Landscape Gradient Research Articles

An analysis on separability for Memetic Computing automatic design

This paper proposes a computational prototype for automatic design of optimization algorithms. The proposed scheme makes an analysis of the problem that estimates the degree of separability of the optimization problem. The separability is estimated by computing the Pearson correlation indices between pairs of variables. These indices are then manipulated to generate a unique index that estimates the separability of the entire problem. The separability analysis is thus used to design the optimization algorithm that addresses the needs of the problem. This prototype makes use of two operators arranged in a Parallel Memetic Structure. The first operator performs moves along the axes while the second simultaneously perturbs all the variables to follow the gradient of the fitness landscape. The resulting algorithmic implementation, namely Separability Prototype for Automatic Memes (SPAM), has been tested on multiple testbeds and various dimensionality levels. The proposed computational prototype proved to be a flexible and intelligent framework capable to learn from a problem and, thanks to this learning, to outperform modern meta-heuristics representing the-state-of-the-art in optimization.

Habitat filtering by landscape and local forest composition in native and exotic New Zealand birds

Untangling the relative influences of environmental filtering and biotic interactions on species coexistence at various spatial scales is a long-held issue in community ecology. Separating these processes is especially important to understand the influences of introduced exotic species on the composition of native communities. For this aim, we investigated coexistence patterns in New Zealand exotic and native birds along multiple-scale habitat gradients. We built a Bayesian hierarchical model, contrasting the abundance variations of 10 native and 11 exotic species in 501 point counts spread along landscape and local-scale gradients of forest structure and composition. Although native and exotic species both occurred in a wide range of habitats, they were separated by landscape-level variables. Exotic species were most abundant in exotic conifer plantations embedded in farmland matrices, while native birds predominated in areas dominated by continuous native forest. In exotic plantation forests, and to a lesser extent in native forests, locally co-occurring exotic and native species were segregated along a gradient of vegetation height. These results support the prediction that exotic and native bird species are segregated along gradients related to anthropogenic disturbance and habitat availability. In addition, native and exotic species overlapped little in a multivariate functional space based on 10 life history traits associated with habitat selection. Hence, habitat segregation patterns were probably mediated more by environmental filtering processes than by competition at landscape and local scales.

