Abstract
Disturbances can affect forest health and are important modulating factors of tree responses to environmental changes. However, standard methods are needed to assess and elucidate the relative effects of disturbance legacies on forest health among species. Here, structural sustainability was used to evaluate and to compare the impacts of contrasting disturbances on the health of Quercus ilex, Cedrus atlantica, and Abies pinsapo forest stands in Morocco and Spain. Disturbance effects on structural sustainability were related to type, severity, and land-use history, and showed inter-regional variability. Cedrus atlantica was structurally sustainable in its core distribution in Morocco, but not at its southern and northernmost geographical range limits. Quercus ilex was structurally sustainable in Morocco. Abies pinsapo was structurally sustainable at optimal elevation sites in Morocco (Rif Mts.), but considering the whole A. pinsapo dataset including Morocco and Spain, the species is structurally unsustainable due to excessive mortality. However, at the lower elevation plots in Spain, unsustainability was due to insufficient mortality. Although some forests were structurally sustainable, none of them were deemed healthy because none met their management objectives. Results also support the key role of disturbance regimes as drivers of forest structural sustainability and adaptive capacity.
Highlights
Forest structure is a driving force behind forest growth processes and productivity [1].Forests worldwide are impacted by both natural and anthropogenic disturbances including forest fragmentation, improper logging practices, overgrazing, insect and disease outbreaks, air pollution, and drought among others
While specific details are provided in Cale et al [9], we briefly describe structural sustainability index score calculation here
Ongoing decline of C. atlantica stands in intensively logged. These results suggest a recent expansion of C. atlantica at its northern geographical range limit, which and overgrazed areas of the Middle Atlas (Figures 1 and 2), structurally sustainable, are is currently related to a lack of size and age diversification and reduced stand mortality
Summary
Forest structure is a driving force behind forest growth processes and productivity [1].Forests worldwide are impacted by both natural and anthropogenic disturbances including forest fragmentation, improper logging practices, overgrazing, insect and disease outbreaks, air pollution, and drought among others. Substantial, long-term disturbance impacts result from changes in spatial forest structure [1]. Changes in forest structure and land use history, in particular, can have cascading, negative effects on co-dependent forest species such as wildlife and vegetation [2], as well as on ecosystem functions and services (e.g., primary productivity, [3], carbon accumulation [4]). How these functions respond to mortality likely will link to forest structure as a legacy of forest management.
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