3.4 Mapping Mexico forests tree height and tree density
The models were used to generate a spatially continuous national map of total tree height (Fig 4) and the total number of trees (Fig 5), both at a 1000-m resolution, along with their associated uncertainties. At the forest type level, maximum pixel values of tree height exist in coniferous, coniferous-broadleaf forests and cloud mountain forests (~36 m, 30 m and 21 m, respectively). These types of forest ecosystems constitute Mexico’s mountain chains Sierra Madre Oriental and Sierra Madre Occidental. Moreover, the smallest tree heights were predicted in arid and semi-arid zones, having a mean of ~4 m. The model had the highest uncertainty when predicting tree height in arid zones (60-80%), the latter could be related to the limited sample size we had for that specific forest type (Fig 4b). Lower uncertainty was observed for tropical forest, tropical dry forest, coniferous and broadleaf forest.
Tropical forests had the maximum pixel values of tree density (~1370 trees/ha), followed by tropical dry forest (1006 trees/ha), coniferous forest (988 trees/ha) and coniferous-broadleaf forest (931 trees/ha) (Fig 5a). Uncertainty in predictions of tree density was relatively low across all forest types (Fig 5b). Similar to what we observed for tree height, the highest uncertainty estimates were found for arid and semi-arid ecosystems but were of a higher magnitude (>80%).