1. Biomes Major ecosystems found in large geographic regions characterized by a distinct vegetative community --primarily a result of abiotic processes Physiognomy The overall appearance of a biome or community based on the relative density, height, and shape of its dominant vegetation

2. Six major biomes: 1. tropics 2. grasslands/savannah 3. temperate forests 4. coniferous forests or taiga 5. tundra 6. deserts

3. Fig. 24.3 Minor biomes: 1. chaparral 2. temperate rain forest 3. polar regions

4. Fig. 24.4

5. Tropical Biomes : Most occur within 10° latitude Defined by rainfall > 240 cm per year Temperature and moisture not limiting factors, nutrients and light are

6. Amazon (Neotropics) Congo SE Asia New World Old World

7. Misconceptions about tropics: Soils are rich Climate is stable Jungles are dense

8. dense canopy, stratified up to four levels Physiognomy of Tropics high diversity of trees 400-700 trees per hectare 100-200 species represented low population densities for each

9. Humidity ~70% Humidity 90-95% Temperature gradient Fig. 25.6 High light attenuation

10. Leaf litter accumulates rapidly, but decays rapidly Plants in competition for nutrients released in decay

11. Physiognomy of Tropics shallow, spreading roots and leaves with drip tips

12. Physiognomy of Tropics shallow, spreading roots and leaves with drip tips Mycorrhiza fungi and hyphae buttress and prop roots

13. Physiognomy of Tropics shallow, spreading roots Mycorrhiza fungi and hyphae buttress and prop roots epiphytes, lianas

14. Gaps and patch dynamics

15. Semi-aquatic herbivores Nocturnal frugivores Diurnal herbivores Nocturnal herbivores Ant eaters Parallel Evolution

16. Hammocks in south Florida

17. Temperate rain forest: Olympic National Park, WA

18. Longleaf Pine community of the Southeast

19. http://www.worldwildlife.org/

20. Deserts are defined by rainfall: true desert has < 12 cm/yr extreme desert < 7 cm/yr semi-desert has up to 40 cm/yr evaporation exceeds rainfall

21. Deserts also characterized by: hot days, cool nights from high albedo sparse plant life C 4 and CAM photosynthesis xerophytes more living plant biomass below ground than above, sometimes 1:10 difference

23. Four major North American Deserts 1.Sonoran 2.Mohave 3.Chihuahuan 4.Great Basin

24. Sonoran Desert Lowest, hottest desert up to 120° F in summer Bi-annual rainfall ~18 cm/yr Most diverse desert in NA Saguaro Cactus limited by temperature

25. Sonoran Desert, AZ cholla cactus ocotilla palo verde trees

26. Mohave Desert Most precipitation in winter 5-12 cm/yr Higher elevation than Sonoran Plants adapted to cooler temperatures

27. Joshua Trees

28. Cholla cactus and yucca

29. Chihuahuan desert and creosote Most precipitation in summer 15-20 cm/yr Dominated by low shrubs and cactus

30. Prickly Pear Cactus

31. Great Basin Desert Largest U.S. desert, considered a cold desert Elevations range from 5000-6000 feet Caused by a series of rainshadow effects Precipitation 15-25 cm/yr Dominated by sagebrush

32. Sagebrush dominates

33. All deserts are characterized by slow growth by plants, but also slow decay of litter Very fragile ecosystems because of this Disturbances, even a single car track, may last decades to centuries Archaeological roads, clearings still visible after 1000+ years

34. Kangaroo Rat: Endemic to North America

35. Kangaroo Rat Adaptations No sweat glands and never drink water Kidneys concentrate urine 5X more than humans Nocturnal behavior, with large auditory bulla Stay in burrows during day, plug entrance and cache seeds Use torpor for brief periods, have bare feet to radiate heat, or cover with tail to retain heat Rostrum long, with complex nasal bones, convoluted surfaces cooled by evaporation to capture water in air leaving body

36. Jerboa

37. Sonoran desert exclosure experiment show keystone effect Ants in Deserts high diversity, granivores Chihuahuan desert: 23 spp. in 30 m 2 50 spp. in 3 km transect Australia: 150 spp. in < 1 ha desert grasses dominate