Allometric equations for tree species and carbon stocks for forests of northwestern Mexico

Abstract

Allometric equations were developed and applied to forest inventory data to estimate biomass and carbon stocks for temperate species and forests of Durango and Chihuahua and for tropical dry forests of Sinaloa, Mexico. A total of 872 trees were harvested and dissected into their component parts: leaves and branches, boles, and coarse roots. Coarse roots of 40 temperate trees ranging in diameter at breast height (DBH) from 6.0 to 52.9 cm were excavated in their entirety (i.e., >0.5 cm diameter). The species sampled (number of trees) in tropical dry forests (39) were Lysiloma divaricata (Jacq) Macbr. (10), Haematoxylon brasiletto Karst. (10), Cochlospermum vitifolium (Wild.) (5), Ceiba acuminata (S. Watson) Rose (5), Bursera penicillata ( B. inopinnata) (5), and Jatropha angustifolia Mull. Arg. (4) and in temperate forests (833) were Quercus spp. (118) ( Q. rugosa Neé, 15, Quercus sideroxylla Humb. & Bonpl, 51, Quercus spp., 52), Pinus herrerae Martinez 1940 (19), Pinus oocarpa Schiede ex Schlectendal 1838 (31), Pinus engelmannii Carriere 1854 (7), Psudotsuga menziesii (Mirb.) Franco (19), Pinus leiophylla Schiede ex Schlectendal et Chamisso 1831 (27), Pinus teocote Schiede ex Schlectendal et Chamisso (55), Pinus ayacahuite Ehrenb. ex Schltdl. (58), Pinus cooperi Blanco (48), Pinus durangensis Martinez 1942 (385), and Pinus arizonica Engelmann 1879 (66). Allometric equations having only DBH as an independent variable were developed for each component of each species. Since Pinus herrerae, Pinus engelmannii, Pinus oocarpa and Pseudotsuga menziensii had a small number of trees, an individual allometric equation was developed for these species. We used non-linear regression to fit parameters of the typical allometric power equation. The resulting 31 equations (10 species or groups of species, three biomass components; bole, branch and leaves, and total aerial; and the generalized equation for coarse roots) fit the data well and enable the user to predict biomass by component for each of the 10 different groups of species or each of six temperate species. A single allometric equation that incorporates the basic specific gravity for aboveground biomass of all temperate tree species also fit the data well, and this equation provides both the detail and the accuracy supplied by species-specific, plant-part-specific equations. Biomass equations coupled with forest inventory data for temperate (637 circular, 1/10 ha plots) and tropical dry forests (166 20 m × 20 m-quadrats) of northwestern Mexico predict a mean (confidence intervals) of 130 Mg ha −1 (4.2 Mg ha −1) and 73 Mg ha −1 (7.1 Mg ha −1) for total tree and total aboveground biomass, respectively. Large sample sizes and the economic and ecological importance of the species studied make this data set uniquely useful for biomass estimations and for understanding the inherent heterogeneity of tree structure in dynamic tropical and temperate environments of northwestern Mexico.