Current Harvesting Techniques Research Articles

Evaluating Guayule (Parthenium argentatum A. Gray) Germplasm Grown in Spain: Rubber and Resin along Three Production Cycles.

Rubber and resin are potentially important products of guayule (Parthenium argentatum A. Gray) that can assure the profitability of this crop as an agricultural alternative for the semi-arid areas of central and eastern Spain. This study analyzes, for the first time, the changes in rubber and resin production across 27 guayule accessions (traditional and modern) and along three cycles under the agroclimatic conditions of Castilla-La Mancha, simulating industrial management with a biannual harvest. The rubber content (% of dry mass) increased from 4.2% in one-year-old plants to 6.6% in two-year-old plants, but decreased after harvesting. Contrastingly, the rubber yield doubled in contiguous sampling, reaching a mean of 303.6 kg ha-1, with a maximum yield of 341.2 kg ha-1 after the first harvest. Three patterns of rubber production were established based on the production periods. A similar analysis was performed for resin production, which was heterogeneous across accessions belonging to the same rubber groups. In this case, three independent groups were established to classify the resin accumulation profiles following the same criteria of production periods. Here, we demonstrate that biannual harvesting has the potential to enhance rubber accumulation in summer, although more research is needed for its adaption to current harvesting techniques in this area.

Transmissive Labyrinthine Acoustic Metamaterial-Based Holography for Extraordinary Energy Harvesting.

Conventional energy sources are continuously depleting, and the world is actively seeking new green and efficient energy solutions. Enormous amounts of acoustic energy are dissipated daily, but the low intensity and limited efficiency of current harvesting techniques are preventing its adoption as a ubiquitous method of power generation. Herein, a strategic solution to increase acoustic energy harvesting efficiency using a specially designed metamaterial is implemented. A scalable transmissive labyrinthine acoustic metamaterial (LAM) is designed, developed, and employed to maximize ultrasound (40 kHz) capture over its large surface area (>27 k mm2), which is focused onto a piezoelectric film (78.6 mm2), thus magnifying incident sound pressure by 13.6 times. Three different piezoelectric films - two commercial and one lab-made nanocomposite film are tested with LAM in the acoustic energy harvesting system. An extraordinary voltage gain of 157-173% and a maximum power gain of 272% using the LAM compared to the case without the LAM are achieved. Multipoint focusing using holographic techniques, showcasing acoustic patterning to allow on-demand simultaneous harvesting in separate locations, is demonstrated. Our versatile approach for high-intensity acoustic energy harvesting opens future opportunities to exploit sound energy as a resource to contribute toward global sustainability.

Donor Tissue Preparation for Descemet Membrane Endothelial Keratoplasty: An Updated Review.

To provide an overview of the current literature on donor tissue preparation for Descemet membrane endothelial keratoplasty (DMEK). A comprehensive database search without date restrictions was performed in PubMed and in The Cochrane Library in May, 2017. Keywords included Descemet membrane endothelial keratoplasty, corneal transplantation, graft, harvest, dissection, preparation, endothelial cell, and endothelial cell density. Articles aiming to describe or evaluate a technique for DMEK graft preparation were considered eligible and were included in this review. A graft dissection technique that provides consistent tissue qualities and a low risk of preparation failure is essential for surgeons and eye banks preparing DMEK tissue. Various techniques have been described aiming to facilitate DMEK graft dissection, including manual dissection, pneumatic dissection, and hydrodissection. All show a trend toward a no-touch technique, for example, without direct physical tissue manipulation during tissue harvesting, as a potential ideal approach to minimize graft damage. An overview of the current harvesting techniques available for DMEK may benefit corneal surgeons and eye banks in choosing the best approach for each specific user.

