We assessed the differential advantages of deciduousness and evergreenness by examining 26 site-years of carbon dioxide, water vapor, and energy flux measurements from five comparable oak woodlands in France, Italy, Portugal, and California (USA). On average, the evergreen and deciduous oak woodlands assimilated and respired similar …
Journal: Ecological Applications, Volume 20 (6): 1583-1597 (2010). DOI: 10.1890/08-2047.1 Sites: US-Ton
Groundwater can serve as an important resource for woody vegetation in semiarid landscapes, particularly when soil water is functionally depleted and unavailable to plants. This study examines the uptake of groundwater by deciduous blue oak trees (Quercus douglasii) in a California oak savanna. Here we present a suite of …
Journal: Water Resources Research, Volume 46 (10): n/a-n/a (2010). DOI: 10.1029/2009wr008902 Sites: US-Ton
Journal: Ecosystem Function In Savannas, Volume : 135-151 (2010). DOI: 10.1201/b10275-10 Sites: US-Ton
Simple but realistic modeling of radiation transfer within heterogeneous canopy has been a challenging research question for decades and is critical for predicting ecological processes such as photosynthesis. The Markov model proposed by [Nilson, T., 1971. A theoretical analysis of the frequency of gaps in plant stands. Agric. Meteorol. …
Journal: Agricultural And Forest Meteorology, Volume 148 (6-7): 1005-1020 (2008). DOI: 10.1016/j.agrformet.2008.01.020 Sites: US-Ton
The study of water exchange between soil, plants, and the atmosphere in response to seasonal or periodic droughts is critical to modeling the hydrologic cycle and biogeochemical processes in water-controlled ecosystems. An essential step in such studies is to characterize changes in evaporation and transpiration under water stress. …
Journal: Water Resources Research, Volume 44 (8): n/a-n/a (2008). DOI: 10.1029/2007wr006646 Sites: US-Ton
To understand the dynamics of ecosystem carbon cycling, CO2 fluxes were measured over and under an oak–grass savanna and over a proximate grassland in California. The measurements were made from 2000 to 2006 using the eddy covariance technique. Annual net carbon exchange (NEE) ranged from −155 to −56 gC m−2 year−1 …
Journal: Agricultural And Forest Meteorology, Volume 147 (3-4): 157-171 (2007). DOI: 10.1016/j.agrformet.2007.07.008 Sites: US-Ton, US-Var
The prediction of evaporation from Mediterranean woodland ecosystems is complicated by an array of climate, soil and plant factors. To provide a mechanistic and process-oriented understanding, we evaluate theoretical and experimental information on water loss of Mediterranean oaks at three scales, the leaf, tree and woodland. …
Journal: Advances In Water Resources, Volume 30 (10): 2113-2122 (2007). DOI: 10.1016/j.advwatres.2006.06.013 Sites: US-Ton
This study proposes a new metric called canopy geometric volume G, which is derived from small-footprint lidar data, for estimating individual-tree basal area and stem volume. Based on the plant allometry relationship, we found that basal area B is exponentially related to G (B = β1G3/4, where β1 …
Journal: Photogrammetric Engineering & Remote Sensing, Volume 73 (12): 1355-1365 (2007). DOI: 10.14358/pers.73.12.1355 Sites: US-Ton
At the leaf scale, it is a long-held assumption that stomata close at night in the absence of light, causing transpiration to decrease to zero. Energy balance models and evapotranspiration equations often rely on net radiation as an upper bound, and some models reduce evapotranspiration to zero at night when there is no solar radiation. …
Journal: Tree Physiology, Volume 27 (4): 597-610 (2007). DOI: 10.1093/treephys/27.4.597 Sites: US-Ton
Filtering methods based on morphological operations have been developed in some previous studies. The biggest challenge for these methods is how to keep the terrain features unchanged while using large window sizes for the morphological opening. Zhang et al. (2003) tried to achieve this goal, but their method required the assumption …
Journal: Photogrammetric Engineering & Remote Sensing, Volume 73 (2): 175-185 (2007). DOI: 10.14358/pers.73.2.175 Sites: US-Ton