Managers of the Prescott National Forest are obliged to evaluate the conditions of watersheds under their jurisdiction in order to guide informed decisions concerning grazing allotments, forest and woodland management, restoration treatments, and other management initiatives. Watershed condition has been delineated by contrasts between “good” and “poor” conditions (DeBano and Schmidt 1989). Good condition is characterized by vegetation and litter cover that is capable of absorbing precipitation, temporarily storing it, and slowly releasing it through a network of channels with minimal drainage density. Poor condition applies to areas where precipitation induces soil erosion and rapid sediment-laden runoff through an expanding network of channels. Evaluations of watershed condition face substantial challenges in attempting to determine a reference condition, the extent of departure from that condition, causes of that departure, and management actions that can return the watershed back toward the reference condition (McCammon and others 1998). These challenges are particularly great in watersheds of the arid and semi-arid Southwest, where flashy, sediment-laden runoff is a common natural condition.
Channel morphology has become an increasingly important subject for analyzing the health of rivers and associated fish populations, particularly since the popularization of channel classification and assessment methods. Morphological data can help to evaluate the flows of sediment and water that influence aquatic and riparian habitat. Channel classification systems, such as the one developed by Rosgen (1994) provide a useful shorthand for summarizing key morphological attributes of a river system. Accordingly, researchers have hypothesized that channel classifications could explain variation in native fish populations in rivers of the Southwest (Rinne and Neary 1997; Rinne 2005). Rosgen’s (1996) full methodology encompasses several levels of analysis arranged hierarchically from a general characterization of a stream basin to detailed measurements of channel change in specific reaches. The second and most popular level (Level II) of the Rosgen (1996) methodology provides a framework for categorizing stream reaches based on channel form and dominant substrate. While this classification is useful for describing variations in channel morphology, critics argue that it is less useful and perhaps even misleading for making inferences about channel condition and processes of development (Miller and Ritter 1996).
Streamside environments are inherently dynamic, yet streamside vegetation plays a key stabilizing role on riparian and aquatic habitats (Van Devender and Spaulding 1979; Van Devender and others 1987). Because of its dynamism, streamside vegetation is rarely the subject of classification analyses, yet it is a focal point for land managers regulating land uses, such as livestock grazing, that could potentially impact aquatic communities (Brown and others 1979). Livestock grazing along the UVR has been a politically charged issue, with recent years (1998 to present) witnessing a removal of livestock from the river corridor under Prescott National Forest management. However, livestock still graze on private lands, with some strays roaming onto State and Forest lands (see Chapter 2). During the same period, researchers observed declining populations of native fishes in the UVR, largely attributable to predation by introduced fishes (see Chapter 9), as well as to vast growth of woody plants post-1993 floods (see Chapter 2), and lateral erosion of historical terraces. Concomitantly, researchers have suggested that increases in woody streamside vegetation might be related to the cessation of livestock grazing (Rinne and Neary 1977; Neary and Rinne 1998, 2001a) as well as to other hydrological factors (see Chapter 2).
The largest wildfire in Arizona history damaged many important springs and wetlands on the western half of the White Mountain Apache Reservation in the summer of 2002. With support through the Burned Area Emergency Rehabilitation plan for the fire, we conducted assessments of dozens of these wetland sites. Two large wet meadows, Swamp Spring and Turkey Spring, were eroding rapidly in the wake of post-wildfire floods. The erosion was not only sending great volumes of ancient wetland soils to downstream rivers, but the downcutting of the stream channels threatened to leave both meadows so high and dry that they would no longer support culturally important wetland plants and wildlife. We surveyed the sites to evaluate the rate and the depth of the erosion. Several characteristics of the sites rendered them particularly vulnerable to post-fire damage: the steep topography of their surrounding landscapes, sandy soils, overuse of soil-binding vegetation by ungulates, and roads with poor drainage designs in the riparian zone. We designed a suite of restoration treatments to restore the wetlands, including rock riffle structures to regain channel stability, revegetation with sedges and reeds to stabilize the soils, fencing to exclude ungulates, and road rehabilitation measures. We collected plants from Swamp Spring and a wetland near Turkey Spring to grow off-site for eventual transplantation. The lessons learned from these sites will help to guide future wetland protection and restoration efforts on the Reservation and in other severely burned areas.
A complex geologic history has shaped the distribution of Arizona willow (Salix arizonica Dorn) and the Mogollon paintbrush (Castilleja mogollonica Pennell). These subalpine plants do not appear to be strict substrate specialists, but they do seem to favor coarse-textured and well-watered soils. Most of their occupied habitats were shaped by Quaternary glaciations, but are ultimately derived from felsic substrates formed before the Pliocene period. Populations of Arizona willow have been identified in the White Mountains of Arizona, the High Plateaus of Utah, and in the Southern Rocky Mountains of New Mexico and Colorado. Species closely related to the Mogollon paintbrush also occur in the Utah plateaus and the Southern Rocky Mountains. Genetic dissimilarity among these populations suggest that these taxa likely share an evolutionary history that extends into the Neogene, when tributaries of the ancestral Colorado River connected young volcanic highlands on the margins of the Colorado Plateau. This history points to the likelihood of additional populations of Arizona willow in the San Juan Mountains, and it suggests that these plants have survived dramatic changes in their environments. These patterns demonstrate the value of analyzing geology at a detailed level when interpreting habitat preferences and distributions of rare species.
Reconstructions of dry western US forests in the late 19th century in Arizona, Colorado and Oregon based on General Land Office records were used by Williams & Baker (2012; Global Ecology and Biogeography, 21, 1042-1052; hereafter W&B) to infer past fire regimes with substantial moderate and high-severity burning. The authors concluded that present-day large, high-severity fires are not distinguishable from historical patterns. We present evidence of important errors in their study. First, the use of tree size distributions to reconstruct past fire severity and extent is not supported by empirical age-size relationships nor by studies that directly quantified disturbance history in these forests. Second, the fire severity classification of W&B is qualitatively different from most modern classification schemes, and is based on different types of data, leading to an inappropriate comparison. Third, we note that while W&B asserted ‘surprising’ heterogeneity in their reconstructions of stand density and species composition, their data are not substantially different from many previous studies which reached very different conclusions about subsequent forest and fire behaviour changes. Contrary to the conclusions of W&B, the preponderance of scientific evidence indicates that conservation of dry forest ecosystems in the western United States and their ecological, social and economic value is not consistent with a present-day disturbance regime of large, high-severity fires, especially under changing climate.