Contrasting fine-root production,survival and soil CO2 efflux in pine and poplar plantations |
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Authors: | Coleman M D Dickson R E Isebrands J G |
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Institution: | (1) North Central Research Station, Forestry Sciences Laboratory, USDA Forest Service, Rhinelander, WI 54501, USA;(2) Present address: Savannah River Institute, USDA Forest Service, New Ellenton, SC, 29809, USA. Corresponding author;(3) North Central Research Station, Forestry Sciences Laboratory, USDA Forest Service, Rhinelander, WI 54501, USA |
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Abstract: | Tree root activity, including fine-root production, turnover and metabolic activity are significant components of forest productivity
and nutrient cycling. Differences in root activity among forest types are not well known. A 3-year study was undertaken in
red pine (Pinus resinosa Ait.) and hybrid poplar (Populus tristis X P. balsamifera cv `Tristis no. 1') plantations to compare belowground root dynamics. We measured fine-root production, mortality and standing
crop, as well as soil CO2 efflux. Pine fine-root production was only 2.9% of that of poplar during three years; 85 pine roots were observed in minirhizotron
tubes compared with 4088 poplar roots. Live-root density oscillated seasonally for both species with late winter minimum and
autumn maximum. Poplar reached constant maximum live-root length within the first growing season, but pine continued to increase
observed fine-root length for three growing seasons. Within the first 100 days following initial appearance, 22% of the pine
roots disappeared and 38% of the poplar roots disappeared. Median fine-root longevity of pine was 291 days compared with 149
days for poplar roots. Fine-root longevity increased with depth in the soil, and was greater for roots with initial diameter
>0.5 mm. The probability of poplar root death from late February to May was more than three times that in any other season,
regardless of root age. Despite the greater poplar root production and live-root length, fine-root biomass and soil CO2 efflux was greater in pine. Greater metabolic activity in the pine stand may be due to greater fine-root biomass or greater
heterotrophic respiration.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | fine-root turnover hybrid poplar minirhizotron red pine soil respiration |
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