Changes in a Wetland Ecosystem: A Vegetation Reconstruction Study Based on Historical Panchromatic Aerial Photographs and Succession Patterns

This paper presents the methodology and results of a vegetation reconstruction method based on botanical sampling, the knowledge of succession pattern, digital photograph-interpretation and automatic delineation via image segmentation. The aim is to provide a methodology for interpretation of archived black-and-white aerial photographs, which can be applied at other study sites. Our study area was the Nyíres-tó mire in the Bereg Plain (NE Hungary). Initially, botanical sampling was carried out, and this was followed by separation and identification of current vegetation types. In our study we selected automatic delineation using multi-resolution image segmentation as the method for vegetation mapping. Based on the present-day vegetation map produced and the known successional pathway of the mire, archive aerial photographs were analyzed separately in reverse chronological order to derive plant associations present at the different photograph acquisition dates. With this method we were able to make a chronological sequence of digital vegetation maps over a period of almost fifty years (1956–2002). The analysis of vegetation maps showed that forest cover increased steadily until 1988. After an artificial water supply was introduced (in 1986), the spread of tree-dominated associations became slower, and the relative cover of the different vegetation types reached a stable state.     

Seed Dispersal Patterns by Large Frugivorous Mammals in a Degraded Mosaic Landscape

Seed dispersal by Red fox (Vulpes vulpes), Stone marten (Martes foina), and Wild boar (Sus scrofa) was analyzed in an extensively degraded mosaic landscape in Sierra Nevada (SE Spain). The main objective was to determine whether seed dispersal by mammals was related to habitat degradation within a mosaic of adjacent degraded patches mixed with native forest and thereby to determine the potential role of mammals as seed dispersers in degraded landscape units. For three consecutive years, mammal feces were collected in the fruit production period, extracting all seeds of woody species found therein and analyzing their viability. Feces were collected in three different plots for each of five different landscape units: shrubland, native forest, and dense, cleared, and fenced reforestation stands. Seeds from 16 woody species (which represent more than a half of the total fleshy‐fruited woody species available) were recorded, although some agrarian species are also introduced in a low percentage of the scats. Seeds showed a high viability rate for all dispersed species, irrespective of the mammal disperser. No differences in species composition appeared in the overall landscape units or in the seed density between degraded habitats. Due to the small patch size, the high viability of dispersed seeds, and the large home range of the large mammals, these three animal species act as efficient seed dispersers for a diverse assemblage of woody plant species regardless of the habitat type within this degradation framework. This fact has important consequences for the biodiversity recuperation in these degraded habitats, principally in pine plantations.     

Socio-Economics and Vegetation Change in Urban Ecosystems: Patterns in Space and Time

By 2050, 70% of the Earth’s human population will live in urban areas. Urbanization can have a devastating impact on local ecosystems, but these impacts vary across time and space. Identifying links between spatiotemporal change in urban ecosystems and neighborhood socio-economics is crucial to management aimed at maintaining flora and fauna in urban areas. Here, we tracked 20 years of socio-economic change and 15 years of vegetation change in 32 residential neighborhoods in south-eastern Australia. Regression models that explicitly accounted for a time lag between neighborhood socio-economic characteristics and vegetation response explained more variation in vegetation cover than models that ignored the effects of time. Also, relationships between vegetation and socio-economic factors were stronger in later years for the same neighborhoods suggesting the influence of socio-economics is more readily identified in established neighborhoods. Socio-economic variables alone, or in combination with biophysical variables, were better predictors of vegetation cover than only biophysical variables. Across space, vegetation cover had a negative quadratic relationship with neighborhood housing density, peaking at mid-density values, and a positive relationship with education level and immigration status (the percentage of residents with a non-Australian background). Over time, housing density had a positive relationship with vegetation cover, reflecting an increase in vegetation as neighborhoods develop. Our results highlight the need to understand temporal context when attempting to explain contemporary patterns in vegetation cover and the increasing importance of socio-economic factors in influencing cover as neighborhoods become established. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Landscape Patterns and Legacies Resulting from Large, Infrequent Forest Disturbances

We review and compare well-studied examples of five large, infrequent disturbances (LIDs)—fire, hurricanes, tornadoes, volcanic eruptions, and floods—in terms of the physical processes involved, the damage patterns they create in forested landscapes, and the potential impacts of those patterns on subsequent forest development. Our examples include the 1988 Yellowstone fires, the 1938 New England hurricane, the 1985 Tionesta tornado, the 1980 eruption of Mount St. Helens, and the 1993 Mississippi floods. The resulting landscape patterns are strongly controlled by interactions between the specific disturbance, the abiotic environment (especially topography), and the composition and structure of the vegetation at the time of the disturbance. The very different natures of these interactions yield distinctive temporal and spatial patterns and demand that ecologists increase their knowledge of the physical characteristics of disturbance processes. Floods and fires can occur over a long period, whereas volcanic eruptions and wind-driven events often last for no more than a few hours or days. Tornadoes and floods produce linear patterns with sharp edges, but fires, volcanic eruptions, and hurricanes can affect broader areas, often with gradual transitions of disturbance intensity. In all cases, the evidence suggests that LIDs produce enduring legacies of physical and biological structure that influence ecosystem processes for decades or centuries. Received 14 July 1998; accepted 6 October 1998.     

