Sandstone Uplands (Wupatki) V1.

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Sandstone Uplands (Wupatki)

States

P1. Pre-eruption. Vegetation was likely shrub-dominated, with Ephedra viridis, Atriplex confertifolia being the best represented species in packrat middens in the Wupatki Basin in general (Ironside 2006). Grasses are a conspicuously absent component. Soil surface characteristics suggest potential for some degree of biological soil crust development. Soil crust may have been well-developed enough to decrease erodibility of the soil surface. A model based on the assumption that Wupatki soil surfaces are adequately rested, and therefore are at their potential regarding soil crusts [a questionable assumption], estimated potential cover of late successional crust elements at <>

P2. Post eruption and occupation. State P1 experienced two drastic changes which almost certainly led to rapid transitions. First the Sunset Carter eruption deposited up to several centimeters of volcanic ash and cinder possibly killing vegetation. Cinder deposition is thought to have improved water infiltration dynamics, and likely strongly altered hydrology (Sullivan and Downum 1991). Biological soil crust potential, previously low to moderate, would have been strongly constricted by locally varying amounts of cinder occupying soil surface area and reducing available habitat (Bowker and Belnap 2007). Within a few decades an approximately century-long occupation of dry-farming societies ensued. These are thought to have been abandoned due to declining soil nutrient stores (Sullivan and Downum 1991).

S1. Reference Shrubland/ grass component. After over 500 years of recovery from cinder deposition and impacts associated with occupation by agricultural societies, the ecosystem presumably recovered. There are no pre-grazing samples from Sandstone Uplands, however several packrat middens were analyzsed on shale uplands normally about 100m distant. Ephedra viridis, Atriplex canescens, and Fallugia paradoxa are especially well represented (Ironside 2006). The same evidence suggests that several grass species were primarily recent arrivals in the last 500 years, perhaps favored by the cinder deposition. The assumed grass dominance of “climax” communities in early soil and range site surveys is not supported by any other evidence (Doughty 1971).

S2. Denuded. Introduction of grazing would have reduced overall vegetation cover, and would tend to increase the relative abundance of unpalatable shrubs over more palatable grasses. Hoof action would increase erodibility by disruption of soil aggregates. Examination of times series photos seems to indicate that vegetation cover in some areas of the Wupatki Basin were markedly denuded around the turn of the 20^th century and well into that century (Unknown 1890-1920, Unknown 1905, Muench 1950-1970). Other historical photos indicate the loss of vegetation in the Wupatki area in general (e.g. Cedar Canyon, Antelope Prairie, Jameson 1962). Invasion by Salsola is possible and common, but no current evidence indicates that it is likely to be dominant.

Wukoki Ruin 1905. Area very close to ruin is unvegetated today, but photograph indicates very little vegetation in the landscape. The vegetation in the surrounding area has since recovered.

Heiser Spring 1890-1920. Unclear if animals are in a very large enclosure, or in open range. Corner of corral to left of bottom photo suggests they are not corralled.

S3. Post-grazing shrubland. Within the national monument, this is the typical state (Decoster and Swan 2009, Hansen and Thomas 2004) as grazing was reduced after the 1920’s and ceased, with the exception of occasional trespass, in 1989. We are uncertain as to whether this constitutes a separate state from S1. It is a shrubland with a grass component, with an overall species list not unlike S1. The primary difference seems to be the dominance of Artemisia filifolia, and the lower importance of Atriplex cancescens (Hansen and Thomas 2004, DeCoster and Swan 2009). Artemisia filifolia was not even detected in packrat middens near sandstone upland sites prior to grazing, whereas Atriplex canescens was the most commonly represented plant fossil (Ironside 2006). It is not known if this is a spatial artifact due to proximity of the middens to Deadman Wash, which is today richer in Atriplex. These midden locations average about 100m distant from Sandstone Uplands, thus this is plausible since this is near the upper limits of packrat foraging (Cinnamon 1988). However it is curious that the current dominant is not represented at all in nearby middens, while another cinder-loving species was well represented (Fallugia paradoxa). Doughty (1971) notes the presence of this species, but provides a community composition list (apparently ordered) topped by Chrysothamnus nauseosum and Ephedra in the early 1970s, possibly an earlier successional sere on the way to eventual Artemisia dominance. Current total cover is typically 5 – 10%, and it is not known if this is comparable to or lower than S1.

S4. Severely eroded. This state is largely theoretical, since most previously denuded areas seem to be vegetated today. If denudation and intense grazing pressure were to persist, and abiotic processes, e.g. erosion, dominated, then vegetation, soil fertility, and biotic activity would be unlikely to recover. Cinders help reduce runoff, but in the exposed soil surface, water-stable aggregation is very low, typically scoring in the lowest two categories using the Herrick soil stability test (Bowker and Belnap 2007). Doughty (1971) also indicates a greater erosion risk with overgrazing, and steeper slopes. Unchecked erosion would not allow establishment of vegetation, and the lack of vegetation would increase erosivity and erodibility, perpetuating erosion.

Transitions

T1: Cinder and deposition due to volcanism beginning in 1064 likely initially destroys much vegetation and biotic crusts, but enhances infiltration and water retention dynamics of soils. From ~ 1200 - 1300, agricultural societies practiced dryfarming, exploiting the properties of the cinder soils.

