Biodiversity controls on nutrient cycling and soil processes

Natural communities have been selected to withstand a wide range of environmental perturbations such as wetting-up after the dry season, intense rain storms, tree throw, synchronous litter falls and outbreaks of defoliating insects. With the exceptions of extreme events such as hurricanes and wildfires, the effects of these events are buffered by the system and have negligible long-term consequences for the sustainable production of the system. In contrast, high-intensity short-rotation...

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0.3-0.5 O.S-O.7 0.7-0.9 0.9-1 1 1.1-1 3 1.3-1 5 1.5 1 7 Land equivalent ratio (Land area of sole crop per land area ol intercropping at same yield) Figure 11.4 The relative yield efficiency of intercrops (two-species mixtures) as compared with the two crops grown separately (from Trenbath 1976) 0.3-0.5 O.S-O.7 0.7-0.9 0.9-1 1 1.1-1 3 1.3-1 5 1.5 1 7 Land equivalent ratio (Land area of sole crop per land area ol intercropping at same yield) Figure 11.4 The relative yield efficiency of intercrops...

Conceptual Model

The relationship between biodiversity and ecosystem function in grasslands can be described by two general hypotheses (Lawton and Brown 1993) the redundant species hypothesis which states that species richness is irrelevant for ecosystem function (under existing conditions'), and the alternative hypothesis that each and every species plays a unique role in the functioning of the ecosystem. Experimental evidence does not support either of these extreme hypotheses. Most ecologists prefer a model...

Human Impacts On Biodiversity Of The Open Ocean

Biodiversity and ecosystem processes are intertwined in a tangled web with complex feedback loops. Changes in one aspect of biodiversity, loss of a top predator for example, will affect some aspect of the food web, which can then lead to changes in other biodiversity and ecosystem processes. Figure 16.5 summarizes the idea that human impacts interact to change biodiversity in Figure 16.5 A conceptual relationship between anthropogenic impact on biodiversity and subsequent effect on ecosystem...

The Global Distribution Of Grassland Biodiversity

The most thorough compendium of comparative data on grassland biodiversity comes from the World Conservation Monitoring Centre (WCMC) (1992), which assembled data from a wide variety of sources to achieve preliminary, working comparisons both of grasslands on different continents and grasslands with other types of ecosystems, WCMC (1992) estimated that only 5 of the world's bird species and 6 of the mammal species were primarily grassland-adapted, since many of the species with abundance...

Energy flow

Energy captured by photosynthesis flows through ecosystems through many pathways, whose variety is correlated with the species richness of the system. Species richness could influence the rates and quantities of energy flowing through the system in a number of ways. Primary productivity and biomass accumulation Primary productivity of tropical forests is apparently affected by plant species richness only at levels far below those that characterize most mainland tropical forests (Vitousek and...

Functional Groups

The number of species in all ecological communities, especially tropical ones, greatly exceeds the number of key ecological processes. We refer to the species that participate in a particular process as a functional group (Vitousek and Hooper 1993). Functional groups are inevitably fuzzy assemblages, but they constitute a useful operational basis for identifying groups of species with potentially similar effects on ecosystem-level processes. If the loss of a species results in a large effect on...

References

Ajtay, G.L., Ketner, P. and Duvineaud, P. (1979) Terrestrial primary production and phytomass. In Bolin. B Degens, E.T., Kempe, S. attd Ketner, P. (Eds)-. The Global Carbon Cycle. Wiley, New York. Baruch, Z. (1986) Comparative ecophysiology of native and introduced grasses in a neotropical savanna. In Joss, P.J., Lynch, P.W. and Williams, O.B. (Eds) Range-lands A Resource under Siege. Cambridge University Press, Cambridge, pp. 449 450. Baruch, Z. and Fernandez, D. (1993) Water relations of...

