http://people.ucalgary.ca/%7Ejohnsone/pub/Johnson&Gutsell_1994.pdf

Fire Frequency Models, Methods and Interpretations*

Tree populations located at the geographical distribution limit of the species may provide valuable information about tree-growth response to changes on climatic conditions. We established nine Pinus nigra ,1 2P. sylvestris and 17 P. uncinata tree-ring width chronologies along the eastern and northern Iberian Peninsula, where these species are found at the edge of their natural range. Tree-growth variability was analyzed using principal component analysis (PCA) for the period 1885–1992. Despite the diversity of species, habitats and climatic regimes, a common macroclimatic signal expressed by the first principal component (PC1) was found. Moreover, considering the PC1 scores as a regional chronology, significant relations were established with Spanish meteorological data. The shared variance held by the tree chronologies, the frequency of narrow rings and the interannual growth variability (sensitivity) increased markedly during the studied period. This shows an enhancement of growth synchrony among forests indicating that climate might have become more limiting to growth. Noticeably, an upward abrupt shift in common variability at the end of the first half of the 20th century was detected. On the other hand, moving-interval response functions showed a change in the growth–climate relationships during the same period. The relationship between growth and late summer/autumn temperatures of the year before growth (August– September, negative correlation, and November, positive correlation) became stronger. Hence, water stress increase during late summer previous to tree growth could be linked to the larger growth synchrony among sites, suggesting that climate was driving the growth pattern changes. This agrees with the upward trend in temperature observed in these months. Moreover, the higher occurrence of extreme years and the sensitivity increase in the second half of the 20th century were in agreement with an increment in precipitation variability during the growing period. Precipitation variability was positively related to tree-growth variability, but negatively to radial growth. In conclusion, a change in tree-growth pattern and in the climatic response of the studied forests was detected since the mid-20th century and linked to an increase in water stress. These temporal trends were in agreement with the observed increase in warmer conditions and in precipitation variability.

https://www7.nau.edu/mpcer/direnet/publications/publications_a/files/climate_increases_regional_tree-growth_variability_in_iberian_pine_forests.pdf

Climate increases regional tree‐growth variability in Iberian pine forests

/pdf/surface-temperature-reconstructions-for-the-last-2000-years-3bzwgubkk7.pdf

Surface temperature reconstructions for the last 2000 years

Considerable evidence exists that current global temperatures are higher than at any time during the past millennium. However, the long-term impacts of rising temperatures and associated shifts in the hydrological cycle on the productivity of ecosystems remain poorly understood for mid to high northern latitudes. Here, we quantify species-specific spatiotemporal variability in terrestrial aboveground biomass stem growth across Canada’s boreal forests from 1950 to the present. We use 873 newly developed tree-ring chronologies from Canada’s National Forest Inventory, representing an unprecedented degree of sampling standardization for a large-scale dendrochronological study. We find significant regional- and species-related trends in growth, but the positive and negative trends compensate each other to yield no strong overall trend in forest growth when averaged across the Canadian boreal forest. The spatial patterns of growth trends identified in our analysis were to some extent coherent with trends estimated by remote sensing, but there are wide areas where remote-sensing information did not match the forest growth trends. Quantifications of tree growth variability as a function of climate factors and atmospheric CO2 concentration reveal strong negative temperature and positive moisture controls on spatial patterns of tree growth rates, emphasizing the ecological sensitivity to regime shifts in the hydrological cycle. An enhanced dependence of forest growth on soil moisture during the late-20th century coincides with a rapid rise in summer temperatures and occurs despite potential compensating effects from increased atmospheric CO2 concentration.

https://www.pnas.org/content/pnas/113/52/E8406.full.pdf

No growth stimulation of Canada's boreal forest under half-century of combined warming and CO2 fertilization.

Summary 1 We examined the validity of classifying tree species as early, mid-, or late-successional based on age and height-growth rates, by comparing the age and height-growth rates of trees in the boreal forest. 2 Age was first examined using the traditional method of coring 30 cm above the root collar; then dendrochronology was used to locate the root collar and missing annual growth rings. Traditional ageing differentially underestimates tree age; species classified as early successional ( Populus tremuloides , Betula papyrifera , and Pinus banksiana ) are less severely underestimated than those classified as mid- and late-successional ( Picea glauca , Picea mariana , and Abies balsamea ) (0‐11 vs. 0‐43 years), and also have relatively fewer locally missing growth rings. Ageing at the root collar shows that all tree species recruit within 5‐10 years after fire and age cannot therefore be used to determine successional status. 3 Mean time taken to grow to each 1-m increment from the root collar was estimated for each species. Species classified as early successional have relatively higher growth rates between the root collar and the first metre; they are therefore less severely underestimated when aged above the root collar, explaining why they often appear older than species classified as mid- and late-successional. The lack of species differences above 1 m means that height-growth rates cannot be used to classify these tree species as early, mid-, or late-successional. 4 In the boreal forest of Saskatchewan, the rapid recruitment of all tree species after fire, and the short fire cycle mean that the forest dynamics between catastrophic wildfires are driven primarily by the mortality rates of each species.

https://besjournals.onlinelibrary.wiley.com/doi/epdf/10.1046/j.0022-0477.2001.00646.x

Accurately ageing trees and examining their height‐growth rates: implications for interpreting forest dynamics

For many types of forest studies, it is essential to identify the exact years of formation of annual rings in increment cores taken from living trees. To accomplish this, dendrochronologists employ...

A simple method for cross-dating increment cores from living trees

CORREL is a FORTRAN program that employs cross correlation to (i) determine potential cross-dating (matching) positions for "floating" (undated) ring series; (ii) detect missing or false rings; and...

A new computer program for estimating the statistical significance of cross-dating positions for "floating" tree-ring series

Tabulated Student's t-values and climatic insensitivity among inner tree-ring widths can bias estimates of statistical significance for cross correlations relating "floating" and master tree-ring s...

More on estimating the statistical significance of cross-dating positions for "floating" tree-ring series

A hoist–puller (come-along) or a scissor jack can be used to extract stuck increment borers from trees. An electric drill is also helpful for removing jammed wood from the inside of borers.

David K. Yamaguchi

Papers

A simple method for cross-dating increment cores from living trees

A new computer program for estimating the statistical significance of cross-dating positions for "floating" tree-ring series

More on estimating the statistical significance of cross-dating positions for "floating" tree-ring series

Mechanical devices for extracting stuck increment borers