Here's my choice of species to analyze--I won't tell you why... Carex elynoides (#15) Carex scopularum (#17) Lewisia pygmaea (#40) Pentaphylloides floribunda (#58) Saxifraga rhomboidea (#62)
Hi,
Well, I couldn't wait for you to do the kriging of the environmental factors for me. I wasn't able to figure out how to properly krige the environmental factors, so I just used library akima in R to interpolate. The pdfs I've included are interpolations of each of the factors. AV is aspect value--low values face toward the SW and are hot, while high values face NE and are cool. Snow Depth is what it says, but in the alpine it is an indication of water availability. Sand is the fraction of the soil that falls in the sand fraction, i.e., it is a measure of how coarse the soil texture is. This also is related to water availability, since coarser soils usually dry out faster.
So how do things match out? #15 is Carex elynoides, a species that is supposed to be found where snow is relatively low. I think there is a rough match between the kriged plot for the species and low snow levels. This is a bit circular, since snow was based on species presences! However, C. elynoides wasn't the only species used for this calculation, so it's not completely circular.
#17 is Carex scopularum. This tends to be found in wetter areas. The Sand plots shows a minimum near the C. scopularum maximum, showing fine soils which hold water better. So this was expected. There also appears to be higher snow here, which would make it wetter. So this was also expected.
#40 is Lewisia pygmaea. This species is supposed to like gravelly soils. In fact, it reaches a max in sandy areas. There also appears to be high snow here--in fact, I remember seeing snowbanks in that region when I sampled. So this may be a species which likes it both wet and coarse-textured, which is an unusual combination and may account for its rarity. So the sandiness was expected, but the snowiness was not. (On the other hand, maybe the snowmelt washes out the finer soil fractions).
#58 is Pentaphylloides floribunda. This is a woody semi-shrub (i.e., a very small shrub), so this is an unusual lifeform for the alpine, where most species are non-woody. It appears to like cooler aspects. This was unexpected.
#62 is Saxifraga rhomboidea. It, in contrast to P. floribunda, appears to like hot aspects. This was also unexpected.
So from a biological viewpoint, this is quite interesting. As you might expect, I would *love* to have other species undergo the "magic kriging." I would also love to have have the environmental factors kriged so those data are more comparable to the lovely smooth species data.
Rick
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================================= Richard L. Boyce Department of Biological Sciences Northern Kentucky University Nunn Drive Highland Heights, KY 41099 USA 859-572-1407 (tel.) 859-572-5639 (fax) boycer@nku.edu http://www.nku.edu/~boycer/ =================================
"One of the advantages of being disorderly is that one is constantly making exciting discoveries." - A.A. Milne