Patch Proximity Research Articles

Arthropod removal in wheat fields enhanced yield regardless of natural habitat patch proximity

Natural habitat patches can be essential in conserving biodiversity and providing ecosystem services for agroecological systems. However, adopting a land-sharing approach requires a deep understanding of the agricultural costs and benefits associated with the existence of adjacent natural habitat patches. We used 17 paired natural habitat patch-wheat field replicates to test the effects of distance from the natural patches and removal of ground-dwelling arthropods from the field on the wheat yield. Removing ground-dwelling arthropods increased wheat yield. Community compositions of ground-dwelling arthropods in the natural habitat patches and wheat fields varied significantly, irrespective of the distance from the natural patch. In April and May, near the wheat harvest, predator abundance was higher in the natural habitat patches than in the wheat fields, whereas the abundance of potential pests was much higher in the wheat fields. This reduced predator-pest ratio in the wheat fields may explain why removing ground-dwelling arthropods increased wheat yield. Future research should focus on developing effective methods for managing ground-dwelling and vertical wheat pest populations while preserving their natural enemies' integrity within the fields and adjacent natural habitat patches.

Predator avoidance and food patch proximity influence sleeping site use of Assamese macaques in a limestone forest of Southwest Guangxi, China

AbstractObjectivesWe investigated the sleeping site use of one group of Assamese macaques in Southwest Guangxi, China. We examined their behavioral adaptation to limestone forests by evaluating hypotheses of predator avoidance, food proximity, and range or resource defense.Materials and MethodsWe recorded the locations of sleeping sites on a topographic map using a grid cell method and mapped the use of foraging patches within the home range.ResultsAssamese macaques used 19 different sleeping sites, mainly located on cliffs. They rapidly entered sleeping sites and then remained silent. They preferred three sites but never used them for more than four consecutive nights. Sleeping site use was positively correlated with the number of surrounding foraging patches, but the distances between sleeping sites and the last/first feeding areas (84.16 ± 41.26 and 94.88 ± 45.83 m, respectively) were not affected by seasonal fluctuations in fruit availability; these distances were longer than those predicted under a multiple central place foraging (MCPF) strategy but shorter than those predicted under a central place foraging (CPF) strategy. The observed distances between the sleeping sites and the first feeding areas in the rainy season were similar to the predicted distances of an MCPF strategy. The macaques slept in peripheral parts of their home range as expected, and there were no conflicts with neighboring groups.DiscussionSleeping site use was strongly affected by predator avoidance and proximity to food resources, but not by resource defense. The vertical distribution of sleeping sites on hills was not influenced by fruit availability. The macaques are closer to using an MCPF strategy to maximize food harvest efficiency, particularly in the rainy season. Assamese macaques' sleeping site use in limestone forests supports the hypotheses of predator avoidance and food proximity.

Fragment shape and size, landscape permeability and fragmentation level as predictors of primate occupancy in a region of Brazilian Cerrado

Human activities result in the formation of a mosaic of forest patches within a non-habitat matrix. The response of the local biodiversity to changes in land-use may occur at different scales. It is important to evaluate the effects of the attributes of both the patches and the surrounding landscape on the occupancy of forest patches by animal populations. Here, we assessed the predictive potential of local (basal area, tree density), patch (size, shape) and landscape scale (total area of forest, number of patches, matrix permeability, patch proximity) variables on the occupancy of forest patches by the syntopic primates Alouatta caraya, Sapajus libidinosus and Callithrix penicillata in the city of Goiânia in the Cerrado region of central Brazil. We used playback to survey primate populations in 22 focal patches and assessed the landscape within a 1000 m buffer zone around each site. In A. caraya, occupancy was influenced by the shape of the focal patches, the amount of forest and fragmentation level of the landscape. Focal patch size and the permeability of the matrix were the principal determinants of the occupancy of S. libidinosus. None of the predictors influenced patch occupancy in C. penicillata, and the structure of the vegetation did not influence occupancy in any of the species. The preservation of as many forest patches as possible, both large and small, as well as gallery forests, and the enhancement of matrix permeability will be essential for the long-term conservation of the syntopic primates of the Cerrado of central Brazil.

