Geographic patterns of novel-invasive forest in an Argentinean montane forest

MONTTI LÍA; GRAU H. RICARDO; PIRIZ CARRILLO VERONICA; GUTIERREZ-ARAGONESE JORGELINA; GASPARRI N. IGNACIO; ARAGÓN ROXANA

Workshop; Evolutionary dynamics of tree invasions: drivers, dimensions, and implications for management; 2015

During the early XX century, numerous patches of native forest in NW of Argentina have been cleared for logging, crop production, livestock or other anthropic uses. Many of these sites were subsequently abandoned and forest recovery occurred. However, invasive tree species are a prevalent element on these successional patches, recorded having varied abundance from rare to highly conspicuous. Among them, Ligustrum lucidum (Oleaceae) W.T. Aiton is the most abundant tree species. This is an exotic Chinese species widespread in Argentina and others countries. This novel (invaded) forests present different ecosystem processes species interactions and habitat quality than the native ones. During the workshop we will synthesize our preliminary knowledge about structure and current geographic distribution of this novel invaded forest exploring its relations with climate and topographic conditions (i.e., rainfall, temperature, altitude and slope); and relative importance of potential social drivers (distance to cities, distance to roads and/or past land-uses) than promote its invasion in Argentinean mountain forest.Our studied area corresponds to the Argentinean subtropical mountain forests (Yungas). To describe L. lucidum dominated-patches we recorded forest structure variables and tree diversity on field plots. Using four Landsat TM images corresponding to summer, autumn, winter and spring 2010, we mapped and quantified the real distribution using ENVI v4.1 and Support Vector Machines (SVM), a non-parametric classifier. To produce the potential distribution map of the species in NW of Argentina, we used the maximum entropy method (Maxent) and four environmental variables. To do this, distribution data points were obtained from field collection, herbarium specimen data and bibliographic information.Our preliminary results showed that this species present a potential wide climatic range (between 400-1000 mm annual precipitation and 14-20 °C mean annual temperature). This predicted area covers all native mountain forest distributions in Argentina. In the surveyed area L. lucidum expanded as mono-dominant secondary forests, with high basal area and biomass (in some areas even higher than the native forests). The spatial and spectral resolution of the Landsat TM sensor did not allow us to detect mixed patches of L. lucidum and native trees. So, only mature dominated-patches were detected and described. The patches were widespread in the study area, covering near of 700 ha that represent the 0.22% of the total forest (324,000 ha). The spatial distribution was not homogeneous, and small patches (