A new index to estimate ecosystem multifunctionality: Theoretical approach and an application to a burned forest of Central Eastern Spain

Several indexes have been proposed in the scientific literature and widely applied in many environments to evaluate the ecosystem multifunctionality. However, some indexes are based on the simple average of the environmental indicators (EIs) and ecosystem functions (EFs), which do not consider the ecosystem complexity and mutual relationships among the composing variables. In order to overcome these limitations, this study proposes a new method that modifies the ecosystem multifunctionality (EMF) index proposed by Maestre et al. (2012) on “Science” (hereafter “original EMF”). From a theoretical point of view, this index (“weighted EMF index” or WEMF), which is based on the Principal Component Analysis, retains only the most influential EIs on EMF, and discards the EFs with lower environmental and statistical significance. Moreover, the method can take into account the combined effects of some EIs that synergistically drive the ecosystem functions, and estimates the quantitative influence of each EF on the ecosystem multifunctionality. The application of the WEMF to a forest ecosystem of Central Eastern Spain affected by a wildfire and then subjected to post-fire management (mulching with wood chips or wheat straw) has shown that: i) the original EMF index gives non-significant differences in ecosystem multifunctionality among the experimented soil conditions, which contrasts evidence from the literature; and ii) the WEMF captures the severe disturbance due to wildfire on ecosystem multifunctionality compared to the unburned sites, giving lower importance to those EFs that marginally affect the EMF. Despite the encouraging validation attempt, the results of this study should be considered preliminary for a wider applicability of the WEMF in other environmental contexts.