Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of...Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of the soils in permafrost regions in the mid-latitudes and boreal regions, such as that on the westem flank of the Da Xing＇anling （Hinggan） Mountains, northeastern China. This paper gives a detailed analysis on meteorological data series from 2001 to 2010 provided by the Gen＇he Weather Station, which is located in a talik of discontinuous permafrost zone and with sparse meadow on the observation field. It is inferred that snow cover is important for the ground thermal regime in the middle Da Xing＇anling Mountains. Snow cover of 10-cm in thickness and five to six months in duration （generally November to next March） can reduce the heat loss from the ground to the atmosphere by 28%, and by 71% if the snow depth increases to 36 cm. Moreover, the occurrence of snow cover resulted in mean annual ground surface temperatures 4.7-8.2℃ higher than the mean annual air temperatures recorded at the Gen＇he Weather Station, The beginning date for stable snow cover establishment （SE date） and the initial snow depth （SDi） also had a great influences on the ground freezing process. Heavy snowfall before ground surface freeze-up could postpone and retard the freezing process in Gen＇he. As a result, the duration of ground freezing was shortened by at least 20 days and the maximum depth of frost penetration was as much as 90 cm shallower.展开更多
Six new chrysophycean stomatocysts ornamented with reticulum were illustrated based on SEM observation. They were described following the guidelines of the International Statospore Working Group (ISWG). All samples we...Six new chrysophycean stomatocysts ornamented with reticulum were illustrated based on SEM observation. They were described following the guidelines of the International Statospore Working Group (ISWG). All samples were collected from the Great Xing'an Mountains, China. Their taxonomic characteristics and habitats were described to provide new information on the biodiversity of chrysophycean stomatocysts. As is common with many morphotypes, their biological affinities remain unknown.展开更多
Larch caterpillars are widely distributed in the Great Xing’an boreal forests;however,the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood.The aims of this study are to ...Larch caterpillars are widely distributed in the Great Xing’an boreal forests;however,the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood.The aims of this study are to investigate the primary weather conditions that might influence forest defoliation and to identify the most important life stage of the larch caterpillar at which forest defoliation might be mitigated by incorporating more inhibitory influences from climatic factors.The life cycle of the larch caterpillar was partitioned into four stages and multiple linear regression and mixed effect models were combined with a relative weight analysis approach to evaluate the importance and influence of meteorological variables on defoliation dynamics.The results show that warmer temperatures in growing seasons and overwintering periods can increase the defoliation area,while rainy and humid growing seasons decrease the defoliation area.Total precipitation during the early instar larval period had the greatest power to explain the variance in defoliation dynamics and had a very strong inhibitory effect,followed by the accumulative temperatures of the late instar larval period which had a positive impact,and precipitation during the middle instar larval period which had a negative impact.Weather conditions during the early instar larval period had the greatest influence on the area defoliated and accounted for 40%of the explained variance.This study demonstrates that climatic warming and drying will increase the risk of larch caterpillar outbreaks in the Great Xing’an Mountains.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41201066, 41401028, and J0930003/J0109)the State Key Laboratory of Frozen Soils Engineering (No. SKLFSE-ZT-14)
文摘Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of the soils in permafrost regions in the mid-latitudes and boreal regions, such as that on the westem flank of the Da Xing＇anling （Hinggan） Mountains, northeastern China. This paper gives a detailed analysis on meteorological data series from 2001 to 2010 provided by the Gen＇he Weather Station, which is located in a talik of discontinuous permafrost zone and with sparse meadow on the observation field. It is inferred that snow cover is important for the ground thermal regime in the middle Da Xing＇anling Mountains. Snow cover of 10-cm in thickness and five to six months in duration （generally November to next March） can reduce the heat loss from the ground to the atmosphere by 28%, and by 71% if the snow depth increases to 36 cm. Moreover, the occurrence of snow cover resulted in mean annual ground surface temperatures 4.7-8.2℃ higher than the mean annual air temperatures recorded at the Gen＇he Weather Station, The beginning date for stable snow cover establishment （SE date） and the initial snow depth （SDi） also had a great influences on the ground freezing process. Heavy snowfall before ground surface freeze-up could postpone and retard the freezing process in Gen＇he. As a result, the duration of ground freezing was shortened by at least 20 days and the maximum depth of frost penetration was as much as 90 cm shallower.
基金Supported by the National Natural Science Foundation of China (Nos.31070181, 30870162)the Leading Academic Discipline Project of Shanghai Municipal Education Commission (No. J50401)
文摘Six new chrysophycean stomatocysts ornamented with reticulum were illustrated based on SEM observation. They were described following the guidelines of the International Statospore Working Group (ISWG). All samples were collected from the Great Xing'an Mountains, China. Their taxonomic characteristics and habitats were described to provide new information on the biodiversity of chrysophycean stomatocysts. As is common with many morphotypes, their biological affinities remain unknown.
基金The work was supported by the National Key R&D Program of China(2017YFA0604403).
文摘Larch caterpillars are widely distributed in the Great Xing’an boreal forests;however,the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood.The aims of this study are to investigate the primary weather conditions that might influence forest defoliation and to identify the most important life stage of the larch caterpillar at which forest defoliation might be mitigated by incorporating more inhibitory influences from climatic factors.The life cycle of the larch caterpillar was partitioned into four stages and multiple linear regression and mixed effect models were combined with a relative weight analysis approach to evaluate the importance and influence of meteorological variables on defoliation dynamics.The results show that warmer temperatures in growing seasons and overwintering periods can increase the defoliation area,while rainy and humid growing seasons decrease the defoliation area.Total precipitation during the early instar larval period had the greatest power to explain the variance in defoliation dynamics and had a very strong inhibitory effect,followed by the accumulative temperatures of the late instar larval period which had a positive impact,and precipitation during the middle instar larval period which had a negative impact.Weather conditions during the early instar larval period had the greatest influence on the area defoliated and accounted for 40%of the explained variance.This study demonstrates that climatic warming and drying will increase the risk of larch caterpillar outbreaks in the Great Xing’an Mountains.
