A model of arctic tundra vegetation derived from topographic gradients

We present a topographically-derived vegetation model (TVM) that predicts the landscape patterns of arctic vegetation types in the foothills of the Brooks Range in northern Alaska. In the Arctic there is a strong relationship between water and plant structure and function and TVM is based on the relationships between vegetation types and slope (tan ) and discharge (), two independent variables that can be easily derived from digital terrain data. Both slope and discharge relate to hydrological similarity within a landscape: slope determines the gravitational hydrological gradient and hence influences flow velocity, whereas discharge patterns are computed based on upslope area and quantify lateral flow amount. TVM was developed and parameterized based on vegetation data from a small 2.2 km² watershed and its application was tested in a larger 22km² region. For the watershed, TVM performed quite well, having a high spatial resolution and a goodness-of-fit ranging from 71–78%, depending on the functions used. For the larger region, the strength of the vegetation types predictions drops somewhat to between 56–59%. We discuss the various sources of error and limitations of the model for purposes of extrapolation.     

Historic range of variability in landscape structure in subalpine forests of the Greater Yellowstone Area,USA

A measure of the historic range of variability (HRV) in landscape structure is essential for evaluating current landscape patterns of Rocky Mountain coniferous forests that have been subjected to intensive timber harvest. We used a geographic information system (GIS) and FRAGSTATS to calculate key landscape metrics on two ∼130,000-ha landscapes in the Greater Yellowstone Area, USA: one in Yellowstone National Park (YNP), which has been primarily shaped by natural fires, and a second in the adjacent Targhee National Forest (TNF), which has undergone intensive clearcutting for nearly 30 years. Digital maps of the current and historical landscape in YNP were developed from earlier stand age maps developed by Romme and Despain. Maps of the TNF landscape were adapted from United States Forest Service Resource Information System (RIS) data. Key landscape metrics were calculated at 20-yr intervals for YNP for the period from 1705-1995. These metrics were used to first evaluate the relative effects of small vs. large fire events on landscape structure and were then compared to similar metrics calculated for both pre- and post-harvest landscapes of the TNF. Large fires, such as those that burned in 1988, produced a structurally different landscape than did previous, smaller fires (1705-1985). The total number of patches of all types was higher after 1988 (694 vs. 340-404 before 1988), and mean patch size was reduced by almost half (186 ha vs. 319-379 ha). The amount of unburned forest was less following the 1988 fires (63% vs. 72-90% prior to 1988), yet the number of unburned patches increased by nearly an order of magnitude (230 vs. a maximum of 41 prior to 1988). Total core area and mean core area per patch decreased after 1988 relative to smaller fires (∼73,700 ha vs. 87,000-110,000 ha, and 320 ha vs. 2,123 ha, respectively). Notably, only edge density was similar (17 m ha⁻¹ after 1988) to earlier landscapes (9.8-14.2 m ha⁻¹).Three decades of timber harvesting dramatically altered landscape structure in the TNF. Total number of patches increased threefold (1,481 after harvest vs. 437 before harvest), and mean patch size decreased by ∼70% (91.3 ha vs. 309 ha). None of the post-harvest landscape metrics calculated for the TNF fell within the HRV as defined in YNP, even when the post-1988 landscape was considered. In contrast, pre-harvest TNF landscape metrics were all within, or very nearly within, the HRV for YNP. While reference conditions such as those identified by this study are useful for local and regional landscape evaluation and planning, additional research is necessary to understand the consequences of changes in landscape structure for population, community, ecosystem, and landscape function. This revised version was published online in July 2006 with corrections to the Cover Date.     

Native-exotic richness relationships in second-growth forests differ along a gradient of land-use history

Landscape Ecology - The relationship between native and non-native species richness is influenced by drivers including disturbance history and environmental character. Disturbance influences...     

Environmental factors and ecological processes controlling vegetation patterns in boreal forests

An individual tree model of forest dynamics was used to examine the environmental and ecological factors controlling forest vegetation patterns in upland boreal forests of North America. Basic life history traits that characterized the regeneration, growth, and death of individual trees were combined with species-specific responses to important environmental factors. This model simulated forest structure and vegetation patterns in conifer, hardwood, and mixed conifer-hardwood forests and woodlands in several bioclimatic sub-regions of the North American boreal forest zone. Model testing identified the processes and parameters required to understand the ecology of upland boreal forests and weaknesses in our current understanding of these processes. These factors included climate, solar radiation, soil moisture, soil temperature and permafrost, the forest floor organic layer, nutrient availability, forest fires, and insect outbreaks. Model testing also identified which of these factors were important in each bioclimatic sub-region.     

