Background:The spring phenology and growth strategy of temperate tree species can be strongly linked to their sensitivity to frosts,which deserve more profound investigations under the background of climate warming pa...Background:The spring phenology and growth strategy of temperate tree species can be strongly linked to their sensitivity to frosts,which deserve more profound investigations under the background of climate warming particularly considering the advancement of spring phenology as well as the increase in frequency and intensity of spring cold waves.Methods:Spring phenologies,stem radial growth characteristics,frost sensitivity of leaves and stem hydraulic systems were studied in five diffuse-porous and five ring-porous temperate tree species under a common garden condition.Results:The results showed that the spring leaf phenology of the diffuse-porous species was one to two weeks earlier than that of the ring-porous species.The ring-porous species had significantly higher stem hydraulic conductivity than the diffuse-porous species(1.81 and 0.95 kg·m^(-1)·s^(-1)·MPa^(-1),P<0.05)but were more vulnerable to freeze-thaw induced xylem embolism than the latter.After a simulated freeze-thaw event,the average percentage loss of hydraulic conductivity in the current year shoots increased from 26.0%(native embolism)to 86.7%in the ring-porous species,while it only increased from 21.3%to 38.3%in the diffuse-porous species.The spring phenology was clearly correlated with vulnerability to freeze-thaw induced embolism,with the more vulnerable ring-porous species exhibited substantially delayed phenology to reduce risks of catastrophic hydraulic dysfunction during spring frosts.Nevertheless,ring-porous species can offset the postponed onset of growth and gained even higher annual growth due to significantly higher hydraulic efficiency and leaf gas exchange rates.Conclusions:Contrasts between ring-porous and diffuse-porous species in resistance to freeze-thaw induced embolism suggest that they face different selective pressures from early spring frosts,which may at least be partially responsible for their divergence in spring phenology and growth strategy and can potentially lead to different responses to climate regime shifts.展开更多
We analyzed 17 seed sources(seed stands)ofPinus wallichiana for variations present in cone and seed characters,scattered over natural distribution in north-west Himalayan states(Uttarakhand and Himachal Pradesh)of Ind...We analyzed 17 seed sources(seed stands)ofPinus wallichiana for variations present in cone and seed characters,scattered over natural distribution in north-west Himalayan states(Uttarakhand and Himachal Pradesh)of India.The significant variations were observed in cone weight,cone length,cone width,seed length,seed width,seed weight,seed germination,radicle length,and plumule length among different seed sources of the species.Significant positive correlation between seed weight,cone weight and cone width showed that seed weight in the species depend more on the cone size.Seed germination was also positively correlated with seed weight,cone weight and radicle length in the study.The estimates of variability with regard to genetic parameters for seed weight,seed germination,cone length,cone width,cone weight showed wide range of variation in the study.Seed weight showed high heritability values coupled with maximum genetic gain.Traits with such values indicate presence of good amount of heritable additive components and are under strong genetic control.The findings of the study revealed that seed sources expressed both phenotypic and genotypic differences in the seed and cone traits which might be due to the differences in genetic make up of various seed sources and environmental factors i,e.genotypic and environmental interaction,The study suggests that the seed weight should be given the top priority for the further improvement of this species.展开更多
Investigations were made to determine the nature and extent of variations present for 10 morphological characters of cone,seed and seedlings of 17 plus trees（PTs）of Pinus kesiya growing in eastern Himalayas（Meghala...Investigations were made to determine the nature and extent of variations present for 10 morphological characters of cone,seed and seedlings of 17 plus trees（PTs）of Pinus kesiya growing in eastern Himalayas（Meghalaya state） of India.The significant variations has been observed in cone weight,cone length,cone diameter,seed length,seed diameter,seed weight,number of seeds per cone,seed germination,seedling height and seedling collar diameter among different PTs of the species.Significant positive correlation（p ／ 0.01） between seed weight,cone length and cone diameter showed that seed weight in P.kesiya depend more on the cone size.Seed germination is found positively correlated（p ／ 0.01） with seed weight,seed diameter,cone size and number of seeds per cone in the study.Among geographical factors,latitude and altitude are found positively correlated（p ／ 0.05） with cone weight and seed diameter,respectively.The genetic parameters for seed,cone and seedlings of PTs of P.kesiya also showed a wide range of variability in terms of variance,coefficient of variability,broad sense heritability,genetic advance and genetic gain.Seed weight,seeds per cone and seedling diameter showed high heritability values（[75） coupled with maximum genetic gain.Traits with such values indicate the presence of good amount of heritable additive components and are under strong genetic control.The findings of the study revealed that PTs expressed both phenotypic and genotypic differences in the seed,cone and seedling characters,which may be attributed to the differences in genetic makeup of various PTs and environmental factors i.e.genotypic and environmental interaction.The presence of high variability in P.kesiya PTs for different characters provide further opportunities to improve the population in subsequent generations so as to establish this species as an important timber tree to be grown on less fertile and degraded soils in its distributional ranges.展开更多
