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Emergy evaluations of and limits to ...

Doherty, Steven James.

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Emergy evaluations of and limits to forest production.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Emergy evaluations of and limits to forest production./
作者:	Doherty, Steven James.
面頁冊數:	215 p.
附註:	Chairman: Howard T. Odum.
Contained By:	Dissertation Abstracts International57-02B.
標題:	Agriculture, Forestry and Wildlife. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9618686

Emergy evaluations of and limits to forest production.
Doherty, Steven James.

Emergy evaluations of and limits to forest production. - 215 p.

Chairman: Howard T. Odum.

Thesis (Ph.D.)--University of Florida, 1995.

Temperate and tropical forest systems in Sweden, Puerto Rico and other areas, ranging in age from 5 and 300 years, were evaluated with energy systems methods to investigate net yields, economic requirements, and limits of biomass production from solar energy. Inputs and products were measured on a common basis in units of solar emergy (solar emjoules--the solar energy required directly and indirectly to produce a product or service). Forest growth and harvested biomass, were compared along with water supply, reforestation, pulp, paper, and recreational use.Subjects--Topical Terms:

783690
Agriculture, Forestry and Wildlife.

Emergy evaluations of and limits to forest production.
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100 1 $a Doherty, Steven James. $3 1256827
245 1 0 $a Emergy evaluations of and limits to forest production.
300 $a 215 p.
500 $a Chairman: Howard T. Odum.
500 $a Source: Dissertation Abstracts International, Volume: 57-02, Section: B, page: 1345.
502 $a Thesis (Ph.D.)--University of Florida, 1995.
520 $a Temperate and tropical forest systems in Sweden, Puerto Rico and other areas, ranging in age from 5 and 300 years, were evaluated with energy systems methods to investigate net yields, economic requirements, and limits of biomass production from solar energy. Inputs and products were measured on a common basis in units of solar emergy (solar emjoules--the solar energy required directly and indirectly to produce a product or service). Forest growth and harvested biomass, were compared along with water supply, reforestation, pulp, paper, and recreational use.
520 $a Net energy yields increased with length of growth cycle, ranging from 1.5 for plantations to more than 12 for unmanaged forests with economic investments as much as ten times greater for managed systems. Preparing biomass for conversion to electricity required greater emergy inputs than was required for processing fossil fuels. Emergy yield ratios for natural gas and coal-fired were between 3 and 6 and less than 2 for wood-fired electricity.
520 $a Solar transformity, a measure of emergy used per unit energy produced, for above ground biomass production was less than 10,000 sej/J (i.e., solar emjoules per joule) and between 100,000-200,000 sej/J for electricity. The lowest value in each category may approach the most efficient conversions thermodynamically possible consistent with operation at maximum production. In Puerto Rico, reforestation using plantations (34 years) and exotic invasions (50 years) minimized economic requirements and increased net yields.
520 $a Emergy yield is inherently dependent upon growth time for biomass systems. Sustainable long-run forests which rely on flow limited, renewable emergy often exhibited greater net production than managed short rotation forests, yet net biomass production is often smaller because more is reinvested to design and maintain diverse structure and autogenic pathways. Although technology may increase energy conversion efficiencies, additional investments reduce net yields below currently available primary sources.
520 $a Because of energy conversion and temporal limits to biomass production, agroforest systems cannot currently compete with fossil-carbon fuels, until nonrenewable sources become limiting, lowering net yields for all existing fuels. Human carrying capacity would be less than half its current size and a general slowing of global economies would be necessary if only renewable fuel sources were available.
590 $a School code: 0070.
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710 2 0 $a University of Florida. $3 718949
773 0 $t Dissertation Abstracts International $g 57-02B.
790 $a 0070
790 1 0 $a Odum, Howard T., $e advisor
791 $a Ph.D.
792 $a 1995
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9618686