Mean Ring Width Research Articles

Scaling of tree height and trunk diameter as a function of ring number

Phipps (1967) showed, in suppressed maples and oaks, that on average the cross-sectional area of successive tree rings is independent of ring number. From that empirical result I argued that mean ring width and mean ring diameter scale as the inverse square root and square root, respectively, of ring number (Prothero 1997). Here I give an illustrative argument as to how macroscopic trunk variables may be related quantitatively to microscopic ring variables. First, evidence is presented consistent with the theory of Greenhill (1881) and the empirical evidence of McMahon (1973) that tree height in a diversity of species scales as about the two-thirds power of trunk diameter. Here I report further evidence bearing on the same question. From these combined results I suggest that tree height, and by implication trunk height, and other parameters governing macroscopic tree trunk proportions, can all be expressed as powers of a microscopic variable, namely ring number, where the scaling exponents are all proper fractions. I suggest that at least one of these relationships is, in principle, non-adaptive.

Growth pattern of Picea rubens prior to canopy recruitment

A majority (72%) of Picea rubens Sarg. (red spruce) trees in an old-growth spruce-fir forest in the Great Smoky Mountains underwent episodes of radial growth suppression and release before they reached the forest canopy. Prior to canopy recruitment, trees experienced an average of 1.43 and a maximum of 7 suppression periods with an average ring width of 0.257 mm. Duration of suppression periods ranged from 4 to 79 years with an average of 19.05 years, which was significantly shorter than the average duration of release periods (29.00 years). Mean ring width in a suppression period was negatively correlated with duration of the suppression period. The opposite was true for release periods. The severity of suppression had no significant effect on mean ring width in subsequent release periods. Greater suppression was observed in the recent growth pattern of current non-canopy trees than in the historical growth pattern reconstructed from current canopy trees. Growth releases prior to canopy recruitment, triggered by small gaps or neighboring gaps, displayed a continuous pattern over the last two centuries and had consistent frequency in recent decades. By contrast, canopy recruitment resulting from large-gap disturbances was discontinuous over the last two centuries, and less frequent after 1850.

Growth-ring analysis of Early Tertiary conifer woods from the Canadian High Arctic and its paleoclimatic interpretation

Abstract Fossil forests, where petrified stumps were preserved in growth position, have been found within Early Tertiary sediments near Strathcona Fiord, Ellesmere Island, Canadian Arctic Archipelago. These fossil forests are obvious evidence for Early Tertiary climate much warmer than that of today. We analyzed the growth rings of petrified woods from two fossil forest sites (one in middle Paleocene, and the other in late Early Eocene) to extract information on climate change. The woods consist most abundantly of Metasequoia and cf. Glyptostrobus, suggesting that these forests grew in similar environments of warm to cool temperate climates. Mean ring width, mean sensitivity and power spectrum were calculated for ring-width sequences. Although significant difference in the mean ring width between the two forests was found, a comparison with living trees suggests that the difference can be attributed to the specific difference between the forests, so that a significant climate change may not necessarily be invoked. We found little significant difference in the mean sensitivity and power spectrum between the forests, neither did we find any strong indication of periodicities. Consideration of all features suggests that there was no significant difference in climate of middle Paleocene and late Early Eocene time in the High Arctic. However, the mean ring-widths of these forests were significantly smaller than that reported for mid-Cretaceous High Arctic fossil forest.

Increase in tree-ring width in subalpine Pinus cembra from the central Alps that may be CO2-related

