managing for sustainable site productivity: weyerhaeuser's forestry perspective

Pergamon Bioma.s.s und Bioenerg~ Vol. 13, Nos. 4,‘5, pp. 255-267. 1997

c 1998 Published by Elsevier Science Ltd. All rights reserved Prlnted III Great Britain

PII: SO961-9534(97)10013-7 0961-9534197 $17.00 + 0.00

MANAGING FOR SUSTAINABLE SITE PRODUCTIVITY: WEYERHAEUSER’S FORESTRY PERSPECTIVE

RONALD L. HENINGER*. THOMAS A. TERRY, ALEX DOBKOWSKI and WILLIAM SCOTT

Weyerhaeuser Company, Western Forestry Research. 505 North Pearl St., Centralia, WA 9853 I, U.S.A.

Abstract-Weyerhaeuser Company is committed to being a responsible steward of the environmental quality and economic value of the forests we manage. Weyerhaeuser’s regional Forest Councils have developed specific resource strategies for forest products. water quality, wildlife habitat, soil productivity and aesthetics. The sustainable site productivity or soil productivity strategy is as follows: “We protect soil stability and ensure long-term soil productivity by: (I) using equipment and practices appropriate to the soil, topography and weather to minimize erosion and harmful soil disturbance, and (2) using forestry practices and technology to retain organic matter and soil nutrients.” The elements of the Weyerhaeuser reliable processes used to achieve this strategy in the Northwest, U.S.A. include (I) a research database; (2) common goals and standards leading to management guidelines; (3) education, training and teaming across the organization; (4) implementation of Best Management Practices (BMPs): (5) monitoring of performance and (6) adaptive experimentation. This is not a static process-- continuous improvement is a design element in the process. Guidelines and BMPs have been developed to minimize detrimental soil disturbance. This was accomplished by having (I) a strategic database on soil disturbance impacts; (2) a classification system that describes soil disturbance classes; (3) a soil operability risk rating system that rates soils on their susceptibility to compaction and puddling; and (4) a close working relationship between R and D and operations to develop BMPs. Steps are being taken to develop organic matter management guides for various soil groups and a soil nutrient risk-rating system. These combined with fertilizer guides will lead to practices that conserve and strive to maintain organic matter and soil nutrients. Education and training of employees is an important step in implementing the guides and BMPs. Operational practices are monitored to assess performance against specified standards. Identification of knowledge gaps lead to additional research and operational adaptive trials. Based on new research information, operational experiences and monitoring feedback. BMPs will be continuously improved to meet Weyerhaeuser’s sustainable site productivity strategy. ‘(’ 1998 Published by Elsevier Science Ltd.

Keywords-Best management practices; compaction; guidelines; organic matter; productivity; reliable process; risk rating: soil disturbance; soil nutrition; sustainability.

The objective of this paper is to describe the steps and processes the Weyerhaeuser Company is using to develop operational guidelines to maintain and enhance the productive capacity of the soil in order to achieve sustainable production of forest products through successive crop rotations.

1. BACKGROUND

The Weyerhaeuser Company is an international forest products company. The prin- ciple business segments of the corporation are: Timberlands, Wood Products, Pulp, Paper and Packaging Products, Real Estate and

*Author to whom correspondence should be addressed: Ron Heninger, P.O. Box 275, Springfield, OR 97477, U.S.A., Tel.: 541-741-5368, FAX: 541-741-5589.

Financial Services. This discussion will concen- trate on the Timberlands Business (the growing and harvesting of trees).

Weyerhaeuser ownership of private commercial forestland in the United States totals 2.1 million ha, split almost equally between the Southeast and the Pacific Northwest. In addition, 7.2 million ha of forest land is under long-term lease from the provincial govern- ments in Canada. This combined timberland asset is managed following the principles embodied in the Weyerhaeuser Forestry Resource Strategies and Stewardship Statement. The practice of sustainable forestry to meet the increasing worldwide demand for wood and wood products is a primary goal of the Timberlands Business.

Weyerhaeuser has been in the timberland management business since our first purchase

255

256 R. L. HENINGER et al.

of land in 1900. We established the first certi- fied Tree Farm in 1941. In the late 1960s our Research and Forest Operations developed the concept of High Yield Forestry. High Yield Forestry is an approach to forest management based on growth and yield studies and computer simulations, with estimates of gain due to tree improvement, state-of-the-art tree propa- gation methods, forest regeneration and state- of-the-art silvicultural methods. Forestry practices included: site preparation and vegetation control, hand planting, applying fertilizers to maintain soil nutrients, stand density regulation (pre-commercial or commercial thinning) and harvest scheduling on a sustained yield basis.

