Ronald S. Zalesny

Clonal variation in survival and growth of hybrid poplar and willow in an in situ trial on soils heavily contaminated with petroleum hydrocarbons.

Species and hybrids between species belonging to the genera Populus (poplar) and Salix (willow) have been used successfully for phytoremediation of contaminated soils. Our objectives were to: 1) evaluate the potential for establishing genotypes of poplar and willow on soils heavily contaminated with petroleum hydrocarbons and 2) identify promising genotypes for potential use in future systems. We evaluated height, diameter, and volume after first year budset by testing 20 poplar clones and two willow clones. Unrooted cuttings, 20 cm long, were planted in randomized complete blocks at 0.91- × 0.91-m spacing at Gary, IN, USA (41.5°N, 87.3°W). Four commercial poplar clones (NM6, DN5, DN34, and DN182) were planted as 20- and 60-cm cuttings. Sixty-cm cuttings exhibited greater height and diameter than 20-cm cuttings; however, we recommend continued use and testing of different combinations of genotype and cutting length. We identified promising genotypes for potential use in future systems and we recommend allocating the majority of resources into commercial poplar clones, given their generalist growth performance. However, further utilization and selection of experimental clones is needed. Specific clones rather than genomic groups should be selected based on the geographic location and soil conditions of the site.

Use of Belowground Growing Degree Days to Predict Rooting of Dormant Hardwood Cuttings of Populus

Abstract Planting Populus cuttings based on calendar days neglects soil temperature extremes and does not promote rooting based on specific genotypes. Our objectives were to: 1) test the biological efficacy of a thermal index based on belowground growing degree days (GDD) across the growing period, 2) test for interactions between belowground GDD and clones, and 3) identify beneficial planting windows based on combinations of genotypes and belowground GDD. We tested two clones of Populus deltoides Bartr. ex Marsh (D133, D134) and four hybrid clones of P. deltoides × P. maximowiczii A. Henry (DM101, DM105, NC14105, NC14107). Cuttings, 20 cm long, were planted in randomized complete blocks at 15- × 15-cm spacing across three planting dates during 1999 at Alexandria, Minnesota, USA (45.9°N, 95.4°W) and Fertile, Minnesota, USA (47.3°N, 96.2°W). Temperatures at 20 cm belowground were converted to GDD with a base temperature of 10°C. We measured root, top, and total dry weight, along with number of roots after 14 d of growth. Relatively warmer and cooler soil temperatures promoted rooting for the cottonwoods and hybrids, respectively. We recommend planting after reaching a threshold of 163 belowground GDD for P. deltoides clones and planting before reaching a threshold of 173 belowground GDD for P. deltoides × P. maximowiczii clones.

Opportunities for Woody Crop Production Using Treated Wastewater in Egypt. I. Afforestation Strategies

The Nile River provides nearly 97% of Egypts freshwater supply. Egypts share of Nile waters is fixed at 55.5 billion cubic meters annually. As a result, Egypt will not be able to meet increasing water demand using freshwater from the Nile and has been developing non-conventional wastewater reuse strategies to meet future demands. The USAID Mission in Cairo began promoting strategies for water reuse in 2004, and guidelines for safe and direct reuse of treated wastewater for agricultural purposes were approved in 2005 (Egyptian Code 501/2005). Twenty-four man-made forests were established that have been useful for assessing the efficacy of using treated wastewater for afforestation. At present, approximately 4,340 hectares are under irrigation with treated wastewater, utilizing a total daily volume of 467,400 cubic meters. Wastewater has been applied to trees along roads, greenbelts in cities, and woody production systems. Currently, a joint USDA Forest Service—Agricultural Research Service technical assistance team has been evaluating the feasibility of scaling up such afforestation efforts throughout Egypt. We describe information about: 1) suitable tree species that have been identified based on local soil characteristics, water quality, and quantity of water supply; 2) the benefits and consequences of using these species; 3) strategies to maximize the potential of afforestation with regard to improving water quality, maximizing resource production, increasing biodiversity, and limiting commercial inputs; and 4) potential long-term impacts on the natural resource base from afforestation. A companion paper addresses irrigation recommendations based on species and local conditions (see Evett et al. 2000).