Health of Vegetation in the Area of Mass Outbreaks of Siberian Moth Based on Satellite Data

This paper presents the results of analyzing the state and dynamics of damaged vegetation from satellite images of high and ultrahigh spatial resolution. This study was conducted based on the example of the site of coniferous forests in the Lower Angara region (Krasnoyarsk krai), where a large outbreak of the Siberian moth took place in 1944–1995. The remote assessment of the state of dark coniferous forests revealed the trends of the SWVI (or NDMI) and NDVI indices that characterize long-term changes in the vegetation cover over the period 2000–2018. The SWVI index is the most informative indicator: a sharp decrease in average values and increase in the coefficient of variation of the index are noted for dead and severely damaged wood stands (crown defoliation of more than 75%). The area of dead forests was calculated according to the difference images of the indices (ΔSWVI) with the threshold criterion lσ (the standard deviation). In 2000, the area of forests that died under the impact of the Siberian moth was approximately 19 200 ha. Alter two major fires in 2004 and 2011 and as a result of destructive factors combination, the area of dead forests increased up to 20 400 ha by 2017–2018. Reforestation within the boundaries of dead stands was estimated from the classification of Landsat images (June 20, 2017; June 23, 2018) by the Random Forest algorithm using the selection of templates from detailed Resurs-P images with a spatial resolution of 1 m (Geoton-LI—July 22, 2015 and December 3, 2018), which were taken during different seasons. The classification proved to be highly reliable (Kappa index is more than 0.9). The areas of classified deciduous and coniferous stands, deciduous and mixed stands with mainly coniferous regrowth, grass–shrub vegetation, and barren soil were calculated. Natural regeneration of mainly coniferous undergrowth occurred in 17% of the damaged area, and deciduous regrowth occurred in approximately 10% of the area 23 years after damage by pests. The area damaged by the moth affected reforestation: the larger the area of the outbreak, the higher the share of open lands with grass and shrub vegetation (it accounts for more than half of the area for the large outbreak and approximately 45% for smaller outbreaks). Regrowth was found in proximity of patches of stands and deadwood in the sites unaffected by large fires. Frequent fires in the territory of moth infestation limit the process of reforestation; therefore, most of the vegetation was at the initial stage of the succession cycle.

Contributions of fire refugia to resilient ponderosa pine and dry mixed‐conifer forest landscapes

AbstractAltered fire regimes can drive major and enduring compositional shifts or losses of forest ecosystems. In western North America, ponderosa pine and dry mixed‐conifer forest types appear increasingly vulnerable to uncharacteristically extensive, high‐severity wildfire. However, unburned or only lightly impacted forest stands that persist within burn mosaics—termed fire refugia—may serve as tree seed sources and promote landscape recovery. We sampled tree regeneration along gradients of fire refugia proximity and density at 686 sites within the perimeters of 12 large wildfires that occurred between 2000 and 2005 in the interior western United States. We used generalized linear mixed‐effects models to elucidate statistical relationships between tree regeneration and refugia pattern, including a new metric that incorporates patch proximity and proportional abundance. These relationships were then used to develop a spatially explicit landscape simulation model. We found that regeneration by ponderosa pine and obligate‐seeding mixed‐conifer tree species assemblages was strongly and positively predicted by refugia proximity and density. Simulation models revealed that for any given proportion of the landscape occupied by refugia, small patches produced greater landscape recovery than large patches. These results highlight the disproportionate importance of small, isolated islands of surviving trees, which may not be detectable with coarse‐scale satellite imagery. Findings also illustrate the interplay between patch‐scale resistance and landscape‐scale resilience: Disturbance‐resistant settings (fire refugia) can entrain resilience (forest regeneration) across the burn matrix. Implications and applications for land managers and conservation practitioners include strategies for the promotion and maintenance of fire refugia as components of resilient forest landscapes.

Circuit-theory applications to connectivity science and conservation.

Conservation practitioners have long recognized ecological connectivity as a global priority for preserving biodiversity and ecosystem function. In the early years of conservation science, ecologists extended principles of island biogeography to assess connectivity based on source patch proximity and other metrics derived from binary maps of habitat. From 2006 to 2008, the late Brad McRae introduced circuit theory as an alternative approach to model gene flow and the dispersal or movement routes of organisms. He posited concepts and metrics from electrical circuit theory as a robust way to quantify movement across multiple possible paths in a landscape, not just a single least-cost path or corridor. Circuit theory offers many theoretical, conceptual, and practical linkages to conservation science. We reviewed 459 recent studies citing circuit theory or the open-source software Circuitscape. We focused on applications of circuit theory to the science and practice of connectivity conservation, including topics in landscape and population genetics, movement and dispersal paths of organisms, anthropogenic barriers to connectivity, fire behavior, water flow, and ecosystem services. Circuit theory is likely to have an effect on conservation science and practitioners through improved insights into landscape dynamics, animal movement, and habitat-use studies and through the development of new software tools for data analysis and visualization. The influence of circuit theory on conservation comes from the theoretical basis and elegance of the approach and the powerful collaborations and active user community that have emerged. Circuit theory provides a springboard for ecological understanding and will remain an important conservation tool for researchers and practitioners around the globe.