In the early 1990s we developed and adapted our current forest land management philosophy-Weyerhaeuser Forestry-to emphasize sustained productivity and stewardship. Forest Councils were established to develop strategies on current issues, to define Weyerhaeuser Forestry and to establish adaptive research trials. Environmental Forestry Research was expanded and now includes Watershed Analysis Teams in all U.S. geogra- phies. Through the Forest Councils, Resource Goals were establish for: forest products, water quality and fish habitat, wildlife habitat, soil productivity and aesthetics.

We will accomplish this by: practising sustainable forestry to meet increasing worldwide demand for wood and wood products; performing to standards set for all forest operations; basing our management processes and practices on scientific research and technology; leading cooperative efforts with public agencies and other groups interested in forest resources to develop balanced, cost-effective forest practices and regulations based on sound scientific standards; and meeting specific resource strategies and goals set by our Forest Councils.

Each resource strategy listed above can be more specifically stated. Our soil productivity strategy is: “We protect soil stability and ensure long-term soil productivity by: (1) using equipment and practices appropriate to the soil, topography and weather to minimize erosion and harmful soil disturbance, and (2) using forestry practices and technology to retain organic matter and soil nutrients.” This two-part resource management strategy will be discussed separately.

2. FACTORS OF SOIL PRODUCTIVITY

Within climatic and biological constraints, site productivity depends on the productive capacity of the soil. The productive capacity of the forestland site is determined by factors that are extrinsic and intrinsic. Extrinsic factors provide the framework that ecosystems are developed on and are most influential in determining long-term regional productivity potentials, i.e. geology, topography and climate.

Intrinsic factors are affected by ecosystem processes and are subject to modification by forest management activities. Examples include certain soil physical, chemical and biological properties and microclimate. Intrinsic factors generally do not affect long-term productivity potentials when viewed in terms of geologic time, but within the time frame of forest management, they may raise or lower productivity significantly.‘,2 Because of the in- herent complexity of natural systems, some site factors-for instance some soil characteristics-cannot be called either entirely extrinsic or entirely intrinsic. But these two categories do provide a reasonable framework for dis- cussing how forest management affects the factors controlling potential productivity.

Where forest productivity potential has declined, evidence shows that the common de- nominators are soil displacement,‘73-9 losses in soil macroporosity due to soil. compaction and puddling2.‘0-16 and losses of organic matter,“- 22 thus the emphasis on both physical soil disturbance and organic matter management. Lands taken out of production due to roading and landings also contribute to decline in forest productivity potential and should be mini- mized.

This paper describes the strategies and processes undertaken by Weyerhaeuser to achieve sustainable site productivity within the Douglas-fir Region of the Pacific Northwest (850 000 ha in the states of Washington and Oregon), where 35% of the ownership lends itself to ground-based logging.

3. GEOLOGY AND CLIMATE OF THE PACIFIC NORTHWEST

3.1. Geology

The Pacific Northwest is among the more diverse regions of North America with respect to environment and vegetation. Oregon and

Managing for sustainable site productivity 257

Washington, the heart of this region, encom- pass wet coastal and dry interior mountain ranges, miles of coastline, interior valleys and basins and high desert plateaus. Moisture, temperature and geologic substrate vary greatly. Landforms vary from level river valleys and lava plains to precipitous mountain slopes. We have land within five of the physio- graphic provinces described by Franklin and Dyrness.” The Olympic Peninsula, Puget Trough, Northern and Southern Washington Cascades and the Coast Range are dominated by temperate conifer forest with Douglas-fir [PseuAorsugn mensiesii (Mirb.) France], western hemlock [ Tsuga heterophyllu (Raf.) Sarg.], western redcedar (Thuja plicata Donn), and true firs [Abies procera Rehd. and Abies umabilis (Dougl.) Forbes] at higher elevations.

There is a tremendous amount of variability in the soils of the region. Volcanism has dominated the shaping of much of the landscape in the Cascade Ranges, the most recent being the eruption of Mt. Saint Helens in 1980. The Northern Cascades and the Puget Trough were also glaciated. The Coast Range consists predominantly of uplifted sedimentary material, which is dominated by tephra.