基于移动窗口法的岷江干旱河谷景观格局梯度分析

PDF HTML阅读 XML下载 导出引用 引用提醒 基于移动窗口法的岷江干旱河谷景观格局梯度分析 DOI: 10.5846/stxb201310312639 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目资助（31000222，31170664） Gradient analysis of dry valley of Minjiang River landscape pattern, based on moving window method Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以岷江干旱河谷为研究区，基于GIS技术和移动窗口法对其景观格局梯度变化进行分析，以期为区域的景观格局优化和管理提供支持。根据研究区的形状特征，分别沿干流和支流设置4条样带；选取景观水平下的景观指数，利用FRAGSTATS3.3软件分别采取标准法和移动窗口法获得不同尺度下的景观指数值；综合利用景观指数粒度效应分析、区域面积信息守恒评价方法和景观指数幅度效应评价曲线确定研究区景观格局梯度分析移动窗口尺寸，并计算了此窗口尺度下4条样带上的景观指数，得到沿样带方向的景观梯度格局。结果表明：岷江干旱河谷的景观基质是灌木林地，面积占73.82%。有林地和草地的景观异质性低，居民地和耕地斑块破碎化程度较大。确定了50m的栅格大小，250m的移动窗口尺寸为研究区景观格局梯度分析的窗口尺度；4条样带上各景观指数均随景观类型变化出现不同幅度的上下波动特征，梯度特征明显。处于景观类型过渡地带的区域，景观多样性和异质性增加，破碎化程度高；干旱河谷景观格局梯度变化主要受地形、水热因子，以及堤坝建设和土地开发利用影响。研究作为一种有益的尝试，更精细地分析了研究区的景观格局，能够为河谷地区景观格局量化分析提供参考，但也存在一定不足，需要在今后工作中继续深入研究。 Abstract:Great attentions have been paid on landscape changes in recent years. As a basis of further researches on landscape functions and dynamics, contributes to analyzing spatial distribution characteristics of landscape components, landscape pattern analysis became an important topic of landscape ecology. In landscape pattern analysis, landscape metrics has been used as a common tool to exhibit the spatial distribution of landscape. During the past two decades, many processes have been used to analyze changes of landscape and the relationships with human influences and environmental factors. As a hotspot of quantitative methods of landscape analysis, gradient analysis, which is conducive to revealing the evolutionary laws of spatial landscape patterns has became a significant means in landscape ecology. However, the appropriate spatial scale is the key point to calculate the landscape metrics, and scale issues represent one of the foremost frontiers of landscape ecology. It is well known that the observed landscape pattern and its relationship with (landscape) process depend upon the scale. Great developments have been made on researches on pixel and spatial extent of landscape pattern evolution quantitatively and qualitatively. Little on the accuracy of the landscape analysis is related to both pixel and extent effect since there is the lackage of systematic study on the selection of optimization scale in landscape gradient pattern analysis. In this study, taking the dry valley of Minjiang River as study area and using ARCGIS9.3, ENVI4.8 and FRAGSTATS3.3, based on the image data of Land Resources Satellite ETM+ (2011), we aim to analyze the variation of landscape index with grain size. To obtain gradient patterns of the landscapes, 4 transects have been set up along both mainstream and tributaries of Minjiang River. A series of metrics at the landscape level (NP, PD, LPI, DIVISION, SHDI, and SHEI) were chosen and calculated using standard and moving window approach with different spatial scale, respectively. Then, an optimization-scale selection method, which integrates: the grain effect analysis of landscape index, the data loss assessment and the landscape index range effect curve analysis, was developed to obtain accuracy and efficient scale. By analyzing the grain inflexions of the landscape index comprehensively, we found that 30-90m and 110-160m were the appropriate grain ranges. Data loss assessment showed that 50m was the appropriate grain extent. In addition, based on moving window analysis, landscape index range effect curve analysis suggested that 250m was the most appropriate spatial extent for landscape pattern analysis. At the landscape level, 6 metrics were calculated by Moving window method: shrub land, accounting for 73.82% of the total landscape, was the matrix in dry valley of Minjiang River in the year 2011; the forestland and grassland's landscape heterogeneity decreased and relatively high the fragmentation degree of construct and farmland; water area has no obvious change; landscape metrics in the four transects present different amplitude and evident gradient diversity as landscape type change, the index change is larger in transition zone as compared to the single region; landscape pattern develops in the direction of heterogeneity, diversification and homogenization; and topography, precipitation, temperature and human activities were the factors for the gradient changes of landscape. As a kind of beneficial attempt, this study more finely analyzed the landscape pattern in the study area. The result of landscape pattern gradient analysis provided a novel way for discerning the landscape pattern change in the mountainous areas. 参考文献 相似文献 引证文献

Forecasting conditional climate-change using a hybrid approach

A novel approach is proposed to forecast the likelihood of climate-change across spatial landscape gradients. This hybrid approach involves reconstructing past precipitation and temperature using the self-organizing map technique; determining quantile trends in the climate-change variables by quantile regression modeling; and computing conditional forecasts of climate-change variables based on self-similarity in quantile trends using the fractionally differenced auto-regressive integrated moving average technique. The proposed modeling approach is applied to states (Arizona, California, Colorado, Nevada, New Mexico, and Utah) in the southwestern U.S., where conditional forecasts of climate-change variables are evaluated against recent (2012) observations, evaluated at a future time period (2030), and evaluated as future trends (2009–2059). These results have broad economic, political, and social implications because they quantify uncertainty in climate-change forecasts affecting various sectors of society. Another benefit of the proposed hybrid approach is that it can be extended to any spatiotemporal scale providing self-similarity exists.