Analytic hierarchy process based spatial biodiversity impact assessment model of highway broadening in Sikkim Himalaya

Spatial impacts of highway projects on biodiversity of North-Eastern Himalaya remains largely unexplored. Usually a number of ecological criteria are required in biodiversity impact assessment. However, a wide set of such criteria can be overwhelming for the decision-makers to assess the viability of such projects. SBIAM uses landscape metrics and experts’ opinion to create a single composite biodiversity value map. The weighted area loss under various project alternatives estimated from Biodiversity Value Map is compared to identify the most viable alternative. SBIAM uses AHP and curve fitting method in the biodiversity estimation. The study indicates that the highway broadening project in the study area will cause a moderate biodiversity loss. Sensitivity analysis of SBIAM indicates its robustness, and shows that forest patches near the highway are most sensitive to disturbances and patch proximity. SBIAM can be applied in varied spatial scales, terrains and development projects as a decision support tool.AbbreviationsAHPAnalytic Hierarchy ProcessBIABiodiversity Impact AssessmentICCRImpact Category Change RateLM(s)Landscape Metric(s)MACRMean Absolute Change RatePSIPatch Shape IndexSBIAMSpatial Biodiversity Impact Assessment ModelSESASpatially Explicit Sensitivity Analysis

喀斯特山区县域耕地景观生态安全及演变过程

为探讨喀斯特山区耕地生态环境变化状况，基于景观生态安全理论，以贵州省赤水市耕地景观为研究对象，选取景观生态安全指数、景观接近度指数、景观类型斑块破碎度、景观类型边界破碎度、景观类型斑块优势度指数、景观分离度指数、景观脆弱度指数等7个景观指数构建喀斯特山区耕地景观生态安全评价模型，分析2000-2014年研究区耕地景观生态安全的演变过程，试探耕地生态安全重心转移方向和驱动因素。结果表明：1）近15年来赤水市耕地景观生态安全重心向西北方向移动，耕地景观斑块密度、分形维数、破碎度下降，斑块形状指数、连接度上升，耕地形状逐渐向复杂状态转变，且分布趋于均匀化，斑块变得越来越群聚。2）耕地面积持续减少、生态安全性不断降低，旱地景观生态安全Ⅰ级区（危险区）向东南部地区扩张，Ⅲ级区（安全区）向Ⅱ级区（相对安全区）转变，Ⅱ级区向Ⅰ级区转变；水田景观生态安全Ⅱ级区由集中呈发散分布，Ⅲ级区向Ⅱ级区、Ⅰ级区转变，旱地和水田景观的生态安全不容乐观。3）通过灰色关联分析得出对研究区旱地景观生态安全演变及重心转移影响最大的因素是农业总产值，其次是粮食产量和农作物播种面积；对水田景观影响最大的是粮食产量，其次是单位化肥施用量和人口密度。;The ‘No. 1 Central Document’ issued in 2016 pushed the ‘three rural issues’ to the cusp. As an important component of the agricultural landscape, the features of the farmland landscape would directly affect the inside ecological processes and productivity of cultivated land, so as to finally decide whether the food problem of the 1.3 billion people in China can be solved or not. In order to investigate changes in the ecological environment of cultivated land in the Karst mountain area on the basis of landscape ecological security theory, the farmland of Chishui City (Guizhou Province, China) was selected as the research object in this essay. Firstly, datas like patch density, patch shape index, patch fractal dimension and patch stability factor were picked out and be used in order to analyse the characteristics of landscape patch evolution and spatial distribution of landscape pattern in the Karst mountain area. Secondly, a landscape ecological security evaluation model for farmland in the Karst mountain area should be constructed to analyze the evolution of the cultivated land's landscape ecological security from 2000 to 2004. In this step, ecological security index, patch proximity index, patch fragmentation, patch boundary fragmentation, landscape type patch dominance index, separation index, and landscape fragile index were used. Thirdly, on this basis of the past two steps, the centroid method commonly used in geography and economics was introduced to calculate the gravity center of the landscape ecological security of cultivated land. In the same time, both the gravity transfer distance model and the moving direction model were used to measure the distance and direction of the ecological safety center of cultivated landscapes. Finally, to explore the driving factors of ecological safety evolution and center of gravity shifts based on regional characteristics, 10 indices were selected, namely, population density, proportion of agricultural population, rate of regional construction land, grain yield, unit of cultivated land fertilizer, arable area, gross output value of agriculture, per capita disposable income of farmers, crop sown area, and number of rural practitioners, and a grey correlation analysis was performed for changes in the indices and changes in the ecological security indices of the cultivated landscape. The results showed as follow. Firstly, in the recent 15 years, the ecological security center of gravity of cultivated land landscape in Chishui moved to the Northwest. Meanwhile the patch density, fractal dimension, and fragmentation decreased, the patch shape index and connection degree increased. The shape of the cultivated land gradually changed to a complex state, and the distribution tended to be homogeneous, whereas the patches became increasingly clustered. Secondly, arable land continued to decline, ecological safety decreased. According to the landscape ecological security index of cultivated land calculated results, it could be seen that the ecological security zone of dry land landscape was expanding to the southeast, and the safe areas was changed to the the relatively safe areas, and the relatively safe areas was changed to the dangerous areas; The relatively safe areas of paddy field landscape changed from a centralized distribution to a divergent distribution, the safe areas transformed the relatively safe areas and hazardous areas. The ecological security of dry land and paddy field landscape was not optimistic. Thirdly, the gray analysis results indicated that the driving factors that affect the evolution of landscape ecological security and the transfer of gravity in dry land of the study area were obtained, and the maximum was the total agricultural output value, followed by grain yield and crop sown area. Grain yield was the most important factor affected by the evolution of landscape ecological security and gravity transfer in paddy fields, followed by the level of fertilizer application and population density.

