PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Cross-site study of fine root biomass and productivity along a calcium supply gradient in north temperate forest ecosystems.
Park, Byung Bae*,1, Yanai, Ruth 1, Fahey, Timothy2, 1 SUNY Environmental Science and Forestry, Syracuse, NY, USA2 Cornell University, Itacha, NY, USA
ABSTRACT- Belowground responses to nutrient availability in forest soils are difficult to measure, but involve a large fraction of carbon allocation. We measured fine root biomass (FRB) and productivity and aboveground productivity at three-well studied sites in the northeastern US: Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. These sites are similar in climate and forest type but represent a gradient from high (Sleepers River) to low (Cone Pond) Ca supply. In each of the three sites, we measured roots in five locations in one softwood and one hardwood stand. We used root-coring techniques to estimate FRB and minirhizotron methods to monitor root dynamics. We hypothesized that sites of high soil fertility (Ca status) would have the lowest root biomass, but the highest root productivity. Across the hardwood stands, live FRB was statistically indistinguishable by site, but was highest where Ca availability was lowest, decreasing along the gradient from 682 g m-2 at Cone Pond to 465 g m-2 at Sleepers River. Softwood FRB was lowest at Hubbard Brook, which was in the middle of the Ca gradient. Fine root turnover (yr-1) varied significantly across sites. Sites fell into two very distinct groups with low (0.62 - 0.71 yr-1) and high (1.32 - 1.52 yr-1) root turnover. However, there were no differences between hardwoods and softwoods. Root turnover was independent of aboveground litter biomass, but had a weak negative correlation with FRB (<1 mm). Fine root production (biomass times turnover) ranged from 1.2 to 3.0 Mg ha-1 yr-1 for hardwood stands and from 0.9 to 2.3 Mg ha-1 yr-1 for softwood stands. Although FRB, turnover, and production were not significantly correlated to soil quality (Ca or Mg status), the ratio of root productivity to litter mass or aboveground productivity was clearly higher in sites with higher soil quality. These results suggest that greater nutrient availability leads to greater carbon allocation below ground in north temperate forest ecosystems.
Key words: fine root biomass, fine root productivity, Ca gradient, carbon allocation