Recent dynamics of Fagaceae and Pinaceae in temperate forests in Mexico and worldwide

Student thesis: Doctoral thesis

Abstract

The temperate forests are distributed in the northern hemisphere and are dominated mainly by Pinaceae and Fagaceae. In recent decades, several studies have documented the decline of these forests and the rapid changes they are experiencing because of climate change and anthropogenic disturbances. These studies indicate that, in many cases, the species of Fagaceae are invading areas that were previously dominated by Pinaceae. The main objective of this PhD thesis has been to analyze the relative dynamics of Pinaceae and Fagaceae in temperate forests, both globally and specifically in the case of Mexico, to understand the recent dynamics of these forests and how can be modified in a context of climate change. On a global scale, the specific objectives were: (1a) to establish if there is a directional substitution of Pinaceae by Fagaceae and if this substitution is consistent for all the large biogeographic regions with temperate forests; (1b) to determine whether these directional changes are associated with specific climatic conditions or reflect differences in the historical management of forests between regions. In the case of Mexican forests, the objectives were: (2a) to evaluate if there was a directional change in the relative abundance of Pinaceae compared to Fagaceae in Mexican pine-oak forests; (2b) to identify the environmental factors that determine the recent growth dynamics of Pinaceae and Fagaceae in the study area; (3a) to evaluate the spatial distribution of the recent Pinaceae and Fagaceae regeneration in pure and mixed forests of both groups of species to determine if the current patterns of regeneration suggest directional changes in forest composition; and (3b) to identify the environmental factors that determine the regeneration dynamics of Pinaceae and Fagaceae in these forests, including climatic factors, forest structure and the impact of management and the main disturbances. To achieve these objectives, we used bibliographic data, repeated sampling data from the National Inventory of Forests and Soils of Mexico, and statistical models. We combined analysis of factors and processes at different spatio-temporal scales. At the global level we found that there is a trend of directional change from Pinaceae to Fagaceae in most of the temperate forests of the world that have been studied. This trend is especially pronounced in Europe and East Asia, and much less clear in eastern North America. The drivers of vegetation change were climate stress, succession dynamics and, to a lesser extent, anthropogenic disturbances. Transitions from Fagaceae to Pinaceae were more common in forests under natural disturbance regimes. In the temperate Mexican forests there is no clear directional pattern showing changes in the relative abundance of Pinaceae and Fagaceae in the tree layer. Growth patterns, however, provide evidence that Fagaceae species are being favored by temperature increases, while Pinaceae are being negatively affected in warmer environments. The spatial patterns of regeneration are affected by forest structure, by climate and by the history of disturbances and land tenure. The regeneration of Fagaceae is in general more abundant than that of Pinaceae and is favored mainly by warm temperatures and presence of fires. Overall, our results suggest an increase in the abundance of Fagaceae to the detriment of Pinaceae in the medium term, especially in the context of climate change. These changes could have important impacts on the functioning of forests and their resilience to environmental changes.
Date of Award28 Jan 2019
Original languageEnglish
Awarding Institution
  • Universitat Autònoma de Barcelona (UAB)
SupervisorJordi Martinez Vilalta (Director) & Javier Retana Alumbreros (Co-director)

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