Quantifying the network connectivity of landscape mosaics: a graph-theoretical approach

Ricotta, Carlo; Stanisci, Angela; Avena, Giancarlo; Blasi, C.

doi:10.1556/comec.1.2000.1.12

Cited by 92 publications

(49 citation statements)

References 25 publications

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“…The most used method in landscape ecology is the graph theory that allows the representation and assessment of landscape connectivity (Ricotta et al 2000, Urban & Keitt 2001, Pascual-Hortal & Saura 2006. The graph theory method enables landscape representation as an interconnected network of patches (Ricotta et al 2000), the basic components of the net-work being the number of habitat patches (N) or nodes and links (L) or connecting elements (Saura & Hortal 2007, Saura & Rubio 2010. Our research proposes an evaluation of the effectiveness of Natura 2000 network in Romanian Alpine Biogeographical Region, analysing the connectivity of the protected forest surfaces, on the one hand, and for the whole forest surfaces (protected and unprotected), on the other hand.…”

Section: Manuscript Received Februarymentioning

confidence: 99%

Effectiveness of Natura 2000 network in Romanian Alpine Biogeographical Region: an assessment based on forest landscape connectivity

Niculae¹,

Avram²,

Vânău³

et al. 2017

Ann. For. Res.

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Abstract. Maintaining and increasing landscape connectivity, especially of forest landscapes, are some of the main concerns regarding biodiversity conservation. The connectivity of protected areas for different species represents an indicator for evaluating the effectiveness of the Natura 2000 network. Our research aims to evaluate the connectivity of forest landscapes in the Romanian Alpine Biogeographical Region (ABR) for various terrestrial species. We analysed the distribution of forest patches and Sites of Community Importance (SCI), as part of Natura 2000 network, in the Romanian ABR. We evaluated the connectivity of forest patches for terrestrial species with different dispersal distances, identifying those patches with significant contribution to maintain the forest landscape connectivity, through the graph theory approach. To quantify the importance of each node, we evaluated the dPCconnector fraction derived from the dPC index. Of the 125 SCIs in the Romanian ABR, 71 protected areas have over 1000 ha, four of them have more than 100,000 ha. The total protected surfaces cover ~35% of the Romanian ABR, and the forest surfaces, protected in SCIs, cover 26% of the total Romanian ABR. Regarding the connectivity scores, we found that the forest surfaces across the ABR are well connected (0.89 or 1 for different dispersal distances) in comparison with the Natura 2000 forest patches. The forest patches are well connected especially for the species with large dispersal distance in both cases (d = 25 km). For the species characterized by a small dispersion distance, the connectivity is lower (0.46) in the case of protected forests. Our results evidence that the connectivity objective of the forest surfaces protected through the Nature 2000 network is not totally achieved. Furthermore new protected areas are needed where the forest are still present for increasing landscape connectivity for species.

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Section: Manuscript Received Februarymentioning

confidence: 99%

Effectiveness of Natura 2000 network in Romanian Alpine Biogeographical Region: an assessment based on forest landscape connectivity

Niculae¹,

Avram²,

Vânău³

et al. 2017

Ann. For. Res.

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“…transport, communication and information networks, etc.) only some graph-based ecological applications tackling conservation problems have been recently reported (Keitt et al 1997;Bunn et al 2000;Ricotta et al 2000;Urban and Keitt 2001;Jordan et al 2003;Pascual-Hortal and Saura 2006). In graph theory, a graph is a set of nodes (or vertices) and links (or edges) such that each link connects two nodes.…”

Section: Graph Theorymentioning

confidence: 99%

“…Although there is a wide variety of connectivity indices in the literature (Hanski 1994;Bunn et al 2000;Ricotta et al 2000;Urban and Keitt 2001;Moilanen and Nieminen 2002;Jordan et al 2003;Calabrese and Fagan 2004), many of them have been found to present serious limitations that make them inadequate for effectively integrating connectivity in forest conservation planning (Pascual-Hortal and Saura 2006). Also, the spatial scales traditionally considered in forest management should be broaden to adequately characterize connectivity, which occurs at a landscape scale (Merriam 1984;Wiens et al 1997;Tischendorf and Fahring 2000;Raison et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Integrating landscape connectivity in broad-scale forest planning through a new graph-based habitat availability methodology: application to capercaillie (Tetrao urogallus) in Catalonia (NE Spain)

