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Exotic plant invasion is one of the major causes of species extinction. In many contexts, mountainous forests are the last refuge for native species. There are several inventory studies conducted in mountainous and tropical forests in Indonesia. However, there are no studies yet on the factors that explain the abundance and richness of surveyed naturalized alien species. This study investigated whether the number of individuals and abundance-weighted species richness (AWR) of naturalized alien plant species in the hiking-trail of Mount Gede-Pangrango National Park (MGPNP) forest area correlated with leaf traits (specific leaf area (SLA) and leaf thickness) and environmental factors (elevation, slope, and normalized difference vegetation index (NDVI)). We showed that leaf thickness and habitat elevation explained the AWR variations of naturalized alien species. We did not detect any important effect of leaf traits and environmental factors on the number of individuals per exotic species per plot. The influence of leaf thickness and habitat elevation indicates the important role of both biotic and abiotic factors on exotic species to develop a high species richness and become an invasive species in the tropical mountain forest ecosystem. [ABSTRACT FROM AUTHOR]

One of the threats faced with Cibodas Biosphere Reserve area is the changes of forest area into plantation. Various efforts were made by Gunung Gede Pangrango National Park (TNGP) management to restore the area to its original function. One of the efforts is planting trees in the ex-plantation area that has been abandoned by the farmers. In 2016, Cibodas Botanics Garden was collaborated with TNGP to plant native trees species that had potency of high carbon sequestration. Six hundreds seedlings from 12 native trees species were planted ie, Altingia excelsa Noronha, Castanopsis argentea (Blume) A.DC., Castanopsis javanica (Blume) A.DC., Castanopsis tunggurut (Blume) A.DC, Dacrycarpus imbricatus (Blume) de Laub., Euonymus indicus B. Heyne ex Wall., Lithocarpus indutus (Blume) Rehder, Magnolia blumei Prantl, Persea rimosa Zoll. ex Meisn., Syzygium acuminatissimum (Blume) DC., Sloanea sigun (Blume) K. Schum., and Schima wallichii Choisy. The observations of evaluation done by January, February and July 2016. Parameters were observed are plant height, root collar diameter and crown width. Then, the data were analyzed by RGR (Relative Growth Rate) and RPI (Relative Performance Index). The results of observation during six months after planting shown that the average survival rate was 60.56%, with the largest survival rates were Altingia excelsa and Castanopsis javanica (80%). Castanopsis tunggurut was the lowest survival rate than the other plants (33,33%). The best growth rate is shown by Schima wallichii. In this case, obstructed plant growth is caused by the high density of weeds and shrubs so that seedlings are less exposed to sunlight and nutritional deficiencies, and also the damage that caused by humans, especially for Castanopsis tunggurut and Sloanea sigun.