3.2. Climute

The varied climates of Oregon and Washington result from complex interplay between maritime and continental airmasses and the mountain ranges, particularly the Cascades which run north and south and divide the States into eastern and western portions. The western portions have a maritime climate characterized by (1) mild temperatures with prolonged cloudy periods, muted extremes and narrow diurnal fluctuations (6- 10°C); (2) wet, mild winters, cool relatively dry summers and a long frost-free season; and (3) abundant precipitation of low intensity (typically 1700-3000 mm or more on the coast). 7585% of which occurs between October and March, mostly as rain. Most precipitation is cyclonic, the result of low-pressure systems that approach from the Pacific Ocean on the prevailing westerlies. During summer, storm tracks are shifted to the north and high- pressure systems bring fair, dry weather for extended periods. There are some important variations in the climate of the western low- lands as a result of the coastal mountains and of latitude. Coastal mountains are responsible for the drier and muted climate of the valleys,

Puget Trough and interior valleys of the southwestern Oregon. The maritime airmasses are blocked from these areas to varying degrees and precipitation declines markedly in resultant rainshadows. At the same time there is a general latitudinal increase in precipitation from south to north. Within the Cascade Range, elevation has a primary effect on local climate.

The varied soil and climatic environment within which our forest land exists has resulted in a range of forest species types within the landscape and various site productivity classes.

4. BIOLOGICAL TENETS AND DEFINITIONS FOR SOIL DISTURBANCE

Soil productivity potential, as we define it, is the capacity of the soil system to support plant growth, particularly crop tree growth. The base productivity level is the natural capacity of unaltered soil to support plant growth as measured by the production of the crop species for a given regime over a specified period and measured in tonnes/hectare/year.

4.1. General premises

Soil productivity potential can be enhanced above ‘base’ levels in some situations by altering factors that are limiting growth such as: chronic nutrient deficiencies by adding nutrient amendments; excessive water by water management systems; compacted soil layers by soil cultivation; and poor soil aeration by soil mounding. Conversely, soil productivity potential can be decreased below ‘base’ levels by altering soil properties to the extent that growth limiting conditions occur, such as: nutrient depletion or topsoil displacement which limits nutrient availability; compacted or puddled soils which restrict root growth and can disrupt subsurface water flow; saturated soils which reduce aeration and limit root growth; and reduced organic matter which results in less nutrient capital and less desirable soil structure which reduces moisture holding capacity/infiltra- tion and limits root growth.

4.2. Soil physical properties

Loss of topsoil and associated litter layers can reduce soil productivity potentia1.3,4,8,9.24

258 R. L. HENINGER et al

Practices that displace topsoil, result in erosion or cause mass wasting are detrimental to the soil productivity potential of the area from which the soil was removed or displaced. Soil aeration and macro-pore space are critical determinants of soil productivity.2~10*1i”3.‘5 Soil compaction can be detrimental or ben- eficial depending on the level of pore space in the undisturbed soil and the amount of macro-pore space.2 Disruption of pore space continuity can also impact water movement.

4.3. Strategy

The objective is to control physical disturbance and mitigate detrimental physical disturbance to forest soils. The approach is to develop a set of integrated decision-making guidelines to assist forest planners, engineers, harvest managers and foresters to understand how their activities impact the physical properties of soils. To begin with, we needed to understand how each group made decisions about harvest and silvicultural activities and how these decisions affected the next group. Interviews were held to understand these decision processes. It was then determined where synthesis of information would make decision- making more effective, i.e. develop guides or processes to improve consistency in decision- making. This strategy and teamwork lead to our tactics.

5. PROCESS COMPONENTS REQUIRED TO ACHIEVE SUSTAINABLE SITE PRODUCTIVITY-

SOIL DISTURBANCE

Generalized elements of the process are out- lined in Fig. 1. The process used to ensure that sustainable site productivity is attained consists of the following components:

Research and strategic databases leading to soil management guidelines, including common goals and standards Education and training to communicate state-of-the-art knowledge, rationale and expectations Implementation of ‘Best Management Practices’ (BMPs) to consistently achieve goals and standards Ongoing monitoring of performance Adaptive management experimentation Results from monitoring and experimentation applied to achieve continuous improvement.

5.1. Soil disturbance management process

In order to develop and implement a process for integrated decision-making, specific pieces of information or data were needed. The list of required information, ‘tools’ and reliable process that were desired included:

Strategic database pertaining to disturbance impacts on tree and stand growth Soil survey of ownership* Soil disturbance classification system Soil operability ratings* Growth and yield strategic database derived from a matrix of studies located across appropriate soil/climatic zones and a reliable growth and yield forecasting model Monitoring and tracking system* Training and education program

(*Integrated with Geographic Information System.)

