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.     

Factors affecting private forest landowner interest in ecosystem management: linking spatial and survey data

Many factors influence forest landowner management decisions. This study examines landowner decisions regarding participation in ecosystem management activities, such as a landscape corridor cutting across their private lands. Landscape corridors are recognized worldwide as an important tool in biodiversity conservation. For ecosystem management activities to occur in areas dominated by a multitude of small private forest landholdings, landowner participation and cooperation is necessary. Data from a survey of landowners combined with an analysis of their land's spatial attributes is used to assess their interest in ecosystem management. Results suggest that spatial attributes are not good predictors of an owner's interest in ecosystem management. Other factors such as attitudes and opinions about the environment are more effective in explaining landowner interest. The results have implications for any land manager using GIS data and implementing ecosystem management activities on private forestland.     

Survival,reproduction, and recruitment of woody plants after 14 years on a reforested landfill

With the advent of modern sanitary landfill closure techniques, the opportunity exists for transforming municipal landfills into urban woodlands. While costs of fullscale reforestation are generally prohibitive, a modest planting of clusters of trees and shrubs could initiate or accelerate population expansions and natural plant succession from open field to diverse forest. However, among woody species that have been screened for use on landfills, these ecological potentials have not yet been investigated. We examined a 14-yr-old landfill plantation in New Jersey, USA, established to test tolerance of 19 species of trees and shrubs to landfill environments. We measured survivorship, reproduction, and recruitment within and around the experimental installation. Half of the original 190 plants were present, although survival and growth rates varied widely among species. An additional 752 trees and shrubs had colonized the plantation and its perimeter, as well as 2955 stems of vines. However, the great majority (>95%) of woody plants that had colonized were not progeny of the planted cohort, but instead belonged to 18 invading species, mostly native, bird-dispersed, and associated with intermediate stages of secondary plant succession. Based on this evidence, we recommend that several ecological criteria be applied to choices of woody species for the restoration of municipal landfills and similar degraded sites, in order to maximize rapid and economical establishment of diverse, productive woodlands.     

Riparian ecotone: A functional definition and delineation for resource assessment

We propose a geomorphic basis for defining riparian areas using the term: riparian ecotone, discuss how past definitions fall short, and illustrate how a linked sequence of definition, delineation, and riparian sampling are used to accurately assess riparian resources on the ground. Our riparian ecotone is based on the width of the valley (its floodprone area width) plus 30 meters on each side to encompass the important adjacent riparian functions, and 15 meters around obvious landslides. A functionally consistent riparian definition and delineation does not derive from land adjacent to a stream, rather it derives from the valley the stream runs through.     

Stream corridor management in the Pacific Northwest: I. Determination of stream-corridor widths

King County, Washington is a part of the rapidly growing Pacific Northwest region. This growth has placed pressure on stream corridors. Past studies about regional stream corridors provide a rich source of information for environmental planners and managers. This article draws on existing literature and case studies to provide guidelines for determining optimal stream corridor widths in a watershed located in King County, Washington.     

Stages in Dutch regional policy: 1945–1984

This paper discusses the major developments in regional policy in the Netherlands by relating the policy instruments and locations to stages in the socio‐economic and political development of the Netherlands from 1945 onwards. It concludes that, at present, the spatial dimension of economic policy has lost importance, and the support for peripheral regions is restricted.     

近10年长三角城际运输联系初步研究

通过对长三角地区1994—2003年各个城市客运量、货运量的分析,总结出近10年来该区域城际运输联系的基本特征。长三角客运量向交通轴线集中,交通走廊经济效应日益突现,货运量多中心分布,极化效应明显。长三角地区经济的快速发展是城际运输联系增强的推进器,区内交通轴线成为重要经济增长轴,南翼浙江借助于港口优势,其经济高速发展态势直逼北翼的苏南地区。     

Geographic variations in seed dispersal by ants: are plant and seed traits decisive?

