Techniques for measuring forage intake of grazing animals
The knowledge of forage intake by grazing ruminants is very important for ecological, economical and management reasons. Eventhough, intake measurements in grazing studies has been the subject of extensive research for many years the procedures used still remain laborious, expensive, time consuming with low precession and accuracy. In this paper several methods such as total fecal collection, markers (Cr2O3 and nalkanes) and fecal nitrogen index which are commonly used for intake determination are discussed.
Diet selection of ruminants as a useful management tool in rangelands
Ruminants foraging on rangelands select their diets from an array of plants that vary in nutrients and toxins. Their senses of taste, smell, and sight help them to select an appropriate diet, which meets nutritional needs. Postingestive feedback adjusts a forage’ s value commensurate with its utility to the animal enabling survival when the grazing environment and animal’s nutritional needs are changing. Animals acquire preference for plant species that cause positive postingestive feedback (these species are usually correlated with adequate nutritional constituents); on the contrary they acquire aversion for plant species that cause negative postingestive feedback (these species are correlated with nutrient deficiencies or excesses and toxicities). In other words, what makes a forage preferable or not is not its taste but its nutritional benefits or deficits received from forage ingestion, which are sensed by animals through feedback and linked with a forage’s taste. The senses of smell and sight help animals to seek foods that cause positive feedback and avoid foods that cause negative feedback. Finally, in this article the implications of diet selection for rangeland management are discussed.
Liming and N, P addition in a grassland dominated by Cyperaceae species in the plateau of Ioannina
The aim of this work was to examine how the liming and the soil enrichment with N and P influence the above-ground vegetation and the species composition in grassland areas dominated by species of Cyperaceae and having low soil pH values. In a grassland, characterised by low soil pH and the dominance of the Cyperaceae species Carex hirta and Cyperus longus, the effects of liming (0 and 800 g/m2, applied once at the beginning of the experiment) and the N (0 and 15 g/m2 per year) and P (0 and 4.5 g/m2 per year) enrichment were examined on vegetation production for four years. Liming did not affect the total aboveground vegetation nor the species composition, although it increased the soil pH. Addition of N increased the total aboveground vegetation 13% (averaged means over the four years). This increase was due to the significant increases at the first three years of the Cyperaceae species Carex hirta and of the annual grasses Alopecurus urticulatus and Bromus hordeaceus and decreased the other forbs. Addition of P affected significantly by increasing only the total legumes. Between years, the total above-ground vegetation was the highest in 1992 because of the relatively high temperatures of the preceding winter and the uniformly distributed rainfall during the spring. Addition of N affected significantly the species composition by progressively increasing the relative abundance of the annual grass Alopecurus urticulatus and the forb Galium aparine and progressively decreasing that of Cyperus longus and of forb Plantago lanceolata. The dominant species Carex hirta was progressively increased but the forb Rorippa sylvestris was decreased.
Competition between Dactylis glomerata L. and Taraxacum officinale L in a controlled environment
In meadows and pastures the presence of many kinds of species with different biological cycles makes the competition between plants an extremely complicated phenomenon. The experimentation with plants of different patterns of growth under controlled conditions could offer useful information for the understanding of the phenomenon of competition. For this purpose there were chosen plants with distinct morphological differences, i.e. Dactylis glomerata L. (cocksfoot) and Taraxacum officinale L. (dandelion). The experiment took place under constant environmental conditions (climate and nutrition through firtirrigation with solution of micro- and macro- elements). The following treatments of competition were applied: shoot, root / shoot, root and that of monoculture of both species. Some morphological characteristics of the plants were measured (height, length of longest leaf, leaf area, tillers, root depth and dry weight of shoot, leaves and root). The last (fourth) observation was the most characteristic. According to this observation, it is concluded that cocksfoot was dominant in most cases of competition. The only exception where dandelion competed successfully cocksfoot was the shoot treatment. Dandelion achieved the best values in most cases as a monoculture. So, the main finding for dandelion was that this species can not compete with cocksfoot.
Leaf construction cost of the most abundant species in an upland grassland of Northern Greece
Leaf construction cost (g glucose/g dry biomass) is considered to be a major determinant of species success in various habitats. The concentration of nitrogen (%N), carbon (%C) and mineral content in plant tissues were used to provide a measure of leaf construction cost. Five leaf samplings of the most abundant plant species (Poa pratensis, Lolium perenne, Festuca valida, Trifolium repens, Taraxacum officinale, Plantago lanceolata, Achillea millefolium) were conducted during the growing season of 1997, in an upland grassland which is dominated by C3 species. Furthermore, soil samplings were performed in parallel to leaf samplings, in order soil inorganic nitrogen is determined. Carbon and nitrogen concentrations and ash content were measured in leaf samples and these measurements were used for leaf construction cost determination. Trifolium repens had the highest nitrogen concentration, grasses had the highest carbon concentration while the highest ash content was observed in the forb species. The highest leaf construction cost was calculated for the legume Trifolium repens which was followed by the grasses Festuca valida and Poa pratensis. Forbs (Taraxacum officinale, Plantago lanceolata, Achillea millefolium) had the “cheapest” leaves since it had the lowest leaf construction cost. A positive correlation between leaf construction cost and soil inorganic nitrogen was evident for grasses (Poa pratensis, Lolium perenne, Festuca valida).
