Earth's Neighborhoods - Ecology Principles PDF

Principles in Ecology PCB 4043 Earth’s neighborhoods Prof. Fahimipour (pronounced “Fa-he-me-poor”) Topics: Biomes, climate, and ancient Egypt [email protected] D: 437 DW | B: 206 Sanson Biomes  Earth’s neighborhoods The biosphere is the zone of life on Earth. It lies between: –The lithosph...

Principles in Ecology PCB 4043 Earth’s neighborhoods Prof. Fahimipour (pronounced “Fa-he-me-poor”) Topics: Biomes, climate, and ancient Egypt [email protected] D: 437 DW | B: 206 Sanson Biomes  Earth’s neighborhoods The biosphere is the zone of life on Earth. It lies between: –The lithosphere—Earth’s surface crust and upper mantle (but see L) –The troposphere—the lowest layer of the atmosphere (but see R) “Biomes” will introduce the diversity of terrestrial and aquatic life.  Terrestrial biomes Biomes: large-scale terrestrial communities shaped by the physical environment (especially at big spatial scales) Categorized by dominant plant growth forms and characteristics such as leaf deciduousness or succulence. Taxonomic relationships are not taken into account; the biome concept relies on similarities in the morphological responses of organisms to the physical environment.  Terrestrial biomes Biomes: large-scale terrestrial communities shaped by the physical environment (especially at big spatial scales) Categorized by dominant plant growth forms and characteristics such as leaf deciduousness or succulence. Taxonomic relationships are not taken into account; the biome concept relies on similarities in the morphological responses of organisms to the physical environment. Why are we so vegetation biased?  Terrestrial biomes Biomes: large-scale terrestrial communities shaped by the physical environment (especially at big spatial scales) Categorized by dominant plant growth forms and characteristics such as leaf deciduousness or succulence. Taxonomic relationships are not taken into account; the biome concept relies on similarities in the morphological responses of organisms to the physical environment. Why are we so vegetation biased? Plants don’t (really) move Long lifespans (slow turnover) A parade of biomes Climate diagram: A graph of average monthly temperature and precipitation at a location, showing the characteristic seasonal climate pattern. Axes are scaled so that 1°C (L) corresponds to 2 mm of precipitation (R). When the precipitation curve falls below the temperature curve, water availability limits plant growth. Tropical rainforests Tropical rainforests: –Between 10°N and 10°S –Abundant rainfall; may occur in one or two peaks associated with movement of the ITCZ –High biomass, high diversity—about 50% of Earth’s species –Light is a key factor—plants must grow tall or adjust to low light. Emergents rise above the canopy. Lianas (woody vines) and epiphytes use the trees for support. Understory trees grow in the shade of the canopy; shrubs and forbs occupy the forest floor. Tropical rainforests Getting too hot: –A paper published yesterday presents data that tropical forests are about 4°C warming away from a breakdown of photosynthesis in plant leaves. Tropical seasonal forests and savannas Tropical seasonal forests and savannas: –North and south of the wet tropics –Wet and dry seasons associated with movement of the ITCZ –Shorter trees, deciduous in dry seasons, more grasses and shrubs –Includes tropical dry forests, thorn woodlands, and tropical savannas –Fires promote establishment of savannas—grasses with intermixed trees and shrubs. –In Africa, large herbivores—wildebeests, zebras, elephants, and antelopes—also influence the balance of grass and trees. Less than half of seasonal tropical forests and savannas remain. Human population growth in this biome has had a major influence. Large tracts have been converted to cropland and pasture. Deserts Deserts: –At high pressure zones, 30° N and S –High temperatures, low moisture –Sparse vegetation and animal populations –Low water availability constrains plant abundance but diversity can be high. – Many plants have succulent stems that store water. Convergence is shown by cacti (Western Hemisphere) and euphorbs (Eastern Hemisphere). –Plants also include drought-deciduous shrubs, grasses, and short-lived annual plants that are active only after a rain.  