2007

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The loss of connectivity of forest landscapes is seriously hindering dispersal of many forest-dwelling species, which may be critical for their viability and conservation. In this context, explicitly incorporating connectivity considerations is an important challenge in current forest planning and management, but as yet there is a lack of operative methods for appropriate decision making in this respect. We describe a new methodology based on graph structures and a habitat availability index (integral index of connectivity) that integrates forest attributes (like habitat quality) and network connectivity in a single measure. We apply this methodology to examine the connectivity of the highly fragmented habitat of capercaillie (Tetrao urogallus) in Catalonia (NE Spain), where the threatened status of this forest bird species calls for landscapelevel forest planning solutions. We analyse data on the distribution of capercaillie forest habitat at 1 km spatial resolution obtained from the recent Catalan Breeding Bird Atlas. We determine the functionally connected regions existing within its habitat distribution and identify the forest habitat areas that are more important for the maintenance of overall landscape connectivity for this species. Based on these results, we provide recommendations on certain critical public forests where management oriented to the conservation of capercaillie habitat is more necessary. These results highlight the potential and practical interest of the proposed methodology for successfully integrating landscape connectivity in broad scale forest planning.

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“…The 316 greater the mean eccentricity of the graph nodes, the more elongated the topology of the 317 sampling design. In preliminary analyses, we had quantified the topology by other graph 318 theoretic measures (Harary index, degree centrality, betweenness centrality, closeness 319 centrality) (Minor & Urban 2008;Ricotta et al 2000), but these measures were rather strongly 320 associated (mostly linearly) with each other, therefore we used only the mean eccentricity in 321 the main analysis. 322 323 Random sampling and the subsequent analysis process described above was iterated 400 324 times at every sample size level, which resulted in a total of 1600 (4 sample sizes × 400 325 repetitions) unique sampling designs and variation partitioning analyses.…”

mentioning

confidence: 99%

Effect of field sampling design on variation partitioning in a dendritic stream network

Sály

Erős

2016

Ecological Complexity

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16Variation partitioning is one of the most frequently used method to infer the importance of 17 environmental (niche based) and spatial (dispersal) processes in metacommunity structuring. 18However, the reliability of the method in predicting the role of the major structuring forces is 19 less known. We studied the effect of field sampling design on the result of variation 20 partitioning of fish assemblages in a stream network. Along with four different sample sizes, a 21 simple random sampling from a total of 115 stream segments (sampling objects) was applied 22 in 400 iterations, and community variation of each random sample was partitioned into four 23 another property of sampling design, is the total number of sampling units in the sample, and 50 it is a simple measure of the sampling effort. An additional property is the topology of the 51 sampling units. Topology describes the geometry by which the sampling units are ecologically 52 connected to each other. When sampling units considered being connected, researchers 53 assume that material and individuals can move from one sampling unit to the other one (e.g., 54 Peterson et al. 2013). 55 56 Variation partitioning 57Ecologists try to reveal the mechanisms controlling the distribution of organisms by 58 investigating their spatial distributional patterns. One of the most frequently used statistical 59 methods for quantifying different sources of variation of communities is variation partitioning 60 (or variance partitioning), which was introduced into the ecological methodology by Borcard 61 et al. (1992). In a classical approach, this method uses a sites-by-species community matrix as 62 response data, and a sites-by-environmental variables matrix and a sites-by-spatial variables 63 4 matrix as explanatory data to decompose additively the total variation of the response data 64 into four variance fractions/proportions by fitting canonical ordination models (canonical 65 correspondence analysis [CCA] or redundancy analysis [RDA]) on the data.

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Quantifying the network connectivity of landscape mosaics: a graph-theoretical approach

Cited by 92 publications

References 25 publications

Effectiveness of Natura 2000 network in Romanian Alpine Biogeographical Region: an assessment based on forest landscape connectivity

Effectiveness of Natura 2000 network in Romanian Alpine Biogeographical Region: an assessment based on forest landscape connectivity

Integrating landscape connectivity in broad-scale forest planning through a new graph-based habitat availability methodology: application to capercaillie (Tetrao urogallus) in Catalonia (NE Spain)

Effect of field sampling design on variation partitioning in a dendritic stream network

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