The variations in seed and pod traits,genetic superiority and genetic divergence were evaluated for a Clonal Seed Orchard(CSO)of Dalbergia sissoo Roxb.at Bithmera,India consisting of 20 clones from different agro-clim...The variations in seed and pod traits,genetic superiority and genetic divergence were evaluated for a Clonal Seed Orchard(CSO)of Dalbergia sissoo Roxb.at Bithmera,India consisting of 20 clones from different agro-climatic conditions of four northern states(Uttar Pradesh,Uttarakhand,Haryana and Rajasthan).The seeds and pods of various clones in the orchard exhibited significant variability in size,weight and other characters.Significant positive correlations were observed between seed length and seed width(p〈0.05),seed length and sccd thickness(p〈0.01),seed length and seed weight(p〈0.01),seed thickness and seed weight(p〈0.01),seed length and germination value(p〈0.05).The ge-netic parameters for seed and pod traits also showed a wide range of variations in the orchard.Heritability values were found to be over 50 percent for most of~e seed and pod traits.Seed weight,seed length and seed thickness showed high heritability values coupled with maximum genetic gain for these characters.Ward's minimum variance dendrogram of clones of D.sissoo showed three distinct clusters;cluster I was the largest with 12 better clones whereas cluster 2 and 3 consisting of seven moderate clones and one poor clone,respectively.Mean cluster values showed sufficient variation among the clusters for seed weight,germina-tion value and seed length.The possible hybridization between best clones of cluster I to the disease resistant clone of cluster 2(resistant against deadly Gandoderma lucidum root rot disease of D.sissoo)is also suggested for further breeding programmes of the species.The deploy-ment of clone 194(better performed and disease resistant)is also rec-ommended in future plantation programmes of D.sissoo in northern India.展开更多
Minquartia guianensis Aubl.is a slow-growing species with several uses.In the juvenile state,it is well-adapted to low light conditions of the forest understory.However,it is still unknown how climate variability affe...Minquartia guianensis Aubl.is a slow-growing species with several uses.In the juvenile state,it is well-adapted to low light conditions of the forest understory.However,it is still unknown how climate variability affects transpiration of this species,particularly under drought stress.In this study,we aimed to assess the effect of climatic variability on sap flow rates(SFR).SFR and radial growth were measured in six trees(14-50 cm diameter)in 2015 and 2016.Climate(precipitation,irradiance,relative humidity and temperature)and soil water content(SWC)data were also collected.SFR tended to increase in the dry season,with a negative relationship between SFR and SWC and precipitation(p<0.001),while there was a positive association between radial growth and monthly precipitation(p=0.004).Irradiance and temperature were the environmental factors more closely correlated with SFR during daytime(p<0.001),whereas relative humidity and vapor pressure deficit were the most important factors at night(p<0.001).Although negative SFR were sometimes recorded at night,the mean nocturnal sap flow was positive and across trees the nighttime sap flow accounted for 12.5%of the total daily sap flow.Increased transpiration during the dry season suggests that the root system of Minquartia was able to extract water from deep soil layers.These results widen our understanding of the ecophysiology of Amazonian trees under drought and provide further insight into the potential effect of the forecasted decline in precipitation in the Amazon region.展开更多
The influence of seasonal variation, indole-3-butyric acid （IBA） and type of cuttings was examined on induction and growth of adventitious roots in Bambusa nutans Wall. and Bambusa tulda Roxb. Singlenode culm and cu...The influence of seasonal variation, indole-3-butyric acid （IBA） and type of cuttings was examined on induction and growth of adventitious roots in Bambusa nutans Wall. and Bambusa tulda Roxb. Singlenode culm and culm-branch cuttings from the mature culms were provided with immersion treatment for 24 h of either water （control） or 2 mM IBA in four different seasons, i.e., spring （mid February）, summer （mid May）, rainy （mid July）, and winter （mid November） and maintained for two months in the mist chamber at the relative humidity of （70±5）% and the tenlperature of （30±2）℃. In B. nutans, adventitious rooting occttrred in both types of cuttings in all the seasons with the best rooting in the summer season i.e., May （88% in culm cuttings） and the least in winter. On the contrary, adventitious rooting was recorded only in culm cuttings in spring and summer season in B. tulda. IBA treatment significantly enhanced rooting, root number and root length; registering 14 to 17 times improvement over control in the best rooting season. Three factor- interactions （season × cutting type × IBA treatment） were significant for rooting in B. nutans and all characteristics, except sprouting in B, tulda. Thus, single-node culm and culm-branch cuttings in B. nutans and culm cuttings in B. tulda treated with 2 mM IBA during spring （February） to summer （May） season are recommended for their clonal multiplication.展开更多
