Recipient Organization
HUMBOLDT STATE UNIV
(N/A)
ARCATA,CA 95521
Performing Department
Forestry and Wildland Resources
Non Technical Summary
Due to influences from previous forest management practices, changing climate and disturbances both natural and unnatural, California's forest resources are changing in composition and structure. For example, some private forest owners are transitioning from harvesting larger second-growth to smaller third-growth timber and public land managers are harvesting or thinning stands that were left unmanaged for decades; resulting in relatively high density and low volume per acre. In addition, much of California's forest resources are also located on steep terrain (e.g. >40% or 22°), which have greater operating costs and risks (e.g. environment and safety) associated, compared to forests on flat terrain.While the forest resources in California have changed considerably in recent decades, the harvesting systems and equipment commonly employed have changed little over the same period. Unfortunately, in many cases these conventional harvesting systems and equipment are often prohibited from working in the newer resource type, due to: physical feasibility (i.e. cannot operate on steep slopes), economic viability (i.e. are not cost-effective due to challenging work conditions) or social acceptability (i.e. present unacceptable safety risks or cause excessive soil disturbance). The result is that many areas of forest are left unmanaged, as forest management plans are deferred because the operations can't be conducted. At best, the operation can still take place, but the forests are harvested with reduced profitability to the land owner and/or optimal forest management objectives could be compromised. In recent years, there are new innovative systems and equipment that have been developed that show potential to work successfully on steep forested terrain. For example, one recent technological development is the practice of tethered (i.e. winch-assisted or cable-assisted) machines that are used for timber falling and extraction on steep ground (>35% slope).Tethered harvesting systems offer several advantages over conventional systems:Machines can travel on steep slopes while maintaining stability that were previously not physically feasible to operate machinery due to risk of sliding or rolling.Economics of the operation can be improved due to the increased system capacity (e.g. area and/or trees felled per day).Reduction in labor (i.e. one machine operator rather than several people falling trees by chainsaw).Social acceptability of operations may improve as these systems provide a safer working environment to employees and can reduce the environmental impacts from harvesting (e.g. soil disturbance associated with the use of machines, like: scarification, rutting, and compaction).While tethered timber harvesting systems have been established in British Columbia, Washington and Oregon, they have yet to be used in California, so their potential applications and benefits are not well understood in California. Successful applications in other forests suggest they might be a viable alternative to managing forests resources on steep ground in California. However,one of the main concerns of adopting this new technology, is the potential soil disturbance resulting from machines operatingon steep ground.Due to the relatively recent introduction of this type of equipment in North America, there are still many unknows surrounding this technology. Soil disturbance of various harvesting machines has been well studied over the years on flat terrain, but few research studies have investigated the soil disturbance of new tethered harvesting systems on steep terrain and none have been conducted in California forests and soil conditions.The goal of this research project is to aid forest managers and land owners to better understand the soil disturbance associated with tethered harvesting systems when used in California forests. With a better understanding of the technology, forest managers will better understand where these new types of machines are best applied; perhaps speeding the uptake of the technology. Finally, the successful adoption of this new technology has the potential to change the ecosystem health by allowing management of more acres of forest annually. The adoption of the technology could also help improve socio-economic conditions of rural forest-dependent communities in CA and the western USA, through cost savings in harvesting which make management projects feasible (e.g. fuel reduction for wildfire or restoration projects) and/or through improving profits of conventional timber harvests on steep terrain, which are currently marginal.
Animal Health Component
33%
Research Effort Categories
Basic
34%
Applied
33%
Developmental
33%
Goals / Objectives
The goal of this research project is to aid forest managers and land owners to better understand the soil disturbance associated with tethered harvesting systems when used in California forests. The specific objectives of this research project are to investigate the use of a tracked felling machine (tethered) by:Quantifying the percent of total soil disturbance (soil compaction and soil displacement) by severity classes across the harvest area.Comparing the disturbance severity between and within machine tracks.Quantifying the change in resistance to penetration and bulk density after completion of harvesting operations.
