Competition For Environmental Resources Research Articles

Perennial forage legume cultivation and their above-ground mass management methods for weed suppression in arable organic cropping systems

BackgroundIn organic crop farms, growing crop yields are limited by insufficient nitrogen supply to plants and crop weediness. In such farms, legume swards are proposed as a service crop to improve nitrogen cycling. However, a positive effect of nitrogen is not only on cereals but also on weeds. In crop rotation, legume swards can stimulate the competition of cereals using the above-ground mass of legume to control the spread of weeds.The effects of the following methods for weeds control were analyzed: (i) forage legumes (Trifolium pratense L. and T. repens) undersown in cereals, (ii) forage legumes (T. pratense L., Medicago sativa L.) and their mixture with festulolium (x Festuliolium) and their above-ground mass management methods, and (iii) plant-based fertilizers (red clover above-ground mass fermented and composted).ResultsOat with red clover undersown reduced weediness more than red clover monocrops, pea, and their mixture with oats. Incorporated undersown white clover mass increased spring barley competitiveness with weeds. When growing legume swards for a longer period of time (green fallow), red clover and their mixture with festulolium are the most suitable for this purpose. The lowest weed dry weight (average 34%, compared with the removal from the field) was obtained while using the mixed management. The cultivation of cereals after forage legumes and their mixtures with festulolium (as a preceding crop) increases its grain yield and competitive ability against weeds. Fermented red clover and fermented pea and spring wheat mixture mass, as a manure, did not increase weediness.ConclusionsIt was concluded that the effectiveness of the perennial forage legumes is determined by the uses of the above-ground mass: soil cover, mulching, application of green manure, and intensity of mass mineralization. Type of activity of forage legumes on weeds were competition for environmental resources, disruption/promotion of germination, destruction of above-ground mass, reduction of the amount of matured seeds, creation of a physical barrier (mulch), and increase of competitiveness of cereals. Growing forage legumes in pure crops usually leads to a loss of marketable production.Graphic abstract

Growth assessment of juvenile oil palm (Elaeis guineensis Jacq.) intercropped with fruit vegetables in a rainforest zone of Nigeria

Improper intercropping of Elaeis guineensis with other crops has impaired the growth and development of the oil palm due to competition for environmental resources. The study was conducted to investigate the impact of intercropping on the growth of juvenile oil palm for 2 years. The research commenced during the rainy season of 2016 at an established juvenile oil palm plantation in Ala, Akure-North Local Government of Ondo State. Four fruit vegetables were intercropped separately within the alley of the plantation at 1, 2 or 3 m away from the oil palms in a randomized complete block design. Growth parameters of the juvenile oils were assessed. Results revealed that at 16 weeks after intercropping (WAI), the intercropped oil palm recorded better growth performance with higher canopy spread, number of frond, number of leaflets and trunk height (218.20, 37.00, 87.48 and 38.17 cm) respectively, than the sole oil palms (214.67, 32.83, 72.89 and 31.67 cm) respectively. There were no significant difference in all the growth parameters examined except canopy height (p < 0.05). Juvenile oil palm cultivated in rainforest agroecological zone of Nigeria can be intercropped with fruit vegetables without any deleterious effect when intercropped at minimum of 1 m away from the oil palms.

The Influence of Aqueous Extracts from Stellaria media L. on the Growth of Zea mays L. Cultivars

Plants introduce chemicals into the environment that can be toxic, both for themselves and for other species. Weed infestation of crops is a competition for environmental resources, but at the same time is a source of chemical substances released into the soil, often reducing yield potential. The paper attempts to investigate the allelopathic interaction of aquatic extracts from dry shoots of chickweed Stellaria media L. on germination and development of maize Zea mays L. seedlings of ‘San’, ‘Kidemos’ and ‘DKC 3441’ cultivars. Along with the increase in the concentration of allelopathic substances, a decrease in the germination activity of all tested maize cultivars was observed. Germination percentage as like percentage of control was the highest for seeds germinating on substrates with 1% chickweed extracts and the lowest for seeds watered with 5% extracts. Biometric measurements of seedlings showed that the most sensitive cultivar of maize was ‘DKC 3441’, and the resistant cultivar ‘San’. The relative water content was the highest for seedlings grown on the 5% extracts. Significant differences in the amount of fresh and dry masses of maize seedlings were demonstrated at the highest concentrations of extracts compared to the control. A significant increase in electrolyte leakage compared to the control sample was found in the ‘Kidemos’ cultivar. The lowest differences in the destabilization of the ionic transport through cell membranes for the ‘DKC 3441’ cultivar were demonstrated.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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Rice and Barnyardgrass: Water Stress and Initial Establishment

