Partial Harvesting Research Articles

Optimal harvesting of a predator-prey system with marine reserve

Fisheries in developing countries are often confronted with the problem of excessive harvesting of the marine resources as a result of lax management practices. This study formulates an optimal control problem involving a predator-prey model with partial harvesting of the prey species and a critical biomass level below which the fishery is not economically viable. The region of boundedness and the equilibrium points of the system are determined and discussed. Stability analysis of the model shows that the interior equilibrium point is both locally and globally asymptotically stable. The Bendixson–Dulac criterion establishes that the system does not possess any limit cycles or periodic orbits. Pontryagin’s maximum principle is employed to determine the necessary conditions for optimality of the model. Singularity analysis of the model, with the aid of the generalized Legendre–Clebsch condition, indicates that the existence of singular arcs cannot be ruled out. Therefore, the characterization of the optimal control gives rise to both bang-bang and singular controls. Furthermore, the relationship between the shadow price of fish stock, the shadow price of fishing effort and the price of landed fish as it relates to the optimal reserve area is explored. Numerical simulations are performed to validate the established theoretical results using empirical data on the Ghana sardinella fishery. The study reveals that the fishery can sustain an effort rate of more than twice the maximum sustainable (MSY) rate, provided that 40% of the current fish stock is in a marine reserve and the operational fish population is at least 30% of the carrying capacity of the ecosystem.

Stand Characteristics and Perceptions of Local Communities on the Management of Pistachio (Pistacia vera L.) Forests in an Unstable Region of Afghanistan

ABSTRACT Pistachio (Pistacia vera L.) forests support livelihoods in communities within Afghanistan’s Pistachio Belt, a region characterized by extreme poverty and chronic insecurity. In this study, we used ecological data, as well as survey data to characterize standing attributes and resource user perceptions about local pistachio forests and their management. The survey questionnaire was verbally administered to 507 household representatives in remote communities that were chosen from eight districts in northern and northwestern Afghanistan based on accessibility and their location within the Pistachio Belt. Stand density and tree form varied widely between sites and as a function of elevation. Partial harvesting for fuelwood collection was positively correlated with stand density. The survey data also showed that pistachio forests support a variety of livelihood activities among respondents and their households. However, suboptimal nut collection timing and use of damaging nut harvesting methods were widespread with little effort to accommodate natural regeneration. Forest users typically recognized the degraded condition of the pistachio forest and the negative impacts of grazing and fuelwood collection on forest density. Respondents also recognized the impacts of nut collection practices, fuelwood collection, and grazing on forest regeneration status. These results suggest that efforts to sustainably manage pistachio forests must recognize considerable variation within and between communities regarding forest physical condition, accustomed uses by associated communities, and existing or potential mechanisms regulating forest uses. All of these necessitate context-specific forest management planning. We discuss challenges inherent to collecting baseline data needed for planning multiple-use community-based natural resources management in highly insecure environments.

Economic impacts of partial harvesting: Mitigating mid-term timber supply shortages as a result of pest outbreaks

Natural disturbances such as pest outbreaks have a significant impact on forest dynamics and services, including the loss of mature stands. From a wood production perspective, these disturbances can lead to long-lasting imbalances in the overall age-class structure of the forest, potentially resulting in a shortage of mature harvestable stands. Researchers from Natural Resources Canada’s (NRCan) Canadian Forest Service (CFS) have made a timber supply analysis of the Dunière forest located in the centre of the Gaspé Peninsula (Québec). This region suffers from an age-class structure imbalance caused by an eastern spruce budworm (ESB) outbreak that ended in 1984, and is consequently facing a reduced annual allowable cut, leading to long- term implications for the regional forest sector. The authors suggest that partial harvesting – the removal of a proportion of timber in a mature stand several years before a final cut is carried out – is a promising opportunity in the ESB-affected area for mitigating mid-term timber supply shortages by smoothing the fibre supply over time.

