Populus Deltoides Research Articles

Novel Integration of Geopolymer Pavers, Silva Cells and Poplar Trees for In-Situ Treatment of Car-Wash Wastewater

This paper presents an eco-friendly, low-impact development (LID) approach, developed and implemented at a car wash site for a cleaner and greener environment. In this approach, the contaminated water discharged after car washing is treated as it is directed through an engineered, ecology-based water-management design. The design involves poplar (Populus deltoides) trees, Silva Cells®, and Fly-ash based Geopolymer concrete pavers working collectively to minimize the percolation of contaminants into the soil. In this novel system, each component has a vital role. For instance, the extensive roots of the poplar trees enable water filtration owing to phytoremediation effect; while the Silva Cells® promote stormwater management, planting of poplar trees and serve as a foundation for paver blocks. Lastly, the paver blocks made from industrial waste allow it to withstand urban load and infiltrate water runoff, thereby reducing runoff quantities. To evaluate the efficacy of contaminant uptake by this system, pH, electrical conductivity and turbidity, which are indicators of water quality levels, were monitored pre- and post-treatment. The percentage change in total dissolved solids indicates the potential of this treatment system for effective treatment of the contaminated car wash water.

Ecosystem Services, Physiology, and Biofuels Recalcitrance of Poplars Grown for Landfill Phytoremediation.

Long-term poplar phytoremediation data are lacking, especially for ecosystem services throughout rotations. We tested for rotation-age differences in biomass productivity and carbon storage of clones Populus deltoides Bartr. ex Marsh × P. nigra L. ‘DN34′ and P. nigra × P. maximowiczii A. Henry ‘NM6′ grown for landfill phytoremediation in Rhinelander, WI, USA (45.6° N, 89.4° W). We evaluated tree height and diameter, carbon isotope discrimination (Δ), and phytoaccumulation and phytoextraction of carbon, nitrogen, and inorganic pollutants in leaves, boles, and branches. We measured specific gravity and fiber composition, and determined biofuels recalcitrance of the Rhinelander landfill trees versus these genotypes that were grown for biomass production on an agricultural site in Escanaba, MI, USA (45.8° N, 87.2° W). ‘NM6′ exhibited 3.4 times greater biomass productivity and carbon storage than ‘DN34′, yet both of the clones had similar Δ, which differed for tree age rather than genotype. Phytoaccumulation and phytoextraction were clone- and tissue-specific. ‘DN34′ generally had higher pollutant concentrations. Across contaminants, stand-level mean annual uptake was 28 to 657% greater for ‘NM6′, which indicated its phytoremediation superiority. Site-related factors (not genotypic effects) governed bioconversion potential. Rhinelander phytoremediation trees exhibited 15% greater lignin than Escanaba biomass trees, contributing to 46% lower glucose yield for Rhinelander trees.

Floodplain forest dynamics: Half‐century floods enable pulses of geomorphic disturbance and cottonwood colonization along a prairie river

AbstractIn dry ecoregions, trees are restricted to river valley floodplains where river water supplements the limited local precipitation. Around the Northern Hemisphere, cottonwoods, riparian poplars, are often predominant trees in floodplain forests and these ecological specialists require floods that create and saturate sand and gravel bars, enabling seedling recruitment. By pairing the interpretation of aerial photographs at approximately decade intervals with dendrochronology, we explored the coordination between river floods, geomorphic disturbance and colonization of plains cottonwoods (Populus deltoides) over eight meanders along the Red Deer River in the semi‐arid prairie of western Canada. This river has a relatively natural flow regime and minimal human alteration through the World Heritage Site of Dinosaur Provincial Park. We found that the 50‐year flood of 1954 increased channel migration and produced extensive accretion with downstream expansion of meander lobes and some channel infilling, which was followed by prolific cottonwood colonization. Those processes accompanied the major flood, while bank erosion and cottonwood losses were more gradual and continuous over the past half‐century. Results indicated even greater floodplain and woodland development after an earlier 100‐year flood in 1915. Each flood produced an arcuate band of mature cottonwoods and there were five to seven progressively older woodland bands across the floodplain, with each cottonwood age grouping increasing by about a half‐century. The 700 m wide floodplain was progressively reworked by the river through pulses of channel movement and floodplain and woodland development over approximately 250 years and correspondingly, the oldest cottonwoods were about 250 years old.

