Plastic Shelters Research Articles

Conspecific and heterospecific cueing in shelter choices of Blaptica dubia cockroaches.

Like many cockroaches, Argentinian wood roaches, Blaptica dubia, prefer darker shelters over lighter shelters. In three experiments, we asked whether chemical cues from other roaches might influence shelter choice, a process known as conspecific or heterospecific cueing, depending on whether the cues come from an individual of the same or a different species, respectively. Each experiment involved trials with focal B. dubia cockroaches in testing arenas containing plastic shelters of varying levels of darkness, with filter paper under each shelter acting as a carrier for chemical cues. In Experiment 1, we tested female and male B. dubia cockroaches with two shelters matched for darkness but differing in cues (conspecific vs. none). The shelter with no cue contained a blank filter paper as a control. In Experiment 2 (conspecific cueing) and Experiment 3 (heterospecific cueing), we tested B. dubia cockroach choices for lighter or darker shelters with filter papers containing chemical cues of other roaches or no chemical cues. For the conspecific cueing study of Experiment 2, we used chemical cues from other B. dubia cockroaches. In contrast, for the heterospecific cueing study of Experiment 3, we used chemical cues from a different species, the death's head cockroach, Blaberus craniifer. In Experiment 1, B. dubia cockroaches overwhelmingly preferred shelters with conspecific chemical cues over darkness-matched shelters without cues. In Experiments 2 and 3, they strongly preferred darker shelters, especially when chemical cues were present. Additionally, they were more likely to be under the lighter shelter when chemical cues were present there. These results reveal that the public information B. dubia cockroaches gain from chemical cues-including those from other species-can drive shelter choices in this species.

Новый пчелоопыляемый гибрид огурца селекции ФГБНУ ФНЦО Храбрец F1

Cucumber is an economically important vegetable crop, which grown in the open field and in various cultivation facilities; at the moment, the range of cucumber hybrids is large, but not all of them sufficiently meet the requirements of the market. The creation of competitive high-yielding hybrids that meet the requirements of the modern market with complex disease resistance for greenhouses, plastic shelters and open ground is the main focus of breeding research on cucumber culture. One of the important areas of breeding work with cucumber culture is the creation of highly productive bee-pollinated hybrids for open ground, temporary shelters and plastic shelters. Preference is given to hybrids of a mixed type of flowering with a high saturation of female flowers, resistant to major diseases and unfavorable growing conditions, with short tuberculate fruits of a universal type of use. As a result of the research, a heterotic hybrid Khrabrets F1 was obtained and included in the State Register of Breeding Achievements approved for use in 2022. Khrabrets F1 an early ripe bee-pollinated hybrid for growing in greenhouses, under temporary shelters and in open ground. The period from germination to the beginning of fruiting is 42-44 days. Fruit is 10-12 cm, cylindrical, medium-tuberous, white-spiked, saturated green color. Hybrid Khrabrets F1 has very good taste. The hybrid has resistant to Cladosporium cucumerinum (Ccu), powdery mildew (Px), and tolerant to pseudoperonospora cubensis (Pcu). A hybrid of universal purpose, intended for fresh consumption, pickling and canning.

Economic Feasibility of Plastic Shelter Tomato Production Method under Rain-Fed in Fogera Plain, North Western Ethiopia

The research intervention was conducted in Fogera plain commonly known and consists of (Fogera, Dera and Libokemkem districts) of South Gondar Zone to evaluate economic feasibility of the new tomato production method using plastic shelter under rain fed production condition. Two types of improved tomato varieties were used known as Melkasalsa and melkashola, each variety within 200 m 2 plots of land. A sum of 5 kebeles/sites and 11 technology beneficiaries (farmers) were addressed under this intervention in three districts. Data on input costs, benefits among other parameters were collected and recorded through intensive field observation and follow up, field days, focused group discussion. Quantitative types of data such as yield, participants in different events through field day, training and exchange visit and qualitative types of data like feed backs, farmers’ perception and preference on demonstrated rice technologies. The use of plastic shelter in tomato production under rain-fed condition had considerable impact on yield performance. The relative yield advantage of tomato production using plastic shelter is better than without shelter production. Regarding profitability issues, the result shows, tomato production using plastic shelter was by far profitable than without shelter production in both varieties. The estimated value of marginal rate of return with shelter production was greater than one for both varieties. An investment of one Ethiopian Birr (ETB) on new production method using plastic shelter could generate additional net income of 20 ETB and 14 ETB from melkasalsa and melkashola varieties, respectively. Hence farmers and respective bodies need to strengthen production of tomato in the rainy season using shelter to get more returns and enhance their livelihood and economic benefits. Keywords: Marginal rate of return, Melka Salasa, Melka shola, Partial budget analysis, Plastic shelter, rain-fed DOI: 10.7176/JESD/13-1-02 Publication date: January 31 st 2022

