Due to the lack of a uniform and accurate defi-nition of‘drought’,several indicators have been introduced based on different variables and methods,and the efficiency of each of these is determined according to their...Due to the lack of a uniform and accurate defi-nition of‘drought’,several indicators have been introduced based on different variables and methods,and the efficiency of each of these is determined according to their relationship with drought.The relationship between two drought indices,SPI(standardized precipitation index)and SPEI(standard-ized precipitation-evapotranspiration index)in different sea-sons was investigated using annual rings of 15 tree samples to determine the effect of drought on the growth of oriental beech(Fagus orientalis Lipsky)in the Hyrcanian forests of northern Iran.The different evapotranspiration calcula-tion methods were evaluated on SPEI efficiency based on Hargreaves-Samani,Thornthwaite,and Penman-Monteith methods using the step-by-step M5 decision tree regression method.The results show that SPEI based on the Penman-Monteith in a three-month time scale(spring)had similar temporal changes and a better relationship with annual tree rings(R^(2)=0.81)at a 0.05 significant level.Abrupt change and a decreasing trend in the time series of annual tree rings are similar to the variation in the SPEI based on the Penman-Monteith method.Factors affecting evapotranspiration,temperature,wind speed,and sunshine hours(used in the Penman-Monteith method),increased but precipitation decreased.Using non-linear modeling methods,SPEI based on Penman-Monteith best illustrated climate changes affecting tree growth.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
Because growth ring data have temporal features, time series analysis can be used to simulate and reveal changes in the life of a tree and contribute to plantation management. In this study, the autoregressive(AR) and...Because growth ring data have temporal features, time series analysis can be used to simulate and reveal changes in the life of a tree and contribute to plantation management. In this study, the autoregressive(AR) and moving average modeling method was used to simulate the time series for growth ring density in a larch plantation with different initial planting densities. We adopted the Box–Jenkins method for the modeling, which was initially based on an intuitive analysis of sequence graphs followed by the augmented Dickey–Fuller stationarity test. The order p and q of the ARMA(p, q) model was determined based on the autocorrelation and partial correlation coefficient figure truncated on the respective order.Through the residual judgment, the model AR(2) was only fitted to the larch growth ring density series for the plantation with the 1.5 9 2.0 m^2 initial planting density.Because the residuals series for the other three series was not shown as a white noise sequence, the modeling was rerun. Larch wood from the initial planting density of2.0 9 2.0 m^2 was modeled by ARMA(2, 1), and ARMA((1, 5), 3) fitted to the 2.5 9 2.5 m^2 initial planting density,and the 3.0 9 3.0 m^2 was modeled by AR(1, 2, 5).Although the ARMA modeling can simulate the change in growth ring density, data for the different growth ring time series were described by different models. Thus, time series modeling can be suitable for growth ring data analysis, revealing the time domain and frequency domain of growth ring data.展开更多
High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, ...High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.展开更多
Standardization is one of the important procedures in dendroclimatology. We used abundant Qilian juniper （Sabina przewalskii Kom.） tree-ring samples from the eastern margin of the Qaidam Basin to develop a new stand...Standardization is one of the important procedures in dendroclimatology. We used abundant Qilian juniper （Sabina przewalskii Kom.） tree-ring samples from the eastern margin of the Qaidam Basin to develop a new standardization method, i.e. total growth curve （TGC）. The samples that contained the complete pith and reached to the growing culmination around the 40th-60th year were used to fit TGC, and the generalized negative exponential function was used to fit the curve. Usually, most cores cannot reach the arboreal pith for some reasons and it is difficult to determine the arboreal cambial age. The empirical model of initial radial growth （IRG） was employed to estimate the number of rings missing from the pith by the same data and IRG model explained 90.9% of the variance. When developing the chronology, the cambial ages of cores that contained the complete pith were regarded as beginning from the first year and others were determined by the numbers of missing and included rings in the core. Standardization was accomplished by dividing each tree-ring series by corresponding TGC. The chronologies developed by TGC can retain more low-frequency variational information and TGC helps to develop more reliable tree-ring width chronology.展开更多
Poplar is raw material for various panel, paper and fiber products. The 12 sample trees of clone Nanlin-895 from four spacings were destructively harvested after thirteen growing seasons to assess the influence of spa...Poplar is raw material for various panel, paper and fiber products. The 12 sample trees of clone Nanlin-895 from four spacings were destructively harvested after thirteen growing seasons to assess the influence of spacing on radial growth and wood properties. Spacing significantly affected tree-ring width and wood basic density (p < 0.05) but not fiber traits. The highest diameter and wood basic density at breast height (1.3 m) was in 6 m × 6 m and 3 m × 8 m spacings, respectively. However, no significant differences in tree-ring width, wood basic density and fiber traits were observed among the four sampling directions in discs taken at 1.3 m for each spacing. Growth rings from the pith and tree heights had significant effects on wood basic density and fiber anatomical characteristics, highlighting obvious temporal-spatial variations. Pearson correlation analysis showed a significantly negative relationship of tree-ring width to wood basic density, fiber length and fiber width, but a significantly positive relationship to hemicellulose. There was no relationship with cellulose and lignin contents. Based on a comprehensive assessment by the TOPSIS method, the 6 m × 6 m spacing is recommended for producing wood fiber at similar sites in the future.展开更多