Bacterial Canker Disease on Populus × euramericana Caused by Lonsdalea populi in Serbia

Populus × euramericana (Dode) Guinier clone (cl.) “I-214” is a fast-growing interspecific hybrid between Eastern cottonwood (P. deltoides Bartr. ex Marsh) and European black poplar (Populus nigra L.). Populus × euramericana was introduced into Serbia in the 1950s and has become one of the most widely grown poplar species. In September 2019, cankers were observed on stems and branches of P. × euramericana cl. “I-214” trees in a two-year-old poplar plantation in the province of Vojvodina, Serbia. The canker tissue was soft and watery, and a colorless fluid that smelled rotten flowed from the cracks in the bark, suggesting possible bacterial disease. After two weeks, diseased trees experienced crown die-back and oozing of foamy, odorous exudates and this study aimed to identify the causal agent of the disease. Canker margins and exudates were collected from 20 symptomatic trees. The associated bacterium was isolated and identified using biochemical characteristics, phylogenetic analyses based on 16S rRNA gene sequences, and multilocus sequence analyses (MLSA) based on partial sequencing of three housekeeping genes (gyrB, infB, and atpD). The pathogen was identified as Lonsdalea populi. Pathogenicity tests were conducted on rooted cuttings of P. × euramericana cl. “I-214” in an environmental test chamber and demonstrated that the isolated bacterial strain was able to reproduce symptoms of softened, water-soaked cankers and exudation. To the best of our knowledge, this is the first report of L. populi causing bacterial canker disease on P. × euramericana cl. “I-214” in Serbia and in southeastern Europe (SEE). It is also the first report of a bacterial disease on hybrid poplars, including P. × euramericana in this country and in SEE. If the disease spreads into new areas, selection for L. populi resistance may need to be integrated into future poplar breeding programs.

Molecular Remodeling in Populus PdKOR RNAi Roots Profiled Using LC-MS/MS Proteomics.

Plant endo-β-1,4-glucanases belonging to the Glycoside Hydrolase Family 9 have functional roles in cell wall biosynthesis and remodeling via endohydrolysis of (1→4)-β-d-glucosidic linkages. Modification of cell wall chemistry via RNA interference (RNAi)-mediated downregulation of Populus deltoides KORRIGAN (PdKOR), an endo-β-1,4-glucanase familygene was shown to have functional consequences on the composition of secondary metabolome and the ability of modified roots to interact with beneficial microbes. The molecular remodeling that underlies the observed differences at metabolic, physiological, and morphological levels in roots is not well understood. Here a liquid chromatography (LC)-tandem mass spectrometry (MS/MS)-based proteome profiling approach is used to survey the molecular remodeling in root tissues of PdKOR and control plants. A total of 14316 peptides are identified and these mapped to 7139 P. deltoides proteins. Based on 90% sequence identity, the measured protein accessions represent 1187 functional protein groups. Analysis of Gene Ontology (GO) categories and specific individual proteins show differential expression of proteins relevant to plant-microbe interactions, cell wall chemistry, and metabolism. The new proteome dataset serves as a useful resource for deriving new hypotheses and empirical testing pertaining to functional roles of proteins and pathways in differential priming of plant roots to interactions with microbes.

Evaluation of the analgesic activity of ethanolic extract of Populus deltoides leaves in mice

The ethanolic leaves extract of Populus deltoides was tested for the presence of various phytoconstituents and designed to evaluate the analgesic activity in mice. The peripheral analgesic activity of ethanolic leaves extract of P.deltoides (250 and 500 mg/kg) was studied by using acetic acid stimulated writhing test and central analgesic activity of P.deltoides was studied by using hotplate process. The ethanolic leaves extract of P.deltoides professed the existence of a variety of chemical constituents like alkaloids, saponins, flavonoids, terpenes and steroids. Leaves extract of P.deltoides appreciably decreased the writhing actions in acetic acid-induced writhing test in mice and amplified the respond time in hotplate test. These results suggest that the extract may have NSAIDs like activity through the peripheral mechanism and central analgesic activities via opioid receptors. From our study, we endowed that leaves extract of P.deltoides has feasible to analgesic activity. This study reveals that it can be used in the management of pain and provide a scientific basis for its traditional use.