Temperate grasslands: –Between 30° and 50° latitude –Warm, moist summers and cold, dry winters –Grasses dominate; maintained by frequent fires and large herbivores such as bison –High soil fertility Most grasslands of central N America and Eurasia have been converted to agriculture. In arid grasslands, grazing by domestic animals can exceed capacity for regrowth, leading to grassland degradation and desertification. Irrigation in some areas causes salinization.  Temperate shrublands and woodlands: –Between 30° and 40° latitude –Evergreen shrubs and trees –Mediterranean-type climates—cool, wet winters and hot, dry summers –Evergreen leaves: plants can be active during cool, wet winters; lowers nutrient requirements—plants don’t have to make new leaves every year. –Sclerophyllous leaves deter herbivores and prevent wilting. –Fire is common and helps maintain the biome. Without regular fires at 30- to 40-year intervals, shrublands may be replaced by forests Some temperate shrublands have been converted to crops and vineyards, but the soils are nutrient-poor. Urban development has reduced the biome (e.g., in southern California). More frequent fires reduce ability of the vegetation to recover, and invasive grasses can move in.  Temperate deciduous forests: –30° to 50° N, on continental edges with enough rainfall for tree growth –Leaves are deciduous in winter –Oaks, maples, and beeches occur everywhere in this biome –Species diversity is lower than tropical rainforests Fertile soils and climate make this biome good for agriculture. Very little old-growth temperate forest remains As agriculture has shifted to the tropics, temperate forests have regrown Shifts in species composition are due to nutrient depletion by agriculture and to invasive species such as chestnut blight..​.​  Temperate evergreen forests: –30° to 50° N and S, coastal, continental, and maritime zones –Temperate rainforests: high rainfall and mild winters; located on west coasts. –Lower diversity than tropical and deciduous forests –Leaves tend to be acidic, and soils nutrient-poor Evergreen trees are used for wood and paper pulp, and this biome has been logged extensively. Very little old-growth temperate evergreen forest remains. In some areas, trees have been replaced with non- native species in uniformly aged stands. Suppression of fires in western North America has increased density of forest stands, resulting in more intense fires when they do occur, and increases spread of pathogens and insect pests. Air pollution has damaged some temperate evergreen forests.  Boreal forests (Taiga): –50° to 65° N –Long, severe winters –Permafrost (soil that remains frozen year- round) prevents drainage and results in saturated soils –Trees are conifers—pines, spruces, larches— and birches –Cold, wet conditions limit decomposition in soils; soils have high levels of organic matter. –In summer droughts, forest fires can be set by lightning and can burn both trees and soil. –Peat bogs form in low-lying areas. Climate war ming may increase soil decomposition rates, releasing stored carbon and increasing greenhouse gas concentrations.  Tundra: –Above 65° latitude, mostly in the Arctic –Cold temperatures, low precipitation –Short summers with long days –Vegetation: sedges, forbs, grasses, low-growing shrubs, lichens, and mosses –Widespread permafrost Human settlements are sparse; this biome has the largest pristine areas on Earth, but human influence is increasing as exploration and development of energy resources increases. The Arctic has experienced significant climate change, with warming almost double the global average. Mountains Some mountain communities have no biome analogs. –Example: In tropical alpine zones, daily temperature change is greater than the seasonal variation. –Unique climate conditions results in vegetation that does not resemble tundra. Freshwater Biological Zones Streams and lakes connect terrestrial and marine ecosystems. They process chemical elements from terrestrial systems and transport them to the oceans. Freshwater biota are influenced by flow velocity light penetration temperature water chemistry Freshwater Biological Zones Streams and rivers are lotic (flowing water) systems. Smallest streams at high elevation are first-order streams. These converge to form second-order streams. Large rivers are sixth-order streams or greater. Streams develop a pattern of riffles and pools, which have different biological communities. Freshwater Biological Zones Benthic zone organisms are bottom dwellers; includes many kinds of invertebrates. Some feed on detritus (dead organic matter), others are predators. Some live in the hyporheic zone—the substratum below and adjacent to the stream. Freshwater Biological Zones River continuum