5.2. Strategic database

The key elements of a strategic database include the following: desired outcome (goal) specified; desired silvicultural prescription specified; inference space defined (local/ region); defined database matrix that covers the critical variables affecting productivity over time; and treatments that extend beyond the ‘normal’ range of activities. A strategic database is designed to: (a) provide an understanding of the biological processes; (b) provide data to develop and validate growth and yield models; and (c) evolve as new knowledge is gained.

Weyerhaeuser growth and yield research included several studies on the impacts of skid trails on the growth of planted conifers. The first series of test plots were only in one geo- climatic zone along the Washington coast and it was felt that we could not extrapolate the

STRATEGIC DATABASE

RESEARCH / GUIDELINES

IMPLEMENTATION OF BEST 0 MANAGEMENT PRACWZES

(BMPs)

Fig. 1. Process components required to achieve sustainable site productivity.


results to other geo-climatic zones in Oregon and Washington. Thus, another series of disturbance class impact trials were installed in two other major geo-climatic zones. These trials evaluated the impacts of non-cultivated disturbed’skid trails, cultivated skid trails and non-disturbed soils (controls) on tree survival and growth. These data helped provide an understanding of the amelioration potential of various soil disturbance classes in various geo- climatic zones. The results of these trials showed that there were no significant differ- ences between treatments in the coastal environment. However, there were reductions in height growth on the drier interior sites of Oregon where the soils have a higher clay content, a lower organic matter content and less summer precipitation (Fig. 2). Cultivation restored the growth potential to that of the non-disturbed soil.

Eventually our plan is to have the soil disturbance growth data sets linked with our growth and yield forecasting model. This will provide better estimates of growth impacts and help foresters make decisions on site preparation cultivation opportunities.

Over the past several years harvest equipment mix began to change from hand-felling to machine-felling, and from traditional ground-skidding to shovel-yarding where logs are lifted and swung toward the landing. This machine configuration resulted in about twice as much ground being covered by machine tracks as compared to traditional hand-felling and ground-skidding; however, there are fewer trips on any given track. These machines are tracked and have less ground pressure than rubber-tired machines. The severity of the soil disturbance is usually less. A new series of stu-

7

iii 6

pc6 F Y4

04 I

0 12 3 4 5 6 7 6 9

YEARS SINCE PLANTING

-c LOGGED ONLY -m- NONRIPPED --c RIPPED

Fig. 2. Height growth of Douglas-fir growing on logged- only non-disturbed soil, compacted non-ripped and ripped skid trails in two geo-climatic zones in Washington and

Oregon.

dies was established to evaluate this type of logging system.

5.3. Soil surve?

Soil survey data were available from both the Weyerhaeuser survey done in the early 1970s and the Soil Conservation Service (now the Natural Resource Conservation Service). These sources provided the various soil series descriptions and some soil physical and chemical data. Soil operability ratings (described below) were developed from this information. Soil survey maps can subsequently be integrated with Geographical Information Systems (GIS).

5.4. Soil disturbance class@ation system

In 1977 a soil disturbance classification system was developed (see Fig. 3). The classification system describes a continuum of traffic disturbance types across the soil surface. Undisturbed soil is classed as ‘0’. As machine traffic moves across the soil, the topsoil is compacted, class ‘1’. As traffic continues it starts to churn and mix the organic material into the topsoil and becomes puddled, class ‘2’. The subsoil may or may not be compacted depending on the depth of the topsoil. As traffic continues the topsoil is partly removed and the subsoil is compacted or puddled, class ‘3’. In class ‘4’ the topsoil is removed and the subsoil compacted or puddled. A modifier to the above occurs when the soil disturbance causes disruption to the subsurface water flow, caus- ing the soil to become and stay saturated for 10 days or more, modifier class ‘S’. Our current recommendations are: class ‘1’ is acceptable, minimize class ‘2’ disturbance and eliminate classes ‘3 and 4’. Our research shows that cultivation can restore the soil’s growth potential for classes ‘1, 2 and 3’, therefore we recommend cultivation of these classes. To properly cultivate class ‘4’, the displaced soil, usually located in berms to either side of the skid trail, must be pushed back onto the exposed subsoil and then cultivated. Class ‘S’ disturbance cannot be readily restored without mitigating the factors contributing to the soil drainage problem.

