Carbon emissions from dryland shifting cultivation: a case study of Mexican tropical dry forest

The article considers the relation of shifting cultivation to deforestation and degradation, and hence its impacts in terms of carbon emissions and sequestration potential. There is a need to understand these relationships better in the context of international policy on Reduced Emissions from Deforestation and Forest Degradation (REDD+). The article reviews the way in which shifting cultivation has been incorporated in global and national estimations of carbon emissions, and assembles the available information on shifting cultivation in Tropical Dry Forests (TDF) in Mexico, where it is widely practiced. It then takes the case of two villages, Tonaya and El Temazcal, which lie within the basin of the River Ayuquila in Jalisco, Mexico. Field data for the typical carbon stocks and fluxes associated with shifting cultivation are compared with stocks and fluxes associated with more intensive agricultural production in the same dry tropical forest area to highlight the carbon sequestration dynamics associated with the shortening and potential lengthening of the fallow cycles. The biomass density in the shifting cultivation system observed can reach levels similar to that of old growth forests, with old fallows (>20 years) having higher carbon stocks than old growth forests. Per Mg of maize produced, the biomass-related emissions from shifting cultivation in the traditional 12 year cycle are about three times those from permanent cultivation. We did not, however, take into account the additional emissions from inputs that result from the use of fertilizers and pesticides in the case of permanent agriculture. Shortening of the fallow cycle, which is occurring in the study area as a result of government subsidies, results in higher remaining stocks of carbon and lower emissions at the landscape level

Pensamiento Novohispano 19

En este número nos encontramos con investigaciones que tienen por objetivo mostrarnos tanto la diversidad de temas estudiados como la riqueza cultural correspondiente al mundo novohispano. En el trabajo titulado "Algunos puntos de Filosofía Novohispana", el autor nos presenta consideraciones correspondientes a los tres siglos de la colonia. Otra aportación relevante, compilada aquí, en el contexto de la conquista y la evangelización, es "El pecado de avaricia en el Tratado sobre los siete pecados mortales, de fray Andrés de Olmos" en donde su autor nos brinda una serte de reflexiones acerca del pecado de avaricia y sus implicaciones. Además, la investigación "Secularización de los Diezmos piadosos en la Nueva España" tiene como finalidad aclarar cuál fue el verdadero sentido de la práctica "obligatoria" de los diezmos y cuál fue la postura de algunos frailes respecto a esa práctica piadosa en el periodo colonial.Universidad Autónoma del Estado de México

Nesting ecology of the Tucuman Amazon (Amazona tucumana) in the cloud forest of Northwestern Argentina

In this chapter we use a parrot species that inhabitsthe cloud forests of northwestern Argentina as a model species to elucidateecological aspects related to habitat use, nesting, and breeding biology of abird species. We synthetize the information gathered for the Tucuman Amazon (Amazona tucumana) during 15 years anddiscuss the implications of this information for the conservation of thespecies and the cloud forest. The Tucuman Amazon is a threatened species,with a small geographic range restricted to the narrow strip of montane foreston the eastern slopes of the Andes (i.e., the Southern Yungas) fromsouth-eastern Bolivia to north-western Argentina. In the SouthernYungas the breeding habitat of Tucuman Amazon is the cloud forest found between1,500?2,200 m asl. Most Tucuman Amazon nests occurred in cavitiesof live trees (95%) of six species, and only 5% were in snags. Compared to theavailability of cavities in different tree species, B. salicifolius, J. australis,and C. lilloi were used significantlymore than expected. Average nest tree DBH was 89.9 ± 26.9 cm, cavities werelocated on average at 14.4 ± 3.9 m above the ground. The estimation of thedensity of available suitable cavities for nesting was 4.6 cavities ha-1(95% CI = 3.1?7.0 cavities ha-1). Clutch-size ranged from one tofive eggs (mean 3.6 ± 1.0, n = 86). The number of fledglings per layingfemale was 2.3 ± 0.8 (n = 86) and differed significantly among years.Primary causes of nest-loss were predation (16%) and parental abandonment(12%). The Tucuman Amazon has high rates of nesting success, large clutches anda large number of fledglings per laying female. These results differ fromtrends observed in other bird species that tend to shift to a slowerlife-history strategy with increased elevation. Nesting and spatialrequirements of Tucuman Amazon could limit management actions intended toincrease the density of nesting pairs. A mean distance among suitable cavitiesof at least 150 m could represent the minimum distance to consider in thespacing of active pairs to avoid exclusion by other pairs especially if nestbox provision is necessary. To ensure theconservation of Tucuman Amazon outside protected areas it is necessary thatforest management guidelines promote the retention of large B. salicifolius, C. lilloi and J. australis)that are selected for nesting by Tucuman Amazon and the latter two have also hightimber values.Fil: Rivera, Luis Osvaldo. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Politi, Natalia. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentin