Grasslands are areas where the vegetation is dominated by grasses (Poaceae) and other herbaceous (non-woody) plants (forbs). Plants of the sedge (Cyperacae) and rush (Juncaceae) families can also be frequent in grasslands. Grasslands occur naturally on all continents except Antarctica, and in many other areas they have replaced the natural vegetation due to human influence. In temperate latitudes, such as north-west Europe, grasslands are dominated by perennial species, whereas in warmer climates annual species form a greater component of the vegetation.
Grasslands can be found in most terrestrial climates. Grassland vegetation can vary in height from very short, as in chalk downland where the vegetation may be less than 30 cm high, to quite tall, as in the case of North American tallgrass prairie, South American grasslands and African savannah. Woody plants, shrubs or trees may occur on some grasslands — forming wooded, scrubby or semi-wooded grassland, such as the African savannahs or the Iberian dehesa. Such grasslands are sometimes referred to as wood-pasture or Savannah woodland. Grasslands cover nearly fifty percent of the land surface of the continent of Africa.
This new book gathers new and important research from around the world in this field.
Expert Commentaries - It is often perceived that the management practices associated with grass based farming systems are less damaging to biodiversity than are those associated with arable farming systems. Therefore, much scientific attention has been dedicated to the rejuvenation and conservation of field margins within arable systems. However, modern agricultural practices such as sward reseeding, fertilisation and silage cutting are known to be detrimental to the botanical and invertebrate faunal communities associated with grasslands. Despite this, the conservation value of field margins within agriculturally improved grasslands has largely been overlooked by scientists and policy makers to date, notwithstanding that agricultural grassland accounts for a large proportion of agricultural land in many countries, e.g., 79% in Ireland and 67% in the UK.
In this commentary, the authors review the ecological research which has focused on the conservation of field margins and in particular, those within grass-based farming systems. They identify the potential benefits for biodiversity and the ecological services facilitated through the retention/rejuvenation/reintroduction of these habitats within intensively managed grasslands. They also discuss some methods for the rejuvenation and/or establishment of a diverse field margin flora, subsequent management and the challenges associated with each option.
In order to provide reliable projections of future CO2 emissions from soils, due to global warming, it is important to consider the global distribution of soil BC. Through an initial assessment of the World Soil Archive (http://library.wur.nl/isric/) the authors demonstrate the variability and trends of global soil BC distribution between different climates and soil types and discuss the implications of this chemically recalcitrant form of C on the global C cycle. By doing this, the authors also demonstrate that current methods exist to routinely analyse BC and in the future to develop a global BC map.
Short Communications - Vegetative production is defined as a coupling between crop plant production as the primary product and livestock production as the endproduct in farmlands. The primary product is forage rather than grains that are often the traditional agricultural endproduct. Accordingly, vegetative production requirements for climatic resources are different from traditional grain production. In the first short communication, climatic resources were compared between the north and south China. Traditional (grain) and vegetative (shoot) productions have many production aspects in common and also have differences in physiology, cost inputs, utilization efficiency of solar energy, and vegetative and grain yields. Advantages of vegetative production compared to traditional grain production are presented. Based on the differences of the requirements of irradiance between vegetative and traditional grain productions, enhanced development of vegetative production was proposed through utilization of existing grasslands and winter fallow croplands in south China. This new strategy promises to reduce runoff and loss of topsoil, decrease dust clouds, and restore a good portion of damaged ecosystems in China.
In the second short communication, the authors discuss a central issue in conservation biology and nature management: whether or not characteristic species of a given habitat type could be preserved by fragmented habitat patches or not. The classical theory of island biogeography predicts that the number of species supported by an island increases with the area of the island. However, there is a significant difference between real and habitat islands. In real islands, the surrounding habitat (ocean, sea, lake, river, etc.) is usually inhospitable to organisms occurring on islands. In the case of habitat islands, the bordering habitat (the matrix) is usually less hostile. Consequently, species richness of real islands is not influenced notably by the surrounding habitat. This difference is increasingly emphasized when studying the predictions of island biogeography theory on habitat islands. A clear distinction should be drawn between specialist species that truly perceive the habitat patches as islands and are unable to survive in the surrounding matrix, and those species that occur in both the habitat patch and the matrix (generalist species).