Fumigation practice combined with organic fertilizer increase antibiotic resistance in watermelon rhizosphere soil

Chemical fumigants and organic fertilizer are commonly used in facility agriculture to control soil-borne diseases and promote soil health. However, there is a lack of evidence for the effect of non-antibiotic fumigants on the distribution of antibiotic resistance genes (ARGs) in plant rhizosphere soils. Here, the response of a wide spectrum of ARGs and mobile genetic elements (MGEs) to dazomet fumigation practice in the rhizosphere soil of watermelon was investigated along its branching, flowering and fruiting growth stages in plastic shelters using high-throughput quantitative PCR approach. Our results indicated that soil fumigation combined with organic fertilizer application significantly increased the relative abundance of ARGs and MGEs in the rhizosphere soil of watermelon plant. The positive correlations between the relative abundance of ARGs and MGEs suggested that soil fumigation might increase the horizontal gene transfer (HGT) potential of ARGs. This result was further confirmed by the enhanced associations between ARG and MGE subtypes in the networks of fumigation treatments. Moreover, bipartite associations between ARGs/MGEs and microbial communities (bacteria and fungi) revealed a higher percentage of linkage between MGEs and microbial taxa in the fumigated soils. Structural equation model analysis further suggested that the increases in antibiotic resistance after fumigation and organic fertilizer application were mainly driven by MGEs and fungal community. Together, our results provide vital evidence that dazomet fumigation process combined with organic fertilizer in plastic shelters has the great potential to promote ARGs' dissemination in the rhizosphere, and raise cautions of the acquired resistance by soil-borne fungal pathogen and the potential spreading of ARGs along soil-plant continuum.

The environmental performance of protecting seedlings with plastic tree shelters for afforestation in temperate oceanic regions: A UK case study

Restoration of forested land represents an effective strategy to achieve net-zero target emissions by enhancing the removal of greenhouse gases from the atmosphere. The most common afforestation strategy envisages planting seedlings, which are germinated and grown to the desired age at tree nurseries, with plastic shelters to increase growth and survival of trees. This article presents a comprehensive Life Cycle Assessment (LCA) study that compares the environmental performance of current and prospective scenarios for shelter-aided seedling planting compared with a base case where shelters are not employed. The study focuses on the UK, but results and conclusions are valid for other temperate oceanic regions. The scenarios investigated are a combination of different shelters materials and end-of-life (EoL) strategies. Our analysis demonstrates that (i) planting seedling without shelters is the most preferable option across most environmental impact categories (including Climate Change), and in terms of weighted results, (ii) polypropylene shelters are preferable to bio-based alternatives, including polylactic acid-starch blends and bio-polypropylene, (iii) recycling is the most environmentally advantageous EoL treatment. Our study also showed that that the carbon emissions of the scenarios investigated are negligible when compared to the amount of carbon sequestered by a tree in 25 years.

