Oak seedling survival and growth along resource gradients in Mediterranean forests: implications for regeneration in current and future environmental scenarios

Abstract

Understanding seedling performance across resource gradients is crucial for defining the regeneration niche of plant species under current environmental conditions and for predicting potential changes under a global change scenario. A 2-year field experiment was conducted to determine how seedling survival and growth of two evergreen and two deciduous Quercus species vary along gradients of light and soil properties in two Mediterranean forests with contrasting soils and climatic conditions. Half the seedlings were subjected to an irrigation treatment during the first year to quantify the effects on performance of an alteration in the summer drought intensity. Linear and non-linear models were parameterized and compared to identify major resources controlling seedling performance. We found both site-specific and general patterns of regeneration. Strong site-specificity was found in the identity of the best predictors of seedling survival: survival decreased linearly with increasing light (i.e. increasing desiccation risk) in the drier site, whereas it decreased logistically with increasing spring soil water content (i.e. increasing waterlogging risk) in the wetter site. We found strong empirical support for multiple resource limitation at the drier site, the response to light being modulated by the availability of soil resources (water and P). Evidence for regeneration niche partitioning among Quercus species was only found at the wetter site. However, at both sites Quercus species shared the same response to summer drought allevation through water addition: increased first-year survival but not final survival (i.e. after two years). This suggests that extremely dry summers (i.e. the second summer in the experiment) can cancel out the positive effects of previous wetter summers. Therefore, an increase in the intensity and frequency of summer drought with climate change might cause a double negative impact on Quercus regeneration, due to a general reduction in survival probability and the annulment of the positive effects of (infrequent) 'wet' years. Overall, results presented in this study are a major step towards the development of a mechanistic model of Mediterranean forest dynamics that incorporates the idiosyncrasies and generalities of tree regeneration in these systems, and that allow simulation and prediction of the ecological consequences of resource level alterations due to global change.

Central Appalachians forest ecosystem vulnerability assessment and synthesis: a report from the Central Appalachians Climate Change Response Framework project

“…South-facing slopes may be particularly vulnerable to soil drying in late summer or fall. Seedlings will be more vulnerable to these effects than mature individuals; just one severely dry growing season per decade may greatly reduce regeneration success of most species (Gómez-Aparicio et al 2008).…”

“…Invasive plant species also have the potential to alter species composition and ecosystem functioning. The invasive tree ailanthus can increase carbon cycling rates and alter soil chemistry to favor rapid growth and subsequent forest colonization by new ailanthus seedlings (Gómez-Aparicio et al 2008).…”

Long-term sustainability of cork oak agro-forests in the Iberian Peninsula: A model-based approach aimed at supporting the best management options for the montado conservation

“…Moreover, the montado ecosystem is considered both a protected habitat within the EU habitats directive (92/43/EEC) and a high nature value farming system, according to the classification proposed by the European Environmental Agency (Paracchini et al, 2008). extensive and deep root system and in some cases seedlings shed leaves and resprout when the drought is over Gómez-Aparicio et al, 2008;Arosa et al, 2015). The cork oak has a thick insulating bark which evolved as a fire protection mechanism (Pausas, 1997;Catry et al, 2012) and which regrows after extraction for cork production (Pausas et al, 2009).…”

Germinación y emergencia de plántulas de cuatro especies de encino amenazadas

“…Their physiognomy, structure and composition depend on factors such as latitude, elevation, wind and precipitation patterns, as well as evolutionary history, all of which lead to the high beta diversity reported for this forest type (Bubb, May, Miles, & Sayer, 2004). Worldwide, TMCF cover a mere 0.14% of the land surface (Scatena, Bruijnzeel, Bubb, & Das, 2010) and are considered one of the most endangered ecosystems because of their limited distribution and the high rates of deforestation to which they are subjected (Toledo-Aceves, Meave, González-Espinosa, & Ramírez-Marcial, 2011 Valencia, 2004;Valencia & Gual-Díaz, 2014 (Valencia & Gual-Díaz, 2014) Several studies have analyzed early establishment in oaks and compared different habitats, including: a) forest successional stages (Li and Ma, 2003;Gómez, 2004;González-Rodríguez, Barrio, & Villar, 2012), b) light gradients within the forest (Gómez-Aparicio et al, 2008; Pérez-Ramos, Gómez-Aparicio, Villar, García, & Marañón, 2010), c) open sites vs. closed canopy forest (Negi, Negi, & Singh, 1996;Fan, Guo, Wang, & Duan, 2014) and different light environments under greenhouse and laboratory conditions (Khan and Shankar, 2001;Quero, Villar, Marañón, Zamora, & Poorter, 2007).…”