Climate sensitivity of reproduction in a mast-seeding boreal conifer across its distributional range from lowland to treeline forests

Mast-seeding conifers such as Picea glauca exhibit synchronous production of large seed crops over wide areas, suggesting climate factors as possible triggers for episodic high seed production. Rapidly changing climatic conditions may thus alter the tempo and spatial pattern of masting of dominant species with potentially far-reaching ecological consequences. Understanding the future reproductive dynamics of ecosystems including boreal forests, which may be dominated by mast-seeding species, requires identifying the specific cues that drive variation in reproductive output across landscape gradients and among years. Here we used annual data collected at three sites spanning an elevation gradient in interior Alaska, USA between 1986 and 2011 to produce the first quantitative models for climate controls over both seedfall and seed viability in P. glauca, a dominant boreal conifer. We identified positive associations between seedfall and increased summer precipitation and decreased summer warmth in all years except for the year prior to seedfall. Seed viability showed a contrasting response, with positive correlations to summer warmth in all years analyzed except for one, and an especially positive response to warm and wet conditions in the seedfall year. Finally, we found substantial reductions in reproductive potential of P. glauca at high elevation due to significantly reduced seed viability there. Our results indicate that major variation in the reproductive potential of this species may occur in different landscape positions in response to warming, with decreasing reproductive success in areas prone to drought stress contrasted with increasing success in higher elevation areas currently limited by cool summer temperatures.

The Duxbury Sunken Forest—Constraints for Local, Late Holocene Environmental Changes Resulting from Marine Transgression, Duxbury Bay, Eastern Massachusetts, U.S.A.

Gontz, A.M.; Maio, C.V., and Rueda, L., 2013. The Duxbury sunken forest—constraints for local, late Holocene environmental changes resulting from marine transgression, Duxbury Bay, Eastern Massachusetts, U.S.A.The present marine transgression has forced geological and ecological zones vertically higher and landward since the late Pleistocene. A recent investigation in Duxbury Bay, Massachusetts, identified 18 Juniperus virginiana tree stumps emergent on an intertidal flat immediately seaward of a small marsh and pond situated between two eroding drumlins. The position of each stump was mapped with global positioning system (GPS), and its elevation with respect to mean lower low water was surveyed. Samples were selected from four stumps with elevations ranging from 2.03 and 0.75 m above mean lower low water for radiocarbon dating. The samples returned calibrated ages between 2219 ± 94 and 2867 ± 79 cal YBP, with the topographically highest sample returning the youngest date. Stump positions suggest a landscape gradient of 1.4 mm/yr between 2000 and 3000 cal YBP. The results are comparable with high-resolution studies of sea level in eastern Massachusetts for the same time period. Comparison of the youngest paleostumps with modern living trees suggests a dramatic change in the landscape gradient, an increase to 1.8 mm/yr. While this is contrary to sea-level studies nearby, it may represent an increase in the energetics of Duxbury Bay and resultant coastal erosion as the bay floods. The site can be used to put the impacts of changing sea-level rates into a landscape evolution framework.

Nonequilibrium landscape theory of neural networks

The brain map project aims to map out the neuron connections of the human brain. Even with all of the wirings mapped out, the global and physical understandings of the function and behavior are still challenging. Hopfield quantified the learning and memory process of symmetrically connected neural networks globally through equilibrium energy. The energy basins of attractions represent memories, and the memory retrieval dynamics is determined by the energy gradient. However, the realistic neural networks are asymmetrically connected, and oscillations cannot emerge from symmetric neural networks. Here, we developed a nonequilibrium landscape-flux theory for realistic asymmetrically connected neural networks. We uncovered the underlying potential landscape and the associated Lyapunov function for quantifying the global stability and function. We found the dynamics and oscillations in human brains responsible for cognitive processes and physiological rhythm regulations are determined not only by the landscape gradient but also by the flux. We found that the flux is closely related to the degrees of the asymmetric connections in neural networks and is the origin of the neural oscillations. The neural oscillation landscape shows a closed-ring attractor topology. The landscape gradient attracts the network down to the ring. The flux is responsible for coherent oscillations on the ring. We suggest the flux may provide the driving force for associations among memories. We applied our theory to rapid-eye movement sleep cycle. We identified the key regulation factors for function through global sensitivity analysis of landscape topography against wirings, which are in good agreements with experiments.

