Changes in forest structure and composition in a pine-oak forest in Jaumave, Tamaulipas, Mexico

Abstract

The pine-oak forest is distributed from the north to the south of Mexico, it has high susceptibility to degradation due to the increasein forest fires, pests, and other extremenatural events, which makes the need to conserve and sustainably use its resources relevant.Even when these forests are in a wide ecological niche (300 to 2500 m altitude), their populations are affected by the interaction ofextreme natural events and anthropogenic disturbances, causing changes in their structure and species composition. The floristiccomposition and forest structure of a pine-oak forest in Jaumave, Tamaulipas, were analyzed over 15 years, with three alternatesamplings in this period. A systematic samplingwas conducted in thirty-two circular plots of 1,000 m². In each plot, all trees with adiameter> 7.5 m were identified and measured. Basalarea (BA), density and species richnesswere calculated. In addition, the type offorest and disturbance type were identified. 3,567 individuals of sixteen distinct species (six familiesand six genera) were registered;the Quercus genus was the most abundant, representing 60% of the arboreal individuals. Three types of forests were defined: pine,oak, and pine-oak, based on the dominance of the basal area. Significant differences were found between measurement dates andfamilies(Pinaceae and Fagaceae, p <0.01). The BA increased with respect to the first and last measurement, increasing the BA of theoaks, while in pines it decreased. The differences were explained by the possible increase in pests, associated with prolongeddroughts registered between the years 2004 and 2010; causing a decrease in AB. Additionally, BA was affected by silviculturaltreatments applied in the control of debarker beetle (Dendroctonus sp.)