Ecosystem Services of Woody Crop Production Systems

Short-rotation woody crops are an integral component of regional and national energy portfolios, as well as providing essential ecosystem services such as biomass supplies, carbon sinks, clean water, and healthy soils. We review recent USDA Forest Service Research and Development efforts from the USDA Biomass Research Centers on the provisioning of these ecosystem services from woody crop production systems. For biomass, we highlight productivity and yield potential, pest susceptibility, and bioenergy siting applications. We describe carbon storage in aboveground woody biomass and studies assessing the provision of clean and plentiful water. Soil protection and wildlife habitat are also mentioned, in the context of converting lands from traditional row-crop agriculture to woody production systems.

Bud Removal Affects Shoot, Root, and Callus Development of Hardwood Populus Cuttings

Abstract The inadvertent removal and/or damage of buds during processing and planting of hardwood poplar (Populus spp.) cuttings are a concern because of their potential impact on shoot and root development during establishment. The objective of the current study was to test for differences in shoot dry mass, root dry mass, number of roots, length of the longest root, and callus dry mass among ten poplar clones subjected to three pre-planting bud removal intensities (0%, 50%, 100%). The ten clones and their genomic groups were: DM115 (P. deltoides Bartr. ex Marsh× P. maximowiczii A. Henry); DN34, I45-51 (P. deltoides× P. nigra L.); NC13446, NC13563, NC13649, NC13685, NC13747 [(P. trichocarpa Torr. & Gray× P. deltoides)× P. deltoides]; and NM2, NM6 (P. nigra× P. maximowiczii). Cuttings, 20 cm long, were processed from shoots collected January 2005 from stool beds established at Hugo Sauer Nursery in Rhinelander, Wisconsin, U.S.A. (45.6 °N, 89.4°W). We measured the traits from harvested cuttings after 14 d of growth. The treatment× clone interaction governed shoot dry mass (P < 0.0001). In general, the top four clones (DM115, DN34, NM2, NM6) exhibited the best shoot dry mass with 0% and 50% of buds removed, while differences among treatments for the remaining clones were negligible. Clones differed for root dry mass (P < 0.0001), while the treatment and clone main effects governed number of roots (P = 0.0126, P < 0.0001, respectively) and length of the longest root (P = 0.0077, P < 0.0001, respectively). Cuttings subjected to the 0% treatment exhibited the greatest number of roots, while cuttings of the 0% and 50% treatment exhibited the greatest length of the longest root. The treatment× clone interaction governed the presence of callus (P = 0.0161), while clones differed for callus dry mass (P < 0.0001). Bud removal did not affect root biomass but it did impact root initiation. Unlike shoot dry mass, the response to removing buds for all rooting traits was not clone-specific. From a practical standpoint, inadvertently damaging and/or removing ≤ 50% of the buds during processing and planting should not be a concern for establishment.

Developing woody crops for the enhancement of ecosystem services under changing climates in the north central United States

Short rotation woody crops belonging to the genera Populus L., Salix L., Pinus L., and Eucalyptus LHer. have provided broad economic and ecological benefits throughout the world, including afforestation and reforestation along urban to rural gradients. Within the genus Populus, cottonwoods, poplars, aspens, and their hybrids (hereafter referred to as poplars) have been shown to exhibit favorable genotype × environment interactions, especially in the face of changing climates. Similar growth responses have been reported for Pinus, especially with white pine (Pinus strobus L.) in the North Central United States. This has led to current research priorities focused on ecosystem services for both genera. The Millennium Ecosystem Assessment (2005) defines cultural, supporting, provisioning, and regulating ecosystem services. The overarching objective of this paper was to synthesize information about the potential of poplars to provide multiple ecosystem services when grown at sites with varying soil and climate conditions across landscape gradients from urban to rural areas. Specific objectives included: 1) providing background of the United States Forest Service and its Research and Development branch, 2) integrating knowledge of current poplar breeding and development with biomass provisioning and carbon regulating ecosystem services as they relate to changing climates in the North Central United States, and 3) providing a case study illustrating this integration through comparisons of poplar with white pine. Our results were evaluated in the context of climate change mitigation, with specific focus on selection of favorable genotypes for sequestering atmospheric carbon and reducing fossil fuel carbon emissions.

