Land use/cover, landforms and fragmentation patterns in a tropical dry forest in the southern Pacific region of Mexico

In spite of widely documented studies of deforestation rates and land use/cover changes in tropical dry forests in Mexico, relatively little is known about fragmentation patterns in such forests. This study defines the spatial distribution of landforms and land use/cover types the lower Papagayo River basin and examines their influence on fragmentation patterns and biological diversity in a tropical dry forest in that southern Pacific region. The land use/cover map was constructed from aerial photographs, Landsat TM imagery (2000) and fieldwork. Landform units were defined based on altitude, slope, lithology and morphology. Landscape fragmentation parameters were obtained using FRAGSTATS (version 3.3) considering the numbers of patches, mean, minimum and maximum patch size, edge density, total edge and connectivity. Results show tropical dry forest to be remnant vegetation (~11 per cent), characterized by isolation and low connectivity. Land use/cover types have different effects on fragmentation patterns. Agriculture and cattle raising produce similar numbers of patches, but with a different mean size; and human settlements have a scattered distribution pattern. The abandonment of rural agricultural livelihoods has favoured the expansion of secondary tropical dry forest characterized by continuity and high connectivity, which suggests a high regeneration potential from land abandonment. It can be concluded that tropical dry forest fragmentation and recovery at regional scales depend on such landscape attributes as lithology, slope, geomorphology and management.     

How landscapes change: Integration of spatial patterns and human processes in temperate landscapes of southern Chile

A comprehensive understanding of the patterns that occur as human processes transform landscapes is necessary for sustainable development. We provide new evidence on how landscapes change by analysing the spatial patterns of human processes in three forest landscapes in southern Chile at different states of alteration (40%-90% of old-growth forest loss). Three phases of landscape alteration are distinguished. In Phase I (40%-65% of old-growth forest loss), deforestation rates are < 1% yr⁻¹, forests are increasingly degraded, and clearance for pastureland is concentrated on deeper soils. In Phase II (65%-80%), deforestation reaches its maximum rate of 1-1.5% yr⁻¹, with clearance for pastureland being the main human process, creating a landscape dominated by disturbed forest and shrubland. In this phase, clearance for pastureland is the primary driver of change, with pastures expanding onto poorer soils in more spatially aggregated patterns. In Phase III (80%-90%), deforestation rates are again relatively low (<1% yr⁻¹) and forest regrowth is observed on marginal lands. During this phase, clearance is the dominant process and pastureland is the main land cover. As a forest landscape is transformed, the extent and intensity of human processes vary according to the existing state of landscape alteration, resulting in distinctive landscape patterns in each phase. A relationship between spatial patterns of land cover and human-related processes has been identified along the gradient of landscape alteration. This integrative framework can potentially provide insights into the patterns and processes of dynamic landscapes in other areas subjected to intensifying human use.     

江浙沪地区土地利用变化模拟和景观格局分析

土地利用／覆被变化对于生态系统多样性和区域生态经济系统可持续性具有深远的影响。本文基于地理信息技术,以江浙沪地区土地利用遥感解译数据为基础,采用景观格局分析法分析了江浙沪地区的景观格局特征;运用CA—Markov模型对江浙沪地区土地利用时空变化进行了模拟。1980-2005年期间,江浙沪地区景观格局变化特征是建设用地增加迅速,耕地集聚减少,建设用地增加主要来自耕地转移,其贡献率达到93．11％。各类斑块类型的破碎度提高;林地和建设用地斑块平均分维数增加,斑块形状趋于复杂,斑块空间分布趋于集中。总体景观破碎度不断提高,景观多样性和景观异质性增加,景观均匀度有所提升：2005年CA—Markov模型模拟结果和遥感解译数据具有高度一致性,Kappa指数达到91％,2010年和2015年模拟结果显示,耕地减少和建设用地增加趋势显著,耕地和林地的减少呈加速状态,建设用地增加的速度降低。未来发展需提高土地利用效率和注重生态格局安全,在提高城市化水平的同时又能兼顾生态保护,以提高区域可持续发展能力。     

2000-2010年中国退牧还草工程区土地利用/覆被变化

在3S技术支持下,结合景观格局定量分析方法,基于30 m分辨率的土地利用/覆被数据,对中国退牧还草工程区2000-2010年土地利用/覆被时空分布特征进行研究。通过利用土地利用转移矩阵和动态度来判定土地利用变化的速度和区域差异,并在斑块类型和景观水平上分析研究区景观格局特征,探讨土地利用格局变化的生态效应。结果表明：①近10年来,研究区土地利用/覆被类型以草地和其他类用地为主,整体内部结构稳定少动。草地变化面积仅占2000年草地总面积的0.37%;林地、湿地、耕地和人工表面的面积均有所增加;其他类用地面积有所减少。②全区土地综合动态度均小于0.1%,土地利用/覆被变幅较小,除人工表面较活跃外,其他各类型变化相对缓慢,且各省土地利用区域差异较小。③研究区内景观基质未发生改变,区域景观破碎度递减,景观多样性水平上升,景观聚集度和连续性微弱下降,景观整体保持较完整态势。退牧还草工程的实施使土地利用/覆被结构和景观格局均得以优化。     

