Methods to Reduce Forest Residue Volume After Timber Harvesting and Produce Black Carbon

Hindawi Scientiﬁca Volume 2017, Article ID 2745764, 8 pages https://doi.org/10.1155/2017/2745764 Research Article Methods to Reduce Forest Residue Volume after Timber Harvesting and Produce Black Carbon Deborah S. Page-Dumroese,1 Matt D. Busse,2 James G. Archuleta,3 Darren McAvoy,4 and Eric Roussel5 1 USDA FS, Rocky Mountain Research Station, 1221 S. Main, Moscow, ID 83843, USA 2USDA FS, Pacific Southwest Research Station, 1731 Research Park Dr., Davis, CA 95618, USA 3USDA FS, Umatilla National Forest, 72510 Coyote Rd, Pendleton, CA 97801, USA 4Utah State University, 5230 Old Main Hill, Logan, UT 84332, USA 5Nevada Division of Forestry, 2478 Fairview Drive, Carson City, NV 89701, USA Correspondence should be addressed to Deborah S. Page-Dumroese; [email protected] Received 16 December 2016; Accepted 21 February 2017; Published 9 March 2017 Academic Editor: Artemi Cerda Copyright © 2017 Deborah S. Page-Dumroese et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Forest restoration often includes thinning to reduce tree density and improve ecosystem processes and function while also reducing the risk of wildfire or insect and disease outbreaks. However, one drawback of these restoration treatments is that slash is often burned in piles that may damage the soil and require further restoration activities. Pile burning is currently used on many forest sites as the preferred method for residue disposal because piles can be burned at various times of the year and are usually more controlled than broadcast burns. In many cases, fire can be beneficial to site conditions and soil properties, but slash piles, with a large concentration of wood, needles, forest floor, and sometimes mineral soil, can cause long-term damage. We describe several alternative methods for reducing nonmerchantable forest residues that will help remove excess woody biomass, minimize detrimental soil impacts, and create charcoal for improving soil organic matter and carbon sequestration. 1. Introduction to reduce wildfire were estimated to be approximately 0.2 millionmetrictonsannuallyintheforestsofSouthern Many forest stands in the western United States are in need California and were expected to increase to 1,500 metric tons of restoration for a variety of attributes (e.g., fire regimes per day [5]. To reduce the risk of wildfire, residues are often or watershed health) after 100 years of fire suppression, removed and transported to a bioenergy facility, dispersed selective harvesting, or livestock grazing [1–3]. Although across the harvest site by masticating or grinding them, or there is broad agreement that some form of restoration of fire piled and burned [6, 7]. regimes, habitat, fish, and wildlife populations, or disturbance Slashpileburningcanbeaneconomicalmethodfor patterns is necessary in many areas of the western United disposing of harvest residues on National Forests following States [4], there is disagreement about the objectives and timber harvesting operations [8] and an effective method for implementation strategies [3]. In this paper we will consider reducing the volume of unmerchantable material. However, slash disposal activities resulting from thinning operations theimpactofpileburningonsoilprocessesishighlyvariable thatareusedtoreducethevolumeofstandingtimberon and can result in either relatively small impacts for a short a site. Stand density restoration activities usually involve period of time or long-term residual soil damage [9], but the cutting and removing small trees with little merchantable ecological impacts are not well understood [2, 10, 11]. The value [3]. Residues created from thinning activities designed high variability of soil impacts from pile burning impacts 2 Scientifica Table 1: Mean slash pile size, soil moisture, and resulting changes in soil properties to a depth of 30 cm after slash piling burning in two seasons on two soil textures relative to the control, unburned soil at the Lubrecht Experimental Forest, Montana. Soil moisture Pile size pH OM C N Soil texture Burn season % Mg % change from unburned Spring 16.7 7.2 +9 −49 −50 −56 Coarse Fall 11.8 9.8 +25 −64 −57 −63 Spring 30.0 9.6 +9 +10 +18 +17 Fine Fall 12.6 5.6 +12 −39 −25 −3 can be attributed to differences in soil texture, fuel type Because slash is concentrated into piles, heat is concen- and loading, soil moisture, and weather conditions during trated into a small area where it can alter soil structure burning (e.g., [12–14]). Often, slash piles leave only localized [12], infiltration [18], nutrient cycling [19], soil pH [20], and soil impacts; however depending on postharvest woody microbial populations [21]. Pile burning can also impact