In this case study, the authors demonstrated that depending on the ratio of specialist and generalist species in an assemblage, the species-area relationship may be positive or negative. Ground beetles (Coleoptera: Carabidae) of sandy grassland patches were studied in Eastern Hungary (Central Europe). The total number of ground beetle species correlated negatively with grassland area. Based on this result, one can draw the (seriously false) conclusion that it is sufficient to conserve small patches because they support most species. This negative relationship was due to the increasing ratio of generalist species with decreasing patch size. Analyzing the habitat specialist species (open-habitat species associated with sandy soils), the significant negative relationship turned over, and became significantly positive; i.e., the ratio of habitat specialist species increased with patch size, as predicted by the theory of island biogeography.
In the third short communication, the authors discuss a solar chimney power generating technology as a solar thermal technology on a large scale which combines three parts: a collector, a high chimney (reinforced concrete chimney or floating chimney that can stretch up to several thousand meters), and turbines installed at the chimney base. The best locations of these systems are vast desert regions with high solar insolation and large daily range of temperature. As reported by Zhou et al. in 2008, special microclimate conditions will result around the solar power generation belts consisting of many commercial solar chimney power plants. Resulting rainfalls will support the growth of different types and quantitities of plants, including herbs, shrubs, and even trees. This will promote restoration of desert land and even create fertile soil and modify the local ecology. Produced plants can be used for biofuel. Furthermore, vegetables can be planted in the periphery of the collector acting as a green house and as a result benefit agricultural production. Other plants can then be used as a source of power as fuelwood or biomass to produce biogas. Many ecological and agricultural benefits are eminent in this respect.
Chapter 1 - The benefits of multi-paddock rotational grazing on commercial livestock enterprises have been evident for many years in many countries. Despite these observations and the results of numerous studies of planned grazing deferment before the mid-1980s that show benefit to species composition, most recent rangelands grazing studies suggest that rotational grazing benefits neither vegetation nor animal production relative to continuous grazing. Detailed comparisons of research methods and practical experiences of successful practitioners of multi-paddock grazing systems identify a number of areas that explain why such different perceptions have arisen. Consistent with producer experience, published data from small paddock trials on both temporal and spatial aspects of grazing management indicates the potential for significantly higher production under multi-paddock rotational grazing relative to continuous grazing and conservative stocking.
While research findings often suggest multi-paddock grazing management is not superior to continuous grazing, researchers have not managed trials to answer practical questions such as: how good is this management option, where is it successful, and what does it take to make it work as well as possible? In contrast, successful ranchers manage strategically to achieve the best possible profitability and ecosystem health. They use basic knowledge of plant physiology and ecology generated by research within an adaptive, goal-oriented management approach to successfully implement planned grazing management.
Published research and experience from ranchers have indicated that the following management factors are the keys to achieving desired goals: (1) planned grazing and financial planning to reduce costs, improve work efficiency and enhance profitability and environmental goals; (2) adjusting animal numbers or having a buffer area available so that animal numbers match forage availability in wet and dry years; (3) grazing grasses and forbs moderately and for short periods during the growing season to allow adequate recovery; (4) timing grazing to mitigate detrimental effects of defoliation at critical points in the life cycle of preferred species inter- and intra-annually; (5) where significant regrowth is likely, grazing the area again before the forage has matured too much; (6) using fire to smudge patch-grazing imprints and manage livestock distribution; and (7) using multiple livestock species. In all these areas, management is the key to success.
Many researchers have failed to sufficiently account for these management factors, either in their treatment applications or in the evaluation of their results. To define the potential impact, researchers must quantify the management strategies for best achieving whole-ranch business and ecosystem results under different grazing management. Conducting research on ranches that have been successfully managed with planned multi-paddock grazing for many years, together with systems-level simulation modeling, offer complementary approaches to traditional small-paddock field research. These methods are particularly applicable where logistics preclude field experimentation, or when assessing impact over decadal time frames. This chapter discusses these points, suggests areas of research that may explain differences in perception among land managers and researchers, and provides information to achieve the full potential of planned multi-paddock grazing management.
