Stand Establishment and Culture of Hybrid Poplar

Charles E. Kaiser, Donald E. Rice, Kirk R. Wallace
James River Corporation, 79114 Collins Road, Clatskanie, OR 97016

Abstract

Fueled by the energy crisis of the mid 1970's and a simultaneous increase in domestic demand for communication grade paper products for the computer age and world demand for tissue and towel grades, technicians turned to short rotation intensive culture research for biomass and pulp fiber supplies. In the United States pulp and paper industry, the increase in computer driven demand and the insistence of papermakers for higher percentages of hardwood fiber in the "furnish" to improve paper quality far outstripped the ability to supply hardwood fiber in the Pacific Northwest through traditional managed forest growth practices. By crossing native Black cottonwood of the Northwest and Eastern cottonwood, a short rotation hybrid with superior growth characteristics was developed. To achieve maximum growth, best management agricultural practices have been developed for site preparation and cultivation. Harvesting machinery properly selected and utilized proves to be an effective means to maximize yields from individual stands throughout scheduled harvested acres. An overview of all management practices developed to successfully establish, maintain and harvest short rotation hybrid cottonwood in the Pacific Northwest by James River Corporation is presented.

INTRODUCTION

The forest industry in the Pacific Northwest has gone through a series of significant changes over the past four decades. Forestry has progressed from the early management attempts of the 1950's to forest land and timber investment optimism in the 1960's. The economic boom of the 1970's gave way to an economic tightening in the 1980's. These changes in the Pacific Northwest run hand in hand with a continuing race for low-cost wood. Pulp fiber, traditionally a by product of the timber and wood products industries, historically has become expensive. In the 1990's, wood supplies in the Pacific Northwest have become difficult to obtain due to environmental pressures placed on traditional sources (ie. state and federal timber lands).

FACTORS LEADING TO FIBER FARM CONCEPT

James River Corporation operates two pulp mills along the lower Columbia River, at Camas, Washington and Wauna, Oregon. The wood supply for these mills comes from southwest Washington, northwest Oregon and areas along the Columbia River in eastern Washington and Idaho. The relatively high cost of wood fiber in the area has significantly affected the relative competitive position of these mills. Wood supply costs have risen due to the reduced availability of sawmill and plywood residuals, a direct result of the Pacific Northwest's loss of market share to Canada and Southern States. Traditionally, native red alder and hemlock have provided additional sources of both short and long-fiber, respectively, but both species supplies are diminishing due to the successful efforts of forest managers to replace them with high valued Douglas fir. Greater fiber recovery from the limited sawmilling and planing operations add to the dismal fiber picture. James River's needs for alternative sources of both alder and hemlock is the driving force behind short-rotation intensive culture of hybrid poplar.

HISTORICAL BACKGROUND

In 1981, Crown Zellerbach's Forestry Research Division established a research station in the Lower Columbia River Floodplain near the town of Westport, Oregon. The focus of the research projects established were primarily on selection of plant materials and genetics, planting stock quality and propagation, and plantation culture. Specifically, projects addressed plantation spacing, poplar clonal testing, species/site comparison studies, European alder provenance tests, herbicide screening tests and competition effects studies. From the information gained in these study projects, an operational farm was established in 1982. This first attempt to establish cottonwood operationally was a dismal failure. Success was first achieved in 1983 and has flourished since that time. In 1986, James River Corporation purchased the pulp and paper division of Crown Zellerbach including the established cottonwood plantations.

SITE LOCATION

James River currently has 4,450 ha (3,560 ha are in actual production) located in diked, drained land along the lower Columbia River. The Fiber Farm currently lies in both the states of Oregon and Washington and stretches from the Pacific Coast on the northwest 160 km south and east towards Portland, Oregon.

