Abstract Quantification of regional soil carbon changes in boreal forests in China is difficult for high spatial heterogeneity, especially considering soil CH4 fluxes in permafrost regions. This study attempted to quantify the variation of soil CO2 emission and its relationship with other soil properties along a permafrost hillslope in Larix gmelinii Kuzen. forest. Using a closed-chamber method, the soil CO2 emission was measured at four slope positions in the Greater Xing’an Range of China in two growing seasons. The results showed that soil CO2 changes have high spatial variability in Larix gmelinii forest along the slope, and average soil CO2 emission at the upper part of the slope was 64% higher than at the bottom. Soil CO2 fluxes showed high positive correlation with soil temperature at 10 cm depth and fungi numbers and negative correlation with soil CH4 change. This study showed the complexity of CO2 emission and could provide data support for forest carbon measurement caused by hillslope in the boreal forest of China.Study Implications: The forest area of Larix gmelinii Kuzen. in the Greater Xing’an Range accounts for 13.2% of the total forest area China. Therefore, the accurate calculation of carbon sequestration of Larix gmelinii forest is significant to the forest carbon measurement of China. However, due to the topographical complexity of the Greater Xing’an Range, the measurement of soil carbon has always been a problem. This study explored the soil carbon dioxide emissions at different slope positions along a hillslope and provided some methods and data support to solve measurement problems caused by hillslope in boreal forest in China.

Abstract There has been increasing interest among foresters and landowners in modifying existing even-aged forest structures to multi-aged or uneven-aged structures. Maintaining a continuous forest structure often provides a wider array of forest values over the long term. The conversion process is challenging in regions of the Northeast United States characterized by forests composed of dense diseased beech thickets and low-vigor deformed overstory trees. Abundance of noncommercial beech may result in negative cash flows during the conversion process to achieve a desired balanced uneven-aged structure. The Forest Vegetation Simulator was used to model growth and yield. Given the possibility of negative cash flows, a least-cost dynamic program with a penalty function was used to determine least-cost time paths for two management scenarios, one characterized by the successful removal of beech and the other simulating the continued presence of beech. Incorporating a penalty function allowed creating a continuum of least-cost paths from a zero penalty with the greatest weight given to net revenue goals to the largest penalty with the greatest weight given to ecological goals. Sensitivity analyses revealed least-cost paths were more stable given changes in prices and wages when greater emphasis was placed on the ecological goals associated with the target structure.

Abstract The black locust (Robinia pseudoacacia L.) is an economically and ecologically important tree worldwide. However, maturation and position effects affect its asexual reproduction. Despite etiolation treatment and successive subcultures promoting the plant cutting’s rooting rate, whether the promoting effects of aging (upper) branches and young (lower) branches are consistent is unknown. Therefore, we evaluated the relevant rooting ability indicators of tree age effect and its location effect in 26-year-old R. pseudoacacia trees and the current-year branches of different parts. Branches of the upper and lower parts of these trees underwent accelerated germination to generate shoots as explants. We subjected the tissue culture–generated shoots to an etiolation treatment to investigate how the treatment and subculture time affected the rooting ability of the shoot explants induced by different parts of the black locust branch. Tissue culture shoots subjected to the etiolation treatment exhibited a 2–3 day shorter rooting time. Shoots from the upper crown organs achieved a rejuvenation effect, which manifested as enhanced rooting capacity. Our study results provide a theoretical basis for maintaining the juvenility and consistency of clones. Besides having theoretical and practical value, our study also guides the selection of suitable propagation materials for production.

