The Himalayas are characterized by a broad gradient of bioclimatic zones along their elevation.However,less is known how forest growth responds to climatic change along elevation.In this study,four standard treering w...The Himalayas are characterized by a broad gradient of bioclimatic zones along their elevation.However,less is known how forest growth responds to climatic change along elevation.In this study,four standard treering width chronologies of Himalayan fir(Abies spectabilis)were developed,spanning 142–649 years along an elevation gradient of 3076–3900 m a.s.l.Principal component analysis classified the four chronologies into two groups;the ones at lower elevations(M1 and M2)and higher elevations(M3 and M4)show two distinct growth trends.Radial growth is limited by summer(June–August)precipitation at M3,and by precipitation during spring(March–May)and summer at M4.It is limited by spring temperatures and winter precipitation(December–February)at M1.Tree-ring width chronologies also significantly correlate with winter and spring Palmer Drought Severity Index(PDSI)at M1,and with summer PDSI at M3 and M4.Thus,Himalayan fir growth at high elevations is mainly limited by moisture stress rather than by low temperatures.Furthermore,the occurrence of missing rings coincides with dry periods,providing additional evidence for moisture limitation of Himalayan fir growth.展开更多
The steep North to South (N-S) gradient and complex topography markssignificant variations in the spatial and temporal patterns of climatic variationsurrounding within a few distances in the Nepal Himalayas. Hence,to ...The steep North to South (N-S) gradient and complex topography markssignificant variations in the spatial and temporal patterns of climatic variationsurrounding within a few distances in the Nepal Himalayas. Hence,to validate climatic linkages between the stations under two distinct topographicconditions, the study examines the observational climatic data from106m a.s.l. and 1801m a.s.l., as a representative station from a plain andhilly area. Different statistical tools including Pearson correlation analysisand a best-fit regression model were applied to analyze climate data. Theanalysis of 13129 daily average temperature records and 13147 daily totalprecipitation records showed that the variation in their sum and average ofdaily, five days, ten days, and monthly values between the stations in thedifferent elevations marked significantly.Despite these variations, temperaturerecords are measured to be consistent in different altitudes and stronglycorrelated. The precipitation data showed a comparatively weaker correlation.The coefficients (0.85-1.6) with R2>0.50 in the regression models forthe lower elevation and higher elevation station in the mid-mountain regionexcept for the monsoon season. It indicated a similar fluctuation of temperaturebetween these two stations in the respective area. The strong degreeof association and the change of climatic parameters in different rangeand elevations indicate the possibilities of using climatic data from Terai torepresent the Mid-mountain region of central Nepal.展开更多
Climate change is expected to threaten the developing countries the most. Nepal is considered one of the five countries most vulnerable to climate change in the world. The mountainous area such as Rasuwa District in N...Climate change is expected to threaten the developing countries the most. Nepal is considered one of the five countries most vulnerable to climate change in the world. The mountainous area such as Rasuwa District in Nepal is more vulnerable due to complex topography, human activity(tourism), and climate change. In this context, we carried out this study to assess the climate change and its impact on agriculture production as well as people’s perceptions on the impact of climate change. The long-term(1980–2014) observed climate data(temperature and precipitation) and field-based survey data on people’s perceptions were analyzed. Mann-Kendall trend test and Sen’s slope estimation were used to analyze the temperature and precipitation trends. Furthermore, key informant interviews(KIIs) and focal group discussions(FGDs) were conducted to understand people’s perceptions of the impact of climate change on agricultural production. Further, ERA5 and Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation of Water Resources(APHRODITE) datasets were used to compare the in situ climate data. The maximum temperature and total precipitation in summer monsoon(June–September) were found increasing significantly at rates of 0.07℃/a and 19.89 mm/a, respectively. But the minimum winter temperature and winter precipitation were found decrease by 0.05℃/a and 4.89 mm/a, respectively. Moreover, a large number of respondents reported a decrease in millet and wheat productions while an increase in potato production over the considered time duration(1990–2014). It is noteworthy that the respondents from the mid-elevation regions perceived an increasing trend in crop production compared to those from the low elevation regions. In recent years, people living in the high elevation regions of Rasuwa District have started to shift their cropping calendar to increase agricultural production. This study will provide useful information for policymakers in formulating adaptation strategies in mountainous areas of Nepal.展开更多
Large tropical volcanic eruptions can cause short-term global cooling. However, little is known whether large tropical volcanic eruptions, like the one in Tambora/Indonesia in 1815, cause regional hydroclimatic anomal...Large tropical volcanic eruptions can cause short-term global cooling. However, little is known whether large tropical volcanic eruptions, like the one in Tambora/Indonesia in 1815, cause regional hydroclimatic anomalies. Using a tree-ring network of precisely dated Himalayan birch in the central Himalayas, we reconstructed variations in the regional pre-monsoon precipitation back to 1650 CE. A superposed epoch analysis indicates that the pre-monsoon regional droughts are associated with large tropical volcanic eruptions, appearing to have a strong influence on hydroclimatic conditions in the central Himalayas. In fact, the most severe drought since 1650 CE occurred after the Tambora eruption. These results suggest that dry conditions prior to monsoon in the central Himalayas were associated with explosive tropical volcanism. Prolonged La Ni?a events also correspond with persistent pre-monsoon droughts in the central Himalayas. Our results provide evidence that large tropical volcanic eruptions most likely induced severe droughts prior to monsoon in the central Himalayas.展开更多
基金We thank the Kathmandu Center for Research and Education,CAS-TU,for help during the fieldwork。
文摘The Himalayas are characterized by a broad gradient of bioclimatic zones along their elevation.However,less is known how forest growth responds to climatic change along elevation.In this study,four standard treering width chronologies of Himalayan fir(Abies spectabilis)were developed,spanning 142–649 years along an elevation gradient of 3076–3900 m a.s.l.Principal component analysis classified the four chronologies into two groups;the ones at lower elevations(M1 and M2)and higher elevations(M3 and M4)show two distinct growth trends.Radial growth is limited by summer(June–August)precipitation at M3,and by precipitation during spring(March–May)and summer at M4.It is limited by spring temperatures and winter precipitation(December–February)at M1.Tree-ring width chronologies also significantly correlate with winter and spring Palmer Drought Severity Index(PDSI)at M1,and with summer PDSI at M3 and M4.Thus,Himalayan fir growth at high elevations is mainly limited by moisture stress rather than by low temperatures.Furthermore,the occurrence of missing rings coincides with dry periods,providing additional evidence for moisture limitation of Himalayan fir growth.