Chapter 2 - Desertification models predict that arid grasslands exist in one of two stable states: grassland or desertified shrubland. This prediction is derived from an assumed positive relationship between grass cover and water infiltration rate: once grass cover is reduced, water infiltration rates are insufficient to support perennial grass. These models assume that other factors known to affect water infiltration rate are unimportant. While this alternate stable state view is widely accepted and suggests that restoration of desertified grasslands will be difficult, there have been four recent reports of the reversal of desertification (significant increases in the abundance of perennial grasses) following long-term livestock removal. At one site, recovery of perennial grass inside a long-term grazing exclosure was associated with increased water infiltration rates due to release from soil compaction. To assess the generality of this finding, the author examined water infiltration rates inside and outside five other long-term livestock exclosure sites in southwestern North America that differ in degree of desertification and time since livestock removal. At each site, water infiltration rates were significantly higher inside compared to outside the grazing fence. The relative difference in water infiltration rate across the sites increased with time since livestock removal at a rate of approximately 1.7% per year. These data show that increased water infiltration rate following livestock removal appears to be a general phenomenon in arid grassland systems. In addition, they suggest that the effect of livestock on water infiltration rates should be included in desertification models to better understand the dynamics of vegetation in these systems. Finally, this work suggests that restoration of desertified grasslands may be possible given sufficient time to allow changes in soil properties including release from soil compaction and the concomitant increases in water infiltration rate that follow.
Chapter 3 - At the times of America's discovery in 1492 the temperate part of South America was covered by grasslands. This area includes today Central and Northeastern parts of Argentina, a great deal of Uruguay and Southern Brazil (Figure 1) (Soriano et al., 1991). Among specific features, those grasslands had a unique characteristic: they were developed without high grazing pressures because the region lacked of large herbivores. This differs from the situation found in equivalent African and North American grasslands (Mc Naughton et al., 1988; Sala et al., 1986). The floristic composition of these grasslands varies in accordance with the regional climatic gradients and the local substrate heterogeneity (León et al., 1979; Burkart et al., 1990; Perelman et al., 2001; Soriano et al., 1991). Since European colonization, this vegetation has been progressively modified by the introduction of domestic cattle and the appearance of annual crops, pastures and forestation. These disturbances have led to the invasion and naturalization of several exotic vegetal species, provoking changes in the distribution of the native species (Ghersa and León, 1999) and alterations in the structure and functioning of the vegetal communities (Sala et al., 1986; Rusch and Oesterheld, 1997). Nowadays, only semi-natural grasslands remain in some locations within the region- They are located where the agricultural possibilities of the lands are seriously constrained (Ghersa and
León, 1999). This typically occurs in the so called Flooding Pampa. Two main reasons affect agricultural development in this subregion: the occurrence of frequent ponding and/or floods alternating with summer drought cycles, and the prevalence of halo-hydromorphic soils (León et al., 1975; Batista et al., 1988; Lavado and Taboada, 1988).
Chapter 4 - Here the authors report the main trends observed in the soil seed bank of some species-rich pastures located near Vic (NE Spain), evaluating the relationship between soil seed bank and standing vegetation in two contrasting communities (xerophilous pasture and mesoxerophilous grassland), and the potential role of the soil bank in community regeneration. The authors analyzed 140 soil samples via germination tests and direct observation. The total seed pool (including soil seed bank and standing vegetation) was characterized in terms of morpho-functional traits.
The soil seed content was high and showed strong seasonal variation. The authors found 12,178.8 to 785.7 seeds m-2 in the germination tests, and 6,909.1 to 4,882.5 seeds m-2 through direct observation. The shallow soil horizon contained much higher densities and species richness than the deep horizon, and higher relative frequencies of elongated or appended seeds. In both communities, 35-45% of the species richness in the soil seed bank corresponded to opportunists, which were rarely found in the established vegetation. In contrast, half of the taxa in the aboveground xerophilous pasture and two-thirds in the mesoxerophilous grassland were not found in the soil bank.
The persistent seeds in the soil bank belonged to a few taxa, mainly not found or rare in the established vegetation. Most of the main species of this vegetation, such as dominant grasses and abundant sub-shrubs, were poorly represented in the soil seed bank. These trends indicate the limited role of this bank in the regeneration of the communities studied, particularly in the mesoxerophilous grassland. The changes in land use occurred during the last half century have strongly increased the fragmentation of semi-natural plant communities, and impair the conservation of plant diversity of this species-rich landscape.
