Wood Decomposition After an Aerial Application of Hydromulch Following Wildfire in a Southern California Chaparral Shrubland

Abstract

Severe wildfire can affect many soil processes, especially organic matter (OM) decomposition. Organic mulches are often applied on steep slopes to mitigate soil erosion, but little is known about how these surface organic additions affect subsequent soil OM decomposition. In 2003 the Cedar Fire burned 110,000 ha in southern California chaparral shrubland, after which hydromulch was aerially applied to reduce soil erosion. Subsequently, we established a 5-year study to assess the effect of hydromulch on OM decomposition at the burned soil surface and in the mineral soil using aspen (Populus tremuloides Michx.) and pine (Pinus taeda L.) wood stakes as standard substrates. Mass loss of both aspen and pine stakes in this dry Mediterranean ecosystem was lowest on the soil surface and increased with mineral soil depth. Decomposition was less in the hydromulched soil than in the untreated control, but the large loss of hydromulch from the soil surface within the first year after application make this result questionable. Subsequent analysis showed that subterranean termites had a major role in wood decomposition, but their variable activity in study replicates confounded the separation of hydromulch impacts on decomposition from other soil variables. Little is known on the role of termites in OM decomposition after wildfire, and they should be considered when designing studies in soils where termites are present. Our study results suggest that termite activity in mineral soil could also be a factor in root decomposition after a fire and affect soil stability on steep slopes.

Prescribed Burning Alters Insects and Wood Decay in a Sagebrush-Steppe Rangeland in Southwestern Idaho, United States

“…Similar to other studies, aspen stakes in and on this sagebrush-steppe soil generally lost mass at a faster rate than pine because aspen has lower stake cellulose:lignin and C:N ratios (Jurgensen et al 2006; Wang et al 2018). Wood decomposition in mineral soil was greater after prescribed burning than in adjacent unburned plots, and this is similar to other studies that examined wood decay following prescribed burns in forests (Page-Dumroese et al 2019) or prairie soils (O'Lear et al 1996) and after a wildfire in chaparral (Jurgensen et al 2020). There is little information on wood decay in sagebrush habitats; however, sagebrush wood can act as a sink for nutrients because of its slow decomposition rate (Rickard 1985).…”

Controls of Initial Wood Decomposition on and in Forest Soils Using Standard Material

“…We also anticipated that higher air temperature would generally lead to greater decomposition of stakes regardless of where the wood stakes are placed (Brischke and Rapp, 2008;Risch et al, 2013;Finér et al, 2016;Fissore et al, 2016), but that soil temperature would be an even better predictor than air temperature for the mineral stakes. We expected precipitation to interact with air temperature as a controlling factor for decomposition, in particular, for stakes placed at the soil surface where high precipitation and warm temperatures should speed up decomposition (Jurgensen et al, 2020). However, we also expected higher mineral stake decomposition at sites with lower precipitation, as water retention by the mineral soil becomes much more important for decomposition processes at drier sites.…”

“…Subsequent results from individual studies or regional sites showed that buried wood stakes generally decomposed faster than when put on the soil surface (Risch et al, 2013;Page-Dumroese et al, 2019;Wang et al, 2019;Jurgensen et al, 2020). Climatic properties, more specifically, higher soil temperatures, and to a lower degree higher precipitation, but not air temperature, were found to be the drivers of these differences in decomposition in Swiss subalpine forests (Risch et al, 2013).…”

“…The majority of wood decomposition studies have been conducted by placing the woody material aboveground, i.e., on top of the soil surface organic horizon (González et al, 2008;Weedon et al, 2009;Bradford et al, 2014;Liu et al, 2015;Hu et al, 2018;Lustenhouwer et al, 2020). Considerably less is known about decomposition processes of standard wood material buried belowground (e.g., Smyth et al, 2016;Erdenebileg et al, 2020;Jurgensen et al, 2020), although the volume of buried wood can contribute up to 935 m 3 ha −1 in temperate forests (Weedon et al, 2009;Moroni et al, 2015). In addition, only a few studies used standardized woody material across widely different sites to allow for a direct comparison of decomposition processes across larger scales (e.g., Reed et al, 2003;Adams et al, 2021;Page-Dumroese et al, 2021).…”

Effects of forest residue mulching on organic matter and nutrient exports after wildfire in North-Central Portugal

“…Therefore, the effects of other mulch materials with higher C:N ratios, like eucalypt bark strands, could take even longer to be perceived as they typically have lower degradation rates (Barreiro et al, 2016). The addition of mulch can induce a priming effect of soil OM, but under field conditions this effect can be difficult to identify due to a complex interplay of biotic and abiotic factors (Jurgensen et al, 2020).…”