Variations in vegetation are closely related to climate change, but understanding of their characteristics and causes remains limited. As a typical semi-humid and semi-arid cold plateau region, it is important to unde...Variations in vegetation are closely related to climate change, but understanding of their characteristics and causes remains limited. As a typical semi-humid and semi-arid cold plateau region, it is important to understand the knowledge of long term Normalized Difference Vegetation Index(NDVI) variations and find the potential causes in the source region of the Yangtze River. Based on four tree-ring width chronologies, the regional mean NDVI for July and August spanning the period 1665–2013 was reconstructed using a regression model, and it explained 43.9% of the total variance during the period 1981–2013. In decadal, the reconstructed NDVI showed eight growth stages(1754–1764, 1766–1783, 1794–1811, 1828–1838, 1843–1855, 1862–1873, 1897–1909, and 1932–1945)and four degradation stages(1679–1698, 1726–1753, 1910–1923, and 1988–2000). And based on wavelet analysis, significant cycles of2–3 yr and 3–8 yr were identified. In additional, there was a significant positive correlation between the NDVI and the Palmer Drought Severity Index(PDSI) during the past 349 yr, and they were mainly in phase. However, according to the results of correlation analysis between different grades of drought/wet and NDVI, there was significant asymmetry in extreme drought years and extreme wet years. In extreme drought years, NDVI was positively correlated with PDSI, and in extreme wet years they were negatively correlated.展开更多
Tree rings provide long-term records of tree growth and climate changes,which makes them ideal benchmarks for forest modeling.Tree-ring information has greatly improved the reliability of 3-PG,which is one of the most...Tree rings provide long-term records of tree growth and climate changes,which makes them ideal benchmarks for forest modeling.Tree-ring information has greatly improved the reliability of 3-PG,which is one of the most commonly used process-based forest growth models.Here,we strengthen 3-PG's ability to simulate tree-ring width and stable carbon isotopes(δ^(13)C)by enhancing its descriptions of tree physiology.The major upgrade was adding a carbon storage pool for tree-ring formation using stored carbohydrates.We also incorporated previous modifications(replacing the age modifier with a height modifier)of 3-PG and tested their efficacy in improving tree-ring simulations.We ran the model based on two grand fir(Abies grandis)stands.The updated model greatly improved the simulations for both tree-ring widths andδ^(13)C.The results represent one of the best tree-ringδ^(13)C simulations,which accurately captured the amplitude in annual variations ofδ^(13)C.The correlations(R^(2))between simulations and observations reached 0.50 and 0.73 at two stands,respectively.The new model also greatly improved the simulations of raw tree-ring widths and detrended ring-width index(RWI).Because of better descriptions of tree physiology and more accurate simulations of tree rings than the previous model version,the updated 3-PG should provide more reliable simulations than previous 3-PG versions when tree-ring information is used as a benchmark in future studies.展开更多
The Gabes aquifer system,located in southeastern Tunisia,is a crucial resource for supporting local socio-economic activities.Due to its dual porosity structure,is particularly vulnerable to pollution.This study aims ...The Gabes aquifer system,located in southeastern Tunisia,is a crucial resource for supporting local socio-economic activities.Due to its dual porosity structure,is particularly vulnerable to pollution.This study aims to develop a hybrid model that combines the Fracture Aquifer Index(FAI)with the conventional GOD(Groundwater occurrence,Overall lithology,Depth to water table)method,to assess groundwater vulnerability in fractured aquifer.To develop the hybrid model,the classical GOD method was integrated with FAI to produce a single composite index.Each parameter within both GOD and FAI was scored,and a final index was calculated to delineate vulnerable areas.The results show that the study area can be classified into four vulnerability levels:Very low,low,moderate,and high,indicating that approximately 8%of the area exhibits very low vulnerability,29%has low vulnerability,25%falls into the moderate category,and 38%is considered highly vulnerable.The FAI-GOD model further incorporates fracture network characteristics.This refinement reduces the classification to three vulnerability classes:Low,medium,and high.The outcomes demonstrate that 46%of the area is highly vulnerable due to a dense concentration of fractures,while 17%represents an intermediate zone characterized by either shallow or deeper fractures.In contrast,37%corresponds to areas with lightly fractured rock,where the impact on vulnerability is minimal.Multivariate statistical analysis was employed using Principal Components Analysis(PCA)and Hierarchical Cluster Analysis(HCA)on 24 samples across six variables.The first three components account for over 76%of the total variance,reinforcing the significance of fracture dynamics in classifying vulnerability levels.The FAI-GOD model removes the very-low-vulnerability class and expands the spatial extent of low-and high-vulnerability zones,reflecting the dominant influence of fracture networks on aquifer sensitivity.While both indices use a five-class system,FAI-GOD redistributes vulnerability by eliminating very-low-vulnerability areas and amplifying low/high categories,highlighting the critical role of fractures.A strong correlation(R2=0.94)between the GOD and FAI-GOD indices,demonstrated through second-order polynomial regression,confirms the robustness of the FAI-GOD model in accurately predicting vulnerability to pollution.This model provides a useful framework for assessing the vulnerability of complex aquifers and serves as a decision-making tool for groundwater managers in similar areas.展开更多
BACKGROUND Timely and accurate evaluation of mental disorders in adolescents using appropriate mental health literacy assessment tools is essential for improving their mental health literacy levels.AIM To develop an e...BACKGROUND Timely and accurate evaluation of mental disorders in adolescents using appropriate mental health literacy assessment tools is essential for improving their mental health literacy levels.AIM To develop an evaluation index system for the mental health literacy of adolescent patients with mental disorders,providing a scientific,comprehensive,and reliable tool for the monitoring and intervention of mental health literacy of such patients.METHODS From December 2022 to June 2023,the evaluation index system for mental health literacy of adolescents with mental disorders was developed through literature reviews,semi-structured interviews,expert letter consultations,and the analytic hierarchy process.Based on this index system,a self-assessment questionnaire was compiled and administered to 305 adolescents with mental disorders to test the reliability and validity of the index system.RESULTS The final evaluation index system for mental health literacy of adolescents with mental disorders included 4 first-level indicators,10 second-level indicators,and 52 third-level indicators.The overall Cronbach’sαcoefficient of the index system was 0.957,with a partial reliability of 0.826 and a content validity index of 0.975.The cumulative variance contribution rate of 10 common factors was 66.491%.The correlation coefficients between each dimension and the total questionnaire ranged from 0.672 to 0.724,while the correlation coefficients in each dimension ranged from 0.389 to 0.705.CONCLUSION The evaluation index system for mental health literacy of adolescents with mental disorders,developed in this study,demonstrated notable reliability and validity,making it a valuable tool for evaluating mental health literacy in this population.展开更多
Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divide...Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divides the order of a group G.In this paper,some characterizations of G being p-solvable or p-supersolvable were obtained by analyzing the normal index of certain subgroups of G.These results can be viewed as local version of recent results in the literature.展开更多
Surface polaritons,as surface electromagnetic waves propagating along the surface of a medium,have played a crucial role in enhancing photonic spin Hall effect(PSHE)and developing highly sensitive refractive index(RI)...Surface polaritons,as surface electromagnetic waves propagating along the surface of a medium,have played a crucial role in enhancing photonic spin Hall effect(PSHE)and developing highly sensitive refractive index(RI)sensors.Among them,the traditional surface plasmon polariton(SPP)based on noble metals limits its application beyond the near-infrared(IR)regime due to the large negative permittivity and optical losses.In this contribution,we theoretically proposed a highly sensitive PSHE sensor with the structure of Ge prism-SiC-Si:InAs-sensing medium,by taking advantage of the hybrid surface plasmon phonon polariton(SPPhP)in mid-IR regime.Here,heavily Si-doped InAs(Si:InAs)and SiC excite the SPP and surface phonon polariton(SPhP),and the hybrid SPPhP is realized in this system.More importantly,the designed PSHE sensor based on this SPPhP mechanism achieves the multi-stage RI measurements from 1.00025-1.00225 to 1.70025-1.70225,and the maximal intensity sensitivity and angle sensitivity can be up to 9.4×10^(4)μm/RIU and245°/RIU,respectively.These findings provide a new pathway for the enhancement of PSHE in mid-IR regime,and offer new opportunities to develop highly sensitive RI sensors in multi-scenario applications,such as harmful gas monitoring and biosensing.展开更多
Droughts are the most frequent natural disaster in regions at the margins of the East Asian summer monsoon(EASM),which pose threats to agriculture,the economy,and human lives.However,the limitations of only approximat...Droughts are the most frequent natural disaster in regions at the margins of the East Asian summer monsoon(EASM),which pose threats to agriculture,the economy,and human lives.However,the limitations of only approximately 60 years of meteorological observations hamper our understanding of the characteristics and mechanisms of local hydroclimate.Trees growing in the marginal region of the EASM are usually sensitive to moisture variations and have played important roles in past hydroclimatic reconstructions.Here,a 303-year tree-ring-width chronology of Pinus tabulaeformis from Mt.Lama,which is located in the junction of the Liaoning Province and Inner Mongolia,China,was used to reconstruct the May-August Palmer drought severity index(PDSI)in the marginal region of the EASM.The transfer function explains 48.0%(or 47.2%after adjusting for the loss of the degrees of freedom)of the variance over the calibration period from 1946 to 2012.A spatial correlation analysis demonstrates that our PDSI reconstruction can represent the drought variability on the northernmost margin of the EASM.The winter Asian polar vortex area index showed a delayed impact on the summer EASM precipitation in the following year.展开更多
Tree-ring width(RW),density,elemental com-position,and stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)are widely used as proxies to assess climate change,ecology,and environmental pollution;however,a specific pret...Tree-ring width(RW),density,elemental com-position,and stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)are widely used as proxies to assess climate change,ecology,and environmental pollution;however,a specific pretreat-ment has been needed for each proxy.Here,we developed a method by which each proxy can be measured in the same sample.First,the sample is polished for ring width meas-urement.After obtaining the ring width data,the sample is cut to form a 1-mm-thick wood plate.The sample is then mounted in a vertical sample holder,and gradually scanned by an X-ray beam.Simultaneously,the count rates of the fluorescent photons of elements(for chemical characteriza-tion)and a radiographic grayscale image(for wood density)are obtained,i.e.the density and the element content are obtained.Then,cellulose is isolated from the 1-mm wood plate by removal of lignin,and hemicellulose.After producing this cellulose plate,cellulose subsamples are separated by knife under the microscope for inter-annual and intra-annual stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)analysis.Based on this method,RW,density,elemental composition,δ^(13)C,and δ^(18)O can be measured from the same sample,which reduces sample amount and treatment time,and is helpful for multi-proxy comparison and combination research.展开更多
Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temp...Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temperature of different periods of early half year, especially with January to August mean （JA） temperature, which means that JA temperature is one of the predominant limiting factors of tree growth in the Helan Mountain. Based on this analysis, we reconstructed JA temperature, and the explained variance is 43.3% （F=21.422, p〈0.001 ）. The comparatively high temperature periods in the reconstruction were： 1805-1818 1828-1857, 1899-1907, 1919-1931 and 1968-1995; and the comparatively low temperatu re periods happened in 1858-1872, 1883-1895 and 1935-1953. Ten-year moving average curve shows three slow uplifting trends： 1766-1853, 1862-1931 and 1944-1995. Each temperature increase was followed by a sudden temperature decrease about 10 years, that is to say, the JA temperature in the Helan Mountain is characterized by slow increase and sudden decrease. The 70- and 10.77-year periodicities detected in the temperature series correspond to the Gleissberg （80-year） and Schwabe （11-year） periodicities of solar activity respectively, the 2.11-2.62 years cycles are considered to be influenced by QBO （Quasi-Biennial-Oscillation） and the local environmental change.展开更多
Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living conifer...Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living coniferous forests on the Altay Mountains provide a good example for carrying out the dendrohydrological studies. In this study, a regional composite tree-ring width chronology developed by Lariat sibirica Ledeb. and Picea obovata Ledeb. was used to reconstruct a 301-year annual （from preceding July to succeeding June） streamflow for the Haba River, which originates in the southern Altay Mountains, Xinjiang, China. Results indicated that the reconstructed streamflow series and the observations were fitting well, and explained 47.5% of the variation in the observed streamflow of 1957-2008. Moreover, floods and droughts in 1949-2000 were precisely captured by the streamflow reconstruction. Based on the frequencies of the wettest/driest years and decades, we identified the 19th century as the century with the largest occurrence of hydrological fluctuations for the last 300 years. After applying a 21-year moving average, we found five wet （1724-1758, 1780-1810, 1822-1853, 1931-1967, and 1986-2004） and four dry （1759-1779, 1811-1821, 1854-1930, and 1968-1985） periods in the streamflow reconstruction. Furthermore, four periods （1770-1796, 1816-1836, 1884-1949, and 1973-1997） identified by the streamflow series had an obvious increasing trend. The increasing trend of streamflow since the 1970s was the biggest in the last 300 years and coincided with the recent warming-wetting trend in northwestern China. A significant correlation between streamflow and precipitation in the Altay Mountains indicated that the streamflow reconstruction contained not only local, but also broad-scale, hydro-climatic signals. The 24-year, 12-year, and 2.2-4.5-year cycles of the reconstruction revealed that the streamflow variability of the Haba River may be influenced by solar activity and the atmosphere-ocean system.展开更多
Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of L.chinensis were...Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of L.chinensis were examined.Correlation analysis showed that similar correlations between tree-ring width chronologies and climatic factors demonstrated that radial growth responded to climate change on both slopes.The radial growth of L.chinensis was mainly limited by temperature,especially the growing season.In contrast,both chronologies were negatively correlated with precipitation in May of the previous year and April of the current year.Spatial climate-correlation analyses with gridded land-surface climate data revealed that our tree-ring width chronologies contained a strong regional temperature signal over much of northcentral and eastern China.Spatial correlation with seasurface temperature fields highlights the influence of the Pacific Ocean,Indian Ocean,and North Atlantic Ocean.Wavelet coherence analysis indicated the existence of some decadal and interannual cycles in the two tree-ring width chronologies.This may suggest the influences of El Nin˜o-Southern Oscillation and solar activity on tree growth in the Qinling Mountains.These findings will help us understand the growth response of L.chinensis to climate change in the Qinling region,and they provide critical information for future climate reconstructions based on this species in semi-humid regions.展开更多
Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-...Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20<sup>th</sup> century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).展开更多
Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation a...Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years.展开更多
A tree-ring width chronology of 442 years(1567-2008) was developed from Tibetan junipers(S.tibetica) derived from south Tibet in western China.Three versions of chronology were produced according to standard dendrochr...A tree-ring width chronology of 442 years(1567-2008) was developed from Tibetan junipers(S.tibetica) derived from south Tibet in western China.Three versions of chronology were produced according to standard dendrochronological techniques.The correlation and response analysis displays a high correlation between the standard tree ring-width chronology and observed annual mean precipitation series during the period 1961-2008.Based on a linear regression model,an annual(prior August to current July) precipitation for the past 229 years was reconstructed.This is the first well-calibrated precipitation reconstruction for the Nanggarze region,south Tibet.The results show that relatively wet years with above-average precipitation occurred in 1780-1807,1854-1866,1886-1898,1904-1949,1967-1981 and 2000-2008,whereas relatively dry years with below-average precipitation prevailed during 1808-1853,1867-1885,1899-1903,1950-1966 and 1982-1999.Common dry/wet periods during 1890s,1910s,1940s-1960s and 1980s were also identified from other moisture reconstructions of nearby regions,indicating a synchronous climatic variation in south Tibet.Abrupt change beginning in 1888 was detected,revealing a transition from wet to dry conditions in south Tibet.Power spectrum analysis reveals significant cycles of 28-year,5.5-5.6-year and 3.3-year during the past 200 years.展开更多
Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data,...Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.展开更多
Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information con...Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information contained in tree-ring width chronology was obtained through linear regression reconstruction models of annual August–July precipitation and annual water discharge of the Selenga River during the period 1767–2015. Comparison of the smoothed series allowed estimating long-term variation component of these moisture regime parameters with a high precision. At the same time, regional drought indices are less correlated with pine radial growth, because they have contribution of the other environmental variables, which are much less reflected in the tree-ring of the investigated pine forest stands. Reconstructed dynamic of the moisture regime parameters is supported by documental evident of many socially significant events in the regional history, such as crop failures caused by both droughts and floods, and catastrophic fire in the Irkutsk City in 1879. Also, dependence of the amount of precipitation in the study area on the atmospheric circulation in Central Asia is revealed to have a similar pattern with other regions, i.e., a negative relationship of precipitation with the development of large high atmospheric pressure area within its center in the Altai and Tianshan mountains.展开更多
The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury(Hg)trends,but with the large knowledge gaps in the reliability.In this study,we comprehensively evaluated the Hg sou...The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury(Hg)trends,but with the large knowledge gaps in the reliability.In this study,we comprehensively evaluated the Hg source,radial translocation and age effect of Masson pine(Pinus massoniana)tree ring at Mt.Jinyun in Chongqing,to assess the suitability of such tree ring as the archive of atmospheric Hg.Results showed that distinct variabilities among Masson pine tree-ring Hg concentration profiles.The Hg concentration significantly increased along with stem height(P<0.05),indicating the Hg in tree rings mainly derived from foliage uptake atmospheric Hg.We found a distinct age effect that the tree ring of young trees had the higher Hg concentration.Besides,we used the advection-diffusion model to demonstrate how Hg concentration shifted by the advection or/and diffusion in tree rings.The modeling results showed that the advection induced radial translocation during the young growth period of tree was a plausible mechanism to result in the tree-ring Hg record largely different from the trend of anthropogenic Hg emissions in Chongqing.We finally suggest that in further Hg dendrochemistry,better discarding the tree-ring Hg profile of the young growth period to reduce impacts of the radial translocation and age effect.展开更多