Spider Trait Assembly Patterns and Resilience under Fire-Induced Vegetation Change in South Brazilian Grasslands

Disturbances induce changes on habitat proprieties that may filter organism''s functional traits thereby shaping the structure and interactions of many trophic levels. We tested if communities of predators with foraging traits dependent on habitat structure respond to environmental change through cascades affecting the functional traits of plants. We monitored the response of spider and plant communities to fire in South Brazilian Grasslands using pairs of burned and unburned plots. Spiders were determined to the family level and described in feeding behavioral and morphological traits measured on each individual. Life form and morphological traits were recorded for plant species. One month after fire the abundance of vegetation hunters and the mean size of the chelicera increased due to the presence of suitable feeding sites in the regrowing vegetation, but irregular web builders decreased due to the absence of microhabitats and dense foliage into which they build their webs. Six months after fire rosette-form plants with broader leaves increased, creating a favourable habitat for orb web builders which became more abundant, while graminoids and tall plants were reduced, resulting in a decrease of proper shelters and microclimate in soil surface to ground hunters which became less abundant. Hence, fire triggered changes in vegetation structure that lead both to trait-convergence and trait-divergence assembly patterns of spiders along gradients of plant biomass and functional diversity. Spider individuals occurring in more functionally diverse plant communities were more diverse in their traits probably because increased possibility of resource exploitation, following the habitat heterogeneity hypothesis. Finally, as an indication of resilience, after twelve months spider communities did not differ from those of unburned plots. Our findings show that functional traits provide a mechanistic understanding of the response of communities to environmental change, especially when more than one trophic level is considered.     

Imprinting on the Heart: Photography and Contemporary Yolngu Mournings

This article examines the ways photographs of the recently deceased have come to occupy a central place in Yolngu grieving practices. Harnessing the potentially traumatic ontological qualities of oscillating absence–presence that are inherent in such images, I show how Yolngu in Northern Australia use this affective force as a way to refigure and reconstitute embodied and sensuously mediated relationships between the living and the dead. With vision simultaneously allowing corporeal permeability and expansion, mourners impress the image of the deceased within them, through the eyes to the heart as the fleshly organ of affect, associative recollection, and lived intersubjectivity.     

Vegetation Components of a Subtropical Rural Landscape in China

To assess the overall vegetation changes and their ecological significance, following landscape evolution, plant composition and physical structures of the homegardens (woodlots and vegetation patches with hedgerow fence) and field boundaries were examined in the rural landscape of subtropical China in order to determine their ecological significance. Field surveys on landscape changes and plant composition were carried out in two typical villages in the Yangtze river plain. Analysis of landscape changes and plant composition showed that the rural landscape is diverse both in terms of types of elements and plant species. The vegetation types in the area have undergone frequent alterations by human beings following major changes of landscape management due to economic and social reforms. The plant diversity of the various vegetation types in the area is related to the duration of colonization of the vegetation type, the extent of disturbance by human beings, and the physical structure diversity of the vegetation type. In the discussion, the plant diversity and heterogeneity of the physical environment in any vegetation type is of importance for the ecological sustainability of the landscape.     

Historical Maps from Modern Images: Using Remote Sensing to Model and Map Century-Long Vegetation Change in a Fire-Prone Region

Understanding the age structure of vegetation is important for effective land management, especially in fire-prone landscapes where the effects of fire can persist for decades and centuries. In many parts of the world, such information is limited due to an inability to map disturbance histories before the availability of satellite images (~1972). Here, we describe a method for creating a spatial model of the age structure of canopy species that established pre-1972. We built predictive neural network models based on remotely sensed data and ecological field survey data. These models determined the relationship between sites of known fire age and remotely sensed data. The predictive model was applied across a 104,000 km² study region in semi-arid Australia to create a spatial model of vegetation age structure, which is primarily the result of stand-replacing fires which occurred before 1972. An assessment of the predictive capacity of the model using independent validation data showed a significant correlation (r_s = 0.64) between predicted and known age at test sites. Application of the model provides valuable insights into the distribution of vegetation age-classes and fire history in the study region. This is a relatively straightforward method which uses widely available data sources that can be applied in other regions to predict age-class distribution beyond the limits imposed by satellite imagery.     