Drivers of community assembly in tropical forest restoration sites: role of local environment, landscape, and space.

There is increasing recognition that community assembly theory can offer valuable insights for ecological restoration. We studied community assembly processes following tropical forest restoration efforts, using dung beetles (Scarabaeinae) as a focal taxon to investigate taxonomic and functional patterns of biodiversity recovery. We evaluated the relative importance of the local environment (i.e., canopy cover, understory cover, tree basal area, and soil texture), landscape context (i.e., habitat patch proximity and availability and percentage of surrounding area classified as natural forest or Eucalyptus spp. plantation), and space (i.e., spatial proximity of the study areas to estimate dispersal limitation or unmeasured spatially structured processes) on dung beetle species and functional trait composition across a gradient of 15 restoration sites in Brazilian Atlantic Forest. We also assessed which factors were the primary determinants in the establishment of individual dung beetle functional groups, classified according to size, food relocation habit, diet, and period of flight activity. Both species and functional trait composition were most strongly influenced by the local environment, indicating that assembly was predominantly driven by niche-based processes. Most of the variation explained by space was co-explained by local environment and landscape context, ruling out a strong influence of dispersal limitation and random colonization on assembly following restoration. In addition, nearly all of the variance explained by landscape context was co-explained by local environment, suggesting that arrival and establishment at a site depends on both local and landscape-scale environmental factors. Despite strong evidence for niche-based assembly, a large amount of variation remained unexplained in all models, suggesting that stochastic processes and/or unmeasured environmental variables also play an important role. The relative importance of local environment, landscape context, and space changed considerably when analyzing the assembly mechanisms of each functional group separately. Therefore, to recover distinct functional traits in restoration sites, it may be necessary to manipulate different components of the local environment and surrounding landscape. Overall, this study shows that assembly rules can help to better understand recovery processes, enabling improvement of future restoration efforts.

Preliminary study of habitat preferences of red brocket deer (Mazama temama) in a mountainous region of central Mexico

Introduction: Red brocket deer ( Mazama temama ) is a cervid distributed along Mexico and Central America, and an important element for subsistence hunters. However, the availability of information of this species is very limited, especially in the mountainous ranges of its geographical distribution. The aim of this study was analyzing the habitat preferences of the red brocket deer in the highlands located in the Mexican states of Puebla, Oaxaca, and Veracruz. Methods: We evaluated the habitat use-availability of the brocket deer in relation to four habitat variables (vegetation type, vegetation cover, plant species richness, and slope). We considered the presence of deer signs and tracks as an indicator of use, while the availability was evaluated by random points. We use chi-squared tests in combination with Bonferroni confidence intervals to determine if the red brocket deer preferred or avoided the selected habitat variables. Results: Results showed that brocket deer selected coffee agroecosystems and avoided areas covered by secondary growth vegetation. Likewise, we observed that the species selects high vegetation cover sites and intermediate plant species richness. Discussion and conclusions: It has been reported that this species are commonly found in areas with slight human influence, our results suggest that the red brocket deer can also use sites with low-level disturbance, such as coffee agroecosystems. However, the use of these sites is associated with the proximity of patches of vegetation in good condition. In Mexico, the red brocket deer is an important species for management and conservation of Management Units for Wildlife Conservation (Unidades de Manejo y Aprovechamiento Sustentable de Vida Silvestre; UMAs for their Spanish initials), so our study results help to understand how the species respond to the habitat characteristics of their environment. This information will help to develop the relevant conservation and management measures that help to maintain healthy populations of the species.