Annual tree rings are widely recognized as valuable tools for quantifying and reconstructing historical forest disturbances.However,the influence of climate can complicate the detection of disturbance signals,leading ...Annual tree rings are widely recognized as valuable tools for quantifying and reconstructing historical forest disturbances.However,the influence of climate can complicate the detection of disturbance signals,leading to limited accuracy in existing methods.In this study,we propose a random under-sampling boosting(RUB)classifier that integrates both tree-ring and climate variables to enhance the detection of forest insect outbreaks.The study focused on 32 sites in Alberta,Canada,which documented insect outbreaks from 1939 to 2010.Through thorough feature engineering,model development,and tenfold cross-validation,multiple machine learning(ML)models were constructed.These models used ring width indices(RWIs)and climate variables within an 11-year window as input features,with outbreak and non-outbreak occurrences as the corresponding output variables.Our results reveal that the RUB model consistently demonstrated superior overall performance and stability,with an accuracy of 88.1%,which surpassed that of the other ML models.In addition,the relative importance of the feature variables followed the order RWIs>mean maximum temperature(Tmax)from May to July>mean total precipita-tion(Pmean)in July>mean minimum temperature(Tmin)in October.More importantly,the dfoliatR(an R package for detecting insect defoliation)and curve intervention detec-tion methods were inferior to the RUB model.Our findings underscore that integrating tree-ring width and climate vari-ables as predictors in machine learning offers a promising avenue for enhancing the accuracy of detecting forest insect outbreaks.展开更多
Based on 120 stem discs collected during3 months of fieldwork along a 12 km route,the history of fires in the Wari Maro Forest（09 1000 N–02 1000E） over the past century in savanna woodland and dry forest was recons...Based on 120 stem discs collected during3 months of fieldwork along a 12 km route,the history of fires in the Wari Maro Forest（09 1000 N–02 1000E） over the past century in savanna woodland and dry forest was reconstituted.Three major ecological areas are characterized：one highly burnt zone located between two relative less burnt areas.By analyzing tree rings,246 fire scars were identified.The scars were caused by 51 fire years,occurring at a mean interval of 2.23 years.From 1890 to1965,only 6 years with fires were recorded from sampled trees.Since 1966,no year has passed without fire.The fire frequency point scale reached 14 years.This was the case of Burkea africana,which has been identified as a species tolerant to fire and could be planted to create a natural firewall.In contrast,Anogeissus leiocarpa is highly sensitive to fire,and in a dry forest ecosystem that burns seasonally,it requires a special conservation plan.Two new concepts are described：the rebarking of trees after fire and Mean Kilometer Fire Interval.The first concept was tested with Daniellia oliveri（Rolfe） Hutch ＆ Dalz trees,and the second concept was used to evaluate spatial fire distribution.We demonstrate that savanna woodland and dry forest were subject to a degradation process caused by destructive fires related to vegetation cover clearance and illegal logging.展开更多
Silver fir(Abies alba Mill.)is a flexible European tree species,mainly vegetating within the mountainous regions of Europe,but its growth responses across its latitudinal and longitudinal range have not yet been satis...Silver fir(Abies alba Mill.)is a flexible European tree species,mainly vegetating within the mountainous regions of Europe,but its growth responses across its latitudinal and longitudinal range have not yet been satisfactorily verified under changing environmental conditions.This study describes the tree-ring increment of silver fir in research plots across a latitudinal gradient from the northern range in Czechia(CZ),through Croatia(HR)to the southernmost range in Italy(IT).The research aims to analyze in detail the dynamics and cyclicity of the ringwidth index(RWI)and how it relates to climatic factors(temperature and precipitation),the North Atlantic Oscillation(NAO),and total solar irradiance(TSI),including the determination of latitude.The results show that the main drivers affecting fir growth are the seasonal NAO index and TSI.Monthly temperatures affect RWI early in the vegetation season,while lack of precipitation during the summer is a limiting factor for fir growth,especially in July.Seasonal temperatures and temperatures in June and July negatively impact,while seasonal precipitation totals in the same months positively influence the RWI in all research plots across meridian.The longest growth cycles in fir RWI were recorded in the northernmost studied plots in CZ.These cyclical fluctuations recede approaching the south.The cyclic increase in RWI is related to the TSI,which decreases its effect from north to south.The TSI's effects vary,positively impacting CZ but negatively influencing HR while remaining relatively neutral in IT.On the other hand,seasonal NAO tends to negatively affect silver fir growth in HR and CZ but has a mildly positive effect in IT.In conclusion,the TSI and the influence of the seasonal NAO index are prevalent in the fir RWI and are accompanied by a greater cyclicity of RWI in Central Europe(temperature optimum)than in the Italian Mediterranean region,where this tree species is limited by climatic conditions,especially lack of precipitation.展开更多
基金Under the auspices of the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(No.2019QZKK0103)National Natural Science Foundation of China(No.41772173,41405077)+1 种基金the Thousand Talents Program for High-end Innovation of Qinghai Provincethe Applied Basic Research Project of Qinghai Province(No.2019-zj-7045)。
文摘Variations in vegetation are closely related to climate change, but understanding of their characteristics and causes remains limited. As a typical semi-humid and semi-arid cold plateau region, it is important to understand the knowledge of long term Normalized Difference Vegetation Index(NDVI) variations and find the potential causes in the source region of the Yangtze River. Based on four tree-ring width chronologies, the regional mean NDVI for July and August spanning the period 1665–2013 was reconstructed using a regression model, and it explained 43.9% of the total variance during the period 1981–2013. In decadal, the reconstructed NDVI showed eight growth stages(1754–1764, 1766–1783, 1794–1811, 1828–1838, 1843–1855, 1862–1873, 1897–1909, and 1932–1945)and four degradation stages(1679–1698, 1726–1753, 1910–1923, and 1988–2000). And based on wavelet analysis, significant cycles of2–3 yr and 3–8 yr were identified. In additional, there was a significant positive correlation between the NDVI and the Palmer Drought Severity Index(PDSI) during the past 349 yr, and they were mainly in phase. However, according to the results of correlation analysis between different grades of drought/wet and NDVI, there was significant asymmetry in extreme drought years and extreme wet years. In extreme drought years, NDVI was positively correlated with PDSI, and in extreme wet years they were negatively correlated.
