Search Results (202)

There is growing interest in the use of herbicide for the silvicultural practice of tree thinning (i.e., chemical thinning or e-thinning) in New Zealand. Potential benefits of this approach include improved stability of the standing crop in high winds, and safer and lower-cost operations, particularly in steep or remote terrain. As uptake grows, tools for monitoring treatment effectiveness, particularly during the early stages of stress, will become increasingly important. This study evaluated the use of UAV-based multispectral and hyperspectral imagery to detect early herbicide-induced stress in a nine-year-old radiata pine (Pinus radiata D. Don) plantation, based on temporal changes in crown spectral signatures following treatment with metsulfuron-methyl. A staggered-treatment design was used, in which herbicide was applied to a subset of trees in six blocks over several weeks. This staggered design allowed a single UAV acquisition to capture imagery of trees at varying stages of herbicide response, with treated trees ranging from 13 to 47 days after treatment (DAT). Visual canopy assessments were carried out to validate the onset of visible symptoms. Spectral changes either preceded or coincided with the development of significant visible canopy symptoms, which started at 25 DAT. Classification models developed using narrow band hyperspectral indices (NBHI) allowed robust discrimination of treated and non-treated trees as early as 13 DAT (F1 score = 0.73), with stronger results observed at 18 DAT (F1 score = 0.78). Models that used multispectral indices were able to classify treatments with a similar accuracy from 18 DAT (F1 score = 0.78). Across both sensors, pigment-sensitive indices, particularly variants of the Photochemical Reflectance Index, consistently featured among the top predictors at all time points. These findings address a key knowledge gap by demonstrating practical, remote sensing-based solutions for monitoring and characterising herbicide-induced stress in field-grown radiata pine. The 13-to-18 DAT early detection window provides an operational baseline and a target for future research seeking to refine UAV-based detection of chemical thinning. Full article

In forests dominated by deciduous tree species, coniferous species are often disproportionately important because of their contrasting functional traits. Eastern white pine (Pinus strobus L.), once a widespread emergent canopy species, co-occurs with deciduous hardwoods in the northern Lake States, but is often uncommon in contemporary hardwood stands. To gain insights into the potential utility of hardwood management strategies for simultaneously regenerating white pine, we leveraged a northern hardwood silvicultural experiment with scattered overstory pine. Seven growing seasons post-harvest, we conducted a complete census of white pine regeneration (height ≥ 30 cm) and mapped their locations and the locations of potential seed trees. Pine regeneration was sparse and strongly spatially aggregated, with most clusters falling within potential seed shadows of overstory pines. New recruits were found to have the highest density in a scarified portion of the study area leeward of potential seed trees. Low regeneration densities within treatment units, strong spatial aggregation, and the spatial arrangement of potential seed trees precluded generalizable inferences regarding the utility of specific treatment combinations. Nevertheless, our results underscore the critical importance of residual overstory pines as seed sources and highlight the challenges associated with realizing their potential in managed northern hardwoods. Full article

Oak–lime–hornbeam forests are among the most biodiverse temperate forests. This study compared older managed stands with a strictly protected old-growth forest in terms of their features. Managed forests at various stages of silvicultural operations were selected: a mature stand where regeneration cuts had not yet begun, as well as stands where such treatments were in the initial or advanced stages. Stand features that may affect the diversity and density of avifauna were analyzed on the basis of 151 sample plots. In four successive breeding seasons, birds in these stands were surveyed. The stands differed significantly in volume, the density of large trees, regeneration, the vertical structure, and the amount of deadwood. The number of bird species was the highest in the initial and advanced gap-cut stands. Group-selection cutting in those stands led to a succession of non-forest bird species and, hence, a greater number of birds building nests on or close to ground as compared to the old-growth forest. The old-growth forest was the most similar to the mature managed stand in terms of bird species composition (Jaccard index = 0.76). The old-growth forest was characterized by the highest bird density (91 pairs per 10 ha), with more than half of the breeding pairs being cavity nesters. In the managed forest, the bird density was from 63 to 72 pairs per 10 ha. Based on the present study, it can be concluded that effective conservation of bird assemblages is possible in managed forests, provided that certain concessions are made. Drawing on the characteristics of old-growth forests, several guidelines can be proposed for forest management. First and foremost, it is essential to maintain a mosaic forest structure. Secondly, it is necessary to retain an adequate number of large, old trees within the stand and to ensure a sufficient volume and diversity of deadwood. Additionally, it is absolutely critical to shift timber harvesting activities outside of the bird breeding season. Full article