The Global Biodiversity Assessment

The SCOPE program was expanded somewhat following initiation by the United Nations Environmental Programme (UNEP) of a Global Biodiversity Assessment (GBA). In mid-1993, a group met in Trondheim, Norway, to prepare an outline of such an assessment. It was decided that the SCOPE effort (as well as other DIVERS IT AS components) would be incorporated into the GBA, as noted in the publications below. The GBA is intended to provide the scientific underpinnings for the Biodiversity Convention. The...

Scope 1 Scope 2 Scope

Global Environment Monitoring, 1971, 68 pp (out of print) Man-Made Lakes as Modified Ecosystems, 1972, 76 pp (out of print) Global Environmental Monitoring Systems (GEMS) Action Plan for Phase I, 1973, 132 pp (out of print) Environmental Sciences in Developing Countries, 1974, 72 pp (out of print) Environmental and Development, proceedings of SCOPE UNEP Symposium on Environmental Sciences in Developing Countries, Nairobi, February 11-23, 1974, 418 pp (out of print) SCOPE 7 SCOPE 8 SCOPE 9 SCOPE...

Mte Research And The Global Forum

Critics sometimes argue that funding of, and attention to, MTE research is disproportionate because they occupy only about 2 of the Earth's land surface according to Koppen Cs climate zones (M ller 1982), or less than 1 using the more narrowly circumscribed definition of Aschmann (1973). This supposes that importance is a linear function of area, which implies that the collective GNP of all MTEs is approximately 4 that of the USA (Europa World Yearbook 1994). MTEs, however, have some...

Humaninduced Changes And Their Effects On Biodiversity And Ecosystem Function

Climate warming The anticipated warming from atmospheric loadings of radiatively active gasses is probably the greatest threat to the boreal region worldwide. Although the global circulation models disagree on the details of the extent of warming and drying, all agree that the greatest warming will take place in high-latitude regions, and most agree that mid-continent areas will become drier while maritime areas will become wetter (Schlesinger and Mitchell 1985). Climate warming will affect the...

The Scope Program

The SCOPE program consisted of a series of activities between 1991 and 1994, culminating in an overall synthesis meeting at Asilomar, California, in 1994. The program was launched in October 1991 with a meeting on background issues held in Bayreuth, Germany. This meeting brought together ecologists and population biologists, both directed toward evaluating the consequences of human-driven disruption of natural systems. In particular, there was an examination of the degree of redundancy within...

Maintaining Biodiversity Of Freshwaters

From an ecosystem perspective, the reason to preserve biodiversity is to preserve options for the future. The environment is certain to change because of natural fluctuations in the physical forcing of the biosphere and large-scale anthropogenic effects. We cannot predict which building blocks will be essentia for maintaining ecosystem or landscape processes in future environments. It is prudent to preserve taxa that may be crucial for ecosystem processes under new conditions. At a large scale,...

Learning and adapting to surprise

The ecological changes likely to occur in Chilean lakes and the management actions to be recommended are consistent with experience in North Temperate lakes. This convergence may indicate global patterns of ecosystem change which suggest that general guidelines for management can be derived, and that we do not need to study each system as if it was unique. It seems likely that nutrient enrichment and salmonid introductions will cause Chilean lakes to resemble many mesotrophic lakes around the...

Nekton Biodiversity And Mangrove Food Webs

Nekton (free-swimming organisms) food webs represent faunal guilds that utilize mangrove habitats for food and protection at different stages of their life cycle. Most of these organisms are migratory (while there may be some residents), and the ephemeral nature of the periods when these organisms utilize mangrove habitats contributes to the poor understanding of their ecology. Robertson and Blaber (1992) reviewed the results of four mangrove fish community studies in northern Australia where...

Stability And Species Richness

Discussions of the degree and causes of stability are frequently hampered by vagueness and inconsistency about what is meant by stability (Orians 1975). Stability may simply mean constancy, that is a low level of variation in some measurable property of the system. Stability may also refer to the resistance of the system to alteration by external perturbations (inertia), its speed of return to initial conditions following a perturbation (elasticity or resilience), the domain over which it...

