Alternative approaches to assessing the natural regeneration of Scots pine in a Mediterranean forest

Abstract

absen

Biomass partitioning in a future dry andCO2enriched climate: Shading aggravates drought effects in Scots pine but not European black pine seedlings

“…But, thinning also increases light availability in the understorey, which might affect the performance of tree seedlings during drought. At dry locations in the Mediterranean, where summer drought is one of the most limiting factors for seedlings establishment (Castro, Zamora, Hódar, & Gómez, ; Moreno‐Fernández, Cañellas, Barbeito, Sánchez‐González, & Ledo, ; Pardos, Montero, Cañellas, & Ruiz del Castillo, ), canopy shading from “nurse plants” has been observed to enhance the regeneration of trees due to microclimatic amelioration (Gómez‐Aparicio, Gómez, Zamora, & Boettinger, ). Management practices that concomitantly alter the availability of light and water might thus have very different effects on regeneration.…”

Modeling sapling distribution over time using a functional predictor in a generalized additive model

“…It might be useful to use variables driving the regeneration as predictors in the model, like shrub cover, soil characteristics, cover, and depth of litter or grass in each quadrat. However, gathering this data on large plots requires a great effort and the influence of these variables on the seedlings of P. sylvestris has already been studied at smaller scales (González-Martínez and Bravo 2001;Pardos et al 2007;Barbeito et al 2011;Moreno-Fernández et al 2015a). On the other hand, new individuals of P. sylvestris are expected to be more affected by soil moisture than by other microsite characteristics (Barbeito et al 2009;Moreno-Fernández et al 2015a).…”

“…However, gathering this data on large plots requires a great effort and the influence of these variables on the seedlings of P. sylvestris has already been studied at smaller scales (González-Martínez and Bravo 2001;Pardos et al 2007;Barbeito et al 2011;Moreno-Fernández et al 2015a). On the other hand, new individuals of P. sylvestris are expected to be more affected by soil moisture than by other microsite characteristics (Barbeito et al 2009;Moreno-Fernández et al 2015a). However, because youngest individuals-seedlings-are less resistant to drought than older-saplings (Maseda and Fernández 2006;Rodríguez-García et al 2011;Manso et al 2014)-it seems it is more necessary to include environmental variables in models dealing with seedlings rather than in those dealing with older individuals-saplings.…”

“…These models allow the spatial distribution of new individuals to be defined in function of attributes of adult trees. Other authors used distance-dependent influence indices (Contreras et al 2011) and available light under the forest canopy or the global site factor as explanatory variables in different models (Pardos et al 2007;Moreno-Fernández et al 2015a). Distance-dependent influence indices determine, at a given point, the influence of the tree size (such as diameter, height, or crown variables) and the distance between trees and the studied point whereas the global site factor measures the amount of light at a given point by analyzing hemispherical photographs.…”

Natural Regeneration in a Multi-Layered Pinus sylvestris-Picea abies Forest after Target Diameter Harvest and Soil Scarification

“…Due to the hierarchical structure (spatial correlation: regeneration subplots within overstory measurement plots within treatment areas within blocks) and the zero-inflation (i.e., a large number of subplots with no seedlings or saplings) of the combined regeneration data set, generalized linear mixed effects modelling was applied using the R package "glmmADMB" [37,38]. In a first step, a model analyzing total subplot seedling density was developed using standardized seedling density (# of seedlings per 10 m 2 ) because of the varying regeneration subplot size used in surveys during 2009 and 2014 [39].…”