A detrimental soil disturbance prediction model for ground-based timber harvesting

Soil properties and forest productivity can be affected during ground-based harvest operations and site preparation. The degree of impact varies widely depending on topographic features and soil properties. Forest managers who understand site-specific limits to ground-based harvesting can alter harvest method or season to limit soil disturbance. To determine the potential areal extent of detrimental (potentially plant growth limiting) soil disturbance based on site characteristics and season of harvest, we developed a predictive model based on soil monitoring data collected from 167 groundbased harvest units. Data collected included dominant site parameters (e.g., slope, aspect, soil texture, and landtype), harvest season, harvest type (intermediate or regeneration), and the machine(s) used during ground-based harvest operations. Aspect (p = 0.0217), slope (p = 0.0738), landtype (p = 0.0002), and the interaction of harvest season × landtype (p = 0.0002) were the key variables controlling the areal extent and magnitude of detrimental soil disturbance. For example, harvesting during non-winter months on gently rolling topography resulted in greater soil disturbance than similar harvest operations on landscapes that are highly dissected. This is likely due to the ease with which equipment can move off designated trails. A geospatially explicit predictive model was developed using general linear model variables found to significantly influence the areal extent of detrimental soil disturbance on nine defined landtypes. This tool provides a framework that, with local calibration, can be used on other forest lands as a decision support tool to geospatially depict landtypes susceptible to detrimental soil disturbance during ground-based harvest operations. Les opérations de récolte et de préparation de terrain qui se déroulent sur le terrain peuvent avoir un impact sur les propriétés du sol et la productivité de la forêt. L’ampleur de l’impact varie énormément selon les caractéristiques topographiques et les propriétés du sol. Les aménagistes qui comprennent les limites inhérentes à chaque station pour la récolte sur le terrain peuvent modifier les méthodes de coupes ou la saison de récolte afin de minimiser la perturbation du sol. Pour déterminer l’étendue aréale potentielle des perturbations néfastes (qui peuvent limiter la croissance des plantes) du sol selon les caractéristiques de la station et la saison de récolte, nous avons élaboré un modèle de prédiction basé sur des données de suivi du sol collectées dans 167 unités de récolte sur le terrain. Les données qui ont été recueillies incluaient les principaux paramètres de la station (p. ex. pente, exposition, texture du sol et type de sol), la saison de récolte, le type de coupe (intermédiaire ou de régénération) et la machinerie utilisée lors des opérations de récolte sur le terrain. L’exposition (p = 0,0217), la pente (p = 0,0738), le type de sol (p = 0,0002) et l’interaction entre la saison de récolte et le type de sol (p = 0,0002) étaient les principales variables responsables de l’étendue et de l’ampleur des perturbations néfastes du sol. Par exemple, le fait de récolter à d’autres moments que pendant les mois d’hiver sur un relief vallonné perturbait davantage le sol que les mêmes opérations de récolte dans des paysages fortement disséqués. Cela est probablement dû à la facilité avec laquelle la machinerie peut s’écarter des sentiers désignés. Un modèle de prédiction géospatialement explicite a été développé à l’aide des variables du modèle linéaire général qui avaient une influence significative sur l’étendue aréale des perturbations néfastes du sol pour neuf types de sol caractéristiques. Cet outil procure un cadre qui, après une calibration locale, peut être utilisé sur d’autres territoires forestiers comme outil d’aide à la décision pour représenter géospatialement les types de sol sensibles aux perturbations néfastes du sol lors d’opérations de récolte qui se déroulent sur le terrain

Contribution of actinorhizal shrubs to site fertility in a Northern California mixed pine forest

Bitterbrush (Purshia tridentata) and mahala mat (Ceanothus prostratus) are common N-fixing shrubs in interior forests of the western United States, yet their contribution to ecosystem N pools is poorly characterized. We compared N fixation and soil N accretion by these shrubs in old-growth ponderosa pine (Pinus ponderosa)-Jeffrey pine (Pinus jeffreyi) stands versus stands that had been harvested 50 years earlier. No differences (α = 0.10) in cover, biomass, or percent N derived from fixation by bitterbrush or mahala mat were found between harvested and uncut stands. Approximately 46% of bitterbrush N was derived from symbiotic N fixation as measured by the 15N natural abundance method. No accurate measure of percent N derived from fixation was attained for mahala mat using this technique due to the absence of a well-matched reference plant. Estimates of total N fixation rates in both stand types were 0.2 kg ha-1 year-1 for bitterbrush and 0.3 kg ha-1 year-1 or less for mahala mat. No appreciable soil N accretion resulted due to the presence of bitterbrush or mahala mat in either stand type. Nitrogen addition by these shrubs, although small, accounts for 10-60% of annual N input in these dry forest ecosystems. © 2007 Elsevier B.V. All rights reserved

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

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

Termite Feeding on Aspen and Pine Stakes on a High Elevation Sagebrush-Steppe Rangeland in Southeastern Idaho