Tree growth is affected by environmental factors, climate condition and tree age. The objective of this study was to evaluate the growth patterns of <i><span style="font-family:Verdana;">Chamaecy...Tree growth is affected by environmental factors, climate condition and tree age. The objective of this study was to evaluate the growth patterns of <i><span style="font-family:Verdana;">Chamaecyparis</span></i> <i><span style="font-family:Verdana;">obtusa</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">C.</span></i> <i><span style="font-family:Verdana;">obtusa</span></i><span style="font-family:Verdana;">) stand in the Gyeongnam province. Data was collected from two cities and one county by using sample quadrats of 20 * 20 m. A total of 11 quadrats were used to collect tree height, diameter at the breast height (DBH), annual growth rings and soil data. The data analysis of soil moisture content, pH, organic matter (%), EC (cmol + /kg of soil), and available phosphorous was conducted. Growth ring was analyzed by using computer based software and the ages of the trees were identified. Average growth of height and DBH was computed from the surveyed data and annual growth of each tree was assessed by computer based reading of annual growth rings. The results of the study revealed that tree growth showed a reducing trend along the longevity. It was identified that soil pH, age, variation in annual average temperature, and altitude were the main factors related with growth of </span><i><span style="font-family:Verdana;">C.</span></i> <i><span style="font-family:Verdana;">obtusa</span></i><span style="font-family:Verdana;"> trees along the life of the stand.</span>展开更多
Huashan pine (Finus armandii Franch) is a poential species for dendroclimatic study. Ring-width cores were sampled for four stands of two sites from the eastern extreme of the Qinling Mountains. The ring-width chronol...Huashan pine (Finus armandii Franch) is a poential species for dendroclimatic study. Ring-width cores were sampled for four stands of two sites from the eastern extreme of the Qinling Mountains. The ring-width chronologies developed in this study cover a maximum Period from A.D. 1359 t0 1992 and show high common chronology variance over the common period 1911-1960.All the chronologies are significantly correlated with all others, and the degree of correlation appears related to tree age. Response function analyses reveal that from 41 to 75 Percent of chronology variance can be accounted for by monthly mean air temperature and monthly total precipitation. A sufficiently strong correlation of ringwidth index with May and June rainfall and June temperature exists, implying soil moisture to be a limiting factor for Huashan pine growth. The association displayed by response diagrams between narrow rings, low precipitation, and high temperature during spring and early summer indicates a promising potential of ring widths for reconstruction of spring drought for the study area.展开更多
Background: Climate-induced challenge remains a growing concern in the dry tropics, threatening carbon sink potential of tropical dry forests. Hence, understanding their responses to the changing climate is of high pr...Background: Climate-induced challenge remains a growing concern in the dry tropics, threatening carbon sink potential of tropical dry forests. Hence, understanding their responses to the changing climate is of high priority to facilitate sustainable management of the remnant dry forests. In this study, we examined the long-term climate-growth relations of main tree species in the remnant dry Afromontane forests in northern Ethiopia. The aim of this study was to assess the dendrochronological potential of selected dry Afromontane tree species and to study the influence of climatic variables (temperature and rainfall) on radial growth. It was hypothesized that there are potential tree species with discernible annual growth rings owing to the uni-modality of rainfall in the region. Ring width measurements were based on increment core samples and stem discs collected from a total of 106 trees belonging to three tree species (Juniperus procera, Olea europaea p. cuspidate and Podocarpus falcatus). Thesubsp. collected samples were prepared, crossdated, and analyzed using standard dendrochronological methods. The formation of annual growth rings of the study species was verified based on successful crossdatability and by correlating tree-ring widths with rainfall. Results: The results showed that all the sampled tree species form distinct growth boundaries though differences in the distinctiveness were observed among the species. Positive and significant correlations were found between the tree-ring widths and rainfall, implying that rainfall plays a vital role in determining tree growth in the region. The study confirmed the formation of annual growth rings through successful crossdating, thus highlighted the potential applicability of dendroclimatic studies in the region. Conclusions: Overall, the results proved the strong linkage between tree-ring chronologies and climate variability in the study region, which further strengthens the potential of dendrochronological studies developing in Ethiopia, and also has great implications for further paleo-climatic reconstructions and in the restoration of degraded lands. Further knowledge on the growth characteristics of tree species from the region is required to improve the network of tree-ring data and quality of the chronology so as to successfully reconstruct historic environmental changes.展开更多
基金This work was supported by Iran National Science Foundation(INSF)(grant no.96012844).
