Desertification and power laws     

Salvador Pueyo 《Landscape Ecology》2011,26(3):305-309

There is an ongoing controversy on the use of the patch-size distribution as an early warning signal for abrupt shifts to a desertified state in Mediterranean arid landscapes. This controversy started with Kéfi et al.’s suggestion that, when approaching the transition point to widespread desertification, vegetation patches would switch from a power-law (PL) to a truncated power-law (TPL) distribution. Here I show that, for fundamental reasons, no untruncated power law can be found in this context, irrespective of the level of degradation. This result does not deny the importance of the findings by Kéfi et al., but means that these have to be reinterpreted by moving from the PL/TPL dichotomy to other categorizations of the patch-size distribution. Physical constraints on patch-size distributions have general interest for landscape ecology.  相似文献   

A GIS-based method for the reconstruction of the late eighteenth century forest vegetation in the Prignitz region (NE Germany)   总被引：1，自引：0，他引：1  

Monika Wulf  Hendrik Rujner 《Landscape Ecology》2011,26(2):153-168

Our goal was to reconstruct the late eighteenth century forest vegetation of the Prignitz region (NE Germany) at a scale of 1:50,000. We also wanted to relate the historical forest vegetation to the actual and potential natural vegetation. For these purposes, we selected 15 woody species and transferred relevant data found in historical records from various sources together with the recent localities of (very) old individuals belonging to these woody species into ArcView GIS. Following multi-step data processing including the generation of a point density layer using a moving window with kernel estimation and derivation of vegetation units applying Boolean algebra rules together with information on site conditions, we derived 17 forest communities corresponding to the potential natural vegetation. We were able to reconstruct the historical forest vegetation for 90% of the forest area ca. 1780. Only two of the 17 forest communities covered large parts of the forested area. The oak forest with Agrostis capillaris covered about 44% of the total forest area, and alder forests on fenland made up about 37%. Oak-hornbeam forests with Stellaria holostea comprised slightly less than 6% of the forest area, while all other forest communities comprised less than 1%. The historical forest vegetation is more similar to the potential forest vegetation and quite different from the actual forest vegetation because coniferous tree species currently cover approximately two-thirds of the actual forest area. The most beneficial result of this study is the map of high-resolution historical vegetation units that may serve as the basis for various further studies, e.g., modelling long-term changes in biodiversity at the landscape scale.  相似文献   

A global perspective on reforesting landscapes     

Brian C. McCarthy 《Landscape Ecology》2011,26(4):601-602

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Modelling dynamics of ecosystem services basket in Mediterranean landscapes: a tool for rational management   总被引：1，自引：1，他引：0  

Gili Koniak  Imanuel Noy-Meir  Avi Perevolotsky 《Landscape Ecology》2011,26(1):109-124

Natural ecosystems are life-supporting systems providing diverse ecosystem services (ESs) and benefits to human societies: e.g., food and clean water, recreation opportunities or climate regulation. The contribution of natural and semi-natural ecosystems to the provision of such services depends to a large extent on vegetation structure and composition, which, in turn, change as a result of interactions between human decisions about land management, and spontaneous biological and environmental processes. Rational management of these dynamic ecosystems requires an ability to predict short- and long-term effects of management decisions on the desired ESs. The vegetation then contributes to, and modifies, the products and services obtained from the land. We applied mathematical modeling to study these complex relationships. We developed a model for a Mediterranean ecosystem which predicts the dynamics of multiple services in response to management scenarios, mediated by vegetation changes. Six representative ESs representing different groups were selected, based on available scientific information, for a detailed study: (1) density of geophytes, (2) potential contribution to honey production, (3) energy density of fleshy fruits foraged by birds, (4) forage for goats, (5) forage for cattle, and (6) carbon retention in woody plants. Mean contributions to each service by different vegetation cover types were estimated, and the overall service provided by the site was calculated as a weighted mean of these contributions. Services were measured in their appropriate units and subsequently standardized to a percentage of the maximum value observed in the study area. We attempted to combine all studied ESs, despite their different nature, into one “ESs basket”. This paper presents the dynamics of simulated vegetation composition and values of services in response to management scenarios involving grazing, fire and their combinations. Our approach can help land managers to evaluate alternative management scenarios by presenting the “services basket” obtained from the entire managed area.  相似文献   

Analyzing the effect of stepping stones on target patch colonisation in structured landscapes for Eurasian lynx     

Stephanie Kramer-Schadt  Tobias S. Kaiser  Karin Frank  Thorsten Wiegand 《Landscape Ecology》2011,26(4):501-513

With habitat loss and fragmentation having become two of the major threats to the viability of species, the question of how to manage landscapes for species conservation has attracted much attention. In this context, the planning of stepping stones has been proposed to increase connectivity in fragmented landscapes. We present a simulation study with a neutral landscape approach to assess the effects of stepping stones on colonization success. To that end, we used a spatially explicit, calibrated population model of the European lynx (Lynx lynx) coupled with structured landscapes, in which we could control the landscape parameters of dispersal habitat coverage and contagion, as well as the number and size of stepping stones available for breeding. In general, we found that colonization success increased with increasing habitat coverage but decreased with increasing habitat contagion, while the introduction of stepping stones had significant effects in critical situations. Especially at low to medium dispersal habitat coverage and high disperser mortality, stepping stones had a positive effect on colonization success when they were large enough to produce new dispersers, but negative effects when they were small and located in a way that dispersers would be distracted from more suitable breeding habitat patches. The latter clearly constituted a shading effect and argues for a thorough consideration of the trade-offs related to stepping stone size and location when implementing stepping stones as a conservation measure, especially when the number of individuals of conservation concern is low.  相似文献   