Climate change adaptation strategies in the highland by vegetable farmers

The Highland of Magelang Regency has a strategic role as a vegetable production center in Central Java. Farmers in the highlands of Magelang cultivate various types of vegetables. Since highland vegetable farming hugely depends on rainfall as a primary water source, climate change remarkably affects farming. Vegetable farmers often encounter problems due to climate changes in drought and highly intense rainfall, which caused crop damage. Since specific studies on vegetable farmers’ adaptation strategies to cope with climate changes and their economic effects are still limited, this research aimed to study the phenomenon. The observation was performed by interviewing all members (20 farmers) of the Mutiara Organic farmers group in Sumberejo Village, Ngablak Sub-Regency, Magelang Regency, conducting field observation and soil analysis in September-November 2018. The results showed that farmers developed several adaptation strategies to deal with climate change, namely applying multiple cropping systems, developing organic agriculture, growing vegetables under plastic shelters, and expanding a vegetable nursery as an alternative source of income. Farmers cultivated extra crops in the wet season due to abundant water availability. Organic vegetable farming, which began in 2013, from the higher value of the benefit-cost ratio, was more profitable than non-organic farming. Besides, organic farming’s land quality was also better based on organic carbon (C-organic), Nitrogen (N), Cation Exchange Capacity (CEC), and other nutrients. Therefore this study recommended to develop organic vegetable farming on a broader scale and seriously support farmers’ vegetable nursery business, since it was profitable, contributed significant income for farmers, and strategic for vegetable farming industries development.

Microbial assembly and association network in watermelon rhizosphere after soil fumigation for Fusarium wilt control

Soil fumigation is an effective method to control soil-borne diseases like Fusarium wilt, however the processes and mechanisms driving microbial community reestablishment and pathogen suppression in the rhizosphere after fumigation remain poorly understood. In this study, we examined the dynamics of the rhizosphere microbiome and microbial network associations across different watermelon development stages and plant statuses (i.e. healthy and dead) after soil fumigation and organic fertilizer (OF) application in plastic shelters with Fusarium oxysporum f. sp. niveum (FON) heavily infected. Our results showed that fumigation treatments significantly reduced Fusarium wilt disease incidence and pathogen abundance, meanwhile, decreased soil microbial metabolic activity, fungal biomass and diversity. Bacterial community recovered from fumigation suppression in a short period, while fungal suppression was longer lasting, resulting in decreased fungi to actinomycetes (F/A) and fungi to bacteria (F/B) ratios in PLFA profiles. We further found some bacterial families, such as Actinospicaceae within Actinobacteria, Haliangiaceae, Rhizobiaceae and uncultured Rhodospirillales within Proteobacteria, Sporolactobacillaceae and Limnochordaceae within Firmicutes were greatly enriched after fumigation and might potentially contribute to pathogen suppression. The fumigation treatments significantly reduced microbial network complexity and the percentage of fungal nodes in comparison to un-fumigated control treatment. In contrast, a more complex microbial network was observed in the rhizosphere soil of healthy plants than that in the soil surrounding dead plant roots within fumigation treatments. Furthermore, healthy plant rhizosphere significantly enriched potential beneficial and nitrogen cycle-related bacterial phyla like Gemmatimonadetes, Verrucomicrobia, and Nitrospirae. More interestingly, Fusarium were markedly enriched in the rhizosphere soil of healthy plants and mainly represented by non-FON Fusarium like F. verticillioides and F. solani, implying a potential niche competition between FON and nonpathogenic Fusarium species in the rhizosphere of healthy watermelon. Taken together, our results provide vital information on the reconstruction of microbial communities and potential interactions between plant and its beneficial consortium after fumigation, which is instructive to develop more systematic strategies through targeting both beneficial and pathogen-similar taxa to improve disease control and soil suppression.

Responses of Tomato Varieties to Rainy Season Production under Low Cost Plastic Shelter

Responses of Tomato Varieties to Rainy Season Production under Low Cost Plastic Shelter

PENGARUH WARNA NAUNGAN PLASTIK DAN DOSIS PUPUK ORGANIK KOMPOS TERHADAP PERTUMBUHAN BAWANG MERAH (Allium ascalonicum L.)

The aim of the research was to study the effect of calors plastic shade and dosage organic fertilizer and the interaction on the growth analyze of Shallots. The experiment was conducted in experiment field of Agriculture Faculty, University Muhammadiyah of Jember.The experiment was arranged in Randomized Block Design consisted of 4 x 3 factorial treatments with three replications. The first factor were 3 levels of Transparent Plastic Shelter, i.e.: clear, blue, and red. The second factor were 4 levels of compost organic fertilizer application, i.e.: 15, 20, 25 and 30 t/ha. The results showed a significant interaction between the color shade of plastic and a dose of organic fertilizer on the parameters of leaf area age 60 days after planting and leaf area index age 60 days after planting, treatment shade of blue with organic fertilizer 30 tons / ha showed the best effect on leaf area and treatment shade of blue with dosages of 25 tons / ha showed the best effect on leaf area index. Use of shade of blue give the best effect on leaf area age 60 hst and shade of red gives the best effect on the growth rate of plants. The treatment dose of organic fertilizer 25 tons / ha gives the best effect on leaf area index age of 60 days after planting, the rate of plant growth, and relative growth rate, and treatment with a dose of fertilizer 30 ton / ha.