Bird Communities in Amazonian White‐Sand Vegetation Patches: Effects of Landscape Configuration and Biogeographic Context

AbstractVegetation growing on white‐sand soils is patchily distributed across the Amazon and is characterized by scrublands or open vegetation types (white‐sand campinas) and by forests (white‐sand forests) surrounded by contrasting habitat types. We studied birds in patches of white‐sand campinas in contrasting landscapes in four regions located in distinct biogeographic units delimited by major rivers. Our aim was to investigate the contribution of landscape configuration and biogeographic context to patterns of species diversity and distribution. Aracá and Viruá landscapes (on opposite sides of Rio Branco) are composed by large and continuous patches of white‐sand campinas, while Jaú, Novo Airão and Uatumã landscapes (on opposite sides of Rio Negro) are composed by small patches of white‐sand campinas isolated by continuous terra firme forests. Birds were sampled using mist‐nets and qualitative censuses, and were classified as white‐sand vegetation specialists or non‐specialists. Bird species diversity was significantly different among studied regions, and composition was significantly different for both, specialists and non‐specialists birds. Local variability in species diversity and composition was best explained by white‐sand campina area, patch proximity, and distance to major rivers. We conclude that landscape configuration and biogeographical context influence patterns of bird diversity, abundance, and composition in Amazonian white‐sand campinas.

Landscape factors affecting the distribution of the great tit in fragmented urban forests of Seoul, South Korea

Seoul City, as the capital and largest metropolis of South Korea, has high population density, and its remaining forests are extremely fragmented as a result of intensive development. The purpose of this study is to analyze the distribution of the great tit (Parus major) and develop a habitat model. Tits have been known as forest birds that inhabit urban forests in Seoul City. A Seoul biotope map and land cover map were combined, and the urban forest areas were delineated on these maps. As factors affecting the distribution of the great tit, landscape indices were calculated by separating them into intrapatch indices, namely logged patch area (PA), area-weighted mean patch shape index (PSI), tree rate (TR), and tree area (TA), and interpatch indices, namely patch degree (PD), patch betweenness (PB), patch proximity (PP), and difference probability of connectivity (DPC), to analyze the internal properties of the patches and their connectivity by tit occurrence data. The results of a t test analyzing the differences of habitat variables by great tit presence/absence and distribution showed differences in PA (p < 0.05), PSI (p < 0.001), TR (p < 0.01), TA (p < 0.001), PD (p < 0.05), PB (p < 0.01), PP (p < 0.05), and DPC (p < 0.1). In the results of logistic regression modeling, in most cases, more than one model had ΔAICc less than 2.0, suggesting that multiple models may be the best model. In the comprehensive models, the TR, PB, and DPC metrics were the best predictors. Among all variables in the intrahabitat model, PSI was the best predictor of species occurrence. Within the interhabitat model, DPC was the best predictor and had a positive relationship with species occurrence, which is the most important of all the factors. In other words, the great tit is more likely to be found in a large circular forest patch than a small and long-shaped forest patch, and connectivity in the threshold distance is the most important factor in predicting great tit occurrence. These results suggest that ecological potential, not only “location potential” but also “supply potential,” should be considered in fragmented urban forests.