Wood forming tissue-specific expression of PdSuSy and HCHL increases holocellulose content and improves saccharification in Populus

Development of strategies to deconstruct lignocellulosic biomass in tree species is essential for biofuels and biomaterials production. We applied a wood forming tissue-specific system in a hybrid poplar to express both PdSuSy (a sucrose synthase gene from Populus deltoides × P. euramericana that has not been functionally characterized) and HCHL (the hydroxycinnamoyl-CoA hydratase-lyase gene from Pseudomonas fluorescens, which inhibits lignin polymerization in Arabidopsis). The PdSuSy-HCHL overexpression poplars correspondingly driven by the promoters of Arabidopsis AtCesA7 and AtC4H resulted in a significant increase in cellulose (> 8%), xylan (> 12%) and glucose (> 29%) content, accompanying a reduction in galacturonic acid (> 36%) content, compared to control plants. The saccharification efficiency of these overexpression poplars was dramatically increased by up to 27%, but total lignin content was unaffected. These transgenic poplars showed inhibited growth characteristics, including > 16% reduced plant height, > 10% reduced number of internodes, and > 18% reduced fresh weight after growth of 4 months, possibly due to relatively low expression of HCHL in secondary xylem. Our results demonstrate the structural complexity and interaction of the cell wall polymers in wood tissue and outline a potential method to increase biomass saccharification in woody species.

Spatial analysis of area and carbon stocks under Populus deltoides based agroforestry systems in Punjab and Haryana states of Indo-Gangetic Plains

Various agroforestry systems are prevalent in different agro-climatic regions of India and occupy sizeable area. Populus deltoides (poplar) based agroforestry systems are very predominant in Indo-Gangetic Plains of northern India. These systems are not only meeting wood demand of wood-based industries but also contributing significantly in generating employment, reducing atmospheric CO2 vis-a-vis mitigating climate change. The present study aimed at estimating area under poplar plantations and assessment of biomass production and carbon stock at district level for selected districts of Punjab and Haryana states. High resolution multispectral remote sensing data (LISS-IV, spatial resolution- 5.8 m) have been used for mapping poplar area in these districts. Growth data (tree density, diameter at breast height) from farmers’ fields were collected for assessment of aboveground and total biomass. Poplar area in Hoshiarpur, Rupnagar, Ludhiana, Shahid Bhagat Singh Nagar, Yamunanagar, Kurukshetra and Karnal districts accounted for 3.19, 4.09, 1.02, 0.43, 7.25, 1.58 and 0.97%, respectively, of their geographical area. As percentage of agroforestry area, poplar area occupied 43.8% in four districts of Punjab and 53.4% in three districts of Haryana. Estimated carbon stock in total biomass of poplar plantations was 0.931, 0.481, 0.287, 0.040, 0.949, 0.256 and 0.229 million tonnes, respectively. CO2 equivalent C in aboveground and total biomass was estimated to be 7.854 and 9.946 million t, respectively, in all these seven districts. The proposed methodology based on object-oriented image classification showed promising results as far as mapping of agroforestry systems/species is concerned.

High-Quality SNP Linkage Maps Improved QTL Mapping and Genome Assembly in Populus.

With the advances in high-throughput sequencing technologies and the development of new software for extracting single nucleotide polymorphisms (SNPs) across a mapping population, it is possible to construct high-quality genetic maps with thousands of SNPs in outbred forest trees. Two parent-specific linkage maps were constructed with restriction site-associated DNA sequencing data from an F1 hybrid population derived from Populus deltoides and Populus simonii, and applied in QTL mapping and genome assembly. The female P. deltoides map contained 4018 SNPs, which were divided into 19 linkage groups under a wide range of LOD thresholds from 7 to 55. The male P. simonii map showed similar characteristics, consisting of 2097 SNPs, which also belonged to 19 linkage groups under LOD thresholds of 7 to 29. The SNP order of each linkage group was optimal among different ordering results from several available software. Moreover, the linkage maps allowed the detection of 39 QTLs underlying tree height and 47 for diameter at breast height. In addition, the linkage maps improved the anchoring of 689 contigs of P. simonii to chromosomes. The 2 parental genetic maps of Populus are of high quality, especially in terms of SNP data quality, the SNP order within linkage groups, and the perfect match between the number of linkage groups and the karyotype of Populus, as well as the excellent performances in QTL mapping and genome assembly. Both approaches for extracting and ordering SNPs could be applied to other species for constructing high-quality genetic maps.