Soil conditions and sheltering techniques improve active restoration of degraded Nothofagus pumilio forest in Southern Patagonia

Nothofagus pumilio forests in the Southern Patagonia region of Chile are highly degraded because of clearing for human settlements, extensive livestock grazing, and more recently, the impact of coal mining operations. Most of these legacy areas have remained as extensive meadows of non-native grasses and legumes with limited Nothofagus pumilio forest recovery due to dry soil moisture conditions and exposure to high wind and solar radiation. Therefore, active reforestation is needed to reclaim Nothofagus pumilio forests from abandoned grassland or disturbances caused by surface mine operation. In this study, a surface coal mine operation and an abandoned meadow established in the 1950 s needed to be restored back to N. pumilio forest on Riesco Island, in Southern Chilean Patagonia. We compared the establishment success of Nothofagus pumilio seedlings on replicated blocks under two conditions (experimental treatments): (i) four blocks of meadow previously disturbed by livestock grazing, (MS), and (ii) four blocks where a deep layer of the soil profile was removed, mixed, and then replaced simulating recommendations used for reclaiming surface coal mines (RS). To improve Nothofagus pumilio establishment and protection at each block under both soil conditions, seedlings were planted both unprotected and protected from wind and solar radiation using four different types of shelters: shade cloth, irregular log piles, white polypropylene shelters, and woody branches. Soil physical and chemical properties, seedling survival and growth, leaf water potential, and stomatal conductance were measured. Results at the end of the first and fourth growing seasons showed better conditions for seedling growth in the RS treatment. Mean survival rates began to be different following the second growing season with values of 84.7 ± 2.9% in RS and 60.2 ± 3.2% survival in MS treatments, respectively. At the end of the study, the difference between the treatments was even geater with values of 75.4 ± 5.5% and 32.2 ± 7.1%. Soil removal and replacement significantly changed soil physical properties, but values were still adequate for vegetation development. The use of shelters significantly influenced four-year survival rates of seedlings planted on the disturbed MS treatment with 60 ± 8.2% survival in plastic shelters and less than 25.5 ± 6.5% for all other shelters. The effects of the shelters were less clear in the RS treatment. Our study showed that Nothofagus pumilio restoration on abandoned grassland and reclaimed mine sites in Patagonia is a feasible option when soil conditions and planting techniques improve soil water availability, and when seedling are protected against excessive solar radiation and wind.

Characterizing spring emergence of adult Halyomorpha halys using experimental overwintering shelters and commercial pheromone traps

AbstractTo improve our understanding of adult Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) overwintering biology and to better inform models of its population dynamics, its temporal pattern of spring emergence was investigated using experimental overwintering shelters in screened cages within protective structures. In 2012, plastic shelters containing 100 adults were deployed in unheated, unlighted buildings, and adjacent woodlots in Virginia, USA. In 2013 and 2014, wooden shelters containing 300 paint‐marked adults were deployed in pairs in six woodlots across Virginia, West Virginia, and Maryland, USA; one in a closed cage and one in a cage with the top removed, enabling emerged adults to be counted or to disperse, respectively. In 2013 and 2014, pheromone‐baited and non‐baited pyramid traps encircled the shelters at each site. Regular counts of adults that emerged into the closed cage and of marked and ‘wild’ (unmarked) adults captured in traps were conducted from February or March through early July. In 2012, emergence patterns from shelters in buildings and woodlots were very similar and matched those recorded from woodlots in 2013 and 2014. In all years, a small peak of emergence occurred in about mid‐April, a larger and more prolonged peak was observed between mid‐May and early June, and emergence ended by early July. Of the 449 H. halys adults captured in traps between 2013 and 2014, only three were marked individuals from shelters in the open cage, suggesting that adults emerging from overwintering sites may require a dispersal flight before responding to pheromone‐baited traps. In 2013 and 2014, respectively, 98 and 93% of captures were in pheromone‐baited traps, but there was no correlation between the weekly number of adults that emerged from shelters in the closed cages and captures in traps.