The influence of species traits and <Emphasis Type="Italic">q</Emphasis>-metrics on scale-specific β-diversity components of arthropod communities of temperate forests     

Martin M. Gossner  Jörg Müller 《Landscape Ecology》2011,26(3):411-424

Protection of biodiversity and ecosystem functions requires a better understanding of spatial diversity. Here we studied diversity patterns of true bugs and saproxylic beetles, sampled in 28 forest stands of southern Germany, using a hierarchical nested design of five increasingly broader spatial levels: trap location, stratum, forest stand, forest site, and ecoregion. We predicted that: (1) for large body-sized species (as a surrogate for highly mobile species) and host generalist species (low host specificity), the proportion of β-diversity decreases from small to large spatial scales; and (2) the differences between trait-based functional guilds in the proportion of β-diversity increase with increasing weighting of more-abundant species. Our results indicated that the ecoregion level is the most important diversity scale for both taxa and among functional guilds sampled, followed by the forest stand level. Specialized species were more strongly affected on the ecoregion level than generalist species. Differences in the proportion of β-diversity between functional guilds increased with increasing weighting of abundant species. The β-diversity patterns based on body size and host specificity were similar for true bugs, but partly contrasting for saproxylic beetles. Our results suggest that (1) future conservation schemes should focus on establishing new conservation sites in new ecoregions, rather than on enlarging existing protected areas; (2) host specificity might be a more meaningful trait than body size to be considered in biodiversity studies; and (3) common conservation approaches restricted to only large, conspicuous, but rare species might result in a mismatch of important biodiversity scales.  相似文献   

Biodiversity science     

Scott M. Pearson 《Landscape Ecology》2011,26(5):751-752

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A reverse keystone species affects the landscape distribution of woodland avifauna: a case study using the Noisy Miner (<Emphasis Type="Italic">Manorina melanocephala</Emphasis>) and other Australian birds     

Rebecca M. Montague-Drake  David B. Lindenmayer  Ross B. Cunningham  John A. Stein 《Landscape Ecology》2011,26(10):1383-1394

We explored the effects of a purported ‘reverse keystone species’, the Noisy Miner (Manorina melanocephala) using a long-term, large-scale dataset. Specifically, we identify whether this aggressive bird affects the landscape distribution patterns of other avifauna, by displacing them into, or restricting their distribution to, less productive areas, and in so doing, adheres to ‘isoleg theory’. We sought to determine the effect of abundance of the Noisy Miner on the abundance of other birds (individual species and groups), and determine whether that effect was consistent with varying site productivity, using a negative binomial distribution with a logarithmic link function, and an offset variable to account for variations in search effort. Relationships between abundance of Noisy Miners and habitat variables were examined using a Poisson distribution with a logarithmic link function scaled for extra-variation (quasi-Poisson regression). We demonstrate that when Noisy Miner abundance is low, many small passerine species are more abundant on high productivity sites. However, as Noisy Miner abundance increases, small passerine abundance decreases, with this decrease most apparent on productive sites. The same patterns were not evident for birds considered ‘non-competitors’ of the Noisy Miner. We identify that both site productivity and vegetation structure influence the abundance of the Noisy Miner. We reveal that the species increasingly tolerates ‘less desirable’ habitat attributes with increasing site productivity. The preference of the Noisy Miner for productive areas is likely to have deleterious impacts on the long-term survival and reproductive success of other Australian woodland bird species, many of which have already undergone severe declines.  相似文献   

Improving the writing of research papers: IMRAD and beyond     

Jianguo Wu 《Landscape Ecology》2011,26(10):1345-1349

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Beyond noise mitigation: managing soundscapes as common-pool resources     

Sarah L. Dumyahn  Bryan C. Pijanowski 《Landscape Ecology》2011,26(9):1311-1326

The extent of noise and its impacts continues to grow globally indicating a different approach from regulating individual noise sources is needed. We pose the argument that soundscapes, or the acoustic environment, should be managed as a common-pool resource (CPR). Using CPR theory, we argue that soundscapes possess key features of CPRs: (1) multiple soundscape users, (2) difficulty of exclusion, and (3) subtractability and degradation. Using Ostrom’s Social-Ecological Systems (SES) framework, we describe the main elements of soundscapes to consider for their sustainable management. In order to assess noise issues and challenges in managing national park soundscapes, we conducted interviews with U.S. National Park Service managers at parks identified as having air tour overflight impacts. While most managers indicated that aircraft overflights posed the most serious impacts to park resources and visitor experiences, the park units also experienced several other types of noise impacts including traffic on park roads, park maintenance operations, and different types of motorized recreational vehicles. Addressing single sources of noise is necessary, as is the case with air tour overflights, but we argue that a more comprehensive approach is needed to protect park soundscapes. From this study several SES framework variables emerged that need to be addressed for sustainable management, such as the lack of clear soundscape boundaries, availability of acoustic monitoring and data, and the number and types of soundscape users. Based on CPR theory and using the SES framework, the challenges and a potential new approach for sustainable management are discussed.  相似文献