Understanding physiological and molecular mechanisms of Populus deltoides ‘DanHongYang’ tolerance to waterlogging by comparative transcriptome analysis

Populus deltoides ‘DanHongYang’ (DHY) was identified as a waterlogging-resistant cultivar in our previous study. Here, the phenotype, physiological features and transcriptome profiling of P. deltoides ‘DHY’ between the treatments of waterlogging and control were compared. Waterlogging treatment led to distinctly formation of adventitious roots from P. deltoides ‘DHY’ stems. The activities of ascorbate peroxidase and glutathione reductase significantly increased in the leaves of P. deltoides ‘DHY’ by waterlogging treatment. Comparative transcriptomic analysis showed that 2,447 and 9,465 differentially expressed genes (DEGs) were screened between the leaves and roots of P. deltoides ‘DHY’ under waterlogging and control, respectively. The KEGG analysis showed the most significantly up-regulated DEGs in the leaves and roots were enriched to the pathways of glycolyis and proline synthesis. Some genes involved in stress response, endogenous hormones, antioxidant system and adventitious root development in the waterlogged were identified to contribute to the waterlogging tolerance of P. deltoides ‘DHY’. In addition, some candidate transcription factors such as RAP, NAC, WRKY, and bHLH were also found to be associated with the waterlogging tolerance of P. deltoides ‘DHY’. These findings provided the insights into the physiological and molecular mechanisms underlying the tolerance of P. deltoides ‘DHY’ to waterlogging stresses.

Clonal Variation in Growth Response of Populus deltoides Bartr. to Nitrogen Fertilization Under Nursery Conditions

Populus deltoides, an extensively planted poplar in Jammu and Kashmir and is one of the ten most prominent tree species grown in the State. A strapping clone x fertilizerinteraction was observed fordiameter, height and biomass. Growth response of six male clones of this species to three levels ofnitrogen (50, 75 and100 kg ha 1 ) was evaluated in nursery for two years to produce healthy and vigorous nursery stock. While application of N- fertilizer @ 75 kg ha 1 recorded maximum height, diameter, number of branches plant', numberofleaves plant', leafarea plant', internodal length and total biomass (fresh and dry) plant', the application of 100 kg N ha ' was observed to exert toxic effects and reduced the growth performance. In terms ofefficient utilization ofNitrogen fertilizer (NUE), the application of 50 kg N ha ' yield maximum biomass p er unit of N- used by the plant. The male clones have recently received a lot of attention due to the increasing cotton mince produced by female clones in Kashmir valley. In currentscenario male clones are the betterperspective to replace the female ones without compromising the economy generated by this species.

Relationship between pore structure and gas permeability in poplar (Populus deltoides CL.\u201955/65\u2019) tension wood

Key messageThe important anatomical changes in tension wood, e.g., the high fiber ratio and rich mesopores, did not significantly increase the air and nitrogen flow; thus the gas permeability in the longitudinal direction of poplar (Populus deltoidesCL.’55/65′) tension wood is actually affected by the cell tissue macroporous porosity.ContextGas permeability is one of the most important physical properties of wood and is closely related to its internal microstructure, particularly porosity. Tension wood is widespread in woody plants and displays significant structural differences compared with opposite wood.AimsThe study was designed to clarify the relationship between pore structure and gas permeability in poplar tension wood.MethodsThe gas permeability was measured using a self-made device. The meso- and macroporosity characteristics were measured by nitrogen adsorption–desorption and mercury intrusion porosimetry. The flow was simulated using ANSYS Fluent software to illustrate the role of pore structure on permeability.ResultsThe morphological features of vessels have an effect on wood permeability. Compared with tension wood, opposite wood, which has higher vessel ratio, larger cell lumen diameter, and more rich pits, shows stronger gas permeability. Increasing the airflow path will actually reduce the gas permeability. The simulation results are consistent with the experimental results.ConclusionIn hardwoods, the gas permeability in the longitudinal direction is mainly dictated by the vessels. The high fiber ratio and rich mesopore in tension wood do not significantly increase gas flow, suggesting the permeability of wood was actually determined by the cell tissue with macroporous porosity. Vessel tissue ratio, length and diameter, and intervessel pit size were found responsible for influencing the permeability in the longitudinal direction.

