PARENT SESSION
Tuesday, August 8, 5:00-6:30 pm
Poster Session 11 - Plant physiological ecology
Exhibit Hall, Ballroom Level, Cook Convention Center

Reevaluating feathermoss growth and production: a challenge to classic methods and implications for boreal carbon cycling.

Benscoter, Brian^*,1, Vitt, Dale¹, ¹ Department of Plant Biology, Carbondale, IL, USA

ABSTRACT- Feathermosses dominate the ground layer of boreal ecosystems and play a vital role in soil carbon (C) accumulation. Growth in these pleurocarpous mosses is both apical and lateral, with branches of determinate length at maturity produced at consistent frequencies along the stem. Current methods of estimating annual production of feathermosses measure the annual stem growth increment and multiply it by a species-specific bulk density (plant mass per length), which is determined by destructive sampling of the top portion of the plant. However, these methods underestimate total plant production because they do not account for lateral growth of the previous years immature branches. We present a conceptual model of feathermoss growth using Pleurozium schreberi that includes apical and lateral annual growth. From this model, we provide a modified method to more accurately measure P. schreberi production that can be calibrated for any monopodial feathermoss. The top 3-cm of ten P. schreberi plants from each of five bog peatlands in Alberta, Canada were collected. For each plant, branch insertion distance from the stem apex was measured, followed by removal of the branches and sectioning of the stem into 3-mm intervals. Branch length was measured, followed by drying and weighing of the branches and stem sections. These samples were then used to define the parameters of the proposed model. An additional 20 plants were collected from a sixth site for testing the accuracy of our modified method. Stem mass was found to be constant, as was branch frequency and branch mass per length. A logarithmic relationship between branch length and insertion distance from stem apex was found and used to define the deterministic mature branch length. These parameters were used redefine the mass per stem growth increment constant that, due to lack of significant variability among the sites in the parameters, can be applied regionally and possibly globally throughout the boreal zone. Assessment of our method showed an insignificant mean difference between observed and calculated production values. Furthermore, comparison of our method with classic methods showed a ca. 25% underestimate of annual production by the latter, significantly increasing the importance of feathermosses in the boreal C cycle.

Key words: bryology, moss production, production measurement