DendroSync: An R package to unravel synchrony patterns in tree-ring networks

Spatial synchrony refers to the presence of a common signal for a time-varying characteristic that, in dendrosciences, is shared among tree-ring chronologies from a particular area. Analysis and interpretation of synchrony patterns in tree-ring networks is currently limited by: (i) the requirement for flexible modelling of complex correlations and heteroscedastic errors and (ii) the availability of ready-to-use open software to fulfil this task. We present an R package (DendroSync) that facilitates estimating and plotting synchrony patterns for pre-defined groups. The package has been devised to work with traits derived from tree rings (e.g. ring-width), but other data types are also suitable. It combines variance-covariance mixed modelling with functions that quantify the degree to which tree-ring chronologies contain a common signal over a fixed time period. It also estimates temporal changes in synchrony using a moving window algorithm. The functionality and usage of DendroSync are illustrated using a simple example

Radial Growth of Qilian Juniper on the Northeast Tibetan Plateau and Potential Climate Associations

There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110–2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes

Tree-ring width wavelet and spectral analysis of solar variability and climatic effects on a Chilean cypress during the last two and a half millennia

International audienceSpectral and wavelet analysis were performed on a tree ring width time series obtained from a 2500 yr old cypress tree (Fitzroya cupressoides) from Costa del Osorno, Chile. The periods for analysis were selected at 95% confidence level. Both periodicities characteristic of solar activity and climatic variations were found in this tree ring width series. The 11 and 22 years solar cycle periods were present in tree ring data with a confidence level above 98%. This indicates the solar modulation of climatic variations is being recorded by the tree ring grown. However wavelet analysis shows that these are present only sparsely. Short-term variations, between 2-5 years, are also present in tree ring data, and are shown by wavelet maps to be a more permanent characteristic. This time scale is a signature of ENSO events. Long-term variations, above 200 years, are also present in tree ring data. The spectral analysis performed in this work shows that this species has the ability to record solar-ENSO variations that seems to be affecting the local environment of tree growth, and also that this region was influenced by ENSO events at least in the past 2500 yr interval covered by this study

Multiple tree-ring parameters from Pinus nigra (Arnold) and their climate signal

The first exploration of climate signal in tree-rings of Black pine (P. nigra Arnold), using minimum blue intensity method, is presented. Sampled trees were growing on site Kojnik (Slovenia). For resin extraction and scanning, 5 mm thick cores were prepared. Whole tree-ring widths were measured, as well as the width and density of early- and latewood. To remove age trend and influence of non-climatic factors, raw measurements were standardized using spline function. In density measurements, highly significant correlation values were calculated between May-June summed precipitation and earlywood density (r = 0.64, p<0.001), while maximum latewood density correlates the best with mean June-August temperature (r = 0.42, p<0.01). In width measurements, the highest correlation was calculated between tree-ring width and mean June-August temperature (r = -0.62, p<0.001)

Arctic tree rings as recorders of variations in light availability

Annual growth ring variations in Arctic trees are often used to reconstruct surface temperature. In general, however, the growth of Arctic vegetation is limited both by temperature and light availability, suggesting that variations in atmospheric transmissivity may also influence tree-ring characteristics. Here we show that Arctic tree-ring density is sensitive to changes in light availability across two distinct phenomena: explosive volcanic eruptions (P<0.01) and the recent epoch of global dimming (P<0.01). In each case, the greatest response is found in the most light-limited regions of the Arctic. Essentially no late 20th century decline in tree-ring density relative to temperature is seen in the least light-limited regions of the Arctic. Consistent results follow from analysis of tree-ring width and from individually analysing each of seven tree species. Light availability thus appears an important control, opening the possibility for using tree rings to reconstruct historical changes in surface light intensity

Using longitudinal survival probabilities to test field vigour estimates in sugar maple (Acer saccharum Marsh.)