Investigation of urea usage in soda pulping of Populus deltoides

Investigation of urea usage in soda pulping of Populus deltoides

The effect of cutting technique on the mortality and resprouting vigor of poplar stumps in short-rotation plantations

Mechanical felling is the most cost-effective solution for harvesting short-rotation poplar plantations, but the damage inflicted by conventional shear-cutting devices on tree stumps has raised concerns about stump mortality and resprouting vigor, both of which are crucial to coppice regeneration. To determine whether such concerns are justified, this experiment monitored the survival and resprouting vigor of 11 sample blocks composed of two 10-stump row segments that were cut according to one of two methods: (1) a chainsaw or (2) an excavator-mounted shear. The sample blocks were located within the same plantation, established 7 years earlier with hybrid poplars (Populus nigra × Populus deltoides) belonging to the AF8 clone. One year after cutting, no differences were found between treatments in terms of stump mortality, number of shoots per stump, shoot diameter at 30 cm from the insertion, or shoot height. These results support the use of mechanical shears to fell short-rotation poplar coppice. However, further studies should be conducted on multiple fields and clones in order to safely generalize these preliminary findings.

Accelerating forest tree breeding by integrating genomic selection and greenhouse phenotyping.

Breeding forest species can be a costly and slow process because of the extensive areas needed for field trials and the long periods (e.g., five years) that are required to measure economically and environmentally relevant phenotypes (e.g., adult plant biomass or plant height). Genomic selection (GS) and indirect selection using early phenotypes (e.g., phenotypes collected in greenhouse conditions) are two ways by which tree breeding can be accelerated. These approaches can both reduce the costs of field-testing and the time required to make selection decisions. Moreover, these approaches can be highly synergistic. Therefore, in this study, we used a data set comprising DNA genotypes and longitudinal measurements of growth collected from a population of Populus deltoides W. Bartram ex Marshall (eastern cottonwood) in the greenhouse and the field, to evaluate the potential impact of integrating large-scale greenhouse phenotyping with conventional GS. We found that the integration of greenhouse phenotyping and GS can deliver very early selection decisions that are moderately accurate. Therefore, we conclude that the adoption of these approaches, in conjunction with reproductive techniques that shorten the generation interval, can lead to an unprecedented acceleration of selection gains in P. deltoides and, potentially, other commercially planted tree species.

Quantifying vertical profiles of biochemical traits for forest plantation species using advanced remote sensing approaches

Biochemical traits in forest vegetation are key indicators of leaf physiological processes, specifically photosynthetic and other photochemical light pathways, and are critical to the quantification of the terrestrial carbon cycle. Advances in remote sensing sensors and platforms are allowing multi-dimensional and continuous-spatial information to be acquired in a fast and non-destructive way to quantify forest biochemical traits at multiple spatial scales. Here we demonstrate the use of high spectral resolution, hyperspectral data combined with high density three-dimensional information from Light Detection and Ranging (LiDAR) both acquired from an unmanned aerial system (UAS) platform, to quantify and assess the three-dimensional distribution of biochemical pigments on individual tree canopy surfaces. To do so, a DSM based fusion method was developed to integrate the 3D LiDAR point cloud with hyperspectral reflectance data. Regression-based models were then developed to predict a number of biochemical traits (i.e., chlorophyll (Chl) a, b, total Chl and total carotenoids (Cars) content) from a suite of common spectral indices at three vertical canopy levels, and were evaluated using a leave-one-out cross-validation approach. One-way ANOVA and Duncan's multiple comparison post hoc tests were used to investigate the vertical distribution of biochemical pigments on individual tree canopy surfaces, and in response to age and species. Our results demonstrated that a number of vegetation indices, derived from the hyperspectral data, were strongly correlated with a number of biochemical traits (Adj-R2 = 0.85–0.91; rRMSE = 5.19–6.38%). In general, models fitted using leaf samples from the upper, middle and lower canopies separately (Adj-R2 = 0.85–0.91; rRMSE = 5.19–6.38%) had similar accuracy to the models developed with pooled data (Adj-R2 = 0.87–0.90; rRMSE = 5.21–6.11%). The differences between separate models and global models were not statistically significant (P > 0.05). However, the distribution of biochemical pigments across vertical layers varied significantly. For dawn redwood (Metasequoia glyptostroboides) and poplar (Populus deltoides), the results were consistent in that the lower component of the canopy (least light impacted) had the highest chlorophyll and carotenoids biochemical traits. Moreover, the vertical distribution of biochemical traits on individual tree canopy surfaces changed with age likely due to the growth variation from the photosynthetic activity of the canopy. This study indicates the potential of using fused 3D point cloud information with spectral data to monitor physiological activities of forest canopy for carbon accumulation estimation as well as precision forestry applications such as nutrition diagnosis, water regulation and subsequent productivity enhancement of these planted forest systems.

