Sierra Nevada Bio-region
Chapter 1: Ecological Integrity of Ecosystems - Riparian Ecosystems
Riparian Meadow and Riparian Non-Meadow Ecological Integrity

Current Condition



Riparian meadow and riparian non-meadow ecosystems border or straddle water bodies including streams, rivers, ponds, lakes, and seeps or springs. As a result, these areas support plants and animals adapted to wet environments. These riparian zones link terrestrial and aquatic systems. They play important roles in the landscape both for habitat and water and nutrient cycling. Transfers of nutrients, sediment, and coarse organic matter (leaves to logs, and contaminants between aquatic and riparian zones affect both systems. Riparian areas filter sediments and nutrients, and store water in alluvial soils that may prolong or sustain stream flow later in the summer (Yarnell et al. 2010).

Two distinct riparian ecosystems can be differentiated; 1) riparian meadow systems; and 2) riparian non-meadow systems (Fites-Kaufmann et al. 2007). They have different species composition, structure, and in some ways function. Riparian meadow systems are dominated by herbaceous vegetation, grasses, grasslike species, such as sedges or rushes, and often mosses and ferns (Weixelman et al. 2011). Riparian meadow settings generally have finer textured soils and better water holding capacity (WHC) (Potter 2005). Riparian non meadow areas include both woody species of shrubs and trees, as well as herbaceous grasses, grasslike species, mosses, and ferns. These riparian non-meadow settings generally have shallower soils, occur on steeper slopes, have higher coarse fragments (rocks) in the soils, and lower WHC (Potter 2005).

Most animal species in the region use both riparian meadow and riparian non meadow areas, at least seasonally, and some require these areas for breeding or their sole habitat. The emphasis of this section is on the vegetation, soils, and to a lesser degree hydrology in riparian ecosystems.

Riparian meadow and non-meadow plant communities are formed by the interacting effects of flood frequency and intensity, soil saturation and depth of water table, proximity to the channel, height above water level, sediment deposition, and ice scouring. In turn, these factors are controlled by flow levels, sediment availability, channel structure and substrate, channel erosion, and channel meandering which produces backwaters, old channels and different flow gradients and areas of deposition. Local factors determining the dominant species on a site include duration of soil saturation, soil depth, soil texture, flood frequency, season and duration, water table depth, degree of ice scouring, soil oxygen availability, browsing, grazing, and fire (Knight 1994, Weixelman et al. 2011). Changes in plant community composition are driven by successional processes in response to disturbance and simultaneously by changes in flooding regime and water table, all of which can change the site type and the potential plant communities that can form. Changes in stream gradient, sinuosity, channel width-to-depth ratios, topography and floodplain landform, and soil type (Knight 1994:43) driven by stream narrowing/widening, meandering/ channelization, and scouring/deposition produce various riparian landforms and resulting vegetation communities (Friedman et al. 1997). Vegetation composition is altered below dams due to changes in magnitude, duration, and frequency of flow levels below these structures.

Three photos showing riparian stream ecosystems for three different stream gradients: (a) low gradient, < 2%; (b) middle gradient, 2-4%; and (c) high gradient, > 4%

.Understanding these complex dynamics between hydrology, vegetation, soils, and wildlife is an ongoing effort. A conceptual model depicting the structure and functioning of riparian and meadow ecosystems is useful to summarize what we understand at this time, figure below. Shown in the model in Figure 2 are key ecosystem attributes which affect the structure and functioning of riparian meadow and non-meadow ecosystems. Major ecosystem attributes which affect riparian structure and function are soil, terrestrial invertebrates, terrestrial vertebrates including livestock, climate, upland watershed characteristics, and streamflow regime. General patterns of influence for each of these major ecosystem attributes on riparian systems is shown in Figure 2 as well as interrelationships between major ecosystem attributes affecting the riparian ecosystem.

General conceptual model depicting the structure and functioning of riparian meadow and non-meadow ecosystems. Symbols represent the following: rectangles = biotic components; ellipses = state factors or major drivers of ecosystem change or variability. Arrows indicate functional relationships among components. The model is constrained by climatic conditions, topography, parent material, and potential biota (adapted from Chapin et al. 1996)

Current Condition

Riparian non-meadow ecosystems

Riparian non meadow areas include those areas where woody plant species are dominant over herbaceous species in the riparian zone. Condition of riparian non-meadow areas, like other riparian areas, is determined by functional and structural characteristics. Condition of these non-meadow riparian areas is often summarized by comparing existing tree densities, stand age class distribution, and understory composition with historical or “natural” conditions. Potter (2005) described major non-meadow vegetation types and characteristic soils for the Southern Sierra Nevada. Potter classified a number riparian non-meadow plant communities including those dominated by aspen (Populus tremuloides), willow (Salix spp.) lodgepole pine (Pinus contorta), Ponderosa pine (Pinus ponderosa), and alder (Alnus incana) with considerable variation within types. In addition to variation within individual types, riparian non-meadow ecosystem types are arranged across the landscape in patchy, spatially complex patterns. This results primarily from the interactions of elevation, hydrogeomorphic surface, and fluvial disturbance, and leads to stands that are relatively small (Potter 2005). There is little data available on the ecological condition of non-meadow riparian areas in the Sierra Nevada and the Southern Cascade ranges. The data that does exist is primarily concerned with structural characteristics such as overstory stem densities, fuel loading, and stream flow characteristics.

Because riparian non meadow areas are dominated by trees and/or shrubs, structural characteristics are an important aspect of their function. Structural characteristics that are important in riparian systems include the proportion of conifer to hardwood cover, canopy layering, canopy cover, and bare ground.

Dams and diversions, climate change, fire, concentrated recreation use, vegetation management, and grazing can all affect the structure, composition, and function of riparian areas. Little information exists on how most of these activities have affected riparian ecosystem Kattelmann and Embury 1996). Most information is available on modifications from water development and the effects of fire suppression. Stream flow characteristics have been locally modified by dams which alter the timing, duration, and frequency of flood events.
Fire plays an important role in shaping many Sierran riparian non meadow tree and shrub riparian ecoystems van Wagtendonk and Fites-Kaufman 2006) but longer fire return intervals and reductions in area burned have altered these communities (Van de Water and North 2011). Productive, mesic riparian forests can accumulate high stem densities and fuel loads, making them susceptible to high-severity fire. Fuels treatments applied to upland forests, however, are often excluded from riparian areas due to concerns about degrading streamside and aquatic habitat and water quality.

Van de Water and North (2011) found that under current conditions, riparian forests were significantly more fire prone than upland forests, with greater stand density (635 vs. 401 stems/ha), probability of torching (0.45 vs. 0.22), predicted mortality (31% vs. 16% BA), and lower quadratic mean diameter (46 vs. 55 cm), canopy base height (6.7 vs. 9.4 m), and frequency of fire tolerant species (13% vs. 36% BA). Under current conditions the modeled severity was much greater in riparian forests, suggesting forest habitat and ecosystem function may be more severely impacted by wildfire than in upland forests (Van de Water and North 2011). However, this study used 97th percentile fuel moisture and weather conditions (i.e., the most extreme fire weather) to model potential fire behavior and even under those circumstances found only 31% predicted mortality, which is associated with low/moderate severity fire.

Condition of riparian non meadow areas has been affected in certain areas by dams. Dams and water diversions can heavily modify the volume of water flowing downstream, change the timing, frequency, and duration of high and low flows, and alter the natural rates at which rivers rise and fall during runoff events. Although much has been written about the ecological consequences of hydrologic alteration, Bunn and Arthington (2002) summarize their review of this literature by highlighting four primary ecological impacts associated with flow alteration: (1) because river flow shapes physical habitats such as riffles, pools, and bars in rivers and floodplains, and thereby determines biotic composition, flow alteration can lead to severely modified channel and floodplain habitats; (2) aquatic species have evolved life history strategies, such as their timing of reproduction, in direct response to natural flow regimes, which can be de-synchronized through flow alteration; (3) many species are highly dependent upon lateral and longitudinal hydraulic connectivity, which can be broken through flow alteration; and (4) the invasion of exotic and introduced species in river systems can be facilitated by flow alteration.

