ECOSYSTEMS-AND-COMMUNITI課件(PPT 50頁)

1、ECOSYSTEMS AND COMMUNITIES第1頁，共50頁。OUTLINESuccession（演替）Primary, Secondary（原生，次生）Terrestrial, Aquatic（陸地，水域）Climax Communities Biomes 生物群系A(chǔ)quatic Ecosystems HIT Environmental Science Wang Xiuheng 2008第2頁，共50頁。SUCCESSION 演替Ecosystems are dynamic.Succession: A series of regular, predictable changes in

2、 the structure of a community over time.Occurs because perturbations（干擾） to an area often make the environment less suitable for current organisms and more suitable for others. HIT Environmental Science Wang Xiuheng 2008第3頁，共50頁。Primary Succession - Begins with bare mineral surfaces or water.Seconda

3、ry Succession - Begins with disturbance of an existing ecosystem. HIT Environmental Science Wang Xiuheng 2008第4頁，共50頁。Terrestrial Primary SuccessionPioneer Community（先驅(qū)群落）: Collection of organisms able to colonize bare rock. ?e.g. Lichens help break down rock and accumulate debris, helping to form a

4、 thin soil layer.Soil layer begins to support small life forms. HIT Environmental Science Wang Xiuheng 2008第5頁，共50頁。 Eventually a climax community is reached HIT Environmental Science Wang Xiuheng 2008第6頁，共50頁。In general, climax communities are more stable and have larger, more diverse populations o

5、f species than earlier stages of succession.Successional (seral) stage (演替階段) - each step in the process. HIT Environmental Science Wang Xiuheng 2008第7頁，共50頁。Aquatic Primary SuccessionExcept for oceans, most aquatic systems are considered temporary.All aquatic systems receive inputs of soil particle

6、s and organic matter from land. - results in gradual filling of shallow bodies of water. Plants can begin to take root. HIT Environmental Science Wang Xiuheng 2008第8頁，共50頁。Secondary SuccessionOccurs when an existing community is disturbed or destroyed. flood, fire, plow HIT Environmental Science Wan

7、g Xiuheng 2008第9頁，共50頁。With most disturbances, most of the soil remains, and many nutrients necessary for plant growth may be available for reestablishment of the previous ecosystem.more rapid. HIT Environmental Science Wang Xiuheng 2008第10頁，共50頁。Secondary Succession from a beaver bond HIT Environme

8、ntal Science Wang Xiuheng 2008第11頁，共50頁。Question BreakHow does primary succession differ from secondary succession? HIT Environmental Science Wang Xiuheng 2008第12頁，共50頁。Climax Communities BiomesTerrestrial climax communities with wide geographic distributions. Usually defined by undisturbed natural

9、plant communities.Two main non-biological factors determining biomes:TemperaturePrecipitation HIT Environmental Science Wang Xiuheng 2008第13頁，共50頁。 HIT Environmental Science Wang Xiuheng 2008第14頁，共50頁。 HIT Environmental Science Wang Xiuheng 2008第15頁，共50頁。Elevation Effects on Climate and VegetationAs

10、 altitude increases, average temperature decreases.Moving from sea level to mountain tops, it is possible to pass through a series of biomes similar to what would be encountered moving from the equator to the north pole. HIT Environmental Science Wang Xiuheng 2008第16頁，共50頁。 HIT Environmental Science

11、 Wang Xiuheng 2008第17頁，共50頁。DesertGrasslandSavannaShrublandsTropical RainforestNorthern Coniferous ForestsTemperate Deciduous ForestMajor types of Biomes HIT Environmental Science Wang Xiuheng 2008第18頁，共50頁。Less than 25cm annual precipitation unevenly distributed throughout the year.Hot? No life?Lar

12、ge daily temp. fluctuations. No Cloud. Most species exhibit specialized adaptations to climate.Deserts HIT Environmental Science Wang Xiuheng 2008第19頁，共50頁。 HIT Environmental Science Wang Xiuheng 2008第20頁，共50頁。Some definitions Rangelands, Grassland: the non-forest areas Savannas: mainly grasses and

13、shrubs with scattered trees Woodlands: trees more common; trees widely spaced (park-like) with canopy cover 30%, Mostly 10 m tall, Occupy around 5% continent HIT Environmental Science Wang Xiuheng 2008第21頁，共50頁。GrasslandsReceive 25-75cm of annual precip. Rainfall sporadic enough to cause draughtsFir

14、e regime usually present.Historically evolved with large herds of migratory grazing mammals.Convert to agriculture or stock raising. Why? HIT Environmental Science Wang Xiuheng 2008第22頁，共50頁。 HIT Environmental Science Wang Xiuheng 2008第23頁，共50頁。Savanna 熱帶稀樹草原50-150cm of annual precip. Not evenly. HI

