Maximum Density Chronologies Research Articles

Responses to subtropical climate in radial growth and wood density of Chinese fir provenances, southern China

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) is a native tree species endemic to China and produces timber with high economic value. It is essential to select a provenance with more optimal adaptability to counteract the potential adverse effects of climate change. However, only a few dendroecology analyses of the variation in Chinese fir provenance climate response have been performed. Therefore, we obtained radial growth (tree ring width, earlywood width and latewood width) and wood density (earlywood density, latewood density, minimum density and maximum density) chronologies for 52 Chinese fir provenances grown in a common garden plantation in southern China. Tree-ring analysis methods (dendrochronology) were used to quantify the influence of climate on radial growth and wood densities of the Chinese fir provenances over a 32-year period (1981–2013). The results showed that the mean values of ring widths and wood densities were significantly related to latitude and longitude at the seed-source origin, respectively. Our study also confirmed that tree ring width is primarily sensitive to summer temperature, whereas parameter maximum density contains the strongest climate signal about spring precipitation. Along with a positive effect of warm winter (December and January) on radial growths, high temperatures in summer (July to September) had a negative effect on tree ring widths. Furthermore, the maximum density chronologies shared a significant negative response to the current April precipitation. However, our findings demonstrate that there is the greatest differentiation among Chinese fir provenances in the strength of the correlations between climate variables (temperature and precipitation) and tree ring indices. Based on responses to temperature and precipitation, Chinese fir provenances from the continuous China distribution range can be divided into several geographic groups along a longitudinal and latitudinal gradient. In general, our results suggest that in developing models to predict the response of Chinese fir to changing climate, it is necessary to include intraspecific differentiation in acclimation and adaptation to environmental factors.

Reconstructing mass balance of Garabashi Glacier (1800–2005) using dendrochronological data

Выполнена первая реконструкции баланса массы ледника Гарабаши по дендрохронологическим данным с 1800 по 2005 г. Лучше всего модель воспроизводит изменчивость годового баланса ледника при использовании хронологий по ширине годичных колец и по максимальной плотности поздней древесины. Изучен вклад каждой древесно-кольцевой хронологии в модель и её климатический отклик. Установлена высокая согласованность реконструкции баланса массы ледника по дендрохронологическим данным с реконструкциями, полученными ранее по метеорологическим рядам.

Intra-annual dendroclimatic reconstruction for northern British Columbia, Canada, using wood properties

Analyses of tree-ring wood properties combined with an understanding of tree physiology provided detailed intra-annual insights into historical and seasonal climate phenomena in sub-boreal forests of northern British Columbia. This study investigated historical climate trends in northern British Columbia, Canada, through the use of tree-ring proxies, and established a means of reconstructing intra-annual climate patterns from wood density, fibre properties and tree-ring width data. Specific attention was given to investigating how dendroclimatological analyses of intra-ring wood and fibre properties could be interpreted to improve the strength of proxy climate records. Trees were sampled at six sites in northern British Columbia. Spruce trees were collected from the Smithers area, whilst Douglas-fir trees were sampled at the northern latitudinal extent of their range near Babine and Francois Lakes, and at a precipitation-limited site near Valemount. Wood cores were analysed by Windendro® software with an ITRAX scanning densitometer, and by the SilviScan system located at the Australian Commonwealth Scientific and Research Organization. A mean June temperature proxy record dating to 1805 and a July–August mean temperature proxy record for Smithers extending from 1791 to 2006 were constructed from spruce ring width and maximum density chronologies. Douglas-fir ring width, spruce minimum density, and Douglas-fir maximum cell-wall thickness chronologies were used to reconstruct a May–June precipitation record extending from 1820 to 2006, and a July–August total precipitation record for Fort St. James that extends from 1912 to 2006. The results of the study demonstrate that a combination of multivariate and single-variate analyses provide detailed insights into seasonal radial growth characteristics. Tree physiological responses to climate at different times throughout the growing season, and temperature and precipitation fluctuations over the historical record are discussed.

