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

Key message: Self-thinning lines are species- and climate-specific, and they should be used when assessing the capacity of different forest stands to increase biomass/carbon storage. Context: The capacity of forests to store carbon can help to mitigate the effects of atmospheric CO2 rise and climate change. The self-thinning relationship (average size measure ∼ stand density) has been used to identify the potential capacity of biomass storage at a given density and to evaluate the effect of stand management on stored carbon. Here, a study that shows how the self-thinning line varies with species and climate is presented. Aims: Our main objective is thus testing whether species identity and climate affect the self-thinning line and therefore the potential amount of carbon stored in living biomass. Methods: The Ecological and Forest Inventory of Catalonia was used to calculate the self-thinning lines of four common coniferous species in Catalonia, NE Iberian Peninsula (Pinus halepensis, Pinus nigra, Pinus sylvestris and Pinus uncinata). Quadratic mean diameter at breast height was chosen as the average size measure. The self-thinning lines were used to predict the potential diameter at a given density and study the effect of environmental variability. Results: Species-specific self-thinning lines were obtained. The self-thinning exponent was consistent with the predicted values of −3/2 and −4/3 for mass-based scaling for all species except P. sylvestris. Species identity and climatic variability within species affected self-thinning line parameters. Conclusion: Self-thinning lines are species-specific and are affected by climatic conditions. These relationships can be used to refine predictions of the capacity of different forest stands to increase biomass/carbon storage.</p

"New Forests" from the Twentieth Century are a Relevant Contribution for C Storage in the Iberian Peninsula

Land-use changes are one of the major drivers of global change. In many developed countries socioeconomic changes have induced forest expansion during the last centuries, with still seldom explored implications for ecosystem services. We assessed the growth rate and the contribution of these &ldquo;new forests&rdquo; on C storage under the imprint of land-use history from Mediterranean to temperate forests in two biogeographical regions in the Iberian Peninsula, using data from 6422 plots of the Spanish National Forest Inventory (1986&ndash;2007) and the land-cover map of 1956 to distinguish among pre-existing and new forests (appeared after 1956). Almost a quarter of current forests were new forests and they represented 22% of the total C pool. New forests maintained similar C stocks than pre-existing ones (~45Mgha&minus;1), but they are growing at rates 25% faster. Considering the whole Spanish forested territory, the new forest growth rate would offset around 9% of the rate of total C emitted in Spain between 1986 and 2007. The effects of land-use history on forest growth and C stocks varied with environmental conditions (for example, growth of new forests in areas with less water availability was higher than in pre-existing ones), supporting the idea that agricultural legacies may prevail in the long term. In a time when European forests exhibit the first signs of carbon sink saturation, our study endows a relevant ecological role to new forests appearing in the second half of the twentieth century

La importància del potassi en el creixement dels boscos

El potassi ha estat, en general, un element poc considerat en els estudis ecològics del creixement dels boscos. Partint d'aquest fet, un grup d'investigadors del CREAF a la UAB ha estudiat el paper d'aquest element en el creixement de 2836 parcel·les de boscos catalanes. Així, aquests investigadors han posat de manifest la importància del potassi per aquest tipus d'estudis ecològics i han millorat el coneixement que es tenia dels factors que influeixen en el contingut dels diferents elements, nitrogen i fòsfor a més del potassi, en les fulles i la fusta dels arbres. També han arribat a la conclusió que el contingut de potassi en els arbres està determinat per factors ambientals.El potasio ha sido, en general, un elemento poco considerado en los estudios ecológicos del crecimiento de los bosques. Partiendo de este hecho, un grupo de investigadores del CREAF, en la UAB, ha estudiado el papel de este elemento en el crecimiento de 2836 parcelas de bosques catalanes. Así, estos investigadores han puesto de manifiesto la importancia del potasio para este tipo de estudios ecológicos y han mejorado el conocimiento que se tenía de los factores que influyen en el contenido de los diferentes elementos, nitrógeno y fósforo además del potasio, en las hojas y la madera de los árboles. También han llegado a la conclusión de que el contenido de potasio en los árboles está determinado por factores ambientales.Potassium is generally not considered in ecological studies of forest growth. Based on this, a group of researchers at the CREAF in the UAB has studied the role of this element in the growth of 2836 forests parcels in Catalonia. Thus, these researchers have highlighted the importance of potassium for such ecological studies and improved knowledge of the factors that had influenced the content of these different elements, nitrogen and phosphorus plus potassium, in leaves and wood of trees. They also concluded that potassium content in trees is determined by environmental factors

The Ecological Forest Inventory of Catalonia: A tool for functional ecology

This paper describes the particular characteristics of IEFC that makes it singular unique tool for the advance of forest ecological understanding. The IEFC stressed by sampling uncommon variables such as biomass and production of branches and leaves, growth curves or nutrient content in wood, bark, branches and leaves. This additional information allowed to carry out some functional studies. In this paper we briefly review the most relevant results regarding: i) the geographical distribution of functional traits across levels of organization and intraspecific and interspecific variability along environmental gradients; ii) the positive relationship between species richness and timber production in Mediterranean forests; iii) the trend to higher growth during most of the twentieth century reversed from year 1970 by lower water availability and; iv) stoichiometric relationships of nutrients by species and functional groups along environmental gradients. Today it is clear that the inclusion of these functional variables in a forest inventory is essential to better understand forest responses to environmental changes and evaluate the suitability of different management strategies