Selection forestry sustains timber production and stand structural complexity via partial harvesting. However, regeneration initiated by harvesting may function as fuel ladders, providing pathways for fire to reach the forest canopy. We sought potential mitigation approaches by simulating stand growth and potential wildfire behavior over a century in stands dominated by coast redwood (Sequoia sempervirens (Lamb. ex. D. Don) Endl.) on California’s north coast. We used the fire and fuels extension to the forest vegetation simulator (FFE-FVS) to compare group selection (GS) to single-tree selection silviculture with either low-density (LD) or high-density (HD) retention on a 20-year harvest return interval. These three approaches were paired with six options involving vegetation management (i.e., hardwood control or pre-commercial thinning (PCT)) with and without fuels treatments (i.e., prescribed fire or pile burning), or no subsequent vegetation or fuel treatment applied after GS, HD, or LD silviculture. Fuel treatment involving prescribed fire reduced hazardous fuel loading but lowered stand density and hence productivity. Hardwood control followed by prescribed fire mitigated potential wildfire behavior and promoted dominance of merchantable conifers. PCT of small young trees regenerating after selection harvests, followed by piling and burning of these cut trees, sustained timber production while reducing potential wildfire behavior by approximately 40% relative to selection silviculture without vegetation/fuel management, which exhibited the worst potential wildfire behavior. Full article

Boreal forests have historically been regarded as some of the largest terrestrial carbon (C) sinks. However, increased soil organic matter (SOM) decomposition due to forest harvesting and post-harvest silviculture (e.g., site preparation, planting, and managing for competing vegetation) may exacerbate the effects of climate warming and shift boreal forests from being C sinks to C sources. We used an established stand-scale, fully replicated, experimental study to identify how two levels of forest management (harvesting = Harvest Only, and harvesting with post-harvest silviculture = Harvest Plus) influence SOC dynamics at three boreal forest sites varying in soil texture. Each site was surveyed for forest floor (litter and F/H horizons) and mineral soils pre-harvest (0) and 5, 14, and 20 years post-harvest. We predicted that sites harvested and left to revegetate naturally would have the lowest SOC stocks after 20 years, as sites that were planted and managed for competing vegetation would recover faster and contribute to a larger nutrient pool, and that the sand-dominated site would have the largest SOC losses following harvest due to the inherently lower ability of sand soils to chemically and/or physically protect SOC from decomposition following harvest. Over a 20-year period, both forest management treatments generally resulted in reduced total (litter, F/H, and mineral horizon) SOC stocks compared with the control: the Harvest Only treatment reduced overall SOC stocks by 15% at the silt-dominated site and 31% at the clay-dominated site but increased overall SOC stocks by 4% at the sand-dominated site, whereas the Harvest Plus treatment reduced overall SOC stocks by 32% at the sand- and silt-dominated sites and 5% at the clay-dominated site. This suggests that harvesting and leaving plots to revegetate naturally on sand-dominated sites and harvesting followed by post-harvest silviculture on clay-dominated sites may minimize total SOC losses at similar sites, though a full replicated field experiment is needed to test this hypothesis. Most treatment effects in this study were observed only in the second decade post-harvest (14 and 20 years post-harvest), highlighting the importance of long-term field experiments on the effects of forest harvesting and post-harvest silviculture. This research improves our understanding of the relationship between C dynamics, forest management, and soil texture, which is integral for developing sustainable management strategies that optimize C sequestration and contribute to the resilience of boreal forest ecosystems in the face of climate change. Full article