The effect of partial harvest on production and growth performance of Litopenaeus vannamei reared in biofloc technologic system

The purpose of this study was to evaluate the effect of partial harvest management on Litopenaeus vannamei reared in BFT system. The experiment lasted for 154 days and it was divided in four experimental treatments according to the number of partial harvests. Treatment H0 had no partial harvest, H1 had one partial harvest (50% of total biomass), H2 had two partial harvests (33% of total biomass each), and H4 that had four partial harvests (20% of total biomass each). The shrimps were kept at optimal water quality conditions and were feed three times a day with commercial feed. The results of production parameters such as final weight 16.1 g (H0), 18.9 g (H1), 18.5 g (H2) and 20.1 g (H4), survival 43.67% (H0), 82.7% (H1), 86.6% (H2) and 84.7% (H4), and yield 3.48 kg.m−2 (H0), 5.85 Kg.m−2 (H1), 6.22 kg.m−2 (H2) and 6.14 kg.m−2 (H4) demonstrate significant differences among treatments. These results suggest that the partial harvest management in BFT system can leverage productivity.

P-461 Pre-selected for an award: A 16-year bicentric retrospective analysis of ovarian tissue cryopreservation (OTC) in paediatric patients: indications, results and outcome

Abstract Study question What is the outcome of ovarian tissue cryopreservation (OTC) in paediatric patients from the beginning of its setting in two different French centres? Summary answer In our cohort of 75 paediatric patients who underwent OTC, the mean age, malignancy rate and survival rate were 9.7 years, 70.7% and 77.3% respectively. What is known already Cancer treatments of last decades improve the survival rate of children and adolescents; however chemo- and radiotherapy result in gonadal damage leading to acute ovarian failure and sterility. The preservation of fertility is now an integral part of care of children requiring gonadotoxic treatments. Currently OTC represents the only possibility of preserving the potential fertility in prepubertal girls. OTC is an effective fertility preservation option which allows long-term storage of primordial follicles, subsequent transplantation restores endocrine function and fertility. The efficacy of these techniques is well-demonstrated within adult population but the data are poor for paediatric patients. Study design, size, duration This is a retrospective study of OTC practice of two French centres from January 2004 to May 2020. Participants/materials, setting, methods A total of 75 patients from paediatrics units underwent cryopreservation of ovarian tissue before gonadotoxic therapy for malignant or benign diseases. The ovarian cortex was cut into fragments and the number of follicles per square millimeter was evaluated histologically. The long-term follow-up includes survival rate, hormonal and fertility status. Main results and the role of chance The mean age at OTC of 75 patients was 9.7 years [0.2 – 20], 32% were postpubertal. 53 had malignant disease and 22 had non-malignant disease. The most frequent diagnoses in this cohort included acute leukemia, hemoglobinopathies and neuroblastoma. Indication for OTC was stem cell transplantation for 78.7% (n = 59) girls. A third of each ovary was collected for 62,7% (n = 47) patients, a whole ovary for 33,3% (n = 25) patients and a third of one ovary alone for 4,0% (n = 3) patients. An average of 17 fragments [5-35] per patient was cryoconserved. A correlation was found between age and the number of fragments (p < 0.001). More fragments were obtained from partial bilateral harvesting than from whole ovary harvesting (p < 0.05). Histological analysis of ovarian tissue showed a median of 6.0 primordial follicles/mm2 [0.0–106.5] and no malignant cells were identified. A negative correlation was found between age and follicular density (p < 0.001). Median post-harvest follow-up was 92 months [1–188] 17 girls had died, 12 were still treated for their pathology and 46 were in complete remission. Of all patients, 29 have been subject to hormonal status evaluation and 26 were diagnosed with premature ovarian insufficiency (p < 0.001). One patient had undergone thawed ovarian tissue transplantation. Limitations, reasons for caution This study is a retrospective analysis. The cohort was not compared with a control group who did not undergo OTC or with an adult population. Furthermore, many of these girls are still young and do not intend to use the transplantation of thawed ovarian tissue yet. Wider implications of the findings OTC should be proposed to all girls with high risk of developing premature ovarian insufficiency following gonadotoxic therapies in order to give them the possibility of fertility and endocrine restoration. Trial registration number Not applicable

P–461 A 16-year bicentric retrospective analysis of ovarian tissue cryopreservation (OTC) in paediatric patients: indications, results and outcome