基金supported by the National Natural Science Foundation of China(Nos.42271048,42430503,and 31971492).
文摘Tree rings provide long-term records of tree growth and climate changes,which makes them ideal benchmarks for forest modeling.Tree-ring information has greatly improved the reliability of 3-PG,which is one of the most commonly used process-based forest growth models.Here,we strengthen 3-PG's ability to simulate tree-ring width and stable carbon isotopes(δ^(13)C)by enhancing its descriptions of tree physiology.The major upgrade was adding a carbon storage pool for tree-ring formation using stored carbohydrates.We also incorporated previous modifications(replacing the age modifier with a height modifier)of 3-PG and tested their efficacy in improving tree-ring simulations.We ran the model based on two grand fir(Abies grandis)stands.The updated model greatly improved the simulations for both tree-ring widths andδ^(13)C.The results represent one of the best tree-ringδ^(13)C simulations,which accurately captured the amplitude in annual variations ofδ^(13)C.The correlations(R^(2))between simulations and observations reached 0.50 and 0.73 at two stands,respectively.The new model also greatly improved the simulations of raw tree-ring widths and detrended ring-width index(RWI).Because of better descriptions of tree physiology and more accurate simulations of tree rings than the previous model version,the updated 3-PG should provide more reliable simulations than previous 3-PG versions when tree-ring information is used as a benchmark in future studies.
文摘The Gabes aquifer system,located in southeastern Tunisia,is a crucial resource for supporting local socio-economic activities.Due to its dual porosity structure,is particularly vulnerable to pollution.This study aims to develop a hybrid model that combines the Fracture Aquifer Index(FAI)with the conventional GOD(Groundwater occurrence,Overall lithology,Depth to water table)method,to assess groundwater vulnerability in fractured aquifer.To develop the hybrid model,the classical GOD method was integrated with FAI to produce a single composite index.Each parameter within both GOD and FAI was scored,and a final index was calculated to delineate vulnerable areas.The results show that the study area can be classified into four vulnerability levels:Very low,low,moderate,and high,indicating that approximately 8%of the area exhibits very low vulnerability,29%has low vulnerability,25%falls into the moderate category,and 38%is considered highly vulnerable.The FAI-GOD model further incorporates fracture network characteristics.This refinement reduces the classification to three vulnerability classes:Low,medium,and high.The outcomes demonstrate that 46%of the area is highly vulnerable due to a dense concentration of fractures,while 17%represents an intermediate zone characterized by either shallow or deeper fractures.In contrast,37%corresponds to areas with lightly fractured rock,where the impact on vulnerability is minimal.Multivariate statistical analysis was employed using Principal Components Analysis(PCA)and Hierarchical Cluster Analysis(HCA)on 24 samples across six variables.The first three components account for over 76%of the total variance,reinforcing the significance of fracture dynamics in classifying vulnerability levels.The FAI-GOD model removes the very-low-vulnerability class and expands the spatial extent of low-and high-vulnerability zones,reflecting the dominant influence of fracture networks on aquifer sensitivity.While both indices use a five-class system,FAI-GOD redistributes vulnerability by eliminating very-low-vulnerability areas and amplifying low/high categories,highlighting the critical role of fractures.A strong correlation(R2=0.94)between the GOD and FAI-GOD indices,demonstrated through second-order polynomial regression,confirms the robustness of the FAI-GOD model in accurately predicting vulnerability to pollution.This model provides a useful framework for assessing the vulnerability of complex aquifers and serves as a decision-making tool for groundwater managers in similar areas.
基金Supported by Inter Disciplinary Direction Cultivation Project of Hunan University of Chinese Medicine,No.2025JC01032025 Hunan Province Science and Technology Innovation Plan Project,No.2025RC9012+2 种基金2022"Unveiling and Leading"Project of Discipline Construction at Hunan University of Chinese Medicine,No.22JBZ044Changsha Municipal Natural Science Foundation,No.kq2402174Hunan Provincial Science Popularization Fund Project,No.2025ZK4223.
文摘BACKGROUND Timely and accurate evaluation of mental disorders in adolescents using appropriate mental health literacy assessment tools is essential for improving their mental health literacy levels.AIM To develop an evaluation index system for the mental health literacy of adolescent patients with mental disorders,providing a scientific,comprehensive,and reliable tool for the monitoring and intervention of mental health literacy of such patients.METHODS From December 2022 to June 2023,the evaluation index system for mental health literacy of adolescents with mental disorders was developed through literature reviews,semi-structured interviews,expert letter consultations,and the analytic hierarchy process.Based on this index system,a self-assessment questionnaire was compiled and administered to 305 adolescents with mental disorders to test the reliability and validity of the index system.RESULTS The final evaluation index system for mental health literacy of adolescents with mental disorders included 4 first-level indicators,10 second-level indicators,and 52 third-level indicators.The overall Cronbach’sαcoefficient of the index system was 0.957,with a partial reliability of 0.826 and a content validity index of 0.975.The cumulative variance contribution rate of 10 common factors was 66.491%.The correlation coefficients between each dimension and the total questionnaire ranged from 0.672 to 0.724,while the correlation coefficients in each dimension ranged from 0.389 to 0.705.CONCLUSION The evaluation index system for mental health literacy of adolescents with mental disorders,developed in this study,demonstrated notable reliability and validity,making it a valuable tool for evaluating mental health literacy in this population.