Fruit Quality and Occurrence of Brown Leaf Spot Disease (Pseudocercospora vitis) according to the Width of Plastic Shelter in the Grape ‘Campbell Early’

Fruit Quality and Occurrence of Brown Leaf Spot Disease (Pseudocercospora vitis) according to the Width of Plastic Shelter in the Grape ‘Campbell Early’

Biomass decomposition and nutrient release from black oat and hairy vetch residues deposited in a vineyard

A significant quantity of nutrients in vineyards may return to the soil each year through decomposition of residues from cover plants. This study aimed to evaluate biomass decomposition and nutrient release from residues of black oats and hairy vetch deposited in the vines rows, with and without plastic shelter, and in the between-row areas throughout the vegetative and productive cycle of the plants. The study was conducted in a commercial vineyard in Bento Gonçalves, RS, Brazil, from October 2008 to February 2009. Black oat (Avena strigosa) and hairy vetch (Vicia villosa) residues were collected, subjected to chemical (C, N, P, K, Ca, and Mg) and biochemical (cellulose - Cel, hemicellulose - Hem, and lignin - Lig content) analyses, and placed in litter bags, which were deposited in vines rows without plastic shelter (VPRWS), in vines rows with plastic shelter (VPRS), and in the between-row areas (BR). We collected the residues at 0, 33, 58, 76, and 110 days after deposition of the litter bags, prepared the material, and subjected it to analysis of total N, P, K, Ca, and Mg content. The VPRS contained the largest quantities and percentages of dry matter and residual nutrients (except for Ca) in black oat residues from October to February, which coincides with the period from flowering up to grape harvest. This practice led to greater protection of the soil surface, avoiding surface runoff of the solution derived from between the rows, but it retarded nutrient cycling. The rate of biomass decomposition and nutrient release from hairy vetch residues from October to February was not affected by the position of deposition of the residues in the vineyard, which may especially be attributed to the lower values of the C/N and Lig/N ratios. Regardless of the type of residue, black oat or hairy vetch, the greatest decomposition and nutrient release mainly occurred up to 33 days after deposition of the residues on the soil surface, which coincided with the flowering of the grapevines, which is one of the phenological stages of greatest demand for nutrients.

Replacing mechanical thermometers with electronic thermometers in a Mediterranean test station and its impact on climatology

In the last two decades of the 20 th century, most meteorological networks replaced traditional mechanical thermometers (usually placed inside a Stevenson screen) with electronic ones (usually in the open air, protected by a plastic shelter). Impacts of such instrumental change on the climatology of daily minimum and daily maximum temperatures are assessed here, by analysing eleven years of data from a couple of stations operating in parallel in the same test site in a location with a Mediterranean climate. Seasonal effects (i.e. monthly biases ranging from -0.8C to +1C) were detected on maximum temperatures, but they compensate each other in the yearly average. In minimum temperatures, electronic thermometers introduced a -0.75C bias, regardless of the season. Specific biases due to horizontal winds and to vertical heat fluxes were also detected and studied. Two possible causes of the climatological bias were investigated: local wind conditions and different responses to turbulent heat fluctuations by electronic and mechanical thermometers. Other possible causes exist, but they could not be investigated due to a lack of data. The present study shows that, in the test site, replacing traditional thermometers with modern ones in climatological networks introduced an underestimate in minimum temperatures. This suggests that in locations with similar microclimates the real atmospheric warming could be even greater than that observed to date.

