Tree-line changes along the Andes: implications of spatial patterns and dynamics

Abstract

The Andes provide an extensive latitudinal and topographical framework for studying the factors that control the spatial patterns of forests (timberlines) and their species components expressed through the presence of tree growth forms (tree lines). Despite consistent overall similarities in landscape patterns, many processes must be unique, given the dramatic differences in species richness and biophysical constraints along the Andes. In all cases evaluated to date, morphological plasticity is a common trait of plant species that dominate at tree lines. In fact, many changes observed can be related to species-specific traits. Physiological limitations on tree growth form only explain species limits, while disturbances and cyclical climate fluctuations interact to affect many landscape patterns. Over long periods of time, tree lines provide unique habitats and perhaps opportunities for speciation. Understanding the spatial organization of tree-line dynamics is one viable research approach for evaluating the likely past fluxes and possible future changes.

Implications of fires on carbon budgets in Andean cloud montane forest: The importance of peat soils and tree resprouting

“…The Puna/Páramo region (>2000 masl) has long been populated leaving a strong human footprint in the current configuration of the landscape, both through agriculture and fire, particularly affecting the distribution of the treeline (Sarmiento and Frolich, 2002;Keating, 1997;Young and León, 2007). Although land use activities in TMCFs vary greatly depending on socio-economic and environmental drivers, a predominant pattern common to most TMCFs is the conversion to pasture (Young and León, 2007).…”

“…Although land use activities in TMCFs vary greatly depending on socio-economic and environmental drivers, a predominant pattern common to most TMCFs is the conversion to pasture (Young and León, 2007). Once established, pastures are generally burned annually to promote new growth of grasses and to prevent invasion by shrubs and trees (Asbjornsen and Wilcke, 2008).…”

A Broad Transition from Cloud Forest to Páramo Characterizes an Undisturbed Treeline in Parque Nacional Llanganates, Ecuador

“…Thus, few examples of what could be construed as a natural upper forest boundary now exist. Further, with the differing interpretations of past forest extent and altitudinal vegetation patterns, the degree to which human activity is the overriding cause of an apparently low upper forest limit and the present situation of widespread páramo, remains unclear Young and León, 2007). The nature of the upper forest limit and the associated distribution of woody vegetation where there has been negligible human activity is thus open to question, and there is a clear need to identify reference sites Ramírez et al, 2009).…”

Changing fire regimes in tropical montane cloud forests: a global synthesis

“…This may be promoting the successful recruitment of the early successional Alnus acuminata during extended ®re-free intervals and eventually recruitment of mature MCF species from surrounding steep slopes over longer time periods (Grau et al, in press). In contrast to the situation in Argentina, frequent burning by local people of humid high-elevation grassland areas of the Peruvian Andes during periods of dry weather to promote re-sprouting of pastures (Young and Leo n, 2007) is likely causing a human-driven lowering of the climatically determined treeline between MCF and pa ramo .…”