Abstract Forest residue utilization for energy has increased in the southeastern United States and additional increases are anticipated. However, such removals generate concerns regarding potential accelerated erosion and nutrient drains, which could affect site productivity and stream water quality. To address erosion and water quality concerns, postharvest erosion rates, operational feature areas, best management practice (BMP) implementation, residual ground cover, soil disturbance, and forest residue concentrations were evaluated on ten biomass and ten conventional clearcut harvests in Virginia’s Coastal Plain. No significant differences in erosion rates (P = 0.4727) were observed between biomass (0.71 tons ac-1 yr-1) and conventional (0.61 tons ac-1 yr-1) harvests. BMP compliance percentages were similar (P = 0.6776) for both biomass (88.54%) and conventional (90.99%) harvests. BMP implementation scores were determined to be a significant predictor of erosion rates (P < 0.0001). A significant reduction (28%) in postharvest residue concentrations was observed for biomass (10.22 tons ac-1) versus conventional harvests (14.24 tons ac-1) (P = 0.0173). Scores for BMP implementation and erosion rates were not significantly different between treatments, indicating that sufficient residual biomass exists for appropriate implementation of BMPs. BMPs provided similar erosion protection on both biomass and conventional clearcut harvests.Study Implications: Forest residues are widely used to cover and stabilize bare soil as best management practices (BMPs) for erosion control. The expanding bioenergy market has raised concerns that overutilization of forest residues may occur. Comparisons of biomass and conventional harvests in the Coastal Plain of Virginia revealed few significant postharvest differences. Implementation of existing water quality BMPs is important for minimizing erosion on biomass harvests; however, the development of biomass harvesting guidelines in addition to current state BMPs appears unnecessary under current harvesting practices. Harvest residue management should be conducted to ensure adequate supplies of woody debris remain for site protection.

Abstract Autotrophic (root) and heterotrophic respiration components respond differently to environmental variables, and each component behaves differently at different time scales, so it is necessary to partition total soil respiration into its components. The aims of this study were determine soil respiration and its root and heterotrophic components in beech stands, examine the relationship between respiration and biogeochemical factors, and assess seasonal variation in soil respiration. Trenching was applied to separate soil respiration components 6 months before measurements. Monthly soil respiration, temperature and moisture measurements, and seasonal soil and root sampling were carried out in Oriental beech (Fagus orientalis L.) stands located in Artvin Saçinka, Turkey from April 2018 to November 2018 and also (except soil sampling) from May 2019 to November 2019. The average contribution of root respiration and heterotrophic respiration to total soil respiration were 58.8% and 41.2%, respectively. Carbon and nitrogen dynamics explained variations of soil respiration with significant models. This study indicates that soil respiration and its components are associated with biogeochemical factors as well as environmental climatic conditions, and each component of respiration responds differently to changes in them.

Abstract Water quality best management practices (BMPs) developed for conventional forest harvests may be adequate for biomass harvests, yet quantitative data is lacking. This study compared estimated erosion, operational feature areas, BMP implementation rates, ground cover characteristics, and downed woody debris quantities following biomass and conventional harvests in the mountains of Virginia. Haul roads on biomass harvests had significantly higher estimated erosion rates (P = 0.064) and masses (P = 0.045) than conventional harvests, but conventional harvests had higher erosion contributions from skid trails (P = 0.089) and averaged more estimated erosion mass overall, despite being significantly smaller in size (P = 0.054). There was significantly less area in heavy slash (P = 0.076) and lower estimated mass of residual downed woody debris (P = 0.001) on biomass sites than conventional sites (10.98 and 27.95 tons/ac, respectively). Site-wide BMP implementation scores (P = 0.041), streamside management zones (SMZs) (P = 0.024), and skidding (P = 0.063) were significantly higher on biomass sites than conventional sites. BMP implementation scores were significant predictors of estimated erosion rates (P < 0.001, R2 = 59%), indicating that adequate levels of existing water quality BMPs are effective for erosion control on both conventional and biomass harvests.

