Agroforestry tends to have higher Land equivalent Ratio (LER). Can you provide the main 5 reasons why?

Question

Land Equivalent Ratio in terms of biomass, e.g. there is more biomass in 2 ha of agroforestry, than the sum of 1 ha of agriculture and 1 ha of forestry.

Answer 1

One reason why mixing crops and trees can have higher productivity that growing them separately (and hence a higher land equivalent ratio(, is that the crop and trees are able to access different resources such as light and water.  This "central agroforestry hypothesis" was covered by a paper by Cannell et al. in 1996.  See the link below:

Central Agroforestry Hypothesis

Answer 2

The agricultural productive months are short for many cash crops in the temperate climates, resources like rain, sun, space, fertile components, CO2 are not productively used due to temporal constraints, eg Winter cold season, with AF you will Still make some use of those ressources, ideally creating some positive feedback loops, ultimately resulting in a higher LER.

Answer 3

In complement to the previous answers, it can be noted that agroforestry also has the potential to buffer extreme weather events, thus reducing the risk of crop failure. This is particularly important when considering climate change. Documented examples of this effect include:

- lower frost damage on grapevine in 2017 and 2021 (for 1 cultivar out of 2) in plots with pine trees, compared to nearby pure vineyard plot (Gosme et al 2022)

- better resilience to spring drought of a pea crop under walnut trees (Blanchet et al 2022)

However, this is not always the case (e.g. in 2021, there was more dammage in agroforestry one one of the cultivars, and in 2023, sorghum was not more resistant to spring drought in AF than pure crop, Bachakdjian et al in prep)

Blanchet, Guillaume, Karim Barkaoui, Mattia Bradley, Christian Dupraz, et Marie Gosme. « Interactions between drought and shade on the productivity of winter pea grown in a 25-year-old walnut-based alley cropping system ». JOURNAL OF AGRONOMY AND CROP SCIENCE, octobre 2022. https://doi.org/10.1111/jac.12488.

Gosme, Marie, Deslandes Florent, Delmotte, Sacha,  Bouisson Yvan, Gary, Christian et al.. Grapevine in agroforestry: impact of evergreen trees on water stress, yield and grape composition. World Congress on Agroforestry, Jul 2022, Québec, Canada. ⟨hal-04754427⟩