An indigenous subterranean termite, Reticulitermes tibialis Banks, fed on quaking aspen (Populus tremuloides Michx.) and loblolly pine (Pinus taeda L.) stakes in prescribed burn and non-burned field plots on an established sagebrush-steppe rangeland restoration study site on Red Mountain, southeastern Idaho, expanding the known distribution of the \u27arid-land subterranean termite\u27 species. Aspen and pine stakes in the plots as part of a 5-year wood-decay study were unexpectedly damaged by termites. Groups of 25, 15-cm-long stakes were placed horizontally on the soil surface, and groups of 25, 20-cm-long stakes were vertically inserted to a depth of 20 cm into the soil. Aspen stakes were more damaged by feeding termites than were pine stakes. Stakes inserted into soil sustained greater termite feeding and decay damage compared with stakes on the soil surface. During the first 4 years of the study, wood mass loss caused by termite feeding on stakes exceeded loss from decay. Losses from termite feeding and microbial decay were similar by the 5thyear. Differences in termite feeding damage on aspen stakes were compared with pine stakes in prescribed burn and non-burned plots. Stakes in prescribed burn plots had more mass loss than those in non-burned plots

Linkages between grazing history and herbivore exclusion on decomposition rates in mineral soils of subalpine grasslands

Background & aims Herbivore-driven changes to soil properties can influence the decomposition rate of organic material and therefore soil carbon cycling within grassland ecosystems. We investigated how aboveground foraging mammalian and invertebrate herbivores affect mineral soil decomposition rates and associated soil properties in two subalpine vegetation types (short-grass and tall-grass) with different grazing histories. Methods Using exclosures with differing mesh sizes, we progressively excluded large, medium and small mammals and invertebrates from the two vegetation types in the Swiss National Park (SNP). Mineral soil decomposition rates were assessed using the cotton cloth (standard substrate) method between May and September 2010. Results Decomposition displayed strong spatio-temporal variability, best explained by soil temperature. Exclusion of large mammals increased decomposition rates, but further exclusion reduced decomposition rates again in the lightly grazed (tall-grass) vegetation. No difference among treatments was found in the heavily grazed (short-grass) vegetation. Heavily grazed areas had higher decomposition rates than the lightly grazed areas because of higher soil temperatures. Microbial biomass carbon and soil C:N ratio were also linked to spatio-temporal decomposition patterns, but not to grazing history. Conclusions Despite altering some of the environmental controls of decomposition, cellulose decomposition rates in the SNP’s subalpine grasslands appear to be mostly resistant to short-term herbivore exclusion.ISSN:0032-079XISSN:1573-503

Response of a subalpine grassland to simulated grazing: aboveground productivity along soil phosphorus gradients

Interactions between grassland ecosystems and vertebrate herbivores are critical for a better understanding of ecosystem processes, but diverge widely in different ecosystems. In this study, we examined plant responses to simulated red deer ( Cervus elaphus L.) grazing using clip-plot experiments in a subalpine grassland ecosystem of the Central European Alps. We measured aboveground net primary production (ANPP) and phosphorus (P) concentration of leaf tissue from plants of two vegetation types with different grazing history. The experimental plots were placed on a soil-P gradient and subject to two different clipping treatments, which simulated moderate and heavy grazing, respectively. We found distinct differences in the response of both ANPP and P concentration in leaf tissues in the two vegetation types. Compared to moderate, heavy grazing simulation did not affect ANPP in the vegetation type adapted to grazing, but decreased ANPP in the non-grazing adapted vegetation type. High soil-P levels also had different effects on the response of the vegetation to clipping in the two vegetation types with different grazing history. ANPP correlated positively with soil-P in non-grazing adapted tall-grass vegetation, while in grazing adapted short-grass vegetation a positive relationship between soil-P and the P concentration in leaf tissues was found. Our experiments provide data for a better understanding of ecosystem processes in high-elevation grasslands of the Alps with possible implications for both nature conservation purposes in protected areas and the management of agriculturally used grasslands

Size-dependent loss of aboveground animals differentially affects grassland ecosystem coupling and functions

Defaunation can have impacts on ecosystem functioning that are currently little understood. Using an exclusion experiment, Risch et al. show the impacts of vertebrate and invertebrate losses on ecosystem coupling, particularly emphasising the role of invertebrates in ecosystem functioning

Decomposition of wood stakes in the Pacific Northwest after soil compaction and organic matter removal

Forest operations can affect soil productivity by impacting the amount and distribution of surface organic matter (OM) and changing the properties of surface mineral soil. The North American Long-Term Soil Productivity Study (LTSP) was developed to address such long-term changes after pulse disturbances associated with clearcut harvesting, soil compaction, and OM removal across a wide spectrum of forest sites. From 2000 to 2002 we established a study to assess the impact of four soil disturbance treatments on OM decomposition in the mineral soil on seven LTSP study plots from southern British Columbia, Canada to southern Oregon, USA. The soil treatments were combinations of two levels of compaction and organic matter removal: 1) removal of only merchantable logs [OM0], 2) removal of all the forest floor and woody material [OM2], 3) no soil compaction after harvest [C0], and 4) “severe” soil compaction after harvest [C2]. Aspen (Populus tremuloides Michx.) and pine (Pinus taeda L.) wood stakes were inserted into the mineral soil of each treatment plot and in an adjacent unharvested control stand to a depth of either 20 or 30 cm (depending on soil depth). At the end of three years the soil compaction and the OM removal treatments had relatively little effect on pine or aspen stake decomposition at the British Columbia study sites. In the United States, soil compaction increased decomposition on the two study sites with coarse-texture mineral soil with surface OM intact. Three key findings were: (1) a strong positive relationship (p = 0.0009) between stake water content and stake mass loss, (2) aspen and pine stake decomposition was greater in the clearcut-LTSP treatments than in the unharvested stands, (3) the rehabilitation of the compacted soil treatment on the British Columbia study sites generally increased wood stake decomposition. However, overall, there were no consistent wood stake decay trends across all sites and LTSP treatments