5.5. Soil operability rating

Guidelines were needed to help forest planners, engineers and harvest managers understand which soils were more susceptible to detrimental soil disturbance, including soil dis-


Topsoil _---------

Subsoil

Soil Condition:

Topsoil Undisturbed Compacted Puddled Partly Removed Removed

Subsoil Slightly Compacted Mixed Puddled or Not with Compacted Topsoil

Classification: 0 1 2 3 4 Disturbance Undistu&d Light Moderate Moderate- Severe

Severe

Recommendation: Acceptable Minimize Eliminate

Cultivate as Needed W

Fig. 3. Weyerhaeuser’s soil disturbance classification system.

placement, compaction and puddling during ground-based logging operations. Based on extensive research on soil-site factors” and research/operational experience, our view was that the key soil attributes to be considered were: thickness of the A horizon; soil texture; drainage and permeability; and depth to water table. The data from the soil survey and the profile descriptions were used to develop a spreadsheet listing all of these variables. A set of criteria for each soil attribute was developed and applied to the spreadsheet data to group the soils into four categories of risk or operability: low, moderate, high and very high (Table 1). Recommended ground-based logging guidelines were formulated for each operability group.

?? Low-risk soils operable 12 h after heavy rain (year-round operations).

?? Moderate-risk soils operable 72 h after heavy rain during spring-summer-fall operations only.

High-risk soils, no ground-logging during wet weather; summer and early fall operations only. Very high-risk soils, sensitive all year; recommend cable logging.

These ‘best’ operating windows do not mean that the indicated season is the only period that a particular class soil can be oper- ated on with ground-based equipment. It does indicate that there is a greater risk of unaccep- table soil disturbance when operating occurs outside of the recommendations. The operability risk ratings for each soil were transferred to planning maps as an overlay attached with each soil series name using GIS technology. To date, this has been accomplished in one region; the goal is to eventually have this capability in all regions.

Harvest units are pre-scheduled 3 years in advance of logging. The forest engineers field review each unit to verify the soils and assigned risk rating. In addition, they gather

Soil property

Table 1. Soil operability risk rating properties and classification

Soil operability risk class

Low Moderate High Very high

A-horizon thickness Moisture and permeability Texture Depth to water table

Very deep

Rapid Sandy

Very deep

Deep

Moderate Loamy Deep

Moderate

Slow Clayey

Moderate

Shallow

Very slow Clayey Shallow


information needed for road construction, wetland and riparian zone protection considerations, management of wildlife and other sensitive issues. Based on all this information the harvest unit is assigned the season of year for logging and the preferred logging equipment configuration. The engineers select equipment to match the soil and terrain, based on their past experience. Harvest managers re-confirm the equipment selection and make adjustments based on current weather patterns at the time of harvest. Season of year and equipment are, therefore, matched to minimize soil disturbance.

5.6. Soil management teams

The Soils Management Team was sponsored by the Weyerhaeuser Forest Council in 1994 to recommend a process to manage soil disturbance. The team consisted of personnel from harvest and forestry operations and Forestry Research. Their charge was to develop soil management goals, performance standards and BMPs based on biological requirements and principles, science, econ- omics, aesthetics, public expectations and regulations. The desired outcome of the team’s efforts was the implementation of reliable processes to consistently meet or exceed measurable soil management standards for harvesting and forestry operations. They were also to develop and maintain a focus on forest soils management throughout Weyerhaeuser Timberlands operations.

A reliable process is defined as a process that can be communicated to an individual or team, which produces a desired outcome in a safe, repeatable, efficient and measurable man- ner.

Best management practices are those practices that are cost effective, achieve soils management objectives and standards given ‘state- of-the-art’ knowledge and represents a prudent approach to resource management. BMPs evolve as more scientific and operational experience is gained.

5.1. Assessment criteria

The focus of the soil management standards is to minimize or eliminate, if possible, soil disturbance that has a significant negative impact on either site productivity, the potential for subsequent soil erosion or forest aesthetics. The team developed assessment criteria to include:

1. the percentage of the ground logged area in a setting with soil disturbance using the classification system described above,

2. the depth of the soil disturbance, 3. the distribution of soil disturbance across

the setting, and 4. visual impacts.

5.8. Monitoring

Research members developed the monitoring methods. The Forest Council determined that all ground-based logged units should be audited for amount and kind of soil disturbance. The audit is conducted by a trained independent outside contractor, who records the information on an electronic hand-held data recorder. Immediately following the audit the files are downloaded to a PC and sum- maries developed and printed. Results are for- warded to harvest managers and district foresters as soon as possible. This provides a feedback loop to operators on how they are doing and provides foresters information for site preparation.

5.9. Operating standards

The audit data were instrumental in developing operating standards. The current standards for per cent of soil disturbance are:

?? Class ‘2’ soil disturbance: target range lo- 25% or less of the area, depending on number of machine entries.

?? Class ‘3 and 4’: target is O&2% of area. ?? Class ‘S’ (saturated): target is 0% of area.