Black phosphorus (BP) as an uprising two-dimensional material exhibits attractive potential in the field of electrocatalysis due to the inherent advantages of high carrier mobility and abundant lone pair electrons.How...Black phosphorus (BP) as an uprising two-dimensional material exhibits attractive potential in the field of electrocatalysis due to the inherent advantages of high carrier mobility and abundant lone pair electrons.However,the exposed active electrons compel BP to be deactivated by oxidative degradation.Herein,the electronic signature of acceptor-donor heterointerfacial interactions between BP and Co_(3)O_(4)is realized via wet ball milling.The preferential migration of active electrons from BP to Co_(3)O_(4)is achieved at the heterointerface since the Fermi level of BP is higher than that of Co_(3)O_(4).Such relative energetic consideration promotes reasonable oxygen electrocatalytic active sites.Moreover,it significantly suppresses the oxidative degradation of BP.Consequently,the resulting Co_(3)O_(4)/BP heterojunction possesses superior oxygen bifunctional electrocatalytic activity than its parent catalysts.Most importantly,this work promotes an efficient route towards BP-based multifunctional catalysts.展开更多
Wood plays a major role in land ecosystems and in human activity. Better understanding the genetic basis and evolutionary implication of wood variability are thus key issues with both ecological and economical implica...Wood plays a major role in land ecosystems and in human activity. Better understanding the genetic basis and evolutionary implication of wood variability are thus key issues with both ecological and economical implications. The present paper addresses the question of the extending and the nature of natural selection on wood related genes in Eucalyptus urophylla, a tropical tree species with key economical importance. We conducted a genetic study on an E. urophylla population from Timor Island using a set of 17 SSR characterized on a main sample of 43 individuals and six candidate genes sequenced on a subset of 18 individuals. The candidate genes include three cellulose synthase genes (EuCesA1, EuCesA2 and EuCesA3), and three genes involved in lignin synthesis (EuCAD2, EuC4H1 and EuC4H2). Based on SSR data, the investigated population appeared to have no structure and have undergone past population expansion. Accounting for this demographic history, we were able to draw neutral expectation for polymorphism distribution on candidate genes and to determine their potential selective status. We hence identified two gene portions exhibiting unexpected polymorphism pattern, consistent with natural selection imprint.展开更多
Long-term high resolution climate proxies are essential for understanding climate variability particularly,in regions such as the western Himalayas of northern Pakistan,where few long-term climate records are availabl...Long-term high resolution climate proxies are essential for understanding climate variability particularly,in regions such as the western Himalayas of northern Pakistan,where few long-term climate records are available.Using standard dendrochronological methods,an 1132-year(882 to 2013 C.E.)tree-ring chronology of Juniperus excelsa M.Bieb was established from the western Himalayas,northern Pakistan(WHNP).Tree growth was negatively and significantly(r=-0.65)correlated with the growing season(June-July)mean temperature,and positively and weakly(r=0.22)associated with precipitation.This inverse relationship of tree radial growth with temperature and positive association with precipitation demonstrated that forest growth is sensitive to high temperature related drought.Utilizing a reliable STD chronology and robust reconstruction model,a 928-year(1086 to 2013 C.E.)mean temperature reconstruction was developed for the WHNP using the substantial negative correlation between the summer temperature and standard tree ring-width chronology.According to statistical validation,the reconstruction accounted for 41.6% of the climatic variation for the period of 1956-2013 C.E.instrumental period.Individual extreme-warm periods occurred in 1093 C.E.(29.42℃)and extreme cold periods in 1088 C.E.(26.99℃)observed during the past 928 years.The reconstruction's multi-taper method(MTM)spectral analysis reveals significant(p<0.05)2-3-year and 63.8-year cycles.Since the 2-3-year cycle occurred within the range of ENSO variation,which indicates that ENSO had an impact on the regional temperature in our studied area.展开更多
基金supported by the National Natural Science Foundation of China(Nos.31901284,31870593,31722013,32192431)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(No.ZDBS-LY-DQC019)National Key R&D Program of China(No.2020YFA0608100)。
