Modelling Carbon Emissions in <i>Calluna vulgaris</i>–Dominated Ecosystems when Prescribed Burning and Wildfires Interact

<div><p>A present challenge in fire ecology is to optimize management techniques so that ecological services are maximized and C emissions minimized. Here, we modeled the effects of different prescribed-burning rotation intervals and wildfires on carbon emissions (present and future) in British moorlands. Biomass-accumulation curves from four <i>Calluna</i>-dominated ecosystems along a north-south gradient in Great Britain were calculated and used within a matrix-model based on Markov Chains to calculate above-ground biomass-loads and annual C emissions under different prescribed-burning rotation intervals. Additionally, we assessed the interaction of these parameters with a decreasing wildfire return intervals. We observed that litter accumulation patterns varied between sites. Northern sites (colder and wetter) accumulated lower amounts of litter with time than southern sites (hotter and drier). The accumulation patterns of the living vegetation dominated by <i>Calluna</i> were determined by site-specific conditions. The optimal prescribed-burning rotation interval for minimizing annual carbon emissions also differed between sites: the optimal rotation interval for northern sites was between 30 and 50 years, whereas for southern sites a hump-backed relationship was found with the optimal interval either between 8 to 10 years or between 30 to 50 years. Increasing wildfire frequency interacted with prescribed-burning rotation intervals by both increasing C emissions and modifying the optimum prescribed-burning interval for minimum C emission. This highlights the importance of studying site-specific biomass accumulation patterns with respect to environmental conditions for identifying suitable fire-rotation intervals to minimize C emissions.</p></div

Locations of the four heath/moorland study sites in Great Britain.

<p>Geographic coordinates for Kerloch: 56°58’N, 2°30’W; Moor House: 54°41’N, 2°24’W; Howden: 53°28’N, 1°42’W; and Dorset: 50°43’N, 2°07’W.</p

Modelled carbon loss for four sites across Great Britain over a 200-year period with respect to prescribed-burning rotation interval and subjected to an additional wildfire at 50-year, 100-year and 200-year return intervals.

<p>Modelled carbon loss for four sites across Great Britain over a 200-year period with respect to prescribed-burning rotation interval and subjected to an additional wildfire at 50-year, 100-year and 200-year return intervals.</p

Modelled annual carbon loss due to prescribed burns (C_lossPBA) for four different sites across Great Britain under varying rotation intervals.

<p>Modelled annual carbon loss due to prescribed burns (C_lossPBA) for four different sites across Great Britain under varying rotation intervals.</p

C emissions over 200 years (Closs_PB200) at different wildfire return intervals in the absence of prescribed burning (t ha^-1).

<p>C emissions over 200 years (Closs_PB200) at different wildfire return intervals in the absence of prescribed burning (t ha^-1).</p

Modelled annual carbon loss at different prescribed burns rotation intervals for four different sites across Great Britain under varying combustion completeness (CC) scenarios.

<p>Modelled annual carbon loss at different prescribed burns rotation intervals for four different sites across Great Britain under varying combustion completeness (CC) scenarios.</p

Optimal prescribed burning rotation interval where C emissions over 200 years (C_lossPB200) are minimized.

<p>These optimal rotation intervals are calculated including the incidence of wildfires at three different return intervals 50, 100 and 200 years.</p