Search

Bioengineering is a technical option which uses selected biological elements to retain soil and rehabilitate areas with gullies. With this aim, bioengineering practices were implemented to recover areas affected by gully erosion in a micro-watershed located in the Mixteca, an important region in the Mexican state of Oaxaca. The restoration plan was to rehabilitate an old stone check dam located in the lower part of the watershed and the establishment of live barriers with Erytrina americana Miller, upstream in the main gullies contributing to the drainage system. To assess the morphometry of the micro-watershed, a digital elevation model was generated by a drone. To assess the efficiency of rehabilitation practices, the volume of sediments retained by the structures was quantified by topographic surveys. Results show that the live barriers combined with the check dam retained as sediments weight 1,304.99 Mg. As the micro-watershed area is 37.06 hectares, without bioengineering structures, the specific degradation would have reached 35.27 Mg ha−1y−1. Thus, sediments retention obtained with the bioengineering system has proven to be efficient in decreasing waterflow speed and initiating the rehabilitation of gullied lands. [ABSTRACT FROM AUTHOR]

• -Anthropogenic disturbance drives the long-term population decline of a dominant dry forest tree. • -Higher rainfall appears to have a bigger positive impact on population growth in a disturbed than a protected site. • -The interactive effects between rainfall and forest status (disturbed or protected) differentially affect the vital rates of A. adstringens. The interactive effects of anthropogenic disturbance and climatic variables can shape the demography of plant populations, but they remain poorly understood especially for long-lived species like tropical trees. Understanding these interactions is critical for designing forest management strategies in the face of both growing anthropogenic pressures and climate change. We explored the effects of habitat disturbance and interannual variation in rainfall on the population dynamics of Amphipterygium adstringens (Anacardiaceae), an ecologically dominant tree species endemic to the tropical deciduous forests of Mexico, that is heavily harvested for its medicinal bark. Specifically, we compared A. adstringens vital rates and long-term population growth rates of unharvested populations in a disturbed versus a protected tropical deciduous forest site; and explored the effects of inter-annual variation in annual rainfall on A. adstringens by comparing vital rates and population growth rates across three years with differing levels of rainfall. We established four plots in each of the two sites and monitored survival, growth and reproduction of 251 individuals over three years. We found that anthropogenic disturbance and rainfall differentially affected the vital rates of A. adstringens. Survival did not differ across sites or years. Growth tended to be lower and fecundity higher, in the protected site, but these effects varied across years and as a function of plant size. No seedlings were found in the disturbed site over the three years study period. Integral projection models showed that projected population growth rates (λ values) in the protected site were higher and much less variable over time than those of the disturbed site. Lambda values in the disturbed site were <1, indicating long-term population decline. In both sites, the rainiest year showed the highest population growth rate but the increase in λ was much higher in the disturbed site than in the protected site. These findings suggest that the population dynamics of A. adstringens are heavily affected by habitat disturbance forest management regime and that the impacts of interannual variability in rainfall or other environmental conditions may be exacerbated in disturbed conditions. The persistence of A. adstringens populations over time will require the exclusion of livestock as well as the implementation of silvicultural practices that will lead to seedling establishment and survival. This study provides key data for the management and conservation of A. adstringens, a highly valued medicinal species. [ABSTRACT FROM AUTHOR]

Herein, we describe the chemical composition of sapwood, heartwood and bark of Quercus laurina and Q. crassifolia , from Ixtlán de Juarez, Oaxaca, Mexico. We also report on the fuel characteristics of wood, bark and charcoal for these species. There was no significant difference in lignin (24.9–25.5%), α-cellulose (47.6–47.9%), and hemicellulose (22.4–23.2%) contents between Q. crassifolia and Q. laurina wood, while the ash content, hot water solubility, and total extractive content were higher in Q. crassifolia wood. The contribution of lignin, α-cellulose, hemicelluloses, suberin, and total extractives in barks, were 25.2–39.6%, 12.2–49.6%, 18.6–23.6%, 1.99–26.6%, and 12.7–31.7%, respectively. Bark had 4–8 times as much ash as the corresponding wood. The wood high heating value (HHV) of both oaks (19.3–19.4 MJ kg −1 ), was higher compared to other temperate hardwoods; the charcoal HHV varied from 32.0 to 33.3 MJ kg −1 . Because of its high polysaccharide (69.7–70.8%) and low extractive (5.29–8.88%) and ash (0.30–0.95%) contents, wood of both species is deemed as suitable for the production of cellulosic pulp, while the content of suberin in the outer bark (20.1–26.6%), suggests its potential as biopolymers source. The fuel properties of wood and charcoal from both species indicate their aptitude as solid fuel. [ABSTRACT FROM AUTHOR]