Abstract Detail

Ecological and evolutionary attributes of bryophytes of the boreal and arctic regions: New paradigms from interdisciplinary research

Graham, Jeremy [1], Vitt, Dale H. [2].

The importance of Sphagnum nitrogen utilization to ecosystem balance: Changes along a nutrient gradient in a boreal peatland.

Boreal bogs and poor fens are peatlands characterized by a near continuous cover of Sphagnum mosses and are abundant across the western Canadian boreal landscape. The structure and function of these systems is highly dependent by the presence and dominance of these mosses. This dependence is attributed to several key traits of Sphagnum, including; rapid nutrient uptake mechanisms, dense ground cover, unique morphologies, recalcitrant tissue, and high cation exchange capacity. As a result of these traits, bogs and poor fens accrue organic matter over the long-term and serve as large carbon stores. It has been long thought that N is the limiting factor to the productivity of these boreal systems. To examine this nutrient limitation we experimentally added NH₄⁺NO₃^- as wet deposition at several treatment levels (0, 5, 10, 15, 20, and 25 kg N ha^-1 yr^-1) for four years to a bog and poor fen-dominated by Sphagnum. We focused on growth responses and plant N concentrations of Sphagnum and ericaceous shrubs to investigate patterns of N usage. After four years of continued elevated N additions we noted two fundamental changes that hinge upon the abilities of Sphagnum. Firstly, a modification of recently documented “typical” Sphagnum capitulum growth and N usage behavior, in which capitula become smaller, less dense, and utilize little N and, secondly, a flourishing growth response of several ericaceous shrub species at levels of N additions beyond what Sphagnum is capable of retaining in its annual net primary production. The response of these shrubs to high N deposition is multifaceted, with increases shown in vascular plant abundance, above and below ground net primary production, limited luxurious N uptake, and a gradual displacement of Sphagnum individuals. Differences in decomposition rates between Sphagnum and vascular plant inputs suggest that bogs and poor fens dominated by vascular plants, rather than Sphagnum, will not be as effective as carbon sinks as those dominated by Sphagnum. The functioning of these systems is highly regulated by the capacity of Sphagnum to assimilate and store atmospherically deposited N. This is of special interest in areas faced with increasing N emissions.

1 - Southern Illinois University Carbondale, Plant Biology, 1125 Lincoln Drive, Life Science II, room 420, Carbondale, Illinois, 62901, United States
2 - Southern Illinois University, Plant Biology, Carbondale, IL, 62901, USA

Keywords:
bogs
fens
peatlands
Sphagnum
nitrogen
ecology
experimental.

Presentation Type: Symposium Presentation
Session: SY03
Location: Salon 10/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 10:45 AM
Number: SY03007
Abstract ID:154
Candidate for Awards:None