Tropical Montane Cloud Forests (TMCF) are fundamental ecosystems in terms of biodiversity, water and carbon cycling. In Mexico, TMCF cover 0.9% of the national territory and less than 25% is in protected areas. It is considered one of the most vulnerable ecosystems to the combined effects of land-use, land-cover change and climate change, that negatively impact biodiversity, biomass and carbon fluxes, among other ecosystem functions. Estimating plant biomass and carbon is fundamental for understanding and monitoring such effects. Previous measurements of AGB in Mexican TMCF have been conducted at local scales and show that C stored in the vegetation ranges from 12.7 MgC ha-1 to as high as 413.08 MgC ha-1. Moreover, it is assumed that AGB decreases with elevation and slope angle, probably because of temperature declining with elevation. However, it is unclear if elevation, or geographic location in general, plays a relevant role in AGB allocation in Mexican TMCF. The questions we sought to answer in this project were: How much AGB exists in Mexican TMCF? What is the relationship between AGB and geographic location in this ecosystem? And how has AGB been impacted by LULCC in the last 20 years? For answering these questions, we took a regional approach and used both remote sensing data and ground-based data retrieved from the Mexican National Inventory of Forests and Soil. We estimated AGB in 1483 plots sampled using generic allometric equations. These measurements were compared with normalized difference vegetation index (NDVI) values for the same sampling sites. NDVI was estimated using Landsat images.
Results/Conclusions
Our preliminary results show that there is a total of 142,100,312.6036 Mg of AGB in Mexican TMCF with an average of 79.5160 Mg ha-1, which falls within the range described in the literature for this ecosystem. TMCF shows great vegetation diversity and it is not dominated by a single species. Despite we were expecting to find lower AGB at higher elevations, AGB slightly increases with elevation. This might be due to the abundance of large tree species like firs and pine trees at higher elevations, but further research is needed to assess this trend. Finally, we found a positive relationship between NDVI and AGB in the assessed plots but with an r-square of 0.2, which indicates that this relationship should be refined before upscaling these results.