基金Supported by the National Natural Science Foundation of China(Grant No.12071092)Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515012072)+1 种基金the Natural Science Research Project of Anhui Educational Committee(Grant No.2024AH051298)the Scientific Research Foundation of Bozhou University(Grant No.BYKQ202419).
文摘Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divides the order of a group G.In this paper,some characterizations of G being p-solvable or p-supersolvable were obtained by analyzing the normal index of certain subgroups of G.These results can be viewed as local version of recent results in the literature.
基金Project supported by the National Natural Science Foundation of China(Grant No.12175107)the Qing Lan Project of Jiangsu Province+2 种基金the Hua Li Talents Program of Nanjing University of PostsTelecommunications,Natural Science Foundation of Nanjing Vocational University of Industry Technology(Grant No.YK22-02-08)the Fund from the Research Center of Industrial Perception and Intelligent Manufacturing Equipment Engineering of Jiangsu Province,China(Grant No.ZK21-05-09)。
文摘Surface polaritons,as surface electromagnetic waves propagating along the surface of a medium,have played a crucial role in enhancing photonic spin Hall effect(PSHE)and developing highly sensitive refractive index(RI)sensors.Among them,the traditional surface plasmon polariton(SPP)based on noble metals limits its application beyond the near-infrared(IR)regime due to the large negative permittivity and optical losses.In this contribution,we theoretically proposed a highly sensitive PSHE sensor with the structure of Ge prism-SiC-Si:InAs-sensing medium,by taking advantage of the hybrid surface plasmon phonon polariton(SPPhP)in mid-IR regime.Here,heavily Si-doped InAs(Si:InAs)and SiC excite the SPP and surface phonon polariton(SPhP),and the hybrid SPPhP is realized in this system.More importantly,the designed PSHE sensor based on this SPPhP mechanism achieves the multi-stage RI measurements from 1.00025-1.00225 to 1.70025-1.70225,and the maximal intensity sensitivity and angle sensitivity can be up to 9.4×10^(4)μm/RIU and245°/RIU,respectively.These findings provide a new pathway for the enhancement of PSHE in mid-IR regime,and offer new opportunities to develop highly sensitive RI sensors in multi-scenario applications,such as harmful gas monitoring and biosensing.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDB40000000National Natural Science Foundation of China,No.41630531State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,CAS,No.SKLLQG2041。
文摘Droughts are the most frequent natural disaster in regions at the margins of the East Asian summer monsoon(EASM),which pose threats to agriculture,the economy,and human lives.However,the limitations of only approximately 60 years of meteorological observations hamper our understanding of the characteristics and mechanisms of local hydroclimate.Trees growing in the marginal region of the EASM are usually sensitive to moisture variations and have played important roles in past hydroclimatic reconstructions.Here,a 303-year tree-ring-width chronology of Pinus tabulaeformis from Mt.Lama,which is located in the junction of the Liaoning Province and Inner Mongolia,China,was used to reconstruct the May-August Palmer drought severity index(PDSI)in the marginal region of the EASM.The transfer function explains 48.0%(or 47.2%after adjusting for the loss of the degrees of freedom)of the variance over the calibration period from 1946 to 2012.A spatial correlation analysis demonstrates that our PDSI reconstruction can represent the drought variability on the northernmost margin of the EASM.The winter Asian polar vortex area index showed a delayed impact on the summer EASM precipitation in the following year.
基金supported the National Natural Science Foundation of China (42022059,41888101)the Strategic Priority Research Program of the Chinese Academy of Sciences,China (Grant No.XDB26020000)+1 种基金the Key Research Program of the Institute of Geology and Geophysics (CAS Grant IGGCAS-201905)the CAS Youth Interdisciplinary Team (JCTD-2021-05).
文摘Tree-ring width(RW),density,elemental com-position,and stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)are widely used as proxies to assess climate change,ecology,and environmental pollution;however,a specific pretreat-ment has been needed for each proxy.Here,we developed a method by which each proxy can be measured in the same sample.First,the sample is polished for ring width meas-urement.After obtaining the ring width data,the sample is cut to form a 1-mm-thick wood plate.The sample is then mounted in a vertical sample holder,and gradually scanned by an X-ray beam.Simultaneously,the count rates of the fluorescent photons of elements(for chemical characteriza-tion)and a radiographic grayscale image(for wood density)are obtained,i.e.the density and the element content are obtained.Then,cellulose is isolated from the 1-mm wood plate by removal of lignin,and hemicellulose.After producing this cellulose plate,cellulose subsamples are separated by knife under the microscope for inter-annual and intra-annual stable carbon and oxygen isotope(δ^(13)C,δ^(18)O)analysis.Based on this method,RW,density,elemental composition,δ^(13)C,and δ^(18)O can be measured from the same sample,which reduces sample amount and treatment time,and is helpful for multi-proxy comparison and combination research.
基金National Natural Science Foundation of China, No.40525004 No.40599420+2 种基金 No.90211081 No.40531003 No.40121303
文摘Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temperature of different periods of early half year, especially with January to August mean （JA） temperature, which means that JA temperature is one of the predominant limiting factors of tree growth in the Helan Mountain. Based on this analysis, we reconstructed JA temperature, and the explained variance is 43.3% （F=21.422, p〈0.001 ）. The comparatively high temperature periods in the reconstruction were： 1805-1818 1828-1857, 1899-1907, 1919-1931 and 1968-1995; and the comparatively low temperatu re periods happened in 1858-1872, 1883-1895 and 1935-1953. Ten-year moving average curve shows three slow uplifting trends： 1766-1853, 1862-1931 and 1944-1995. Each temperature increase was followed by a sudden temperature decrease about 10 years, that is to say, the JA temperature in the Helan Mountain is characterized by slow increase and sudden decrease. The 70- and 10.77-year periodicities detected in the temperature series correspond to the Gleissberg （80-year） and Schwabe （11-year） periodicities of solar activity respectively, the 2.11-2.62 years cycles are considered to be influenced by QBO （Quasi-Biennial-Oscillation） and the local environmental change.