基于遥感的植被覆盖变化景观分析——以北京海淀区为例

提出了基于土地利用分类的植被覆盖度计算的亚象元模型,针对不同的植被覆盖类型,综合利用“等密度模型“和“变密度模型“计算植被覆盖度,使其能有效地从遥感数据中提取植被覆盖信息。在GIS的支持下,应用该模型对北京海淀区1975年、1991年和1999年5月份植被覆盖度进行计算,并着重对其景观变化过程进行了分析。研究结果表明：1975至1999年来,海淀区植被覆盖整体表现为增加趋势,但空间格局分布不均衡,全植被覆盖区和高植被覆盖区过分集中在西北部狭长地带,东南部则多为低植被覆盖区,反映出北京海淀区土地利用的结构特征。     

山西植被空间格局及演替简

在ArcGIS软件中采集1984年和2005年山西植被类型的图形,得到山西群系、森林、灌丛、草本植被及栽培植被的图形及面积,用叠置分析和景观格局分析方法研究植被的空间分布及其演替、空间格局及其变化。森林在西南部相对集中分布,在西北角增加明显,它在山西植被中所占面积及比重都最小,最为破碎。油松林在山西森林中占优势,恢复森林主要是油松林、小叶杨林、辽东栎林。1984年灌丛的面积在植被中最大,所占比例也最高,超过50%,集中连片分布面积较大,但灌丛缩减迅速,主要在中南部,在山西植被中遭破坏最为严重。沙棘、虎榛子灌丛和黄栌、连翘灌丛对灌丛的影响最大。草本植被主要在北部减少,在中南部分散增加,更加破碎。白羊草草丛在山西草本植被中占优势,蒿、禾草草原和百里香、禾草草原变化最大。栽培植被明显增加,在植被中所占比重急剧增加,成为山西优势植被。森林、栽培植被分别增加24.3%、71.5%,而灌丛、草本植被却分别减少70.3%,15.6%,演替主要是人为因素造成的。     

Landscape and Vegetation Effects on Avian Reproduction on Bottomland Forest Restorations

ABSTRACT Forest restoration has been undertaken on >200,000 ha of agricultural land in the Mississippi Alluvial Valley, USA, during the past few decades. Decisions on where and how to restore bottomland forests are complex and dependent upon landowner objectives, but for conservation of silvicolous (forest-dwelling) birds, ecologists have espoused restoration through planting a diverse mix of densely spaced seedlings that includes fast-growing species. Application of this planting strategy on agricultural tracts that are adjacent to extant forest or within landscapes that are predominately forested has been advocated to increase forest area and enhance forested landscapes, thereby benefiting area-sensitive, silvicolous birds. We measured support for these hypothesized benefits through assessments of densities of breeding birds and reproductive success of 9 species on 36 bottomland forest restoration sites. Densities of thamnic (shrub-scrub dwelling) and silvicolous birds, such as yellow-breasted chat (Icteria virens), indigo bunting (Passerina cyanea), and white-eyed vireo (Vireo griseus) were positively associated with 1) taller trees, 2) greater stem densities, and 3) a greater proportion of forest within the landscape, whereas densities of birds associated with grasslands, such as dickcissel (Spiza americana) and red-winged blackbird (Agelaius phoeniceus), were negatively associated with these variables. Vegetation structure, habitat edge, and temporal effects had greater influence on nest success than did landscape effects. Taller trees, increased density of woody stems, greater vegetation density, and more forest within the landscape were often associated with greater nest success. Nest success of grassland birds was positively related to distance from forest edge but, for thamnic birds, success was greater near edges. Moreover, nest success and estimated fecundity of thamnic species suggested their populations are self-sustaining on forest restoration sites, whereas these sites are likely population sinks for grassland and open-woodland species. We recommend restoration strategies that promote rapid development of dense forest stands within largely forested landscapes to recruit breeding populations of thamnic and silvicolous birds that have reproductive success sufficient to sustain their populations.     

Ecological Thresholds in the Savanna Landscape: Developing a Protocol for Monitoring the Change in Composition and Utilisation of Large Trees

Background

Acquiring greater understanding of the factors causing changes in vegetation structure - particularly with the potential to cause regime shifts - is important in adaptively managed conservation areas. Large trees (≥5 m in height) play an important ecosystem function, and are associated with a stable ecological state in the African savanna. There is concern that large tree densities are declining in a number of protected areas, including the Kruger National Park, South Africa. In this paper the results of a field study designed to monitor change in a savanna system are presented and discussed.