Trends of tropical deforestation in Southeast Mexico

We assessed deforestation in Southeast Mexico (a surface area of 29 000 km² in seven states) through the comparison of land use/land cover maps at a scale of 1:250 000. This facilitated mapping of the land use/land cover change (LULCC) processes and calculation of the rates of change and the change matrix for the period 1978–2000. An original method was used to assess the accuracy of the LULCC map. The verification sites were selected through a stratified random sampling and were corroborated with aerial photographs for 1978 and 2000. Error matrices were elaborated using both hard and fuzzy set approaches in order to take into account the errors related to generalization of the map in fragmented landscapes. The results showed an average annual deforestation rate of 1.1 per cent which represents an average annual loss of 190 000 ha of forest, or an estimated total reduction of 4.2 million ha over 22 years. Furthermore, deforestation processes are concentrated in some areas such as Yucatan and Chiapas states, which registered major forest conversions to grassland and slash‐burning. The overall accuracy of the LULCC map, assessed with hard and fuzzy set approaches, was 72 per cent and 88 per cent respectively.     

内陆干旱区土地利用变化的景观格局特征分析——以新疆白杨河流域为例

基于GIS/RS环境对两期Landsat7-ETM 影像数据进行土地利用分类处理,运用景观生态学原理和数理统计分析方法,从区域整体景观格局水平和土地利用类型水平两个角度,选取景观多样性指数等5个指数描述白杨河流域土地利用变化的景观格局特征。结果表明:研究区各土地利用类型面积都有不同程度的变化,除草地和未利用土地有所减少,其他土地利用类型都有不同程度的增加。从景观水平上看,区域景观异质性在增大,景观斑块的连通性降低,表现为多样性指数和均匀度指数呈增加,优势度指数减小;从类型水平上看,5年间人类对景观的干预程度较大,对人工景观的干扰强于半自然景观,体现在半自然景观类型的分离度较小,而人工景观类型的分离度较大。同时,景观周长-面积分维度指数的增长趋势说明景观斑块的自我相似性减小,几何形状趋于复杂化。总体上,是人类活动加剧破坏了自然绿洲内部的整体性和完整性,并且人类活动干扰还在增加。     

Ants in Labyrinths: Lessons for Critical Landscapes

Percolation theory provides a starting point for models for the movement of organisms in fragmented landscapes. We simulated six general rules for movement on three general landscape patterns with different degrees of habitat fragmentation. Fragmentation pattern affects migration success. Organisms moving within habitat patches are restricted by fragmentation, but the response is less abrupt as one moves from random to hierarchical to fractal landscapes, respectively. Success for organisms moving along edges is more strongly differentiated by landscape pattern. Success and speed are usually directly related, but indirect relations may indicate rare but efficient pathways or cul-de-sacs. We propose that general rules can be applied to the identification of landscapes near critical levels of fragmentation that will respond sensitively to increases in fragmentation or efforts at restoration.     

Progressive landscape fragmentation in relation to cash crop cultivation

Cash crop cultivation has been a critical driver of land use change in many countries around the world. However, few efforts have been made to quantify the relationships between cash crop expansion and the subsequent landscape pattern changes. This paper characterized the process of cash crop expansion across Tiaoxi watershed (China) from 1985 to 2009 using multi-sensor and multi-temporal remotely sensed imageries. Correlations were identified between indicators of cash crop expansion (total area and total production of cash crops) and a family of landscape fragmentation metrics (patch density, edge density, landscape division index, effective mesh size, splitting index, Shannon's diversity index, and aggregation index). Results showed that Tiaoxi watershed experienced profound cash crop expansion and progressive landscape fragmentation. The cash crops spread in accessible and productive areas at the expense of paddy and forests. Social drivers of cash crop expansion included population growth, labor structure changes and market incentives. Indicators of cash crop expansion presented linear relationships with landscape fragmentation metrics. These findings evidenced that cash crop cultivation would significantly fragment landscapes. Our study contributed to understanding on the enlarging cultivation of cash crops and the associated modifications of landscape patterns in subtropical regions.     