Transpiração e crescimento foliar de clones de batata em resposta à fração de água transpirável no solo

A água é vital para as plantas. Uma redução na disponibilidade de água pode afetar a transpiração e o crescimento foliar das culturas. O objetivo deste trabalho foi determinar a resposta da transpiração e do crescimento foliar ao conteúdo de água disponível no solo, representado pela fração de água transpirável no solo (FATS), em dois clones de batata (um antigo e um recente) adaptados ao Sul do Brasil. Foram realizados três experimentos em ambiente protegido por abrigo telado em Santa Maria, RS, dois deles na primavera (cultivo de safra), com plantios em 20/08/2008 (E1) e 20/10/2008 (E2), e um experimento no outono (cultivo de safrinha), com plantio em 25/03/2009 (E3), usando-se dois clones de batata: um antigo ('Macaca') e um recente ('SMINIA793101-3'). A água disponível, representada pela FATS, a transpiração e o crescimento foliar foram medidos diariamente durante o período de imposição da deficiência hídrica. A FATS crítica que começa a alterar a transpiração, indicativo do início do fechamento estomático, foi de 0,39, 0,47 e 0,28 no clone 'Macaca' e de 0,47, 0,49 e 0,33 no clone 'SMINIA793101-3', para os experimentos E1, E2 e E3, respectivamente, enquanto o crescimento foliar começou a ser reduzido, com valor de FATS crítica maior para o clone 'Macaca', indicando que o clone 'SMINIA793101-3' é mais tolerante ao déficit hídrico no solo que o clone 'Macaca'.

Yellow Dryad, a New Host Plant of Colletotrichum acutatum in Switzerland.

In spring 2008, yellow dryad (Dryas drummondii L.), an ornamental plant, was studied at the Research Center Conthey (Switzerland) for its possible use by the cosmetical industry. Plants grown from wild-type seeds were multiplied by transplanting cuttings in pots that were later transplanted in an experimental field plot. Before field planting, partial wilting occurred on several plants. The petioles of affected leaves appeared dry, tan, and covered with black acervuli containing black setae. Isolation from the acervuli on potato dextrose agar (PDA) containing chlortetracycline (25 mg/liter) resulted in the growth of white-to-gray mycelium containing salmon-colored conidial masses but no setae. The underside of the colony was carmine red. Conidia were primarily fusiform with an average size of 13 × 4 μm. On the basis of these morphological traits, the pathogen was identified as Colletotrichum acutatum J.H. Simmonds (2). PCR using the species-specific primer CaInt2 in conjunction with the conserved primer ITS4 (3) was conducted on genomic DNA from a single-spore isolate. An isolate of C. acutatum from strawberry was included as a positive control. This primer pair produced a 490-bp fragment that confirmed the identification based on morphology. A pathogenicity test was conducted at the end of August and beginning of September 2009. The single-spore isolate from yellow dryad and a single-spore isolate of C. acutatum from highbush blueberry (Vaccinium corymbosum located at Dürrenroth, Switzerland) were grown on PDA at 23 ± 2°C for 1 week. Conidial suspensions were prepared with 0.9% sterile NaCl solution and were adjusted to 3 to 5 × 105 spores/ml. For each spore suspension, five 3- to 5-cm tall, healthy, yellow dryad plants in the rosette stage were sprayed until runoff. Spraying five plants with a sterile 0.9% NaCl solution served as control treatment. Immediately after inoculation, plants were covered individually with a polyethylene bag and incubated at 23 ± 2°C for 5 days. Polyethylene bags were then removed and the plants were placed outdoors under a plastic shelter (18 ± 4°C). After 1 week, plants inoculated with either strain of C. acutatum showed the same symptoms. The most prevalent symptoms on leaves were brown necroses surrounded by a dark brown margin; the necrotic lesions were covered with black acervuli without setae. Less frequent were small, brown lesions that turned gray and were covered with acervuli containing setae. Acervuli with setae also occurred frequently on the petioles of the inoculated plants. On the control plants, none of these symptoms were observed. Leaves with lesions were incubated in a humid chamber for 1 day, resulting in abundant salmon-colored sporulation from the acervuli. C. acutatum was reisolated from such spore masses on PDA. To our knowledge, this is the first report of C. acutatum on yellow dryad. Since C. acutatum is a widespread pathogen worldwide (1), it represents a potential threat to yellow dryad crops grown for ornamental and potentially cosmetical use.

