Thermal conductivity of untreated and chemically treated poplar bark and wood

The thermal insulation properties of bark and wood of a poplar tree (Populus nigra × alba) were investigated using a guarded hot plate device (GHP) and a purpose-built miniature heat flow meter (Mini-HFM). To reduce their density and improve their performance as insulation material, bark and wood were chemically treated. The correlation between thermal conductivity and test temperature as well as between thermal conductivity and material moisture was investigated. By means of the treatment 44 and 34% of the mass of bark and wood, respectively, was removed and the equilibrium moisture content of the both materials decreased significantly. For untreated bark, a thermal conductivity of 0.071 Wm−1 K−1 and 0.140 Wm−1 K−1, respectively, were determined in transverse and axial direction. For wood, measurements showed comparably higher conductivities of 0.078 Wm−1 K−1 and 0.204 Wm−1 K−1 in transverse and axial direction. By reducing density, thermal conductivity of bark decreased up to 24%, whereas for wood reductions between 10 and 35% were found. It was shown that the self-constructed Mini-HFM is a useful and reliable instrument to determine the thermal conductivity on a small wood sample in the three main anatomical directions.

Establishment of Regional Phytoremediation Buffer Systems for Ecological Restoration in the Great Lakes Basin, USA. II. New Clones Show Exceptional Promise

Poplar tree improvement strategies are needed to enhance ecosystem services’ provisioning and achieve phytoremediation objectives. We evaluated the establishment potential of new poplar clones developed at the University of Minnesota Duluth, Natural Resources Research Institute (NRRI) from sixteen phytoremediation buffer systems (phyto buffers) (buffer groups: 2017 × 6; 2018 × 5; 2019 × 5) throughout the Lake Superior and Lake Michigan watersheds. We divided clones into Experimental (testing stage genotypes) and Common (commercial and/or research genotypes) clone groups and compared them with each other and each NRRI clone (NRRI group) at the phyto buffers. We tested for differences in clone groups, phyto buffers, and their interactions for survival, health, height, diameter, and volume from ages one to four years. First-year survival was 97.1%, with 95.5%, 96.2%, and 99.6% for the 2017, 2018, and 2019 buffer groups, respectively. All trees had optimal health. Fourth-year mean annual increment of 2017 buffer group trees ranged from 2.66 ± 0.18 to 3.65 ± 0.17 Mg ha−1 yr−1. NRRI clones ‘99038022’ and ‘9732-31’ exhibited exceptional survival and growth across eleven and ten phyto buffers, respectively, for all years. These approaches advance poplar tree improvement efforts throughout the region, continent, and world, with methods informing clonal selection for multiple end-uses, including phytotechnologies.

Analysis of Environmental Purification Effect of Riparian Forest with Poplar Trees for Ecological Watershed Management: A Case Study in the Floodplain of the Dam Reservoir in Korea

The Total Nitrogen(T-N) and Total Phosphors(T-P) contents in the soils of three riparian forests with poplar trees were compared with the surrounding cultivated and uncultivated lands. Three key results were obtained by analyzing poplar tree volume and the T-N and T-P content in the plant body. First, in soil surveys covering 36 points, the T-N and T-P content in the riparian forests were 0.064% and 0.036%, respectively, whereas in non-riparian forests, they were 0.147% and 0.101%, respectively. The two areas had significantly different T-N and T-P values. Within the non-riparian-forest category, the T-N and T-P content in cultivated land was 0.174% and 0.103%, respectively, showing significant differences from riparian forest values. When comparing riparian forests and uncultivated land, the T-N contents were not significantly different (p > 0.113), but the T-P content of 0.095% showed a significant difference (p < 0.006). Second, the total poplar tree volumes of the riparian forest test sites 1, 2, and 3 were 466.46 m3, 171.34 m3, and 75.76 m3, respectively. The T-N and T-P accumulation per unit area was the largest in site 1, at 497.75 kg/ha and 112.73 kg/ha, respectively. The larger the tree volume, the larger the T-N and T-P accumulation in the plant body, and the lower the T-N and T-P content in the soil. Third, analyzing the T-N and T-P removal rate in relation to the environmental conditions of the riparian forests showed that site 3 had the smallest total poplar tree content, and the T-N and T-P accumulation per unit area (ha) was also relatively low at just 56% and 68% of the average value. The main causes of this outcome are thought to be the differences in environmental conditions, such as the crop cultivated before poplar planting began and the terrain. The research results verify that riparian forests with poplar trees reduced T-N and T-P content in the soils. The growth of poplar is expected to increase the removal of T-N and T-P from the soil and contribute to the reduction of various nonpoint source pollution flows into rivers and lakes and to the purification of soil in flooded areas. Therefore, riparian forests can act as a form of green infrastructure and as a system to remove nonpoint source pollution in ecological watershed management.