Abstract Study question What is the outcome of ovarian tissue cryopreservation (OTC) in paediatric patients from the beginning of its setting in two different French centres? Summary answer In our cohort of 75 paediatric patients who underwent OTC, the mean age, malignancy rate and survival rate were 9.7 years, 70.7% and 77.3% respectively. What is known already Cancer treatments of last decades improve the survival rate of children and adolescents; however chemo- and radiotherapy result in gonadal damage leading to acute ovarian failure and sterility. The preservation of fertility is now an integral part of care of children requiring gonadotoxic treatments. Currently OTC represents the only possibility of preserving the potential fertility in prepubertal girls. OTC is an effective fertility preservation option which allows long-term storage of primordial follicles, subsequent transplantation restores endocrine function and fertility. The efficacy of these techniques is well-demonstrated within adult population but the data are poor for paediatric patients. Study design, size, duration This is a retrospective study of OTC practice of two French centres from January 2004 to May 2020. Participants/materials, setting, methods A total of 75 patients from paediatrics units underwent cryopreservation of ovarian tissue before gonadotoxic therapy for malignant or benign diseases. The ovarian cortex was cut into fragments and the number of follicles per square millimeter was evaluated histologically. The long-term follow-up includes survival rate, hormonal and fertility status. Main results and the role of chance The mean age at OTC of 75 patients was 9.7 years [0.2 – 20], 32% were postpubertal. 53 had malignant disease and 22 had non-malignant disease. The most frequent diagnoses in this cohort included acute leukemia, hemoglobinopathies and neuroblastoma. Indication for OTC was stem cell transplantation for 78.7% (n = 59) girls. A third of each ovary was collected for 62,7% (n = 47) patients, a whole ovary for 33,3% (n = 25) patients and a third of one ovary alone for 4,0% (n = 3) patients. An average of 17 fragments [5–35] per patient was cryoconserved. A correlation was found between age and the number of fragments (p < 0.001). More fragments were obtained from partial bilateral harvesting than from whole ovary harvesting (p < 0.05). Histological analysis of ovarian tissue showed a median of 6.0 primordial follicles/mm2 [0.0–106.5] and no malignant cells were identified. A negative correlation was found between age and follicular density (p < 0.001). Median post-harvest follow-up was 92 months [1–188]: 17 girls had died, 12 were still treated for their pathology and 46 were in complete remission. Of all patients, 29 have been subject to hormonal status evaluation and 26 were diagnosed with premature ovarian insufficiency (p < 0.001). One patient had undergone thawed ovarian tissue transplantation. Limitations, reasons for caution This study is a retrospective analysis. The cohort was not compared with a control group who did not undergo OTC or with an adult population. Furthermore, many of these girls are still young and do not intend to use the transplantation of thawed ovarian tissue yet. Wider implications of the findings: OTC should be proposed to all girls with high risk of developing premature ovarian insufficiency following gonadotoxic therapies in order to give them the possibility of fertility and endocrine restoration. Trial registration number Not applicable

Blue consequences of the green bioeconomy: Clear‐cutting intensifies the harmful impacts of land drainage on stream invertebrate biodiversity

Abstract Growing bioeconomy is increasing the pressure to clear‐cut drained peatland forests. Yet, the cumulative effects of peatland drainage and clear‐cutting on the biodiversity of recipient freshwater ecosystems are largely unknown. We studied the isolated and combined effects of peatland drainage and clear‐cutting on stream macroinvertebrate communities. We further explored whether the impact of these forestry‐driven catchment alterations to benthic invertebrates is related to stream size. We quantified the impact on invertebrate biodiversity by comparing communities in forestry‐impacted streams to expected communities modelled with a multi‐taxon niche model. The impact of clear‐cutting of drained peatland forests exceeded the sum of the independent effects of drainage and clear‐cutting, indicating a synergistic interaction between the two disturbances in small streams. Peatland drainage reduced benthic biodiversity in both small and large streams, whereas clear‐cutting did the same only in small streams. Small headwater streams were more sensitive to forestry impacts than the larger downstream sites. We found 11 taxa (out of 25 modelled) to respond to forestry disturbances. These taxa were mainly different from those previously reported as sensitive to forestry‐driven alterations, indicating the context dependence of taxonomic responses to forestry. In contrast, most of the functional traits previously identified as responsive to agricultural sedimentation also responded to forestry pressures. In particular, taxa that live temporarily in hyporheic habitats, move by crawling, disperse actively in water, live longer than 1 year, use eggs as resistance form and obtain their food by scraping became less abundant than expected, particularly in streams impacted by both drainage and clear‐cutting. Synthesis and applications. Drained peatland forests in boreal areas are reaching maturity and will soon be harvested. Clear‐cutting of these forests incurs multiple environmental hazards but previous studies have focused on terrestrial ecosystems. Our results show that the combined impacts of peatland drainage and clear‐cutting may extend across ecosystem boundaries and cause significant biodiversity loss in recipient freshwater ecosystems. This information supports a paradigm shift in boreal forest management, whereby continuous‐cover forestry based on partial harvest may provide the most sustainable approach to peatland forestry.