Bats and birds increase crop yield in tropical agroforestry landscapes

Human welfare is significantly linked to ecosystem services such as the suppression of pest insects by birds and bats. However, effects of biocontrol services on tropical cash crop yield are still largely unknown. For the first time, we manipulated the access of birds and bats in an exclosure experiment (day, night and full exclosures compared to open controls in Indonesian cacao agroforestry) and quantified the arthropod communities, the fruit development and the final yield over a long time period (15months). We found that bat and bird exclusion increased insect herbivore abundance, despite the concurrent release of mesopredators such as ants and spiders, and negatively affected fruit development, with final crop yield decreasing by 31% across local (shade cover) and landscape (distance to primary forest) gradients. Our results highlight the tremendous economic impact of common insectivorous birds and bats, which need to become an essential part of sustainable landscape management.

A riverscape transect approach to studying and restoring river systems: A case study from southern China

Rivers provide critically important ecosystem services to society, and play an essential role in maintaining the structure, function, and integrity of landscapes in which the rivers reside. Better understanding of the patterns and processes in river systems requires a broader landscape approach that goes beyond the traditional linear and longitudinal focus. Such a landscape approach is especially important for effectively restoring and managing already damaged or degraded rivers around the world. Toward this end, here we develop a riverscape transect approach by adapting landscape gradient analysis with pattern metrics so as to quantify the longitudinal variations in the spatial pattern of the river-land complex from headwater to mouth. Two rivers systems in southern China were used to develop and demonstrate the approach. For each river, we first constructed a riverscape transect, consisting of a spatial series of overlapping neighborhood landscapes, then computed a selected set of landscape metrics, and finally depicted the longitudinal profile of riverscape pattern with relative location-based plots. Our results have shown that this riverscape transect approach is conceptually consistent with the increasingly prominent riverine landscape perspective and technically feasible with the aid of remote sensing data and landscape pattern analysis methods. In particular, landscape metrics, such as percentages of urban and native vegetation, patch density, and Shannon diversity, can be used to reveal important variations in riverscape structure along the river. These longitudinal profiles of riverscape pattern, used as spatial indicators, can help identify key socioeconomic drivers and ecological impacts of land use and land cover change in the watershed. Our study demonstrates that this riverscape transect approach can be a new and effective way of facilitating the planning and evaluation of river restoration and management efforts.

Climate and exotic pasture area in landscape determines invasion of forest fragments by two invasive grasses

To date, there has been a focus on biological aspects of invasion rather than landscape-scale processes within human-modified landscapes. Applying a multi-scale approach may improve predictive models of invasion in fragmented landscapes as well as management. We tested a priori models of the relative importance of landscape (10 000 to 30 000 ha), site-scale (<0·3 ha) factors and climate gradients, and their interactions, on the cover of exotic grasses in forest fragments. We tested the models for two exotic pasture grasses Cenchrus ciliaris and Panicum maximum in fragmented agricultural landscapes of subtropical eastern Australia. Mixed-effect models were applied to quantify the multi-scale effects of land use, forest area and fragmentation, vegetation structure, soil and climate attributes and their interactions on the ground cover of the two exotic grasses. We used model averaging to account for model and parameter uncertainty and tested for spatial autocorrelation and the model fit in model residuals. There was strong evidence that the area of exotic pasture grass in the landscape and climate gradients had a strong influence on cover observed at the site scale, but the climate influence was species specific. Cenchrus ciliaris cover was higher in forest sites within landscapes converted to exotic pastures and with high mean minimum temperatures and sites with low canopy cover. In contrast, P. maximum cover was primarily influenced by high mean annual rainfall, with moderate positive effects from area of exotic pasture in the landscape and high minimum temperatures. Synthesis and applications. This study highlights several key issues that need to be considered when prioritizing management of invasive species in fragmented landscapes. First, the propagule supply in the landscape and climate gradients are key factors influencing the spread of exotic grasses into forest fragments. Second, managing canopy cover is critical to enhancing C. ciliaris invasion resistance, but not for P. maximum. We conclude that a multi-scale approach provides the conceptual and applied basis for an improved understanding and management of plant invasions in fragmented landscapes.

