Forest Ecology and the Forest Ecosystems - Northern ：森林生态学和森林生态系统-北[精品].ppt

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2018-04-25 发布于湖北
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Forest Ecology and the Forest Ecosystems - Northern ：森林生态学和森林生态系统-北[精品].ppt

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Forest Ecology and the Forest Ecosystems - Northern ：森林生态学和森林生态系统-北[精品]

Components of Healthy Ecosystems/Ecosystem Management Wally Covington Ecosystem Studies Ecosystem studies based on general systems principles focus on the movement of energy, nutrients, water, organisms, etc. through landscape units called ecosystems * An ecosystem:What is it? Size? Can be as large or small as needed to fit the purpose of study A single leaf A forested stand A watershed Hierarchical units * Definitions: Watershed: topographically defined unit of land, all precip. flows out of a single stream Stand: any area of forest vegetation whose site conditions, past history, and current species composition are sufficiently uniform to be managed as a unit A watershed can have many stands * Ecosystem Study Examples – Hubbard Brook Ecosystem-level study of a forested watershed Hubbard Brook Valley; Durham, NH Six small watersheds with similar geology, soils, and vegetation * Ecosystem Study Examples – Hubbard Brook Watershed: topographically defined unit of land, all precip. flows out of a single stream Monitor: precipitation in (rain gauges) streamflow out (weir) nutrients in: Plants, soil, and those lost in water * Ecosystem Study Examples – Hubbard Brook 1. Study paired watershed-ecosystem before a disturbance 2. Then disturb the system (In this case, forest harvesting practices such as a clear-cut = treatement) 3. Compare inputs and outputs before and after (or use “paired watersheds” – one disturbed, other not) 4. Differences in water, nutrients, etc. – due to the treatment * Organic Budgets/Nitrogen Cycle Very different in deciduous vs. coniferous forests Decomposition – (therefore, release of nitrogen in ionic form) is often faster in deciduous forests Coniferous trees need less nitrogen/decomposition is often slower Fire can be important in mobilizing nitrogen * Computer Models:Central to Ecosystem Management Need computer models: Complexity of forest ecosystems Complexity of management decisions * What is a model? Model = an abstra