Recent climate changes interact with stand structure and management to determine changes in tree carbon stocks in Spanish forests

Abstract

Most temperate forests are accumulating carbon (C) and may continue to do so in the near future. However, the situation may be different in water-limited ecosystems, where the potentially positive effects of C and N fertilization and rising temperatures interact with water availability. In this study, we use the extensive network of plots of two consecutive Spanish national forest inventories to identify the factors that determine the spatial variation of the C stock change, growth, and mortality rate of forests in Peninsular Spain (below-and aboveground). We fitted general linear models to assess the response of C stock change and its components to the spatial variability of climate (in terms of water availability), forest structure (tree density and C stock), previous forest management, and the recent warming trend. Our results show that undisturbed forests in Peninsular Spain are accumulating C at a rate of~1.4 Mg C ha À1 yr À1 , and that forest structural variables are the main determinants of forest growth and C stock change. Water availability was positively related to growth and C accumulation. On the other hand, recent warming has reduced growth rate and C accumulation, especially in wet areas. Spatial variation in mortality (in terms of C loss) was mostly driven by differences in growth rate across plots, and was consistent with 'natural', self-thinning dynamics related to the recent abandonment of forest management over large areas of Spain, with the consequent increase in tree density and competition. Interestingly, the negative effect of warming on forest C accumulation disappears if only managed stands are considered, emphasizing the potential of forest management to mitigate the effects of climate change. However, the effect of forest management was weak and, in some cases, not significant, implying the need of further research on its impact.

Self-thinning in four pine species: an evaluation of potential climate impacts

“…Our results suggest that a lower precipitation could reduce potential carbon stocks in lowland pines but could be beneficial for P. uncinata growing in high altitudes. In line with this result, Vayreda et al (2012b) identified reductions on carbon accumulations in Spanish forests due to recent warming and due to lower water availability. Using the STLs, we can identify which species are likely to grow to larger sizes under new conditions and promote these species as a climate change adaptation strategy.…”

Forest management and carbon sequestration in the Mediterranean region: A review

“…These key characteristics, together with the frequent occurrence of disturbances such as fire or pests, have influenced the composition, structure and functioning of these forest ecosystems. Hence, in order to maintain the level of ecosystem services in this area, forest management is required, particularly in the light of reports that climate change is causing a reduction in the carbon sink capacity of unmanaged Spanish forests due to lower water availability (Vayreda et al, 2012).…”

Vulnerability of Spanish forests under climatic change: evaluation through models

“…temperatura o precipitación) en el periodo de estudio respecto al clima medio observado en un periodo de referencia (e.g. Vayreda et al 2012; Ruiz-Benito et al datos sin publicar). Por otra parte, la correlación entre series dendrocronológicas estandarizadas de crecimiento radial y series de variables climáticas para las especies puede usarse como un indicador de la sensibilidad climática de las mismas (e.g.…”

“…interacciones entre el clima y la competencia) que pueden causar efectos no proporcionales sobre los diferentes componentes de la sensibilidad de las especies como la productividad o la mortalidad (e.g. Linares et al 2010;Vayreda et al 2012;Ruiz-Benito et al 2013b). Además, otros procesos pueden causar importantes modificaciones en la abundancia y distribución de especies, desde por ejemplo interacciones planta-suelo (McCarthy-Neumann e Ibáñez, 2012), procesos a diferentes niveles tróficos (Harrington et al 1999) o efectos competitivos especie-específicos (Gomez-Aparicio et al 2011); hasta posibles cambios en la frecuencia e intensidad del ré-gimen de incendios (Pausas 2004;Pausas et al 2008) o cambios en el uso del suelo (Thuiller et al 2008).…”