基金supported by the National Natural Science Foundation of China (41275120, 41605047)the Shanghai Cooperation Organization Science and Technology Partnership (2017E01032)+1 种基金the Special Foundation for Asian Regional Cooperation (Climate Reconstruction of Tian Shan in China, Kyrgyzstan and Tajikistan)the Autonomous Region Youth Science and Technology Innovation Talents Training Project (qn2015bs025)
文摘Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living coniferous forests on the Altay Mountains provide a good example for carrying out the dendrohydrological studies. In this study, a regional composite tree-ring width chronology developed by Lariat sibirica Ledeb. and Picea obovata Ledeb. was used to reconstruct a 301-year annual （from preceding July to succeeding June） streamflow for the Haba River, which originates in the southern Altay Mountains, Xinjiang, China. Results indicated that the reconstructed streamflow series and the observations were fitting well, and explained 47.5% of the variation in the observed streamflow of 1957-2008. Moreover, floods and droughts in 1949-2000 were precisely captured by the streamflow reconstruction. Based on the frequencies of the wettest/driest years and decades, we identified the 19th century as the century with the largest occurrence of hydrological fluctuations for the last 300 years. After applying a 21-year moving average, we found five wet （1724-1758, 1780-1810, 1822-1853, 1931-1967, and 1986-2004） and four dry （1759-1779, 1811-1821, 1854-1930, and 1968-1985） periods in the streamflow reconstruction. Furthermore, four periods （1770-1796, 1816-1836, 1884-1949, and 1973-1997） identified by the streamflow series had an obvious increasing trend. The increasing trend of streamflow since the 1970s was the biggest in the last 300 years and coincided with the recent warming-wetting trend in northwestern China. A significant correlation between streamflow and precipitation in the Altay Mountains indicated that the streamflow reconstruction contained not only local, but also broad-scale, hydro-climatic signals. The 24-year, 12-year, and 2.2-4.5-year cycles of the reconstruction revealed that the streamflow variability of the Haba River may be influenced by solar activity and the atmosphere-ocean system.
基金funded by National Natural Science Foundation of China(No.31370587)
文摘Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of L.chinensis were examined.Correlation analysis showed that similar correlations between tree-ring width chronologies and climatic factors demonstrated that radial growth responded to climate change on both slopes.The radial growth of L.chinensis was mainly limited by temperature,especially the growing season.In contrast,both chronologies were negatively correlated with precipitation in May of the previous year and April of the current year.Spatial climate-correlation analyses with gridded land-surface climate data revealed that our tree-ring width chronologies contained a strong regional temperature signal over much of northcentral and eastern China.Spatial correlation with seasurface temperature fields highlights the influence of the Pacific Ocean,Indian Ocean,and North Atlantic Ocean.Wavelet coherence analysis indicated the existence of some decadal and interannual cycles in the two tree-ring width chronologies.This may suggest the influences of El Nin˜o-Southern Oscillation and solar activity on tree growth in the Qinling Mountains.These findings will help us understand the growth response of L.chinensis to climate change in the Qinling region,and they provide critical information for future climate reconstructions based on this species in semi-humid regions.
基金supported by the National Natural Science Foundation of China(91025002,30970492)the National Key Technology Research&Development Program(2012BAC08B05)the Key Project of the Chinese Academy of Sciences(KZZD-EW-04-05)
文摘Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20<sup>th</sup> century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).
基金supported by the National Natural Science Foundation of China (40801004, 40671184)the Research Fund for the Doctoral Program of Higher Education (20070027019)
文摘Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years.
基金funded by the National Basic Research Program of China (973 Program) (No.2010CB950104)the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists (Grant No.2009S1-38)+1 种基金the Chinese Academy of Sciences (CAS) 100 Talents Project (29082762)the NSFC (Grant no.40871091)
文摘A tree-ring width chronology of 442 years(1567-2008) was developed from Tibetan junipers(S.tibetica) derived from south Tibet in western China.Three versions of chronology were produced according to standard dendrochronological techniques.The correlation and response analysis displays a high correlation between the standard tree ring-width chronology and observed annual mean precipitation series during the period 1961-2008.Based on a linear regression model,an annual(prior August to current July) precipitation for the past 229 years was reconstructed.This is the first well-calibrated precipitation reconstruction for the Nanggarze region,south Tibet.The results show that relatively wet years with above-average precipitation occurred in 1780-1807,1854-1866,1886-1898,1904-1949,1967-1981 and 2000-2008,whereas relatively dry years with below-average precipitation prevailed during 1808-1853,1867-1885,1899-1903,1950-1966 and 1982-1999.Common dry/wet periods during 1890s,1910s,1940s-1960s and 1980s were also identified from other moisture reconstructions of nearby regions,indicating a synchronous climatic variation in south Tibet.Abrupt change beginning in 1888 was detected,revealing a transition from wet to dry conditions in south Tibet.Power spectrum analysis reveals significant cycles of 28-year,5.5-5.6-year and 3.3-year during the past 200 years.
基金supported by the Major Research Plan of National Natural Science Foundation of China (No. 91025014),the National Natural Science Foundation of China (No. 30800147)
文摘Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.
基金funded by the Russian Foundation for Basic Research (17-04-00315)the Russian Science Foundation (14-14-00219)
文摘Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information contained in tree-ring width chronology was obtained through linear regression reconstruction models of annual August–July precipitation and annual water discharge of the Selenga River during the period 1767–2015. Comparison of the smoothed series allowed estimating long-term variation component of these moisture regime parameters with a high precision. At the same time, regional drought indices are less correlated with pine radial growth, because they have contribution of the other environmental variables, which are much less reflected in the tree-ring of the investigated pine forest stands. Reconstructed dynamic of the moisture regime parameters is supported by documental evident of many socially significant events in the regional history, such as crop failures caused by both droughts and floods, and catastrophic fire in the Irkutsk City in 1879. Also, dependence of the amount of precipitation in the study area on the atmospheric circulation in Central Asia is revealed to have a similar pattern with other regions, i.e., a negative relationship of precipitation with the development of large high atmospheric pressure area within its center in the Altai and Tianshan mountains.