residue abundance, pile size, amount, and type of fuel in understory plants, seedbanks, and water holding properties the piles, soil type, fire duration, and the distribution of [2, 22, 23]. Many studies suggest that pile burning occur piles within an activity area larger-scale impacts are possible when soils are moist to limit detrimental soil heating [11, 13], [2, 15]. Alternatives to slash pile burning are limited and despite the potential for biological damage that can result broadcast burning is often restricted by weather conditions, from burning piles when the soil is moist [24–26]. stand species composition, availability of expert fire crews, or When slash piles are built using a bulldozer they are often air quality regulation that limit seasonal burning. Some areas a mixture of dense fuels, mineral soil, and surface organic arenotsuitedforpileorbroadcastburningandtherefore, horizons [13, 27]. Once ignited, the piles often burn very mastication (reducing the size of woody residues) is gaining hot for an extended period of time [27] and can produce popularity in many areas because it can be less expensive than long-term soil impacts. Pile size also plays a key role in burning. However, it does not remove fuels, it just rearranges soil impacts [14]. Season of burning and under-pile soil them [16]. moisture and texture will alter the extent of impacts (Table 1). We briefly discuss the impacts of slash piles, how slash In northwestern Montana, for example, spring burning of piles are currently built, and then discuss alternative methods grappler-built slash piles on fine-textured soil resulted in for using waste woody residues to create biochar. Our paper is increases in soil organic matter, carbon, and nitrogen. Fall designed to provide information on the usefulness of making burning of grappler-built piles when soil moisture was low and applying biochar (or black carbon), purposefully made resulted in loss of more than half of the organic matter, charcoal for land application. Purposeful biochar applica- carbon, and nitrogen. There are methods to restore burn scars tions can be a vehicle for carbon sequestration made from (e.g., wood chip mulches or soil scarification) [7, 28], but renewable and sustainable woody biomass, but it can also help these efforts also add to overall increased site preparation improve soil conditions by improving soil water and nutrient costs. holding capacity [11]. 3. Current Pile Construction Techniques 2. Slash Pile Impacts Slash piles are currently used as the preferred method for Determining the impacts of pile burning on soil health is residuedisposalbecausetheycanbeburnedatvarioustimes complex because of the wide variability in how piles are of the year, offer a larger margin of safety, and are relatively constructed and distributed within a harvest area, amount effective at removing woody residues. Pile burning has been of biomass to dispose, piling method, species composition, used for many years and is often the preferred method to andpilelocation.Inaddition,soilisnotaparticularly reduceharvest-generatedslash.Pilescanbeconstructedin goodconductorofheatowingtoitshighinternalporosity a variety of ways, by hand, bulldozer, excavator (grappler), [17]. For example, hand-built pile coverage in a Lake Tahoe or log loaders. In Table 2 we describe several strengths and Basin study ranged from 2% to over 30% within thinning weaknesses of slash pile burning. units [7]. In northeastern Oregon, estimates for whole tree yarding and bulldozer-built piles are one on 4 ha (10 acres) 3.1. Hand Piles. Typically these piles are a loose stack of wood while processing trees within a harvest area may result in built by placing one piece of wood onto the pile at a time. one bulldozer-built or hand-built pile in every 0.4 ha (1 ac; Nocareistakentoelevatethepilefromtheground,but personal communication; Kristin Marshall, Assistant Fire typically the pile rests on a few supporting branches that Management Officer, Umatilla National Forest, Heppner, elevate the pile. There is also little effort to densify the pile OR). Commonly, harvest units have less than 15% pile during construction; leaving many air voids. In some cases coverage (median of 8%) and the actual ground coverages are hand piles do not create detrimental soil impacts as a result highly correlated with the level of basal area reduction [8]. of heating or the act of building the pile [8, 29], but if soil Scientifica 3 Table 2: Strengths and weaknesses of slash pile burning. Strengths Weaknesses Soil heating damage; changes in chemical, physical, and/or biological Widely used for many years properties Easily controlled fire Smoke, greenhouse gases, and particulates released

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