Hybrid Poplar Production Research Articles

Planting Density and Site Effects on Stem Dimensions, Stand Productivity, Biomass Partitioning, Carbon Stocks and Soil Nutrient Supply in Hybrid Poplar Plantations

In this study, planting density and site effects on hybrid poplar productivity and stem dimensions were evaluated on the mid-term and longer term (8 and 14 years) in southern Québec (Canada). We also evaluated the effects of planting density and site on biomass accumulation and carbon stocks in different plantation compartments, on biomass partitioning at the stand-level, on soil carbon stocks and on soil nutrient supply rate after 14 years. The experimental design consisted of three replicate poplar stands located along a site fertility gradient. Each stand contained six planting densities (ranging from 494 to 1975 trees/ha) and a single genotype (Populus canadensis × P. maximowiczii hybrid). Planting density had a large effect on stem dimensions, but a minor effect on stand volume, aboveground woody biomass production, and aboveground biomass carbon stocks. Site selection and tree survival were more important factors affecting these variables. At all sites, and independent of planting density, mean annual volume increments were also higher after 14 vs. 8 years. On fertile sites, strong correlations between area per tree at planting and biomass partitioning, carbon allocation belowground, soil nutrient supply rate and soil carbon stocks were observed. Aboveground, higher competition for light with increasing planting density resulted in an increase in the stem to branch ratio. Belowground, higher competition for soil resources with increasing planting density reduced soil macronutrient availability (except for potassium), which likely stimulated carbon allocation belowground and carbon accumulation in the soil. Over the longer-term, higher density plantations of poplars could provide greater benefits in terms of carbon storage belowground (soil and roots).

Pest categorisation of Sphaerulina musiva.

Following a request from the European Commission, the EFSA Plant Health Panel performed a pest categorisation of Sphaerulina musiva, a well‐defined and distinguishable fungal species of the family Mycosphaerellaceae. Following a recent phylogenetic analysis of the genus Septoria and other closely related genera, a new name (S. musiva) was introduced for the species. The former species name Mycosphaerella populorum is used in the Council Directive 2000/29/EC. The pathogen is regulated in Annex IAI as a harmful organism whose introduction into the EU is banned. S. musiva is reported from North and South America and not known to occur in the EU. S. musiva causes Septoria leaf spots and cankers of poplar (Populus spp.). Of the poplars native to Europe, Populus nigra is reported as susceptible and Populus tremula as susceptible when planted in North America. The hybrid Populus x canadensis (arising from a cross of P. nigra and the North American Populus deltoides), widely grown in the EU, is also susceptible. The pest could enter the EU on plants for planting, cut branches, isolated bark and wood with and without bark. S. musiva could establish in the EU, as hosts are common and favourable climatic conditions are widespread, and could spread following establishment by natural dispersal and movement of infected plants for planting, cut branches, isolated bark and wood with or without bark. The pest introduction would have impacts in woodlands, plantations and nurseries. The pathogen is considered the most serious disease affecting hybrid poplar production in North America. Selection, breeding and planting of resistant species and clones are the main methods used to control the damage caused by the pathogen. There is some uncertainty on the geographical distribution of the pest in the Caucasus, the Crimean Peninsula and South America and on the level of susceptibility among Populus species native to Europe as well as Salix spp. The criteria assessed by the Panel for consideration as a potential quarantine pest are met. For regulated non‐quarantine pests, the criterion on the pest presence in the EU is not met.

Impacts of Supplyshed-Level Differences in Productivity and Land Costs on the Economics of Hybrid Poplar Production in Minnesota, USA

The joint effects of poplar biomass productivity and land costs on poplar production economics were compared for 12 Minnesota counties and two genetic groups, using a process-based model (3-PG) to estimate aboveground biomass productivity. The counties represent three levels of productivity which, due to spatial stratification, were analogous to three biomass supplysheds. An optimal rotation age (ORA) was calculated that minimizes the annualized, discounted per-dry megagrams biomass cost for each county, genetic group and land cover, and for two discount rates (5 and 10 %). The ORA for the lowest-cost county (Todd) with specialist genotypes and a 5 % discount rate is 14 years and the breakeven price at that age is US$71 dry Mg−1, while for the highest-cost county (McLeod), the generalist genotype and a 10 % discount rate, the ORA is 10 years and the breakeven price at that age is US$175 dry Mg−1. Planting after a previous poplar stand increased breakeven prices and increased the ORAs by 1 to 2 years relative to planting after a previous annual crop. An ANOVA analysis showed a significant genetic group effect and significant productivity class × land rent interactions. All other factors being equal, an increase in the discount rate from 5 to 10 % is expected to reduce ORAs by 2 to 3 years. High-productivity supplysheds can also be expected to have ORAs that are 2 to 3 years shorter than low-productivity ones. Land costs were not as closely correlated to productivity as we expected.