文摘The steep North to South (N-S) gradient and complex topography markssignificant variations in the spatial and temporal patterns of climatic variationsurrounding within a few distances in the Nepal Himalayas. Hence,to validate climatic linkages between the stations under two distinct topographicconditions, the study examines the observational climatic data from106m a.s.l. and 1801m a.s.l., as a representative station from a plain andhilly area. Different statistical tools including Pearson correlation analysisand a best-fit regression model were applied to analyze climate data. Theanalysis of 13129 daily average temperature records and 13147 daily totalprecipitation records showed that the variation in their sum and average ofdaily, five days, ten days, and monthly values between the stations in thedifferent elevations marked significantly.Despite these variations, temperaturerecords are measured to be consistent in different altitudes and stronglycorrelated. The precipitation data showed a comparatively weaker correlation.The coefficients (0.85-1.6) with R2>0.50 in the regression models forthe lower elevation and higher elevation station in the mid-mountain regionexcept for the monsoon season. It indicated a similar fluctuation of temperaturebetween these two stations in the respective area. The strong degreeof association and the change of climatic parameters in different rangeand elevations indicate the possibilities of using climatic data from Terai torepresent the Mid-mountain region of central Nepal.
文摘Climate change is expected to threaten the developing countries the most. Nepal is considered one of the five countries most vulnerable to climate change in the world. The mountainous area such as Rasuwa District in Nepal is more vulnerable due to complex topography, human activity(tourism), and climate change. In this context, we carried out this study to assess the climate change and its impact on agriculture production as well as people’s perceptions on the impact of climate change. The long-term(1980–2014) observed climate data(temperature and precipitation) and field-based survey data on people’s perceptions were analyzed. Mann-Kendall trend test and Sen’s slope estimation were used to analyze the temperature and precipitation trends. Furthermore, key informant interviews(KIIs) and focal group discussions(FGDs) were conducted to understand people’s perceptions of the impact of climate change on agricultural production. Further, ERA5 and Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation of Water Resources(APHRODITE) datasets were used to compare the in situ climate data. The maximum temperature and total precipitation in summer monsoon(June–September) were found increasing significantly at rates of 0.07℃/a and 19.89 mm/a, respectively. But the minimum winter temperature and winter precipitation were found decrease by 0.05℃/a and 4.89 mm/a, respectively. Moreover, a large number of respondents reported a decrease in millet and wheat productions while an increase in potato production over the considered time duration(1990–2014). It is noteworthy that the respondents from the mid-elevation regions perceived an increasing trend in crop production compared to those from the low elevation regions. In recent years, people living in the high elevation regions of Rasuwa District have started to shift their cropping calendar to increase agricultural production. This study will provide useful information for policymakers in formulating adaptation strategies in mountainous areas of Nepal.
基金supported by the National Natural Science Foundation of China (41661144040)the Strategic Priority Research Program of Chinese Academy of Sciences (XDA20050101, XDA2006040103)+1 种基金Youth Innovation Promotion Association of Chinese Academy of Sciences, and the Open Research Fund of Key Laboratory of Tibetan Environmental Changes and Land Surface Processes, Chinese Academy of Sciencessupported by the Chinese Academy of Sciences President’s International Fellowship Initiative (2018PC0040)
文摘Large tropical volcanic eruptions can cause short-term global cooling. However, little is known whether large tropical volcanic eruptions, like the one in Tambora/Indonesia in 1815, cause regional hydroclimatic anomalies. Using a tree-ring network of precisely dated Himalayan birch in the central Himalayas, we reconstructed variations in the regional pre-monsoon precipitation back to 1650 CE. A superposed epoch analysis indicates that the pre-monsoon regional droughts are associated with large tropical volcanic eruptions, appearing to have a strong influence on hydroclimatic conditions in the central Himalayas. In fact, the most severe drought since 1650 CE occurred after the Tambora eruption. These results suggest that dry conditions prior to monsoon in the central Himalayas were associated with explosive tropical volcanism. Prolonged La Ni?a events also correspond with persistent pre-monsoon droughts in the central Himalayas. Our results provide evidence that large tropical volcanic eruptions most likely induced severe droughts prior to monsoon in the central Himalayas.