滇西北高原湿地区土地利用变化特征

湿地景观格局的动态变化与区域土地利用/覆盖格局的变化有着十分紧密的联系。以纳帕海、碧塔海和属都湖三块高原湿地所在的云南省香格里拉县建塘镇为例,在遥感和GIS技术的支持下,对该区域1974、1987和2000三期Landsat TM(ETM)影像进行了解译,分析了26 a间的土地利用/覆盖变化规律,并结合景观格局动态分析的方法,借助FRAGSTATS软件定量分析了该区景观格局特征及其动态变化。结果表明:该区土地利用/覆盖状况变化显著,主要土地利用/覆盖类型有林地以822 hm2/a的速度在大面积减少,并主要转为灌木林地,使得后者在26 a间扩大高达17倍,变化幅度最大。建设用地和耕地的面积分别扩大了6倍和2倍,而草地和雪地面积持续减少。相应地,该区景观格局定量分析显示,有林地的斑块密度增大而平均斑块面积减小迅速,呈破碎化趋势,灌木林地的斑块密度、平均斑块面积均增加,草地则与之相反均减小,耕地的斑块密度降低而平均斑块面积增加,在不断融合成大斑块,其余各景观单元斑块密度增大平均斑块面积减小,同时各斑块几何形状在1987年变化最剧烈,景观格局趋于复杂。     

近20年来烟台沿海地区土地利用变化研究

基于地理信息技术、景观格局分析理论和马尔可夫模型,利用1986年、1992年、2000年和2004年四期TM数据,定量分析了烟台沿海地区土地利用类型变化及其景观格局动态特征。结果显示:近20年来,烟台沿海地区各种土地类型变化及其相互转化频繁。水域、果园和建设用地分别增加335.61%、70.43%和134.48%,而耕地、林地分别减少18.63%和20.75%。各种土地利用类型空间格局变化显著,耕地、果园破碎度增加,连通性降低,水域、林地和建设用地则趋于集中,连通性增强,景观类型有向多元化方向发展的趋势。马尔可夫模型预测表明,从2008年至平稳期,水域、耕地和林地面积将持续减少,建设用地和果园将逐年增加。耕地保护与建设用地扩张之间的矛盾将更加突出。     

Ants in Labyrinths: Lessons for Critical Landscapes

Percolation theory provides a starting point for models for the movement of organisms in fragmented landscapes. We simulated six general rules for movement on three general landscape patterns with different degrees of habitat fragmentation. Fragmentation pattern affects migration success. Organisms moving within habitat patches are restricted by fragmentation, but the response is less abrupt as one moves from random to hierarchical to fractal landscapes, respectively. Success for organisms moving along edges is more strongly differentiated by landscape pattern. Success and speed are usually directly related, but indirect relations may indicate rare but efficient pathways or cul-de-sacs. We propose that general rules can be applied to the identification of landscapes near critical levels of fragmentation that will respond sensitively to increases in fragmentation or efforts at restoration.     

Forest transitions in tropical landscapes: A test in the Atlantic Forest biodiversity hotspot

Analyzing temporal changes in forest amount and configuration is paramount to better design future forest management interventions. Such analyses are especially required for tropical biomes, which are usually subject to dynamic and heterogeneous land uses. Recent studies have suggested that many tropical biomes are passing through the process of “forest transition”, i.e. an overall change from forest loss to forest gain. However, this hypothesis remains scarcely tested, due to the difficulty of obtaining detailed, quantitative historical records of forest cover. In this study, we investigate 38 years of land use change in Brazil's Atlantic Forest, a biodiversity hotspot, from 1976 to 2014, using multitemporal datasets from aerial photographs and satellite images. We classified the historical series to produce land use maps and calculated a set of landscape metrics, including total forest cover, patch size, patch shape and patch connectivity. Our results indicated non-linear changes through time in forest loss and gain and also in landscape structure, which can be classified into two distinct periods. The first period (1976–1996) was marked by expressive forest loss and fragmentation, whereas the second (1996–2014) was characterized by a much less intense forest dynamics, with little deforestation being balanced by forest regeneration. We attribute the forest dynamics observed to temporal changes in socioeconomic factors, such as increasing human settlements and changes in environmental protection policies. Our results show that current forests are a heterogeneous mosaic of forests with different ages, and support the hypothesis that forest transition is occurring in Atlantic Forest landscapes.     

