Mixed Hydrologic Recovery of a Degraded Mesquite Rangeland

Land degradation and anthropogenic change is widespread on rangelands in Texas. Over the last 150 years, noticeable change has occurred as a direct result of agricultural practices and human activity. As novel ecosystems and permanently altered landscapes become more common, an understanding of these new environments becomes essential. The ability of rangelands to rebound from past degradation is a factor of interest and one this study attempts to quantify. How a localized hydrologic cycle responds to disturbance can be indicative of the health of an ecosystem. This study characterized the hydrology of a mesquite rangeland at Fort Hood, Texas and assessed the current hydrologic regime compared to similar rangeland sites. The site at Fort Hood is unique because it has undergone recent high intensity vehicular traffic and low intensity grazing. Additionally, the site was cultivated until Camp Hood was established in 1942. Presented within this paper are the results of a series of seven large-scale rainfall simulations, which quantified the hydrologic variables present at the Fort Hood site. Variables of interest included infiltration, runoff, and sediment loads. Key quantitative findings of the study include: (1) Runoff values accounted for 28.7% - 64.9% of the total application of water applied to the plot. (2) Infiltration rates ranged from 15.1 mm/hr to 70.1 mm/hr at the site and (3) sediment loads ranged from 1.7 kg/ha to 4.2 kg/ha. These findings potentially indicate that the site has undergone a mixed recovery to its past hydrologic regime because erosion amounts are minimal, but infiltration rates are lower than comparable locations. This is important because it describes the ability of these landscapes to recover from past degradation

Mitigating wildfire carbon loss in managed northern peatlands through restoration

Northern peatlands can emit large amounts of carbon and harmful smoke pollution during a wildfire. Of particular concern are drained and mined peatlands, where management practices destabilize an array of ecohydrological feedbacks, moss traits and peat properties that moderate water and carbon losses in natural peatlands. Our results demonstrate that drained and mined peatlands in Canada and northern Europe can experience catastrophic deep burns (>200 t C ha(-1) emitted) under current weather conditions. Furthermore, climate change will cause greater water losses in these peatlands and subject even deeper peat layers to wildfire combustion. However, the rewetting of drained peatlands and the restoration of mined peatlands can effectively lower the risk of these deep burns, especially if a new peat moss layer successfully establishes and raises peat moisture content. We argue that restoration efforts are a necessary measure to mitigate the risk of carbon loss in managed peatlands under climate change

Severe wildfire exposes remnant peat carbon stocks to increased post-fire drying

Abstract The potential of high severity wildfires to increase global terrestrial carbon emissions and exacerbate future climatic warming is of international concern. Nowhere is this more prevalent than within high latitude regions where peatlands have, over millennia, accumulated legacy carbon stocks comparable to all human CO2 emissions since the beginning of the industrial revolution. Drying increases rates of peat decomposition and associated atmospheric and aquatic carbon emissions. The degree to which severe wildfires enhance drying under future climates and induce instability in peatland ecological communities and carbon stocks is unknown. Here we show that high burn severities increased post-fire evapotranspiration by 410% within a feather moss peatland by burning through the protective capping layer that restricts evaporative drying in response to low severity burns. High burn severities projected under future climates will therefore leave peatlands that dominate dry sub-humid regions across the boreal, on the edge of their climatic envelopes, more vulnerable to intense post-fire drying, inducing high rates of carbon loss to the atmosphere that amplify the direct combustion emissions

Impact of prescribed burning on blanket peat hydrology

Fire is known to impact soil properties and hydrological flowpaths. However, the impact of prescribed vegetation burning on blanket peatland hydrology is poorly understood. We studied ten blanket peat headwater catchments. Five were subject to prescribed burning, while five were unburnt controls. Within the burnt catchments we studied plots where the last burn occurred ∼2 (B2), 4 (B4), 7 (B7) or greater than 10 years (B10+) prior to the start of measurements. These were compared with plots at similar topographic wetness index locations in the control catchments. Plots subject to prescribed vegetation burning had significantly deeper water tables (difference in means = 5.3 cm) and greater water-table variability than unburnt plots. Water-table depths were significantly different between burn age classes (B2>B4>B7>B10+) while B10+ water tables were not significantly different to the unburnt controls. Overland flow was less common on burnt peat than on unburnt peat, recorded in 9% and 17% of all runoff trap visits, respectively. Storm lag times and hydrograph recession limb periods were significantly greater (by ∼ 1 hr and 13 hr on average, respectively) in the burnt catchments overall, but for the largest 20% of storms sampled, there was no significant difference in storm lag times between burnt and unburnt catchments. For the largest 20% of storms the hydrograph intensity of burnt catchments was significantly greater than those of unburnt catchments (means of 4.2 x10−5 s−1 and 3.4 × 10−5 s−1, respectively), thereby indicating a non-linear streamflow response to prescribed burning. Together, these results from plots to whole river catchments indicate that prescribed vegetation burning has important effects on blanket peatland hydrology at a range of spatial scales