We previously talked about the fact that several of the 16 ecosites probably behave very similarly and that S&T models will likely be very similar in these cases. Perhaps critical threshold values will differ a bit but the structure of the models will look really similar.
I see the following groupings. I know Mark also went through this exercise, I wonder if we came up with something similar?
1) Deep sandy, soil grasslands:
All have the potential to be dominated by widely spaced (~0.5m usually) taller bunchgrasses whose filamentous root structure favors accessing water via capillary action. All are susceptible to annual invasion, though because desert sand is Navajo derived, it may be less of an issue there.
Desert sand (sand sagebrush),
desert sandy loam (4-wing saltbush),
semi-desert sand (4-wing saltbush),
sandy loam upland (Chaco),
sandy loam upland (pet forest)
2) Shallow sandy shrublands-woodlands:
Usually a thin layer over sandstone bedrock, may or may not have an overstory of P-J, has understroy of colegyne. cattle access to water sources or shade may impact these areas but annualization is probably not an issue.
desert sandy shallow loam
semi-desert shallow sandy loam.
3) Limey Upland:
due to unique history of Wupatki (volcanism, agriculture), this should be dealt with separately.
4) Sandstone Upland:
ditto for this.
5) Clayey fan:
This seems like a highly productive grassland over a somehwhat salty fine textured soil. Seems unique in this set of ecosites.
6) Skeletal rocky soils, saline:
These are common on gravity deposited slopes, or ancient alluvial deposits, normally occupied by shadscale. These two ecosites seem to differ mainly in slope.
semi-desert stony loam (shadcale)
semi-desert very steep stony loam (shadscale)
7) Semi-desert alkali sandy loam:
Deep salty soils, usually in basins, dominance by saltgrass and greasewood. Greasewood, I think is a phreatophyte, could be suceptible to Tamarix invasion maybe?? Seems unique in the ecosite set.
8) Mature Pinyon juniper woodlands:
the only problem i see with grouping these is that fire cycles are poorly known for P-J and a bit controversial.
Mesa tops and shoulders (Bandolier)
Shallow Loamy mesa tops (Mesa Verde)
What do you think???
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17 years ago
Looks good to me - pretty similar to how I grouped them. One addition to the deep sandy soil grasslands is the Semidesert Sandy Loam (4-wing) site. The Desert Sandy Loam - Semidesert Sandy Loam also can be considered a xeric - mesic gradient. These two also have been lumped in the new Cany soil survey update.
ReplyDeleteFor this deep grassland group, one consideration is that along a N-S latitudinal gradient, water erosion becomes increasingly important due to increasing relative contribution of high-intensity monsoonal precip.
The Semidesert Alkali Sandy Loam is structurally similar to the nonalkali version, but has major truncation issues (higher risks of water-driven erosion) due to occurrence on old alluvial surfaces with stratified soils including fine-textured lenses (I think - based on one field visit).