A trait-based typification of urban forests as nature-based solutions

Urban forests as nature-based solutions (UF-NBS) are important tools for climate change adaptation and sustainable development. However, achieving both effective and sustainable UF-NBS solutions requires diverse knowledge. This includes knowledge on UF-NBS implementation, on the assessment of their environmental impacts in diverse spatial contexts, and on their management for the long-term safeguarding of delivered benefits. A successful integration of such bodies of knowledge demands a systematic understanding of UF-NBS. To achieve such an understanding, this paper presents a conceptual UF-NBS model obtained through a semantic, trait-based modelling approach. This conceptual model is subsequently implemented as an extendible, re-usable and interoperable ontology. In so doing, a formal, trait-based vocabulary on UF-NBS is created, that allows expressing spatial, morphological, physical, functional, and institutional UF-NBS properties for their typification and a subsequent integration of further knowledge and data. Thereby, ways forward are opened for a more systematic UF-NBS impact assessment, management, and decision-making.     

Modelling tree canopy cover and evaluating the driving factors based on remotely sensed data and machine learning

Quantifying urban tree cover is important to ensure sustainable urban ecosystem. This study calculates urban percent tree cover (PTC) for Bursa city, Turkey from Sentinel-2 data and evaluates the driving factors of PTC using an Artificial Neural Network-Multi Layer Perception (ANN-MLP) approach. For the PTC calculation, a Regression Tree (RT) analysis was performed using several vegetation indices (NDVI, LAI, fCOVER, MSAVI2, and MCARI) to improve accuracy. Socio-economic, topographic, and biophysical variables were incorporated into the ANN-MLP approach to evaluate the factors that drive urban PTC. A PTC prediction map was generated with an accuracy of 0.95 and a coefficient of determination of 0.87. The ANN-MLP training process yielded a correlation coefficient value of 0.71 and an R-square of 0.82 was achieved between the predicted ANN-MLP and observed tree cover maps. A priority tree cover map was generated considering statistical relationships between the factors and the ANN-MLP prediction map in addition to visual interpretations at the urban scale. Results demonstrate that, unlike other urban forms, PTC has a statistically negative relationship with the gross dwelling density (R2 =0.31). Topographic variables including slope and DEM were positively correlated with PTC with the R2 value of 0.80 and 0.72 respectively. The integration of remote sensing data with vegetation indices and driving factors yielded accurate prediction for identifying and evaluating the variability in the urban PTC.     

The recent landscape history of Limpach valley, Switzerland: considering three empirical hypotheses on driving forces of landscape change

Understanding global landscape dynamics is a core challenge for the newly emerged field of land change science. Such an understanding requires insights into general pattern of landscape changes and the related driving forces. Many case studies of landscape change exist, but only few attempts have been made, to synthesize the results and to search for general pattern. We suggest that applying hypotheses on driving forces of landscape change derived from one case study in another region as a promising way to advance towards a more integrative view on landscape dynamics. Based on the conclusions drawn in a case study conducted in Godmanchester (Quebec, Canada; Domon and Bouchard 2007), we formulated three hypotheses and discussed them in a case study on landscape change in the Limpach valley, Switzerland. We confirm the importance of geomorphological characteristics for landscape development (hypothesis 1) and our analysis also supports the second hypothesis, which states that changes in demand for certain resources result in landscape change. However, we suggest replacing the term resources by the more encompassing concept of goods and services. The third hypothesis, which states that technological transformations stand at the beginning of landscape change, also was confirmed. Technologies have to be affordable, socially accepted, and corresponding to a demand, to be implemented on a large scale. This will cause a technological transformation, which then—depending on the specifics of the technology applied—becomes relevant for landscape development. We conclude with three reworded hypotheses on driving forces of landscape change and we hope that they will be tested and further developed in other case studies.     

