Tom Gower - Academia.edu (original) (raw)

Papers by Tom Gower

Research paper thumbnail of Serbin etal 2013 RSE Chronosequence Plot Locations

Research paper thumbnail of Effects of warming on the structure and function of a boreal black spruce forest

Research paper thumbnail of An Equilibrium Tension Lysimeter for Measuring Drainage through Soil

Soil Science Society of America Journal, 1999

ABSTRACT

Research paper thumbnail of Carbon allocation in boreal black spruce forests across regions varying in soil temperature and precipitation

Global Change Biology, 2008

Research paper thumbnail of Modeling harvest and biomass removal effects on the forest carbon balance of the Midwest, USA

Environmental Science & Policy, 2013

Research paper thumbnail of Canopy dynamics and phenology of a boreal black spruce wildfire chronosequence

Agricultural and Forest Meteorology, 2009

Research paper thumbnail of 2014 QUBES Minisymposium at the Seventh International Symposium on Biomathematics and Ecology: Education and Research

Collection of presentations that were part of a minisymposium at the Seventh International Sympos... more Collection of presentations that were part of a minisymposium at the Seventh International Symposium on Biomathematics and Ecology: Education and Research in 2014.

Research paper thumbnail of Water budget evaluation of natural and managed ecosystems employing an improved field drainage measurement technique

Publikationsansicht. 6016056. Water budget evaluation of natural and managed ecosystems employing... more Publikationsansicht. 6016056. Water budget evaluation of natural and managed ecosystems employing an improved field drainage measurement technique / (1997). Brye, Kristofor R. Abstract. Typescript.. Thesis (MS)--University of Wisconsin--Madison, 1997.. ...

Research paper thumbnail of A Global Terrestrial Monitoring Network Integrating Tower Fluxes, Flask Sampling, Ecosystem Modeling and EOS Satellite Data

Remote Sensing of Environment, 1999

Research paper thumbnail of A comparison of optical and direct methods for estimating foliage surface area index in forests

Agricultural and Forest Meteorology, 1994

Measurement of foliage surface area index (foliage SAI) is prominent in studies of terrestrial ec... more Measurement of foliage surface area index (foliage SAI) is prominent in studies of terrestrial ecosystems because it is an important determinant of water, carbon, and energy exchange at the stand, landscape, and global scales, yet is very time consuming and labor intensive to measure directly. The objectives of this study were to 1) compare the resolution and accuracy of the Ceptometer, LAI-2000, and DEMON which measure a vegetation area index (VAI; includes branches, stems, cones, etc. in addition to leaves) optically using light interception, 2) examine the utility of logarithmic versus linear averaging and a correction factor proposed by Gower and Norman (1991), and 3) determine if there is a ‘universal’ regression relating optical and direct estimates of SAI across the range of foliage areas for most North American forests (and if one exists, how it relates to individual site regressions).For our analysis, data collected in open canopy natural ponderosa pine (Pinus ponderosa Dougl. ex Laws) forests and closed canopy red pine (Pinus resinosa Ait.) plantations were combined with data from previous studies which used one or more of the instruments. We found all instruments generally underestimated SAI when compared with direct estimates. Logarithmic averages of light transmittance reduced this problem, especially for conifer forests with foliage clumped at the shoot and canopy levels. The DEMON, using logarithmically averaged data, provided the most accurate optical estimates of SAI. We did not find the clumping correction factor suggested by Gower and Norman (1991) to be useful and suggest an alternative correction technique that is based on hemisurface area index (HSAI) and includes a shoot shape factor along with a clumping factor. Across a broad range in foliage SAI, all instruments provided optical estimates of SAI that were strongly correlated to direct estimates but the optical estimates were biased. The LAI-2000 (R2 = 0.93) and the DEMON logarithmic (R2 = 0.93) had the best fits. Because of the small size of the data sets evaluated, we strongly recommend the collection of larger data sets across a wider range of foliage SAIs to better test the strength of ‘universal’ regressions relating optical estimates of SAI to direct estimates.

Research paper thumbnail of Rapid estimation of leaf area index in conifer and broad-leaf plantations

Research paper thumbnail of Carbon and nitrogen budget evaluation of natural and managed ecosystems

Research paper thumbnail of BOREAS in 1997: Experiment overview, scientific results, and future directions

Journal of Geophysical Research, 1997

The goal of the Boreal Ecosystem-Atmosphere Study (BOREAS) is to improve our understanding of the... more The goal of the Boreal Ecosystem-Atmosphere Study (BOREAS) is to improve our understanding of the interactions between the boreal forest biome and the atmosphere in order to clarify their roles in global change. This overview paper describes the science background and motivations for BOREAS and the experimental design and operations of the BOREAS 1994 and BOREAS 1996 field years. The findings of the 83 papers in this journal special issue are reviewed. In section 7, important scientific results of the project to date are summarized and future research directions are identified.