Summary of riparian existing conditions in relation to the riparian natural range of variability (NRV)
  • Most available accounts indicate a major decrease in area of riparian vegetation in the assessment area since European colonization. As of 1988 less than 2%, of the Sacramento River’s Riparian forest is estimated to remain (Spotts 1988) and riparian vegetation currently makes up less than 1% of the Sierra Nevada bioregion area (Kattelmann & Embury 1996).
  • Late 19th century timber harvest had disproportionate impacts on riparian forests both because rivers and drainages were frequently used to transport harvested logs and because gold-mining activities were focused within streams and required wood (Kattelmann & Embury 1996).
  • Many historic riparian sites are now under water, as wide valleys with large swaths of riparian habitat offered ideal reservoir locations (Kattelmann & Embury 1996).
  • In areas where water flow has been completely or nearly eliminated due to water development riparian vegetation has nearly disappeared (Kattelmann & Embury 1996; Stine et al. 1984).
  • Riparian zones are at greater risk of fragmentation, and non-native species invasion, than historically.
  • 93% of studied watersheds in the assessment area have clear gaps in the riparian corridor – largely from road/railroad crossings, timber harvest, private lot clearing, livestock grazing, and dam/diversion dewatering (Kondolf et al. 1996).
  • Riparian zones are among those areas of the Sierra Nevada most impacted by non-native invasive species (Schwartz et al 1996), and altered riparian systems may be especially vulnerable (Parks et al. 2005).
  • Current riparian forests are more fire prone than reconstructed historic riparian forests, including great basal area, stand density and snag volume, duff and total fuel loads, predicted surface and crown flame lengths, probability of torching, and predicted post-fire tree mortality (Van de Water & North 2011).
  • Fire plays an important role in shaping riparian communities (Russell & McBride 2001), but fuel management has been prohibited in riparian corridors due to concern for water quality and sensitive riparian ecosystems (Kobziar & McBride 2006). Fire return interval (FRI) was found to be shorter for riparian zones which bordered narrower, more incised streams, where FRI and fire severity may mirror upland characteristics (Van de Water & North 2010). Larger, extended, less steep riparian zones, other the other hand, may act as natural fire breaks (Kobziar & McBride, 2006; Van de Water & North 2010).
  • Major changes in flow regimes, a key shaping force of riparian communities, have led to significant differences between current and historic conditions in riparian zones.
  • Currently, droughts in the Sierra Nevada usually last less than a decade. The drought record suggests that that multidecadal and even multicentennial droughts (low flow regimes) would be expected under the natural range of variation (Benson et al. 2002).
  • In many regions of the assessment area, natural flow regimes have been so compromised by water development (e.g. diversion, exportation, inter-basin transfers), that discussion of current ‘natural’ flow regimes is limited in applicability (Elmore et al. 2003). For example, water diversion from the Truckee River led to a decrease in depth of Pyramid Lake in the 1960s greater than the estimated effects one of the most severe droughts of the previous 2,000 years (Benson et al. 2002).
  • More generally, water development throughout the assessment region has reduced flow seasonality and shifted flow peak timing, reducing spring flood pulses and augmenting summer flow (Vaghti & Greco 2007). The resulting lack of episodic disturbance and increased summer water levels have led to shifts in riparian species recruitment and survival (Vaghti & Greco 2007).
  • Over the last century, climate change has caused discernible shifts in factors causing debris flows in the montane areas of Western United States, including: more winter precipitation falling as rain instead of snow, leading to increased spring flow (Barnett et al. 2008); increased frequency of catastrophic floods due to rain-on-snow events (Herbst & Cooper 2010); and increased melting of alpine glacier cover (31-78% in the Sierra Nevada; Basagic & Fountain 2011).
  • Riparian communities contain more plant and animal species than any other California community type (Schoenherr 1992) and about one fifth of terrestrial vertebrate species in the Sierra Nevada depend on riparian habitat (Kattelmann & Embury 1996). About one quarter of wildlife species that depend on riparian habitat are considered at risk of extinction today (Graber 1996; Kattelmann & Embury 1996).
  • Surveys the lower Truckee River in 1981 revealed that only 1 of the 21 obligate riparian bird species had not shown strong declines in population since 1868 (Rood et al. 2003). As of the mid 1990s, half of the 32 amphibian species and almost half of the 40 fish species/subspecies found in the Sierra Nevada were endgangered, threatened, or of special concern (Moyle et al. 1996). Additionally, 85% of Sierra Nevada watersheds are characterized by poor to fair aquatic biotic communities (Moyle & Randall 1996).

Common terrestrial measures of riparian meadow function based on vegetation and physical attributes.
Meadow vegetation condition
Abundance of different plant functional groups; diversity index
USFS Region 5 Range Monitoring Program, USDA NRCS (1975), National Research Council (NRC) 1994
Non-native species
USFS Region 5 Range Monitoring Program
Streambank vegetation condition
Abundance of different plant functional groups
USFS Region 5 Range Monitoring Program
Soil characteristics
Amount of bare soil in meadows
Fryjoff-Hung & Viers, 2012. Sierra Nevada Multi-Source Meadow Polygons Compilation, USFS Region 5 Range Monitoring Program
Connectivity of stream to floodplain
Stream incision
Fryjoff-Hung & Viers, 2012. Sierra Nevada Multi-Source Meadow Polygons Compilation, Stillwater Sciences. 2012
Conifer encroachment in meadows
Abundance of conifer cover in meadow
Fryjoff-Hung & Viers, 2012. Sierra Nevada Multi-Source Meadow Polygons Compilation

