Latewood width(LWW)indices of trees are considered a reliable proxy of summer precipitation in the Northern Hemisphere.However,the strong coupling and high correlation between earlywood width(EWW)and LWW indices often...Latewood width(LWW)indices of trees are considered a reliable proxy of summer precipitation in the Northern Hemisphere.However,the strong coupling and high correlation between earlywood width(EWW)and LWW indices often prevent registration of climate signals of the LWW index.In this study,328-year-long earlywood width and latewood width chronologies were developed from Chinese pine at two sites in the Hasi Mountains,north central China.The climate responses of these chronologies were analyzed and the LWW index used to derive sum-mer precipitation signals.Correlation analyses showed that LWW was particularly influenced by earlywood growth and recorded stronger climate signals of the previous year as EWW,rather than those of the current year with infrequent summer climate signals.However,after removing the effect of earlywood growth using a simple regression model,the adjusted LWW chronology(LWW_(adj))showed a strong relationship with July precipitation in dry years.This suggests that the LWW_(adj) chronology has the potential to be used to investigate long-term variability in summer precipitation in drought-limited regions.展开更多
Hydroclimate affects the radial growth responses of trees, but the drivers of their spatial and population variability are not sufficiently understood. We addressed this issue by sampling several conifer populations l...Hydroclimate affects the radial growth responses of trees, but the drivers of their spatial and population variability are not sufficiently understood. We addressed this issue by sampling several conifer populations located at the same latitude, but at different longitude and elevation in western(W) and eastern(E) Mexican regions. We used dendroecology to disentangle how earlywood width(EW), latewood width(LW) and adjusted LW(LWadj),i.e. the residuals after removing EW influences on LW, responded to climate variables(temperature and precipitation), climate indices(Southern Oscillation Index, SOI, Nino 3.4, Pacific Decadal Oscillation, PDO) and a drought index(Standardised Precipitation-Evapotranspiration Index, SPEI). The W species(Pinus herrerae Martinez, Pinus durangensis Martinez, Abies durangensis Martínez and Cupressus lusitanica Mill.) showed lower growth rates than the E species(Pinus hartwegii Lindl., Picea mexicana Martinez, Pseudotsuga menziesii(Mirb.) Franco and Abies vejari Martinez). Growth in W benefits mostly from high precipitation in the prior winter and current spring and it is limited by high temperatures in spring, whereas growth in the E showed similar but weaker responses.Furthermore, positive(negative) correlations were found in radial growth with the Nino 3.4(SOI) and the PDO from the prior to current autumns, which were again stronger in absolute terms in the W than in the E regions,excepting SOI in summer. In the W, P. durangensis and C. lusitanica were the least and most responsive species to spring drought, respectively;whilst P. menziesii and A. vejari were very responsive to spring drought compared to P. hartwegii in the E. Our results suggest greater responsiveness to hydroclimate and atmospheric patterns in the W than in the E region. These findings allow better interpretations of future changes in growth and composition in Mexican conifer forests, considering that climate models forecast warmer spring conditions and increased water shortage.展开更多
This paper had developed a theoretical mathematics model of wood drying stress-strain using mathematical and physical theories and taking moisture content (MC) and ratio of every layer into consideration as explicit p...This paper had developed a theoretical mathematics model of wood drying stress-strain using mathematical and physical theories and taking moisture content (MC) and ratio of every layer into consideration as explicit parameters,predicted the development of stress-strain using MATLAB software,and analyzed the effect of MC and ratio of every layer. The results showed that on the condition of making the basic parameters set,the charts plotted by MATLAB software reflected the effect of MC and ratio of every layer. Total strain changed linearly with MC. The model could be applied to analyze the drying characters of a specimen with symmetric properties through the thickness.展开更多
In order to investigate the response to climate changes in radial growth of Picea crassifolia at the lower tree line in the middle Qilian mountains in northwestern China, relationships of standardized chronologies of ...In order to investigate the response to climate changes in radial growth of Picea crassifolia at the lower tree line in the middle Qilian mountains in northwestern China, relationships of standardized chronologies of annual ring, earlywood and latewood widths with mean monthly temperature and total monthly precipitation were analyzed by ways of correlation and pointer year analyses. The results show that annual ring, earlywood and latewood widths are significantly negatively correlated with mean monthly temperature in June and July. Annual ring and earlywood widths are significantly and positively correlated with total monthly precipitation in March, May and June and negatively correlated with total monthly precipitation in September. Latewood width is less sensitive to climate changes than the width of earlywood and insignificantly sensitive to precipitation. The results of pointer year analysis revealed that when summer temperatures are higher than the mean summer temperature synchronization and the summer precipitation lower than mean summer precipitation synchronization, narrow annual rings are formed. Wide annual rings are formed when summer temperatures are lower than the mean summer temperature synchronization and summer precipitation higher than mean summer precipitation synchronization. The results indicate that more precipitation in the spring and summer is helpful for radial growth while warmer summer restricts radial growth of P. crassifolia at the lower tree line in the middle Qilian mountains.展开更多
基金supportedbytheNational Natural Science Foundation of China (No.U21A2006 and 42001043).