Chapter 5 - During the last century changing patterns of land use in the UK have led to the large scale loss and degradation of species-rich chalk grasslands, a habitat of conservation importance across Europe. In particular, the conversion of chalk grasslands into arable land has represented a major threat to this habitat type. The re-creation of chalk grasslands on exarable land therefore has the potential to both increase the area of this threatened habitat, and to provide links between existing remnant fragments. The authors present a four year study investigating the effects of three different methods of introducing plant species during grassland re-creation: 1) a simple grass seed mix, intended to suppress the establishment of pernicious weeds; 2) spreading of hay; and 3) sowing of brush harvested seeds. The latter two methods introduce local provenance seeds collected from species-rich chalk grassland. Using a replicated block design, the authors investigate the efficacy of these management practices in promoting the re-creation of both plant and phytophagous beetle assemblages. They compare re-creation success relative to a target chalk grassland and contrast differences in the responses between these two trophic levels. The introduction of local provenance seeds by hay spreading and brush harvesting is shown to be beneficial during re-creation. However, if used in combination with simple grass-only seed mixtures the establishment of some chalk grassland species may be reduced. The authors discuss the relevance of these findings for the re-creation of plant and phytophagous beetle assemblages of species-rich grasslands on exarable land. They also consider the implications of differences in establishment rates between these two taxa for the long term success of habitat creation.
Chapter 6 - Over recent decades, vegetation ecology has increasingly become a predictive functional science that is more oriented towards the physiological properties of the organism and less concerned about the presence or absence of particular organisms. The mechanisms underlying ecosystem functioning result in typical plant community structures and floristic compositions that are frequently seen also in heavily polluted locations. Mathematical models provide useful tools when trying to decipher the links between biodiversity, productivity, stability, decomposition, nutrient acquisition and resilience in ecosystems, with important findings for the direction of natural resource management and applications in remediation technologies. Phytoremediation is the use of vegetation for the in-situ treatment of contaminated soils, sediments and water. It is characterized by lower capital inputs and lower costs, as compared to conventional methods. It is best applied at sites with shallow contaminations of metal, nutrient or organic pollutants, that are amenable to one of its applications: rhizofiltration, rhizosphere bioremediation, phytotransformation, phytostabilisation, phytoextraction and, in extreme cases, phytomining. Assigning plant species to functional groups on the basis of their physical and/or ecophysiological characteristics is one of the strategies applied when trying to explain and predict the interactions of plants with their environment. It has become clear however, that no single functional classification is applicable to all situations. Metallophytes, in particular, have received special attention in phytoremediation studies, primarily because of the mechanisms that enable them to resist metal concentrations that are toxic to most plant species, and thus to survive and dominate areas with natural or anthropogenic induced mineralization. The focus of the chapter is on the recent advances in vegetation ecology and their consequences for contemporary phytoremedial applications.
Chapter 7 - In different regions of southern Brazil, often a mosaic of grassland and forest is found, but little is known how these vegetation pattern has been formed. Palaeoecological background information is needed for management and conservation of the highly diverse mosaic of forest and grassland in southern Brazil. Questions on the origin of grasslands, its development, dynamic and stability, its response to environmental change such as climate, and the role of human impact, are essential. Further questions on its natural stage of vegetation or its alteration by pre- and post-Columbian anthropogenic activity are also important. To answer these questions, palaeoecological and palaeoenvironmental data based on pollen and charcoal analysis of radiocarbon dated sedimentary archives from southern Brazil are used to provide an insight into past vegetation changes that allow us to improve our understanding of the modern vegetation and to develop conservation and management strategies for the strongly affected grassland ecosystems in southern Brazil.
Chapter 8 - Agricultural activities are significant producers of nitrous oxide (N2O) emission to the atmosphere (Johnson et al., 2007; Ugalde et al., 2007). That is, about 58% of total anthropogenic N2O emissions are caused by agriculture (IPCC, 2007). The main cause of agricultural increases in N2O is the application of N fertilizers and animal manures. Nitrous oxide is a long-lived greenhouse gas in the atmosphere with 296 times the global warming potential of CO2. Denitrification is credited as the primary producer of N2O (Johnson et al., 2005), which is generally favoured in poorly aerated soils with high NO3- concentrations (V an Groeningen et al., 2005). Currently, about 32% of the agricultural land in the EU is used for grassland production (Eurostat, 2005). The response of grassland to fertilizer N is greater than that of most other crops due both to its long growing season and to being harvested as vegetative growth (Whitehead, 1995). In the Basque Country, around 36% of agricultural land is occupied by grassland, and there is a high risk of N2O losses by denitrification due to high rainfall, typically in excess of 1000 mmyr-1, and warm temperatures, especially in spring and autumn when fertilizer is applied (Estavillo et al., 1994). Besides, the current dairying model is still developing towards an intensified dairy production system, resulting in increases in generation of animal manure, which may be also a significant source of harmful nutrient emissions into the environment if handled improperly. Also, the mountainous orography characteristic of the area together with the historically parcelled rural soil distribution and the current high industrial pressure has dramatically increased rural soil prices, which does not contribute to enhance farmland availability. Efficient use of nutrients is one of the major keys of sustainable agricultural production systems because inefficient nutrient use not only results in excessive and potentially harmful losses to the environment, it also negatively affects economic performance of production systems (Oenema and Pietrzak 2002).