Landscape pattern influences nekton diversity and abundance in seagrass meadows

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 507:139-152 (2014) - DOI: https://doi.org/10.3354/meps10818 Landscape pattern influences nekton diversity and abundance in seagrass meadows Geoffrey M. Hensgen1,*, G. Joan Holt2, Scott A. Holt2, Jason A. Williams3, Gregory W. Stunz3 1Colorado River Alliance, 3625 Lake Austin Boulevard, Austin, TX 78703, USA 2Marine Science Institute, University of Texas at Austin, 750 Channel View Drive, Port Aransas, TX 78373, USA 3Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA *Corresponding author: ghensgen@gmail.com ABSTRACT: We studied how spatial qualities and configuration of seagrass patches influence the diversity and abundance of resident nekton. Shallow landscapes of equal area (4225 m2) in 2 bays were mapped and sampled in the summer and fall to identify different qualities of landscape structure and the abundance and diversity of nekton. Two suites of characteristics were found to describe the natural landscape structure: (1) habitat area, connectivity, patch proximity and patch density; and (2) patch shape complexity and edge length. These were used to quantitatively distinguish between 3 naturally occurring seagrass landscape patterns: (1) small, isolated patches; (2) reticulated edge patches; and (3) continuous cover. Species evenness (Pielou’s J’) was significantly lower in small, isolated patches and reticulated edge patches compared to continuous cover. This pattern was temporally consistent despite significant seasonal differences in total nekton density and seasonal shifts in the distribution of individual species among landscape patterns. Nekton species density (no. of species per 61.2 m2 of seagrass) and species richness (no. of species per 1683 ind. sampled) did not differ significantly among landscape patterns; however, a landscape structure threshold may exist for species evenness between 45 and 85% cover. High densities of shrimp in small, isolated patches and reticulated edge patches during summer drove species evenness levels lower and overall nekton density levels higher than in continuous cover. Large expanses of continuous seagrass harbor more stable nekton communities across time. They may provide enough space for different species to feed and reproduce without depleting food resources to the point that nekton populations become unstable. KEY WORDS: Biodiversity · Seagrass · Landscape structure · Habitat fragmentation Full text in pdf format Supplementary material PreviousNextCite this article as: Hensgen GM, Holt GJ, Holt SA, Williams JA, Stunz GW (2014) Landscape pattern influences nekton diversity and abundance in seagrass meadows. Mar Ecol Prog Ser 507:139-152. https://doi.org/10.3354/meps10818 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 507. Online publication date: July 17, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

The Weight of the Past

In order to understand the importance of past land use and current ecological factors relating to oak regeneration within pine plantations, we hypothesized that native forest regeneration within plantations depends largely on in situ biological legacies as a source of propagules. We analyzed native oak regeneration in 168 pine plantation plots within the Sierra Nevada (southern Spain) in relation to land use type in 1956, oak patch proximity, and pine tree density. Historical land use patterns were determined from 1956 aerial photographs, and these were compared to 2004–2005 inventory data and additional orthophoto images. Aerial photograph of an area of the Sierra Nevada mountains (southern Spain) in 1956 (top) and 2001 (bottom). During the period 1950–1980, many heavily overharvested agricultural lands were abandoned, and were then converted to pine plantations. Photo credit: A. J. Pérez-Luque, obtained from Ortophotos (Andalusian regional government). (a) Dense pine plantations in Sierra Nevada Mountains (southern Spain). These forest plantations are usually characterized by higher stand density and lower tree diversity. (b) Within these forests we find recruits of native oak Quercus ilex ssp. ballota (Desf.) Samp. (c) The number of Q. ilex recruits per sampled area (estimated from a forest inventory carried out in 2005) were used as the oak regeneration variable in the study. Photo credit: A. J. Pérez-Luque. The oak recruitment in the pine plantations also depends on the dispersion distance from native forest. In this photo we show a native forest patch acting as a source of oak propagules for an adjacent pine plantation. Photo credit: A. J. Pérez-Luque. These photographs illustrate the article “The weight of the past: land-use legacies and recolonization of pine plantations by oak trees” by Irene Navarro-González, Antonio J. Pérez-Luque, Francisco J. Bonet, and Regino Zamora, published in Ecological Applications 23(6):1267–1276, September 2013. http://dx.doi.org/10.1890/12-0459.1

The weight of the past: land‐use legacies and recolonization of pine plantations by oak trees

Most of the world's plantations were established on previously disturbed sites with an intensive land-use history. Our general hypothesis was that native forest regeneration within forest plantations depends largely on in situ biological legacies as a source of propagules. To test this hypothesis, we analyzed native oak regeneration in 168 pine plantation plots in southern Spain in relation to land use in 1956, oak patch proximity, and pine tree density. Historical land-use patterns were determined from aerial photography from 1956, and these were compared with inventory data from 2004-2005 and additional orthophoto images. Our results indicate that oak forest regeneration in pine plantations depends largely on land-use legacies, although nearby, well-conserved areas can provide propagules for colonization from outside the plantation, and pine tree density also affected oak recruit density. More intense land uses in the past meant fewer biological legacies and, therefore, lower likelihood of regenerating native forest. That is, oak recruit density was lower when land use in 1956 was croplands (0.004 +/- 0.002 recruits/m2 [mean +/- SE]) or pasture (0.081 +/- 0.054 recruits/m2) instead of shrubland (0.098 +/- 0.031 recruits/m2) or oak formations (0.314 +/- 0.080 recruits/m2). Our study shows that land use in the past was more important than propagule source distance or pine tree density in explaining levels of native forest regeneration in plantations. Thus, strategies for restoring native oak forests in pine plantations may benefit from considering land-use legacies as well as distance to propagule sources and pine density.

