Biomass, productivity and allocation patterns in tropical old-growth and logged-over forests in Ghana

Understanding how tropical forest structure and function change during the decades after logging is a key research challenge. This thesis reports functional traits, forest structure, biomass, net primary productivity (NPP) and allocation, as well as their controlling factors in an old-growth forest and a 54-year-old logged-over forest in Ghana. By analyzing root traits, I found fine-root biomass, root length, surface area, and root tissue density were higher in the logged-over forest, whereas the old-growth forest had higher specific root length and specific root area. I also found divergent exploitation strategies between the two forests; plants in the old-growth forest produced thinner roots, which increase resource uptake efficiency, while plants in the logged-over forest had thicker roots, which are associated with greater resource conservation. Through correlation analysis, I found that fine-root mass correlated positively to relative humidity, while absorbed photosynthetically active radiation and fine-root biomass were also positively correlated. Fine-root mass and soil K were also positively correlated, and fine-root necromass correlated positively with soil P. I then explored the relationships between leaf traits, taxonomic (e.g., species richness) or structural (e.g., tree diameter) variables and aboveground biomass (AGB) or coarse wood productivity (CWP) in the two forests. Leaf K related positively to tree biomass in the logged-over forest. Leaf N and P were significantly and positively related to tree productivity in the old-growth forest and logged-over forest. AGB and CWP were mostly explained by the structural variables. The shape and magnitude of the relationships between tree species richness and AGB or CWP differed between the two forests. In addition, I found that leaf area index, mean tree diameter and height were similar between the two forests, but stand density and basal area were higher in the logged-over forest than in the old-growth forest. Total biomass and annual NPP were comparable in both forests, but there was a shift in NPP allocation between wood and fine roots. I conclude that the forest structure, biomass and productivity of the logged-over forest have largely recovered, but the legacy of logging still persists, which is reflected in differences in functional traits and allocation patterns.Forestry, Faculty ofGraduat

Changes in mass, carbon, nitrogen and phosphorus in logs decomposing for 30 years in three Rocky Mountain coniferous forests

Estimates of decomposition rates of coarse woody debris (CWD) and fluxes of nutrients therein are essential components of C and nutrient budget models. In a 30-year field experiment, we periodically measured mass remaining and nutrient concentrations in log segments of pine, spruce and fir in natural, mature coniferous forests in Alberta, Canada. The predicted turnover times (t95; years) were 43-44 years for pine, 42-60 years for spruce and 38-46 years for fir. Extrapolating from best-fit models, we predict that decomposition of these logs would be complete within 50 â 60 years. C:N declined for most of the decomposition period and ratios of the three species converged atThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Effects of Leaf Age and Exogenous Hormones on Callus Initiation, Rooting Formation, Bud Germination, and Plantlet Formation in Chinese Fir Leaf Cuttings

To guide the cultivation of superior Chinese fir plantlets, we designed an L16(4)4 orthogonal experiment to determine how leaf age and exogenous hormones influence key growth processes in leaf cuttings. Hormone concentration and treatment duration significantly affected leaf cuttings in all three age categories; 6-benzylaminopurine (6-BA), 1-naphthaleneacetic acid (NAA), and treatment time exerted the strongest effects on callus initiation rates. Additionally, NAA had the largest effect on the rooting rate across all cuttings, and all three hormones significantly influenced the bud germination rate. Based on our experimental results, expected optimal treatments for callus initiation were 10 mg∙L−1 indole-3-butyric acid (IBA) for 10 min, 30 mg∙L−1 NAA for 15 min, and 10 mg∙L−1 NAA plus 30 mg∙L−1 IBA for 10 min. For the rooting rate, the expected optimal treatment was 50 mg∙L−1 NAA and 40 mg∙L−1 IBA for 5–20 min. Finally, for bud germination, optimal treatments were 20 min of immersion in water, 30 mg∙L−1 6-BA plus 50 mg∙L−1 NAA for 15 min, and 30 mg∙L−1 6-BA for 5 min. Plantlet formation only occurred in the <one-year-old leaves, and at very low rates (maximum 5.8%); this outcome is likely attributable to the mother plant’s relatively old age (five years). Plantlet formation from cuttings is dependent on ensuring the rooting rate after callus initiation. Therefore, to promote rooting rates and bud germination, we recommend leaving more xylem at the base of leaf cuttings