Urban-rural gradient detection using multivariate spatial analysis and landscape metrics

The gradient approach allows for an innovative representation of landscape composition and configuration not presupposing spatial discontinuities typical of the conventional methods of analysis. Also the urban-rural dichotomy can be better understood through a continuous landscape gradient whose characterization changes accordingly to natural and anthropic variables taken into account and to the spatio-temporal scale adopted for the study. The research was aimed at the analysis of an urban-rural gradient within a study area located in central Italy, using spatial indicators associated with urbanization, agriculture and natural elements. A multivariate spatial analysis (MSA) of such indicators enabled the identification of urban, agricultural and natural dominated areas, as well as specific landscape transitions where the most relevant relationships between agriculture and other landscape components were detected. Landscapes derived from MSA were studied by a set of key landscape pattern metrics within a framework oriented to the structural characterization of the whole urban-rural gradient. The results showed two distinct sub-gradients: one urban-agricultural and one agricultural-natural, both characterized by different fringe areas. This application highlighted how the proposed methodology can represent a reliable approach supporting modern landscape planning and management.

A spatially predictive baseline for monitoring multivariate species occurrences and phylogenetic shifts in mediterranean southern Australia

AbstractQuestionClimate change is driving shifts in the composition of vegetation but the lack of controls and confounding spatial factors pose challenges for detecting the climate signal in observed changes through time and space. We tested whether climate can be isolated as a driver of spatial vegetation composition at the landscape scale in mediterranean southern Australia by considering landscape factors (e.g. soil gradients) and spatial structure (relative geographic isolation). The aim was to develop principles for selecting spatial analogues for climate change and provide a spatially predictive baseline for monitoring.MethodsA landscape‐scale monitoring transect spanning 550 km was established. Whole community presence/absence of vascular plant species in plots was modelled as a multivariate response to environmental and spatial variables. Species and phylogenetic composition–environment relationships were also explored using indirect gradient approaches, partial correlations and distance decay models.ResultsA total of &gt;2900 occurrences of &gt;400 plant species were recorded. Relative vegetation composition was predicted by mean temperature and soil properties, such as electrical conductivity and texture. Spatial structure was critical, as decay in compositional similarity with geographic distance and spatial autocorrelation of nested plots were involved in turnover patterns. The rate of change in species composition with changes in temperature equated to complete species turnover within the habitats sampled.ConclusionsThe influence of climate on spatial variation in vegetation composition can be quantified, accounting for distance decay. Landscape gradients (particularly soil properties) tended to be orthogonal to climate and explained some turnover. Spatial analogues for climate change would need to be similar in soil properties and not too geographically distant. Composition resulting from more extreme climate change scenarios may have no spatial analogue due to the importance of neutral distance decay at larger spatial scales in determining compositional differences. We illustrate these principles with a sequence of warming, drying analogues. The spatial transect provides a framework for monitoring composition by directly incorporating temporal data and using spatial analysis to inform the expected direction of compositional shifts with climate change.

Eddy current and coupled landscapes for nonadiabatic and nonequilibrium complex system dynamics

Physical and biological systems are often involved with coupled processes of different time scales. In the system with electronic and atomic motions, for example, the interplay between the atomic motion along the same energy landscape and the electronic hopping between different landscapes is critical: the system behavior largely depends on whether the intralandscape motion is slower (adiabatic) or faster (nonadiabatic) than the interlandscape hopping. For general nonequilibrium dynamics where Hamiltonian or energy function is unknown a priori, the challenge is how to extend the concepts of the intra- and interlandscape dynamics. In this paper we establish a theoretical framework for describing global nonequilibrium and nonadiabatic complex system dynamics by transforming the coupled landscapes into a single landscape but with additional dimensions. On this single landscape, dynamics is driven by gradient of the potential landscape, which is closely related to the steady-state probability distribution of the enlarged dimensions, and the probability flux, which has a curl nature. Through an example of a self-regulating gene circuit, we show that the curl flux has dramatic effects on gene regulatory dynamics. The curl flux and landscape framework developed here are easy to visualize and can be used to guide further investigation of physical and biological nonequilibrium systems.

