Regeneration dynamics in fragmented landscapes at the leading edge of distribution: Quercus suber woodlands as a study case

Abstract

Aims We studied the regeneration dynamics of woodlands and abandoned old fields in a landscape dominated by Quercus suber in its lower limits of rainfall and temperature. Two hypotheses were established: (1) regeneration of Quercus species is strongly favored by the presence of tree cover; and (2) growth of Q. suber is driven by the climatic variables that represent the lower ecological limit of its leading distribution edge. Methods We selected woodlands and old fields with and without tree remnants (n = 3 per type), and analyzed stand structure, soil parameters and tree growth. Results Succession was arrested in old fields without tree remnants. By contrast, remnant trees were accelerators of forest recovery in old fields. Tree cover played a fundamental role in Quercus recruitment throughout seed dispersal and facilitation that mitigate the effects of summer drought on seedlings. Also, tree cover improved soil parameters (e.g., organic matter) that are important factors for understanding differences in regeneration. Winter/spring precipitation exerted a positive effect on tree growth, as well as temperatures during winter/spring and September. Conclusions Regeneration dynamics are modeled by the density of tree cover in the cold and dry edge of the distribution area of Q. suber where Q. ilex is increasing in abundance. Although temperature has a positive effect on the tree growth of Q. suber, when demographic processes are considered, decreases in water availability likely play a critical role in Q. ilex recruitment. This in turn changes dominance hierarchies, especially in abandoned areas with little or no tree cover.

Natural regeneration of cork oak forests under climate change: a case study in Portugal

“…The lower acorn availability in stand B may be due to a lower tree density (Acácio et al, 2007). The results obtained in this study for cork oak forest systems in Northern Portugal are in accordance with trends reported in southern Portugal (Algarve and Alentejo provinces) and in the North subdivision of the Central plateau of the Iberian Peninsula (Salamanca province), where dense stands have shown a greater supply of acorns and a higher density of seedlings (Acácio et al, 2007;Montero-Muñoz et al, 2021;Ritsche et al, 2021).…”

Forest Conservation and Restoration Using the Emberger Index: Cork Oak as Study Case

“…On the other hand, the species occurrence in the early 20th century is not detailed and widely referenced; thus, the comparison with the actual range is hard to assess. However, we can assume that variation in the distribution in a century is not significant for a long-life tree, such as cork oak, so the responses to climate change can be stated by recent investigations about tree dieback and changes in regeneration processes [56][57][58][59]. However, we can presently deal with advanced remote sensing techniques, which are useful to obtain punctual and refined data; by coupling that information with indexes, such as Emberger's Index, it is finally possible to monitor the responses of forest species to variations in climate, at least for the next century.…”