Riparian meadow ecosystems

Riparian meadow areas are those riparian areas where herbaceous plant species are dominant over woody species. Riparian meadow areas occur on a variety of landforms and receive water from various sources including precipitation, surface water inputs, or groundwater inputs (Weixelman et al. 2011). Riparian meadow areas occur on fourteen distinct hydrologic and landform (hydro-geomorphic) combinations in the Sierra Nevada and Southern Cascade ranges in CA (Weixelman et al. 2011). Riparian meadow sites occur along streamsides in valleys with varying gradients , along borders of lakes or depressions, and on hillslopes associated with flowing water. These sites are dominated primarily by sedges including Nebraska sedge (Carex nebrascensis), and beaked sedge (Carex utriculata), grasses including tufted hairgrass (Deschampsia cespitosa), and redtop (Agrostis stolonifera), rushes including Baltic rush (Juncus arcticus), forbs including western aster (Aster occidentalis), and yarrow (Achillea millefolium). Lodgepole pine (Pinus contorta), willow (Salix spp.), alder (Alnus spp.), or current (Ribes spp.) may be present but are not dominant. This section will focus on low and middle gradient riparian meadow systems (0 to 4% slope)(Weixelman et al. 2011). These areas are among the most intensely used by recreationists and livestock grazing.

The ecological integrity of riparian meadow systems can be summarized by important indicators listed in Table 1. The measures listed in Table 1 are terrestrial variables that are commonly measured in riparian and meadow ecosystems to provide information on ecological integrity. An important key indicator is the presence and extent of non-native plants which indicate the extent of meadow degradation, or health/integrity. The other side of this indicator is the diversity index for the presence of a suite of typical Sierra meadow plant species. Meadow and streambank condition provides information on the ability of vegetation to stabilize streambanks (Winward 2000), slow floodwater and catch sediment (Stillwater Sciences 2008), cycle nutrients for plant growth, and provide for infiltration and water storage (Weixelman and Zamudio 2001). The amount of incision provides information on the connectivity of riparian and meadow areas to the stream, overbank flooding and recharge along channel boundaries (Weixelman et al. 2011), water storage in the adjacent riparian (Yarnell et al. 2010), and accumulation of organic material in the soil. Information on encroachment of conifers relates to water table depths, fire regime, disturbance, and climate change influences. Finally, data on the amount of bare soil provides information on soil stability (Weixelman and Zamudio 2001).

Meadow condition

Weixelman and Zamudio (2001) devised an integrated measure of meadow ecological condition based on soil and vegetation composition and structure. Based on this study, meadow condition can be shown graphically as in Figure 3. Four condition classes are shown in this graphic; early seral, mid seral, late seral, and potential natural vegetation (PNV). The four condition classes represent ecological health from low (early seral) to high (potential natural vegetation). At the early seral stage there is a high amount of disturbance resulting in an abundance of early successional plant species (Mosley et al. 1986), shallow rooting depths, and generally high amounts of bare soil (Weixelman and Zamudio 2001). Rooting depth is defined as the maximum depth of at least 1 root per square cm in the soil. This is the rooting density that is typical of later successional meadow plant communities (Weixelman and Zamudio 2001). At late seral and PNV, late seral species are dominant, rooting depths are deep, and there is very little bare soil. Late seral and PNV condition classes represent a desirable condition because there are ample amounts of late successional plant species for community resilience, greater plant diversity than lower condition sites (Weixelman and Gross, unpublished to be submitted spring 2013), and deep rooting depths to maintain soil stability and streambank protection.

Monitoring plots have been established for key area meadows under the Region 5 Range Long Term Monitoring Project. These plots are used to monitor rangeland condition and trend and the plots are re-read on a 5 year cycle. The plot locations are non-randomly selected and are located in areas within the meadow most likely to show change and transition. Specifically, the plots are located in mesic sites (moist meadow type) that are likely in a lower ecological condition as opposed to being placed in the hydric or wetter types that are more likely to be at good ecological condition. Therefore the plots are established to best determine changes such as fluctuations in species composition, over time. Since the monitoring sites were selected to best represent trend, they do not necessarily reflect the overall condition of an area. Condition in the wetter area may not be the same as in a drier area of the meadow. Key areas were selected within the meadows so that when the range types on these sites are at desired condition, or trending towards desired condition at a satisfactory rate, surround types will likely be trending the same.

Graphical representation of riparian meadow condition. Four condition classes are identified: early seral, mid seral, late seral, and potential natural vegetation, PNV (National Research Council, 1994).


Riparian meadow condition for the Sierra Nevada and Southern Cascades in CA

Meadow Key Sites

Using the four condition classes above, the condition of 505 meadow sites in the Sierra Nevada and Southern Cascades is graphically shown in Figure 4 based on results from the R5 long term monitoring of key sites. A wetland index on the vertical scale (Gross et al. 2013) indicates the type of meadow, whether wet, mesic, or dry. This index represents the proportion of plants that are wetland indicators, the larger the number, the higher the proportion of wetland indicators. The horizontal axis represents a functional index (from Gross et al. 2013) from zero to 100. The functional index is determined by the proportion of plant functional groups (Weixelman and Gross, to be submitted in spring, 2013) on a meadow site. Desired condition is represented by the late seral and potential natural vegetation condition classes (Weixelman 2013). The graph indicates that most of the meadows sampled were in the mesic or wet meadow type. The data represent the latest reading for each of the sites.