The lands consist of cultivated fields and unimproved pasture lying within levees. These areas have alluvially deposited silt loam, peaty clay loam, or sandy loam soils which are at or below river level. Because these soils are moderately to poorly drained, drainage systems with pumps or tide gates are required. It is not uncommon to have standing water in portions of the fields throughout the winter and late spring. Permeability is moderate to moderately slow. Percent of organic matter ranges from 1 percent to 35 percent. Fertility of the sites varies, but generally they are plentiful in both macro- and micro-nutrients.

The area has a maritime climate with mild, wet winters, cool, dry summers and a long growing season. Precipitation that normally occurs in western Oregon and Washington (up to 1,520 mm annually) occurs mainly in winter, largely from mid-October to mid-May. Prolonged cloudy periods are common as well as an occasional ice and snow storm.

SITE PREPARATION

Proper site preparation is critical for a successful plantation. Falling short of the standards stated has proved disastrous for the Lower Columbia River Fiber Farm in both survival and growth. In order to promote root development, adequate soil aeration, and allow for maximum herbicide effectiveness, we encourage proper site preparation.

In the final condition, the soil should be tilled 25 to 30 cm deep, have a maximum clod size less than 8 cm and contain a proportional range of soil particle sizes. The ground should be free of any weed vegetation after tillage. Since root development will move downward as well as laterally, any hardpan or deep heavily compacted soil should be broken. The finish disking should allow for uniform herbicide application. No clod shadows, oversized clumps or extremes in topography should exist.

Timing of site preparation should allow enough time to prepare the site before the rainy season, and yet have the last operation occur just before the rainy season, to control fall resprouting of weeds.

Spacing needed for proper tree growth and full utilization of land has not yet been fully defined. Current spacing varies between 3.0 x 1.5 m, 3.0 x 2.1 m, 2.7 x 2.7 m, depending upon clone, site and proposed cultural activities. Planting design can be square or rectangular. One must allow adequate room for potential operations in the fields after planting. Allowance for herbicide application, mechanical weed cultivation, and crop monitoring should be taken into consideration.

Marking the planting rows in the finished field can be done by equipment or manually. We have planted in 25 cm high hills in order to minimize exposure of the cutting to standing water.

Rows are marked for planting using a subsoil shank (38 to 51 cm depth) combined with a hilling implement attached to a 100 kW tractor. The implement has two hillers with hydraulically controlled 'wings' for marking the next tractor pass.

Costs for site preparation will vary depending upon type of equipment used. Standard costs published throughout the industry indicate a cost of $70 per ha.

HERBICIDE Application

Currently, our experience regarding proper timing of soil active herbicides is January to mid- March for both pre-plant and vegetation control in one year old stands. Treatment is extended to those few select stands of older trees where vegetation control is required due to poor growth for one reason or another. Typically, a mixture of glyphosate (Roundup) and pre-emergent herbicides are applied to kill existing winter annuals and to give residual control into the growing season. Current rules and regulations concerning herbicide use have greatly reduced the number and type of products available for use in hybrid cottonwood plantations. A good working relationship with chemical suppliers is a must in order to stay ahead of fast-changing and often confusing rules and regulations.

PLANTING

Genetic Consideration - Cottonwood plantations are established with unrooted, dormant cuttings collected from either one-year-old whips grown in a stoolbed or a one-year-old whips grown in a stoolbed or one-year-old side branches from two-year-old trees. This is an example of vegetative reproduction; every tree grown from cuttings produced by the same stoolbed is genetically identical. A clone is a group of trees, not necessarily of the same age, which share the same genetic makeup.

Different clones frequently exhibit large differences in growth rate, form, survival, disease resistance, and adaptability to varying site conditions. Use of the proper clone can be the determining factor in the success of a planting program.

Based on the results of extensive field tests conducted first by Crown Zellerbach and then James River, the best clones for the lower Columbia River region are those which have been developed by hybridizing native black cottonwood with eastern cottonwood. Recent developments using material from Japan is providing additional diversity of traits suitable for this region. To date, our best hybrid clones have exhibited good adaptability to a limited range of site conditions.