This review focuses on N2O emission especially in the Basque Country as related to grassland soil, considering the effect of management and mitigation options.
Chapter 9 - The stages of grassland development on Kunashir and Iturup Islands (Southern Kuril Islands) and Lesser Kuril Ridge are reconstructed based on pollen analysis and radiocarbon dating of soil profiles. There are anthropogenic grasslands and meadows in wind shadows formed during cooling events in Late Holocene; these formations have been relatively stable during last 1500-2000 years. Grasslands on small islands in the south of the Lesser Kuril Ridge have existed last 4000-6000. Floristic components began to change in the Late Pleistocene. Grassland soils have multiple profiles. Grasslands have various floristic compositions. Herbaceously rich meadows are located on terraces and divides, with Sasa on some terrace surfaces and slopes. Shrub-grass associations developed on supersaturated substratum; herb-graminoid - on well drained areas. Grass associations typical for swamp accumulative lowlands are developed on low coastal plains.
The lithogenic component of landscapes is most dynamic on the islands and it quickly responds to climatic changes and changes in sea level. For example, substratum renewal has largely been a response to aeolian processes during small amplitude regressions in the Middle and Late Holocene. Sand buildup and the addition of volcanic ash with varied chemical compositions have changed water and mechanical soil characteristics that greatly influenced grass associations. Supersaturated sedge and sedge-herb meadows even on low isthmuses shifted to herb-graminoid and the role of xerophilous species increased.
Chapter 10 - Nitrous oxide (N2O) emissions from grazed pasture soils represent a significant source of atmospheric N2O. Nitrous oxide is produced by transformations of nitrogen from cattle excrements, urine and fertilizers entering the soil. Specific conditions are necessary for emissions of N2O and these emissions are both spatially and temporally highly variable. Spatial, and in some extent temporal variability, is due to the complex effect of nitrogen input, pasture management and environmental conditions (e.g., aeration and water status, pore space and pore size distribution, available carbon and mineral nutrients concentration, pH and other soil chemical properties, as well as microbial communities abundance and diversity) on N2O emissions and all this makes estimation of emissions very difficult. Several types of environments or events characterized by potentially high N2O production and emissions (=emission hot spots) can be distinguished in the livestock farming system. These include camping areas, drinking sites, feedlots, shade areas, footpaths, dung and urine patches (where combined effects of nutrients in urine, dung and compaction occur resulting in creating conditions for high nitrification and denitrification rates). Here, the author proposes overwintering areas, that is pasture sites where cattle is located in high stock densities for a relatively long period during winter season (where severe damage of plant cover is common and the effects are typical for the above camping areas other hot spots are even reinforced as another type of hot spots for N2O emissions. Due to overgrazing effect, damage of vegetation and high stock density, as well as high N-inputs in excrements and lower utilization of deposited N by plants in a cold period, cattle overwintering areas appear to have a large potential for accelerated microbial N transformations and thus gaseous losses. This contribution examines various aspects related to the production of N2O and its emission from the soil of cattle-grazed pasture sites, aiming to identify its major sources as well as environmental soil conditions favourable for N2O production (=emission hot spots), as well as to summarize mitigation strategies for N2O emissions. In particular, it is focused on the cattle overwintering areas, representing specific and often significant emission hot spots. Relevant measures to decrease N2O fluxes from the grazed grasslands are presented. However, practical options to decrease N2O emissions seems to be rather limited due to a number of reasons, including a limited knowledge on intrinsic mechanisms regulating N2O production in the pasture soils.
In: Grasslands: Ecology, Management and Restoration Editor: Hans G. Schröder
Expert Commentary A
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