Effects of mixing clones on hybrid poplar productivity, photosynthesis and root development in northeastern Canadian plantations

Mixing tree cultivars or species in forest plantations can be efficient to reduce the risk of pest damages and could have a positive effect on yields if complementarity or facilitation between trees occurs. Four hybrid poplar clones (747215, Populus trichocarpa Torrey & A.Gray×P. balsamifera L.; 915004 and 915005, P. balsamifera×P. maximowiczii Henry; and 915319 P. maximowiczii×P. balsamifera) were planted in monoclonal and polyclonal plantations in three sites located in Quebec, Canada, to assess effects of clonal diversity on (i) aboveground biomass productivity, (ii) net photosynthesis and nutrient status of trees, and (iii) root spatial distribution. Stem growth was measured over five growing seasons, while root development, foliar nutrient concentrations and photosynthesis were measured during the fifth growing season. Results showed frequent but not general overyielding of trees in the polyclonal plots compared to monoclonal plots, five years after plantation establishment. Overall, stem volumes were 21% higher in the polyclonal (7.4m3ha−1) vs. monoclonal (6.1m3ha−1) plots. Effects of clone mixing on growth were greater in sites where soil nutrients were more limiting. However, foliar macronutrient concentrations (N, P, K, Ca and Mg) in trees growing in polyclonal plots were similar to those in monoclonal plots. Root development differed between the two plot layouts, with mean root:shoot ratio being greater in monoclonal (0.41:1) vs. the polyclonal (0.35:1) plots. Mixing clones increased biomass allocation aboveground, which we attributed to reduced competition between individuals of different clones and could explain overyielding in the polyclonal plots. The root fraction most distant from the stem (⩾60cm) was greater in monoclonal (67% of total root biomass) compared to polyclonal (47% of total root biomass) plots, suggesting greater belowground competition in the former, which forced roots to extend further from the stems. Effects of plot layout on net assimilation rate (Pn) depended on site, with trees in polyclonal plots having greater Pn in two of the three sites. Root total non-structural carbohydrates were greater in the polyclonal (216mgg−1) compared to the monoclonal (159mgg−1) plots. Mixing hybrid poplar clones often resulted in greater aboveground growth, lower root:shoot ratios, and different spatial root distributions, when compared to clones planted in monocultures.

Hybrid poplar (Populus spp.) adaptation to a semi-arid region: results from Northwest New Mexico (2002–2011)

A provenance test was initiated in spring 2002 at the New Mexico State University Agricultural Science Center at Farmington to examine the adaptability of various hybrid poplar (Populus spp.) crosses to the high elevation, semi-arid conditions of this region of the Southwestern United States. Ten crosses of P. deltoides, P. maximowiczii, P. nigra and P. trichocarpa obtained from nurseries in the Pacific Northwest were grown in replicates (3 plots × 16 trees) under drip irrigation programmed to match tree evapotranspiration (ET) rates. By the end of year 10, six crosses had maintained a 90 % or higher survival rate and had an average wood volume of 246 m3 ha−1. The P. deltoides × P. nigra (P. × canadensis) clone OP-367 surpassed a ten-year commercial target of 25-cm diameter at breast height (DBH) after eight seasons, and by the end of 2011 attained a DBH of 28.0 cm, height of 19.9 m and wood volume of 473 m3 ha−1. Results suggest that hybrid poplar production is possible in this type of semi-arid environment using appropriate germplasm and drip irrigation regimes scheduled according to tree ET demand.

Mature Hybrid Poplar Riparian Buffers along Farm Streams Produce High Yields in Response to Soil Fertility Assessed Using Three Methods

This study had three main objectives: (1) to evaluate the aboveground biomass and volume yield of three unrelated hybrid poplar clones in 9 year-old riparian buffer strips located on four farms of southern Québec, Canada; (2) to compare yield data at 9 years with previous data (at 6 years); (3) to evaluate how soil fertility, measured using three different soil testing methods (soil nutrient stocks, soil nutrient concentrations, soil nutrient supply rates), is related to yield. Across the four sites, hybrid poplar productivity after 9 years ranged from 116 to 450 m3ha−1, for stem wood volume, and from 51 to 193 megagrams per hectare (Mg ha−1), for woody dry biomass. High volume and woody dry biomass yields (26.3 to 49.9 m3ha−1yr-1, and 11.4 to 21.4 Mg ha−1yr-1) were observed at the three most productive sites. From year 6 to 9, relatively high yield increases (8.9−15.1 m3ha−1yr−1) were observed at all sites, but the productivity gap between the less fertile site and the three other sites was widened. Clone MxB-915311 was the most productive across the four sites, while clone DxN-3570 was the least productive. However, at the most productive site, clone MxB-915311 experienced severe stem and branch breakages. Independently of the soil testing method used, available soil P was always the first soil factor explaining volume yield.