Results to date are encouraging, as shown in Fig. 4. The survey results from data col- lected in the 198991990 winter logging season, before effective implementation of a soil management process and training, showed that dis-

Fig. 4. Results of implementation of soil management guides on ground-based logging soil disturbance, cornpar-

ing 1989-1990 to 1994-1995 winter logging.

262 R. L. HENINGER ct al.

turbance class ‘3 and 4’ was approximately 7%, class ‘2’ at 12% and class 1 at 10% of the area. The results of the 1994-1995 winter logging season, after several years of operating with soils management process, showed that disturbance class ‘3 and 4’ was at 1% and class ‘2’ was reduced to 8% of the area. This was achieved by having the aforementioned process as described in place. All employees who have the potential to impact the soil have common goals and standards, which they apply in their own work situation.

5.10. Education and training

The other key step in the process is education and training of staff. A training program was developed by the Soils Management Team. The program includes a handbook of pertinent information for easy reference, a slide presentation and a video to help illustrate the importance of the soil as resource. The program includes five sections: (1) soil func- tion and properties; (2) harvesting and site preparation impacts on tree growth; (3) soil protection techniques; (4) stewardship policy and regulation; and (5) soil classification and disturbance evaluation. The training program covers the concepts of forest soils management and BMPs for ground-based harvesting. The modules are used with all personnel that have decisions related to, or responsibility for, activities that could impact the soil. The training has taken place in the office as well as in the field, especially with equipment operators. Soils management is the responsibility of each employee.

5.11. Example of BMP

Weyerhaeuser’s BMPs for skid trail amelioration starts with the Forester and Harvest manager deciding in the field on the need for soil rehabilitation. These conditions meet the requirement for cultivation: all ‘dirt’ logging roads; severely compacted class 2, 3 and 4 logging trails; severely compacted class 1 and 2 unit area soil disturbance (continuous soil compaction); intersection of logging trails with roadsides; and dirt landings. Effective cultivation can be achieved with: (1) spading with a brush-rake mounted on a tractor; (2) rock-rip- pers or winged subsoiler pulled by a tractor; or (3) a scarification-rake grapple mounted on an excavator shovel. The soils need to be below field capacity or dry for cultivation to shatter compacted soil effectively. Currently

an excavator shovel with a scarification-rake is the preferred equipment for soil cultivation. This combination is very effective at shattering compacted soil under a wide range of soil moisture conditions, and at bringing displaced topsoil and woody debris back onto the skid trail. Treatment steps include: (1) excavator backs out the trail cultivating the soil by push- ing and pulling the scarification rake through the soil to a depth of 60-75 cm; (2) displaced topsoil is pulled from the berm of the logging trail back onto the trail (bringing decomposed organic matter and nutrients back to the soil surface); and (3) woody debris (tops and limbs) topsoil are taken from alongside the trail and scattered across the trail (restoring a longer-term source of organic matter). This also helps reduce the risk of erosion.

5.12. Adaptive experimentation and research

Throughout this sequence of activities gaps in our knowledge base are reviewed and separ- ated into two basic groups: (a) information needs that can be addressed effectively through adaptive management experimentation, and (b) more basic problems which need to be addressed by the Forestry R and D Forest Productivity Team.

A strategic database will be developed, as a part of on-going operations, to address the information needs of the Soils Management Team. The cooperative research between operations and R and D provides information needed to continuously improve practices related to meeting the Weyerhaeuser Forestry Resource Goal on Soil Productivity.

5.13. Continuous improvement

Knowledge from operational experience and the data that have been gathered are docu- mented, communicated and applied to improve the overall process. The process continues as we learn more about the impacts of our activities on the soil and how these affect timber growth.

6. PROCESS COMPONENTS REQUIRED TO ACHIEVE SUSTAINABLE SITE PRODUCTIVITY-

SOIL ORGANIC MATTER, NUTRITION AND BIOTA MANAGEMENT

6.1. Organic matter/nutrients key tenets

Our goals are to: (1) conserve organic matter/nutrients throughout the managed forest cycle; (2) balance nutrient outputs/inputs


through successive rotations; and (3) replace nutrients through fertilization and management of vegetation. Organic matter significantly impacts soil nutrients, soil structure, organism diversity and ecosystem health.‘7-2’ Nutrients are removed from harvested sites in increasing amounts as biomass removals increase and rotation lengths shortened: total- tree utilization plus litter removal > total-tree utilization > bole-only utilization > partial-bole utilization.‘6.27 Harvest removes nutrient capital in excess of ambient inputs under short rotation cycles (40-50 years) where a high proportion of the standing biomass is removed, particularly since many nitrogen-fix- ing species like red alder (Alnw rubra Bong.) are controlled to minimize competition with the conifer crop.2”,29 Soil organic matter levels affect productivity potential and vary naturally based on geologic/soil/climate/biological factors and man-made disturbances. Organic matter management needs to be a critical com- ponent of any process aimed at managing nutrient ‘outputs and inputs’, and sustainable productivity.