Stock Quality - Considering economic and operational feasibility, use of unrooted cuttings approximately 25 to 30 cm long has provided adequate survival and growth. The cuttings should be of one-year old material, dormant, have a minimum and maximum diameter of 1.0 cm and 1.9 cm respectively and contain at least one prominent bud located on the upper ¼ of the cutting.

Stock Storage - If you cannot plant cuttings shortly after they have been collected, cold storage will provide adequate protection. Protect them from drying by placing in air tight plastic bags and refrigerating them at temperatures between -3.9 to -2.2 degrees C. These temperatures limit black stem disease and permit cuttings to be safely stored for several months.

Stock Planting - Preferred planting season is mid-February through mid-April depending upon moisture received during this time frame. Manual planting provides easy access to planting sites and requires minimal equipment investment as opposed to machine planting. Field conditions found during this time frame in the lower Columbia River region are not conducive to mechanical planting. Cuttings are carried in tree planting bags and pushed into the ground by hand and are planted vertical and right side up. Place at least 25 cm of the cutting into the soil, leaving only the tip extending beyond the soil surface. Deep planting ensures deep rooting, and when most of the cutting is below ground, only one sprout is likely to emerge to form the tree. If necessary, loosen portions of the planting spot with a shovel, or use a planting bar (dibble) in hard ground or for larger cuttings.

MAINTENANCE IN PLANTATIONS

The need for minimal weed competition is critical for a successful crop in the lower Columbia River region. If weed and grass are not adequately controlled, hybrids will grow slowly and may not survive. Furthermore, unwanted vegetation provides cover to voles, which can girdle and kill trees as old as four years. Plantation weed control is usually performed by combining mechanical and manual cultivation and herbicides during the first and second growing seasons.

To minimize herbicide use, the area between tree rows are mechanically cultivated using a variety of small disks, rototillers, and dyna-drives. Down the tree row, cultivation is accomplished by adapting equipment developed for other agricultural crops. Cultivation is most effective when weeds are small. Limit cultivation to no more than 8 cm in depth to minimize damage to tree roots.

Chemical weed control during the growing reason is very limited. Products such as Poast<2>, Fusilade and Diquat will give some grass and weed control without much damage to the trees. Care must be taken when applying chemicals with backpack spray operations being the most advantageous.

Manual weed control provides excellent weed control but is extremely expensive. However, this option must be considered should conditions risking growth and survival loss prevail in a plantation.

HARVESTING

Prior to long term harvesting in 1991, many different types of equipment were tried on the Fiber Farm. Several types and sizes of feller/bunchers, skidders, delimbers, yarders, and transportation methods were tested to try and determine the most economical method in delivering a final product to the pulp mill. Various studies and cost analyses were conducted to try and improve equipment efficiencies and production rates and thus lower costs.

In May 1991, the first sustained harvest of 400 ha commenced. The most economical system found to date includes a Bell feller-buncher, both rubber-tired and track skidders, a knuckle-boom loader that feeds a modified chain flail delimber/debarker, chipper and chip vans. The mill advocates having material every day of the year which precludes seasonal harvesting. With this fact in mind, the present system includes both rubber-tired and track machines. Track machines consist of a high-track dozer and FMC skidders.

CONCLUSION

This paper presents one system for the production of short rotation intensive culture hybrid cottonwood plantations. Because the silvicultural activities of this crop resemble closely those commonly found in agriculture, both the states of Oregon and Washington have declared it so. Success in the production of trees depends upon having good soil, appropriate cultural practices, matched genetic material for location selected and, most importantly, machinery necessary to complete the required tasks, at the right time. The future of the production from cottonwood plantations will solely depend upon the advancement of technology in site preparation, cultivation, herbicide applications, and harvesting equipment.

File posted on March 5, 1996; Date Modified: February 21, 1999