Hi to all!
If the "loss to drainage waters" (see table at p. 1443 of Street-Perrot and Barker, 2008) is clearly major for forest ecosystem (i.e. coniferous forest = 26 kg Si ha-1 yr-1), why speculate about a possible role for grassland (a max of 11 kg Si ha-1 yr-1) in enhancing silica input to rivers?
I'd like to have your opinion about.
Thanks,
Luca
Sorry, for perhaps an uninformed response and for not reading your citation. I had not heard that silicon was an important benefit to surface waters, so I will have to become more informed on this. Regardless, pine forests tend to have more acidic needles than grassland vegetation, so it may have something to do with that. The amount of silicon is also probably related to the parent materials (geology and soils) and the total loading related to the rate of flow and chemical decomposition or weathering through these systems. Generally, the more acid condition wins, favoring the coniferous forests. So it may be something different, but I would look into the pH differences and perhaps buffering capacity, if soils, geology, water levels, topography, climate, etc. are the same to try to identify why grasslands and coniferous forests are different. If higher silicon is desired in streams, perhaps that may be one benefit of pine forests. More acid in low buffered waters may also mean some negative effects as increased solubility of aluminum, which is hard on some fish species. Nonetheless, the water quality interactions you suggest from land use is a very viable field of study. There are many things yet to learn on how we might manage and conserve the resources for improved benefit.
Thank you so much for your opinion Mr. Hansen! However, Poaceae are among the largest silica accumulators and grasslands constitute 40% of land surface...
If we take a look to the interesting article of Kidder & Gierlowski-Kordesch (2005) about the relationships between grassland radiation and silica cycle, we can read: "Grass-dominated ecosystems PROBABLY release silica more readily than forest ecosystems" "Silica recycling in grasslands appears to be considerably less efficient than in forests, based on both EMPIRICAL and theoretical considerations."
If you consider table 1 from Street-Perrott & Barker (2008) these considerations are difficult to accept: recycle in grasslands is near to steady-state while in forest no; loss to drainage in forest is always bigger than grasslands.
What do you think about?
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