6.2. Generul premises

(1) Organic matter can be reduced in some soils and the productivity potential of the soil can still be maintained or enhanced above ‘base’ levels.30.3’ (2) Conversely, organic matter can be increased in some soils without a corresponding increase in soil productivity potential.“.3’ (3) Conservation of soil organic matter is important on most sites as the demand for soils nutrients resource increases with increasing management intensity.29

6.3. Soil organic matter management process

There is a significant data gap concerning the role that organic matter conservation and nutrient amendments play in sustaining long- term site productivity. The following data sets are needed to understand how organic matter and nutrient amendments need to be managed so that appropriate guidelines for best management practices can be developed.

?? Determine the soil’s natural capacity to support stand growth as measured by crop tree species production in tonnes per hectare per year for a given regime over a specified time period. These data will be forthcoming from a comprehensive growth and yield database

matrix, which is designed for the develop- ment of growth and yield forecast models. Understand the capacity of a soil to supply the nutrient demands of the crop. Sites that have a high proportion of their nutrients in standing biomass as opposed to the soil reserve may be more susceptible to nutrient deficiencies under high biomass removal and short rotation management regimes than sites with a high proportion of their nutrients in the soil rather than in the standing crop. Understand the impacts that various nutrient amendment regimes will have on crop tree nutrient status and tree growth under different biomass (organic matter) removal regimes. These data will be used to develop appropriate organic matter management strategies and nutrient amendment guidelines. Track crop management histories and monitor crop and associated vegetation production, so that long-term trends in crop productivity can be assessed. This is the validation step to ensure that our soil management strategies are being attained. The database will also provide insights into management regimes or sites that are most efficient to manage and those which require extraordinary measures to ensure that productivity is maintained.

6.4. Strategic database

Currently we have a comprehensive growth and yield database. The database covers a range of silvicultural regime options located across various geo-climatic zones and a range of site index classes within those zones. The primary variable of productivity is site index (height at 50-years breast height age) determined from natural stands as part of the soil survey process. This variable is currently ser- ving as a surrogate for productivity until managed stands in the growth and yield database reach harvest age. At that time a more direct parameter of productivity, i.e. t/ha/year, can be ascertained.

Fertilizer response to nitrogen applications is well understood for natural Douglas-fir stands in the Pacific Northwest.‘4 However, there are very few data from managed planted stands. It is important that we understand if repeated nitrogen applications result in other


nutrients being in inadequate supply for opti- mal growth, and if fast growing genotypes will be more nutrient demanding than slower growing genotypes.

We are developing research proposals that are designed to assess organic matter management and nutrient amendment strategies and tactics that relate to logging and site preparation practices. Like several study designs presented in papers at this workshop, our plan will evaluate the long-term site productivity impacts of bole-only harvest versus total-tree harvest and total-tree plus all woody vegetation removal. The benefits that can be attained from cultivation and nutrient amendment treatments will also be assessed. These are expensive research projects and require long measurement periods over multiple rotations. The plan is being considered for a cooperative research venture among interested parties.

6.5. Soil nutrient capital reserves

Soil nutrient data are available from our soil survey database and from the Natural Resource Conservation Service (formerly the Soil Conservation Service). The intent is to understand nutrient removal and input processes so that nutrient demand requirements can be met, and to risk-rate soils as to their potential for developing nutrient deficiencies. Additional information from foliar analysis in yield forecasting plots, fertilizer studies and crop monitoring will help us diagnose nutrient problems. A nutrient risk-rating system for soil groupings corresponding to ‘low,’ ‘moderate,’ ‘high’ and ‘very high’ nutrient deficiency risk can then be developed, similar to the soil operability risk rating previously described. Appropriate soil management and nutrient amendment regimes would be developed for each soil grouping. A draft prototype is com- pleted and in review.

6.6. Fertilization

Currently, periodic nitrogen fertilizations are an integral part of our forest management strategy. In the future, fertilization guides will be developed based on our soil nutrient risk ratings, foliar nutrient analysis data and results from empirical fertilization trials. At present we do not have any studies to evaluate elements other than nitrogen. However, in the past there were several studies to evaluate growth response to nitrogen plus other el-

ements.35 The data matrix covered limited soil groups. Results from these studies indicated that there were no significant increases in growth over the nitrogen-only treatment. We expect to find some soil groups where other elements in combination with nitrogen will result in increased growth.

