Background/Question/Methods
The combined study of community structure, environmental gradients, ecosystem response, and plant functional traits measured in the lab contribute to an emerging field of functional ecology showing promise for forecasting. However, we have a nascent understanding of drivers behind physiologic trait patterns in nature, in particular, eco-hydrologic traits of wetland bryophytes. We asked if species traits associated with water relations link to ecosystem response, bryophyte community structure, and hydrology in a sub-alpine fen in the western Cascades of Oregon, U.S.A.? Growth and reproduction of bryophytes depend on the quantity of external water held, which varies by species. Wetlands provide a soil substrate that supplies either an unlimited amount of water, or at minimum, a shallow water table for part of the year.  We measured bryophyte and vascular plant community structure in bryophyte-dominated fen for three years. We scored resident bryophyte species for morphological, anatomical, and lab-measured physiologic traits associated with water relations. We measured environmental gradients including hydrology during the study period.
Results/Conclusions
We hypothesized and confirmed that external water holding capacity of bryophyte species (measured in the laboratory) corresponded to bryophyte community structure along a hydrology gradient in the wetland.  Our results also demonstrated that water holding capacity of bryophyte species can be aggregated to the level of the wetland ecosystem to reveal an emergent community property, water holding capacity of the living portion of the bryophyte mat. Our work supported the theory by Paul Keddy (1999) that co-occurring organisms can show similarity in resource acquisition along gradients of resource limitation. Dominance of bryophyte species can be linked to species-specific traits facilitating resource acquisition such as water when the water table is below the surface but in capillary contact. We promote conceptual frameworks that incorporate traits of plant species such as bryophytes for understanding and predicting both community composition and ecological response such as water holding capacity in peatlands.