Tree crops can uplift soil nutrients from deeper in the soil profile, redistribute them to the surface via leaf litter, and therefore reduce nutrient losses from leeching in agricultural systems. Does anyone know of any studies that quantify this effect? It will obviously depend on the soil type, nutrient availability, tree species, etc., but Iʻm curious if people have tried to look at the effect in a highly quantified way (i.e. what density of tree plantings is ideal in a cropping system to promote adequate uplift to then be cropping annuals around the trees). I understand that the variability of the effect will be huge and complex, but there is an ancient cropping system that I am trying to wrap my head around how to examine and discuss the long term effects. Is there a stable isotope signature or ratio that might be useful in understanding long term cumulative effects?
Hello! Perhaps one or more of the following research articles (or references therein) might be of some interest to you:
Soil Organic C and Nutrient Contents under Trees with Different Functional Characteristics in Seasonally Dry Tropical Silvopastures* (CASALS et al., 2014)
(*) = A PDF copy of this research article is available on “Google”, posted by one of the co-authors, Graciela M. RUSCH, under the aforementioned title.
The Influence of Strata on the Nutrient Recycling within a Tropical Certified Organic Coffee Production System (MAMANI-PATI et al., 2012)
http://downloads.hindawi.com/journals/isrn/2012/389290.pdf
Spatial Variability of Nutrient Stocks in the Humus and Soils of a Forest Massif (Fougères, France)
[LEGOUT et al., 2008]
http://hal.archives-ouvertes.fr/docs/00/88/41/51/PDF/hal-00884151.pdf
The Uplift of Soil Nutrients by Plants: Biogeochemical Consequences across Scales (JOBBÁGY and JACKSON, 2004)
http://gea.unsl.edu.ar/pdfs/Jobbagy_Ecol_%202004.pdf
Plant Soil Interactions in Multistrata Agroforestry in the Humid Tropics (SCHROTH et al., 2001)
http://www.css.cornell.edu/faculty/lehmann/publ/AgroforSyst%2053,%2085-102,%202001%20Schroth.pdf
Aloha. Thank you! These articles, especially collectively, are very useful. Is this something you work on, or just happen to have the papers for?
You are quite welcome. I'm pleased to have been of some assistance.
Thanks Again Mei-Ling. I did finally get to read these papers. However, I am looking for something more rigorous. We all know that trees lift up nutrients from the ground, and deposit them on the soil, which can be reabsorbed. These paper tend to quantify the deposition of nutrients. However, this is really just scratching the surface of that I am after.
I am really after some of the partitioning of where the nutrients come from and go to. Think of a two tiered agroforestry system, with a larger, deep rooted plant and a smaller shallow rooted annual crop. The trees can lift nutrients from shallow in the soil, or deep in the soil. When they redeposit their nutrients to the surface those nutrients can be taken up by the trees again, or by the crops, or leeched out of the system. In this two tier system ideally what we would like is that the trees uplift nutrients from deep in the soil, and when they are deposited they are primarily take up by the annual crops. So the trees are powering the more rapid harvest.
I have been looking for more intensive studies that attempt to partition the nutrient sources and pathways, but it doesnʻt not seem like any work has been done to this effect. I am planning to study it in some very simple systems in Hawaii, where the "deep" soil is all unweathered basalt and the "shallow" soil is virtually purely organic soil derived from uplift. The isotope partitioning, I believe, should be strong enough to start to identify sources and fates of the nutrients. I would love to hear feedback on this concept from anyone!
Again, you are quite welcome. I wish you much success in this intriguing line of research.
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