The present work aimed to evaluate the effect of different water stress levels on the development of both rice and barnyardgrass. The study was established into greenhouse, in completely randomized design, in factorial scheme 2 × 5, with four replications. Factor “A” comprised the plant species (rice cv. BRS Querência, or the weed Echinochloa crusgalli), and factor “B” comprised the water stress levels: (T1) continuous flood (CF); (T2) 0 kPa (saturated soil); (T3) 10 kPa; (T4) 40 kPa; and (T5) 100 kPa. Plant emergence was assessed every day; plant length was measured 30 days after planting. At the end of the experiment, the number of leaves per plant, root length and shoot and root dry mass were determined. Our data supply evidence that under moderate water stress, up to approximately 40 kPa, rice tends to perform better than barnyardgrass in the initial stage of crop growth, when under equivalent plant density. However, barnyardgrass is usually present in much higher plant density than crop plants in fields traditionally cropped with rice. Thus, efficient control of barnyardgrass should be accomplished to avoid damage to rice crop by competition for environmental resources.

Allelopathic activity of some grass species on Phleum pratense seed germination subject to their density

Efficient utilization of allelopathy in the agricultural practice requires searching for some species and developmental stages when the allelopathic substances are generated in bioactive concentrations. That also requires the knowledge of allelopathy mechanisms and primarily its separation from the other aspects of plant activity, mainly from competition for environmental resources. This task, however, has remained vital in the studies on plant interference, being extremely difficult to perform under field conditions. Therefore, the studies were conducted in the laboratory. To determine the activity of an allelopathic agent of the selected grass species, the density dependent phytotoxicity model was employed. The model is based on the fact that an increase of acceptor plants density evokes a decrease of their response to the allelopathic compounds, whereas the negative effects of the competition become more intense. A higher rate of acceptor plants growth accompanying their density increase in the given object does not agree with the competition rules and thus, it may imply an allelopathic background of the observed changes. In the presented studies, the allelopathic properties of grasses - donors were evaluated by studying the effect of two densities of the emerging seeds and two- and four weeks aged seedlings of <i>F. arundinacea</i>, <i>L. multiflorum</i>, <i>L. perenne</i> and <i>P. pratensis</i>. The tested species - acceptor <i>Ph. pratensis</i> was sown in the density of 10 and 20 seeds in a pan. The results revealed that the germination of acceptor seeds was differentiated depending on their density in the pan, and on the species, density and the age of the donor. Inhibition of <i>Ph. pratense</i> seed germination in objects with a lover density may prove allelopathic effects of the studied donor grasses.