The effect of local ant species on the dispersal success of a myrmecochorous plant, Helleborus foetidus, was analyzed in two populations of the Iberian Peninsula (Caurel and Cazorla, respectively). The contribution of the various local ant species to dispersal was very unequal. While 5 and 19 ant taxa visited the plants of Caurel and Cazorla, respectively, most removal activity (67 and 80%) was performed by two species only (Formica lugubris and Camponotus cruentatus, respectively). Visits by dispersers were also unequally distributed between neighboring plants. While some plants were always visited during the period of seed release, others were never visited. A regression model indicated that this pattern might be explained by two plant traits: ants preferred to visit plants that released more seeds and whose elaiosomes were richer in oleic acid. Although it has long been known that this compound triggers removal by ants, it is the first demonstration that quantitative variations in elaiosome traits contribute to variation in dispersal success. Finally, other variables being equal, morphological traits (seed size, elaiosome size, and elaiosome/seed size ratio) did not affect ant behavior. Although myrmecochory has long been considered a diffuse interaction, our results support the idea that, at local scale, a limited number of ant species may be decisive to its evolution.     

Comparing spatial conservation prioritization methods with site- versus spatial dependency-based connectivity

Larval dispersal is an important component of marine reserve networks. Two conceptually different approaches to incorporate dispersal connectivity into spatial planning of these networks exist, and it is an open question as to when either is most appropriate. Candidate reserve sites can be selected individually based on local properties of connectivity or on a spatial dependency-based approach of selecting clusters of strongly connected habitat patches. The first acts on individual sites, whereas the second acts on linked pairs of sites. We used a combination of larval dispersal simulations representing different seascapes and case studies of biophysical larval dispersal models in the Coral Triangle region and the province of Southeast Sulawesi, Indonesia, to compare the performance of these 2 methods in the spatial planning software Marxan. We explored the reserve design performance implications of different dispersal distances and patterns based on the equilibrium settlement of larvae in protected and unprotected areas. We further assessed different assumptions about metapopulation contributions from unprotected areas, including the case of 100% depletion and more moderate scenarios. The spatial dependency method was suitable when dispersal was limited, a high proportion of the area of interest was substantially degraded, or the target amount of habitat protected was low. Conversely, when subpopulations were well connected, the 100% depletion was relaxed, or more habitat was protected, protecting individual sites with high scores in metrics of connectivity was a better strategy. Spatial dependency methods generally produced more spatially clustered solutions with more benefits inside than outside reserves compared with site-based methods. Therefore, spatial dependency methods potentially provide better results for ecological persistence objectives over enhancing fisheries objectives, and vice versa. Different spatial prioritization methods of using connectivity are appropriate for different contexts, depending on dispersal characteristics, unprotected area contributions, habitat protection targets, and specific management objectives. Comparación entre los métodos de priorización de la conservación espacial con sitio y la conectividad espacial basada en la dependencia     

县域单元美丽乡村建设类型划分与生态廊道构建——以浙江省德清县为例

基于第一次地理国情普查数据,以浙江省德清县为例,探讨县域单元美丽乡村建设类型划分和生态廊道建设。首先,基于自然本底,将村域单元划分为3种类型:山地景观型、丘陵风光型和平原水乡型;在此基础上,考虑城市未来扩展空间,增加都市风貌型,最终将美丽乡村建设划分为4种类型。其次,依据资源空间分布,评价各个村域单元美丽乡村建设潜力,将所有村域分为3个等级:核心建设村落、重点建设村落和一般建设村落。第三,识别出对德清具有重要生态意义的6个生态保护区,考虑不同地表覆盖景观格局对动物迁移的阻碍差异,利用GIS空间分析方法,计算出迁徙成本最小的路径,识别出4条重要的生态廊道。第四,将识别的生态廊道与地表覆盖进行匹配调整分析,最终构建起德清县“六核心、四廊道”的生态空间格局。