Biomedical subjects

Merrill R. Kaufmann

Publications and source records attributed to Merrill R. Kaufmann.

5 recordsLinked to original sources

PubMed1990

Characteristics of high- and low-vigor lodgepole pine trees in old-growth stands.

Lodgepole pine (Pinus contorta var. latifolia Engelm.) trees in an old stand differed widely in appearance. Some appeared healthy, with deep crowns, high leaf areas, nearly conical-shaped crown tops, and branches with live needles extending well back from the tip. Others with similar-sized boles appeared to be in a state of decline, having much shallower crowns, lower leaf areas, crowns that were flattened at the top, and "tufted" branches with needles only near the ends of the branches. Ten trees, five each in these two apparent vigor classes, were selected from a one-hectare area of a mature stand. Trees in the two groups were found to have similar height, diameter at breast height, age, and total volume. As expected from the selection criteria, high-vigor trees had much deeper crowns (P = 0.01) and higher leaf areas (P = 0.10). The volume of heartwood in the bole was higher in the low-vigor trees (P = 0.08), and the volume of the sapwood was higher in the high-vigor trees (P = 0.13). Sapwood and heartwood ages were similar in both classes. This suggests that, in earlier years, low-vigor trees reached a larger volume, represented by the present heartwood, than did the high-vigor trees (i.e., the current vigor rankings are the reverse of what they had been). The ratio of sapwood volume to total leaf area was not significantly higher in the low-vigor trees (P = 0.24), although this ratio varied tenfold among the data. Results suggest that a physiological basis for assessing vigor involving leaf area, sapwood, heartwood, age, and incremental growth data would identify a continuum of response from high- to low-vigor trees rather than discrete groups based on visual appearance.

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PubMed1986

Physiographic, stand, and environmental effects on individual tree growth and growth efficiency in subalpine forests.

Annual volume growth of subalpine trees in the central Rocky Mountains was studied in relation to site and stand conditions. Growth of individual trees was most strongly influenced by estimated potential absorbed radiation, which varied with physiographic conditions and tree leaf area. Growth efficiency was estimated by the ratio of annual volume growth to potential radiation absorption by the crown. Growth efficiency was higher in young lodgepole pine (Pinus contorta var. latifolia Engelm.) than in Engelmann spruce (Picea engelmannii Parry ex Engelm.) or subalpine fir (Abies lasiocarpa (Hook.) Nutt.). In all species, growth efficiency declined sharply with age, and suppressed and overtopped trees had growth efficiencies equal to the highest efficiencies observed for dominant/codominant or intermediate trees. Lodgepole pine growth was most responsive to site and stand variables, Engelmann spruce was intermediate, and subalpine fir was rather unresponsive.

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PubMedDate not supplied

Tree physiology research in a changing world.

Changes in issues and advances in methodology have contributed to substantial progress in tree physiology research during the last several decades. Current research focuses on process interactions in complex systems and the integration of processes across multiple spatial and temporal scales. An increasingly important challenge for future research is assuring sustainability of production systems and forested ecosystems in the face of increased demands for natural resources and human disturbance of forests. Meeting this challenge requires significant shifts in research approach, including the study of limitations of productivity that may accompany achievement of system sustainability, and a focus on the biological capabilities of complex land bases altered by human activity.

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PubMedDate not supplied

To live fast or not: growth, vigor and longevity of old-growth ponderosa pine and lodgepole pine trees.

Old trees of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and lodgepole pine (Pinus contorta var. latifolia Engelm.) were studied to determine volume growth patterns in relation to leaf area. Ponderosa pine trees varied in age from 166 to 432 years and were about 77 cm in diameter; lodgepole pine trees varied in age from 250 to 296 years and were about 31 cm in diameter. With the exception of several ponderosa pine trees less than 200 years old, trees of both species had flattened tops, heavy branches, and foliage distribution characteristically found only in the oldest trees. After trees were felled, annual volume increments were determined from crossdated radial increments measured on discs at 4-m height intervals, and leaf areas were determined based on leaf area/branch sapwood area ratios for 1/5 sections of the crown for each tree. In ponderosa pine, three distinct volume growth patterns occurred: (1) a gradual increase in annual volume growth until felling; (2) a more rapid increase in growth to a plateau that persisted for a century or more; and (3) a rapid increase in growth followed by a generally sudden decrease in growth to less than half the earlier rates, and persisting at these lower rates for as long as seven decades. In lodgepole pine, fewer trees exhibited the sudden growth decline observed in ponderosa pine. Most short-term growth variations in ponderosa pine were synchronized among all trees, suggesting a common climatic signal. In lodgepole pine, annual variations in volume growth were slight. Volume growth in the most recent years before felling was weakly correlated with leaf area at the time of felling (r(2) = 0.45 for both species). However, in both species, trees having a high volume growth rate and leaf area at the time of felling had grown slowly when young, whereas trees having low volume growth rate and leaf area at felling grew rapidly when young. Thus a wide range of early and late growth patterns can lead to old-growth conditions in these species. Growth efficiencies (grams of dry matter per m(2) total leaf area) were generally higher for trees having the lowest leaf areas, and in almost all cases were below 100 g m(-2).

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PubMedDate not supplied

Performance of a canopy light interception model for conifer shoots, trees and stands.

A hierarchical approach was used to evaluate the behavior of a canopy light interception model using submodels for interception at levels of the shoot, crown and stand. Mean silhouette areas of individual shoots of lodgepole pine (Pinus contorta var. latifolia Engelm.) calculated assuming spherical shoot orientation agreed well with silhouette areas measured with a video projection system. A theoretical mean silhouette to total leaf area ratio (STAR) calculated using measured shoot characteristics and a model of shoot geometry agreed reasonably well with STAR values from measured shoot silhouette and leaf areas, although the range of calculated STAR values was slightly lower than that of the measured values. The shadow areas of tree crowns were underestimated for lodgepole pine; however, a model using regular shoot dispersion in the crown gave better agreement than a model based on random shoot dispersion. The underestimates may have been caused by underestimation either of leaf or branch area for the crowns or of the extinction coefficient. Two equations used to calculate leaf area from sapwood area measurements both underestimated leaf area. Accordingly, there are too many uncertainties to determine whether crown interception is best represented by a random or regular distribution of shoots. Mean canopy transmission in the Engelmann spruce (Picea engelmannii Parry ex Engelm.) stand was estimated very well by a random (Poisson) model of the spatial distribution of trees, whereas, in the lodgepole pine stand, a regular (hexagonal) model gave the best results. The Engelmann spruce stand had less regular tree spacing than the lodgepole pine stand. Taken as a whole, the weakest submodel for calculating canopy interception was the model for individual crown transmission, which underestimated crown shadow areas. However, the problem may be in leaf area estimates rather than in model performance.

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