Stand-level forest management for foraging and nesting of Williamson’s sapsuckers

Williamson’s Sapsuckers, like most woodpeckers, require live and dead standing trees for foraging and nesting. Forest management plans that include Williamson’s Sapsucker habitat conservation guidelines currently focus on nesting trees because little is known about foraging habitat requirements, but foraging habitat in close proximity is also essential for the survival and reproduction of the species. We conducted a study on the selection of stand-level characteristics for foraging and nesting territories to improve knowledge on the habitat requirements of this endangered woodpecker in Canada during the breeding season. We tracked 27 radio-tagged Williamson’s Sapsuckers in managed forest at their northern range limit in two regions of southern British Columbia. We examined the selection of forest composition and configuration characteristics at the foraging patch and stand levels by comparing use and availability, and described foraging trip distances. In the Okanagan region, sapsuckers did not show a selection pattern for foraging patch characteristics. In the Western region, Williamson’s Sapsuckers selected foraging patches with higher densities of large live Douglas-fir trees. Nest patches were usually in small openings and had lower tree densities than foraging patches in the Western region, but not in the Okanagan region. Open areas (e.g., clear-cuts, seed tree cuts, pastures, roads, powerlines) were avoided during foraging trips in both regions. Regarding stand-level configuration, Williamson’s Sapsuckers selected continuous stands for foraging – with ≥30% crown closure in both regions. We used the 50th and 95th percentiles of foraging trip distances to recommend zones for nest reserve (no-harvest; 0–140 m from the nest) and nest management (Okanagan: 340 m, Western: 410 m). For the nest management zone, we recommend only partial harvesting with retained groups of trees extending from 140 to 340 m in the Okanagan region and from 140 to 410 m in the Western region. We suggest that Williamson’s Sapsuckers exhibited stronger selection when foraging in the Western region, because they compensated for longer foraging distances due to higher proportions of open area in their nesting territories.

Managing Wildlife Habitat: Complex Interactions With Biotic and Abiotic Disturbances

Sustainable forest management strategies include emulating historical disturbance regimes to achieve multiple objectives. Partial-harvesting strategies are used to overcome conflicts between timber production and wildlife habitat conservation; however, the potential impacts on complex disturbance interactions and ecological functions remain largely unknown. In 1984, a controlled experiment was initiated in the dry forests of central British Columbia, Canada, to test partial harvesting intended to enhance mule deer habitat while allowing timber extraction. To determine the short- and long-term impacts on complex disturbance regimes, we quantified changes in forest structure and susceptibility to western spruce budworm, Douglas-fir beetle, and wildfire. We compared structural attributes in 2014 (30 years after the first harvest) and 2015 (1 year after the second harvest) in treated forests, and contrasted them with control forests that were measured in 2015. In the short term (1 year post-harvest), partial harvesting altered forest structure by reducing total canopy cover, subcanopy tree density and basal area, and increasing the abundance of large woody surface fuels. In the long term (30 years post-harvest), the forest canopy attributes did not differ between the treatment and control areas, partly due to increased growth of subcanopy trees. Harvesting had little impact on forest susceptibility to western spruce budworm. Susceptibility to Douglas-fir beetle was lower in the short term due to fewer available mature host trees, but increased to levels similar to the control forest over the long term. Reduced canopy fuels and increased canopy base height decreased the likelihood of crown fire in favor of surface fire. In the long term, canopy fuels and likelihood of crown fire recovered, but woody fuel loads remained low after 30 years. Harvesting to enhance mule deer habitat interacts with biotic and abiotic disturbances in the short and long term. Potential cascading affects depended more on the decision to remove harvesting residuals to mitigate potential Douglas-fir beetle infestations and wildfire than on time since treatment. Provided partial harvesting occurs at intervals ≤ 30 years and residuals are immediately removed, timber extraction and mule deer habitat can be compatible with complex disturbance regimes and sustainable forest management.