6.7. Organic matter guides

A common question is, “How much organic matter should be left after logging and site preparation?” At the present there is not an adequate answer for this question. The answer depends on many interacting variables described above.

Until more information is at hand, we are modifying our site preparation methods to follow this prudent Best Management Practice:

Plant after logging with no site preparation, except where adequate planting spots are not available or competition is above specified threshold levels. When possible, conduct site preparation during harvest operations including: thorough utilization of all merchantable logs (grade and fibre); avoid practices that result in continuous, deep concentrations of slash; scatter concentrations of slash when- ever possible so that slash is uniformly dis- tributed and the desired number of quality planting spots are available. Follow the assessment process for determining the need for site preparation based on unit specific data (see BMP example for skid trail amelioration above). The following steps should be evaluated: (a) determine fire hazard risk and abate if necessary; (b) evaluate the number of suitable planting spots-site prepare to increase number to target level based on cost/benefit analysis; (c)determine level of competing vegetation -site prepare if current or expected levels exceed specified thresholds which significantly impact seedling survival and/or growth. The preferred treatment for mechanical scarification is to use an excavator with specially designed brush/root-rake tines on a modified-bucket attachment. A tractor with root rake is not recommended. Treatment specifications are as follows: minimal displacement of the forest floor; scatter concentrations of slash and woody vegetation to achieve the target distribution


5.

of suitable planting spots; and when piling is unavoidable use narrow/discontinuous rows approximately 2 m wide and less than 6 m long, or use small piles less than 3 m in diameter and less than 2 m high. Minimize broadcast burning, except in the cases where risk from wildfires is high. Burning of piles may be needed along landing areas where the concentration of logging debris can be very high and quality planting spots are limited. Broadcast burning is sometimes necessary to reduce the fire hazard from contiguous areas of logging slash and to meet planting requirements on steeper ground where safety considerations limit equipment and planter access.

6.8. Crop history trucking

Crop history refers to the record of silvicultural treatments and harvest removals for individual management units. This information will be required to validate management strategies and tactics pertaining to meeting sustainable site productivity goals. These data can be used to gain insights into developing productivity issues or opportunities, i.e. sites where productivity may be showing a declin- ing or increasing productivity trend over one or more rotations

Currently, detailed crop history records are tracked for all studies within the extensive sil- viculture growth and yield database. The plan is to eventually maintain detailed crop history records for at least a subset of operationally managed stands across a range of soils/climate zones, as well as the adaptive trials proposed to test organic matter and nutrient amendment strategies. These crop history records will be kept on our computer database, linked with our GIS.

7. SUMMARY

Weyerhaeuser has made a public commit- ment to meeting its forest resource strategies including one pertaining to maintaining soil productivity. The soil productivity strategy is as follows. “We protect soil stability and ensure long-term soil productivity by: (1) using equipment and practices appropriate to the soil, topography and weather to minimize erosion and harmful soil disturb-

ance, and (2) using forestry practices and technology to retain organic matter and soil nutrients”.

The processes developed to minimize erosion and soil disturbance should help meet the first goal. Through understanding the soils’ potential for compaction, having descriptive soil disturbance classes and a research database on growth impacts, has enabled the Weyerhaeuser Company to develop guidelines and best management practices. Education and training of employees is an important step in implementing the guides and BMPs. Through the monitoring and audit process information is gained to assess performance against those standards. Implementation of processes always raises questions, which lead to additional research and operational adaptive trials. Based on new information, operations, standards and processes will be improved, and BMPs modified or adjusted to meet Weyerhaeuser’s sustainable site productivity goal.

The processes planned to retain organic matter and soil nutrients will lead to improved management practices. Organic matter management guides and soil nutrient-risk ratings in combination with nutrient amendment pre- scriptions will lead to the implementation of BMPs required to meet this goal.

The elements of the Weyerhaeuser process include having a research strategic database; common goals and standards leading to guidelines: education, training and teaming across the organization; implementation of BMPs; monitoring of performance and adaptive experimentation, which leads to continuous improvement.

Sustainable site productivity should be attained when the above soil management processes are combined with the following silvi- culture strategies of (1) planting the appropriate tree species matched to site requirements, (2) using adapted genetic material with field-tested proven performance, (3) applying the appropriate silvicultural regime that produces the desired forest products and (4) using integrated pest management principles to reduce risk from disease/insects and environmental stress.

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managing for sustainable site productivity: weyerhaeuser's forestry perspective

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