明析退耕还林（草）背景下生态环境较为脆弱的北方农牧交错带土地利用及碳储量变化,基于该区2000、2010、2018年土地利用数据,通过动态度、土地转移矩阵,景观指数等指标从土地利用变化的数量、速率以及空间格局特征加以分析,同时基于InVEST模型定量估算了该区近20年来的碳储量变化。结果表明：（1）北方农牧交错带土地利用类型以草地、耕地、林地为主,面积合计逾4.30×10⁵ km²,占比超过91.83%;林地、建设用地显著扩张,草地与耕地有明显减少趋势,同时两者之间流转面积最多,高达1.67×10⁴ km²,研究区景观格局总体上收敛于“集中—分散”;（2）近20年来北方农牧交错带总碳储量51.44—52.81亿t,总体呈增加趋势,碳密度稳定在110 t·hm^-2左右,退耕还林（草）政策下碳储量净增加逾300万t。北方农牧交错带土地利用变化程度较为剧烈,退耕还林（草）政策不仅是土地更迭的主要驱动因素,也是该区固碳功能显著提升的重要原因。     

Reconstructing pre-agricultural expansion vegetation cover of Ethiopia

Landscape reconstructions can be used to define a reference condition from which to assess the magnitude of land changes caused by human influence. Since the beginning of the last century, the population of Ethiopia has increased drastically with large effects on the natural vegetation and biodiversity. However, the original land cover patterns in Ethiopia have not been precisely mapped, which hinder the identification of the biophysical and socio-economic factors that contributed to the current landscape patterns. The objective of this study was to reconstruct the past century vegetation landscapes of Ethiopia (i.e. vegetation cover before agricultural expansion) and identify which ecosystems have been most affected by land changes. First, the net primary productivity (NPP) was modelled based on the climatic constraints of natural vegetation growth (water availability, solar radiation and minimum temperature) derived from remote sensing and climate data. This analysis showed that water availability is the most critical constraint for vegetation growth for all regions and land cover types in Ethiopia. Then, the past vegetation was mapped based on predicted NPP. Our results show that i) the extent of broadleaved evergreen or semi-deciduous forest, open broadleaved deciduous forest, closed to open shrubland, mosaic forest-shrubland/grassland, sparse vegetation and grassland was 18.8%, 12.4%, 20.6%, 31.5%, and 16.8%, respectively, and ii) current agricultural landscapes were previously covered mainly by broadleaved evergreen and deciduous forest, which encompassed 38.9%. The least affected by agricultural expansion were sparse vegetation and grassland. Our study provides novel insights on pre-agricultural expansion landscapes in Ethiopia with critical information for scientists and other stakeholders working on the restoration and rehabilitation of degraded areas.     

220 ka以来萨拉乌苏河流域地层磁化率与气候变化

 萨拉乌苏河流域滴哨沟湾剖面磁化率变化结果表明:近220 ka来我国北方气候变化极不稳定,存在着不同尺度的频繁变化,特别是寒冷气候阶段变化尤为频繁,其中倒数第二次冰期存在5个气候旋回,末次冰期存在10个气候旋回。这些气候变化与深海氧同位素、极地冰芯反映的全球变化具有良好的对应关系,反映了该区气候变化与全球变化的一致性。控制本区气候变化的主要因素是全球冰量变化及太阳辐射影响的东亚季风变化。     

新疆天山自然遗产地景观格局动态演化及其生态健康评价

喀拉峻-库尔德宁区域是新疆天山自然遗产地的重要组成部分，其生态健康状况将影响该自然遗产地的突出普遍价值。目前从景观生态学角度，通过景观格局动态演化过程反映自然遗产地生态健康研究较少。本研究以喀拉峻-库尔德宁区域为例，基于多源遥感影像，提取景观信息进行定性与定量分析，并结合景观格局指数，从景观动态特征、类型水平和景观水平分析景观格局演化特征，评价景观健康状况，形成自然遗产地景观数据的获取方法，探索景观格局与生态过程的关系，为相关研究提供借鉴。结果显示：裸地增加，冰雪、针阔混交林等景观减少；类型水平上，针阔混交林受人为干扰严重，中和低覆盖度草地呈破碎化；景观水平上，景观聚集度、连通性、分形状况稳定，景观多样性提升后维持稳定；总体景观生态健康，突出普遍价值（OUV）维持稳定，但对针阔混交林需要进行重点保护。结果可为研究区综合管理和生态健康分析提供有效数据。