4 research outputs found
Avocado Cover Expansion in the Monarch Butterfly Biosphere Reserve, Central Mexico
No full textAvocado cultivation has reduced the extent of forest ecosystems in central Mexico, even in natural protected areas such as the Monarch Butterfly Biosphere Reserve (MBBR) where information on the extent and expansion dynamics of avocado cover is scant. This study aimed to identify avocado plantations within the MBBR through photo interpretation for the 2006–2018 period. Change rates of the avocado cover extent were calculated for the northern, central, and southern zones of the MBBR, and topographic attributes such as elevation, soil type, slope, and slope aspect were identified. A total extent of 958 ha is covered by avocado plantations within the MBBR. The southern zone hosted the largest area under avocado cultivation (570 ha), but the northern zone had the highest change rate between 2006 and 2018 (422%). Most avocado orchards have been established mainly in Acrisol soils, south-facing slopes, on steep hillsides, and in elevations between 2050 and 2800 m. The conversion from traditional agricultural lands has been the main mechanism for the establishment of avocado orchards. However, 40 ha under avocado cultivation derived from deforestation, mainly in the central zone. The expansion of avocado plantations could trigger environmental impacts, even threatening the overwintering habitat and the migratory phenomenon of the monarch butterflies
Modification of Fire Regimes Inferred from the Age Structure of Two Conifer Species in a Tropical Montane Forest, Mexico
No full textResearch Highlights: Age structure was used to infer fire regimes in the Monarch Butterfly Biosphere Reserve. Uneven-aged structures in stands dominated and co-dominated by pine and fir species, which are distributed according to an altitudinal gradient, indicated a regime of frequent, low-severity, and low-intensity fires. Background and Objectives: Age structure analyses have been used to infer natural and disrupted fire regimes when field-based descriptions of fires are scarce or unavailable. In montane conifer forests, fire regimes typically vary according to an altitudinal gradient, shaping contrasting tree establishment patterns. In the Monarch Butterfly Biosphere Reserve, Mexico, the altitudinal distribution and fire regimes of sacred fir forests (Abies religiosa), smooth-bark Mexican pine forests (Pinus pseudostrobus), and mixed-conifer forests are poorly documented. The objectives of this study were to determine the altitudinal ranges occupied by mono-dominant and co-dominant stands and to reconstruct tree establishment history to infer historical fire regimes. Materials and Methods: Six altitudinal transects were established along the reserve, each one at elevations from 2400 to 3300 m, with sampling sites at every 150 m of elevation. In each site, increment cores were collected from the base of 25 mature trees. A total of 800 increment cores were collected and cross-dated. Results: P. pseudostrobus is dominant in stands between 2400 and 2850 m, A. religiosa between 3150 and 3300 m, and both species co-dominate between 2850 and 3150 m. The establishment pattern for both species has been continuous, represented by uneven-aged structures, suggesting that tree establishment in smooth-bark Mexican pine forests, mixed-conifer forests, and sacred fir forests, is likely to be associated with frequent, low-severity, and low-intensity fires. Conclusions: These fire regimes suggest, by the one hand, the disruption of natural fire regimes by human activities, limiting the occurrence of high-severity fires; on the other hand, a distinctive feature of these tropical montane forests
Avocado Cover Expansion in the Monarch Butterfly Biosphere Reserve, Central Mexico
No full textAvocado cultivation has reduced the extent of forest ecosystems in central Mexico, even in natural protected areas such as the Monarch Butterfly Biosphere Reserve (MBBR) where information on the extent and expansion dynamics of avocado cover is scant. This study aimed to identify avocado plantations within the MBBR through photo interpretation for the 2006–2018 period. Change rates of the avocado cover extent were calculated for the northern, central, and southern zones of the MBBR, and topographic attributes such as elevation, soil type, slope, and slope aspect were identified. A total extent of 958 ha is covered by avocado plantations within the MBBR. The southern zone hosted the largest area under avocado cultivation (570 ha), but the northern zone had the highest change rate between 2006 and 2018 (422%). Most avocado orchards have been established mainly in Acrisol soils, south-facing slopes, on steep hillsides, and in elevations between 2050 and 2800 m. The conversion from traditional agricultural lands has been the main mechanism for the establishment of avocado orchards. However, 40 ha under avocado cultivation derived from deforestation, mainly in the central zone. The expansion of avocado plantations could trigger environmental impacts, even threatening the overwintering habitat and the migratory phenomenon of the monarch butterflies