Forced migration and health - diarrhoea among adult Zimbabwean immigrants in Limpopo

To the Editor: The political and economic decline in Zimbabwe has forced many Zimbabweans to migrate to neighbouring countries and abroad. 1 A large number of Zimbabwean migrants live in poverty in the border region. The high demand for shelter forces some people to create and occupy very basic dwellings 2 and cook food in tin cans over fires. Many live in cardboard and plastic shelters, some in the back yards of overcrowded homes where they have to pay rent. Others sleep under trees next to roads or on open fields on farms, at railway stations or on the street. 3

Efficacy of Individual Barriers to Prevent Damage to Douglas-Fir Seedlings by Captive Mountain Beavers

Abstract We tested the ability of individual tree seedling protectors to deter mountain beavers from damaging Douglas-fir seedlings. Using captive mountain beavers in field pens, we tested 20 products representative of a wide range of barriers suitable for protecting individual tree seedlings from rodent damage. Eleven products protected 95% or more of seedlings from damage. Tree shelters and fabric shelters provided the most protection; 98 and 95% of seedlings were undamaged, respectively. Rigid mesh protector tubes protected 81% of seedlings, and protection netting protected 55% of seedlings. Purchase prices varied widely; protection netting was least expensive, followed by rigid mesh tubes, fabric shelters, and tree shelters. Seedling growth was greatest within fabric shelters and plastic tree shelters. Materials used to construct 15 of the 20 tree protectors were tested using captive mountain beavers in small sheltered pens. Here, samples of barrier materials were used to block access to a favored food. The four materials that excluded all test animals in all trials were from unvented tree shelters with solid seamless walls. Seven materials failed to exclude any animals in the sheltered-pen trials.

Decomposition of Douglas-fir coarse woody debris in response to differing moisture content and initial heterotrophic colonization

This experiment was designed to test the effects of moisture content and hetrotrophic community composition on the decomposition of coarse woody debris (CWD). In 1995, 360 freshly cut Douglas-fir logs were randomly assigned to 5 replicate sites, with 12 heterotrophic colonization × moisture treatment combinations at each site. Half of the logs in each heterotrophic treatment were placed under elevated clear plastic shelters to reduce precipitation inputs while the other half received unrestricted inputs. The heterotrophic colonization treatments (HCT) were designed to test the effect on decomposition of the initial timing of physical penetration of the bark by drilling holes into the phloem and sapwood, and insect vectoring of fungi by injecting basidiomycete and ascomycete inoculum into the sapwood. In summer of 2001, respiration was measured from one set of experimental logs and density change, the amount of area affected by brown rot and wood borer galleries (br/wbg) from another set of logs. The sheltered logs had significantly higher respiration rates than the unsheltered logs (0.70 g CO 2 m −2 d −1 versus 0.57 g CO 2 m −2 d −1 respectively). Sheltered logs also had significantly higher percentage of the log's total volume affected by br/wbg (6.3%) than in the non-sheltered logs (1.1%). Mean moisture content in the sheltered logs was 36%, significantly less than in the unsheltered logs (45%). There was also evidence that earlier insect entry into CWD can facilitate faster decomposition as indicated by higher respiration rates in the logs that had been experimentally penetrated. In sum, the results suggest that even small decreases in moisture content can significantly increase respiration rates through increased fungal and insect activity in the early stages of decomposition. However, after 6 years the differences in hetrotrophic activity did not result in significantly higher density loss in the drier logs.

Évaluation de la résistance à deux nématodes : Radopholus similis et Meloidogyne spp. chez quatre génotypes de bananiers au Maroc

Radopholus similis and Meloidogyne spp. are the main nematode parasites of banana plants grown under plastic shelters in Morocco. A test was made in pots to evaluate the resistance of four genotypes of banana to these nematodes. Infection by Meloidogyne spp. brought about an increase in root weight in all banana plants tested because of gall formation. The inoculation of R. similis produced a reduction in length and diameter of the pseudo-trunk as well as in root and aerial mass in all genotypes. Pisang jari buaya showed the significantly lowest number of Meloidogyne nematodes per 10 g of roots, whereas for R. similis, the significantly smallest numbers were obtained in Pisang berlin and Pisang jari buaya. Therefore, Pisang jari buaya was the only banana genotype studied to show some degree of resistance to both nematodes. To cite this article: A. Guedira et al., C. R. Biologies 327 (2004).