都市圈边缘带土地利用变化及人为驱动力研究

都市圈边缘带区位特殊,其土地利用的变化规律及驱动过程特征明显。以重庆都市圈边缘带的沙坪坝区为例,利用2006、2013年的TM遥感影像,结合RS、GIS技术分析研究区土地利用变化情况,利用SPSS分析其驱动因子。结果表明:2006和2013年间各类型土地转换明显,林地和建设用地呈增加趋势,其中林地增加量最大,增加了48.41km2,建设用地增加了34.17km2。水域和耕地呈减少趋势,耕地减少量最大,减少了45.08km2,水域减少了37.50km2。通过主成分分析得出,政策指向、社会驱动、经济刺激等是土地转换的主要驱动力,并据此提出了应对土地利用变化的措施。     

Review on the multi-scale interactions of urban forests and atmospheric particles: Affecting factors are scale-dependent among tree,stand and region

Increasing studies worldwide have examined the impacts of urban forests on mitigating atmospheric particulate matter (PM) over the past decades. These scattered studies revealed the aerodynamics of atmospheric PM deposited on urban forests, as well as the various factors influencing the PM capture and removal by urban forests. However, these evidences are varying and even contradictory, and the affecting factors do not follow a universal pattern. In addition, these studies generally have been conducted in a specific scale such as leaf, stand and city without considering the multi-scale associations and incorporations. This literature review tried to address the associations of urban forest and PM removal across single tree, stand and regional scales, and summarized the confounding factors for PM capture and removal within each scale. Particle size and local meteorology have significant impacts across scales. For an individual tree, PM capture and removal capacity are largely determined by the leaf morphology and epidermal structures, but at the stand scale, the biophysical characteristics and configurational designs of urban forests are the essential factors. At the city and regional scale, the determinants are the fraction of forest coverage, as well as background pollution levels. The literature collation emphasizes the necessity of concerning the appropriate factors responding to the specific scale when quantifying and evaluating PM capture and removal by urban forests, and warrants a multi-scale research paradigm and inclusive modeling evaluation incorporating the confounding factors from multiple scales for PM capture and removal by urban forests.     

Ecological functions and human benefits of urban forests

The recent sprawl of urbanization in the Eastern U.S. perpetuated by population growth and economic success has caused landscapes to become vulnerable to degradation. As urban development encroaches on such landscapes, various anthropogenic stressors are introduced including air pollution, land conversion, and alterations in watershed hydrology. Across various disciplines, urban forests have been presented as a method to ameliorate human and environmental health in metropolitan environments. Understanding how to incorporate urban forestry into city design is critical and urban planners would benefit from a review that holistically describes the diverse set of services urban forests have to offer. We conducted a review to highlight the ecological functions and human benefits of urban forests and to identify gaps in the literature. We synthesized the findings of research studies in the last 20 years to illuminate the human, abiotic, and biotic services of urban forestry. As environmental quality is rapidly deteriorating in anthropogenic environments, our findings suggest city planners should consider trees as a method of mitigation to alleviate these impacts. Ultimately, when managing urban forests, an interdisciplinary approach involving all levels of governance is necessary to ensure the maximum potential of urban trees. Through this study, the consolidated research can aid in sustainable development and innovation to combat the anthropogenic stressors associated with the sprawl of urbanization.     

Testing landscape metrics as indicators of habitat loss and fragmentation in continuous eucalypt forests (Queensland,Australia)

Landscape metrics are widely applied in landscape ecology to quantify landscape structure. However, many are poorly tested and require rigorous validation if they are to serve as reliable indicators of habitat loss and frag-mentation, such as Montreal Process Indicator 1.1e. We apply a landscape ecology theory, supported by explor-atory and confirmatory statistical techniques, to empirically test landscape metrics for reporting Montreal Process Indicator 1.1e in continuous dry eucalypt forests of sub-tropical Queensland, Australia. Target biota examined included: the Yellow-bellied Glider (Petaurus australis); the diversity of nectar and sap feeding glider species including P. australis, the Sugar Glider P. breviceps, the Squirrel Glider P. norfolcensis, and the Feathertail GliderAcrobates pygmaeus; six diurnal forest birds species; total diurnal bird species diversity; and the density of nec-tar-feeding diurnal bird species. Two scales of influence were considered: the stand-scale (2 ha), and a series of radial landscape extents (500 m –2 km;78–1250 ha) surrounding each fauna transect. For all biota, stand-scale structural and compositional attributes were found to be more influential than landscape metrics. For the Yellow-belliedGlider, the proportion of trace habitats with a residual element of old spotted-gum/ironbark eucalypt trees was a significant landscape metric at the 2 km landscape extent. This is a measure of habitat loss rather than habitat fragmentation. For the diversity of nectar and sap feeding glider species, the proportion of trace habitats with a high coefficient of variation in patch size at the 750 m extent was a significant landscape metric. None of the landscape metrics tested was important for diurnal forest birds. We conclude that no single landscape metricadequately captures the response of the regions forest biota per se. This poses a major challenge to regional reporting of Montreal Process Indicator 1.1e, fragmentation of forest types.This revised version was published online in May 2005 with corrections to the Cover Date.     