文摘Latewood width(LWW)indices of trees are considered a reliable proxy of summer precipitation in the Northern Hemisphere.However,the strong coupling and high correlation between earlywood width(EWW)and LWW indices often prevent registration of climate signals of the LWW index.In this study,328-year-long earlywood width and latewood width chronologies were developed from Chinese pine at two sites in the Hasi Mountains,north central China.The climate responses of these chronologies were analyzed and the LWW index used to derive sum-mer precipitation signals.Correlation analyses showed that LWW was particularly influenced by earlywood growth and recorded stronger climate signals of the previous year as EWW,rather than those of the current year with infrequent summer climate signals.However,after removing the effect of earlywood growth using a simple regression model,the adjusted LWW chronology(LWW_(adj))showed a strong relationship with July precipitation in dry years.This suggests that the LWW_(adj) chronology has the potential to be used to investigate long-term variability in summer precipitation in drought-limited regions.
基金funded by CONACYT for funding provided through project A1-S-21471。
文摘Hydroclimate affects the radial growth responses of trees, but the drivers of their spatial and population variability are not sufficiently understood. We addressed this issue by sampling several conifer populations located at the same latitude, but at different longitude and elevation in western(W) and eastern(E) Mexican regions. We used dendroecology to disentangle how earlywood width(EW), latewood width(LW) and adjusted LW(LWadj),i.e. the residuals after removing EW influences on LW, responded to climate variables(temperature and precipitation), climate indices(Southern Oscillation Index, SOI, Nino 3.4, Pacific Decadal Oscillation, PDO) and a drought index(Standardised Precipitation-Evapotranspiration Index, SPEI). The W species(Pinus herrerae Martinez, Pinus durangensis Martinez, Abies durangensis Martínez and Cupressus lusitanica Mill.) showed lower growth rates than the E species(Pinus hartwegii Lindl., Picea mexicana Martinez, Pseudotsuga menziesii(Mirb.) Franco and Abies vejari Martinez). Growth in W benefits mostly from high precipitation in the prior winter and current spring and it is limited by high temperatures in spring, whereas growth in the E showed similar but weaker responses.Furthermore, positive(negative) correlations were found in radial growth with the Nino 3.4(SOI) and the PDO from the prior to current autumns, which were again stronger in absolute terms in the W than in the E regions,excepting SOI in summer. In the W, P. durangensis and C. lusitanica were the least and most responsive species to spring drought, respectively;whilst P. menziesii and A. vejari were very responsive to spring drought compared to P. hartwegii in the E. Our results suggest greater responsiveness to hydroclimate and atmospheric patterns in the W than in the E region. These findings allow better interpretations of future changes in growth and composition in Mexican conifer forests, considering that climate models forecast warmer spring conditions and increased water shortage.
文摘This paper had developed a theoretical mathematics model of wood drying stress-strain using mathematical and physical theories and taking moisture content (MC) and ratio of every layer into consideration as explicit parameters,predicted the development of stress-strain using MATLAB software,and analyzed the effect of MC and ratio of every layer. The results showed that on the condition of making the basic parameters set,the charts plotted by MATLAB software reflected the effect of MC and ratio of every layer. Total strain changed linearly with MC. The model could be applied to analyze the drying characters of a specimen with symmetric properties through the thickness.
基金financially supported by the Special Fund of the National Public Welfare Industry (Forestry) (No.200804001)the National Science Fund for Distinguished Young Scholars (No.30825034)
文摘In order to investigate the response to climate changes in radial growth of Picea crassifolia at the lower tree line in the middle Qilian mountains in northwestern China, relationships of standardized chronologies of annual ring, earlywood and latewood widths with mean monthly temperature and total monthly precipitation were analyzed by ways of correlation and pointer year analyses. The results show that annual ring, earlywood and latewood widths are significantly negatively correlated with mean monthly temperature in June and July. Annual ring and earlywood widths are significantly and positively correlated with total monthly precipitation in March, May and June and negatively correlated with total monthly precipitation in September. Latewood width is less sensitive to climate changes than the width of earlywood and insignificantly sensitive to precipitation. The results of pointer year analysis revealed that when summer temperatures are higher than the mean summer temperature synchronization and the summer precipitation lower than mean summer precipitation synchronization, narrow annual rings are formed. Wide annual rings are formed when summer temperatures are lower than the mean summer temperature synchronization and summer precipitation higher than mean summer precipitation synchronization. The results indicate that more precipitation in the spring and summer is helpful for radial growth while warmer summer restricts radial growth of P. crassifolia at the lower tree line in the middle Qilian mountains.