Testing long-term summer temperature reconstruction based on maximum density chronologies obtained by reanalysis of tree-ring data sets from northernmost Sweden and Finland

Abstract. Here we analyse the maximum latewood density (MXD) chronologies of two published tree-ring data sets: one from Torneträsk region in northernmost Sweden (TORN; Melvin et al., 2013) and one from northern Fennoscandia (FENN; Esper et al., 2012). We paid particular attention to the MXD low-frequency variations to reconstruct summer (June–August, JJA) long-term temperature history. We used published methods of tree-ring standardization: regional curve standardization (RCS) combined with signal-free implementation. Comparisons with RCS chronologies produced using single and multiple (non-climatic) ageing curves (to be removed from the initial MXD series) were also carried out. We develop a novel method of standardization, the correction implementation of signal-free standardization, tailored for detection of pure low-frequency signal in tree-ring chronologies. In this method, the error in RCS chronology with signal-free implementation is analytically assessed and extracted to produce an advanced chronology. The importance of correction becomes obvious at lower frequencies as smoothed chronologies become progressively more correlative with correction implementation. Subsampling the FENN data to mimic the lower chronology sample size of TORN data shows that the chronologies bifurcate during the 7th, 9th, 17th and 20th centuries. We used the two MXD data sets to reconstruct summer temperature variations over the period 8 BC through AD 2010. Our new reconstruction shows multi-decadal to multi-centennial variability with changes in the amplitude of the summer temperature of 2.2 °C on average during the Common Era. Although the MXD data provide palaeoclimate research with a highly reliable summer temperature proxy, the bifurcating dendroclimatic signals identified in the two data sets imply that future research should aim at a more advanced understanding of MXD data on distinct issues: (1) influence of past population density variations on MXD production, (2) potential biases when calibrating differently produced MXD data to produce one proxy record, (3) influence of the biological age of MXD data when introducing young trees into the chronology over the most recent past and (4) possible role of waterlogging in MXD production when analysing tree-ring data of riparian trees.

PICEA SCHRENKIANA RING WIDTH AND DENSITY AT THE UPPER AND LOWER TREE LIMITS IN THE TIEN SHAN MTS (KYRGYZ REPUBLIC) AS A SOURCE OF PALEOCLIMATIC INFORMATION

We present here the results of spruce (Picea schrenkiana Fish. et May.) tree-ring research in the Tien Shan Mountains, Kirgiz Republic. We explore the connection between climatic parameters and spruce ring width and maximum density at the upper and lower tree limits and provide two reconstructions: the May-August temperature reconstruction from 1626 to 1995 based on a multi-site composite maximum density chronology from the upper tree limit and the drought index reconstruction from 1680 to 2000 based on the lower tree limit regional ring width chronology. The ring width chronologies from the upper and lower tree limits show a strong similarity. They both depend to a large extent on moisture availability. The maximum density chronology does not correlate with them: it depends on different climatic parameters, namely on the summer temperature. The correlations of the reconstructions with CRU TS3 temperature and precipitation grid point data confirm the results of the modeling using the meteorological data from the nearest stations. The 20th century does not look unusual in the context of the last three hundred years in the Tien Shan Mountains, either in terms of the drought occurrence and severity or in summer temperature changes. However the reconstruction does not encompass the last decade when the summer warming in Tine Shan has been especially prominent. In contrast, some change in precipitation is indicated with the 19th century being drier in the Issyk Kul region compared to the 20th century.

CLIMATE SIGNAL IN THE RING WIDTH, DENSITY AND CARBON STABLE ISOTOPES IN PINE (PINUS SILVESTRIS L.) IN CENTRAL CAUCASUS

Variability of width, maximum density and stable isotopes ( δ 13 C) in tree-rings of Scots pine (Pinus sylvestris L.) were studied in Northern Caucasus. Statistically sufficient agreements between ring width chronologies allow to construct composite chronology for the Elbrus area. Absence or low correlation between indices of the ring width and maximum density chronology point out different climatic signal. The influence of temperature and precipitation on these tree-ring parameters was also analyzed. The ring width of pine at the upper tree limit in the Baksan valley correlates positively with the June and July precipitation (r=0.3; 0.3; 0.4, p<0.05). No correlation with temperature parameters was found. The maximum density reflects the warm period temperature (April-October). The similarity in interannual variations of δ 13 C in annual rings between the individual samples means that their display a coherent common signal. This signal can be largely interpreted as the June and July precipitation.