The effect of mifepristone on natural killer subsets of peripheral blood and decidua in early pregnancy

AIM: To investigate the effect of mifepristone on natural killer(NK) subpopulations of peripheral blood and decidua in early pregnancy. METHODS: Flow cytometry was used to detect the expression of CD56 and CD16 on lymphocytes of decidua and peripheral blood in early pregnancy, mifepristone-treated pregnancy. RESULTS: The percentages of different natural killer subsets in peripheral blood between early pregnancy and mifepristone-treated pregnancy were almost identical. The serum levels of estradiol and progesterone in mifepristone-treated pregnancy were slightly higher than in early pregnancy. The percentage of decidual CD56⁺NK cell in early pregnancy was significantly higher than in mifepristone-treated pregnancy. The CD56⁺NK cells were predominant lymphocyte population of decidua in mifepristone-treated pregnancy, but in which the CD56⁺CD16⁺ and CD16⁺NK cells were major lymphocyte subpopulations of peripheral blood. CONCLUSION: Mifepristone acted principally on feto-maternal interface, it blocked the proliferation and differentiation of decidual CD56⁺NK cells and induced embryo immune rejection.     

Extinction risk of wood-living model species in forest landscapes as related to forest history and conservation strategy

Dead wood is a critical resource for biodiversity in boreal forests. We analysed the persistence of five model species inhabiting dead wood. By parameterising a metapopulation model (the incidence function model), the model species were all assigned characteristics that makes it likely that they have disappeared from some (20%) forest landscapes with a long history of forest management. In the metapopulation model, a forest stand (5 ha) was regarded as a habitat patch. The amount of habitat in each patch was obtained from models of dead wood dynamics of Norway spruce in central Sweden. Dead wood generated by altered management over the entire landscape was found to be less efficient in reducing extinction risks in comparison to the same amount of dead wood generated by protecting reserves. Because generation of dead wood by altered management is often less expensive than setting aside reserves, it is difficult to determine which conservation measure is most cost-efficient. In a landscape subjected to forestry for the first time, it was better to preserve a few large reserves than many small ones. However, in a managed, highly fragmented forest landscape it was better to set aside many small reserves. The reason for this was that small plots with high habitat quality could be selected, while large reserves originally contained habitats both of high and low quality, and the rate of habitat quality increase was low. A strategy for biodiversity conservation in a managed forest landscape should include information about the history of the landscape, the current amount and spatial distribution of forest habitats, and the potential for rapid restoration of forest habitats, both on managed and unmanaged forest land.     

The influence of the topographic position within highlands of Western Rwanda on the interactions between banana (Musa spp. AAA-EA), parasitic nematodes and soil factors

Soil properties vary according to the topography. They affect water uptake and root exploration in the soil. Consequently, they may also influence the spread of plant–parasitic nematodes. This study reports on the effect of toposequence-related variations in soil on banana yields, foliar nutrient status, and nematode impact. Twenty banana plots were visited within 6 hills/valleys at each of the three toposequence positions: valley bottom, mid-slope and crest. Important variability in plant growth, nutrition and soil properties was observed within the toposequence. Significantly better plant growth (height and girth) was observed in the valley bottoms, where banana bunch weight was 1.7–3.4 kg higher (although not significant) than at upper toposequence positions. Best plant growth was observed in valley bottoms in contrast to the highest N and K foliar deficiencies in this position. Plants in the valley bottoms had higher foliar Ca and Mg, and K compared to those in the crest. Plants in the mid-slope had greater percentage of dead roots (19.1%), compared to the plants in the valley bottoms (12.3%) and the crest (14.2%). Soils in the valley bottoms were deeper, sandier, with lower organic matter, lower N, and K compared to the soils at higher toposequence. Nematodes likely play a key role in banana root damage, however, their effect appear to be in relation to various soil factors at each position. The abundance of Pratylenchus goodeyi had generally limited impact on banana yields in fields having less than 5% slope (crest and valley bottom) where soil conditions were more optimal for root growth. However, in the presence of increased run-off on steeper middle slopes, root death was increased even under moderate pressure from P. goodeyi.     