文摘Background:The spring phenology and growth strategy of temperate tree species can be strongly linked to their sensitivity to frosts,which deserve more profound investigations under the background of climate warming particularly considering the advancement of spring phenology as well as the increase in frequency and intensity of spring cold waves.Methods:Spring phenologies,stem radial growth characteristics,frost sensitivity of leaves and stem hydraulic systems were studied in five diffuse-porous and five ring-porous temperate tree species under a common garden condition.Results:The results showed that the spring leaf phenology of the diffuse-porous species was one to two weeks earlier than that of the ring-porous species.The ring-porous species had significantly higher stem hydraulic conductivity than the diffuse-porous species(1.81 and 0.95 kg·m^(-1)·s^(-1)·MPa^(-1),P<0.05)but were more vulnerable to freeze-thaw induced xylem embolism than the latter.After a simulated freeze-thaw event,the average percentage loss of hydraulic conductivity in the current year shoots increased from 26.0%(native embolism)to 86.7%in the ring-porous species,while it only increased from 21.3%to 38.3%in the diffuse-porous species.The spring phenology was clearly correlated with vulnerability to freeze-thaw induced embolism,with the more vulnerable ring-porous species exhibited substantially delayed phenology to reduce risks of catastrophic hydraulic dysfunction during spring frosts.Nevertheless,ring-porous species can offset the postponed onset of growth and gained even higher annual growth due to significantly higher hydraulic efficiency and leaf gas exchange rates.Conclusions:Contrasts between ring-porous and diffuse-porous species in resistance to freeze-thaw induced embolism suggest that they face different selective pressures from early spring frosts,which may at least be partially responsible for their divergence in spring phenology and growth strategy and can potentially lead to different responses to climate regime shifts.
基金financially supported by USDA,Washington for conducting this study under the project"Studies on Himalayan Pines"(1996-2006)
文摘We analyzed 17 seed sources(seed stands)ofPinus wallichiana for variations present in cone and seed characters,scattered over natural distribution in north-west Himalayan states(Uttarakhand and Himachal Pradesh)of India.The significant variations were observed in cone weight,cone length,cone width,seed length,seed width,seed weight,seed germination,radicle length,and plumule length among different seed sources of the species.Significant positive correlation between seed weight,cone weight and cone width showed that seed weight in the species depend more on the cone size.Seed germination was also positively correlated with seed weight,cone weight and radicle length in the study.The estimates of variability with regard to genetic parameters for seed weight,seed germination,cone length,cone width,cone weight showed wide range of variation in the study.Seed weight showed high heritability values coupled with maximum genetic gain.Traits with such values indicate presence of good amount of heritable additive components and are under strong genetic control.The findings of the study revealed that seed sources expressed both phenotypic and genotypic differences in the seed and cone traits which might be due to the differences in genetic make up of various seed sources and environmental factors i,e.genotypic and environmental interaction,The study suggests that the seed weight should be given the top priority for the further improvement of this species.
基金funded by Indian Council of Forestry and Education,Dehradun
文摘Investigations were made to determine the nature and extent of variations present for 10 morphological characters of cone,seed and seedlings of 17 plus trees（PTs）of Pinus kesiya growing in eastern Himalayas（Meghalaya state） of India.The significant variations has been observed in cone weight,cone length,cone diameter,seed length,seed diameter,seed weight,number of seeds per cone,seed germination,seedling height and seedling collar diameter among different PTs of the species.Significant positive correlation（p ／ 0.01） between seed weight,cone length and cone diameter showed that seed weight in P.kesiya depend more on the cone size.Seed germination is found positively correlated（p ／ 0.01） with seed weight,seed diameter,cone size and number of seeds per cone in the study.Among geographical factors,latitude and altitude are found positively correlated（p ／ 0.05） with cone weight and seed diameter,respectively.The genetic parameters for seed,cone and seedlings of PTs of P.kesiya also showed a wide range of variability in terms of variance,coefficient of variability,broad sense heritability,genetic advance and genetic gain.Seed weight,seeds per cone and seedling diameter showed high heritability values（[75） coupled with maximum genetic gain.Traits with such values indicate the presence of good amount of heritable additive components and are under strong genetic control.The findings of the study revealed that PTs expressed both phenotypic and genotypic differences in the seed,cone and seedling characters,which may be attributed to the differences in genetic makeup of various PTs and environmental factors i.e.genotypic and environmental interaction.The presence of high variability in P.kesiya PTs for different characters provide further opportunities to improve the population in subsequent generations so as to establish this species as an important timber tree to be grown on less fertile and degraded soils in its distributional ranges.