Reconstructing mean maximum temperature of growing season from the maximum density of the Schrenk Spruce in Yili, Xinjiang, China

To study the historical temperature variation in Yili of Xinjiang, the tree-ring chronologies of maximum density (MXD) and tree-ring width (TRW) were established with the Schrenk Spruce (Picea schrenkiana Fisch. et Mey) collected from six sites to analyze the characteristics and ability of response to climate change. The results suggest that the MXD chronology of the Schrenk Spruce from different sampling sites responded to climate change well and were positively correlated with the mean maximum temperature and the mean temperature from April to August in the study area. The mean maximum temperature anomaly from April to August, spanning the years from 1848 to 2000, was reconstructed by three MXD chronologies which were selected by stepwise regression. The reconstructed function was stable and explained 56.2% of the variance. The reconstructed results indicated a cold span of 153 years in spring and summer from the beginning of the 1950s to the beginning of the 1970s in the Yili valley. No strongly increasing tendency was detected in the mean maximum temperature anomaly from April to August during this reconstructed period.

Torneträsk tree-ring width and density ad 500–2004: a test of climatic sensitivity and a new 1500-year reconstruction of north Fennoscandian summers

This paper presents updated tree-ring width (TRW) and maximum density (MXD) from Tornetrask in northern Sweden, now covering the period ad 500-2004. By including data from relatively young trees for the most recent period, a previously noted decline in recent MXD is eliminated. Non-climatological growth trends in the data are removed using Regional Curve Standardization (RCS), thus producing TRW and MXD chronologies with preserved low-frequency variability. The chronologies are calibrated using local and regional instrumental climate records. A bootstrapped response function analysis using regional climate data shows that tree growth is forced by April-August temperatures and that the regression weights for MXD are much stronger than for TRW. The robustness of the reconstruction equation is verified by independent temperature data and shows that 63-64% of the instrumental inter-annual variation is captured by the tree-ring data. This is a significant improvement compared to previously published reconstructions based on tree-ring data from Tornetrask. A divergence phenomenon around ad 1800, expressed as an increase in TRW that is not paralleled by temperature and MXD, is most likely an effect of major changes in the density of the pine population at this northern tree-line site. The bias introduced by this TRW phenomenon is assessed by producing a summer temperature reconstruction based on MXD exclusively. The new data show generally higher temperature estimates than previous reconstructions based on Tornetrask tree-ring data. The late-twentieth century, however, is not exceptionally warm in the new record: On decadal-to-centennial timescales, periods around ad 750, 1000, 1400, and 1750 were equally warm, or warmer. The 200-year long warm period centered on ad 1000 was significantly warmer than the late-twentieth century (p < 0.05) and is supported by other local and regional paleoclimate data. The new tree-ring evidence from Tornetrask suggests that this “Medieval Warm Period” in northern Fennoscandia was much warmer than previously recognized.

Tree-ring reconstruction of maximum and minimum temperatures and the diurnal temperature range in British Columbia, Canada

Summary This paper demonstrates the possibility of reconstructing May-August maximum (Tmax) and minimum (Tmin) temperatures plus the diurnal temperature range (DTR) using ring-width (RW) and maximum density (MXD) series from treeline sites across Interior British Columbia. Multiple linear regression of three orthogonal principal components (derived from 12 ring-width and 7 maximum density chronologies) were used to reconstruct each climate parameter separately over the 1820–1991 interval. Calibration explains 64% (Tmax), 39% (Tmin) and 40% (DTR) of the variance in the instrumental climate record (1895–1991). The Tmax reconstruction shows cool 19th century conditions with the warmest period in the 1940s. This trend agrees well with other summer temperature reconstructions in the southern Canadian Cordillera. The coolest reconstructed Tmin values are in the 1880s and increase steadily to the 1990s. Regional climate data show that the DTR has decreased in the late 20th century due to differences in the rate of change in Tmax and Tmin. These exploratory reconstructions suggest that recent trends in DTR are not unique in Interior British Columbia in context of the last 180 years. Our results also indicate that: (1) Tmean, Tmaxand Tmin may not vary consistently; (2) tree growth at these temperature-limited sites may be more closely related to Tmax than Tmean or Tmin; (3) recently reported changes in the relationships between mean temperatures and tree-ring variables may in part reflect the changing relative influence of maximum and minimum temperatures on mean temperature values. It may therefore be prudent, where possible, to reconstruct all three parameters to evaluate past temperature variability.