Environmental Technologies of Woody Crop Production Systems

Soil erosion, loss of productivity potential, biodiversity loss, water shortage, and soil and water pollution are ongoing processes that decrease or degrade provisioning (e.g., biomass, freshwater) and regulating (e.g., carbon sequestration, soil quality) ecosystem services. Therefore, developing environmental technologies that maximize these services is essential for the continued support of rural and urban populations. Genotype selection is a key component of these technologies, and characteristics of the species used in short rotation woody biomass systems, as well as the silvicultural techniques developed for short rotation woody crops are readily adapted to environmental applications. Here, we describe the development of such woody crop production systems for the advancement of environmental technologies including phytoremediation, urban afforestation, forest restoration, and mine reclamation. The primary goal of these collective efforts is to develop systems and tools that can help to mitigate ecological degradation and thereby sustain healthy ecosystems across the rural to urban continuum.

Mini-Review of Knowledge Gaps in Salt Tolerance of Plants Applied to Willows and Poplars

Salt tolerance of agricultural crops has been studied since the 1940, but knowledge regarding salt tolerance of woody crops is still in its initial phase. Salt tolerance of agricultural crops has been expressed as the yield decrease due to a certain salt concentration within the root zone as compared to a non-saline control. The most well-known plant response curve to salinity has been a piece-wise linear regression relating crop yield to root zone salinity. This method used the hypothesis that crops tolerate salt up to a threshold after which their yield decreases approximately linearly. Critique to this method included its lack of sensitivity to dynamic factors such as weather conditions. As a result, other classification indices have been developed, but none is as well accepted as the threshold-slope model. In addition to a mini-review of the key salt tolerance studies, our objective was to classify salt tolerance levels of poplars and willows. Initial classification showed that salt tolerance of these genera ranged from sensitive to moderately tolerant.

Biofuels, Bioenergy, and Bioproducts from Sustainable Agricultural and Forest Crops

This issue of BioEnergy Research highlights the Short Rotation Crops International Conference held in Bloomington, Minnesota in August 2008. This is the first special issue of BioEnergy Research, with several additional special issues planned in the next year, focused on the three U.S. Department of Energy Bioenergy Research Centers (Great Lakes Bioenergy Research Center, BioEnergy Science Center, and Joint BioEnergy Institute), and emerging technologies for biodiesel production. The purpose of these special issues is to highlight emerging research efforts in the areas of biomass, biofuels, and bioenergy. The Short Rotation Crops International Conference represented a unique opportunity for communication and interaction between researchers working on herbaceous and woody bioenergy feedstocks, one that we hope will continue to stimulate new interactions and creative solutions for bioenergy and bioproducts. We invite other groups to submit ideas for future special issues to one of the three co-Editors-inChief of BioEnergy Research. For quite some time, there has been a substantial need for an international conference integrating biological and social aspects of producing both herbaceous and woody crops for biofuels, bioenergy, and bioproducts. Increasing energy prices worldwide have made alternative sources economically feasible in recent times. Therefore, given substantial support from 26 sponsors representing both agricultural and forestry sectors, the Short Rotation Crops International Conference: Biofuels, Bioenergy, and Bioproducts from Sustainable Agricultural and Forest Crops was held in Bloomington, Minnesota during August 2008. This meeting combined world-leaders in herbaceous and woody biomass energy crops to present more than 90 papers on the state-of-the-art in sustainable energy production and policy. The conference goal was to create an international forum to strengthen old collaborations and create new partnerships to attack some of the pressing issues facing the world’s demand for energy. This special issue represents many of the extensive efforts underway to help understand these issues. We hope this collection will help to spark further conversations among scientists, academicians, regulators, and the general public. We encourage you to contact the authors to cultivate such discussions. M. D. Casler U.S. Department of Agriculture, Agricultural Research Service, U.S. Dairy Forage Research Center, 1925 Linden Drive, Madison, WI 53706, USA

Short rotation Populus: a bibliography of North American literature, 1989-2011

There have been three comprehensive poplar bibliographies dating back to 1854 and the most recent contained literature published through 1988. Given that these bibliographies are outdated, the number of forestry/bioenergy related journals has increased dramatically (along with subsequent publications), and there have been profound advances in science (particularly in the areas of genetics and molecular biology) within the past two decades, development of the current bibliography was necessary. In addition to compiling the information, our objectives were to encourage publication in peer-reviewed journals and to enhance collaborations with partners outside the poplar community. The current bibliography contains 864 unique citations that are cross-listed among as many as three topic areas, resulting in 1,395 total entries. The topic areas are cell and tissue culture, conservation, diseases, economics and social science, general, genetics, global change, growth and productivity, insects and mites, physiology, phytotechnologies, silviculture, and wood science and wood products.