RS and N (no weeds)

Canopy nitrogen, carbon assimilation, and albedo in
temperate and boreal forests: Functional relations
and potential climate feedbacks
S. V. Ollinger, et al.

Another remote sensing paper, and it continues on with my recent readings in foliar nitrogen. The researchers use AVIRIS (and a little Hyperion, where necessary) to estimate foliar nitrogen levels over a few landscapes in temperate/boreal forests scattered over Canada. I received this paper after emailing S. Ollinger himself about some AVIRIS work he's doing, and he graciously sent me this along with a few thoughts... but back to the paper. They found a strong relationship between measured foliar N and reflectance across most of the NIR spectrum- cool, because that means you can get foliar N estimates from other (read: free) sensors. To quote directly:

"Collectively, these results suggest that we already have a basis
for detecting variation in %N and CAmax of forest canopies at
continental scales by using scaled relationships with albedo
and/or simple measures of NIR reflectance obtained during the
peak period of the growing season."

Then, they tie the N measurements to carbon fixation, using flux towers (through BOREAS sites I assume; I believe that's where the imagery is). All well and good.

My thoughts, to tie into the previous post, are about using this foliar N to potentially address biodiversity levels, potential for invasion, and perhaps even invasion monitoring (I don't know a lot of biogeochemistry, so hopefully I don't say something dumb at this point, but I'll try anyway). Would higher biodiversity sites (in the understory: say vascular plants, or invertebrates, or whatever) also have higher foliar N in the overstory? I would imagine so, given simple things like nutrient availability, more potential niches, etc. Would invasive species be reflected in the overstory N (either via nitrogen fixation themselves, like Scotch broom or sea buckthorn, or by exclusion of other nitrogen fixing plants, see previous post)? To speculate further (what fun!), what would the edge of higher nitrogen zones look like? If you look at the map in the paper, there's a lot of heterogeneity in the foliar nitrogen levels across forests- so... could any sort of meta-population/meta-community dynamics be happening across that edge?