Seedling emergence and growth of Quercus spp. following severe drought effects on a Pinus sylvestris canopy

Abstract

Questions We addressed the following questions: (1) did defoliation and die‐off of the dominant Pinus sylvestris, induced by an extreme drought episode, favour emergence of other tree species; (2) did the defoliated canopies of P. sylvestris resulting from drought promote radial growth among other pre‐existing tree species seedlings under them? Location P. sylvestris forest in Central Pyrenees (NE Spain) affected by a severe drought in 2004–2005. Methods Despite increased focus on climate‐related forest die‐off, studies of the effects on regeneration processes following extreme drought remain scarce. We analysed whether an episode of drought‐induced mortality on the dominant P. sylvestris L. may act as a driver of vegetation shift. Seedlings of Quercus humilis Mill. and Q. ilex L. from 27 plots were sampled under P. sylvestris canopies with <50% and ≥50% defoliation (standing dead trees included) to determine age distribution and radial growth using a retrospective, dendrochronological approach. Results Drought‐induced canopy losses appear not to be compensated by regeneration of P. sylvestris. Recruitment of below‐canopy tree species (specifically Q. humilis and Q. ilex) that could potentially become dominant was high in the entire studied area. However, the spatial patterns of Quercus spp. regeneration following the 2004–2005 drought were complex. While the emergence of new Quercus spp. seedlings was reduced under open, drought‐induced canopies, growth of seedlings already established was favoured in open‐canopy conditions. Conclusions Although the effects of extreme drought events may disfavour the establishment of new recruits, enhanced growth responses of a pre‐established seedling bank could still contribute to accelerate forest dynamics under drier conditions. Because of the predicted increases in intensity and frequency of extreme droughts, monitoring studies are key to elucidate whether the initial patterns observed will be maintained in the long term, eventually leading to a vegetation shift.

Factors Affecting Natural Regeneration of Tropical Forests across a Precipitation Gradient in Myanmar

“…This finding supported the research by Galiano et al [45] and Parada and Lusk [46], which explored how drought or reduced rainfall limited the survival of plants at the seedling stage. In comparison with other studies, the density of natural regeneration at our study sites was lower than that of semi-evergreen forests in Myanmar studied by Oo [47], and higher than that of the secondary forests in Vietnam studied by Woo et al [48].…”

Large‐scale recruitment limitation in Mediterranean pines: the role of Quercus ilex and forest successional advance as key regional drivers

“…Overall, in mid‐elevation mountain pine forests, we observed a higher percentage of plots with recruitment of Q. ilex than of any pine species (http://onlinelibrary.wiley.com/doi/10.1111/geb.12111/suppinfo) and positive trends in Q. ilex recruitment in pine stands with absent or very low basal area of adult Q. ilex trees (http://onlinelibrary.wiley.com/doi/10.1111/geb.12111/suppinfo). These trends suggest that these forests follow successional trajectories towards oak or mixed pine–oak forests (Gómez‐Aparicio et al ., ; Urbieta et al ., ; Vilà‐Cabrera et al ., 2012a; Galiano et al ., ). The higher success of P. sylvestris recruitment above 1600 m a.s.l., however, contrasted with progressively lower and scant Q. ilex recruitment, suggesting autosuccessional trajectories at high elevations (http://onlinelibrary.wiley.com/doi/10.1111/geb.12111/suppinfo).…”

“…These results are consistent with recent trends observed at local and regional scales (e.g. Vilà‐Cabrera et al ., 2012a; Galiano et al ., ; Rabasa et al ., ; Urli et al ., ).…”

Refining predictions of population decline at species' rear edges

“…Oak seedling abundance and performance are higher under drought‐induced Scots pine decline but this association is not only restricted to the most drought‐prone stands at low‐altitudes. Habitat deterioration and past species‐selective management explain observed community dynamics at the local scale (Galiano, Martínez‐Vilalta, Eugenio, Granzow‐de la Cerda, & Lloret, ). The local community composition can be directly obtained from inventory data or field‐based sampling, directly informing on ecological marginality and supporting a better understanding of marginality type (Figures and a).…”