The idiosyncrasies of place: geographic variation in the climate–distribution relationships of the American pika

Although climate acts as a fundamental constraint on the distribution of organisms, understanding how this relationship between climate and distribution varies over a species' range is critical for addressing the potential impacts of accelerated climate change on biodiversity. Bioclimatic niche models provide compelling evidence that many species will experience range shifts under scenarios of global change, yet these broad, macroecological perspectives lack specificity at local scales, where unique combinations of environment, biota, and history conspire against generalizations. We explored how these idiosyncrasies of place affect the climate-distribution relationship of the American pika (Ochotona princeps) by replicating intensive field surveys across bioclimatic gradients in eight U.S. national parks. At macroecological scales, the importance of climate as a constraint on pika distribution appears unequivocal; forecasts suggest that the species' range will contract sharply in coming decades. However, the species persists outside of its modeled bioclimatic envelope in many locations, fueling uncertainty and debate over its conservation status. Using a Bayesian hierarchical approach, we modeled variation in local patterns of pika distribution along topographic position, vegetation cover, elevation, temperature, and precipitation gradients in each park landscape. We also accounted for annual turnover in site occupancy probabilities. Topographic position and vegetation cover influenced occurrence in all parks. After accounting for these factors, pika occurrence varied widely among parks along bioclimatic gradients. Precipitation by itself was not a particularly influential predictor. However, measures of heat stress appeared most influential in the driest parks, suggesting an interaction between the strength of climate effects and the position of parks along precipitation gradients. The combination of high elevation, cold temperatures, and high precipitation lowered occurrence probabilities in some parks, suggesting an upper elevational limit for pikas in some environments. Our results demonstrate that the idiosyncrasies of place influence both the nature and strength of the climate-distribution relationship for the American pika. Fine-grained, but geographically extensive, studies replicated across multiple landscapes offer insights important to assessing the impacts of climate change that otherwise may be masked at macroecological scales. The hierarchical approach to modeling provides a coherent conceptual and technical framework for gaining these insights.

Guild structure in the food web of grassland arthropod communities along an urban—rural landscape gradient

Urbanization is a major cause of ecosystem change, and arthropods are a principal component of grassland ecosystems, which are often found in human-dominated landscapes. Although higher trophic level arthropods have been expected to be the most sensitive to urbanization, researchers are debating whether this is the case. We compared the guild structure of grassland arthropod food webs along an urban—rural gradient in the Tokyo metropolitan area, the largest metropolitan area in the world. Arthropod communities were sampled, and guild types were classified by body size and food habit. The guild structure of arthropod food webs was compared among various types of grasslands, and the effects on the guild structure of the surrounding landscape and local vegetation were analyzed. The arthropod guild structure varied along the urban—rural gradient. Large carnivores were abundant in semi—natural grassland ecosystems in the traditional rural landscape, which was at one end of the studied urban-rural gradient. In contrast, small carnivores, omnivores, and detritivores were abundant in the artificial grassland ecosystems of the urban landscape at the other end of the gradient. Because very large carnivores are vulnerable to urbanization activities, rural landscapes rich in these species should be conserved.

