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
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 a reference for the high mountain environment in the intertropical regions.展开更多
High Mountain Asia(HMA)has the largest volume of glaciers outside the polar region and protects approximately 800 million people in the downstream basins against water stress.HMA is facing rapid glacier melting and su...High Mountain Asia(HMA)has the largest volume of glaciers outside the polar region and protects approximately 800 million people in the downstream basins against water stress.HMA is facing rapid glacier melting and substantial glacier mass loss,reaching the peak of runoff('peak water')in the following decades.In the present study,the timing of glacier peak water was calculated using a projected glacier runoffdataset forced by twelve General Circulation Models under the Shared Socioeconomic Pathway(SSP)scenarios.The dominant factors that influence the timing of peak water,such as glacial area,elevation,aspect,slope,latitude and debris thickness,were investigated using partial correlation and stratified analysis.Our results demonstrated that,for the entire HMA,glacier peak water was predicted to occur in 2028,2052,2057,and 2059 under SSP126,SSP260,SSP370,and SSP585,respectively.For each subregion,Hengduan Shan is projected to reach the earliest peak water in HMA in 2024,2025,2021,and 2024 under SSP126,SSP260,SSP370,and SSP585,respectively.In West Tianshan,glacier peak water is projected to occur in 2027,2036,2050,and 2050 under SSP126,SSP260,SSP370,and SSP585,respectively.In the West Kunlun,glacier peak water will occur in 2070 under SSP126 and 2080 under SSP245 but will not appear until 2100 under SSP370 and SSP585.Glacier elevation and latitude are highly correlated with peak water timing for the entire HMA,with the partial correlation coefficients being 0.48 and 0.47,respectively(P<0.01).Additionally,earlier glacier peak water normally occurs in glaciers with a small area or steeper slope.Debris can also influence the timing of glacier peak water with a thinner debris cover(<5 cm)leading to delayed peak water.Our findings indicated that glacier elevation and latitude are highly correlated with glacier peak water timing for the entire HMA.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.
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 a reference for the high mountain environment in the intertropical regions.
基金supported by the Tianshan Talent Program of Xin-jiang,China(2022TSYCCX0042)National Natural Science Foundation of China(42071046,42130512)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0720203)the Water System Evolution and Risk Assessment in Arid Regions for Original Innovation Projectof Institute,and the Youth Innovation Promotion Association of the Chinese Academyof Sciences.
文摘High Mountain Asia(HMA)has the largest volume of glaciers outside the polar region and protects approximately 800 million people in the downstream basins against water stress.HMA is facing rapid glacier melting and substantial glacier mass loss,reaching the peak of runoff('peak water')in the following decades.In the present study,the timing of glacier peak water was calculated using a projected glacier runoffdataset forced by twelve General Circulation Models under the Shared Socioeconomic Pathway(SSP)scenarios.The dominant factors that influence the timing of peak water,such as glacial area,elevation,aspect,slope,latitude and debris thickness,were investigated using partial correlation and stratified analysis.Our results demonstrated that,for the entire HMA,glacier peak water was predicted to occur in 2028,2052,2057,and 2059 under SSP126,SSP260,SSP370,and SSP585,respectively.For each subregion,Hengduan Shan is projected to reach the earliest peak water in HMA in 2024,2025,2021,and 2024 under SSP126,SSP260,SSP370,and SSP585,respectively.In West Tianshan,glacier peak water is projected to occur in 2027,2036,2050,and 2050 under SSP126,SSP260,SSP370,and SSP585,respectively.In the West Kunlun,glacier peak water will occur in 2070 under SSP126 and 2080 under SSP245 but will not appear until 2100 under SSP370 and SSP585.Glacier elevation and latitude are highly correlated with peak water timing for the entire HMA,with the partial correlation coefficients being 0.48 and 0.47,respectively(P<0.01).Additionally,earlier glacier peak water normally occurs in glaciers with a small area or steeper slope.Debris can also influence the timing of glacier peak water with a thinner debris cover(<5 cm)leading to delayed peak water.Our findings indicated that glacier elevation and latitude are highly correlated with glacier peak water timing for the entire HMA.
