High-mountain forests (>3500 masl) are the main supplier of environmental services to Mexico City and its metropolitan area. Taking as a study case the Nevado de Toluca National Park, this article focuses on the co...High-mountain forests (>3500 masl) are the main supplier of environmental services to Mexico City and its metropolitan area. Taking as a study case the Nevado de Toluca National Park, this article focuses on the considerable reduction on the density of its forest cover, characterised by disturbances in the structure and dynamics of Pinus hartwegii. This specie is located towards the upper limits of the altitudinal gradient (3500 - 4100 masl) constituting the only pine species in the world capable to be established in those extreme environmental conditions. The information was collected through the implementation of 30 Sampling Plots (SP) of 20 × 50 mts (1000 m2) in three forest density categories: dense, semi-dense and fragmented. For each forest category, all trees ≥2.5 cm DBH were measured in 10 SPs. The measurement variables were DBH, total and commercial height, forest health and forest extraction. The results show the abundance of dense, semi-dense and fragmented forest (336, 202 and 150 trees/Ha-1), with extraction percentages of 11%, 20% and 33% respectively. The horizontal structure distribution shows the shape of an inverted J for the three conditions. However, the phytosanitary conditions of the semi-dense forests (83% infested trees) and fragmented (63% infested trees), do not guaranties the survival of the adult trees, implying an intensification of the fragmentation process for the next decade;given the reduction of the regeneration patterns due to the lack of healthy tree breeding.展开更多
Globally,mountains are often characterized as fragile and hazardous terrains,with vast areas covered by the cryosphere.The livelihoods of communities in the Hindu Kush Himalayan region are closely linked with the cryo...Globally,mountains are often characterized as fragile and hazardous terrains,with vast areas covered by the cryosphere.The livelihoods of communities in the Hindu Kush Himalayan region are closely linked with the cryosphere.But over the past few decades,communities in the region have experienced multiple changes,including those driven by climat e change,with direct and immediate impacts on their lives and livelihoods.In this study,we explore linkages between the cryosphere and high-mountain livelihoods using a social-ecological system approach.It examines how the complex social-ecological system in villages in Langtang Valley,Nepal,has evolved in response to both cryospheric and socioeconomic changes.The local communities perceive gradual but significant changes in the cryospheric system,such as receding and thinning glaciers,changing snowfall patterns,changes in temperature and precipitation patterns,and a growing incidence of cryosphere-related hazards,such as avalanches and landslides.Communities in the Langtang Valley are also facing a number of socioeconomic changes,resulting in changing aspirations,particularly among the youth.The growing disconnection between society and the surrounding cryosphere,with direct impacts on the transfer and growth of local knowledge systems,are discussed.These simultaneous changes in the cryosphere and the socioeconomic domain have also resulted in a homogenization of livelihood sources,with tourism emerging as the dominant source of livelihood.This has resulted in a dependence of the local population on food imported from outside the valley.A growing dependence on tourism for livelihoods,dependence on imports for food and other basic needs,and the lack of a risk reduction strategy might pose great risks for local lives and livelihoods in the long run.Interventions pertaining to diversifying livelihoods,harmonizing social capital,and hazard risk assessment are essential for strengthening linkages between cryosphere and the socioeconomic system.展开更多
The state of the cryosphere in tropical regions is of great importance because the temperature around the glaciers, permafrost and snow cover always fluctuates near the melting point. These thermal conditions and thei...The state of the cryosphere in tropical regions is of great importance because the temperature around the glaciers, permafrost and snow cover always fluctuates near the melting point. These thermal conditions and their high sensitivity to climate change cause the accelerated disappearance of these elements;therefore, it is important to know the climatic factors that regulate them, as well as the physical characteristics of each cryospheric element. Unlike glaciers, permafrost and snow cover have not been widely studied. In recent decades, the study of the glacial and periglacial environment has been carried out in intertropical mountains. However, despite the altitude of their relief and the frequent occurrence of snowfall in tropical high mountains, the conditions that determine such events have been barely analyzed;and in the case of Mexico, the volume of snowfall and its thickness have not been quantified either, as well as their corresponding duration. Consequently, this work is aimed to analyze the temperature and precipitation conditions that determine the snowfall at the higher part of the Nevado de Toluca volcano;at the same time, the conditions of the cryotic climate and their possible implication on the surface are studied. The analysis of data from 1965 to 2016, using frequency statistics, allowed to realize that snowfall occurs with low intensity, its accumulation being less than 10 cm thick and 10 mm of snow water equivalent, which causes the snowpack to stay only a few weeks on average. At the same time, it was determined that there is a significant increase in the number of freeze-thaw cycles. Therefore, due to the climate conditions and their influence on the mountain surface, it is probable that the bedrock is subject to a greater gelifraction dynamics, and the unconsolidated soil surface increases;the combination of the above could cause a greater geomorphological dynamic over time, particularly due to debris flows, and by water and wind erosion of the surface. This work is intended to serve as 展开更多