Different times,same story: Native forest loss and landscape homogenization in three physiographical areas of south-central of Chile

Temperate forest represents the smallest area among the main world's forest biomes, but is one of those most threatened by forest loss. Chile contains most of the temperate forest in South America and more than half of the temperate forest in the southern hemisphere. Chilean temperate forest is considered to be one of the world's biodiversity hotspots. In this study we assessed the rate of land use and land cover (LULC) change over time, identified the main LULCs replacing native forest, and described how changes have evolved in contrasting physiographical conditions and through different historical phases of the landscape over the last 40 years. To achieve this, we analysed LULC change with particular focus on forest cover in three areas representing different physiographical conditions and histories of human occupation in the Araucanía Region of Chile, namely the Central Valley, the Coastal range, and the Andean range. We found substantial differences in temporal and intra-regional patterns of forest loss and LULC change. In the Central Valley, forest loss started long ago, and the area occupied by native forest nowadays is less than 5% of the landscape. In the Coastal range, rapid land cover change has taken place since 1973, with an increasing rate of forest loss over time. We detected a similar but less intense pattern in the forests of the Andean range. Overall, the general pattern points to a process of landscape homogenization in all three physiographical areas. Exotic tree plantations have spread over large geographical areas, becoming the dominant land cover. Land cover change in the Araucanía Region reflects a model of change in which areas with better environmental conditions and accessibility are occupied first for productive activities. As the availability of suitable areas for the expansion of productive activities diminishes, these activities start to move into physiographical areas which were previously “protected” by adverse environmental conditions or poor accessibility. This model of production growth could lead to the complete deforestation of areas outside national protected areas, and other areas which still remain inaccessible due to technological restrictions on exploitation.     

基于RS和GIS的西双版纳土地覆被动态变化

人口增加、经济发展导致滇南热带地区西双版纳土地利用/土地覆被发生显著变化,这些变化对该区的生态环境及生物多样性保护有着重要影响。基于RS和GIS方法,通过对1976、1988和2003年三个时期遥感影像解译分析,试图了解西双版纳近27 a间土地利用/土地覆被时空变化特征及影响因素。结果表明,近27 a间有林地在西双版纳分布最广、占绝对优势,其中以亚热带常绿阔叶林面积最大;但在研究时段内,有林地面积不断减少、呈现破碎化,尤其是热带季节雨林、山地雨林面积减少最为明显和破碎化最为严重。相应,橡胶园、灌木林面积不断扩大并聚集成片,其中橡胶园在1988~2003年间是面积增长最快、最多的地类,其面积扩张主要来源于对热带季节雨林的砍伐。轮歇地面积在1976~1988年是所有地类中增长最快、最多的,在1988~2003年由于向橡胶园转变而大幅度减小。粗放式的刀耕火种和橡胶种植园的不断扩大是主导本区土地利用/土地覆被变化的主要因素,土地利用变化导致了本区生态环境的退化和生物多样性的丢失。     

Assessment of multifunctional landscapes dynamics in the mountainous basin of the Mo River (Togo,West Africa)

In this study, historical landscape dynamics were investigated to (i) map the land use/cover types for the years 1972, 1987, 2000 and 2014; (ii) determine the types and processes of landscape dynamics; and (iii) assess the landscape fragmentation and habitat loss over time. Supervised classification of multi-temporal Landsat images was used through a pixel-based approach. Post–classification methods included systematic and random change detection, trajectories analysis and landscape fragmentation assessment. The overall accuracies (and Kappa statistics) were of 68.86% (0.63), 91.32% (0.79), 90.66% (0.88) and 91.88% (0.89) for 1972, 1987, 2000 and 2014, respectively. The spatio-temporal analyses indicated that forests, woodlands and savannahs dominated the landscapes during the four dates, though constant areal decreases were observed. The most important dynamic process was the decline of woodlands with an average annual net loss rate of–2%. Meanwhile, the most important land transformation occurred during the transition 2000–2014, due to anthropogenic pressures. Though the most important loss of vegetation greenness occurred in the unprotected areas, the overall analyses of change indicated a declining trend of land cover quality and an increasing landscape fragmentation. Sustainable conservation strategies should be promoted while focusing restoration attention on degraded lands and fragmented ecosystems in order to support rural livelihood and biodiversity conservation.     

