Ecosystem Ecology 2: Biogeochemical Cycles PDF

Ecosystem ecology 2: Biogeochemical Cycles Learning goals Recognize decomposers as essential to nutrient cycling Recognize the major biogeochemical cycles and key steps in each Give examples of the ways humans have changed each major biogeochemical cycles, and the consequences for e...

Ecosystem ecology 2: Biogeochemical Cycles Learning goals Recognize decomposers as essential to nutrient cycling Recognize the major biogeochemical cycles and key steps in each Give examples of the ways humans have changed each major biogeochemical cycles, and the consequences for ecosystem functioning/human wellbeing Give examples of how biogeochemical cycles interact Recognize the role of biodiversity (populations/communities) in shaping the surrounding ecosystems Where does plant biomass come from? Air! (https://www.youtube.com/watch?v=2KZb 2_vcNTg) How? - Photosynthesis 6CO2 + 6H2O→ C6H12O6 + 6O2 Carbon glucose oxygen water dioxide Photo credit; Dr. Carly Ziter Cellulose Starch image credit; Lab star theory Lignin Comprehension question In a forest ecosystem, Which of the following best explains the role of decomposers in this process? A. In brown food web, decomposers are the secondary consumers B. Decomposers convert dead organic matter into small nutrients that enrich the soil C. The rate of decomposition is higher in colder regions D. Decomposers recycle energy and nutrients in the ecosystem Decomposition and nutrient cycling All energy fixed in primary production eventually becomes available to decomposers ; either as producer or consumer biomass Why decomposition important ? Photo credit; Dr. Eric Pedersen  Two groups; Detritivores; earthworms, beetles, crabs etc., and Decomposer-microorganism ;bacteria ,fungi Scavengers ; recyclers of the Honey Fungus Image credit ;Wikimedia commons, Stu's Images ecosystem Organic matter is broken down into carbon dioxide and the mineral forms of nutrients like nitrogen Dung beetle Image credit ;Wikimedia commons What happens to dead biomass? Decomposition is driven by both abiotic (chemical, physical) processes and biotic processes 1. Fragmentation 2. Leaching 3. Mixing 4. Microbial digestion Temperature, moisture, oxygen levels and nutrient availability determine the rate of decomposition Photo credit; Dr. Eric Pedersen  Tropic Rain forest o rapid decomposition o Relatively little amount of organic matter on the forest floor o 75% of nutrients in woody trunks Temperate forest o Slower decomposition o 50% of nutrients in the soil Cold and wet ecosystems; peatlands, o Store large amount of organic matter o Net primary production > decomposition Whale Fall Actively Devoured by Scavengers at Davidson Seamount | Nautilus Live https://www.youtube.com/watch?v=CZzQhiNQXxU Consequences of unbalanced work by decomposers ; Most of our pollution problems are linked to “nutrient” cycling © Vladimir Melnik/Adobe Stock Plastic is a polymeric material-molecules are very large, often Input of N and P > out put by decomposers resembling long chains made Image credit; Snohomish County Government Decomposers are not able to break down  Law of conservation of matter/mass Energy flows but nutrients cycle Atoms/molecules are not destroyed, but are rearranged and recycled Nutrients cycle Image credit: J. A. Nilsson\[^2\]  Major reservoirs of Nutrients Available Unavailable Biomass Fossil fuels Organic Fossilization Respiration Photosynthesis Decomposition Assimilation Excretion Formation of Inorganic Nutrients: sedimentary rock Minerals air, in rocks soil & water Weathering , Erosion Biogeochemical cycles Major biogeochemical cycles - Water - Carbon - Nitrogen - Phosphorus  Hydrological cycle/water cycle Link between terrestrial & aquatic systems Major drivers; evaporation of liquid water by solar energy Condensation of water vapor in to cloud and precipitation What is the water cycle powered by? Sun Campbell Biology, Anything we do on land affects Canadian Edition; aquatic ecosystems Fig 55.13  Human actions on Water cycle and consequences 1. Deforestation - Less plants ,less evaporation 2. Over abstraction of ground water Droughts, floods, water scarcity, and 3. Land use change the degradation of -expansion of agriculture and ecosystems pasture, growth of urban areas Question What is the largest reservoir of carbon ? A. limestone rocks B. Ocean C. Atmosphere D. Biomass  Carbon cycle Photosynthesis by plants and phytoplankton remove atmospheric CO2 vs. cellular Respiration by producers and consumers In and out C Quantity is almost equal Biggest reservoir is limestone rocks, but this turns over very slowly Linked to climate change Cause? - Burning 300 million yr old coal forests & other fossil fuels Ocean acidification: CO2 dissolves in Campbell Biology, Canadian Edition; Fig 55.13 water  Human actions on Carbon cycle and consequences Inflow of CO2 from human sources is not balanced by outflows. major source – fossil fuels Atmospheric carbon dioxide is now 50 percent higher than it was before the Industrial Revolution Climate change !!!! From: RealClimate.org, 2018: http://www.realclimate.org/index.php/archives/2018/01/the-global-co2-rise-the-facts-exxon-and-the-favorite-denial-tricks/ Latest CO2 reading: 423.26ppm(6.39AM,11/11/2024) (https://keelingcurve.ucsd.edu/) Gruber, N., Friedlingstein, P., Field, C. B., Valentini, R., Heimann, M., Richey, J. E.,... & Chen, C. T. A. (2004). The vulnerability of the carbon cycle in the 21st century: An assessment of carbon-climate-human interactions. The global carbon cycle: integrating humans, climate, and the natural world, 62, 45-76. https://www.researchgate.net/publication/258432144_The_vulnerability_of_t he_carbon_cycle_in_the_21st_century_An_assessment_of_carbon-climate- human_interactions Question Why is nitrogen fixation important for plants? a) It helps in the conversion of nitrogen gas into a usable form. b) It increases the nitrogen content in the atmosphere. c) It allows plants to convert nitrogen into Nitrate. d) It breaks down organic matter into nitrogen compounds.  