托福TPO31阅读Passage3原文文本+题目+答案解析 为了帮助大家高效备考托福，为大家带来托福TPO31阅读Passage3原文文本+题目+答案解析，希望对大家备考有所帮助。 Savanna Formation Located in tropical area at low altitudes,savannas are stable ecosystems,some wet and somedry consisting of vast grasslands with scattered treeor shrubs.They occur on a wide range of soil typesand in extremes of climate.There is no simple or single factor that determines if a given sitewill be a savanna,but some factors seem to play important roles in their formation. 热带草原或热带稀树草原位于热带低海拔地区，干湿气候皆有。稀疏分布着树木和灌木的广阔大草原，其为一个稳定的生态系统。气候极端，涵盖了广泛的土壤种类。对于热带草原的形成原因，虽无单一的解释，但似乎仍有一些因素对其形成起到了重大作用。 Savannas typically experience a rather prolonged dry season.One theory behind savannaformation is that wet forest species are unable to withstand the dry season,and thussavanna,rather than rain forest,is favored on the site.Savannas experience an annual rainfallof between 1010 and 2000 millimeters,most of it falling in a five-to-eight month wet season.Though plenty of rain may fall on a savanna during the year,for at least part of the year littledoes,creating the drought stress ultimately favoring grasses.Such conditions prevailthroughout much of northern South America and Cuba,but many Central American savannasas well as coastal areas of Brazil and the island of Trinidad do not fit this pattern.In theseareas,rainfall per month exceeds that in the above definition,so other factors mustcontribute to savanna formation. 热带草原通常会经历十分漫长的旱季。热带草原形成理论之一，就是湿润的森木物种无法承受干燥的季节这更有利于热带草原，而不是热带雨林的形成。热带草原的年降水量在1010到2000毫米，绝大多数降水都集中在长达5到8个月的雨季中。虽然每年的降水总量充足，但至少会有几个月几乎零降水，由此引起的干旱使得该地区最终只适合草地生长。这样的条件广泛地分布于南美北部和古巴的大部分地区，但也有例外，比如在中美洲的稀树大草原，巴西的沿海地区和特立尼达岛气候的类型就不一样。在这些地区每月的降水量超过了之前定义的降水量范围，因此还有其他因素影响着热带草原的形成。 In many characteristics,savanna soils are similar to those of some rain forests,thoughmore extreme.For example,savanna soils,like many rain forest soils,are typically oxisols(dominated by certain oxide minerals)and ultisols(soils containing no calcium carbonate),with a high acidity notably low concentrations of such minerals as phosphorus,calcium,magnesium,and potassium,while aluminum levels are high.Some savannas occur on wet,waterlogged soils;other dry,sandy,well-drained soils.This many seem contradictory,but itonly means that extreme soil conditions,either too wet or too dry for forests,are satisfactoryfor savannas.More moderate conditions support moist forests. 为了帮助大家高效备考托福，为大家带来托福TPO31阅读Passage3原文文本+题目+答案解析，希望对大家备考有所帮助。 Savanna Formation Located in tropical area at low altitudes,savannas are stable ecosystems,some wet and somedry consisting of vast grasslands with scattered treeor shrubs.They occur on a wide range of soil typesand in extremes of climate.There is no simple or single factor that determines if a given sitewill be a savanna,but some factors seem to play important roles in their formation. 热带草原或热带稀树草原位于热带低海拔地区，干湿气候皆有。稀疏分布着树木和灌木的广阔大草原，其为一个稳定的生态系统。气候极端，涵盖了广泛的土壤种类。对于热带草原的形成原因，虽无单一的解释，但似乎仍有一些因素对其形成起到了重大作用。 Savannas typically experience a rather prolonged dry season.One theory behind savannaformation is that wet forest species are unable to withstand the dry season,and thussavanna,rather than rain forest,is favored on the site.Savannas experience an annual rainfallof between 1010 and 2000 millimeters,most of it falling in a five-to-eight month wet season.Though plenty of rain may fall on a savanna during the year,for at least part of the year littledoes,creating the drought stress ultimately favoring grasses.Such conditions prevailthroughout much of northern South America and Cuba,but many Central American savannasas well as coastal areas of Brazil and the island of Trinidad do not fit this pattern.In theseareas,rainfall per month exceeds that in the above definition,so other factors mustcontribute to savanna formation. 热带草原通常会经历十分漫长的旱季。热带草原形成理论之一，就是湿润的森木物种无法承受干燥的季节这更有利于热带草原，而不是热带雨林的形成。热带草原的年降水量在1010到2000毫米，绝大多数降水都集中在长达5到8个月的雨季中。虽然每年的降水总量充足，但至少会有几个月几乎零降水，由此引起的干旱使得该地区最终只适合草地生长。这样的条件广泛地分布于南美北部和古巴的大部分地区，但也有例外，比如在中美洲的稀树大草原，巴西的沿海地区和特立尼达岛气候的类型就不一样。在这些地区每月的降水量超过了之前定义的降水量范围，因此还有其他因素影响着热带草原的形成。 In many characteristics,savanna soils are similar to those of some rain forests,thoughmore extreme.For example,savanna soils,like many rain forest soils,are typically oxisols(dominated by certain oxide minerals)and ultisols(soils containing no calcium carbonate),with a high acidity notably low concentrations of such minerals as phosphorus,calcium,magnesium,and potassium,while aluminum levels are high.Some savannas occur on wet,waterlogged soils;other dry,sandy,well-drained soils.This many seem contradictory,but itonly means that extreme soil conditions,either too wet or too dry for forests,are satisfactoryfor savannas.More moderate conditions support moist forests.