Relationships among phenology, climate and biomass across subtropical forests in Argentina

Abstract

Abstract:Phenology is a key ecosystem process that reflects climate–vegetation functioning, and is an indicator of global environmental changes. Recently, it has been suggested that land-use change and timber extraction promote differences in forest phenology. We use remote-sensing data to describe regional leaf phenological patterns in combination with field data from 131 plots in old-growth and disturbed forests distributed over subtropical forests of Argentina (54–65°W). We assessed how climate is related to phenological patterns, and analysed how changes in forest structural characteristics such as stock of above-ground biomass relate to the observed phenological signals across the gradient. We found that the first three axes of a principal component analysis explained 85% of the variation in phenological metrics across subtropical forests, ordering plots mainly along indicators of seasonality and productivity. At the regional scale, the relative importance of forest biomass in explaining variation in phenological patterns was about 15%. Climate showed the highest relative importance, with temperature and rainfall explaining Enhanced Vegetation Index metrics related to seasonality and productivity patterns (27% and 47%, respectively). Within forest types, climate explains the major fraction of variation in phenological patterns, suggesting that forest function may be particularly sensitive to climate change. We found that forest biomass contributed to explaining a proportion of leaf phenological variation within three of the five forest types studied, and this may be related to changes in species composition, probably as a result of forest use.

Elevation and latitude drives structure and tree species composition in Andean forests: Results from a large-scale plot network

“…dendrometer bands) in all the permanent forest plots of the Network; 6) detecting situations that are locally important; 7) promoting comparative research for monitoring the impacts of anthropogenic activities across the region, including the dynamics of invasive species (i.e. the case of Ligustrum lucidum in Argentina) [79], or primary/secondary succession as a result of volcanism, forest fires, hurricanes, or land use change (abandonment of agricultural and livestock lands); 8) exploring in detail the association between changes in permanent plots and changes in remotely sensed descriptors of functioning (e.g., NDVI) [80], promoting joint research to develop high resolution models of climate change for the Andean region, and descriptions of land use change [12].…”

Forest biomass stocks and dynamics across the subtropical Andes

“…In comparison with the tropical Andes, in which the reported AGB stocks range from 150 to 250 Mg biomass/ha (e.g., Girardin, Farfan‐Rios, et al., 2014; Peña et al., 2018; Vilanova et al., 2018), we found that subtropical Andean forests had 320 to 370 Mg biomass/ha. Subtropical Andean forests had AGB stocks that were similar as subtropical forests outside the Andes, such as subtropical Atlantic forests in South America (Blundo et al., 2018; Vieira et al., 2008). The abundance of species with high wood specific gravity may contribute to the high AGB stocks of subtropical forests.…”

“…Few studies have evaluated the effects of this historical human practice on forest structure and dynamics at the community level, but the change in species composition may be partially explained by cattle presence (Blundo, Malizia, Blake, & Brown, 2012). Cattle presence does not seem to reduce AGB stock but leads to changes in species composition after decades of forest‐use, for example, increased abundance of some understory species (Malizia, Easdale, & Grau, 2013) or increased abundance of evergreen species (Blundo et al., 2018). Additional studies about the effects of this historical human influence would lead to a better understanding of forest dynamics in the subtropical Andes.…”

“…Plots were established in well‐conserved and mature forests. However, some plots have occasional grazing; this does not seem to reduce forest biomass but may affect species composition after decades of forest use (Blundo et al., 2018). In addition, some plots had low‐intensity selective logging prior to the initial census.…”

“…Andean forests had 320 to 370 Mg biomass/ha. Subtropical Andean forests had AGB stocks that were similar as subtropical forests outside the Andes, such as subtropical Atlantic forests in South America (Blundo et al, 2018;Vieira et al, 2008). The abundance of species with high wood specific gravity may contribute to the high AGB stocks of subtropical forests.…”