Graph of condition for 505 meadow sites in the Sierra Nevada and Southern Cascade ranges in California (from USFS R5 Long Term Monitoring Report, Weixelman 2013). Graph design adapted from Gross et al. (to be submitted, spring 2013). Sites shown are the long term monitoring plots established by the Forest Service range crews. Plots were established at key monitoring sites from 1999 to 2004. These plots are revisited every 5 years and continue to be visited. Condition increases from 0 to 100. Condition classes (0-25, 26-50, 51-75, 76-100) taken from National Research Council, 1994).

Random Meadow Sites

During 2001 and 2002, meadows were randomly chosen and sampled as part of the Sierra Nevada Framework Monitoring Program. During that time, 119 meadows were sampled to represent the condition of meadows across the Sierra Nevada and Southern Cascades. Figure 5 shows the condition of those meadows that were sampled. Unlike the sampling protocol above used for range monitoring, the sampling protocol used in the Framework monitoring consisted of transects placed across the entire meadow, thus giving an “average” condition for the entire meadow complex. As in the graph above, meadow condition is shown using a functional matrix adapted from Gross et al. (2013). A wetland index is shown on the vertical axis (see above) and a functional index is shown on the horizontal axis. The condition of these 119 sites show that wetter meadows were generally in higher condition than were dry meadows. In addition, as above, more wet and moist meadows were sampled than were dry meadows. The proportion of sites meeting or exceeding desired conditions is similar to the results for the range key site monitoring shown below.

Graph of condition for 119 meadow sites in the Sierra Nevada and Southern Cascade ranges in California (from USFS R5 Framework Monitoring, 2001 - 2002). Graph design adapted from Gross et al. (to be submitted, spring 2013). Sites shown are randomly sampled sites established in 2001 and 2002. Four condition classes are shown, early seral, mid seral, late seral, and potential natural vegetation (PNV). Condition classes taken from National Research Council, 1994). Desired conditions are late seral and PNV.

Ecological Integrity and Natural Range of Variability for Meadows
At this point, the range of natural variability (NRV) for meadow areas has not been determined for the Sierra Nevada and Southern Cascades and has been estimated based on areas that have been ungrazed (including exclosures) for 20 to 30+ years (Weixelman and Zamudio XXXX) and analyses of meadow ecological integrity have been based on these results. To further refine estimates of the NRV for meadows, a study will be undertaken starting in summer, 2013, and extend through 2014. This study will involve sampling approximately 120 meadows in the National Park system in the Sierra Nevada and Southern Cascade ranges. This sampling will allow the Forest Service to estimate the NRV condition for meadows and provide information on distribution of meadows successional stages that can be expected across the landscape under conditions approximating the NRV. This assessment of meadow NRV will use the scoring system outlined in Gross et al. (unpublished, to be submitted spring 2013) and the plant ratings for indicating ecological integrity outlined in Weixelman and Gross (unpublished, to be submitted spring 2013) to assess the ecological integrity of the sampled meadows in the National Park System. This will provide a direct comparison to meadows and land disturbing impacts on Forest Service lands with meadow NRV.

Streambank vegetation condition in meadows
The kind, amount, and location of vegetation are crucial to the function of most riparian systems. Greenline (streambank) monitoring measures the vegetation along the edge of streams. This method samples plant community type composition on both sides of the stream in a selected section of a stream (within one riparian vegetation complex) and compares the composition with objectives for the area as well as past measurements. Objectives may be based on a “standard” required for proper functioning of that particular stream type. Winward (2000) suggests the standard and rates each community type’s ability to buffer the forces of moving water. Greenline data can be used to develop a rating of both ecological status (i.e. the kind and amount of existing vegetation on that particular section of stream in relation to the amount and kind of vegetation that might potentially occur on that stream section) and average physical strength for buffering the effects of moving water (streambank stability rating). Greenline data as the same location through time can be used to evaluate long-term trend.