基金supported by Indian Council of Forestry and Education,Dehradun
文摘The variations in seed and pod traits,genetic superiority and genetic divergence were evaluated for a Clonal Seed Orchard(CSO)of Dalbergia sissoo Roxb.at Bithmera,India consisting of 20 clones from different agro-climatic conditions of four northern states(Uttar Pradesh,Uttarakhand,Haryana and Rajasthan).The seeds and pods of various clones in the orchard exhibited significant variability in size,weight and other characters.Significant positive correlations were observed between seed length and seed width(p〈0.05),seed length and sccd thickness(p〈0.01),seed length and seed weight(p〈0.01),seed thickness and seed weight(p〈0.01),seed length and germination value(p〈0.05).The ge-netic parameters for seed and pod traits also showed a wide range of variations in the orchard.Heritability values were found to be over 50 percent for most of~e seed and pod traits.Seed weight,seed length and seed thickness showed high heritability values coupled with maximum genetic gain for these characters.Ward's minimum variance dendrogram of clones of D.sissoo showed three distinct clusters;cluster I was the largest with 12 better clones whereas cluster 2 and 3 consisting of seven moderate clones and one poor clone,respectively.Mean cluster values showed sufficient variation among the clusters for seed weight,germina-tion value and seed length.The possible hybridization between best clones of cluster I to the disease resistant clone of cluster 2(resistant against deadly Gandoderma lucidum root rot disease of D.sissoo)is also suggested for further breeding programmes of the species.The deploy-ment of clone 194(better performed and disease resistant)is also rec-ommended in future plantation programmes of D.sissoo in northern India.
基金supported by research project(MCTI/INPA:PRJ-15.120)。
文摘Minquartia guianensis Aubl.is a slow-growing species with several uses.In the juvenile state,it is well-adapted to low light conditions of the forest understory.However,it is still unknown how climate variability affects transpiration of this species,particularly under drought stress.In this study,we aimed to assess the effect of climatic variability on sap flow rates(SFR).SFR and radial growth were measured in six trees(14-50 cm diameter)in 2015 and 2016.Climate(precipitation,irradiance,relative humidity and temperature)and soil water content(SWC)data were also collected.SFR tended to increase in the dry season,with a negative relationship between SFR and SWC and precipitation(p<0.001),while there was a positive association between radial growth and monthly precipitation(p=0.004).Irradiance and temperature were the environmental factors more closely correlated with SFR during daytime(p<0.001),whereas relative humidity and vapor pressure deficit were the most important factors at night(p<0.001).Although negative SFR were sometimes recorded at night,the mean nocturnal sap flow was positive and across trees the nighttime sap flow accounted for 12.5%of the total daily sap flow.Increased transpiration during the dry season suggests that the root system of Minquartia was able to extract water from deep soil layers.These results widen our understanding of the ecophysiology of Amazonian trees under drought and provide further insight into the potential effect of the forecasted decline in precipitation in the Amazon region.
基金funded by Department of Biotechnology, Government of India, New Delhi(Sanction No.102/IFD/San 2632/2003-2004)
文摘The influence of seasonal variation, indole-3-butyric acid （IBA） and type of cuttings was examined on induction and growth of adventitious roots in Bambusa nutans Wall. and Bambusa tulda Roxb. Singlenode culm and culm-branch cuttings from the mature culms were provided with immersion treatment for 24 h of either water （control） or 2 mM IBA in four different seasons, i.e., spring （mid February）, summer （mid May）, rainy （mid July）, and winter （mid November） and maintained for two months in the mist chamber at the relative humidity of （70±5）% and the tenlperature of （30±2）℃. In B. nutans, adventitious rooting occttrred in both types of cuttings in all the seasons with the best rooting in the summer season i.e., May （88% in culm cuttings） and the least in winter. On the contrary, adventitious rooting was recorded only in culm cuttings in spring and summer season in B. tulda. IBA treatment significantly enhanced rooting, root number and root length; registering 14 to 17 times improvement over control in the best rooting season. Three factor- interactions （season × cutting type × IBA treatment） were significant for rooting in B. nutans and all characteristics, except sprouting in B, tulda. Thus, single-node culm and culm-branch cuttings in B. nutans and culm cuttings in B. tulda treated with 2 mM IBA during spring （February） to summer （May） season are recommended for their clonal multiplication.