Abstract The use of genomic markers in forest tree breeding is expected to improve the response to selection, especially within family. To evaluate the potential improvements from genotyping, we analyzed a large Pinus taeda L. clonal population (1,831 cloned individuals) tested in multiple environments. Of the total, 723 clones from five full-sib families were genotyped using 10,337 single-nucleotide polymorphism markers. Single-step models with genomic and pedigree-based relationships produced similar heritability estimates. Breeding value predictions were greatly improved with inclusion of genomic relationships, even when clonal replication was abundant. The improvement was limited to genotyped individuals and attributable to accounting for the Mendelian sampling effect. Reducing clonal replication by omitting data indicated that genotyping improved breeding values similar to clonal replication. Genomic selection predictive ability (masking phenotypes) was greater for stem straightness (0.68) than for growth traits (0.41 to 0.44). Predictive ability for a new full-sibling family was poorer than when full-sibling relationships were present between model training and validation sets. Species that are difficult to propagate clonally can use genotyping to improve within-family selection. Clonal testing combined with genotyping can produce breeding value accuracies adequate to graft selections directly into deployment orchards without progeny testing.

Abstract Calcium (Ca) is a critical plant nutrient typically applied at the time of planting in intensive Eucalyptus plantations in South America. At two sites in Colombia, we examined (1) calcium source by comparing growth after application of 100 kg ha−1 elemental Ca as lime or as pelletized highly reactive calcium fertilizer (HRCF) compared to a no application control, and (2) Ca rate by applying 0, 100, 200, and 400 kg ha−1 elemental Ca as HRCF with the addition of nitrogen, phosphorus, potassium, sulfur, and boron (NPKSB). We assessed height, diameter, and volume after 12 and 24 months. There were no growth differences from Ca source at the 100 kg ha−1 rate. We found increased volume after 24 months at the “Popayan” site with 200 and 400 kg ha−1 Ca HRCF+NPKSB treatments (112 and 113 m3 ha−1, respectively) compared to control (92 m3 ha−1), a 22% increase. In contrast, volume did not differ after 24 months at the “Darien” site, ranging from 114 m3 ha−1 in the 0 kg ha−1 Ca HRCF+NPKSB treatment to 98 m3 ha−1 in the control. Differences in response are likely due to soil characteristics, such as organic matter, emphasizing the importance of identifying site-specific nutrient deficiencies.

Abstract Generally, woody residues generated from logging remain on site, although recently, forest managers have been harvesting this material for energy generation. We evaluated the impact on an Oxisol’s physical and chemical properties after removal of residues (coarse woody debris, CWD) from logging-created gaps. The logging operations occurred on private timberland in the Central Amazon. Eighteen months after creation of the gaps, soil samples were taken up to 150 cm depth in each treatment: mature undisturbed forest (FOR), gaps with residues retained on site (RET), and gaps with removal of large branches greater than 10 cm in diameter that were from logging (REM). Clay content, up to 20 cm depth, was higher in RET and REM soils than in FOR soils. Soil bulk density values increased progressively from areas of FOR to RET and REM at 0–5 cm. The highest carbon and nutrient contents were observed in the 0–5 and 5–10 cm soil layers of RET. In the 10–30 cm depth, the contents of all nutrients, except phosphorus, were higher in REM soils. According to these short-term results, it is not possible to affirm categorically that the removal of CWD has a negative impact on the nutrient status of soils in gaps created by logging operations.

Abstract The jacaranda of Bahia (Dalbergia nigra (Vell.) Allemão ex Benth) is an endemic tree of a Brazilian neotropical biodiversity hotspot and is of great ecological and economic interest. Given the threat of extinction due to timber overexploitation and climate change, the present study aimed to analyze the physiological and biochemical quality of D. nigra seeds exposed to heat stress. The seeds were sown in a test tube containing woody plant culture medium, kept in a biochemical oxygen demand chamber at 45°C for 0, 24, 48, 72, and 96 hours, and then maintained in the same chamber at 25°C for 30 days. Physiological analyses of moisture, electrical conductivity, germination speed index, normal and abnormal seedlings, seedling length, root length, hypocotyl length, collar diameter, seedling and root dry mass, and Dickson quality index revealed a drop in germination and vigor with prolonged heat stress, dropping from 95% to 0% between 0 and 96 hours. This was accompanied by a reduction in the content of carbohydrates, lipids, and proteins. Therefore, the vigor and quality of seedlings is negatively influenced by exposure to heat stress at 45°C.