15、T Environmental Science Wang Xiuheng 2008第24頁，共50頁。Mediterranean Shrubland HIT Environmental Science Wang Xiuheng 2008第25頁，共50頁。Tropical Dry Forest HIT Environmental Science Wang Xiuheng 2008第26頁，共50頁。TropicalRainforestsLocated near equator, temp. is relatively warm and constant. Over 200cm annual r

16、ainfall.Closed canopy (70% FPC), Often H30 m HIT Environmental Science Wang Xiuheng 2008第27頁，共50頁。Laterite soil allows high levels of leaching, thus most nutrients are tied-up in biomass.Buttress roots, extensive network with fungi. HIT Environmental Science Wang Xiuheng 2008第28頁，共50頁。Very high spec

17、ies diversityMany tree species ( 50 per ha)Forests (cover 5% world area) have 50% vertebrate species in the worldDependency on forests mammals 77% reptiles 33%Space occupied ground (logs, litter) tree hollows (many dependent) HIT Environmental Science Wang Xiuheng 2008第29頁，共50頁。Taiga, Northern Conif

18、erous ForestsShort, cool summer and long winters Receive 25-100cm annual rainfall.Common species, Spruces, firs, larches.Insect, migrant birds, mammals HIT Environmental Science Wang Xiuheng 2008第30頁，共50頁。 HIT Environmental Science Wang Xiuheng 2008第31頁，共50頁。Temperate Deciduous ForestsMost areas rec

19、eive over 100cm annual rainfall.Fewer species, 2 or 3 dominant tree species.Spring wildflowersInsect, migrant birds, mammals HIT Environmental Science Wang Xiuheng 2008第32頁，共50頁。 HIT Environmental Science Wang Xiuheng 2008第33頁，共50頁。TundraTundra HIT Environmental Science Wang Xiuheng 2008第34頁，共50頁。Ma

20、jor Aquatic EcosystemsFour factors influencing aquatic ecosystems:Penetration of suns raysNature of bottom substrateWater temperatureAmount of dissolved materialsDissolved salt: fresh water, marine HIT Environmental Science Wang Xiuheng 2008第35頁，共50頁。Marine Ecosystems Pelagic Marine Ecosystems （大洋）

21、Pelagic Region - Open seaPhytoplankton（浮游植物）- microscopic plants floating in the ocean. (perform photosynthesis, upper level)Zooplankton （浮游動物） - Microscopic animals of many kinds. (feed on phytoplankton, depth, eat phy. at night) HIT Environmental Science Wang Xiuheng 2008第36頁，共50頁。 HIT Environment

22、al Science Wang Xiuheng 2008第37頁，共50頁。Productive aquatic ecosystems are those in which essential nutrients are common. (from currents, rivers) HIT Environmental Science Wang Xiuheng 2008第38頁，共50頁。Benthic Marine EcosystemsBottom of the sea淺海，深淵Organism attached or notSubstrate is very important in co

23、mmunity developmentSand, mud, rockCoral reef eco. Southern China Sea HIT Environmental Science Wang Xiuheng 2008第39頁，共50頁。Estuaries（河口）Shallow, partially enclosed areas where freshwater enters the ocean, a bridge between freshwater and marine eco.Number of species is lessExtensive production because

24、 of shallow, warm, nutrient-rich areasPrevent ocean pollution, gradual filling results in terrestrial. HIT Environmental Science Wang Xiuheng 2008第40頁，共50頁。Mangrove swamp ecosystems (紅樹林)Shallow region near shore with light waveTolerate salt, long seeds trapped in mud to take root. Trap sediment, de

25、velop terrestrial eco. HIT Environmental Science Wang Xiuheng 2008第41頁，共50頁。Freshwater EcosystemsTwo broad Categories:Stationary Water: lake, reservoirRunning Water: river, streamWetland, Glacier HIT Environmental Science Wang Xiuheng 2008第42頁，共50頁。Lakes and PondsLittoral and Limnetic zones - presen

26、ce or absence of rooted vegetation. HIT Environmental Science Wang Xiuheng 2008第43頁，共50頁。Productivity of a lake determined by many factors.Cold temps - Shallow depth - Erosion sediments from land- Dissolved nutrient levels HIT Environmental Science Wang Xiuheng 2008第44頁，共50頁。Eutrophic （富營養(yǎng)）- Shallow

27、, warm, nutrient-richOligotrophic （貧營養(yǎng)）- Deep, cold, nutrient-poorDO-Dissolved OxygenBOD (化學(xué)需氧量) Biochemical Oxygen Demand, breakdown of organic material by bacteria and fungi uses oxygen from water. HIT Environmental Science Wang Xiuheng 2008第45頁，共50頁。Streams and RiversEven though most streams are shallow, it is difficult for most photosynthetic organisms to accumulate nutrients necessary for growth.Most clear streams are not very producti