Project Methods
Soil compaction and soil displacement damage are important to understand and they influence sediment transport potential; therefore, both will be quantified during the study.Description on the study site and harvesting machines usedAn appropriate study site will be selected in collaboration with a local timberland owner and/or manager (e.g. identified research collaborator). The study site should be one that is scheduled for harvest in the dry season (May - October) and have the approval from the appropriate regulatory authorities to fell timber with a tethered machine on steep terrain; since this practice requires amending a proposed Timber Harvest Plan (THP) in the state of California.The tethered felling machine is the focus of this study and should preferably be a tracked machine with a separate base-machine as the winch anchor placed on the top of the hill. A copy of the THP will be obtained to note important site details such as but not limited to:AcresSoil types/texture & moistureGround slopesHarvesting volume/acre (MBF/acre) by delineated areaSilvicultural prescription and other important management objectivesAt the study site, the location of felling machine trails will be identified prior to or during felling operations, to implement the data collection procedure. On each machine trail studied, the felling machine will be used to fell and bunch timber for subsequent extraction by a cable yarder. The process starts with the felling machine descending a hill side from a road edge. As the felling machine traverses downslope it will fell trees to clear its path. Trees are cut and then both lifted and rotated to be placed in groups (i.e. bunched) away from the winch ropes, in an arrangement specified to facilitate cable yarding (e.g. perpendicular to the direction of extraction) of whole trees. The felling machine will work its way up and downhill felling and bunching timber until the winch anchor machine needs to be repositioned to fell trees in a new area, or simply to keep the operating ropes in as straight a lead as possible with the felling machine. After tree felling is complete, the machine will be relocated to a new stand and a cable logging crew will complete the extraction of the logging operations. The crew will consist of a cable yarder for extracting whole trees to the roadside or landing. Once the trees arrive at the roadside or landing, they are processed, where the branches are removed and the then the stems are cut to sellable log lengths (i.e. bucked). Processing is usually preformed by an excavator with specialized attachment (i.e. processing head). Finally, another excavator with log loading grapple (i.e. attachment) will load logs onto trucks for transportation to the mill (i.e. market destination).Data CollectionTotal soil percent of soil disturbance (soil compaction and soil displacement) by severity classeswill be based on a 10% sample of the area occupied by machine trails. Total bare mineral soil exposure due to soil displacement will be classified in terms of percent of the total machine trail area by visual disturbance classes similar to methods used by Evanson and others (2013) and Chase and others (2019). In addition, soil displacement depth will be measured along machine trails as described by Han and others (2006) using a rope transect and ruler. For example, a rope is strung tight between two stakes, perpendicular to the machine trail and at a height of the undisturbed soil indicating the original non-disturbed soil surface elevation; and a ruler is then held behind the rope and touching the ground to measure the displacement (i.e. rut) depth.Soil compaction will be measured by collecting soil samples at fixed locations after harvesting is complete (e.g. after the completion of tree felling and extraction by cable yarder). Sample locations will be identified and marked in the field. The experimental design will consist of three test strips of ground located along machine trails. A minimum of 30 samples will be collected from each test strip. At each sample location bulk density (Db) and resistance to penetration (RTP) samples will be collected between machine tracks (Bt), inside machine tracks (It) and outside of machine tracks (Ot), in accordance with the methodology described in Hwang et al. (2019) and Green and others (2019).Soil RTP measurements will be collected with a static cone penetrometer with needle pressure gauge. At each sample location at 10 to 50 cm depth at 10 cm intervals. Soil Db samples will be collected with a slide hammer corer and placed in plastic bags for transport from the field to the laboratory. In the laboratory, soil samples will be weighed and then oven-dried at 105 °C for 24 hours and reweighed to determine wet-based moisture content and bulk density. In addition to bulk density samples, several bulk soil samples will be collected for the purpose of determining soil type and texture.Data AnalysisTo determine the total percent area disturbed within machine trails, each machine trail length will be used as the denominator and the trail length for each disturbance severity class used as the numerator. Total harvest area disturbance will be quantified by the sum of the total disturbed areas divided by the harvest plan total area.To determine the change in soil compaction, for each machine trail, Db measurements from outside of tracks (i.e. pre-harvest condition) will be compared to inside and between track measurements (i.e. post-harvest condition).Similarly, to determine the change in soil RTP, for each machine trail, RTP measurements from outside of tracks will be compared to inside and between track measurements. Statistical analysis will be conducted using an ANOVA to determine variance between groups means, with each track position representing a group.