It accumulates salts to the soil preventing or

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Unformatted text preview: ltered ecosystems Crystalline iceplant invades California coastal communities. It accumulates salts to the soil, preventing or retarding native species Altered ecosystems Southwestern desert plants, such as saguaro cactus, are usually widely spaced with no build up of leaf litter, therefore fires are rare and the native vegetation has little fire resistance. Non-native grasses such as this buffelgrass form nearly continuous cover which allows fires that spread rapidly, killing native cacti, shrubs and other perennials over large areas. Heyer Altered ecosystems • Saltcedar (Tamarix ) invades and displaces desert riparian habitats. • It clogs stream beds altering erosion patterns. • Increased transpiration rates cause vital pools and streams to dry up. • Saltcedar foilage decomposes more rapidly removing the primary productivity. Abundance and diversity of stream macroinvertebrates and fish decrerases significantly. 14 Community Ecology Altered ecosystems Dissolved oxygen and light penetration in the Hudson River with native ( Vallisneria) or invasive (Trapa ) plant cover • Invasive aquatic plants can sharply reduce light levels and dissolved oxygen concentrations in the waters they occupy. Minimum DO 2 for fish & invertebrate respiration Altered ecosystems Atlantic smooth cordgrass (Spartina alterniflora ) has invaded mudflat communities in Pacific coast estuaries • Encroaches further over mudflats...
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