hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width. When the gully formation is in process, the water flow rate can be substantial, which causes the significant deep cutting action into soil. 15. What environmental problems occur in temperate grassland? Few natural temperate grassland regions remain because most have been turned into farms or grazing land. This is because they are flat, covered with grass and have a rich soil. Overgrazing, ploughing, and excess salts left behind by irrigation waters harm temperate grasslands. Strong winds blow loose soil from the ground after ploughing, especially during droughts. TV H 1-7 lk 26-28 http://www.blueplanetbiomes.org/world_biomes.htm http://www.ucmp.berkeley.edu/exhibits/biomes/index.php http://www.ucmp.berkeley.edu/glossary/gloss5/biome/ http://www.mbgnet.net/ http://www.worldbiomes.com/ http://www.thewildclassroom.com/biomes/ http://kids.nceas.ucsb.edu/biomes/index.html
under grazing in savannas. Grazing also promotes the spread of weeds in savannas by the removal or reduction of the plants which would normally compete with potential weeds and hinder establishment. In addition to this cattle and horses are implicated in the spread of the seeds of weed species such as Prickly Acacia and Stylo. These alterations in savanna species composition brought about by grazing can alter ecosystem function, and are exacerbated by overgrazing and poor land management practices. Introduced grazing animals can also affect soil condition through physical compaction and break-up of the soil caused by the hooves of animals and through the erosion effects caused by the removal of protective plant cover. Such effects are most likely to occur on land subjected to repeated and heavy grazing. The effects of overstocking are often worst on soils of low fertility and in low
12' 0" =t=, .- Jan Apr Jul - 1 Oct O· overgrazing and ag ricul ture. 11' -__[20' SAN FRANOSCO. USA l~: l - _ _ - - - - 10'
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