方法对比

	Land Equivalent Ratio	On-Farm Agrobiodiversity Index
领域	Food Agriculture Studies	Food Agriculture Studies
方法族	Process / pipeline	Process / pipeline
起源年份	1980	2008
提出者	Roger Mead & Roger W. Willey	Devra Jarvis & colleagues (on-farm crop-variety diversity framework); diversity indices after Magurran
类型	Descriptive index of relative land productivity	Descriptive diversity-index pipeline for cultivated and reared diversity on farms
开创性文献	Mead, R., & Willey, R. W. (1980). The Concept of a 'Land Equivalent Ratio' and Advantages in Yields from Intercropping. Experimental Agriculture, 16(3), 217-228.	Jarvis, D. I., Brown, A. H. D., Cuong, P. H., Collado-Panduro, L., Latournerie-Moreno, L., Gyawali, S., et al. (2008). A global perspective of the richness and evenness of traditional crop-variety diversity maintained by farming communities. Proceedings of the National Academy of Sciences, 105(14), 5326-5331.
别名	LER, Relative Yield Total, Land Equivalent Coefficient, Intercropping Land-Use Efficiency	On-Farm Crop Diversity Index, Agrobiodiversity Index, Farm Varietal Diversity Index, Cultivated Diversity Index
相关	4	4
摘要	The land equivalent ratio (LER) is the standard index for judging whether intercropping — growing two or more crops together on the same land — uses land more efficiently than growing each crop separately. Formalized by Roger Mead and Roger Willey in 1980, the LER expresses how much land would be required under sole cropping to produce the yields achieved by one unit of intercropped land. It is computed by dividing each component crop's intercrop yield by its sole-crop yield and summing these partial ratios across all components. An LER greater than one means the intercrop is more land-efficient than the corresponding sole crops, and the amount above one quantifies the land saved, giving agronomists a simple, interpretable, and widely used measure of the biological advantage of mixed cropping.	The on-farm agrobiodiversity index applies the mathematics of biological diversity — richness, evenness, and combined indices such as Shannon, Simpson and Margalef — to the crops, landraces, varieties and livestock breeds that farmers actually maintain in their fields and herds. Rather than counting wild species in an ecosystem, it quantifies cultivated and reared diversity: how many distinct crop species and varieties a farm grows, how evenly the area or production is spread across them, and how this compares between farms, communities and regions. Devra Jarvis and a large international team showed in 2008 that these measures of richness, evenness and divergence reveal substantial crop-variety diversity still maintained on farms worldwide and provide a sound basis for indicators of on-farm conservation. Built on Magurran's standard diversity formulas, the index turns agrobiodiversity into measurable, comparable numbers for research and policy.