文摘Due to the lack of a uniform and accurate defi-nition of‘drought’,several indicators have been introduced based on different variables and methods,and the efficiency of each of these is determined according to their relationship with drought.The relationship between two drought indices,SPI(standardized precipitation index)and SPEI(standard-ized precipitation-evapotranspiration index)in different sea-sons was investigated using annual rings of 15 tree samples to determine the effect of drought on the growth of oriental beech(Fagus orientalis Lipsky)in the Hyrcanian forests of northern Iran.The different evapotranspiration calcula-tion methods were evaluated on SPEI efficiency based on Hargreaves-Samani,Thornthwaite,and Penman-Monteith methods using the step-by-step M5 decision tree regression method.The results show that SPEI based on the Penman-Monteith in a three-month time scale(spring)had similar temporal changes and a better relationship with annual tree rings(R^(2)=0.81)at a 0.05 significant level.Abrupt change and a decreasing trend in the time series of annual tree rings are similar to the variation in the SPEI based on the Penman-Monteith method.Factors affecting evapotranspiration,temperature,wind speed,and sunshine hours(used in the Penman-Monteith method),increased but precipitation decreased.Using non-linear modeling methods,SPEI based on Penman-Monteith best illustrated climate changes affecting tree growth.
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financially supported by the National Sci-Tech Support Plan of China(Grant No.2015BAD14B05)
文摘Because growth ring data have temporal features, time series analysis can be used to simulate and reveal changes in the life of a tree and contribute to plantation management. In this study, the autoregressive(AR) and moving average modeling method was used to simulate the time series for growth ring density in a larch plantation with different initial planting densities. We adopted the Box–Jenkins method for the modeling, which was initially based on an intuitive analysis of sequence graphs followed by the augmented Dickey–Fuller stationarity test. The order p and q of the ARMA(p, q) model was determined based on the autocorrelation and partial correlation coefficient figure truncated on the respective order.Through the residual judgment, the model AR(2) was only fitted to the larch growth ring density series for the plantation with the 1.5 9 2.0 m^2 initial planting density.Because the residuals series for the other three series was not shown as a white noise sequence, the modeling was rerun. Larch wood from the initial planting density of2.0 9 2.0 m^2 was modeled by ARMA(2, 1), and ARMA((1, 5), 3) fitted to the 2.5 9 2.5 m^2 initial planting density,and the 3.0 9 3.0 m^2 was modeled by AR(1, 2, 5).Although the ARMA modeling can simulate the change in growth ring density, data for the different growth ring time series were described by different models. Thus, time series modeling can be suitable for growth ring data analysis, revealing the time domain and frequency domain of growth ring data.
基金funded by the National Natural Science Foundation of China (40971032, 91125026)
文摘High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.
基金National Natural Science Foundation of China, No.40371118National Natural Science Foundation of China, No.90502009
文摘Standardization is one of the important procedures in dendroclimatology. We used abundant Qilian juniper （Sabina przewalskii Kom.） tree-ring samples from the eastern margin of the Qaidam Basin to develop a new standardization method, i.e. total growth curve （TGC）. The samples that contained the complete pith and reached to the growing culmination around the 40th-60th year were used to fit TGC, and the generalized negative exponential function was used to fit the curve. Usually, most cores cannot reach the arboreal pith for some reasons and it is difficult to determine the arboreal cambial age. The empirical model of initial radial growth （IRG） was employed to estimate the number of rings missing from the pith by the same data and IRG model explained 90.9% of the variance. When developing the chronology, the cambial ages of cores that contained the complete pith were regarded as beginning from the first year and others were determined by the numbers of missing and included rings in the core. Standardization was accomplished by dividing each tree-ring series by corresponding TGC. The chronologies developed by TGC can retain more low-frequency variational information and TGC helps to develop more reliable tree-ring width chronology.
基金The work was supported by the National Key Research and Development Program of China(Grant Number 2016YFD0600402).