基金supported by the National Natural Science Foundation of China (No. 62004143)the Natural Science Foundation of Hubei Province (No. 2021CFB133)+5 种基金the Central Government Guided Local Science and Technology Development Special Fund Project (No. 2020ZYYD033)the Opening Fund of Key Laboratory of Rare Mineral,Ministry of Natural Resources (No. KLRM-KF 202005)the Innovation Project of Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education (No. LCX2021003)the Open Research Fund of Key Laboratory of Material Chemistry for Energy Conversion and Storage (HUST), Ministry of Education (No. 2021JYBKF05)the Opening Fund of Key Laboratory for Green Chemical Process of Ministry of Education of Wuhan Institute of Technology (No. GCP202101)the 13th Graduate Education Innovation Fund of Wuhan Institute of Technology。
文摘Black phosphorus (BP) as an uprising two-dimensional material exhibits attractive potential in the field of electrocatalysis due to the inherent advantages of high carrier mobility and abundant lone pair electrons.However,the exposed active electrons compel BP to be deactivated by oxidative degradation.Herein,the electronic signature of acceptor-donor heterointerfacial interactions between BP and Co_(3)O_(4)is realized via wet ball milling.The preferential migration of active electrons from BP to Co_(3)O_(4)is achieved at the heterointerface since the Fermi level of BP is higher than that of Co_(3)O_(4).Such relative energetic consideration promotes reasonable oxygen electrocatalytic active sites.Moreover,it significantly suppresses the oxidative degradation of BP.Consequently,the resulting Co_(3)O_(4)/BP heterojunction possesses superior oxygen bifunctional electrocatalytic activity than its parent catalysts.Most importantly,this work promotes an efficient route towards BP-based multifunctional catalysts.
文摘Wood plays a major role in land ecosystems and in human activity. Better understanding the genetic basis and evolutionary implication of wood variability are thus key issues with both ecological and economical implications. The present paper addresses the question of the extending and the nature of natural selection on wood related genes in Eucalyptus urophylla, a tropical tree species with key economical importance. We conducted a genetic study on an E. urophylla population from Timor Island using a set of 17 SSR characterized on a main sample of 43 individuals and six candidate genes sequenced on a subset of 18 individuals. The candidate genes include three cellulose synthase genes (EuCesA1, EuCesA2 and EuCesA3), and three genes involved in lignin synthesis (EuCAD2, EuC4H1 and EuC4H2). Based on SSR data, the investigated population appeared to have no structure and have undergone past population expansion. Accounting for this demographic history, we were able to draw neutral expectation for polymorphism distribution on candidate genes and to determine their potential selective status. We hence identified two gene portions exhibiting unexpected polymorphism pattern, consistent with natural selection imprint.
基金supported by the National Natural Science Foundation of China(Grant No.42007407)the Sino-German mobility program(M-0393)the China-Pakistan Joint Research Center on Earth Sciences(No.131551KYSB20200022).
文摘Long-term high resolution climate proxies are essential for understanding climate variability particularly,in regions such as the western Himalayas of northern Pakistan,where few long-term climate records are available.Using standard dendrochronological methods,an 1132-year(882 to 2013 C.E.)tree-ring chronology of Juniperus excelsa M.Bieb was established from the western Himalayas,northern Pakistan(WHNP).Tree growth was negatively and significantly(r=-0.65)correlated with the growing season(June-July)mean temperature,and positively and weakly(r=0.22)associated with precipitation.This inverse relationship of tree radial growth with temperature and positive association with precipitation demonstrated that forest growth is sensitive to high temperature related drought.Utilizing a reliable STD chronology and robust reconstruction model,a 928-year(1086 to 2013 C.E.)mean temperature reconstruction was developed for the WHNP using the substantial negative correlation between the summer temperature and standard tree ring-width chronology.According to statistical validation,the reconstruction accounted for 41.6% of the climatic variation for the period of 1956-2013 C.E.instrumental period.Individual extreme-warm periods occurred in 1093 C.E.(29.42℃)and extreme cold periods in 1088 C.E.(26.99℃)observed during the past 928 years.The reconstruction's multi-taper method(MTM)spectral analysis reveals significant(p<0.05)2-3-year and 63.8-year cycles.Since the 2-3-year cycle occurred within the range of ENSO variation,which indicates that ENSO had an impact on the regional temperature in our studied area.