Distribution of Wild Mammal Assemblages along an Urban–Rural–Forest Landscape Gradient in Warm-Temperate East Asia

Urbanization may alter mammal assemblages via habitat loss, food subsidies, and other factors related to human activities. The general distribution patterns of wild mammal assemblages along urban–rural–forest landscape gradients have not been studied, although many studies have focused on a single species or taxon, such as rodents. We quantitatively evaluated the effects of the urban–rural–forest gradient and spatial scale on the distributions of large and mid-sized mammals in the world's largest metropolitan area in warm-temperate Asia using nonspecific camera-trapping along two linear transects spanning from the urban zone in the Tokyo metropolitan area to surrounding rural and forest landscapes. Many large and mid-sized species generally decreased from forest landscapes to urban cores, although some species preferred anthropogenic landscapes. Sika deer (Cervus nippon), Reeves' muntjac (Muntiacus reevesi), Japanese macaque (Macaca fuscata), Japanese squirrel (Sciurus lis), Japanese marten (Martes melampus), Japanese badger (Meles anakuma), and wild boar (Sus scrofa) generally dominated the mammal assemblage of the forest landscape. Raccoon (Procyon lotor), raccoon dog (Nyctereutes procyonoides), and Japanese hare (Lepus brachyurus) dominated the mammal assemblage in the intermediate zone (i.e., rural and suburban landscape). Cats (feral and free-roaming housecats; Felis catus) were common in the urban assemblage. The key spatial scales for forest species were more than 4000-m radius, indicating that conservation and management plans for these mammal assemblages should be considered on large spatial scales. However, small green spaces will also be important for mammal conservation in the urban landscape, because an indigenous omnivore (raccoon dog) had a smaller key spatial scale (500-m radius) than those of forest mammals. Urbanization was generally the most important factor in the distributions of mammals, and it is necessary to consider the spatial scale of management according to the degree of urbanization.

Effects of volcanic and hydrologic processes on forest vegetation: Chaitén Volcano, Chile

The 2008-2009 eruption of Chaiten Volcano (Chile) involved a variety of volcanic and associated hydro- logic processes that damaged nearby forests. These processes included coarse (gravel) and fine (silt to sand) tephra fall, a laterally directed blast, fluvial deposition of remobilized tephra, a variety of low-temperature mass-movement processes, and a pyroclastic flow. Each of these geophysical processes constitutes a type of ecosystem disturbance which involves a distinctive suite of disturbance mechanisms, namely burial by tephra and sediment, heating, abrasion, impact force, and canopy loading (accumulation of tephra in tree crowns). Each process affected specific areas, and created patches and disturbance gradients in the forest landscape. Coarse tephra ('gravel rain', >5 cm depth) abraded foliage from tree canopies over an area of approximately 50 km 2 north-northeast of the vent. Fine tephra (>10 cm depth) accumulated in tree crowns and led to breakage of branches in old forest and bowing of flexible, young trees over an area of about 480 km 2 . A directed blast down the north flank of the volcano damaged forest over an area of 4 km 2 . This blast zone included an area of tree removal near the crater rim, toppled forest farther down the slope, and standing, scorched forest around the blast perimeter. Fluvial deposition of >100 cm of remobilized tephra, beginning about 10 days after initiation of the erup- tion, buried floodplain forest in distinct, elongate streamside patches covering 5 km 2 of the lower 19 km of the Rayas River and several km 2 of the lower Chaiten River. Across this array of disturbance processes the fate of affected trees varied from complete mortality in the tree removal and pyroclastic flow areas, to no mortality in areas of thin tephra fall deposits. Tree damage included defoliation, loss of branches, snapping of tree trunks, abrasion of bark and ephiphytes, and uprooting. Damaged trees sprouted from epicormic buds located in trunks and branches, but sprouting varied over time among disturbance mechanisms and species. Although some effects of the Chaiten eruption are very similar to those from the 1980 eruption of Mount St. Helens (USA), interactions between biota and geophysical processes at Chaiten produced some unique effects. Examination of vegetation response helps interpret geophysical processes, and disturbance mechanisms influence early stages of biotic response to an eruption.