文摘Poplar is raw material for various panel, paper and fiber products. The 12 sample trees of clone Nanlin-895 from four spacings were destructively harvested after thirteen growing seasons to assess the influence of spacing on radial growth and wood properties. Spacing significantly affected tree-ring width and wood basic density (p < 0.05) but not fiber traits. The highest diameter and wood basic density at breast height (1.3 m) was in 6 m × 6 m and 3 m × 8 m spacings, respectively. However, no significant differences in tree-ring width, wood basic density and fiber traits were observed among the four sampling directions in discs taken at 1.3 m for each spacing. Growth rings from the pith and tree heights had significant effects on wood basic density and fiber anatomical characteristics, highlighting obvious temporal-spatial variations. Pearson correlation analysis showed a significantly negative relationship of tree-ring width to wood basic density, fiber length and fiber width, but a significantly positive relationship to hemicellulose. There was no relationship with cellulose and lignin contents. Based on a comprehensive assessment by the TOPSIS method, the 6 m × 6 m spacing is recommended for producing wood fiber at similar sites in the future.
文摘Tree growth is affected by environmental factors, climate condition and tree age. The objective of this study was to evaluate the growth patterns of <i><span style="font-family:Verdana;">Chamaecyparis</span></i> <i><span style="font-family:Verdana;">obtusa</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">C.</span></i> <i><span style="font-family:Verdana;">obtusa</span></i><span style="font-family:Verdana;">) stand in the Gyeongnam province. Data was collected from two cities and one county by using sample quadrats of 20 * 20 m. A total of 11 quadrats were used to collect tree height, diameter at the breast height (DBH), annual growth rings and soil data. The data analysis of soil moisture content, pH, organic matter (%), EC (cmol + /kg of soil), and available phosphorous was conducted. Growth ring was analyzed by using computer based software and the ages of the trees were identified. Average growth of height and DBH was computed from the surveyed data and annual growth of each tree was assessed by computer based reading of annual growth rings. The results of the study revealed that tree growth showed a reducing trend along the longevity. It was identified that soil pH, age, variation in annual average temperature, and altitude were the main factors related with growth of </span><i><span style="font-family:Verdana;">C.</span></i> <i><span style="font-family:Verdana;">obtusa</span></i><span style="font-family:Verdana;"> trees along the life of the stand.</span>
文摘Huashan pine (Finus armandii Franch) is a poential species for dendroclimatic study. Ring-width cores were sampled for four stands of two sites from the eastern extreme of the Qinling Mountains. The ring-width chronologies developed in this study cover a maximum Period from A.D. 1359 t0 1992 and show high common chronology variance over the common period 1911-1960.All the chronologies are significantly correlated with all others, and the degree of correlation appears related to tree age. Response function analyses reveal that from 41 to 75 Percent of chronology variance can be accounted for by monthly mean air temperature and monthly total precipitation. A sufficiently strong correlation of ringwidth index with May and June rainfall and June temperature exists, implying soil moisture to be a limiting factor for Huashan pine growth. The association displayed by response diagrams between narrow rings, low precipitation, and high temperature during spring and early summer indicates a promising potential of ring widths for reconstruction of spring drought for the study area.
基金financial supports for this study were obtained from the Pan African University(PAU)African Union(AU)Addis Ababa,Ethiopia as part of its PhD scholarship scheme
文摘Background: Climate-induced challenge remains a growing concern in the dry tropics, threatening carbon sink potential of tropical dry forests. Hence, understanding their responses to the changing climate is of high priority to facilitate sustainable management of the remnant dry forests. In this study, we examined the long-term climate-growth relations of main tree species in the remnant dry Afromontane forests in northern Ethiopia. The aim of this study was to assess the dendrochronological potential of selected dry Afromontane tree species and to study the influence of climatic variables (temperature and rainfall) on radial growth. It was hypothesized that there are potential tree species with discernible annual growth rings owing to the uni-modality of rainfall in the region. Ring width measurements were based on increment core samples and stem discs collected from a total of 106 trees belonging to three tree species (Juniperus procera, Olea europaea p. cuspidate and Podocarpus falcatus). Thesubsp. collected samples were prepared, crossdated, and analyzed using standard dendrochronological methods. The formation of annual growth rings of the study species was verified based on successful crossdatability and by correlating tree-ring widths with rainfall. Results: The results showed that all the sampled tree species form distinct growth boundaries though differences in the distinctiveness were observed among the species. Positive and significant correlations were found between the tree-ring widths and rainfall, implying that rainfall plays a vital role in determining tree growth in the region. The study confirmed the formation of annual growth rings through successful crossdating, thus highlighted the potential applicability of dendroclimatic studies in the region. Conclusions: Overall, the results proved the strong linkage between tree-ring chronologies and climate variability in the study region, which further strengthens the potential of dendrochronological studies developing in Ethiopia, and also has great implications for further paleo-climatic reconstructions and in the restoration of degraded lands. Further knowledge on the growth characteristics of tree species from the region is required to improve the network of tree-ring data and quality of the chronology so as to successfully reconstruct historic environmental changes.
