Impact of climate induced glacial melting on coastal marine systems in the Western Antarctic Peninsula region

IMCOAST is an international research program that features a multidisciplinary approach involving geo and biological sciences, field investigations, remote sensing and modeling and knowledge into the hydrographical and biological history of the marine coastal ecosystems of the Western Antarctic Peninsula region

Nitrogen Fertilization in \u3ci\u3ePaspalum dilatatum\u3c/i\u3e, Poir: Herbage Production, Nutritive Value and Structural Characteristics

It was studied the effect of nitrogen application on structural changes and quantity and quality characteristics of a Paspalum dilatatum Poir sward, under field conditions during two growing seasons. The nitrogen (N) rates were 0 and 440 kg ha-1 applied during the first year in split applications. The nitrogen fertilization increased leaf, stem and cumulative total dry matter yield, plant height, tiller density, cover ground and leaf crude protein yield

Legume Seedling Development in No Till Pasture Establishment

The objective of this study was to compare no-till and conventional seeding of pasture and their effects on legume establishment. The presence of residue cover reduced legume seedling establishment and weed population under no-till seeding. The reduction in establishment was associated with the physical impediment of the residue cover and the decay of seedling vigor when passing through that cover

Effect of Cattle Grazing on the Aridity Level of Humid Halomorphic Grass Communities of the Flooding Pampa (Argentina)

The Argentine Flooding Pampa is a large humid rangeland, severely deteriorated by cattle grazing, to the point of causing the local extinction of many native grasses and important alterations in ecosystem function. Among grassland communities exist those that vegetate halomorphic soils, highly degraded due continuous grazing by domestic herbivores causing soil denudation and increased aridity. An alternate grazing method, that controls the periodicity and moment of important rest periods followed by disturbance events, should increase cover and favor water availability. This succession process will determine more vigorous and abundant foraging species in the degraded communities. After six years of controlled grazing implementation, grasses show a higher water potential recuperation capacity than those grazed continuously. These results are related to an increase in soil cover, a better water status which decreases the aridity level and allows seedling establishment

Sustainability and range management in the Patagonian steppes

One hundred years of grazing by domestic herbivores hampered the ecological sustainability of the Patagonian steppes. We propose three management-related factors of such ecosystem degradation: (1) overestimation of carrying capacity of the rangelands, (2) inadequate distribution of animals in very large, heterogeneous paddocks, and (3) year-long continuous grazing. We suggest that these three management factors interact with the highly selective grazing habit of sheep generating a pattern of grazing heterogeneity at three scales: landscape, community, and population. Grazing differs in intensity among areas of the same paddock, among plant species, and even among individuals of the same species. As a consequence, the most palatable species within a patch are almost continuously subjected to a very high frequency of defoliation in the most preferred areas, which increases the mortality of the most preferred individuals of these forage species. We review the available ecological knowledge and range management technologies that may contribute to revert degradation. A quick assessment of both the availability and spatial heterogeneity of forage resources is now possible with the aid of remote sensing. Range assessment will allow to estimate the carrying capacity of each paddock, and separate different vegetation units. From information on the phenology of the different vegetation units it is possible to decide the timing of grazing and/or resting periods of single paddocks. Rotational grazing methods allow for a recovery of the most preferred species and for a reduction of the heterogeneity of defoliation at the three mentioned levels. Research efforts are needed to develop warning systems, improve the productivity and use efficiency of meadows, and design and evaluate grazing methods for the most arid areas of the region

State and Transition Model of Lowland Grassland in Flooding Pampa

Rainfall conditions are considered to be a major factor in determining vegetation structure in temperate grasslands with grazing playing a secondary role (Biondini et al., 1998; Sternberg et al., 2000). In order to analyse the relative importance of both factors on the lowland community of the Flooding Pampa we compared the responses of functional groups under both intermittent and continuous grazing regimes over a 3- year period of important inter seasonal rainfall variation. The results are presented in a state and transition model

Phosphorus Use Efficiency for Biomass Production of Legume Species

The objective of the experiment was to identify traits associated with the production of plant biomass, and hence with P utilization efficiency, when legume species were fertilized. Red clover (Trifolium pratense) and narrowleaf birdsfoot trefoil (Lotus tenuis) were compared in a greenhouse experiment using phosphorus deficient soils. Three plants grew in pots fertilized with 0, 2, 4, 8, 15, 20, 30 and 40 ppm in soil, in a randomized experimental design. Harvest was made at 60 days from the sowing date. Leaf areas, shoot and root biomass, and tissue phosphorus contents were measured. Results showed that changes in leaf area ratio in response to phosphorus fertilization influence nutrient use efficiency. Lotus tenuis showed a pronounced decreasing trend in these variables compared with Trifolium pratense (P\u3c 0.05)

Grassland Use and Plant Diversity in Grazed Ecosystems

Earth biomes are being deconstructed, through unprecedented rates of species disappearance or invasion (McCann 2000). This, added to the threat of global environmental change and changes in values of a developed society, caused that biodiversity became a topic that has captured the attention of the public as well as the scientific community. Such concern on the importance of biodiversity is based in four basic reasons clearly described by West (1993): (i) morality, that aims for the protection of species; (ii) aesthetics, as people desire to see and appreciate the living parts of nature; (iii) economics and, (iv) the array of “services” provided by the natural ecosystems. It is vital to know how badly is affecting ecosystem function human alarming rate of destroying the original diversity

Effects of Defoliation Frequency on Foraging Selective Behaviour in Pasture with Paspalum Dilatatum

The objective was to assess defoliation effects exerted by sheep grazing on a pasture composed by falaris and dallisgrass, at two phenological stages during spring and summer. A sown pasture of Phalaris aquatica and Paspalum dilatatum were grazed at two phenological stages: stage I (SI), with no more than 5% of reproductive tillers, and stage II (SII), with at least 70% of reproductive tillers. Tillers of both grass species were marked with plastic colour rings along two transects in each plot. Phenological stage of tillers, and the number, age and length of each leaf per tiller were registered. Tiller defoliation rates (TDR), Leaf defoliation rates (LDR) of young and old leaves and Defoliated tiller percent (DTP) were estimated for both species. The results obtained demonstrated that selective forage behaviour of grazing sheep showed the existence of mechanisms towards maximum forage consumption