Ochroma lagopus Swartz is a rapidly growing plant known for its lightweight wood; it is widely utilized for timber production and ecological restoration. We investigated the effects of different numbers of drought–rehydration cycles on O. lagopus seedlings cultivated at the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences. The experiment comprised three treatments: normal watering (CK, 80–85% field capacity), one drought–rehydration cycle (D1, one rewatering), and three drought–rehydration cycles (D2, three rewaterings). We characterized the effects of these treatments on seedling growth, biomass allocation, non-structural carbohydrates (NSCs), malondialdehyde (MDA), catalase (CAT) activity, peroxidase (POD) activity, superoxide dismutase (SOD) activity, proline content, and soluble protein content. The number of drought–rehydration cycles had a significant effect on the growth characteristics and physiological and biochemical properties of leaves. As the number of drought–rehydration cycles increased, the height increased significantly (by 17.17% under D2). The leaf biomass ratio, soluble sugar content, and starch content decreased (15.05%, 15.79%, and 46.92% reductions under the D2 treatment); the stem biomass ratio and root biomass ratio increased; CAT activity increased and then decreased (it was highest at 343.67 mg·g⁻¹·min⁻¹ under D1); and the POD and SOD activities, the MDA content, the soluble protein content, and the soluble sugar/starch ratio increased significantly (395.42%, 461.82%, 74.72%, 191.07%, and 59.79% higher under D2). The plasticity of growth was much greater than that of physiological and biochemical traits. In summary, O. lagopus seedlings adapted to multiple drought–rehydration cycles by increasing the accumulation of soluble proteins (likely associated with osmotic protection), activating enzymes (POD and SOD), promoting the conversion of NSCs (increasing stored carbon consumption), and allocating more biomass to plant height growth than to diameter expansion. Under climate change scenarios with intensified drought frequency, elucidating the drought resistance mechanisms of O. lagopus is critical to silvicultural practices in tropical plantation. Full article

Constructed wetlands (CWs) attempt to simulate the physicochemical and biological processes that occur within a natural wetland and have been employed in recent decades for wastewater treatment. This work aims to review the use of CWs for domestic wastewater treatment in undeveloped or developing areas, including the amount of literature produced, the type of constructed wetland, the vegetation, the substrate, and the social benefits that have been achieved, through a qualitative methodology where different articles are collected from the Scopus and Web of Science databases after a strict revision by means of the PRISMA method (Preferred Reporting Items of Systematic Reviews and Meta-Analyses) and CASP (Critical Appraisal Skills Program). A total of 49 articles were selected, and co-occurrence and density maps were obtained; following this, three main themes and the five keywords with the highest correlation were identified. The literature analyzed in this work exposes different types of CWs where not only the hybrid, vertical, and horizontal flow systems stand out, but also the floating and aerated wetlands, which present high removal efficiencies. Additionally, new substrate materials, such as olote, palm shells, and coconut peat, and the ornamental plants usually used, such as Phragmites australis and Thypha latifolia, are discussed; however, new studies with vegetation that has been little studied but has a high potential to be implemented in areas with silvicultural characteristics stand out: Duranta repens, Pennisetum pedicellatum, and Pistia stratiotes. In conclusion, there is an advancement in the research of these systems, new configurations, substrates, and vegetation to treat domestic wastewater; in addition, these studies present an opportunity to continue studying the installation of CWs at the household level; however, compared to the other areas of application mentioned above, its implementation requires a greater challenge, since it requires a compact design and easy handling. Full article