Property and Expropriation: Themes and Variations in American Law

In recent years, property owners have increasingly clashed with regulators over what seem to be ever-expanding environmental laws. The ensuing conflicts have raised the stakes for understanding the ways in which American constitutional law protects owners from uncompensated of their property. This article argues that although the United States is certainly a very property-conscious nation, our property law has also co-existed with several quite different forms of uncompensated expropriations that have gone almost unnoticed in our property law. These contrasting types of expropriations can put in perspective the environmental regulations currently contested in cases. On the one extreme are a set of generally unnoticed expropriations that arise from claims-clearing doctrines and rules such as adverse possession, liability rules, and losses from the operation of the recording system. Despite the expropriative effects of these rules, a property regime could not exist without such housekeeping devices to clear title for continuing normal transactions; such rules suggest that certain forms of expropriation are actually a part of any functioning property regime. At the other extreme are the very dramatic expropriations that accompanied such major social upheavals as the American Revolution, the emancipation of slaves, and the settlement of the West at the expense of indigenous peoples. The article argues that these expropriations did not unsettle the bulk of property relations precisely because of their extraordinary character, particularly because they were perceived at most as losses suffered by outsiders to the ordinary community of property holders. The article argues that claims arise in an intermediate area between the housekeeping rules and the extraordinary measures. Changes in environmental laws, like the operation of housekeeping rules, are a part of any functioning property regime, in that they necessarily readjust the content of entitlements in face of increasing congestion and competition for environmental resources. But because of the uneven distribution of environmental regulatory change, these regulations also raise the prospect that some owners may be treated as outsiders. The article argues that takings doctrine is, thus, best understood not as an automatic defense of property rights, but rather as a legal compromise tactic to allow needed environmental transitions to occur, while reassuring owners that they are not being treated as outsiders to the community.

Light-dependent development of two competitive species (Rubus idaeus, Cytisus scoparius) colonizing gaps in temperate forest

Forest regeneration can be inhibited by competition for environmental resources (water, nutrients, light) between tree seedlings and some competitive species that are generally light-demanding species developing in gaps. The study’s aim was to quantify the development of two competitive species (Rubus idaeus and Cytisus scoparius) present in the chaine des Puys, France, relatively to light in gaps inside Picea abies stands. On 29 transects linking the stand to the gap centre (223 points), light intensity was measured (0–80% of relative light) and floristic measurements (cover and height of the different species) were done. Development of both competitive species is positively connected to light, with a bell-shaped curve with a maximum of 40–50% for R. idaeus and a quite constant increase to 80% (maximum of light recorded in the experimentation) for C. scoparius. These results are discussed relatively to understorey vegetation management in order to favour forest regeneration.

Weed Characteristics of the Labiatæ, with Special Reference to Allelopathy

ABSTRACT The Labiatae is a large family of diverse morphology and habit. Almost all members contain phytochemicals, volatile oils which contribute variously to commercial value, problems of toxicity and allelopathic activity. Weed status in the Labiatae depends primarily on competition for environmental resources and on characteristics dependent on the phytochemical content. In a number of genera, notably Salvia, allelopathic activity has been documented.

Effect of conspecific sex on aggression during pregnancy and lactation in golden hamsters

The effect of conspecific sex on maternal aggression in hamsters was determined by comparing the frequency of aggressive responses by dams continuously housed with either a virgin male or female cagemate during pregnancy and lactation. Dams easily established aggressive dominance over male cagemates soon after pairing, and their aggression was low thereafter for the duration of pregnancy and lactation. The aggression of dams with females, on the other hand, tended to fluctuate with highs during mid pregnancy and mid lactation and lows around birth. When dam aggression was low around birth, female cagemates frequently became aggressively dominant, and several dams lost their litters. The higher aggression of dams toward females than males is probably a reflection of greater intrasexual competition for environmental resources that includes pups.

The Population Biology of the Genus Viola: I. The Demography of Viola Sororia

(1) A census of all plants of Viola sororia 1-yr-old or older was carried out at regular intervals over an 8-yr period in a forest site in New England. Over a 2-yr period seedlings were similarly recorded, and each leaf and reproductive structure on twenty selected plants was marked and its fate recorded at weekly intervals. (2) Calculations were made of population flux, age distribution, survivorship and life expectancy of 1-yr-old or older plants, and of seedlings. (3) Fluctuation in population size was small compared to the number of individual plants gained and lost in the population. There was a remarkably constant annual death risk, superimposed upon a seasonal cycle, May-September being a period of greater mortality than the winter months when the plants were inactive. (4) The life expectancy of a 1-yr-old plant was over 10 yr. While seedlings and adult plants exhibited a Deevey type-III mortality curve, leaves had a Deevey type-I curve. (5) It was also established that seedling survival and production-probability are a function of plant size; the relationship is exponential in the case of seed production. It is suggested that individual plant size is regulated by competition for environmental resources.

