《生物与气候》PPT课件.ppt

生物地理學,氣候陸生生態系,風 地球循環系統的重要部份,地理生態學,To do science is to search for patterns,not simply to accumulate facts,and to do the science of geographical ecology is to search for patterns of plant and animal life that can be put on a map.,氣候,Weather 任何時間地點的溫度,壓力,溼度,降水,日照,雲量,風向,風速等物理特性Front 兩個具不同溫度與密度的氣團的交界,氣候,Warm Front 暖空氣密度較低,遇冷空氣上升凝結成雲,逐漸厚實後雲層降低,釋放其濕氣時將飄小雨Cold Front 冷空氣密度較高,於暖空氣下方呈楔形,被推擠向上的暖空氣凝結成大水滴,常有雷雨形成,氣候,Tornado 龍捲風 於陸地上快速形成難以預測Tropical cyclone 熱帶暴風 於海上長期形成可追蹤其路徑與風速 生成於大西洋稱颶風,於太平洋稱颱風,氣候,Climate 長期的天氣狀況,平均溫度與平均雨量為決定氣候的兩個重要因子,氣候,氣流與氣候 1.地表受熱不均 2.地球軸線(假想線)為傾斜 3.地球自轉 4.太陽能量的偶發性衝擊地球 5.空氣與水的特性,洋流與氣候,溫室效應,Rain shadow effect,Sea and Land Breezes,地球的主要生態系,溫度雨量與生態系,溫度雨量與生態系,海拔緯度與生態系,世界主要沙漠分布,Two major bands:30o N and 30o S.Occupy about 30%of earths land surface.Water loss exceeds precip.most of the year.Soil usually extremely low in organic matter.Plant cover ranges from sparse to absent.Animal abundance low,but biodiversity may be relatively high.Strong behavioral adaptations.Human intrusion increasing.,人類對沙漠的衝擊,世界主要草原分布,Tropical Savanna,Often occur immediately N/S of Rain Forests.Climate alternates between wet/dry seasons.Drought associated with dry season leads to dry conditions and subsequent lightning-caused wildfires.Soils have low water permeability.Saturated soils keeps trees out.Increasing pressure to produce livestock.,Temperate Grassland,Extremely widespread distribution.Annual rainfall 300 1,000 mm.Experience periodic droughts.Soils tend extremely nutrient rich and deep.Thoroughly dominated by herbaceous vegetation.Large roaming ungulates.Bison vs.cattle,Tundra,Covers most of lands N of Arctic Circle.Climate typically cool and dry with short summers.200-600mm precip.Low decomposition rates.Supports substantial numbers of native mammals.Human intrusion historically low,but increasing as resources become scarce.,人類對草原的衝擊,世界主要森林分布,Tropical Rainforests,Most occur within 10o lat.of equator.Little temp.variation between month.Annual rainfall 2,000 4,000 mm relatively evenly distributed.Heavy rainfall quickly leaches soil nutrients.Organisms add vertical dimension to ecology.Harbor staple foods and medicines for worlds human populations increasingly exploited.,Latitudinal Gradients in Species Richness,Most groups of organisms are more species-rich in the tropics.Brown grouped hypotheses into six categories:Time Since PerturbationMore species in the tropics because tropics are older and disturbed less frequently.More time for speciation,and less frequent disturbance reduces extinction rate.,Latitudinal Gradients in Species Richness,ProductivityHigh productivity contributes to high species richness.More energy to divide among population.Environmental HeterogeneityMore heterogeneity thus more potential habitat areas and niches.,Latitudinal Gradients in Species Richness,FavorablenessTropics have more favorable environments.No extremes to limit diversity.Niche Breadth and Interspecific InteractionsVarious themes Brown suggests that ultimate causes must by physical differences.,Latitudinal Gradients in Species Richness,Speciation and Extinction RatesRosenzweig proposed immigration can be largely discounted at broad scales,thus speciation will be primary source of new species.Species removal via extinction.Tropics richness is greater due to higher rates of speciation and/or lower rates of extinction.,Temperate Forest,Majority lie between 40o and 50o.Rainfall averages 650 3,000 mm.Fertile soilsLong growing seasons dominated by deciduous plants.Short growing seasons dominated by conifers.Biomass production can be very high.Many major human population centers.,Boreal Forest(Taiga),Confined to N.hemisphere.Covers 11%of earths land area.Thin,acidic soils low in fertility.Generally dominated by evergreen conifers.Relatively high animal density.Historically,low levels of human intrusion.,人類對森林的衝擊,Mountain Biomes,Make up almost a fourth of the worlds land surface.Contain the majority of the worlds forest.Regulate the earths climate when their snow-and ice-covered tops reflect solar radiation back into space.Play a critical role in the hydrological cycle.,人類對山地的衝擊,Three Major Lessons,Different climates occur as a result of currents of air and water flowing over an unevenly heated planet spinning on a tilted axis.Different climates resulted in different communities of organisms,or biomes.Everything is connected!,