Ecological integrity of streambanks gives an indication of the stability of the streambank system in a meadow and susceptibility to streambank failure. Streambank failure can result in stream widening, incision, or both. The greenline method of Winward (2000) was used to assess the ecological integrity (condition) of streambank vegetation in meadows for grazed allotments in Region 5. A total 155 permanent monitoring sites for streambank vegetation have been established in Region 5 and these sites are monitored every five years. These monitoring sites were established from 1999 to 2004 using the greenline method. Successional stages are used to summarize the greenline method (Winward 2000). The early successional stages are considered lower ecological condition, while the late successional stages and PNC (Potential Natural Community) are considered high ecological condition. The greenline is a measure of the percent of late successional plant communities on the streambank (greenline) along a lineal stretch of 364 ft. of streambank. The figure below summarizes the results and represent the latest readings taken during the period 2004 to 20111. Desired conditions for these sites are late seral or PNC (Potential Natural Community). The data represent the latest reading for each of the sites.

A summary of results for streambank vegetation data in low and middle gradient riparian meadow types for eight National Forests (from Weixelman 2013).


Incision depths for stream channels in meadows in the Sierra Nevada and Southern Cascade ranges

Stream incision occurs when a streambed downcuts (degrades) in elevation (Simon and Rinaldi 2006). Incision is a common response of alluvial channels that have been disturbed such that they contain excess amounts of flow energy or stream power relative to the sediment load (Simon and Rinaldi 2006). One way in which changes in streambed elevation relative to floodplain elevation can lead to cascading effects on adjacent ecosystems is by impacting soil water availability. An incising streambed leads to a lower stream surface elevation, which then leads to a reduction in the water table elevation. A lower water table results in reduced water availability in the root zone and, typically, a transition to plant communities more adapted to dry conditions. Many examples of this phenomenon exist in the wet meadows of the Sierra Nevada and southern Cascade ranges in California, USA (Loheide et al. 2009).

The causes of the channel incision include changes to the streamflow regime, overgrazing, mining activities, road/railroad construction and channelization/drainage activities. Increased peak stream discharge has mostly been a consequence of changes in land use following Euro-American settlement in the mid-1800s (Loheide et al. 2009) but may also be related to changes in climate (Germanowski and Miller 2004). Overgrazing by sheep and cattle was very common throughout the Sierra Nevada prior to 1930 (SNEP 1996) and led to direct mechanical action of hooves on the stream bed and banks as well as compaction of soil in the uplands, reduced infiltration rates, and increased surface runoff (Trimble and Mendel 1995). In addition to the effects of grazing, timber harvesting played a role in increasing the magnitude of the hydrologic response through increased surface runoff and decreased surface roughness. The other direct cause of channel incision – stream channelization – was also common across the region. Some channelization projects were intentionally constructed to drain wet meadows to allow for railways, roads, homes, and agriculture; other projects related to railway/road construction or crossings inadvertently led to channel degradation and wet meadow drainage (SNEP 1996).

When the stream bed incises, the stream stage and water table in the interconnected aquifer also decline, causing the near-surface soil water regime to become drier in the meadow. However this process does not occur uniformly across the valley. The slope of the water table increases as a consequence of incision and continued groundwater inputs to the valley from the hillslope. This results in more xeric (very dry) vegetation near the channel where the water table depth is greater as compared with near the hillslope where more mesic (moderate amount of moisture) vegetation is present.

During summer, 20010 and 2011, surveys were conducted to measure channel incision on 101 meadows on six National Forests in the Sierra Nevada and Southern Cascade ranges (Fryjoff-Hung & Viers, 2012). The results of the surveys are shown in Figure 6. The results are given as the amount (cm) of stream incision. Results were not available for the amount of incision using bank height ratio, i.e. the height of the bank relative to the depth of the stream. Bank height ratio is informative as it scales to the stream channel size. However, the results presented here are informative in giving a general summary of the depth of incision for wadeable streams in the Sierra Nevada and the potential loss of wet meadow. These results indicate that approximately 46 out of 101 (or 46%) of riparian meadows on six National Forests were not incised significantly, while 54% were significantly incised based on depth of incision.

Incision depth for 101 low and middle gradient riparian sites for six National Forests, Sierra Nevada and Southern Cascade ranges, CA (Fryjoff-Hung & Viers, 2012)