concept: communities change along the length of a stream. –As streams increase in size, detritus from becomes less important as a food source; fine organic matter, algae, and macrophytes become more important. –Shredders that tear up and chew leaves give way to collectors that collect fine particles from the water. Freshwater Biological Zones Lakes and still waters (lentic ecosystems) occur where depressions in the landscape fill with water. Can be formed by glacial processes, river oxbows, volcanic craters, tectonic basins, or by damming streams. Deep lakes with small surface area tend to be nutrient-poor; shallow lakes with large surface area tend to be nutrient rich. Ephemeral ponds can be formed when logs, tree holes, plant leaves, or depressions in the ground fill with rain water. Freshwater Biological Zones Pelagic zone: open water; dominated by plankton (small and microscopic organisms suspended in the water). –Phytoplankton are photosynthetic; restricted to the photic zone. –Zooplankton are nonphotosynthetic protists and tiny animals. Littoral zone: near shore; the photic zone reaches the bottom; macrophytes occur here. Benthic zone: detritus from littoral and pelagic zones is food for animals, fungi, and bacteria; may be cold and have low oxygen. Marine Biological Zones Oceans cover 71% of Earth’s surface and have a rich diversity of life. Marine biological zones are categorized by their location relative to shorelines and the ocean bottom. Marine organisms are influenced by salinity, temperature, light, water depth, bottom substrate, and interactions with other organisms. Nearshore zones are influenced by local climate, tides, waves, and influx of fresh water and sediments from rivers. Tides produce unique transition zones between terrestrial and marine environments. Marine Biological Zones Marine Biological Zones Estuaries: where rivers flow into oceans. –Salinity varies as fresh water from the river mixes with salty water from the sea. –Rivers bring in terrestrial sediments and nutrients, contributing to the productivity of estuaries. –Juvenile stages of many fish species live in these protected environments. Marine Biological Zones Salt marshes: Shallow coastal wetlands dominated by grasses and rushes. –Terrestrial nutrients enhance productivity. –Tides produce salinity gradients that result in zones with different plant species. –Marshes provide food and protection for fish, crabs, birds, and mammals. Marine Biological Zones Mangrove forests dominate some tropical coastal zones. –Mangroves are salt-tolerant, evergreen trees and shrubs; the roots trap sediments. –They provide nutrients to other marine ecosystems and habitat for many animals; threatened by human development, particularly shrimp farms. Famous in ecology from the experiments of Dan Simberloff and E.O. Wilson (Biogeography unit) Marine Biological Zones Rocky intertidal zones provide a stable substrate for many organisms. –Sessile organisms must cope with wet and dry conditions and changing salinity as the tides rise and fall. –Mobile organisms can move into pools at low tide to avoid desiccation. Famous in ecology from the experiments of Bob Paine (Predators unit) Marine Biological Zones Shallow ocean zones: light penetrates to the bottom; sessile photosynthetic organisms support a diverse community of other organisms by providing energy and physical support. –Coral reefs –Seagrass beds –Kelp beds Rates of biomass production are some of the highest in the world.  Seagrass beds are submerged communities of flowering plants in subtidal marine sediments. –Algae and animals grow on the plants, and larval stages of many organisms use them for habitat. –Nutrients from agricultural activities can increase the algal growth in seagrass beds Kelp beds, or kelp forests, support a diverse marine community, including sea urchins, lobsters, mussels, abalones, many other seaweeds, and sea otters. –Kelp are large brown algae, with leaf-like fronds, stems, and holdfasts which anchor them to the bottom.  Deep benthic zones are sparsely populated –Temperatures near freezing; very high pressure. –Sediments are rich in organic matter. Sea stars and sea cucumbers graze the ocean floor or filter food from the water. –Bioluminescence is used by benthic predators to lure prey. Ancient Egypt Egypt Justin Yeakel, UC Merced Ancient Egypt Species Composition Most likely time of extinction Ancient Egypt Ancient Egypt Modelling Results Human Population Growth Initially: Very Stable Aridification Pulses Now: Very Fragile