Yield in 8 year-old hybrid poplar plantations on abandoned farmland along climatic and soil fertility gradients

We evaluate, after 8 growing seasons, the effect of climate and soil characteristics on the biomass and volume yields of eight hybrid poplar plantations established on abandoned farmland sites, all planted during the same week, with the same five unrelated clones (D×N, T×D, N×M, DN×M, and M×B hybrids), and with the same silvicultural treatments. These plantations are located along an elevation (from 80 to 450m), or climatic gradient, but also along an edaphic gradient (from rich bottomlands to poorer hillside slopes). The largest effect that affected poplar volume yield was the Site effect (F ratio=134), followed by the Clone effect (F ratio=17), both effects being highly significant (p<0.001). However, a highly significant Site×Clone interaction suggests that the unrelated hybrid poplar clones used in this study respond differently to the environmental gradients. The large Site effect was expressed by hybrid poplar yield (5 clones mean) being as high as 22.4m3ha−1year−1 in the bottomlands of the Bedford site, where all clones reached their highest yield, and as low as 1.1m3ha−1year−1 on the poorer soils of hill slopes at Stornoway. Only one clone was the highest yielding at all sites, the N×M hybrid.The yield extremes observed highlight the strong control of elevation (proxy for climate), but also site fertility in terms of P availability on hybrid poplar productivity after 8years. Results from the stepwise regressions showed that Populus maximowiczii hybrids (N×M, DN×M, and M×B) productivity was first influenced by P availability followed by elevation, while D×N and T×D hybrids productivity was primarily influenced by elevation followed by P availability. Hybrid poplars related to the Tacamahaca section, and especially P. maximowiczii hybrids, were therefore able to produce relatively high yields (above 10m3ha−1year−1) on fertile sites located at higher elevation. In addition, simple regression models between elevation and productivity showed that the M×B hybrid, which has both of its parents from the Tacamahaca (balsam poplar) section, was the least influenced by elevation, an indication of its greater adaptation to colder climate.Because all clones strongly responded to soil P availability, clone selection cannot compensate for inadequate site selection in terms of soil fertility. Choosing high fertility abandoned farmland sites is therefore of paramount importance for hybrid poplar production.

Influence of Climate on the Growth of Hybrid Poplar in Michigan

This study examined the influence of climate on cumulative and interannual growth patterns of 18 full-sib families of hybrid poplars (Populus × smithii Boivin) derived from different geographical locations (state counties) of natural stands of aspen parents (trembling aspen (Populus tremuloides Michx.) and bigtooth aspen (Populus grandidentata Michx.)). The hybrids were subsequently planted in 1982 in southern mid-Michigan at Michigan State University (MSU) Sandhill Research Area. Cumulative measures of hybrid poplar productivity (diameter, height, basal area, and stem volume) in 2009 (28 years since plantation establishment) were related via correlation analysis to geographical distances and climatic variables (temperature and precipitation) between parental county locations and between parental locations and the plantation site. Tree-ring analysis methods (dendrochronology) were also used to quantify the influence of climate (i.e., mean temperature and total precipitation at monthly and 3-month seasonal scales) on interannual basal area growth rates of hybrid poplars. Analyses of cumulative measures of growth indicated a maternal effect: full-sib families had higher productivity if they had a maternal parent originating from a state county that was close to or had higher temperature (annual and summer) and summer precipitation than corresponding parameters of the planting site. Principal component analysis indicated that 17 of the 18 full-sib families shared a large amount of common growth variation. Dendrochronological analyses of interannual growth-climate relationships indicated that growth was mainly affected by the degree of late summer to fall moisture stress in both the current and previous growth season, and the degree of winter harshness.

