The Role of Recent (1985–2014) Patterns of Land Abandonment and Environmental Factors in the Establishment and Growth of Secondary Forests in the Iberian Peninsula

Marina Palmero-Iniesta,Joan Pino,Lluís Pesquer,Òscar Gonzàlez-Guerrero,Xavier Pons,Miquel Ninyerola,Josep Maria Espelta,Cristina Domingo-Marimon,Mario Padial-Iglesias

doi:10.3390/land10080817

Abstract

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985–2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and aboveground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broadleaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth.

Highlights

Changes in land use and land cover are one of the main drivers of global environmental change given that they affect the properties of land surfaces, the provision of ecosystem services [1] and, the Earth’s energy balance and biogeochemical cycles [2,3]. deforestation is still one of the main manifestations of changes in land use and land cover, the net rate of forest loss decreased substantially worldwide during 1990–2020 due to a reduction in deforestation in certain countries and active and passive afforestation in others [4]
Broadleaf evergreen (BE) forests increased by 5.2%, while needleleaf evergreen (NE) forests showed no changes in their area
By the end of the study period, 14.8% of the forest area corresponded to secondary forests that had emerged during the 1985–2014 period

Summary

Introduction

Changes in land use and land cover are one of the main drivers of global environmental change given that they affect the properties of land surfaces, the provision of ecosystem services [1] and, the Earth’s energy balance and biogeochemical cycles [2,3]. deforestation is still one of the main manifestations of changes in land use and land cover, the net rate of forest loss decreased substantially worldwide during 1990–2020 due to a reduction in deforestation in certain countries and active and passive afforestation in others [4]. The expansion of secondary forests may increase the functional connectivity between forests (e.g., seed dispersal potential) and may facilitate migration and gene flow between tree populations in response to climate change [13], while potentially increasing the propagation of large wildfires, especially in southern Europe [14]. Apart from these environmental changes, the expansion of secondary forests has gained much attention owing to their role in carbon accumulation [15,16]. Fuchs et al [17] determined that afforestation and cropland abandonment made the greatest contribution to carbon sequestration during 1950–2010 in Europe, while Pan et al [16] reported that the C sink of China’s forests increased by 34% during

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