Riparian plant species differ in sensitivity to both the mean and variance in groundwater stores

Abstract Aims Determining the ecological consequences of interactions between slow changes in long-term climate means and amplified variability in climate is an important research frontier in plant ecology. We combined the recent approach of climate sensitivity functions with a revised hydrological ‘bucket model’ to improve predictions on how plant species will respond to changes in the mean and variance of groundwater resources. Methods We leveraged spatiotemporal variation in long-term datasets of riparian vegetation cover and groundwater levels to build the first groundwater sensitivity functions for common plant species of dryland riparian corridors. Our results demonstrate the value of this approach to identifying which plant species will thrive (or fail) in an increasingly variable climate layered with declining groundwater stores. Important Findings Riparian plant species differed in sensitivity to both the mean and variance in groundwater levels. Rio Grande cottonwood (Populus deltoides ssp. wislizenii) cover was predicted to decline with greater inter-annual groundwater variance, while coyote willow (Salix exigua) and other native wetland species were predicted to benefit from greater year-to-year variance. No non-native species were sensitive to groundwater variance, but patterns for Russian olive (Elaeagnus angustifolia) predict declines under deeper mean groundwater tables. Warm air temperatures modulated groundwater sensitivity for cottonwood, which was more sensitive to variability in groundwater in years/sites with warmer maximum temperatures than in cool sites/periods. Cottonwood cover declined most with greater intra-annual coefficients of variation (CV) in groundwater, but was not significantly correlated with inter-annual CV, perhaps due to the short time series (16 years) relative to cottonwood lifespan. In contrast, non-native tamarisk (Tamarix chinensis) cover increased with both intra- and inter-annual CV in groundwater. Altogether, our results predict that changes in groundwater variability and mean will affect riparian plant communities through the differential sensitivities of individual plant species to mean versus variance in groundwater stores.

Emission Characteristics of Biogenic Volatile Compounds (BVOCs) from Common Greening Tree Species in Northern China and Their Correlations with Photosynthetic Parameters

In order to understand the emission characteristics of common greening trees in Beijing and analyze their correlations with photosynthetic parameters, including the net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (ci), and transpiration rate (Tr), we collected samples of biogenic volatile organic compounds (BVOCs) using a dynamic sampling technique from 14 species of deciduous trees. The results showed that there were significant differences in isoprene and total BVOC emissions between family or genus levels (P<0.01). With the exception of Lonicera maackii Maxim and Ulmus pumila L., all species were found to emit isoprene, monoterpenes, and sesquiterpenes, of which, species from the Salicaceae (e.g., Populus deltoides cv. '55/56'× P.deltoides cv. 'Imperial', P. euramericana cv. '74/76', Populus simonii Carr, and Salix babylonica) and Legume (Sophora japonica, Robinia pseudoacacia, and S. japonica Linn. var. japonica f. pendula Hort) families were the higher isoprene emitters, with emission rates that ranged from (30.1±4.3) μg·(g·h)-1 to (91.8±10.0) μg·(g·h)-1. Plants from the Oleaceae (e.g., Fraxinus chinensis Roxb and Syringa oblata Lindl), Begonia (Malus prunifolia), Sapindaceae (Koelrenteria paniculate), and Aceraceae (Acer truncatum Bunge) families mainly emitted monoterpenes and sesquiterpenes. Among them, Fraxinus chinensis Roxb and Acer truncatum Bunge were the highest emitters with emission rates of (10.6±4.8) μg·(g·h)-1 and (11.8±6.4) μg·(g·h)-1, respectively. Ocimene and β-pinene were the two main monoterpenes emitted from greening tree species. No significant correlations were found between the emission of BVOCs and Pn or gs, while the emission rate of isoprene (r=0.681; P<0.01) and the total BVOC (r=0.698; P<0.01) from the Salicaceae family increased with increasing Tr. Moreover, leguminous plants showed a significant positive correlation between the total BVOC emission rate and ci (P=0.04). This study provides a scientific reference for the selection and configuration of urban greenery, and a theoretical basis for exploring the mechanism of BVOC emissions.