Regenerating conifers after harvest through planting and postharvest broadcast application of herbicide is effective in ensuring the survival and growth of seedlings, but faces challenges in meeting broad social and ecological objectives of forest management. This study reports the effectiveness of alternative options in regenerating jack pine (Pinus banksiana Lamb.), 21 years after harvest of trembling aspen (Populus tremuloides Michx.)-dominated boreal mixedwood stands. The treatment options included (i) preharvest spray—aerial broadcast spray prior to harvest, (ii) postharvest partial spray—ground herbicide application in strips, (iii) partial harvest in strips, (iv) postharvest aerial broadcast, and (v) uncut reference. Twenty-one years after treatments, the four harvest treatments were similar in overstory density (4000 stems/ha) and basal area (BA, 20 m²/ha), but differed in composition and structure. The preharvest spray had an intimate mixture of aspen and jack pine (22% and 57% by BA, respectively), compared to spatial mosaics of aspen and pine corridors in the partial spray (36% and 41%), and aspen and maple corridors in the partial cut (21% and 31%). While the postharvest broadcast was pine-dominated (74% by BA) as expected, uncut and partial cut were similar in pine composition (10% by BA), which is inadequate for aspen and pine mixedwood stands. The early positive effects of preharvest spray and partial harvest on understory species abundance and diversity became neutral 21 years postharvest. The implications of these findings are discussed with respect to stand conditions before harvest, postharvest regeneration dynamics, and treatment objectives for the renewal of trembling aspen and jack pine mixedwood stands after harvest. Full article

The adoption of “consortium” of potential microorganisms can optimize the forest seedling production process. The objective of this study was to evaluate in greenhouse conditions the effect of co-inoculation between Trichoderma harzianum, Bradyrhizobium diazoefficiens, and B. elkanni on the growth of Schizolobium parahyba var. parahyba (Vell.) Blake seedlings. The treatments consisted of fungi strains (T. harzianum ESALQ 1306); bacteria strains (B. elkanni (SEMIA 5080) + B. diazoefficiens (SEMIA 587)); consortium (Trichoderma +Bradyrhizobium), and a control treatment. The seeds were sown, and evaluations were carried out 120 days after sowing. The variables analyzed were shoot height (SH), stem diameter (SD), root length (RL), shoot fresh mass (SFM), root fresh mass (RFM), total fresh biomass (TFM), shoot dry mass (SDM), root dry mass (RFM), total dry biomass (BIO), and Dickson quality index (DQI). The evaluated microorganisms proved to be effective in the production of S. parahyba var. parahyba, with emphasis on co-inoculation for growth parameters, promoting an increase in SH (23%), SD (36%), and RL (84%). For mass, non-inoculated seedlings (control) obtained a decrease of 67% (TFM) and 83% (BIO) compared to co-inoculation. The results indicate a promising method in seedling production; the biostimulators allowed the increase in plant development, which led to success in the morphometric indices. The mechanisms involved in the co-inoculation of microorganisms’ consortium in promoting the growth of native wood species to allow their production on a large scale in the silvicultural sector are still scarce, and new research is needed to elucidate the physiological and biochemical mechanisms involved. Full article

Haloxylon ammodendron plays a pivotal role in combating aeolian desertification and restoring degraded arid ecosystems. Strategic afforestation protocols for this xerophytic species offer dual benefits in ecological stabilization and socioeconomic development, particularly in ecotonal zones between desert and oasis ecosystems, as exemplified by the Jilantai Salt Lake region. This investigation employs allometric scaling analysis to elucidate biomass allocation strategies in H. ammodendron plantations under three distinct silvicultural approaches: soil moisture retention afforestation, water flushing afforestation, and mechanical hole afforestation. Key findings demonstrate that water flushing afforestation treatment induced significant biomass enhancement (total biomass: 1718.69 ± 214.28 g), with phylloclade (photosynthetic branch) and vegetative organ biomass increasing by 29.03% and 60.34%, respectively, compared to conventional methods. Conversely, soil moisture retention afforestation preferentially promoted lignification processes, maximizing biomass allocation to structural components (stems: 15.2% increase) and reproductive structures (inflorescences: 22.7% elevation). Standardized major axis regression revealed differential scaling exponents among organ pairs under varying treatments (stem-phylloclade: 1.798; inflorescence-phylloclade: 1.752; vegetative-reproductive: 1.672; p < 0.001), indicating treatment-specific allometric allocation patterns. Notably, soil moisture retention afforestation induced lateral crown expansion through enhanced meristematic activity in secondary branches (p < 0.01), contrasting with the apical dominance observed in water flushing afforestation and mechanical hole afforestation specimens. These morphological divergences suggest resource allocation trade-offs between vertical exploration and horizontal exploitation strategies. The differential growth trajectories were strongly correlated with edaphic moisture redistribution patterns (R² = 0.83, p < 0.001), as quantified using soil water potential measurements. This study provides mechanistic insights into phenotypic plasticity responses to silvicultural interventions. These findings advance our understanding of allometric growth regulation in a psammophyte and establish an empirical basis for optimizing desert afforestation strategies in arid transitional ecotones. Full article