Tung Oil-Based Production of High 3-Hydroxyhexanoate-Containing Terpolymer Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate-co-3-Hydroxyhexanoate) Using Engineered Ralstonia eutropha.

Polyhydroxyalkanoates (PHAs) are attractive new bioplastics for the replacement of plastics derived from fossil fuels. With their biodegradable properties, they have also recently been applied to the medical field. As poly(3-hydroxybutyrate) produced by wild-type Ralstonia eutropha has limitations with regard to its physical properties, it is advantageous to synthesize co- or terpolymers with medium-chain-length monomers. In this study, tung oil, which has antioxidant activity due to its 80% α-eleostearic acid content, was used as a carbon source and terpolymer P(53 mol% 3-hydroxybytyrate-co-2 mol% 3-hydroxyvalerate-co-45 mol% 3-hydroxyhexanoate) with a high proportion of 3-hydroxyhexanoate was produced in R. eutropha Re2133/pCB81. To avail the benefits of α-eleostearic acid in the tung oil-based medium, we performed partial harvesting of PHA by using a mild water wash to recover PHA and residual tung oil on the PHA film. This resulted in a film coated with residual tung oil, showing antioxidant activity. Here, we report the first application of tung oil as a substrate for PHA production, introducing a high proportion of hydroxyhexanoate monomer into the terpolymer. Additionally, the residual tung oil was used as an antioxidant coating, resulting in the production of bioactive PHA, expanding the applicability to the medical field.

Post-harvest forest herb layer demography: General patterns are driven by pre-disturbance conditions

Timber harvesting constitutes extensive anthropogenic disturbance in temperate forests, producing a broad range of ecological impacts that most often enhance the demographic processes of vegetation. This study monitored post-harvest herb layer demography over a 6-year period in mesic Dinaric fir-beech forests (Slovenia), a vascular plant diversity hotspot among European forests. Three experimental harvesting intensities, i.e. full harvest (FH), partial harvest (PH) and a control treatment (NH), were each applied over a circular area of 4000 m2 and replicated three times at each of three study sites. Vegetation sampling was conducted before harvesting (in 2012), and two (2014) and six (2018) years following it, in a 400 m2 circular plot positioned in the centre of each treatment area. We focused on identifying general demographic patterns and evaluating the effects of various pre-disturbance abiotic and biotic predictors on compositional responses to disturbance. Two years after harvest (2012–2014), compositional shifts were larger than those in the next 4-year period (2014–2018), confirming the general theoretical prediction that species turnover rate decreases along a successional gradient. The degree of compositional shifts in gaps (FH) and thinned stands (PH) was affected by local abiotic factors (geomorphology of karst sinkholes) and community attributes, such as pre-harvest species richness. Our results indicate that compositional stability is positively associated with pre-disturbance species richness. Over the whole study period, increases in plot-level species richness (alpha diversity) and overall enrichment of the species pool (gamma diversity) were accompanied by compositional convergence, i.e. a decline in floristic dissimilarity (beta diversity) between and within study sites. However, the observed tendency towards homogenization was rather weak and would have been even more pronounced if the demographic type of persistent resident species had not shown a high degree of resistance, thus leaving a strong imprint on post-harvest vegetation development by preserving the forest characteristics of the herb layer community.