Research paper thumbnail of Forest Succession

Research paper thumbnail of Direct and Indirect Estimation of Leaf Area Index, f APAR, and Net Primary Production of Terrestrial Ecosystems

Remote Sensing of Environment, 1999

Research paper thumbnail of Leaf area index of boreal forests: Theory, techniques, and measurements

Journal of Geophysical Research, 1997

Research paper thumbnail of Characterization of the structure and function of upland forest ecosystems in north central Wisconsin

Research paper thumbnail of Serbin etal 2013 RSE Chronosequence Plot Locations

Research paper thumbnail of Effects of warming on the structure and function of a boreal black spruce forest

Research paper thumbnail of An Equilibrium Tension Lysimeter for Measuring Drainage through Soil

Soil Science Society of America Journal, 1999

ABSTRACT

Research paper thumbnail of Carbon allocation in boreal black spruce forests across regions varying in soil temperature and precipitation

Global Change Biology, 2008

Research paper thumbnail of Modeling harvest and biomass removal effects on the forest carbon balance of the Midwest, USA

Environmental Science & Policy, 2013

Research paper thumbnail of Canopy dynamics and phenology of a boreal black spruce wildfire chronosequence

Agricultural and Forest Meteorology, 2009

Research paper thumbnail of 2014 QUBES Minisymposium at the Seventh International Symposium on Biomathematics and Ecology: Education and Research

Collection of presentations that were part of a minisymposium at the Seventh International Sympos... more Collection of presentations that were part of a minisymposium at the Seventh International Symposium on Biomathematics and Ecology: Education and Research in 2014.

Research paper thumbnail of Water budget evaluation of natural and managed ecosystems employing an improved field drainage measurement technique

Publikationsansicht. 6016056. Water budget evaluation of natural and managed ecosystems employing... more Publikationsansicht. 6016056. Water budget evaluation of natural and managed ecosystems employing an improved field drainage measurement technique / (1997). Brye, Kristofor R. Abstract. Typescript.. Thesis (MS)--University of Wisconsin--Madison, 1997.. ...

Research paper thumbnail of A Global Terrestrial Monitoring Network Integrating Tower Fluxes, Flask Sampling, Ecosystem Modeling and EOS Satellite Data

Remote Sensing of Environment, 1999

Research paper thumbnail of A comparison of optical and direct methods for estimating foliage surface area index in forests

Agricultural and Forest Meteorology, 1994

Measurement of foliage surface area index (foliage SAI) is prominent in studies of terrestrial ec... more Measurement of foliage surface area index (foliage SAI) is prominent in studies of terrestrial ecosystems because it is an important determinant of water, carbon, and energy exchange at the stand, landscape, and global scales, yet is very time consuming and labor intensive to measure directly. The objectives of this study were to 1) compare the resolution and accuracy of the Ceptometer, LAI-2000, and DEMON which measure a vegetation area index (VAI; includes branches, stems, cones, etc. in addition to leaves) optically using light interception, 2) examine the utility of logarithmic versus linear averaging and a correction factor proposed by Gower and Norman (1991), and 3) determine if there is a ‘universal’ regression relating optical and direct estimates of SAI across the range of foliage areas for most North American forests (and if one exists, how it relates to individual site regressions).For our analysis, data collected in open canopy natural ponderosa pine (Pinus ponderosa Dougl. ex Laws) forests and closed canopy red pine (Pinus resinosa Ait.) plantations were combined with data from previous studies which used one or more of the instruments. We found all instruments generally underestimated SAI when compared with direct estimates. Logarithmic averages of light transmittance reduced this problem, especially for conifer forests with foliage clumped at the shoot and canopy levels. The DEMON, using logarithmically averaged data, provided the most accurate optical estimates of SAI. We did not find the clumping correction factor suggested by Gower and Norman (1991) to be useful and suggest an alternative correction technique that is based on hemisurface area index (HSAI) and includes a shoot shape factor along with a clumping factor. Across a broad range in foliage SAI, all instruments provided optical estimates of SAI that were strongly correlated to direct estimates but the optical estimates were biased. The LAI-2000 (R2 = 0.93) and the DEMON logarithmic (R2 = 0.93) had the best fits. Because of the small size of the data sets evaluated, we strongly recommend the collection of larger data sets across a wider range of foliage SAIs to better test the strength of ‘universal’ regressions relating optical estimates of SAI to direct estimates.

Research paper thumbnail of Rapid estimation of leaf area index in conifer and broad-leaf plantations

Research paper thumbnail of Carbon and nitrogen budget evaluation of natural and managed ecosystems

Research paper thumbnail of BOREAS in 1997: Experiment overview, scientific results, and future directions

Journal of Geophysical Research, 1997

The goal of the Boreal Ecosystem-Atmosphere Study (BOREAS) is to improve our understanding of the... more The goal of the Boreal Ecosystem-Atmosphere Study (BOREAS) is to improve our understanding of the interactions between the boreal forest biome and the atmosphere in order to clarify their roles in global change. This overview paper describes the science background and motivations for BOREAS and the experimental design and operations of the BOREAS 1994 and BOREAS 1996 field years. The findings of the 83 papers in this journal special issue are reviewed. In section 7, important scientific results of the project to date are summarized and future research directions are identified.

Research paper thumbnail of Forest Succession

Research paper thumbnail of Direct and Indirect Estimation of Leaf Area Index, f APAR, and Net Primary Production of Terrestrial Ecosystems

Remote Sensing of Environment, 1999

Research paper thumbnail of Leaf area index of boreal forests: Theory, techniques, and measurements

Journal of Geophysical Research, 1997

Research paper thumbnail of Characterization of the structure and function of upland forest ecosystems in north central Wisconsin