Effects of Plant Population on Sole-crop Cassava in Sierra Leone

SUMMARYEffects of plant population on mean yield and yield components of 2-year sole cassava crops were studied on Njala upland soils of Sierra Leone in two experiments. Increasing plant population of multi-shoot Cocoa cassava over 7000/ha decreased all the parameters studied except top/root weight ratio, which increased. The observed effects were attributed to competition for environmental resources, since area of land/plant unit decreased as plant population increased. The relations between plant populations and yields of fresh root and cortex dry matter were asymptotic, indicating that the respective yields were products of the vegetative phase of cropping.

Ecological Analysis of the Cayman Island Avifauna

Ecological studies of the avifauna carried out over the past eight years in the three Cayman Islands of the Caribbean Sea revealed the presence of 151 species, mostly transients. Grand Cayman has 39 species of breeding birds (26 terrestrial), Little Cayman 29 (17 terrestrial), and Cayman Brac 30 (20 terrestrial). Each island also supports an additional 40 North American migrants in winter. Seasonal occurrences and relative abundances of birds are described, particularly for seven upland ecological formations in which the greatest breeding species diversities occur in logwood-thatch palm-red birch and limestone forests. In one sere, from pastureland through limestone forest, bird species diversity and total abundance increase with age of the community. High species diversity and density in the limestone forest are associated with some semblance of stratification but more so with a greater number of feeding niches. For the most part, the land birds breed in May and June at the onset of a rainy season. In the past 30-40 years, two bird species have become extinct on Grand Cayman, whereas two others have at least attempted colonization. The problems of inter- island distributional patterns are discussed in an attempt to explain the presence and absence of different species on different islands. No evidence was found to support the idea that the absence of one species on an island permitted another one on that same island to broaden its ecological niche; rather, the absence of woodpeckers, a tanager, flycatcher, dove, finch, and others on the two small islands strongly suggests vacant niches on those islands. Competition for environmental resources among the resident terrestrial birds was analyzed, especially between congeners and between species of similar ecologies. The four (or five) sympatric dove and pigeon species are separated chiefly by habitat and food differences; the two woodpeckers by food; four flycatchers by combinations of bill size, habitat, feeding height, and food type; the vireos by body size and bill size; and two Dendroica warblers by habitat and feeding height. With the exception of the scarce Barn Owl, no significant vertebrate predators on birds occur on these islands. The largely ornithophagous owl probably represents the greatest single biological control of the avifauna. Feeding ecologies, habitat distribution, and taxon cycles are specified, where known, for all the resident terrestrial species. Taxon cycles appear to be similar to those of other insular avifaunas, despite the absence of montane refugia on the Caymans. Species in Stage I (evidently the recent colonizers) are more common in early seral stages ("marginal habitats"), whereas the endemic subspecies (Stage IV) are more abundant in the mature forests. Because of the relatively large number of available habitats, Grand Cayman has 3.8 habitats per species, an exceptionally high figure when compared with mainland and other insular populations. This value plus other data indicate a remarkable generalization for the Cayman Island birds. The large number of wintering species appears to influence the residents very little because the wintering forms usually occupy feeding niches different from the residents. It is suggested that the winter is characterized by an abundant food supply (chiefly insects) that is incompletely exploited by the resident avifauna.

Competition for Environmental Resources by Component Characters1

Do component traits such as numbers of heads/area, seeds/head and weight/kernel compete for the same environmental resources? If so, how can this competition be measured objectively? The general case of two trait competition was examined. When each trait competes more severely with itself than with others, stable equilibria will be found. At some point in development it becomes more difficult for the plant to add, say, another head than to add more seeds per head. The conclusions regarding two competing traits were extended to three traits and applied to the components of yield in oats (Avena sativa L.). The findings seemed to Imply that stable equilibria existed for the three environments and the 36 lines tested. The analysis showed that the component traits shared a common pool of environmental resources but that also certain resources were trait specific. The practical aspects of these findings were discussed.