Soil respiration, or the combined CO₂ emissions from roots and soil microorganisms, constitutes one of the largest losses of carbon (C) from terrestrial ecosystems. The major drivers of soil respiration, which include soil moisture, temperature, and substrate quality, have been known for some time. Nevertheless,
correlations between these drivers and...
My objectives were to investigate the correlation of height and diameter growth in young Douglas-fir (Pseudotsuga menziesii) plantations with stand density, and to determine the effects of stand density on the canopy boundary layer conductance (g[subscript]ac) and microclimate characteristics of young Douglas-fir plantations. I measured annual height (h) and diameter...
Canopy structure has a significant impact on the canopy hydrology of
Douglas-fir forests in the Pacific Northwest (PNW). Whole canopy rainfall
interception was measured for young Douglas-fir forest and compared to an
old-growth Douglas-fir forest. The old-growth forest had significantly greater
canopy water storage capacity (5) and direct throughfall fraction...
Many studies have shown that net primary production in old-growth Douglas-fir/western hemlock forests is lower than in younger forests in similar sites, although the cause is still not clear. One possibility is that overall carbon assimilation, or GPP, is lower in older forests. However, it is difficult to measure GPP...
Soils are the largest terrestrial pool of carbon, therefore it is critical to understand
what controls soil carbon efflux to the atmosphere in light of current climate uncertainty.
The primary efflux of carbon from soil is soil respiration which is typically categorized
into autotrophic and heterotrophic respiration. These two components...
The goal of this dissertation was to improve our understanding of age-related constraints on aboveground production of forest trees. Previous research suggesting that carbon uptake of old trees is hydraulically constrained by tree size was used as the
springboard for this research. Three specific working hypotheses were investigated: 1) compensation...
Exotic ponderosa pine (Pinus ponderosa Doug. ex Lawson) plantations are being planted within the natural distribution area of cordilleran cypress (Austrocedrus chilensis (D.Don) Pic. Ser. et Bizzarri) in Patagonia, Argentina. The productivity of these exotic plantations is much greater than that of native forests, suggesting greater water use. Before these...
Soil CO2 efflux is a major contributor of CO2 to the atmosphere. The rate that CO2 is respired out of the soil is called the soil flux (Fs). Many variables alter Fs. These variables differ drastically in the variety of ecosystems found on the earth. It is important to understand...
Warming of the terrestrial biosphere due to the anthropogenic addition of carbon dioxide to the earth’s atmosphere is becoming a major focus of scientific inquiry. Predictions of the extent of this warming are hampered by uncertainty in the ability of the earth’s ecosystems to counteract this effect by sequestering carbon...
Rainfall interception is a primary control over the moisture input to a forested ecosystem through the partitioning of precipitation into throughfall, stemflow, and an evaporated component (i.e. the interception loss). Rainfall interception is a spatially and temporally varying process at multiple scales, but heterogeneity in interception processes are poorly understood...
