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Clemson FOR 2060 - Litterfall
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FOR 2060 1st Edition Lecture 6 Outline of Last Lecture I. PhotoautotrophsA. Photosynethic Efficiency B. SaturationII. Gross Primary Production A. RespirationB. Net Primary Production Outline of Current Lecture III. Why Are Forests Less Grazed Than Other Ecosystems?IV. LitterfallA. Aboveground LitterfallB. Belowground LitterfallV. Detritivores A. Detritus B. The Detritus Food Web C. Saprotrophic Organisms D. Assimilation Efficiency E. ComminutionVI. What Factors Control the Decomposition of Litter?A. Litter Quality B. TemperatureC. Soil MoistureD. Soil pH Current LectureIII. Why Are Forests Less Grazed Than Other Ecosystems?In a grassland ecosystem, the NPP is available to whoever needs it since it is close to the ground;however, the high quality NPP in a forest is out of reach. In a forest ecosystem you have a lot of woody tissues, which are not very palatable to grazers. The leaves also have tannins and are of alow nutritional value. The exception to forests being less grazed is when there are insect outbreaks and the large number of insects consume all of the leaves. IV. LitterfallThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Litterfall is the greatest loss of forest NPP. Litterfall is the regular annual transfer of living plant material to nonliving organic matter of the forest floor and mineral soil. Up to 75% of NPP becomes litterfall. Examples of aboveground litterfall are leaves falling to ground and branches falling to the ground. Aboveground litterfall generally increases as you move from the poles to the equator. The longer the foliage is retained on the tree, the less the quantity of the litterfall. In high latitude forests the trees are mostly evergreen so there is very little litterfall. Belowground litterfall examples include fine roots being broken down. Up to 67% of total NPP can go to the fine roots and mycorrhizal fungi. V. DetritivoresDetritivores are heterotrophs that obtain energy and nutrients by consuming detritus, which id defined as decomposing plant and material, as well as fecal matter. Without detritivores, production would grind to a halt because no nutrients would be released from the broken downwaste products. The detritus food web is very important. Litterfall is a major energy source for saprotrophic organisms (decomposer) in the detritus web. This food web also receives input from the grazer web through the death and decomposition of primary, secondary, and tertiary consumers. There is a low assimilation efficiency of primary, secondary, and tertiary consumers. Assimilation efficiency is the energy ingested when something is eaten. The assimilation energyis never 100%. Detritivores are any organisms that consume detritus. Most of them are small, unseen organisms but they can also be vultures and other larges animals. Comminution is when a large object is broken down into smaller pieces. This increases the surface area and allows smaller organisms to come in and continue to break down the detritus. VI. What Factors Control The Decomposition of Litter?Litter quality refers to the ratio of carbon to nitrogen. High quality litter has a low amount of nitrogen and low quality litter has a high amount of nitrogen. The more nitrogen you have the faster you will decompose. Bacteria and fungi are the main decomposers and bacteria are more efficient than fungi at breaking down most litter. However, bacteria cannot break down woody litter so only fungi can break down woody litter. Woody litter has a high carbon to nitrogen ration and a high lignin content. They can only be metabolized by fungi since they possess the enzymes for breaking down lignin. Temperature also effects the decomposition of litter. There is an optimum temperature, about 30C, at which the microbes are effective at breaking down the litter. However, once thetemperature gets too high enzymes begin to denature and the microbes are unable to decompose the litter. Soil moisture is also important for decomposition. As moisture increase so does the decomposition rate. There is an optimum amount of moisture so once you get to a certain moisture there is too much water and not enough oxygen, hence the decomposition rate decreases after the optimum point. Soil pH also plays a role in decomposition. There is a slower decomposition rate at high and low pH. You need a near neutral soil pH in order to have a high rate of decomposition because bacteria and fungi thrive in neutral pH. The highest microbial biomass occurs between pH 5.8 and


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Clemson FOR 2060 - Litterfall

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