Improved Fluorescence Excitation‐Emission Matrix Regional Integration to Quantify Spectra for Fluorescent Dissolved Organic Matter

The purpose of this short communication is to demonstrate the importance of numerical analysis and wavelength increment selection when characterizing fluorescent dissolved organic matter (FDOM) using fluorescence excitation-emission matrix (EEM) regional integration. A variety of water samples, representing a landscape gradient and different types of FDOM, were analyzed for their percentage distribution of five operationally defined FDOM fractions (aromatic protein I, aromatic protein II, fulvic acid-like, soluble microbial byproduct-like, and humic acid-like) using three numerical methods in integrating volume under the surface of the fluorescence EEMs: Riemann summation, composite trapezoidal rule, and composite Simpson's rule. The influence of wavelength increment was also examined for the precision of the percentage distribution of each fraction. Our results show that the FDOM fraction estimated by Riemann summation with a 10- or 5-nm excitation wavelength can cause >40% or >5% errors, respectively, when compared with the best estimated values obtained by averaging results from composite trapezoidal rule and composite Simpson's rule with 1-nm excitation wavelength at the same emission increment. Also, our experiments show that fluorescence matrix regional integration could underestimate the two aromatic protein fractions but could overestimate the soluble microbial byproduct-like and humic acid-like fractions if improper increment and integral methods are used. The error can be reduced if a smaller wavelength increment is used. The smallest increment in a spectrofluorometer and composite Simpson's rule should be used for scanning fluorescence EEMs and calculating the percentage distribution of each FDOM fraction. Alternatively, 5-nm wavelength increments with composite Simpson's rule could be cost effective, and the error of each FDOM fraction commonly falls within 5% compared with those estimated by 1-nm increments.

Habitat connectivity for pollinator beetles using surface metrics

Measuring habitat connectivity in com- plex landscapes is a major focus of landscape ecology and conservation research. Most studies use a binary landscape or patch mosaic model for describing spatial heterogeneity and understanding pattern-process rela- tionships. While the value of landscape gradient approaches proposed by McGarigal and Cushman are recognized, applications of these newly proposed three dimensional surface metrics remain under-used. We created a gradient map of habitat quality from several GIS layers and applied three dimensional surface metrics to measure connectivity between 67 locations in Indiana, USA surveyed for one group of ecosystem service providers, flower longicorn beetles (Cerambycidae: Lepturinae). The three dimensional surface metrics applied to the landscape gradient model showed great potential to explain the differ- ences of lepturine assemblages among the 2,211 studied landscapes (between site pairs). Surface kurtosis and its interaction with geographic distance were among the most important metrics. This approach provided unique information about the landscape through four configuration metrics. There were some uniform trends of the responses of many species to some of surface metrics, however some species responded differently to other metrics. We suggest that three dimensional surface metrics applied to a habitat surface map created with insight into species requirements is a valuable approach to under- standing the spatial dynamics of species, guilds, and ecosystem services.

Optimal reconstruction of the folding landscape using differential energy surface analysis

In experiments and in simulations, the free energy of a state of a system can be determined from the probability that the state is occupied. However, it is often necessary to impose a biasing potential on the system so that high energy states are sampled with sufficient frequency. The unbiased energy is typically obtained from the data using the weighted histogram analysis method (WHAM). Here we present differential energy surface analysis (DESA), in which the gradient of the energy surface, dE/dx, is extracted from data taken with a series of harmonic biasing potentials. It is shown that DESA produces a maximum likelihood estimate of the folding landscape gradient. DESA is demonstrated by analyzing data from a simulated system as well as data from a single-molecule unfolding experiment in which the end-to-end distance of a DNA hairpin is measured. It is shown that the energy surface obtained from DESA is indistinguishable from the energy surface obtained when WHAM is applied to the same data. Two criteria are defined which indicate whether the DESA results are self-consistent. It is found that these criteria can detect a situation where the energy is not a single-valued function of the measured reaction coordinate. The criteria were found to be satisfied for the experimental data analyzed, confirming that end-to-end distance is a good reaction coordinate for the experimental system. The combination of DESA and the optical trap assay in which a structure is disrupted under harmonic constraint facilitates an extremely accurate measurement of the folding energy surface.