Freshwater Ecosystems Linkages of Complexity and Processes

PERSSON, M. POWER AND D. SOTO 12.1 INTRODUCTION 12.1.1 Uses of Freshwaters Freshwater ecosystems are indispensable for life. Unlike some resources, there is no substitute for water. Its availability influences the distribution of Earth's major biomcs and the productivity of agriculture. Historically, fresh-waters have been a magnet for human settlement. Important human uses of freshwaters include drinking, fishing, industry, irrigation, recreation and transportation...

Conclusion biodiversity and ecosystem function from genes to regions

To conclude, we have identified how biodiversity, from genes to regions, may alfect ecosystem function in coral reefs. At a single reef, diversity in the life-history characteristics of reef biota, both within and among species, provides the basis for occupancy and survival in the broad range of environments that the reef provides. The diversity of a reefs zones is essential to the maintenance and accretion of the overall structure itself, and of its protein resources. Each zone's...

Mangrove Faunal Guilds And Ecosystem Function

Animal species co-occurring in mangrove forests can be separated into guilds characterized by the utilization of available resources (Ray and McCormick 1992). Fauna) guilds described in this section are basically resident species that exploit the habitat with different intensity in space and time, in contrast to the nekton guilds discussed below (Section 13.6). The utilization and exploitation of the mangrove habitat by faunal guilds, both resident and migratory, can contribute to the structure...

Facilitators as links between humans biodiversity and ecosystem function

Three case studies illustrate reef turn-off caused by population fluctuations in echinoderm facilitator species. In the first, the turn-off appears to be rapidly reversible without human intervention in human time scales in the latter two, the situation appears to be irreversible, or at least much slower than expected. Crown-of-thorns starfish. In the 1960s and 1980s, populations of the crown-of-thorns starfish Acanthaster planci, for reasons unknown, increased by several orders of magnitude...

Water quality and land runoff effects on biodiversity and ecosystem function

The water flowing onto a coral reef acts as a transport medium for materials (organic matter, nutrients, sediments, propagules - sec Section 15.3) which are beneficial when delivered at appropriate concentrations and frequencies, but may be deleterious when delivered in excess. Mechanisms for nutrient impacts on coral reefs Four mechanisms for nutrient impact on reefs are rccognised, although cause and effect have been difficult to establish unequivocally (Bell 1992). Should they reach a reef...

Effect Of Species Diversity On Ecosystem Function

We now explore how changes in species diversity affect ecosystem function in order to test our null hypothesis. For this purpose we make use of natural and unplanned human experiments involving the addition and or removal of plant and animal species from natural savanna ecosystems. 8.4.1 Invasion of South American and Australian savannas by African Several species of African grasses (such as Hypharrenia rufa, Melinis minuli-flora and Panicum maximum) have becomc naturalized in the South...

Savanna Structure And Function

Litterfall And Decomposition Plant

Ecosystem function can be interpreted in two ways. It can refer to the flow of energy and nutrients through an ecosystem or to the flow of species populations through time, i.e. the persistence of species populations and their properties, what Holling calls the resilience of the system (Holling 1973, 1986 Solbrig 1993). The usual way of looking at ecosystem function is to consider only the flow of energy and nutrients. We first discuss how species characteristics control the flow of energy and...

Biodiversity Of Mangroves

Mangrove Ecosystem Structure

Biodiversity is usually defined at three levels, i.e. species, populations and ecosystems (Ray and McCormick 1992). The term biodiversity components has been recommended as an ecological reference to these several hierarchical levels, and the idea is particularly appropriate to describe tropical estuarine ecosystems (Yanez-Arancibia et al. 1994). Biodiversity components of tropical estuaries can refer to the high diversity of species, life histories, habitats and links in food webs, or the...

Tropical forests

The lime dimension Tropica forests illustrate the importance of the time dimension in considering the roles of species in ecosystem functioning. Through selective harvesting of plants and animals we have performed many experiments' to test the role of various species and functional groups in the functioning of total ecosystems. However, interpreting the results of these experiments may take a long time, since many organisms live for centuries and many ecosystem processes have very long time...