Is There an Equivalence between Measures of Landscape Structural and Functional Connectivity for Plants in Conservation Assessments of the Cerrado?

Abstract

Landscape connectivity can be assessed based on the physical connection (structural connectivity) or the maintenance of flow among habitats depending on the species (functional connectivity). The lack of empirical data on the dispersal capacity of species can lead to the use of simple structural measures. Comparisons between these approaches can improve decision-making processes for the conservation or restoration of habitats in fragmented landscapes, such as the Cerrado biome. This study aimed to understand the correspondence between the measures of landscape structural and functional connectivity for Cerrado plants. Three landscapes with cerradão patches in a pasture matrix were selected for the application of these metrics based on the functional connectivity of four profiles of plant dispersal capacity. The results showed divergent interpretations between the measures of landscape structural and functional connectivity, indicating that the assessment of biodiversity conservation and landscape connectivity is dependent on the set of metrics chosen. Structurally, the studied landscapes had the same number of cerradão patches but varied in optimal resource availability, isolation, heterogeneity, and aggregation. Functional connectivity was low for all profiles (based on the integral index of connectivity—IIC) and null for species with a low dispersal capacity (based on the connectance index—CONNECT), indicating that species with a medium- to long-distance dispersal capacity may be less affected by the history of losses and fragmentation of the Cerrado in the pasture matrix. The functional connectivity metrics used allowed a more robust analysis and, apparently, better reflected reality, but the lack of empirical data on dispersal capacity and the difficulty in choosing an indicator organism can limit their use in the management and planning of conservation and restoration areas.

Propagation distance thresholds of woody Cerrado species in a pasture matrix

“…The low permeability of the matrix can also hinder or prevent the flow and dispersal of species (Forman, 1995; Driscoll et al, 2013; Deans & Chalcraft, 2017). Indexes of functional connectivity for plants obtained for the same landscapes L1, L2 and L3 (Issii et al, 2020) suggest low connectivity, especially for plants with a short dispersion distance. This analysis was performed based only on the distances among habitats and plant dispersal abilities in meters and did not consider matrix resistance.…”

“…This analysis was performed based only on the distances among habitats and plant dispersal abilities in meters and did not consider matrix resistance. Thus, the potential landscape functional connectivity for plants is expected to be even lower, especially when considering that the effects of the matrix may be more intense on seed‐dispersing fauna (Issii et al, 2020). In the case of forest birds, movement in the pasture matrix tends to be more regular and oriented to habitat fragments when compared with movement in other matrices, such as silvicultural and agricultural systems, allowing greater dispersal success than the agricultural matrix (Biz et al, 2017).…”

“…Of all the landscapes studied, L3 represents the best connectivity condition (Issii et al, 2020). This might have positively affected dispersal, which would partially explain the high abundance of regenerating individuals sampled in this landscape (52% of the entire sample of this study).…”

Mapping of Ecological Corridors as Connections between Protected Areas: A Study Concerning Sardinia, Italy

“…In particular, the second definition reflects the dual nature of connectivity, which entails a structural and a functional dimension (structural connectivity, functional connectivity). Structural connectivity is environmentally oriented, while functional connectivity is speciesoriented [12]. In this study, the second dimension of connectivity is considered and used.…”