Evaluating partial harvesting strategies for whiteleg shrimp Litopenaeus (Penaeus) vannamei semi-intensive commercial production: profitability, uncertainty, and economic risk

A bioeconomic model and Monte Carlo simulation were used to analyze alternative management scenarios of partial harvesting schedules in semi-intensive shrimp (Litopenaeus vannamei) farming, emphasizing profitability, uncertainty, and economic risk. The schedules, including 1, 2, and 3 partial harvests, were studied considering two management scenarios (worst and best). Management improved by using high stocking density and reducing the rearing period. Higher profitability was calculated for Schedule 3 (US$ 6699 ha-1) in the best scenario, while Schedule 1 yielded the worst result even under the best scenario (US$ 2451 ha-1). Uncertainty diminished as management improved, as indicated by lower relative variability of the economic indicators. Higher uncertainty was expected for Schedule 1, while similar uncertainty was estimated for schedules 2 and 3. The highest economic risk was estimated for Schedule 1 in the worst scenario where a single pond would have a 27.9% probability of having economic losses. No losses were expected when using the best scenario for Schedule 3. Calculating the effect of averaging the results of 20 ponds rather than only one pond reduced uncertainty (from 76.9–78.4%) and loss probability (98.5%) in Schedule 1. Null loss probability was calculated for 20 ponds in the rest of the schedules. A sensitivity analysis indicated that the main factors affecting net revenues were final shrimp weight, shrimp prices of large shrimp, mortality rate before the first partial harvest, and rate at which the feed conversion ratio increased throughout the rearing period.

Restoration Thinning in a Drought‐Prone Idaho Forest Creates a Persistent Carbon Deficit

AbstractWestern US forests represent a carbon sink that contributes to meeting regional and global greenhouse gas targets. Forest thinning is being implemented as a strategy for reducing forest vulnerability to disturbance, including mortality from fire, insects, and drought, as well as protecting human communities. However, the terrestrial carbon balance impacts of thinning remain uncertain across regions, spatiotemporal scales, and treatment types. Continuous and in situ long‐term measurements of partial harvest impacts to stand‐scale carbon and water cycle dynamics are nonetheless rare. Here, we examine post‐thinning carbon and water flux impacts in a young ponderosa pine forest in Northern Idaho. We examine in situ stock and flux impacts during the 3 years after treatment as well as simulate the forest sector carbon balance through 2050, including on and off‐site net emissions. During the observation period, increases in tree‐scale net primary production (NPP) and water use persistence through summer drought did not overcome the impacts of density reduction, leading to 45% annual reductions of NPP. Growth duration remained constrained by summer drought in control and thinned stands. Ecosystem model and life cycle assessment estimates demonstrated a net forest sector carbon deficit relative to control stands of 27.0 Mg C ha−1 in 2050 due to emissions from dead biomass pools despite increases to net ecosystem production. Our results demonstrate dynamics resulting in carbon losses from forest thinning, providing a baseline with which to inform landscape‐scale modeling and assess tradeoffs between harvest losses and potential gains from management practices.

Partial Harvest in Paludified Black Spruce Stand: Short-Term Effects on Water Table and Variation in Stem Diameter

The boreal forest is considered to be a low productivity forest due to its cold climate and poorly drained soils promoting paludification. These factors create conditions favouring accumulation of undecomposed organic matter, which causes declining growth rates of forest stands, ultimately converting mature stands into peatlands. Under these conditions, careful logging is conducted during winter, which minimizes soil disturbance in northwestern Quebec boreal forest. This results in water table rise, increased light availability and paludification. Our main objective was to evaluate the short-term effect of partial harvesting as an alternative method to careful logging in winter to mitigate water table rise on black spruce (Picea mariana [Mill.] B.S.P.) stands. We quantified tree stem diameter variation and daily variation in water table depth in mature spruce stands before and after partial harvest (basal area reduction of 40%) and girdling (same basal area reduction with delayed mortality) during 2016 and 2017 growing seasons. Water table variation prior to and following silvicultural treatments did not differ one year after treatment. Daily stem diameter variation in black spruce did not differ between treatments and control. Furthermore, temperature exerted a positive effect on variation in water table and on stem diameter. These results suggest that partial harvest could be more effective than clearcutting to mitigate negative effects of a high water table while limiting paludification.