It has been suggested many times that elevated atmospheric CO2 levels should stimulate radial increment of stem growth. However, interpretation of dendrochronologies with respect to a CO2 signal is a difficult task, since a multitude of environmental and tree factors influence the growth of stems. Here we provide a data set from subalpine stone pine which covers the period from 1750 to 1988, and from which growth rings of the 80- to 90-year age class were analysed. The most common climatological effects are taken into consideration. We found a steady and significant increase of mean ring width for the considered age class from approximately 1 mm per year in the middle of the last century to about 1.4 mm per year at present. Selected periods of equal mean summer temperatures in the last century and in more recent decades still yield a mean stimulation of about 25% for which atmospheric CO2 enrichment appears to be the most plausible explanation. The recent dramatic increase of atmospheric N-deposition could confound this interpretation, but chronologies of the last 2 decades during which wet and dry deposition of N-compounds showed the most dramatic increase exhibit no deviation from the long term trend. In contrast to the so far conflicting evidence of tree-ring responses to atmospheric changes the clear signal obtained here may be explained as follows: (1) stone pine produces little late season wood and moisture is never a limiting factor (particularly not in the early season); (2) comparatively good climatic records permitted the selection of thermally comparable periods; (3) trees grew under little spatial competition, (4) cores were collected well below the upper altitudinal range-limit of stone pine, leaving enough physiological leeway under episodic climatic stress, but (5) trees grew at altitudes high enough so that the reduction of the partial pressure of CO2 could be expected to cause CO2 to become relatively more limiting than at low elevations.

Decreasing frequency of forest fires in the southern boreal zone of Québec and its relation to global warming since the end of the 'Little Ice Age'

Although an increasing frequency of forest fires has been suggested as a consequence of global warming, there are no empirical data that have shown a climatically driven change in fire frequency since the warming that has followed the end of the 'Little Ice Age'. We present here evidence from fire and tree-ring chronologies that the post-'Little Ice Age' climate change has profoundly decreased the frequency of fires in the northwestern Québec boreal forest. A 300-year fire history (AD 1688-1988) from the Lake Duparquet area (48°28' N, 79°17' W) shows an important decrease, starting 100 years ago, in the number and the extent of fires. This decrease in fire frequency is also associated with a long- term increase in the mean ring width of northern white cedar (Thuja occidentalis L.) in the same area. Agreement between the standardized tree-ring chronology and fire years, together with a negative correlation with a drought index reconstructed for the AD 1913-1987 period, shows that the decrease in fire frequency may be related to a reduced frequency of drought periods since the end of the 'Little Ice Age'. The contradictory results between predicted and observed effects of warming on fire frequency call into question our present capability to generalize the effect of increasing CO2 levels on fire frequency.

Two hundred year variation of southern red spruce radial growth as estimated by spectral analysis

Spectral analysis was applied to high-elevation (≥1800 m) old-growth (≥200 years) red spruce (Picearubens Sarg.) tree-ring data from eight plots on Clingmans Dome, North Carolina. Low-frequency sine and cosine functions with wavelengths greater than or equal to 10 years accounted for between 76 and 90% of the variation in mean ring widths for all eight sites analyzed. Mean radial growth has increased and decreased no less than nine times over the last 200 years, with no evidence of constant radial growth for extended periods of time. Since the mid-1960s, radial growth has decreased and increased twice and is currently increasing through 1986, the last year of sampling. Growth in 1976 was equal to or greater than pre-1965 levels. A local maximum (mid-1960s) of the periodic cycles in radial growth coincides with the reported downturn in radial growth of red spruce at other locations in the southern Appalachians. Verification of historical growth periodicities can best be evaluated through continual monitoring of trees from a greater number of sites.

Dendrochronological analysis of single-tree interactions in mixed pine-oak stands of central Arizona, USA

Radial growth of ponderosa pine after stand establishment was dendrochronologically analyzed in relation to varying amounts of Gambel oak presence on the Beaver Creek Experimental Watershed, Arizona. Climate, topography, soil parent material, vegetation structure and soil type were uniform across selected sites. Intra- and inter-specific competition affecting individual pines was quantified using an age-independent index, also modified for asymmetric competition. Pine mean ring width and mean ring area were regressed against competition indices, pine age, and height index after accounting for sites and plots in sites. Dendrochronological techniques provided accurate high resolution data, which were used to reconstruct the growth history of individual pines and stands. Site interactions were never significant, and fitted models explained from 50 to 66% of the total variance. Regression statistics were best when competition indices assumed symmetric interactions. Mean radial growth of pine over 5 and 10 years was negatively related to intra-specific competition, but was not significantly related to inter-specific competition between pine and oak. This could be attributed to the positive influence of oak on soil nutrient status and/or to increased pine spacing caused by the presence of oak.