Methodology/Principal Findings

Developing the first phase of a monitoring protocol to measure the change in tree species composition, density and size distribution, whilst also identifying factors driving change. A central issue is the discrete spatial distribution of large trees in the landscape, making point sampling approaches relatively ineffective. Accordingly, fourteen 10 m wide transects were aligned perpendicular to large rivers (3.0–6.6 km in length) and eight transects were located at fixed-point photographic locations (1.0–1.6 km in length). Using accumulation curves, we established that the majority of tree species were sampled within 3 km. Furthermore, the key ecological drivers (e.g. fire, herbivory, drought and disease) which influence large tree use and impact were also recorded within 3 km.

Conclusions/Significance

The technique presented provides an effective method for monitoring changes in large tree abundance, size distribution and use by the main ecological drivers across the savanna landscape. However, the monitoring of rare tree species would require individual marking approaches due to their low densities and specific habitat requirements. Repeat sampling intervals would vary depending on the factor of concern and proposed management mitigation. Once a monitoring protocol has been identified and evaluated, the next stage is to integrate that protocol into a decision-making system, which highlights potential leading indicators of change. Frequent monitoring would be required to establish the rate and direction of change. This approach may be useful in generating monitoring protocols for other dynamic systems.     

基于大样地油松种群的地统计学分析

在对山西省灵空山国家级自然保护区4 hm2样地内油松种群调查的基础上,采用地统计学的半方差分析法对油松种群的空间分布格局进行了研究,并用克里金插值法绘制了不同径级油松种群胸径的等值线图。结果表明:油松种群径级Ⅰ、Ⅲ、Ⅳ的最优半方差拟合模型均为指数模型,径级Ⅱ的最优拟合模型为球状模型,说明4个径级都为聚集分布且均为中等的空间相关性;油松种群径级Ⅰ、Ⅱ、Ⅲ、Ⅳ的空间自相关范围分别为23.4、15.2、11.1、24.9 m,分维数大小依次为径级Ⅱ(1.999)径级Ⅲ(1.995)径级Ⅳ(1.973)径级Ⅰ(1.969)。以树高为变量作半方差分析的结果与以胸径作为变量的分析结果基本一致,且以树高为变量进行的类似分析也进一步证实了该结果的准确性。利用Surfer软件绘制的Kriging图直观反映了油松种群空间分布的斑块聚集效果,即油松种群空间格局纹理图。本文利用地统计学的半方差分析法和Kriging插值方法相结合弥补了传统格局分析方法的不足,能精确直观地反映出油松种群个体的空间分布、斑块的聚集效果等,可为植物空间分布格局的分析提供有效的研究方法。     

Effects of Climate Change and a Doubling of CO2 on Vegetation Diversity

A model is presented for predicting the response of global familydiversity to global environmental change. The model assumesthat three primary mechanisms determine diversity: the capacityto survive the absolute minimum temperature of a site, the abilityto complete the life cycle in a given length and warmth of thegrowing season, and the capacity to expand leaves in a definedregime of precipitation and vegetation transpiration. The directeffects of CO₂ on vegetation transpiration are also included. About one-third of the floristic regions of the world exhibitincreased diversity with a 3°C increase in temperature,a 10% increase in precipitation, and a doubling of the CO2 concentration.The addition of CO₂ offsets the increased rates of transpiration,caused by global warming through its capacity to reduce transpiration.As a consequence, the diversity of dry regions displayed thegreatest increase in diversity due to increased CO₂.     

The Influence of Change in Marital Status on Weight Change Over One Year

Marital status is an influence on body weight. Changes in marital status and body weight were examined in the National Survey of Personal Health Practices and Consequences, a telephone survey of 2,436 adults interviewed twice approximately 1 year apart. Two statistical methods for analyzing weight change were compared, and both produced similar results: regression analysis of weight change and regression analysis of weight at follow-up controlling for baseline weight. The findings revealed that women who entered marriage had greater weight change than women who remained married. Analysis of weight gain and weight loss separately showed that women who became married lost less weight than those who remained married. For men, there were no statistically significant relationships between marital change and weight change over a 1-year period. These findings support other literature showing that marital status plays a role in body weight changes. The results suggest gender differences may exist in the rate of body weight change after marriage, with more immediate changes in women than men.     

基于唐诗文本挖掘的关中地区人文景观格局研究

关中地区作为中国历史上最早的“天府之国”,拥有丰富的自然与人文资源和独特的人文景观格局。对近400首描写关中风貌的唐代诗词进行筛选梳理,利用文本挖掘技术,通过可视化分析将关中地区划分为长安故都、行宫别苑、山水形胜、田园意境和雄关遗迹5种景观空间类型,并进一步对人文景观情感特征、景观空间分布特征和空间语义网络特征展开分析,结果表明：不同类型景观空间的词条语义有明显的相似性特征,关中地区形成了以“绿”“素”“青”“朱”为主的景观色彩分布格局,人文景观情感在区域中体现出明显的空间分异。