Terrestrial Nitrogen cycle Root nodules in leguminous plants NH3 NH4+ Campbell Biology, Canadian Edition; Fig 55.13 Terrestrial Nitrogen cycle Unavailable What happens when we add fertilizer? Atmosphere Plants (by bacteria) Nitrates Nitrifying bacteria Nitrogen NH3 NH4+ Nitrites fixing soil bacteria  Nitrogen cycle Largest reservoir: the atmosphere Fixation: Turning atmospheric nitrogen (N₂) into a usable form, like ammonia (NH3/NH4+), done by soil bacteria or lightning. Nitrification: Converting ammonia into nitrites (NO₂⁻) and then nitrates ( NO₃⁻), again with the help of bacteria. Assimilation: Plants absorb these nitrates to build proteins and other vit al compounds. Ammonification: When plants and animals die, decomposers convert or ganic nitrogen back into ammonia. Denitrification: Denitrification bacteria convert nitrate to nitrogen gas, removing bioavailable nitrogen  Human actions on Nitrogen cycle and consequences Burning fossil fuels, application of nitrogen-based fertilizers, human induced N fixation activity has doubled the amount of global nitrogen fixation - Nutrient imbalance in trees, changes in forest health, and declines in biodiversity - Methemoglobinemia (Blue Baby Syndrome) – foods or drinking water high in nitrate (https://www.dhs.wisconsin.gov/water/blue-baby- syndrome.htm) - Toxic algal blooms What do you think might happen to nutrients when the watershed was clearcut? ? Campbell Biology, Canadian Edition; Fig 55.15  Minimal atmospheric phase Biggest reservoir is sedimentary Add fertilizers? rocks, released by weathering of rock (and now by mining) Main processes Weathering Absorption Consumption Decomposition Sedimentation Campbell Biology, Canadian Edition; Fig 55.13 Human actions on phosphorous cycle and consequences Prior to industrial agriculture: heavily recycled in ecosystems. Now: large amounts added to waters via fertilizers, agriculture & sewage + deforestation Eutrophication!!! https://www.youtube.com/watch?time_continue=1&v=mLbDbmmV6Qc&embeds_referri ng_euri=https%3A%2F%2Fhubblecontent.osi.office.net%2F&source_ve_path=Mjg2NjY  Biogeochemical cycles interact These cycles interact and influence each other in complex ways, helping to regulate Earth’s climate, ecosystems, and the availability of essential nutrients. 1. Carbon and Nitrogen Cycle Interaction in Plant Growth 2. Water and Carbon Cycle Interaction in Oceans 3. Nitrogen and Phosphorus Cycles Interaction in Algal Blooms 4. Carbon, Nitrogen, and Water Cycle Interaction in Soil Organic Matter The Role of Biodiversity in Shaping Ecosystems Ecosystem engineers Beavers Building Dams and Creating Wetlands Water Flow Regulation and Flood Control Enhancing Biodiversity Improve water quality Rewilding and Restoring Ecosystems Two sections of the River Utah, where the North American beaver is present on the left, and absent on the right. Credit: Stacy Passmore, “Landscape with Beavers,” Places Journal, July 2019 https://placesjournal.org/article/landscape-with-beavers/?cn-reloaded=1  Hippos Linking Aquatic and Terrestrial Ecosystems Nutrient Cycling and Fertilization Creating Habitats for Aquatic Life Modifying River Flow and Water Quality Food Source for Scavengers and Decomposers Image from Voysey, M. D., de Bruyn, P. N., & Davies, A. B. (2023). Are hippos Africa's most influential megaherbivore? A review of ecosystem engineering by the semi‐aquatic common hippopotamus. Biological Reviews, 98(5), 1509-1529. ; https://onlinelibrary.wiley.com/doi/10.1111/brv.12960  Salmons Nutrient Transport and Distribution Food source for Other Species Shaping River and Stream Habitats; When they spawn, salmon dig nests called “redds” in the gravel beds of rivers and streams. Impact on Plant Growth and Soil Health Tropical trees Evapotranspiration and Cloud Formation Create shady habitats Break winds Soil Temperature Regulation  Bioindicator species Mayflies, Stoneflies, and Caddisflies: sensitive to pollution Trout: Trout require clean, well-oxygenated water to thrive. Lichens: Lichens are sensitive to air quality, particularly sulfur dioxide and heavy metals Honey Bees: Bees are sensitive to pesticides, habitat loss, and pollution Bats: Bats are sensitive to changes in insect populations, pesticides, and habitat degradation Woodpeckers: Woodpeckers are indicators of forest health, as they rely on mature trees and deadwood.  Disturbance-intolerant taxa (green) Disturbance-adapted taxa (blue): Non-insects Line represents water discharge (Q) at each site Community composition change with the rate of water withdrawal Image credit; 2010 Nature Education Modified from Miller et al. (2007); Umatilla River, Oregon, USA https://www.nature.com/scitable/knowledge/library/bioindicators-using-organisms-to-measure-environmental-impacts- 16821310/#:~:text=Lichens%20and%20bryophytes%20serve%20as,of%20contaminants%20from%20the%20air.  Bioaccumulation biomagnification process by which toxic substances Increasing concentration of toxic accumulate in an organism's substances in organisms at each tissues over time. successive level of the food chain. Eg; methylmercury accumulation Eg; DDT  10x 4x 10x Banning of DDT in 1972 10,000x Course- BIOL 227 Lecturer – Semini Kushara Nawalage