Thinning even-aged Douglas-fir stands: effects of density and structure on stand volume growth

Thesis (Ph. D.)--University of Washington, 1987The usefulness of thinning studies in Douglas-fir stands has been limited by difficulties such as the long time period required, changing study objectives, and the limited scope of these studies. An approach is presented where two baseline models--based on volume estimates for unthinned stands from two Douglas-fir growth and yield models--are compared to the growth of measured thinned stands. The baseline models were similar over most of their common range of age and density, but at lower densities and older ages the models indicated substantially different volumes.Results from the 28-year Delezenne thinning study found volumes from thinned plots were comparable to, and in some cases exceeded, those of the baseline models. These high levels of production in the Delezenne plots suggest: (1) the growth and yield models are underestimating the growth of widely-spaced stands; and/or (2) an unrecognized potential exists for thinning to increase volume growth.Gross volume increment from the Delezenne plots was unaffected by thinning in most of the lightly-thinned plots and reduced in heavily-thinned plots. Net increment was increased in some thinned plots.Dominant and codominant trees produce more volume per tree and a greater portion of stand volume growth in thinned and unthinned stands. Average growth rates per unit of occupied growing space (growing space efficiency) were higher for dominants and codominants in unthinned stands. In thinned stands average growing space efficiency was similar among all represented crown classes. Tall trees and trees with medium-sized crowns were generally the most efficient.The correlations between growing space efficiency and other individual tree characteristics, and between individual tree characteristics, were lower in thinned stands than in unthinned stands, suggesting these relationships do not apply after thinning.Results suggest: (1) stand density measures do not provide similar expressions of competition in thinned stands; (2) density/growth relations are oversimplifications of a complex interaction of many variables; (3) optimal stand growth is obtained with a particular stand structure, not necessarily with a particular stand density; and (4) thinning may have the potential to increase gross stand volume growth

BAAD: a Biomass And Allometry Database for woody plants

Understanding how plants are constructed i.e., how key size dimensions and the amount of mass invested in different tissues varies among individuals is essential for modeling plant growth, carbon stocks, and energy fluxes in the terrestrial biosphere. Allocation patterns can differ through ontogeny, but also among coexisting species and among species adapted to different environments. While a variety of models dealing with biomass allocation exist, we lack a synthetic understanding of the underlying processes. This is partly due to the lack of suitable data sets for validating and parameterizing models. To that end, we present the Biomass And Allometry Database (BAAD) for woody plants. The BAAD contains 259 634 measurements collected in 176 different studies, from 21 084 individuals across 678 species. Most of these data come from existing publications. However, raw data were rarely made public at the time of publication. Thus, the BAAD contains data from different studies, transformed into standard units and variable names. The transformations were achieved using a common workflow for all raw data files. Other features that distinguish the BAAD are: (i) measurements were for individual plants rather than stand averages; (ii) individuals spanning a range of sizes were measured; (iii) plants from 0.01-100 m in height were included; and (iv) biomass was estimated directly, i.e., not indirectly via allometric equations (except in very large trees where biomass was estimated from detailed sub‐sampling). We included both wild and artificially grown plants. The data set contains the following size metrics: total leaf area; area of stem cross‐section including sapwood, heartwood, and bark; height of plant and crown base, crown area, and surface area; and the dry mass of leaf, stem, branches, sapwood, heartwood, bark, coarse roots, and fine root tissues. We also report other properties of individuals (age, leaf size, leaf mass per area, wood density, nitrogen content of leaves and wood), as well as information about the growing environment (location, light, experimental treatment, vegetation type) where available. It is our hope that making these data available will improve our ability to understand plant growth, ecosystem dynamics, and carbon cycling in the world's vegetation

TRY plant trait database - enhanced coverage and open access

10.1111/gcb.14904GLOBAL CHANGE BIOLOGY261119-18