Dataset for: Patterns of understory invasion in exotic, invasive timber stands

Current climate and land cover change threaten global mountaintops with increased spread of invasive species. Long-established plantations of exotic and invasive trees on these mountaintops can alter their surroundings, further increasing invader-facilitated invasion. Identifying the ecological conditions that promote such specific associations can help develop better management interventions. 
The Western Ghats's Shola Sky Islands (>1400m MSL) host vast stretches of exotic and invasive tree plantations that sustain colonisation of other invasive woody, herbaceous and fern species in their understories. Here we analysed vegetation and landscape variables from 232 systematically-placed plots in randomly selected grids using NMDS and Phi Coefficient approaches, to examine patterns of association (positive interactions) between understory invasive species with specific exotic and invasive overstory species. We also conducted GLMM with zero inflation to determine the influence of environ..., The present study was conducted across the high-elevation montane forests of the Nilgiris and Anamalai-Palani hills landscapes (10.12⁰N 77.60⁰E to  11.50⁰N 76.70⁰E). We classified wooded habitats above 1400m MSL into shola forests and plantations following Arasumani et al. 2019. A point lattice of spacing 100 m between the points was overlaid using ArcGIS, and we randomly selected 0.5% of points. Squares of 200mx200m were placed over the lattice, with their centres coinciding with the selected points. We chose 143 random squares and surveyed up to eight circular plots of radius 7m within the grids placed systematically. Since our objective was to assess native regeneration under exotic overstorey, we did not include plots with native trees in their overstory in our analyses. The final numbers of plot samples were 232. Each grid cell consists of up to eight 7m-radius circular plots arranged systematically, and each plot has five circular sub-plots of radius 1m. The circumference at breas..., We used the software R to conduct our analyses. The file is in CSV format and can be opened in Microsoft Excel.Â