Sandy Loam Upland 12-16" p.z.

Description

The potential plant community on this site is dominated by warm season perennial grasses. All the major perennial grass species on the site tend to be well dispersed throughout the plant community. Perennial forbs and shrubs are minor on the site. The aspect is open grassland.

Characteristics and indicators

Native perennial grass basal cover ≥ 0.5%, large shrub (mesquite) canopy <5%, and succulent canopy <3%.

Submodel

Description

Non-native perennial grasses introduced from South Africa are well-adapted within this LRU. Once introduced to this site, the non-native perennial grasses will come to dominate when livestock grazing is not managed to ensure native perennial grass vigor. This State has two plant community phases.

Submodel

Description

Unmanaged or heavy livestock grazing impairs the perennial grass vigor and removes fuel loading for natural fire cycling. Large shrubs and cactus grow without the periodic reduction by burning. The open aspect is interrupted by large shrubs. The perennial grass community is diminished in diversity and basal cover.

Characteristics and indicators

Large shrub canopy >5%, median fetch* <20”, native perennial grass basal cover 0.5%, NN p.grass basal cover <1%; succulents may or may not be dominant, see CPs.

Submodel

Description

Large shrubs and non-native lovegrasses are co-dominant. Native perennial grasses may remain intact, generally under large shrub canopies. Non-native perennial grasses include African lovegrasses (most commonly Lehmann and Cochise lovegrasses) and, at the low and high elevations of this LRU, bufflegrass and yellow bluestem, respectively. The large shrubs are resistant to fire mortality and burning will not affect their removal from the plant community. Repeated burning or heavy grazing negatively affects the perennial grasses and puts the site at risk of excessive soil erosion. In these areas, mechanical brush management will likely result in transitioning the site to State 2, with a loss of native grasses, both their productivity and diversity.

Submodel

Description

Mesquite and other large shrubs have increased and are dominant with canopies greater than 5%. Native and non-native annual forbs and grasses, both cool and warm season, dominate the under-story. Snakeweed and burroweed cycle with climate, but both remain important in the plant community. Native perennial grasses are largely gone, due to the interactions of drought, fire and continuous, heavy grazing. Areas located close to mountains usually have higher soil cover of cobbles and gravel, thus, exhibit inherent soil and site stability. Hydrologic relationships have changed to increase the amount of runoff. Sandy loam upland in this State is at risk to transition to State 6 (Large Shrub, Eroded).

Characteristics and indicators

Large shrub canopy >5%, Median Fetch* >20”, perennial grass basal cover <1%, no evidence of active, accelerated erosion
*Fetch is distance from a point in any direction to nearest perennial plant base

Submodel

Description

The Large Shrub, Eroded State is very similar in structure to States 4 and 5 (mesquite dominated, half-shrub understory), however, the soil erosion threshold has been crossed; active, extreme soil loss (exposed argillic horizon, rills, pedestals, gullies) is occurring. Snakeweed and burroweed cycle with climate, but both remain important in the plant community. Native perennial grasses are largely gone, due to the interactions of drought, fire and continuous, heavy grazing. Remnant non-native lovegrasses may be present. Hydrologic relationships are permanently altered. Restoration practices can be applied to slow erosion rates and trap sediments; paired with prescribed grazing, non-native lovegrasses will colonize the site resulting in Plant Community 2.2, Cultivated Lehmann lovegrass Community.

Characteristics and indicators

Large shrub canopy >5%, Median Fetch* >20”, perennial grass basal cover <1%, active, accelerated erosion as indicted by water flow patterns, litter dams, and rills
*Fetch is distance from a point in any direction to nearest perennial plant base

Submodel