Methods of detecting past spruce beetle outbreaks in Rocky Mountain subalpine forests

We examined the use of dendrochronological techniques and stand age structure for detecting past outbreaks of spruce beetle (Dendroctonusrufipennis Kirby) in subalpine forests in the Colorado Rocky Mountains. The methods were based on the observation that following beetle-caused mortality of canopy trees, growth rates of subcanopy Engelmann spruce (Piceaengelmannii (Parry) Engelm.) and subalpine fir (Abieslasiocarpa (Hook.) Nutt.) increase severalfold and remain high for several decades or more. Although inspection of unstandardized individual tree ring-width chronologies is useful for detecting past disturbance, standardized mean chronologies based on ≥20 cores assure adequate sample sizes and improve interpretability. Standardization of ring-width series by fitting the observed data to a horizontal line passing through the mean ring width facilitates detection of past outbreaks better than other standardization models such as polynomial or cubic spline functions. The incorporation of samples from dead-standing trees increases sample sizes and reveals patterns in the early history of a stand that may not be detectable if samples only from live trees are used. Patterns of release frequencies based on nearly all the trees in a stand were helpful in confirming interpretations not always clear from the chronologies alone. Variations in tree population age structures were related to the history of disturbance by beetle outbreak, but age structure alone was not a reliable means of detecting past outbreaks.

The Relationships between Oak Tree Growth and Climate in Britain

SUMMARY (1) At thirteen sites in the British Isles between ten and twenty oak trees (185 in all) were sampled for dendroclimatological study. The growth ring widths were measured and, after standardization, a mean ring width index was derived for each year for each site. (2) The resulting site-index time-series were tested for climate relationships by the response function method which relates tree growth to variations in monthly temperature and precipitation. (3) Marked similarities in response functions throughout the British Isles enabled a generalized British Isles oak response function to be constructed. This shows that high rainfall, particularly in the growing season, and high temperatures in early summer favour growth. High temperatures in the previous winter, however, are detrimental to growth in the following season perhaps due to loss of food reserves.

Tree Ring and Climate change in Langtang National Park, Central Nepal

In present study 120 tree cores from 60 trees of Abies spectabilis from two different sites Chandanbari and Cholangpati area of Langtang National Park were collected. Analysis of increment cores showed that trees in those stands were 100-300 years old. Trees of Chandanbari site were found to be older than Cholangpati. Mean tree ring width of Chandanbari was 2.34 mm and that of Cholangpati site 1.70 mm. Growth rate was higher (2.34 mm/yr) at the Chandanbari than that of Cholangpati (1.70 mm/yr). Series intercorrelation and mean sensitivity were 0.457 and 0.223 for Chandanbari and 0.499 and 0.203 for Cholangpati, respectively. The high mean sensitivity value indicated that high inter-annual variability was present in the ring widths and that the chronology was sensitive to yearly environmental changes; ring width was negatively correlated with minimum monthly temperature and positively correlated with total monthly precipitation.DOI: 10.3126/on.v8i1.4321

VARIATION OF DENSITY IN STEMS OF DOUGLAS FIR

In a disk from the stem of a very fast-grown Douglas fir ( Pseudotsuga taxifolia Brit.), 19 years old, with an almost constant ring-width of about ⅓ inch, the density of the individual rings was almost constant from pith to bark and there was no sign of any increase outwards such as was found by Turnbull in fast-grown South African pines. Similar results were also obtained with more closely grown material (mean ring-width about 1 1/0 inch). There appeared to be no general relation between density and ring-width, but the highest densities occurred in rings less than 6 mm. wide in the centre of the fast-grown tree and at the outside of a tree with access to river water.