The role of landscape structure on the abundance of a disease vector planthopper: a quantitative approach

Studies of patchily distributed insect populations have made clear the importance of host patch size and degree of isolation in determining the distribution of these populations. For such populations, patch connectivity will have an effect on patterns of patch occupancy and regional dynamics. In the present study we performed a series of observations to estimate the effect of landscape structure on the abundance of Delphacodes kuscheli (Homoptera: Delphacidae), vector of “Mal de Rio Cuarto” disease to maize. Actively dispersing D. kuscheli individuals were collected in 19 sampling sites during the spring of 2004, using sticky traps placed at 2 m above ground level. Land use and landscape pattern were quantified, using Landsat 5 TM images for the area where each sampling site was placed. Four land use categories were considered in the analysis; winter pastures, winter cereals, perennial pasture and stubble. The spatial pattern analysis program FRAGSTATS was employed to estimate the patch area, patch proximity index, Total Class Area and the Mean Proximity Index for each of the land use categories in those sites where insect samples were taken. Partial Least Squares Regression analysis techniques were employed to relate the mean abundance of D. kuscheli and the landscape measures. Eighty percent of the variation of the mean insect abundance was explained by two first PLSR components. The proximity index of the local host patches, the amount of area left to stubble, local host patch area and total area of winter pastures were the most important variables affecting the abundance of dispersing D. kuscheli individuals. We found that the abundance of the dispersive fraction of the population of D. kuscheli is affected mostly by the surrounding landscape, particularly by the proximity of other host patches, and the permeability of the matrix represented by the stubble.

Spatially explicit models to analyze forest loss and fragmentation between 1976 and 2020 in southern Chile

Forest fragmentation threatens biodiversity in one of the last remaining temperate rainforests that occur in South America. We study the current and future impacts of fragmentation on spatial configuration of forest habitats at the landscape level time in southern Chile. For this purpose, we identify the geophysical variables (“pattern drivers”) that explain the spatial patterns of forest loss and fragmentation between 1976 and 1999 using both a GIS-based land-use change model (GEOMOD) and spatially explicit logistic regression. Then, we project where and how much forest fragmentation will occur in the future by extrapolation of the current rate of deforestation to 2010 and 2020. Both modeling approaches showed consistent and complementary results in terms of the pattern drivers that were most related to deforestation. Between 1976 and 1999, forest fragmentation has occurred mainly from the edges of small fragments situated on gentle slopes (less than 10°) and far away from rivers. We predict that patch density will decline from 2010 to 2020, and that total forest interior area and patch proximity will further decline as a result of forest fragmentation. Drivers identified by these approaches suggest that deforestation is associated with observed local socio-economic activities such as clearance of forest for pasture and crops and forest logging for fuelwood.

Evaluating Residual Tree Patches as Stepping Stones and Short‐Term Refugia for Red‐Legged Frogs

Abstract: Temperate pond‐breeding amphibians are vulnerable to forest fragmentation because they must access upland terrestrial sites during the nonbreeding season but are prone to desiccation in hot, dry environments without canopy cover. Harvesting techniques that retain live trees in the cut block are advocated for sustaining forest biodiversity, but the effects of these practices on amphibians are unknown. We studied red‐legged frogs (Rana aurora) in movement trials to assess: 1) how short‐term use of residual trees was affected by tree patch size, streams, and neighborhood features; 2) whether residual tree patches were used as stepping stones in negotiating cut blocks; 3) the effects of patch size and patch proximity in altering movement paths; and 4) the effects of retention level and patch size on interpatch distance. Residual tree patches were potentially valuable short‐term refugia but their value was size dependent. Virtually all frogs released at the base of single trees or inside small tree clusters left within 72 hours, but the proportion leaving decreased curvilinearly with increasing patch size. Frogs were less likely to leave tree patches with a running stream or where neighborhood stream density was high. Residual tree patches did not systematically alter movement paths. Frogs intercepted residual tree patches mostly at random and had to be within 5‐20 m of a tree patch before moving to it in greater proportions than expected by chance. However, amphibian movements were biased toward large (0.8 ha) patches and away from small (0.3 ha) patches 50 m away. Our results indicated that residual trees should not be retained singly but should be aggregated in groups between 0.8 ha and 1.5 ha, preferably in stream locations.

