An index for the assessment of degraded Mediterranean forest ecosystems

Abstract

Aim of study: Diagnosing the degradation degree of forest ecosystems is the basis for restoration strategies. However, there is no literature documenting how to quantify the forest degradation degree by using synthetic indicators, also because there is not a widely accepted definition for "forest degradation" and "degraded forest". Although there are many definitions of forest degradation that converge on the loss of ecosystem services, still today there are no largely accepted methods that give operational guidance to help in defining it. In the present research, with the aim to assess the degree of forest degradation, an integrated index -FDI, Forest Degradation Index -was developed.Area of study: In this first application, the FDI was applied and validated at stand level in two different Mediterranean forest types in two different case studies: Madonie and Nedrodi regional Parks (Sicily, Italy). The first dominated by sessile oak [Quercus petraea (Matt.) Liebl. subsp. austrotyrrhenica Brullo, Guarino & Siracusa], the second dominated by cork oak (Quercus suber L.).Material and methods: FDI is a synthetic index structured starting from representative and relatively easily detectable parameters. Here, we propose a set of six indicators that should be assessed to determine the forest degradation: Structural Index (SI), Canopy Cover (CC), Natural Regeneration Density (NRD), Focal Species of Degradation (FSD), Coarse Woody Debris (CWD), and Soil Depth (SD). FDI, here proposed and discussed, has been based on a MCDA (Multi-Criteria Decision Analysis) approach using the Analytic Hierarchy Process (AHP) technique, and implemented in order to contribute in finding simple indicators useful for forest restoration purposes that have an eco-functional basis.Main results: An integrated index of forest degradation has been defined. FDI values are comprised in the closed interval [0, 10], ranging from class I (Higher ecological functionality) to class IV (Lower ecological functionality). A forest fallen in the FDI-IV class can be defined degraded. In this first application, degradation occurs in SA-4 and in SB-4 where the lowest values (qualitative and quantitative) of the indicators were recorded and the FDI reach the minimum value.Research highlights: FDI has proved to be a useful tool at stand level in identifying a threshold value below which a forest can be termed as 'degraded'. In turn, FDI assumes the meaning of descriptor of the ecological functionality. Future development of the FDI will provide an extension of the application at landscape scale exploiting the potential advantages in coupling MCDA and GIS (Geographical Information Systems) techniques.

Forest Degradation: When Is a Forest Degraded?

“…If the evaluation approach requires categorization of a degraded forest, the integrated Forest Degradation Index (FDI) put forward by Modica et al [9] is applicable at the stand level, and based on six indicators: Structural index (which measures stratification of trees, i.e., their vertical distribution), canopy cover, natural regeneration density, focal species of degradation (i.e., typical associated species; functional species whose loss results in progressive changes to the forest, affecting a number of other species in turn), coarse woody debris (i.e., volume per hectare) and soil depth. By contrast with the above methodological approach, Ghazoul et al [27] propose the use of indicators linked to functional forest processes, including variables such as shoot growth in woody plants, seed availability in soil seed banks, abundance of seedlings, and age structure of common species (compared to that expected based on the successional state of the forest and the regeneration strategy of the various species).…”

“…In the majority of cases, the process involves a reduction in biomass and changes to the structure and species composition (biodiversity) of the forest, as well as in its natural regeneration. These changes in the system's biotic components may also lead to alterations in soil and water, and in the interactions between these components, ultimately affecting forest functioning and diminishing the provision of ecosystem goods and services [4,[7][8][9]. Thus, forest degradation refers to situations involving long-term and severe environmental changes, and does not cover short-term changes or variability such as those associated with forest management for silvicultural purposes [6,10].…”

Assessment and Monitoring Damage by <i>Coraebus florentinus</i> (Coleoptera: Buprestidae) in Mediterranean Oak Forests

“…The environmental degradation of the Mediterranean forests is an increasingly considered question when designing the management measures dealing with biodiversity or climate change [1]. The challenge of guaranteeing natural resources for future implies sustainable management of the forests, protection of relic preserved spaces and restoration of disturbed zones [2]. In agreement with these statements, the Habitat Directive (92/43/EEC, 1992), relative to the conservation of unmanaged habitats and of wild fauna and flora, established the obligation of taking all the compensatory measures necessaries to ensure the overall coherence of Nature 2000 Net (European Ecological Network for Conservation of Biodiversity [3]).…”

Modelling the Spatial Expansion of Green Manure Considering Land Productivity and Implementing Strategies

“…Assessment criteria usually proposed by experts and the Analytic Hierarchy Process(AHP)-based spatial multicriteria decision analysis (S-MCDA) method [50,51] were usually introduced to determine the criteria scores and weights [52][53][54][55][56][57].…”