基金supported by the Natural Science Foundation of Chongqing(No.cstc2020jcyj-msxmX0063)the National Natural Science Foundation of China(No.41977272)。
文摘The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury(Hg)trends,but with the large knowledge gaps in the reliability.In this study,we comprehensively evaluated the Hg source,radial translocation and age effect of Masson pine(Pinus massoniana)tree ring at Mt.Jinyun in Chongqing,to assess the suitability of such tree ring as the archive of atmospheric Hg.Results showed that distinct variabilities among Masson pine tree-ring Hg concentration profiles.The Hg concentration significantly increased along with stem height(P<0.05),indicating the Hg in tree rings mainly derived from foliage uptake atmospheric Hg.We found a distinct age effect that the tree ring of young trees had the higher Hg concentration.Besides,we used the advection-diffusion model to demonstrate how Hg concentration shifted by the advection or/and diffusion in tree rings.The modeling results showed that the advection induced radial translocation during the young growth period of tree was a plausible mechanism to result in the tree-ring Hg record largely different from the trend of anthropogenic Hg emissions in Chongqing.We finally suggest that in further Hg dendrochemistry,better discarding the tree-ring Hg profile of the young growth period to reduce impacts of the radial translocation and age effect.
基金supported by the Xinjiang Regional Collaborative Innovation Project(2022E01045)Zhejiang University(108000*1942222R1).
文摘Annual tree rings are widely recognized as valuable tools for quantifying and reconstructing historical forest disturbances.However,the influence of climate can complicate the detection of disturbance signals,leading to limited accuracy in existing methods.In this study,we propose a random under-sampling boosting(RUB)classifier that integrates both tree-ring and climate variables to enhance the detection of forest insect outbreaks.The study focused on 32 sites in Alberta,Canada,which documented insect outbreaks from 1939 to 2010.Through thorough feature engineering,model development,and tenfold cross-validation,multiple machine learning(ML)models were constructed.These models used ring width indices(RWIs)and climate variables within an 11-year window as input features,with outbreak and non-outbreak occurrences as the corresponding output variables.Our results reveal that the RUB model consistently demonstrated superior overall performance and stability,with an accuracy of 88.1%,which surpassed that of the other ML models.In addition,the relative importance of the feature variables followed the order RWIs>mean maximum temperature(Tmax)from May to July>mean total precipita-tion(Pmean)in July>mean minimum temperature(Tmin)in October.More importantly,the dfoliatR(an R package for detecting insect defoliation)and curve intervention detec-tion methods were inferior to the RUB model.Our findings underscore that integrating tree-ring width and climate vari-ables as predictors in machine learning offers a promising avenue for enhancing the accuracy of detecting forest insect outbreaks.
基金funded by Deutscher Akademisher Austausch Dienst(DAAD)Biodiversity Monitoring Transect Analysis(BIOTA)project
文摘Based on 120 stem discs collected during3 months of fieldwork along a 12 km route,the history of fires in the Wari Maro Forest（09 1000 N–02 1000E） over the past century in savanna woodland and dry forest was reconstituted.Three major ecological areas are characterized：one highly burnt zone located between two relative less burnt areas.By analyzing tree rings,246 fire scars were identified.The scars were caused by 51 fire years,occurring at a mean interval of 2.23 years.From 1890 to1965,only 6 years with fires were recorded from sampled trees.Since 1966,no year has passed without fire.The fire frequency point scale reached 14 years.This was the case of Burkea africana,which has been identified as a species tolerant to fire and could be planted to create a natural firewall.In contrast,Anogeissus leiocarpa is highly sensitive to fire,and in a dry forest ecosystem that burns seasonally,it requires a special conservation plan.Two new concepts are described：the rebarking of trees after fire and Mean Kilometer Fire Interval.The first concept was tested with Daniellia oliveri（Rolfe） Hutch ＆ Dalz trees,and the second concept was used to evaluate spatial fire distribution.We demonstrate that savanna woodland and dry forest were subject to a degradation process caused by destructive fires related to vegetation cover clearance and illegal logging.
基金supported by the Czech University of Life Sciences Prague,Faculty of Forestry and Wood Sciences(No.IGA A_21_26)the Ministry of Agriculture of the Czech Republic(No.QK1910292 and QK21020371).
文摘Silver fir(Abies alba Mill.)is a flexible European tree species,mainly vegetating within the mountainous regions of Europe,but its growth responses across its latitudinal and longitudinal range have not yet been satisfactorily verified under changing environmental conditions.This study describes the tree-ring increment of silver fir in research plots across a latitudinal gradient from the northern range in Czechia(CZ),through Croatia(HR)to the southernmost range in Italy(IT).The research aims to analyze in detail the dynamics and cyclicity of the ringwidth index(RWI)and how it relates to climatic factors(temperature and precipitation),the North Atlantic Oscillation(NAO),and total solar irradiance(TSI),including the determination of latitude.The results show that the main drivers affecting fir growth are the seasonal NAO index and TSI.Monthly temperatures affect RWI early in the vegetation season,while lack of precipitation during the summer is a limiting factor for fir growth,especially in July.Seasonal temperatures and temperatures in June and July negatively impact,while seasonal precipitation totals in the same months positively influence the RWI in all research plots across meridian.The longest growth cycles in fir RWI were recorded in the northernmost studied plots in CZ.These cyclical fluctuations recede approaching the south.The cyclic increase in RWI is related to the TSI,which decreases its effect from north to south.The TSI's effects vary,positively impacting CZ but negatively influencing HR while remaining relatively neutral in IT.On the other hand,seasonal NAO tends to negatively affect silver fir growth in HR and CZ but has a mildly positive effect in IT.In conclusion,the TSI and the influence of the seasonal NAO index are prevalent in the fir RWI and are accompanied by a greater cyclicity of RWI in Central Europe(temperature optimum)than in the Italian Mediterranean region,where this tree species is limited by climatic conditions,especially lack of precipitation.
