2.2 Mexico National Forest and Soils Inventory data
Tree height and tree density models were developed using plot level data collected between 2009 and 2014 and obtained from the INFyS database. The sampling design considered a total of 26,220 plots distributed across the Mexican territory during 2009-2014 (Fig 1), however 9.5% of the total plots were categorized as inaccessible sites and another 5.1% were obtained from remote sensing data (CONAFOR, 2017). The number of sampled plots for each forest ecosystem were 2,606 for coniferous forests; 4,111 for coniferous-broadleaf; 3,249 for broadleaf forest; 483 for cloud mountain forest; 3,724 for tropical forest; 1,466 for tropical dry forests; 240 for arid zones; 1,334 for semiarid zones and 157 for mangrove forests. Data available from the Environmental Data Initiative (EDI): https://doi.org/10.6073/pasta/4620375aea631ab6a09cb573c7bf8aff (Barreras et al., 2022) and at the official web page https://snmf.cnf.gob.mx/datos-del-inventario/.
Sampled plots are distributed across all land cover types, ecological stages, and land tenure classes (e.g., private, social, government). Plot distribution is accomplished through systematic, pre-stratified sampling with 5x5, 10x10 and 20x20 km spacing in temperate and tropical forests, dry and semiarid vegetation communities, and arid vegetation strata, respectively. These strata are derived from a forest type map created by the Mexican government (Fig 1, INEGI, 2017), hereafter referred to as the INEGI map. The plot is considered a cluster design with 4 circular subplots, 3 of which are configured in a triangular array around a central subplot. Primary subplots, where trees with a diameter at breast height (dbh, 1.3 m above ground) ≥ 7.5 cm are measured, have a radius of 12.56 meters and are 400 m2in area; spacing between adjacent primary subplot centers is 45.14 m. (CONAFOR 2017). For the purpose of this study, a tree is defined as those greater than or equal to 7.5 cm dbh.