文摘High-mountain forests (>3500 masl) are the main supplier of environmental services to Mexico City and its metropolitan area. Taking as a study case the Nevado de Toluca National Park, this article focuses on the considerable reduction on the density of its forest cover, characterised by disturbances in the structure and dynamics of Pinus hartwegii. This specie is located towards the upper limits of the altitudinal gradient (3500 - 4100 masl) constituting the only pine species in the world capable to be established in those extreme environmental conditions. The information was collected through the implementation of 30 Sampling Plots (SP) of 20 × 50 mts (1000 m2) in three forest density categories: dense, semi-dense and fragmented. For each forest category, all trees ≥2.5 cm DBH were measured in 10 SPs. The measurement variables were DBH, total and commercial height, forest health and forest extraction. The results show the abundance of dense, semi-dense and fragmented forest (336, 202 and 150 trees/Ha-1), with extraction percentages of 11%, 20% and 33% respectively. The horizontal structure distribution shows the shape of an inverted J for the three conditions. However, the phytosanitary conditions of the semi-dense forests (83% infested trees) and fragmented (63% infested trees), do not guaranties the survival of the adult trees, implying an intensification of the fragmentation process for the next decade;given the reduction of the regeneration patterns due to the lack of healthy tree breeding.
文摘Globally,mountains are often characterized as fragile and hazardous terrains,with vast areas covered by the cryosphere.The livelihoods of communities in the Hindu Kush Himalayan region are closely linked with the cryosphere.But over the past few decades,communities in the region have experienced multiple changes,including those driven by climat e change,with direct and immediate impacts on their lives and livelihoods.In this study,we explore linkages between the cryosphere and high-mountain livelihoods using a social-ecological system approach.It examines how the complex social-ecological system in villages in Langtang Valley,Nepal,has evolved in response to both cryospheric and socioeconomic changes.The local communities perceive gradual but significant changes in the cryospheric system,such as receding and thinning glaciers,changing snowfall patterns,changes in temperature and precipitation patterns,and a growing incidence of cryosphere-related hazards,such as avalanches and landslides.Communities in the Langtang Valley are also facing a number of socioeconomic changes,resulting in changing aspirations,particularly among the youth.The growing disconnection between society and the surrounding cryosphere,with direct impacts on the transfer and growth of local knowledge systems,are discussed.These simultaneous changes in the cryosphere and the socioeconomic domain have also resulted in a homogenization of livelihood sources,with tourism emerging as the dominant source of livelihood.This has resulted in a dependence of the local population on food imported from outside the valley.A growing dependence on tourism for livelihoods,dependence on imports for food and other basic needs,and the lack of a risk reduction strategy might pose great risks for local lives and livelihoods in the long run.Interventions pertaining to diversifying livelihoods,harmonizing social capital,and hazard risk assessment are essential for strengthening linkages between cryosphere and the socioeconomic system.
基金the National Council for Science and Technology CONACYT,México for the postdoctoral fellowship。
文摘The state of the cryosphere in tropical regions is of great importance because the temperature around the glaciers, permafrost and snow cover always fluctuates near the melting point. These thermal conditions and their high sensitivity to climate change cause the accelerated disappearance of these elements;therefore, it is important to know the climatic factors that regulate them, as well as the physical characteristics of each cryospheric element. Unlike glaciers, permafrost and snow cover have not been widely studied. In recent decades, the study of the glacial and periglacial environment has been carried out in intertropical mountains. However, despite the altitude of their relief and the frequent occurrence of snowfall in tropical high mountains, the conditions that determine such events have been barely analyzed;and in the case of Mexico, the volume of snowfall and its thickness have not been quantified either, as well as their corresponding duration. Consequently, this work is aimed to analyze the temperature and precipitation conditions that determine the snowfall at the higher part of the Nevado de Toluca volcano;at the same time, the conditions of the cryotic climate and their possible implication on the surface are studied. The analysis of data from 1965 to 2016, using frequency statistics, allowed to realize that snowfall occurs with low intensity, its accumulation being less than 10 cm thick and 10 mm of snow water equivalent, which causes the snowpack to stay only a few weeks on average. At the same time, it was determined that there is a significant increase in the number of freeze-thaw cycles. Therefore, due to the climate conditions and their influence on the mountain surface, it is probable that the bedrock is subject to a greater gelifraction dynamics, and the unconsolidated soil surface increases;the combination of the above could cause a greater geomorphological dynamic over time, particularly due to debris flows, and by water and wind erosion of the surface. This work is intended to serve as