Macrocystis (Laminariales, Phaeophyceae) in South Africa: potential for cultivation through holdfast fragmentation and use as feed for the aquacultured abalone, Haliotis midae

Macrocystis pyrifera (Linnaeus) C. Agardh, known in some regions as ‘giant kelp’, occurs along temperate coastal rocky reefs throughout the southern hemisphere, as well as along the north-east Pacific coastline. In Chile, it serves as a major source of abalone feed within the abalone industry, with considerable literature on cultivation of the species. Here we attempt to cultivate South African M. pyrifera through vegetative propagation and investigate its use as a feed for the abalone, Haliotis midae. Kelp holdfasts were attached to a rope-raft system in Saldanha Bay, South Africa, and monitored over 3 months. In addition, a 6-month H. midae feed inclusion trial was carried out, which compared the use of M. pyrifera with the predominant commercial kelp feed species, Ecklonia maxima. Young M. pyrifera grew well on the culture system, with mean upright length nearly doubling over the culture period (55.6–102.2 cm) and displayed mean upright relative growth rates between 0.99 and 1.22% day-1. Additionally, holdfasts developed new uprights and holdfasts increased in size, growing around culture lines. Simulated partial harvesting of samples stopped upright elongation, but samples survived, whereas complete removal of uprights caused mortality. Haliotis midae fed with M. pyrifera + formulated feed (SAF 3000®) displayed comparable growth rates to the E. maxima + SAF 3000® diet. No significant differences in mean specific growth rate (M. pyrifera 0.19, E. maxima 0.18% body weight day-1), daily increment in shell length (M. pyrifera 31.19, E. maxima 24.64 μm day-1), condition factor (M. pyrifera 1.37, E. maxima 1.40 g mm-1) and mortality rate were identified between the two diets. Additionally, H. midae consumed significantly less M. pyrifera than E. maxima, suggesting potential differences in feed conversion ratio/kelp nutritional composition among the kelp species. These findings provide baseline information for the potential cultivation and use of M. pyrifera as a new source of fresh seaweed feed in the South African abalone industry.

Effect magnitudes of operational-scale partial harvesting on residual tree growth and mortality of ten major tree species in Maine USA

Silvicultural systems based on partial harvesting (PH) have become increasingly common in areas historically dominated by clearcut-based systems in response to ecological and social concerns. Current knowledge about the effects of PH is based primarily on stand responses from controlled experiments from limited number of sites. A broader scope of inference is needed to fully understand the effects of PH when applied operationally at a landscape scale. We used 835 permanent monitoring plots from the US Forest Service Forest Inventory and Analysis network to quantify the effect magnitude (EM) of low- (5–40% basal area removal) and high-intensity (41–80% basal area removal) PH on the periodic diameter growth and mortality of residual trees of ten major tree species in Maine, USA. Our results showed that the EM and timing of statistically significant effect (p < 0.05) of the two intensities of PH varies across species. Tree diameter growth responses to high-intensity PH was rapid and prolonged for sugar maple (Acer saccharum) and American beech (Fagus grandifolia), while other species did not show significant responses for at least five years. High-intensity PH increased mortality of American beech, balsam fir (Abies balsamea), red spruce (Picea rubens), northern white cedar (Thuja occidentalis), and red maple (Acer rubrum), but not for other tree species. No relationship was found between species shade tolerance and species-specific response magnitude to PH in terms of diameter growth and tree- or stand-level (absolute or relative) mortality. This result suggests that species shade tolerance does not always determine the type or magnitude of response that a given species has to increased resource availability following PH and that other functional traits may be more important. Overall, the findings provide strong evidence that subsequent tree responses to PH are not consistent among contrasting species for at least 15 years following harvest and longer-term regional assessments are needed.

Assessing Tree Mortality Probability in Harvested Hardwood Stands Using Long-Term Forest Inventory Data

Abstract Partial harvesting (here defined as removal of ≤50% of preharvest volume) is the predominant silvicultural scheme applied to hardwood forest types in the eastern United States. Future stand conditions are largely reliant on trees retained after harvest, so their mortality because of harvesting activity damage should be minimized or taken into account when planning. We quantify partially harvested stand characteristics and postharvest mortality using data from 32,057 forested conditions, 366,953 trees with a diameter at breast height (dbh) ≥ 2.5 cm, of which 4,469 trees were cut and used in partially harvested stands. On average 23.3% of stand volume was selectively harvested with an additional 2.5% of volume lost to harvesting-caused mortality. Of the trees killed by logging activity in harvested stands, 90.7% were under 28 cm dbh. The likelihood of mortality was 1.31 times higher (95% CI of 1.20 to 1.44) for trees retained in stands that had undergone partial harvesting than for trees growing in unharvested stands. Commercial species had lower odds of mortality (0.88 times) in harvested stands than noncommercial species. Residual trees in harvested stands on private lands had a higher probability of mortality (1.23 times) than those on harvested public lands.

