National level biomass database comparison for Mexico in relation to vegetation degradation stages

摘要

Anthropogenic land cover change, e.g. deforestation and forest degradation cause carbon emission. To estimate deforestation and forest degradation, it is important to have reliable data on vegetation and carbon distribution. In Mexico, land cover maps are available at national level in which vegetation is described in four statuses: primary, secondary ("woodland"), secondary ("shrub land"), and secondary ("grass") according to degradation stages. Data on biomass/carbon distribution are also available including: (1) INFyS: national forest and soil inventory; (2) MODIS WHRC: biomass data by Woodshole Research Center for Pantropical region using MODIS data; (3) PALSAR EHRC: biomass data produced by WHRC for Mexico using PALSAR data; (4) MODIS VCF: Vegetation Continuous Fields percent tree cover layer. The aim of this study is 1) to evaluate if degradation stages and biomass are positively correlated, e.g. better preserved vegetation has more biomass, and 2) to evaluate the spatial patterns of the comparison in 1) using geographically weighted regression (GWR), 3) to assess the correlation among the biomass datasets including VCF data. Results show that 1) in general, the biomass value decreases following the degradation stages and the most degraded stage corresponds to the least biomass value. Cuzick value shows that this trend is significant in most of the cases. However, there is serious overlapping in biomass values in various stages. 2) GWR results show that in some regions the four disturbance stages corresponds better with the difference in biomass values. The regions with higher parameter value show better correlation. 3) The biomass data from PALSAR WHRC show higher Spearman values and thus stronger correlation with the biomass data from INFyS. However, due to that biomass data from INfyS and PALSAR WHRC are not independent; we consider the better correlation is from the rest two biomass datasets.