Characteristics of the urban forests in arctic and near-arctic cities

The urban forest of three arctic and near-arctic cities (Murmansk in Russia, Nuuk in Greenland, and Reykjavik in Iceland) were surveyed to determine tree species composition and structure. Interviews with local authorities were conducted to learn about the history of urban tree planting. The urban forests of all three cities were composed of a limited number of trees and tree species due to abiotic constraints of the arctic and near-arctic environment. These limitations include: low temperature, short growing season, high wind velocity and permafrost. A total of 28 species were observed in the three cities. Only three of these (Alnus incana (L.) Moench, Picea abies (L.) Karst., Betula pubescens Ehrh., and Salix glauca L.) were observed in all three of the cities. Planting designs that created windbreaks for pedestrians were common along streets in Murmansk and Reykjavik. Street trees have not yet been introduced in Nuuk, but trees were found in cemeteries, parks, and on private property. Older portions of cemeteries in all three cities were characterized by trees planted directly on graves. These grave trees were the first trees to be introduced in these cities. Subsequently, ‘trial and error’ was used by local residents to plant trees. Much of these plantings failed. In recent times arboreta were established near all three cities to identify species suited for planting under arctic and near-arctic conditions. Trees identified in these test gardens are now being planted in Murmansk and Reykjavik.     

Percentage change on natural killer subsets of peripheral blood and decidua in between normal early pregnancy and spontaneous abortion

AIM: To determinate the percentage change on natural killer(NK) subsets of peripheral blood and decidua in between normal early pregnancy and spontaneous abortion. METHODS: Flow cytometry was used to detect the expression of CD56 and CD16 on lymphocytes of decidua and peripheral blood in normal early pregnancy and spontaneous abortion. RESULTS: In peripheral blood, the percentage of CD56⁺ of spontaneous abortion tended to decrease in comparison with normal early pregnancy, and the percentage of CD56⁺CD16⁺ in spontaneous abortion was significantly less than that in normal early pregnancy. The percentages of different natural killer subsets in decidua of spontaneous abortion were significantly lower than those in decidua of normal early pregnancy. CONCLUSION: The decrease of CD56⁺NK cells in decidua may be one of causes for abortion, the loss of CD56⁺ and CD56⁺CD16^+NKcells in peripheral blood could have a diagnostic value for spontaneous abortion.     

The landscape history of Godmanchester (Quebec,Canada): two centuries of shifting relationships between anthropic and biophysical factors

Taking into consideration ecological aspects in land management requires an understanding of the processes and dynamics that create landscapes. To achieve this understanding demands that landscapes be studied as a biophysical and social reality, and that phenomena be analyzed within a historical perspective. Based on the research of a multidisciplinary team over the last 25 years, this paper proposes to reconstitute the landscape of Godmanchester (Quebec, Canada) from the pre-colonial period (1785) to today (2005). Using various methods and sources of data, seven stages of evolution were identified: (1) the pre-colonial period, (2) the first settlements, (3) the first agricultural developments, (4) the maximum development of agricultural activities, (5) the concentration of agricultural activities, (6) the intensification of agricultural activities, and (7) the importance of new amenities. First, these results allowed us to identify three sets of fundamental factors that are necessary to understanding the landscape changes, the geomorphological characteristics, the socio-economic demands, and the technological transformations. Second, the results highlight the key elements and the perspectives that are appropriate to their comprehension, in order to be able to direct the future evolution of the landscapes. This requires that transformations be analyzed from mid-term to long-term perspectives, that the consequences of the changes, as well as the opportunities that they generate, are well understood, and finally that relationships be drawn between the biophysical, anthropic, and technological factors responsible for these transformations. This paper concludes with the idea that the creation of landscapes occurs through actions brought about by social demands and by the adjustment of technologies according to the biophysical characteristics of the territories.     