Soil respiration and net ecosystem productivity in a chronosequence of hybrid poplar plantations

Forest stand age can affect ecosystem carbon (C) cycling and net ecosystem productivity (NEP). In Canada, establishment of short-rotation plantations on previously agricultural lands has been ongoing, but the effect of stand development on soil respiration (Rs) and NEP in such plantations is poorly understood. These types of data are essential for constraining ecosystem models that simulate C dynamics over the rotation of a plantation. We studied Rs (including autotrophic, Ra, and heterotrophic, Rh) and NEP in 2008 and 2009 in a chronosequence of 5-, 8-, 14-, and 16-yr-old (ages in 2009) hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) plantations in northern Alberta. The highest Rs and NEP were generally found in the 14-yr-old stand. Seasonal variations in Rs were similar among the plantations, with most of the variation explained by soil temperature at the 10 cm depth in 2008 with far less explained in 2009, a much drier year. In diurnal measurements, hysteresis was found between soil respiration and soil temperature, with the patterns of hysteresis different among stand ages. Soil respiration in the 14-yr-old plantation had the greatest sensitivity to temperature changes. Stand age did not affect the Rh:Rs ratio, whereas the NEP exhibited strong inter-annual variability. We conclude that stand age was a major factor affecting Rs and NEP, and such effects should be considered in empirical models used to simulate ecosystem C dynamics to evaluate potentials for C sequestration and the C source–sink relationship in short-rotation woody crop systems.

The practice and economics of hybrid poplar biomass production for biofuels and bioproducts in the Pacific Northwest

Hybrid poplar demonstration-scale farms were managed in Oregon, Washington, Idaho, and California to establish management practices, yields, harvesting methods, and the economics of biomass production. Yield during the 2-year establishment cycle averaged 3.5 dry Mg ha−1 year−1 increasing to 11.6 Mg ha−1 year−1 in the ensuing 3-year coppice cycle. Populus deltoides (Bartram ex Marsh.) × P. maximowiczii (Henry) varieties preformed best in Oregon during the coppice cycle with the best variety producing 18.1 Mg ha−1 year−1, while P. ×generosa (Henry) varieties maximized yields in Washington at 22.1 Mg ha−1 year−1. P. ×canadensis (Moench) varieties excelled in Idaho and California with upper yields of 13.6 Mg ha−1 year−1 and 12.9 Mg ha−1 year−1, respectively. Stands were cut with a single-pass harvester 2 years after planting and a second time after 3 years of coppice growth; material capacity, limited by poor ground conditions, varied between 21.7 to 31.3 green Mg h−1. Chemical composition averaged 1.87% inorganics, 7.74% extractives, 26.90% lignin, 38.07% glucan, 13.66% xylan, 1.61% galactan, 1.14% arabinan, and 2.76% mannan. Production costs (USD) projected over a 20-year rotation of six coppice cycles were $71.81 Mg−1 in Washington, $89.91 Mg−1 in Oregon, $98.76 Mg−1 in Idaho, and $179.07 Mg−1 in California. Land rental, establishment, crop care, harvest, transportation, and land restoration, respectively, accounted for 23%, 5%, 19%, 30%, 17%, and 6% of total feedstock cost. Farms were successfully restored to conditions existing before poplar conversion. In the absence of fertilization, increases in soil pH and decreases in nitrate-nitrogen, zinc, iron, and organic matter were consistently noted but could not be associated with poplar production alone.