Predicting the productivity of a young hybrid poplar clone under intensive plantation management in northern Alberta, Canada using soil and site characteristics

Site productivity of the hybrid poplar clone Brooks6 was predicted using soil and site information from 6, 4-year-old plantations in north-east Alberta. Predictions were made at both the local and microsite scales. Percent sand (R2 = 0.352, P = 0.001) was the best single predictor of hybrid poplar productivity, showing a curved relationship. Soil pH also showed a curved but weaker relationship with hybrid poplar productivity (R2 = 0.133, P = 0.100). Maximum tree productivity occurred at sand contents between 55 and 70% and pH values near 6. Other variables, including foliar nutrient concentrations, foliar δ13C, electrical conductivity, depth of the A horizon and total chemistry of the soil, were also related to hybrid poplar productivity at the local and microsite scales. However, all of these variables were correlated to either soil texture (percent sand) or pH. At the microsite scale within plantations, percent sand was the most important predictor of tree productivity and explained more than 50% of the variability within plantations, although the relationship varied by plantation. In plantations with fine textures, sandier microsites were associated with increased growth while in sandy plantations, finer textured microsites were more productive. As a whole, the growth of the hybrid poplar clone Brooks6 appears to be mostly influenced by a combination of soil water and nutrient availability, the former being impacted by soil texture and the latter being governed by soil pH.

Nursery stock type, nitrogen fertilization and shoot pruning effects on the growth of juvenile hybrid poplar in Saskatchewan

Increased demand for wood from the forest-products and bio-energy industries in Canada has generated interest in large-scale hybrid poplar production for the prairie-boreal transition region. Because of the harsh climate and short growing season, this region of Canada poses significant challenges for establishment and production of hybrid poplar plantations and currently little silviculture information specific to this region is available. Trials were established at two sites with different prior land use histories: a former alfalfa field and a mixed-grass pasture. Cutting (Ct), rooted cutting (RCt) and rooted plug (RPg) nursery stock of hybrid poplar [P. deltoides × (P. laurifolia × P. nigra) var. Walker] were established with two fertilization rates (0 and 100 kg N ha-1) and pruned and unpruned treatments. Despite the alfalfa site having higher amounts of available N than the pasture site and tree growth being superior at the alfalfa site, foliar N concentrations indicated an N deficiency at the alfalfa site in 2003. The difference in growth between sites was attributed to a higher degree of weed competition at the pasture site. Survival of saplings was affected by the nursery stocks. The presence of roots on the initial stock was key to early survival with approximately 92% of rooted stocks surviving over winter the first year of planting, and only 41% of unrooted cuttings surviving the same period. The short growing seasons (115 to 127 frost-free days) provided enough time for RCt to recover from pruning and produce stem volumes larger than unpruned trees. For reasons unknown, RPg did not fully recover from pruning and stem volumes in 2003 and 2004 were lower than unpruned trees. Although expectations of rates of growth of hybrid poplar are lower in the prairie-boreal transition region of Canada compared with regions of North America with more moderate climates, establishment of plantations can be realized with aggressive weed control and selection of rooted stock materials. Key words: Cuttings, rooted cuttings, rooted plugs, cultural practices, Walker

Environmental Effects of Biosolids Trenching for Reclaiming Mined Land for Hybrid Poplar Production

Environmental Effects of Biosolids Trenching for Reclaiming Mined Land for Hybrid Poplar Production

Growth and Survival of Drip-Irrigated Hybrid Poplar in the Semi-Arid Four Corners Region

Rapid growth rates and versatility have made hybrid poplar (Populus L.) a common choice to fulfill timber and pulp needs in temperate regions with adequate precipitation. Hybrid poplar production in drier regions has recently received interest as an irrigated source of cut logs and shredded fiber. Ten hybrid poplar clones were selected from nurseries in Washington and Oregon to determine their growth potential and water-use requirements on a calcareous soil at the NMSU Agricultural Science Center in Farmington, NM. Planted in May 2002, the clones were evaluated for survival growth characteristics over two seasons. Clones 50-194 and 184-411 had poor survival and were not continued during the 2003 season. Clone OP-367 had low chlorosis ratings, the greatest height (4.16 m), basal diameter (9.16 cm), diameter at breast height (4.65 cm) and wood volume (2.87 m3 ha-1) during both seasons. A range of responses to environmental conditions of the Four Corners region was exhibited. Mid-season leaf greenness, as determined with a SPAD-502 chlorophyll meter, was a good predictor of growth characteristics. OP-367 appeared to be a potential candidate for inclusion in drip-irrigated wood production strategies for this and other arid/semi-arid regions of the world.

Electronic Data Collection for Tomorrow's Forest

The Fast Growing Forests Technology Development Group is committed to the development and transfer of forest management technology. To improve the efficiency of data collection and the integrity of the data collected, the group has implemented a system of electronic data collection utilizing the DAP Microflex and PC1000 hand-held units. Programs have been developed for applications such as field trial data collection, timber cruising the Larose Agreement Forest and Domtar hybrid poplar production plantation forest, stand marking, cold storage inventory, log scaling, plus tree collection, electronic weigh scales and other related forestry applications.