Prescribed burning of harvested boreal black spruce forests in eastern Canada: effect on understory vegetation

Ecosystem-based management advocates that forestry disturbances should aim to emulate natural disturbances to mitigate the landscape-level impact of forest management. This study compares the impact of clear-cuts followed by a prescribed burn (CCPB) with clear-cuts alone (CC) and current careful logging practices (CLAAG: “careful logging around advanced growth”) on understory composition within black spruce (Picea mariana Miller (BSP)) paludified forest stands at the plot, site, and treatment levels using a functional-type approach. Vascular and nonvascular taxa showed significant differences in composition at the plot level among treatments. We found that pioneer taxa occurred mainly in CCPB sites, while late-successional taxa characterized CC sites. CLAAG sites had higher taxa richness than CCPB and CC sites, and we found that CCPB treatments were most likely to promote vascular taxa compositions that are more similar to those observed after natural disturbances. Additionally, the relative abundance of Sphagnum spp., responsible for paludification, was significantly reduced in sites treated by prescribed burning. This study therefore presents results suggesting that prescribed burning might represent a sustainable alternative to current harvesting techniques in the Clay Belt of eastern Canada that could help in preserving biodiversity (in terms of understory species assemblage) while maintaining or even enhancing forest productivity.

Using insights from animal behaviour and behavioural ecology to inform marine conservation initiatives

The impacts of human activities on the natural world are becoming increasingly apparent, with rapid development and exploitation occurring at the expense of habitat quality and biodiversity. Declines are especially concerning in the oceans, which hold intrinsic value due to their biological uniqueness as well as their substantial sociological and economic importance. Here, we review the literature and investigate whether incorporation of knowledge from the fields of animal behaviour and behavioural ecology may improve the effectiveness of conservation initiatives in marine systems. In particular, we consider (1) how knowledge of larval behaviour and ecology may be used to inform the design of marine protected areas, (2) how protecting species that hold specific ecological niches may be of particular importance for maximizing the preservation of biodiversity, (3) how current harvesting techniques may be inadvertently skewing the behavioural phenotypes of stock populations and whether changes to current practices may lessen this skew and reinforce population persistence, and (4) how understanding the behavioural and physiological responses of species to a changing environment may provide essential insights into areas of particular vulnerability for prioritized conservation attention. The complex nature of conservation programmes inherently results in interdisciplinary responses, and the incorporation of knowledge from the fields of animal behaviour and behavioural ecology may increase our ability to stem the loss of biodiversity in marine environments.

The remarkable population size of the endangered clam Tridacna maxima assessed in Fangatau Atoll (Eastern Tuamotu, French Polynesia) using in situ and remote sensing data

AbstractSeveral lagoons of the Eastern Tuamotu Atolls (French Polynesia) are characterized by enormous populations of the clam Tridacna maxima, a species considered as endangered in many locations worldwide. This unique resource is virtually intact, until recently being impacted only by local consumption. Increasing exports to Tahiti's market (up to 50 tonnes of wet matter y−1), combined with the relatively small size of these lagoons (<50 km2), have raised significant concerns for agencies charged with management of lagoonal resources. In order to evaluate whether the current harvesting pressure threatens long-term sustainability of this resource, it is necessary to estimate the total number of individual clams present and also the fraction of that stock that is currently targeted by fishers, who generally collect clams in very shallow waters (<1 m), walking on the reef edges. Here, we present results for a pilot study evaluating this resource at Fangatau Atoll. Using a combination of data collected in situ and three remotely sensed images with different spatial resolution (1.5, 5.6, and 30 m), we estimate that the shallowest lagoonal areas (4.05 km2 at depth <6 m) harbour five classes of benthic habitat with significantly different clam areal covers and densities. Considering the cover/density values for each habitat class, 23.65 ± 5.33 million clams (mean ± 95% confidence interval) inhabit these 4.05 km2. Assuming that current harvesting techniques will be maintained in the future, the commercially available stock represents 44% of the population located on 1.18 km2 of the shallow lagoon. A comparison of results from the three remote sensing platforms indicates that high resolution, broadband multispectral sensors (e.g. IKONOS, Quickbird) should provide the best existing platforms to conduct similar assessments elsewhere.

Are clearcuts appropriate for the mixed forest of Québec?

