UC Berkeley

The root systems of forest ecosystem are both important and understudied. Roots function as the critical organs of nutrient uptake and anchor tree stems against wind throw and aboveground disturbance. Roots are also an important terrestrial reservoir of carbon and play an important role in global climate. Conversion or disturbance of forest lands can result in an emission of carbon dioxide to the atmosphere, and so quantifying the amount of carbon in root biomass is of interest for forest scientists and the climate policy their research informs.

This dissertation contributes to the science of root biomass measurement and modeling, providing techniques and approaches to improve those estimates, and models for leaf area that can be used to estimate root biomass. It focuses on techniques to improve measurement of root biomass using ground penetrating radar, an emergent method to measure root biomass. First, I investigate what above-ground metrics might best be used to model and predict root biomass and distribution and I develop new models relating basal area to leaf area for quaking aspen (Populus tremuloides) in the Sierra Nevada. Second, I investigate root biomass and distribution in coast redwood (Sequoia sempervirens), and how water acquisition may drive the allocation to roots in redwoods.

Ground penetrating radar is shown to have considerable utility for the measurement of coarse root biomass. Above ground biomass is shown to be an excellent predictor of coarse root biomass in Sierran ecosystems. Leaf area, which is predicted by pipe model theory to have a tight relationship with fine root biomass, is shown to have some predictive power for root biomass, and my model represents an improvement over other reported metrics. Finally, I conclude that global root biomass estimates have not been based on reliable or unbiased data to date and I contribute A plan to correct this gap in future global estimates.