Historical forestry practices (e.g., fire suppression, heavy timber logging) have contributed to a discernable change in stand composition of western forests in the U.S., which now comprise a tinderbox mixture of increased surface and ladder fuels, dense stands, and fire-intolerant species. Forest managers are mitigating this concern by implementing silviculture practices (e.g., selective logging, thinning, prescribed burning) to reduce fuel loads and improve stand resiliency. Concern for habitat specialists, such as the fisher (Pekania pennanti), have arisen as they may be negatively influenced in the short-term by modifications to their environment that are needed to ensure long-term habitat persistence. To address this issue, we initiated an 8-year study in 2010 in Ashland, Oregon, to determine the behavioral response of fishers to fuel reduction treatments applied in forested stands. We measured the distance of each location from eight GPS-collared fishers to all treatments before and after they were treated within each home range, and performed three statistical tests for robustness, including a multi-response permutation procedure, chi-squared test of independence, and a Kolmogorov–Smirnov assessment. We found high variation among individuals to the tolerance of habitat manipulation. Using effect size to interpret the magnitude of fisher response to pre- and post-treatment effects, 1 fisher showed a moderate negative relationship to fuel reduction treatments, 5 exhibited a weak negative response, and 2 had a weak positive association with treatments. We used analysis of variance on the three fishers exhibiting the largest effect sizes to treatment disturbance, and used treatment, temporal, and habitat covariates to explore whether these factors influenced behavioral differences. Treatment season and vegetation class were important factors influencing response distance in the pre-treatment period. Post-treatment variables eliciting a negative treatment response were treatment season and treatment size, and results were slightly different when parsing out individual effects compared to a pooled sample set. Our findings suggested that seasonal timing and the location of management activities could influence fisher movement throughout their home range, but it was largely context-dependent based on the perceived risks or benefits to individuals. Full article

As forest managers increasingly seek to develop and maintain mixedwood forests, more information is required on the potential facilitative and competitive interactions between tree species. We present data from a broadleaf thinning study established in a mixedwood stand in Central British Columbia, Canada, to examine how residual trembling aspen and paper birch competitively affect spruce growth after thinning but may also concurrently protect spruce from attack by the white pine weevil. Tree-level data collected at a stand age of 36 years, 19 years after broadleaf trees were thinned, show that spruce height and diameter growth declined with broadleaf competition, particularly from taller trees, resulting in a competition-related reduction in stand-level spruce volume yields. The fastest spruce growth occurred in treatments where all broadleaf trees were removed, but complete broadleaf removal also resulted in higher rates of weevil attack on spruce, which also caused height and diameter growth reductions. Our results suggest that maintaining a density of approximately 500 broadleaf trees per hectare may achieve a stand condition that balances spruce growth reductions from competitive interactions with broadleaf trees while providing some protection from white pine weevil attacks. Full article

