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Fig. 13.1 (a) Conceptual state-and-transition model for NRCS ecological site R028AY307UT
A. tridentata spp. wyomingensis growing on upland gravelly loam soils in Utah (Thacker et al. 2008 ).
The larger bold boxes represent vegetation states with the top (#1) being the reference state and
immediately below it (#2) the current potential state, which is similar to the reference with a non-
dominant presence of nonnative plants. States #3–5 represent undesirable states that are invaded
with J. osteosperma, Gutierrezia sarothrae (Pursh) Britton & Rusby (broom snakeweed), and inva-
sive annual grasses or forbs, respectively. The final (#6) state represents a nonnative but more
desirable vegetation community such as Agropyron cristatum (L.) Gaertn. (crested wheatgrass).
L. Provencher et al.