Brian W. Benscoter

Global vulnerability of peatlands to fire and carbon loss

The amount of carbon stored in peats exceeds that stored in vegetation. A synthesis of the literature suggests that smouldering fires in peatlands could become more common as the climate warms, and release old carbon to the air.

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release w ...

Moderate drop in water table increases peatland vulnerability to post-fire regime shift

Northern and tropical peatlands represent a globally significant carbon reserve accumulated over thousands of years of waterlogged conditions. It is unclear whether moderate drying predicted for northern peatlands will stimulate burning and carbon losses as has occurred in their smaller tropical counterparts where the carbon legacy has been destabilized due to severe drainage and deep peat fires. Capitalizing on a unique long-term experiment, we quantify the post-wildfire recovery of a northern peatland subjected to decadal drainage. We show that the moderate drop in water table position predicted for most northern regions triggers a shift in vegetation composition previously observed within only severely disturbed tropical peatlands. The combined impact of moderate drainage followed by wildfire converted the low productivity, moss-dominated peatland to a non-carbon accumulating shrub-grass ecosystem. This new ecosystem is likely to experience a low intensity, high frequency wildfire regime, which will further deplete the legacy of stored peat carbon.

Post-fire bryophyte establishment in a continental bog

Abstract Questions: What is the mechanism of bog ground layer colonization post-fire? Is species colonization stochastic or does facilitation occur? Location: Boreal bog peatland near Crow Lake, Alberta, Canada. Methods: Diaspore-addition treatments were applied in 2003 to autoclaved peat samples from high and low microtopographic positions within a recently burned bog. Colonization was assessed within the plots in 2005 and compared to control plots to determine treatment success and patterns of colonization. Results: A significant degree of ground layer colonization was found two years after fire, with Polytrichum strictum dominating the site. Colonization was greater in low (wet) plots, although only P. strictum and Sphagnum angustifolium had significant colonization. No effect of diaspore addition was observed and Sphagnum was only found in conjunction with P. strictum. Conclusions: Environmental conditions and species life history strategy are more important than diaspore availability for post-fire colonization. True mosses (e.g. P. strictum) appear to facilitate Sphagnum colonization. Nomenclature: Vitt et al. 1988.

Shifts in pore connectivity from precipitation versus groundwater rewetting increases soil carbon loss after drought

Droughts and other extreme precipitation events are predicted to increase in intensity, duration, and extent, with uncertain implications for terrestrial carbon (C) sequestration. Soil wetting from above (precipitation) results in a characteristically different pattern of pore-filling than wetting from below (groundwater), with larger, well-connected pores filling before finer pore spaces, unlike groundwater rise in which capillary forces saturate the finest pores first. Here we demonstrate that pore-scale wetting patterns interact with antecedent soil moisture conditions to alter pore-scale, core-scale, and field-scale C dynamics. Drought legacy and wetting direction are perhaps more important determinants of short-term C mineralization than current soil moisture content in these soils. Our results highlight that microbial access to C is not solely limited by physical protection, but also by drought or wetting-induced shifts in hydrologic connectivity. We argue that models should treat soil moisture within a three-dimensional framework emphasizing hydrologic conduits for C and resource diffusion.The impacts of top down (precipitation) and bottom-up (groundwater rise) wetting processes on carbon sequestration are poorly understood. Here, the authors use incubation experiments to show that drought legacy and pore-scale wetting patterns are important factors controlling short-term carbon dynamics.

The effect of long-term drying associated with experimental drainage and road construction on vegetation composition and productivity in boreal fens

Land-use and climate change are expected to cause drying of vegetation and surface soils in continental boreal peatlands. We examined the effects of multi-decadal drying and drainage on plant community structure and productivity in four fens located in Alberta, Canada. Long-term drying resulted in a two to fourfold increase in total biomass in three of the four fen sites, with a similar large increase in NPP in Treed Fen 1. The treed poor fens consistently had decreased moss cover and productivity with drainage. Across all sites, changes in understory community composition were related to the change in water table position as well as overstory canopy development that occurred post-drainage. Overall, drainage induced a shift toward a drier peatland regime, favoring increased canopy and vascular plant density at the expense of ground-layer mosses or the understory. Within the ground layer communities, drainage favored dry-adapted hummock moss and lichen species over those wet-adapted but dessication-prone species typical of low-lying lawns and hollows. Alteration of fen vegetation due to ecosystem drying will not only influence carbon sequestration but also will increase the vulnerability of peatlands to wildfire, increasing the risk of further ecosystem degradation and possible loss of resilience.

Non-Destructive Estimation of Aboveground Biomass in Sawgrass Communities of the Florida Everglades

The preservation, restoration, and management of ecologically sensitive wetland plant communities, such as found in the Florida Everglades, require methods to reliably and non-destructively assess their health and performance. The pin-intercept method is a technique commonly used in grasslands for non-destructively estimating aboveground plant biomass. In this study, we developed an algorithm for the estimation of aboveground sawgrass biomass using coupled pin-intercept and harvest methods at A.R.M. Loxahatchee National Wildlife Refuge. Our data illustrates a positive relationship between aboveground biomass and the frequency of pin-intercepts as well as leaf area for sawgrass (Cladium mariscus). This pin-intercept method will serve as an effective, reliable tool for conservation and land management efforts in graminoid-dominated wetlands.