Tree mortality is a major force driving forest dynamics. To foresters, however, tree mortality is often considered a loss in productivity. To reduce tree mortality, silvicultural systems, such as selection cuts, aim at removing trees that are more likely to die. In order to identify trees with higher risks of mortality, field classifications are employed that assess vigour based on external characteristics of trees. We used a novel longitudinal approach for estimating survival probabilities based on ring-width measurements, initially developed by Bigler and Bugmann [Bigler, C., Bugmann, H., 2004. Predicting the time of tree death using dendrochronological data. Ecol. Appl. 14 (3), 902-914], to parameterize a survival probability model for sugar maple (Acer saccharum Marsh.) and to test whether field-assessed tree vigour classes are corroborated by survival probabilities determined from radial growth history. Data from 56 dead and 321 live sugar maples were collected in stands in western Quebec (Canada) that had undergone a selection cut ≈10 years prior to sampling. Our results showed that tree vigour established from external defects and pathological symptoms, using the classification of Boulet [Boulet, B., 2005. D

Tree-ring analysis of teak (Tectona grandis L.F.) in central India and its relationship with rainfall and moisture index

Tree-ring-width index chronologies of teak (Tectona grandis L.F.) from three sites in central India have been studied for their dendroclimatic potential. The existence of good correlation among the three site chronologies indicates the in.uence of common forcing factor to the tree growth of the region. Tree growth and climate relationship based on correlation analysis revealed the important contribution of moisture index and rainfall rather than the direct influence of the temperature on tree growth during different seasons. Signi.cant positive relationship of moisture index and rainfall during the monsoon months as well as on the annual scale with tree-ring width variations over the region indicates the important role of moisture availability at the root zone. The results suggest that the teak tree-ring chronologies can be used as high resolution proxy for past precipitation and moisture level in the environment

Do centennial tree-ring and stable isotope trends of Larix gmelinii (Rupr.) Rupr. indicate increasing water shortage in the Siberian north?

Tree-ring width of Larix gmelinii (Rupr.) Rupr., ratios of stable isotopes of C (δ13C) and O (δ18O) of whole wood and cellulose chronologies were obtained for the northern part of central Siberia (Tura, Russia) for the period 1864-2006. A strong decrease in the isotope ratios of O and C (after atmospheric δ13C corrections) and tree-ring width was observed for the period 1967-2005, while weather station data show a decrease in July precipitation, along with increasing July air temperature and vapor pressure deficit (VPD). Temperature at the end of May and the whole month of June mainly determines tree radial growth and marks the beginning of the vegetation period in this region. A positive correlation between tree-ring width and July precipitation was found for the calibration period 1929-2005. Positive significant correlations between C isotope chronologies and temperatures of June and July were found for whole wood and cellulose and negative relationships with July precipitation. These relationships are strengthened when the likely physiological response of trees to increased CO2 is taken into account (by applying a recently developed δ13C correction). For the O isotope ratios, positive relationships with annual temperature, VPD of July and a negative correlation with annual precipitation were observed. The δ18O in tree rings may reflect annual rather than summer temperatures, due to the late melting of the winter snow and its contribution to the tree water supply in summer. We observed a clear change in the isotope and climate trends after the 1960s, resulting in a drastic change in the relationship between C and O isotope ratios from a negative to a positive correlation. According to isotope fractionation models, this indicates reduced stomatal conductance at a relatively constant photosynthetic rate, as a response of trees to water deficit for the last half century in this permafrost regio

Is forest mushroom productivity driven by tree growth? Results from a thinning experiment

• Most of the edible forest mushrooms are mycorrhizal and depend on carbohydrates produced by the associated trees. Fruiting patterns of these fungi are not yet fully understood since climatic factors alone do not completely explain mushroom occurrence. • The objective of this study was to retrospectively find out if changing tree growth following an increment thinning has influenced the diversity patterns and productivity of associated forest mushrooms in the fungus reserve La Chanéaz, Switzerland. • The results reveal a clear temporal relationship between the thinning, the growth reaction of trees and the reaction of the fungal community, especially for the ectomycorrhizal species. The tree-ring width of the formerly suppressed beech trees and the fruit body number increased after thinning, leading to a significantly positive correlation between fruit body numbers and tree-ring width. • Fruit body production was influenced by previous annual tree growth, the best accordance was found between fruit body production and the tree-ring width two years previously. • The results support the hypothesis that ectomycorrhizal fruit body production must be linked with the growth of the associated host trees. Moreover, the findings indicate the importance of including mycorrhizal fungi as important players when discussing a tree as a carbon source or sin