Energy balance estimation of growing corn for grain with alienation of its by-products for bioenergy needs

Annotation Purpose. Energy assessment of growing corn for grain with a comparison of two options for the use of corn by-products: partial collection of the by-products as solid biofuel for heat production or leaving all the crop residues in the field with further plowing them into the soil and heating with natural gas. Methods. Theoretical methods of designing technological processes in crop production, energy assessment of mechanized crop production technologies, life cycle analysis and computer modeling. Results. A comprehensive energy analysis with the inclusion of all technological processes of growing corn for grain, partial harvesting of its by-products and further use for heat production compared to plowing all the crop residues into the soil and using natural gas for heating. Conclusions. It is established that by meeting the agronomic requirements for the alienation of corn for energy needs, significant savings in anthropogenic energy per unit of heat produced compared to the option of plowing all the crop residues into the soil and using natural gas for heating. Keywords: energy analysis, corn, by-products, crop residues, biofuel, heat, heating.

Long-term effects of alternative partial harvesting methods on the woody regeneration layer in high-elevation Quercus rubra forests of the southern Appalachian Mountains, USA

High-elevation Quercus rubra forests in the Appalachian Mountains represent a transition zone between temperate mixed-Quercus forests that dominate lower elevations (<1350 m) and Picea-Abies forests at high (>1530 m) elevations. Little information exists specific to the response to disturbance, including timber harvesting, in these forests. In this study, we examined the long-term (22 years) effects of alternative regeneration methods – group selection harvests (GSH) and shelterwood with high (SWH; 9.0 m2/ha) and low (SWL; 5.0 m2/ha) residual basal area, and undisturbed control (CON) – on the development of the regeneration layer in high-elevation Q. rubra forests in the Appalachian Mountains. Treatments affected the density of the regeneration layer (stems ha−1; SPH), but results varied by species group. Density of Q. rubra saplings (stems ≥ 3.8 cm dbh and <10.9 cm dbh) was significantly greater in GSH (250 SPH), SWH (85 SPH), and SWL (121 SPH) than CON (0 SPH). For shade-tolerant species, density averaged 1095 SPH in SWH and SWL and was significantly greater than in CON. Shade-tolerant Acer rubrum was the most abundant species in the sapling layer 22 years post-harvest. Survival of individuals tagged and followed over time was unaffected by treatment, however, height of Quercus seedlings was greatest in treatments with lower residual basal area (GSH and SWL). At Y22, the relatively low density of successfully regenerated Quercus stems in the regenerated stands suggests that additional treatments, including crown-touch release and/or prescribed burning, may be necessary to secure the continued recruitment of Quercus in these high-elevation Q. rubra forests.

Development of Redwood Regeneration after Conifer Partial Harvest and Hardwood Management

Abstract Harvesting of commercial conifer species from conifer-hardwood mixtures can leave residual stands dominated by hardwoods. Removing unwanted hardwoods by cutting or herbicide makes growing space available to residual trees and regeneration and can restore conifer dominance. Forest managers of north coastal California need guidance on how such treatments affect subsequent growth of planted redwoods (Sequoia sempervirens [D. Don.] Endl.) or natural regeneration, as well as proliferation of undesirable species. Our observational study reconstructed growth of 108 regenerating redwoods in 26 treated stands. Residual stand density was the main driver of height and diameter growth in the new cohort of redwoods, irrespective of whether hardwoods were cut or received herbicide frill treatment (prevents resprouting). At lower residual stand densities, there were higher densities of natural regeneration (ingrowth) of conifers and hardwoods, which affected diameter at breast height (dbh) growth of regenerating redwoods. After heavier cutting of hardwoods, this ingrowth comprised a greater proportion of unwanted hardwood regeneration. Therefore, frill treatment is recommended when the objective of management is to reduce hardwood stocking and regeneration. Combining partial harvesting of conifers with cutting or frill treatment of hardwood is another option that reduces stand density to promote height and dbh growth of regenerating redwoods.