Influence of landscape pattern on breeding distribution and success in a threatened Alcid, the marbled murrelet: model transferability and management implications

Summary The marbled murrelet Brachyramphus marmoratus is a threatened Alcid nesting in old‐growth coastal forests from central California to Alaska. Logging has greatly reduced the amount and altered the pattern of the species’ nesting habitat. Landscape fragmentation effects on the breeding ecology of the species are poorly understood because of the inaccessibility of nest sites. Using radio‐telemetry, 157 marbled murrelet nests were located in two old‐growth areas in British Columbia, Canada, with different logging histories. Probable breeding success was estimated from nest attendance patterns by radio‐tagged parents. Information‐theoretic and hypothesis‐testing methods were used to model breeding distribution (used vs. random unknown sites) and success (successful vs. failed nests) within c. 50‐km radius extents at a scale of 2·3‐km radius landscapes. Intersite transferability of distribution models was tested. Breeding distribution was positively related with old‐growth patch proximity, edge density (natural and artificial) and contrast, proportion of landscape under old‐growth or core habitat, and interspersion of old‐growth patches; it was negatively related with coastal zone proximity and mean old‐growth patch size. Breeding success was negatively affected by the edge contrast, coast proximity and proportion of young forest, probably reflecting the distribution of nest predators. All distribution models discriminated well between used and random landscapes within the training area. Intersite model transferability was good for 50% of the models. The models less predictive of the training site (area under the curve 0·676–0·738) were more transferable, probably because at the training site, which had considerably less old‐growth nesting habitat (18% of extent) than the testing site (55%), breeding distribution was driven by a different subset of predictors. Synthesis and applications. Geographic information system (GIS) data were helpful in discriminating between landscapes known to be used by nesting marbled murrelets and those with unknown breeding status. Previous indirect inferences about landscape‐level effects on breeding distribution in the birds were shown to correspond with their true nesting distribution. Our results suggest that habitat fragmentation per se need not have a negative effect on the birds beyond that as a result of habitat loss, unless associated with an increased abundance of predators. Our results fine‐tune the existing habitat conservation guidelines by suggesting that protection of old‐growth forest adjacent to clearcuts is important. We provide a means for desktop classification of marbled murrelet landscapes. We advise the application of several different models, depending on the amount of remaining old‐growth forest, to evaluate the consistency of predictions.

Observations of tidal and springtime sediment transport in the upper Delaware Estuary

Suspended-sediment transport in the upper Delaware Estuary was investigated in Spring 2003 to examine mechanisms of material exchange from the tidal river to the turbidity maximum zone in the lower estuary. Timeseries records of currents and suspended-sediment concentration (SSC) were obtained between 18 March and 10 June 2003 using moored instrumentation deployed at two locations spanning the tidal river−estuary transition: (1) Tinicum Island, 90 km up-estuary of the Delaware Bay mouth in tidal freshwater; and (2) New Castle Flats, 40 km down-estuary of Tinicum in oligohaline waters. Environmental conditions during the observational period were typical for the spring season and included two river peakflows (1000–2000 m 3 s −1) and several moderate remote-wind events. Results indicate that SSC and tidal sediment flux vary spatially in the estuary with local current magnitude and the proximity of patches of easily resuspendable sediment. Landward of the turbidity maximum zone, SSC was not correlated with current velocity due to depletion of bed sediment sources early in the tidal cycle. In contrast, SSC and velocity within the turbidity maximum zone were well correlated due to an abundance of fine sediment generated by resuspension and advection. At both observational sites the depth-averaged residual current (Eulerian mean) and net sediment flux were seaward, and the flux magnitude increased 3–4 fold during river peakflow events on account of elevated ebb flow and bottom scour. The seaward residual current, mostly compensatory flow for Stokes Drift on flood tide, is an important mechanism of sediment transport to the estuarine turbidity maximum zone. Averaged over the 80-day study period, the cross-sectionally averaged sediment flux past New Castle (11 ± 4 × 10 8 kg) was significantly larger than that at Tinicum (4 ± 1 × 10 8 kg), and twofold larger than the estimated influx from river tributaries (5 ± 1 × 10 8 kg). The mass imbalance (∼7 × 10 8 kg) suggests that eroded bed sediment, previously deposited and stored in the upper estuary, was a major source of material to the turbidity maximum zone in Spring 2003.