基于RS、GIS的奈曼旗土地覆盖/利用变化研究

利用内蒙古奈曼旗1980年、1996年的1：10万的TM遥感影像，采用空间分析和统计分析的方法，研究了1980～1996年来该县土地覆盖／利用变化过程及其自然社会经济驱动机制。结果表明，20世纪80年代以来林地和草地的变化最为显著，林地、草地面积明显增加，沙地和耕地面积减少，其它土地利用类型面积变化不大；景观呈现整体破碎化的趋势，耕地和林地的破碎明显，未利用土地破碎萎缩，土地覆盖／利用向多样化、均匀化方向发展。粮食单产、年均降水量、农业机械动力是草地变化的主要驱动力，农牧民人均纯收人、大牲畜总头数是林地变化的主要驱动力。     

京津冀地区1985–2000期间林地变化的时空格局及其影响因素（英文）

林地是维护生态安全,实现区域可持续发展的根本基础资源。林地变化可能导致一些生态环境问题,包括土壤侵蚀,水资源短缺,干旱加剧以及生物多样性的丧失。本文以景观生态学和逻辑回归模型为基础,探讨了京津冀地区1985-2000期间林地变化的时空格局及其影响因素。格局分析结果表明,林地景观破碎化正在下降和林地形状变得越来越规则。通过建立Logistic回归模型,这项研究旨在探讨这一区域1985-2000期间林地变化的重要变量。对于京津冀地区1985-2000期间林地变化而言,土壤有机质含量,坡度(5°),到最近村庄的距离以及人均国内生产总值是最重要的解释变量。研究表明,空间异质性会影响到林地变化的逻辑回归模型的可预测性。     

城市化过程中半城市化地区社区人居环境特征研究——以厦门市集美区为例

城市化过程中半城市化地区存在着城市化程度由低到高的农村社区、城乡过渡型社区以及居住小区等城市型社区,社区人居环境多样化、多变化。在城市化影响下,这些社区人居环境呈现一定的特征。以厦门市集美区为例,通过选取典型社区,分析其景观格局特征,构建人居环境评价指标体系,对城市化过程中半城市化地区不同类型社区的人居环境特征进行了研究。结果表明:①从农村到城乡过渡型社区,建筑面积比例显著增加,道路面积比例变化不大,而林地和草地面积比例逐渐减少,景观格局逐渐变为景观类型较单一、以现代建筑为优势景观的状态,景观趋于破碎化,形状略趋复杂,城市居住小区各类景观面积比例则相对合理,但景观高度破碎化、形状较规则。②城市化过程中各类型社区人居环境质量均逐渐变好,城乡过渡型社区和农村尤为明显,城市居住小区质量明显高于过渡型社区与农村,且除城中村之外,从农村到城市居住小区社区城市化程度与人居环境质量呈正相关关系。③城市化总体上促进了社区人居环境质量的提高,但对社区人居环境各方面的作用具有不同的规律,对于环境质量、人文环境等方面具有一定的负面影响。     

Combining land transitions and trajectories in assessing forest cover change

One restriction of landscape studies is that land use and cover change is often regarded as irreversible. A highly dynamic landscape in southern Chile was selected to show that forest cover change involves a series of complex transitions and trajectories. Using Landsat images from 1976, 1985, 1999 and 2007 an in-depth analysis of the transition matrix was conducted to separate random and systematic transitions which were grouped into trajectories using a pixel-history approach. Main trajectories were linked to fragmentation indices and farming systems through cluster analysis. Of the 247 trajectories identified, old growth forest persistence comprised 22% of the landscape, whereas deforestation trajectories comprised 20.9% and were mostly composed of changes from old growth forest to shrubland (13.9%). Trajectories of forest degradation from old growth to secondary forest comprised 19.7% of the landscape. The periods 1976-1985 and 1999-2007 concentrated the most systematic deforestation and degradation transitions. In turn, random transitions predominated between 1985 and 1999, probably in response to economic factors that acted suddenly on the landscape during the 80’s, such as the woodchip export and aquaculture booms. A close relationship between landscape fragmentation and the proportion of systematic transitions and farming systems was found; specifically, the highest entropy indices occurred in clusters which exhibited the lowest proportion of systematic transitions and the highest proportion (>70%) of peasant agricultural systems. Understanding the complexity of forest cover change trajectories is relevant for improving the prediction of possible landscape evolutions and establishing landscape management priorities.     

近30年玉门市土地利用与景观格局变化及其驱动力

干旱内陆河流域生态环境非常脆弱,是土地利用和景观格局变化的敏感区域,也是全球环境变化响应比较突出的区域。采用1976年、1989年、2000年和2010年的Landsat遥感影像,利用GIS技术和景观格局分析方法,系统地分析了疏勒河中游玉门市的土地利用和景观格局变化的时空特征,为研究区土地可持续利用政策的制定提供参考和依据。研究结果显示:近34a来,玉门市土地利用和景观格局发生了剧烈变化,土地利用变化经历了"缓慢变化—急剧变化—显著变化"的过程。研究区景观密度增大,多样性和均匀度先减小,后增加;不同斑块间的分离度减小。农业人口增长和经济发展是玉门市土地利用景观格局变化的最直接驱动力,同时还受气候因素和政策因素的影响。