Behavior of class-level landscape metrics across gradients of class aggregation and area

Habitat loss and fragmentation processes strongly affect biodiversity conservation in landscapes undergoing anthropogenic land use changes. Many attempts have been made to use landscape structure metrics to quantify the independent and joint effects of these processes. Unfortunately, ecological interpretation of those metrics has been plagued by lack of thorough understanding of their theoretical behavior. We explored behavior of 50 metrics in neutral landscapes across a 21-step gradient in aggregation and a 19-step gradient in area using a full factorial design with 100 replicates of each of the 399 combinations of the two factors to assess how well metrics reflected changes in landscape structure. Metric values from real landscapes were used to determine the extent of neutral landscape space that is represented in real landscapes. We grouped metrics into three major behavioral classes: strongly related to focal class area (n=15), strongly related to aggregation (n=7), and jointly responding to area and aggregation (n=28). Metrics strongly related to class area exhibited a variety of distinct behaviors, and many of these metrics have unique interpretations that make each of them particularly useful in certain applications. Metrics strongly related to aggregation, independent of class area, are particularly useful in assessing effects of fragmentation. Moreover, metrics in this group exhibited a range of specific behaviors, highlighting subtle but different aspects of landscape aggregation even though we controlled only one aspect of aggregation. The non-linear behavior exhibited by many metrics renders interpretation difficult and use of linear analytical techniques inappropriate under many circumstances. Ultimately, comprehensive characterization of landscapes undergoing habitat loss and fragmentation will require using several metrics distributed across behavioral groups.This revised version was published online in May 2005 with corrections to the Cover Date.     

The development of forage production and utilization gradients around livestock watering points

Large herbivores can impose spatial patterns on otherwise homogeneous vegetation, but how these patterns change through time is poorly understood. Domestic livestock pastures are model systems for studying how foraging behavior influences the development of coupled grazing and vegetation patterns. We sampled forage production and utilization by cattle along distance-from-water gradients to provide a snapshot of grazing and vegetation patterns, and then evaluated the ability of simulation models to qualitatively reproduce these patterns. In the field, forage production increased with distance from water, as expected, but utilization peaked at intermediate distances from water in two of three study areas. Likewise, simulations based on a variety of foraging strategies produced gradients in forage production and, after forage availability near water declined sufficiently, peaks in utilization at intermediate distances. Distance-from-water gradients thus represent cumulative but not necessarily present day gradients in grazing intensity. The model with a foraging strategy based on time minimization produced slightly more realistic patterns in forage abundance than a model based on energy maximization, although results were sensitive to the value of the threshold for rejecting sites of low forage biomass. However, all models produced implausible thresholds in grazing and forage distribution, suggesting that factors besides resource distribution influence herbivore distributions. Moreover, different foraging rules produced similar vegetation gradients, especially on point water source landscapes, illustrating the difficulty of inferring foraging processes from vegetation patterns.     

华北落叶松与阔叶树种混合凋落叶分解过程中养分和细菌群落变化

采用凋落物分解袋法,研究塞罕坝地区华北落叶松（L）、华北落叶松和白桦（LB）、华北落叶松和蒙古栎（LQ）,以及华北落叶松、白桦和蒙古栎（LBQ）的混合凋落叶分解过程中凋落叶养分和细菌群落变化特征。结果表明,在720 d分解过程中,不同混合凋落叶养分变化趋势大致相同,N和P含量呈上升趋势,C和K含量呈下降趋势,pH呈先下降后上升趋势。在分解过程中,混合凋落叶的C和K释放率均高于华北落叶松凋落叶,N和P释放率则相反。华北落叶松凋落叶pH显著低于混合凋落叶。凋落叶分解初期,优势细菌门为变形菌门、蓝细菌门、拟杆菌门和放线菌门;随分解时间延长,变形菌门和蓝细菌门相对丰度逐渐降低,拟杆菌门和放线菌门变化趋势则相反。凋落叶pH和N与细菌多样性指数呈极显著相关。凋落物分解过程中,细菌多样性指数和丰富度呈上升趋势。分解600 d后,华北落叶松凋落叶细菌丰富度低于混合凋落叶。华北落叶松、白桦和蒙古栎凋落叶混合,能够提高部分养分释放率,提高细菌群落多样性。