Ecosystem, terrestrial

Impacts of Nitrogen Deposition on Terrestrial Ecosystems, Report of the United Kingdom Review Group on Impacts of Atmospheric Nitrogen, Department of the Environment, London, 1994. Report of the AERC Institute of Arable Crops Research for 1991, AERC, London, 1992, p. 36. 

INDITE, Impacts of Nitrogen Deposition in Terrestrial Ecosystems in the United Kingdom,... 

Legge, A. H., and Krupa, S, V., "Air Pollutants and Their Effects on the Terrestrial Ecosystem." Wiley, New York, 1986. 

Particulate emissions have their greatest impact on terrestrial ecosystems in the vicinity of emissions sources. Ecological alterations may be the result of particulate emissions that include toxic elements. Furthermore, the presence of fine particulates may cause light scattering, known as atmospheric haze, reducing visibility and adversely affecting transport safety, property values, and aesthetics. 

Atmospheric Transport, Deposition, and Potential Effects on Terrestrial Ecosystems... 

Air Pollutants and their Effects on Terrestrial Ecosystems. Legge, A.H. Krupa, S.V. Eds., John Wiley Sons NY, 1986. 

Figure 3. Feedbacks in terrestrial ecosystem responses to C02-induced climate change. Arrows with plus signs (-I-) indicate processes that have positive effects or that increase the rates of other processes. Arrows with minus signs (—) indicate processes that have the opposite effects.

The most common way in which the global carbon budget is calculated and analyzed is through simple diagrammatical or mathematical models. Diagrammatical models usually indicate sizes of reservoirs and fluxes (Figure 1). Most mathematical models use computers to simulate carbon flux between terrestrial ecosystems and the atmosphere, and between oceans and the atmosphere. Existing carbon cycle models are simple, in part, because few parameters can be estimated reliably. 

There are two types of data necessary to obtain accurate global estimates of vegetation carbon pools or biomass. First, it is important to have accurate data on the areal extent of major ecosystems. Matthews (29) found that calculations of global biomass were significantly influenced by the land cover data set used. Second, there must be accurate estimates of biomass density for terrestrial ecosystems. There is a wide range of estimates published for the same ecosystem, each derived by different methods (29), and none having statistical reliability (7). 

Field, C. B., Chapin III, F. S., Matson, P. A., and Mooney, H. A. (1992). Responses of terrestrial ecosystems to the changing atmosphere a resource-based approach. Annu. Rev. Ecol. System. 23, 201-235. 

Schimel, D. S. (1995). Terrestrial ecosystems and the carbon cycle. Glob. Change Biol. 1, 77-91. 

Plate 3 shows a map of dominant soil orders for the entire world. Although this map necessarily lacks detail due to its scale, the relationship between soils and the biosphere is evident. Different terrestrial ecosystems are correlated with climatic conditions and different soils are correlated with both. For example, Mollisols are common in areas where there are prairies or steppes a result of grasses as the dominant vegetation and low, seasonal rainfall. Spodosols occur where coniferous forests dominate and the climate is cold and wet. Comparing Fig. 8-5 and Plate 3 carefully will show how strong this correlation is for the entire Earth. 

Watersheds, also known as drainage basins, define a natural context for the study of relationships among soils, geology, terrestrial ecosystems, and the hydrologic system because water and sediment travel downslope under the influence of gravity. This material is a continuation of some of what was presented in Chapter 6. 

Large amounts of carbon are found in the terrestrial ecosystems and there is a rapid exchange of carbon between the atmosphere, terrestrial biota, and soils. The complexity of the terrestrial ecosystems makes any description of their role in the carbon cycle a crude simplification and we shall only review some of the most important aspects of organic carbon on land. Inventories of the total biomass of terrestrial ecosystems have been made by several researchers, a survey of these is given by Ajtay etal.(1979). 

There is a group of organic compounds in terrestrial ecosystems that are not readily decomposed and therefore make up a carbon reservoir with a long turnover time. There are... 

Braswell, B. H., Schimel, D. S., Linder, E. and Moore III, B. (1997). The response of global terrestrial ecosystems to interannual temperature variability. Science 278,870-872. 

Cao, M. and Woodward, F. I. (1998). Dynamic responses of terrestrial ecosystem carbon cycling to global climate change. Nature 393,249-252. 

Kindermann, J., Wiirth, G., Kohlmaier, G. H. and Badeck, F.-W. (1996). Interannual variations of carbon exchange fluxes in terrestrial ecosystems. Global Biogeochem. Cycles 10, 737-755. 

Meliilo, J. M., Steudler, P. A., Aber, J. D. and Bowden, R. D. (1989). Atmospheric deposition and nutrient cycling. In "Dahlem Workshop on Exchange of Trace Gases Between Terrestrial Ecosystems and the Atmosphere" (M. O. Andreae and D. S. Schi-mel, eds). Wiley Interscience Publishers, New York. 

A global representation of the P cycle, by necessity, will be general. It will combine a wide variety of P-containing components into relatively few reservoirs and will parameterize intricate processes and feedback mechanisms into simple first-order transfers. To appreciate the rationale behind the construction of such a model and to understand its limitations, the transfers of P within a hypothetical terrestrial ecosystem and in a generalized ocean system will be discussed first. 

The dominant processes controlling the movements of P through terrestrial ecosystems are schematically presented in Fig. 14-4. In a general way, the overall movement of P on the continents may be envisioned as the constant erosion of P from continental rocks and transport in both dissolved and particulate form by rivers to the ocean, stopping occasionally along this pathway to interact with biological and mineralogical systems. 

Lerman et al. (1975) considered several cases in which mankind s activities perturbed the natural cycle. If we assume that all mined P is supplied to the land as fertilizer and that all of this P is incorporated into land biota, the mass of the land biota will increase by 20%. This amount is small relative to the P stored in the land reservoir. Since P incorporated into land biota must first decompose and be returned to the land reservoir before being transported further, there is essentially no change in the other reservoirs. Thus, although such inputs would significantly alter the freshwater-terrestrial ecosystem locally where the P release is concentrated, the global cycle would be essentially unaffected. 

On the other hand, reservoirs are ecosystems strongly linked with the surrounding terrestrial ecosystems, and it is hardly useful to model them independently. 

Terrestrial ecosystems (plants and animals) under water scarcity suffer from water stress, and aquatic ecosystems of intermittency in water flow. Water scarcity has implications on hydrologic resources and systems coimectivity, as well as negative side-effects on biodiversity, water quality, and river ecosystem functioning. Finally, water scarcity has also direct impacts on citizens and economic sectors that use and depend on water, such as agriculture, tourism, industry, energy and transport. 

Tieszen, L.L. and Boutton, T.W. 1989 Stable carbon isotopes in terrestrial ecosystem research. In Rundel, P.W., Ehleringer, J.R. and Nagy, K.A., eds., Stable Isotopes in Ecological Research. New York, Springer-Verlag 167-195. 

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