Conifer cover in meadows

Conifer encroachment into montane meadows in the Pacific northwest and California Sierra Nevada has been reported by many authors (Vale 1981, Rochefort et al. 1994, and Taylor 1995, Griffiths et al. 2005). Since meadows are more diverse than adjacent forests, replacement of
meadow vegetation by conifer forest reduces local and landscape biodiversity (Haogo and Halpern 2007). In the central Sierra Nevada, including areas within and just south of the CABY region, encroachment occurs most commonly with lodgepole pine and to a lesser amount, red fir.
Western hemlock encroachment in meadows also occurs within the zone of this species (Taylor 1995). Conifer encroachment into mountain meadows has been attributed to several (nonexclusive) causes, including climate effects (Helms 1987 and Woodward et al. 1995, Millar et al. 2004), direct effects from grazing (Andersen & Baker, 2005; Franklin et al., 1971), cessation of grazing (Dunwiddie 1977, (Vale 1981, Miller and Halpern 1998), and fire suppression (Arno and Gruell 1986, Hadley 1999). It is possible that all of these factors allow for increased conifer cover in existing meadows. Millar and others (2004) recently published a study including 10 meadows experiencing conifer (lodgepole) invasion in the Central Sierra Nevada. Tree establishment dates were correlated to long-term fluctuations in weather patterns associated with climate change (Pacific Decadal Oscillations or PDO). Over 87% of the cored meadow trees were established within a single 30 year period (1945 to 1974), which coincided with negative PDO, associated with consistently drier weather and low soil moisture in the 20th Century. Thus, Millar et al. (2004), argue that conifer invasion in these meadows occurred during a single mid-20th Century pulse that was triggered by climatic conditions.

During summer, 20010 and 2011, surveys were conducted to measure the amount of conifer cover in 101 meadows on six National Forests in the Sierra Nevada and Southern Cascade ranges (Fryjoff-Hung & Viers, 2012). The results of the surveys are shown in Figure 7. The results are given as the percent cover of conifer trees in the meadow. Results indicate that approximately 27/101 or 27% of riparian low and middle gradient systems have little or no conifer cover (< 1%), while 40% have a conifer cover greater than 10%. While 12% of the sampled meadows had a conifer cover greater than 20%.

Amount of conifer cover on 100 meadows on 6 National Forests, Sierra Nevada and Southern Cascade ranges, CA.

Photo of low gradient riparian area and meadow on the Plumas National Forest. Conifer encroachment is occurring on this meadow and restoration by cutting of conifers has been conducted (note tree stumps) (photo by D. Weixelman).

Amount of bare ground in meadows

Bare ground--soil that is not covered by vegetation, litter or duff, downed woody material, or rocks--is highly susceptible to erosion. It may contribute both to overland sediment flow and to the erosion of streambanks. In both cases, it can affect water quality as well as the loss of valuable soil and acreage. Soil not covered by desirable vegetation is a prime area for invasion of noxious weeds or other undesirable plant species. Bare ground increases the possibility of compaction or bank shearing by hoofed animals, vehicles, or people. This reduces the water-holding capacity of the soil.

One of the difficulties in assessing this aspect of riparian health is that many riparian areas will naturally have bare soil and dry meadows naturally have more bare soil than wetter meadows. After high flow events, bare soil in the form of trapped sediment could indicate riparian vegetation on the site is performing its sediment-trapping function. On the other hand, such a situation could also reflect an unstable situation further upstream.
It is important to try to determine what caused the bare ground. If it is related to or caused by human activities or has been increased by management practices, it is more likely to indicate a deteriorating situation somewhere along the stream. Some human activities which can lead to increased bare ground are livestock mismanagement, poor road construction, or excessive ATV use.

The Forest Service considers bare ground in excess of 10% cover as an indication of significant degradation in wet and moist meadows on key range monitoring sites. In some cases, gopher activity can produce high amounts of bare ground in some meadows. Figure 9 summarizes the percent bare ground on 110 meadows on six National Forests in the Sierra Nevada and Southern Cascade ranges. Results indicate that approximately 81% of meadow sites in this survey have less than equal to 10% bare ground, while 19% have greater than 10% bare ground. A value of greater than 10% bare ground generally indicates that significant degradation has occurred in a meadow. The data represent the latest reading for each of the sites.

Amount of bare ground for 101 meadows on 6 National Forests, Sierra Nevada and Southern Cascade ranges, CA.



In order to provide information on trends for condition of riparian meadows areas and to provide information on the relationship of managed grazing and the ecological integrity of meadows sytems, the Forest Service Pacific Southwest Region 5 has entered into a Challenge Cost Share Agreement with the University of California, Davis Rangeland Watershed Laboratory. This project was initiated to evaluate rangeland (meadow and upland) ecological integrity and trends in ecological integrity across grazing allotments in U.S. Forest Service (USFS) Region 5. As described above, the Forest Service Pacific Southwest Region 5 initiated a long-term, region-wide monitoring program to make field measurements of rangeland plant and soil indicators of ecological condition (Rangeland Long-Term Condition and Trend Monitoring Program). Over 800 monitoring sites have been established throughout the Region since 1999, with sites sampled/re-sampled every 5 years.

Dr. Kenneth Tate’s laboratory is currently collaborating with Region 5 to conduct statistical analysis of these data to determine ecological condition and trend condition, and correlate management to trends in condition.
Objectives of the study include the following:

Objective one: Statistically analyze, interpret and publish results on: 1) rangeland condition and trend for the over 400 sites enrolled in the Rangeland Long-Term Condition and Trend Monitoring Program -Term Meadow Monitoring Project which have 10 years of data; and 2) correlation of grazing management and standards and guidelines with rangeland condition and trend.