The success of reforestation and restoration projects depends on several factors, with proper seedling management and the selection of an appropriate planting area being crucial. In Peru, the populations of Retrophyllum rospigliosii (Pilg.) C.N.Page (Ulcumano) have been decreasing due to intensive logging of one of the most valuable woods in South America’s tropical forests. There are few studies that unify the production of plants through seeds in nurseries and the identification of suitable areas to place the plants produced. Our study has two components. The first aimed to optimize the plant production process through an experiment that evaluated the effects of three doses of controlled-release fertilizer (CRF) (4.2, 8.4, and 12.6 g/L) and two container sizes (115 and 180 cc) on the morphological quality of seedlings in the nursery. The second component involved identifying potential reforestation areas using ecological niche modeling, based on climatic and edaphic variables. The results indicated that the 4.2 g/L CRF treatment for both container sizes had a significant positive effect on seedling growth. The average germination rate was 85% at 120 days. At six months after seedling transplantation, treatments of 4.2 g/L CRF in 115 cc and 180 cc containers were shown to have the best positive effect on morphological variables of seedlings, with a root collar diameter of 3.76 mm and a height of 13.25 cm. Regarding the potential niche models, an area of 6321.97 km² with ideal conditions for reforestation with R. rospigliosii was estimated, with the departments of Huánuco, Pasco, Junín, and Cusco showing the highest potential. Based on this, it is estimated that over three million plants are needed for large-scale reforestation projects. Integrating silvicultural studies with niche models is a valuable tool for supporting reforestation and ecosystem restoration projects. Full article

Forest restoration thinning may accelerate the development of structural complexity toward old-growth conditions faster than a natural forest, yet associated changes in forest carbon (C) are poorly understood. Old-growth forests are characterized by high levels of sequestered C in aboveground biomass and soil C pools, yet active management has well-recognized negative impacts on stored C. Effects of forest restoration thinning on forest C can be determined using longitudinal measurements and modeling based on stand conditions and tree growth. At Ellsworth Creek Preserve in Southwest Washington, forest restoration efforts in a second-growth temperate rainforest have been monitored using permanent plots since 2007. Here, we compare repeat measurements from 2020, modeled forest C, and measurements of O-horizon C pools from 2022 to determine C impacts of silvicultural treatments for old-growth restoration. We found good general agreement between empirical measurements and models of forest C using the Forest Vegetation Simulator (FVS). However, treatment alone was not a strong indicator for C conditions; rather, forest age and age–treatment interactions better predicted soil C responses to restoration treatments. These data may indicate that “light” forest restoration thinning can accelerate old-growth development with minimal effects on soil carbon—a win-win conservation strategy for old-growth forests and the climate. Full article

A comprehension of the effects planting density and nitrogen (N) fertilization have on the physiological and morphological characteristics of trees is critical for optimizing the require size and characteristics of wood products. We evaluated the growth traits and the leaf and wood characteristics of three clone poplars including Populus simonii × P. nigra ‘Xiaohei’, ‘Xiaohei-14’ and ‘Bailin-3’ under five planting densities (1666, 1111, 833, 666, and 555 tree ha⁻¹) and four N fertilization rates (0, 100, 160, and 220 g tree⁻¹ year⁻¹). The results show that the clone type significantly affected all observed indicators, while planting density and N fertilization treatments had a significant effect on growth traits and leaf characteristics, but not on wood characteristics. Specifically, the clone ‘Bailin-3’ exhibited the largest annual increments in tree height and diameter at breast height (DBH), leaf width, N content, and soluble protein content. A decrease in initial planting density (from 1666 to 555 tree ha⁻¹) led to an increased annual incremental tree height and DBH, regardless of clone type and N fertilization treatment. N fertilization treatment significantly impacted the annual increment in DBH, but not that of tree height. Further, the annual increments in tree height and DBH were positively correlated with leaf width, N content, chlorophyll content, and soluble protein content, and negatively correlated with hemicellulose content. In addition, the chlorophyll and soluble protein contents were identified as the most reliable predictors of the annual increments in tree height and DBH. Our results demonstrate the clone ‘Bailin-3’ with 555 tree ha⁻¹ under 160 g N tree⁻¹ yr⁻¹ showed superior growth traits and leaf characteristics. Thus, it is recommended for future poplar silviculture of larger diameter timber production at similar sites. The results contribute to understanding of the effects of planting density and fertilization on the growth traits and the leaf and wood characteristics of three poplar clones, offering valuable guidance for the sustainable development and long-term productivity of poplar plantations. Full article