T2. Long term rest (centuries) allowed succession to proceed.

T3. Introduction of grazing reduces overall vegetative cover, proportionally reduces palatable herbage in favor of unpalatable vegetation. Animal vectors can facilitate Salsola invasion.

T4. Cessation of grazing allows recovery of vegetative cover.

T5? Shrubland succession proceeds arriving at original condition. [much uncertainty here regarding the distinctness of S1 and S3, proposed successional pathway is conjecture]

T6. Active erosion and poor hydrological control prevent reestablishment of vegetation, creating a positive feedback.

Useful indicators and rationale:

For the most part, the I&M program is monitoring the right indicators.
I1. Vegetative community structure. T3, T4, T5. Will help determine if current communities are dynamic or stable, and will help determine their trajectory if dynamic.

I2. Total vegetative and ground cover, and cover of bare gound. T3, T5, T6. Of the controls on erosion in this ecosite, only vegetation cover and its converse bare ground are likely to be dynamic. These would help detect grazing-induced changes in modifiers of erosivity, and dynamics in these variables after cessation of grazing (the current management scenario).

I3. Erosional features. T3, T4, T6. As stated above, when plant cover is sparse there is a greater probability of erosion. Detection/quantification of direct evidence of erosion, e.g rills, gullies, terracettes, pedestelling, scalding could be informative about advancement or cessation of these processes, especially in areas thought to be currently degraded. Wupatki-specific indicators may seek to detect coppicing-like behavior in the eolian redistribution of cinders.



Data Availability: Sparse
Ironside (2006) sampled post-occupation, pre-grazing packrat middens in Deadman Wash, mapped very near to or within Sandtone Uplands units.

Hansen, et al. (2004) created a classification of plant communities, and mapped them using remote sensing and ground truthing.

DeCoster and Swan (2009) summarizes the first years of the I & M program and contains the most purposefully collected dataset for Sandstone Uplands. Contains good information on vegetation structure and ground cover, but lacks data on erosional features (e.g. rills, gulleys, terracettes). There are 3 years of data but sites may all be in basically the same state, and not very dynamic.

Bowker and Belnap (2007) sampled biological soil crust cover, soil stability, and surface roughness on sandstone uplands assumed to be at potential condition.

Several photosets (Muench 1950-1970, Unknown 1936, Unknown 1890-1920, Euler 1936-1950, and Parke 1960-1970), provide a very incomplete image of what vegetation looked like at various time periods. Most photos are not focused on landscapes, but some information can be extracted.

Recommendations for I & M program:
Consider low intensity (perhaps one time only) sampling of key variables in plots outside of monument boundaries on Sandstone Uplands, which are still undergoing grazing. This will help confirm that the state-and-transition model is reasonable, and may provide a data-based confirmation of estimated threshold points in key monitoring variables.
Consider refining and implementing monitoring data which relate to dynamic surface erosional features, such as sand deposition, rills, gullies, pedestelling, scalding, and terracettes.


Literature Cited

Bowker, M.A. and Belnap, J. 2007. Spatial Modeling of Biological Soil Crusts to Support Land Management Decisions: Indicators of Range Health and Conservation–restoration Value Based Upon the Potential Distribution of Biological Soil Crusts in Montezuma Castle, Tuzigoot, Walnut Canyon, and Wupatki National Monuments, Arizona.

Cinnamon, S.K. 1988. The vegetation community of Cedar Canyon, Wupatki National Monument as influenced by prehistoric and historic environmental change. Master’s Thesis, NAU.

Doughty, J.W. 1971. Soil survey and range site and condition inventory. Wupatki National Monuments, Arizona. A special report. USDA SCS.

Hansen, M., J. Coles, and K. Thomas. 2004. Vegetation of Wupatki National Monument. U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Colorado Plateau Field Station, Flagstaff, Arizona. Final report to the USGS-NPS Vegetation Mapping Program.

Ironside, K. 2006. Climate change research in national parks; paeloecology, policy, and modeling the future. Master’s Thesis, Northern Arizona University.

Jameson, D.A. 1962. Effects of Burning on a Galleta-Black Grama Range Invaded by Juniper. Ecology 43: 760-763.

Meunch, J. 1950 – 1970. Photographs 1950-1970. NAU Digital Photo Archives.

Unknown. 1936. Wukoki ruin. NAU Digital Photo Archives.

Unknown. 1890 – 1920. People, Animals and activities at Heiser Spring near Wupatki National Monument, Arizona. NAU Digital Photo Archives.

Euler, RC. 1936 – 1950. Non-pueblo Indians: Navajo. NAU Digital Photo Archives.

Parke, H. 1960-1970. National Parks: Rainbow Bridge, Saguaro, Sunset Crater, Timpanogos Cave, Tonto, Tumacacori, Tuzigoot, Walnut Canyon, White Sands, Wupatki, Yellowstone, and Yosemite. NAU Digital Photo Archives

Sullivan, AP, Downum, CE. 1991. Aridity, activity, and volcanic ash agriculture: a study of short-term prehistoric cultural-ecological dynamics. World Archaeology 22: 271-287.