Sustainable forest management involves, among other things, maintaining diversity of ecosystems and preserving their natural processes. The main objective of this paper is to consider the validity of current harvesting techniques applied to the mixed forest of Québec. The old-growth mixed forest naturally regenerates by gap dynamics. However, the harvesting technique most commonly used in the mixed forest is clearcutting, with the result that succession must start over from the beginning. A general forest succession model applicable after such large disturbances is proposed. The most positive estimate indicates that the mixed forest will not be re-established earlier than 250 years after clearcutting. To ensure sustainable development in the mixed forest, harvesting techniques should imitate natural regeneration processes. Key words: balsam fir-yellow birch stands, CPRS, gap dynamics, succession model, sustainability, sustainable development

Harvesting techniques, hemiparasites and fruit production in two non-timber forest tree species in south India

Increasing demands for non-timber forest products and their commercial extractions can result in harvesting methods that maximize short term economic gains with little attention to long term ecological consequences. We assessed the ecological impacts of harvesting techniques used by an indigenous group, the Soligas, on the non-timber forest products they extract from the forests of Biligiri Rangan Hills, south India. Specifically, we examined patterns of resource availability of two non-timber tree species, Phyllanthus emblica and P. indofischeri, and how the current fruit harvesting techniques influence fruit yields, and susceptibility of trees to infestations by hemiparasitic plants of the Loranthaceae family. We also assessed how hemiparasite infestations affect fruit production and growth rates of Phyllanthus trees. There was considerable variation in fruit production in both species of Phyllanthus from one fruiting season to the next. The Soligas harvest an average of 86% (±17.72%) of the fruit yield on a per tree basis in P. emblica and 94.17% (±6.9%) in the case of P. indofischeri. At the population level, 64.75 and 86.6% of the fruit productivity is harvested in P. emblica and P. indofischeri, respectively. However, not all individuals or populations are harvested. Harvesting techniques used resulted in cutting of 15% of P. indofischeri trees and 5% of P. emblica trees. The current harvesting techniques used by the Soligas reduce fruit production in P. emblica in the following year ( R 2=0.27, p=0.03). Furthermore, the Soligas selectively harvest fruits from trees that have larger fruit crop sizes in both species. Individual trees that carried a greater load of hemiparasites produced significantly lower fruit yields ( P. emblica: r=−0.32, p<0.013; P. indofischeri: r=−0.73, p<0.001). The presence of hemiparasites significantly affected the growth rates of trees. Current harvesting techniques used by the Soligas have negative impacts on trees of Phyllanthus spp., as do infestations by hemiparasites. Current fruit harvesting strategies and techniques used by the Soligas focus on maximizing the economic returns by adopting methods of extraction such as lopping of branches and cutting of trees. Such practices can ultimately decrease the rates at which the populations grow, thereby making the extraction of Phyllanthus fruits unsustainable. Adopting more sustainable methods of harvesting appears to be one viable solution to the current ecological problem facing the conservation of Phyllanthus trees in the forests of Biligiri Rangan Hills.

Shrimp seed recruitment in mixed shrimp and mangrove forestry farms in Ca Mau Province, Southern Vietnam

The densities of shrimp seed recruited into ponds at mixed shrimp and mangrove forestry farms in Ca Mau province, southern Vietnam, were monitored semi-continuously from 1996 to 1998 to determine whether shrimp culture in the region is recruitment-limited. The numbers of shrimp seed lost during harvests were also monitored to assess whether current management strategies contribute to low stocking densities and pond production. Shrimp seed recruitment densities were low and highly variable with farms recruiting less than 1 postlarva m −3 between August 1996 and May 1997. Recruitment varied significantly with season ( P=0.0014), with peaks in October to November and April to May, the former having the highest recruitment densities. This trend is consistent with seasonal offshore spawning events in southern Vietnam. Recruitment did not vary significantly between day and night ( P=0.8), although data suggest that recruitment may be higher at night during peak recruitment months (November, February). Postlarval densities were significantly higher on the first day (24 h) of each spring tide period ( P=0.0046). Mean total length of shrimp seed was 13.72±0.35 mm, which indicates that farms are recruiting postlarvae approximately 15–20 days post-metamorphosis (PL 15–20), or 35 days post-hatch, into ponds. Recruitment densities were higher at farms on rivers than at farms on small canals during March/April 1998, which corresponded with peaks in immigration of postlarvae into estuaries on tidal currents at this time. The numbers of shrimp seed lost during harvests were high, reducing net recruitment and net stocking densities to 0.15 postlarvae m −2 from a potential gross stocking density of 0.35 postlarvae m −2. Shrimp culture in Ca Mau province is recruitment-limited. This is a major factor contributing to low shrimp yields in the region. Current harvesting techniques need to be modified to reduce postlarval losses and improve overall stocking densities and pond production.