Species richness

Legislation enacted by both Canada and the United States (see the US-Canada Air Quality Accord, 1991) will, when implemented, reduce the North American emissions of sulphur dioxide by about 50% based upon the 1980 baseline. These projected emission fields have been appplied in the atmospheric source-receptor models that were described above, to provide a projected deposition field for acidic sulphate that would be expected (14). The predicted sulphate deposition fields have then subsequently been appUed in aquatic effects models that provide estimates of regional surface water acidification distributions (50). The regional acidification profiles have then been used in a model of fish species richness (51) that results in an estimate of the expected presence of fish species as compared to that expected in an unacidified case. 

Water fluctuations in Mediterranean rivers seriously affect fish production and droughts put important selective forces on fish communities [73] by reducing population density and species richness [58], Fish also suffer from chemical and organic pollution affecting their physiological abilities [90],... 

It has been found that many environmental factors influence the amount and composition of root exudates and hence the activity of rhizosphere microbial populations. Microbial composition and species richness at the soil-plant interface are related either directly or indirectly to root exudates and thus vary according to the same environmental factors that influence exudation. In es.sence, the rhizosphere can be regarded as the interaction between soil, plants and microorganisms. Figure 2 shows some of the factors associated with these interactions, which will be discussed during the course of the chapter. Here we mention briefly the influence of some plant and microbial factors on root exudation and rhizosphere microbial populations, while soil factors are discussed later. 

Pysek P, Jarosik V, Kropac Z, Chytry M, Wild J and Tichy L (2005). Effects of abiotic factors on species richness and cover in Central European weed communities . Agriculture, Ecosystems Environment, 109, 1-8. 

Table 6.1 Literature overview of the relation between species richness and P concentration...

Habitat Relation species richness to P P concentration Reference... 

One of the major future challenges affecting phytodiversity is climate change. In the following, we will discuss current knowledge concerning the influence of climate change on plant species richness via effects on nutrient availabilities and invasive species. 

Giisewell S (2004) N P ratios in terrestrial plants variation and functional significance. New Phytol 164 243-266. doi http //www.blackwell-synergy.com/doi/abs/10. Ill 1/j. 1469-8137.2004.01192.x Giisewell S, Bailey KM, Roem WJ, Bedford BL (2005) Nutrient limitation and botanical diversity in wetlands can fertilisation raise species richness Oikos 109 71-80. doi http //www.black-well-synergy.com/doi/abs/10.1111/j.0030-1299.2005.13587.x Halsted M, Lynch J (1996) Phosphorus responses of C3 and C4 species. J Exp Bot 47 497-505. 

Nematode population Various extraction techniques Indicates soil food web functioning, species richness, and abundance spatially variable time-consuming Blair et al. (1996)... 

Beetles (Coleoptera) comprise the most species-rich insect order. About 350,000 species have been described today, about 10% of the estimated actual amount. Apart from open oceans, beetles are colonizing almost every habitat and are able... 

N limited. Nutrient availability also affects the composition of plant communities species richness and the presence of rare species often decline as nutrient availability increases beyond some threshold (Bedford et al., 1999). In addition to the inflow of nutrients with the water and sediment, there are complicated interactions between hydrology and nutrient availability that affect productivity and decomposition. Transformations of N and P under anaerobic conditions are discussed in Section 4.3. 

Kraft mill that had used elemental chlorine historically Microbial community and diatom species in lake sediments sampled from 2-8 cm depths Drop in the ATP content, depressed butyrate-esterase activity indicating toxicity to microorganisms, and reduction in diatom species richness Mika et al., 1999 [31]... 

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