Objective two: Transfer the information developed from these analyses to USFS staff, grazing managers, and stakeholders to enhance range NEPA accomplishment, inform up-coming Forest Plan revisions, and to help identify restoration opportunities.

It is expected that when this information is available it will be included in the Forest Plan revision process. This study will provide a more meaningful assessment of trend and response to grazing management as well as to weather and other factors (i.e., elevation, initial meadow condition).

Riparian Fauna

Though less than 1% of the area of the Sierra Nevada is comprised of riparian habitat (Kattlemann and Embury 1996), approximately onefifth of the 400 species of terrestrial vertebrates that inhabit the Sierra Nevada are strongly dependent on riparian areas (Graber 1996).


Riparian areas are among the most important habitats for birds in the Sierra Nevada (Siegel and DeSante 1999, Burnett and Humple 2003, Burnett et al. 2005).

Meadows and birds

In the Sierra Nevada, riparian aspen and meadows support several rare and declining bird species and are utilized at some point during the year by almost every bird species that breeds in or migrates through the region (Siegel and DeSante 1999 ). Management and restoration of aspen and meadow habitats should consider the importance of the habitat to birds and other wildlife. A disproportionate number of the special status wildlife species in the Sierra Nevada are tied to meadows, including four bird species – Greater Sandhill Crane, Great Gray Owl, Willow Flycatcher, and Yellow Warbler. Using meadow and aspen associated meadow-dependent bird species (focal species) as indicators of aspen and meadow ecological function can be a powerful adaptive management tool for informing management and restoration decisions in Sierra Nevada (see //Managing Meadows for Birds in the Sierra Nevada//: Through such a focal species approach, it is possible to identify conservation priorities, help guide meadow and aspen restoration design and management prescriptions, and establish and evaluate management and conservation targets (Burnett et al. 2005, Chase and Geupel 2005, Campos and Burnett 2012).

Aspen and birds

The health of aspen habitat across the West has deteriorated over a century of mismanagement. Estimates suggest its extent in western North America has been reduced by as much as 96%, primarily because of fire suppression and overgrazing. Aspen habitat, especially when associated with riparian vegetation, is the single most species-rich avian habitat in the Sierra Nevada. Several bird species of management interest are associated with aspen including Northern Goshawk, Red-breasted Sapsucker, Warbling Vireo, and Mountain Bluebird. With its disproportionate importance to birds and other wildlife, limited extent on the landscape, and significant loss and degradation, aspen restoration should be among the highest priorities of land managers in the Sierra Nevada. Strategies for enhancing aspen bird habitat include: (1) promoting aspen regeneration and expansion, (2) managing for multiple age and cover classes, (3) restoring riparian aspen communities, (4) managing for dense and diverse understory, (5) limiting grazing and over-browsing (see //Managing Aspen Habitat for Birds in the Sierra Nevada//:

Bird species richness and abundance in aspen habitat in the Sierra Nevada are positively correlated with lower percent conifer cover and increased herbaceous cover (Richardson and Heath 2004). Aspen stand restoration through the removal of competing conifers works to promote the regeneration of aspen stands (Jones et al. 2005) and provide habitat for many aspen-associated bird species (Campos and Burnett 2012).

Willow Flycatcher

Once common throughout the western United States, the willow flycatcher (Empidonax traillii) has been extirpated from much of its range. In central California, this Neotropical migrant is limited to breeding in montane meadows. Surveys indicating a declining population trend led to the listing of the willow flycatcher as a California state endangered species, which prompted the initiation of a distribution and demographic study in 1997 (Mathewson et al. 2011). This research includes over 30 study sites (meadows) grouped into 3 regions: south (south of Lake Tahoe), central (north Lake Tahoe, Truckee meadows and vicinity), and north (Warner Valley south of Lassen Volcanic National Park). Primary objectives were to (1) determine the distribution of breeding willow flycatchers; (2) quantify reproductive success, recruitment, dispersal and survival of willow flycatchers in selected meadows; (3) examine factors influencing demographic patterns through associated graduate research projects; and (4) use the results to make management and restoration recommendations (Mathewson et al. 2011).

The willow flycatcher population in the central Sierra Nevada declined during the course of this 14-year monitoring study (Mathewson 2011). The study reported an apparent contraction of their range from south to north, in that populations in the South Tahoe region all but disappeared during the course of our 14-year study, likely resulting from initial small population size, stochastic weather events, and low reproduction that influenced dispersal dynamics. The population of flycatchers in the Truckee regions exhibited annual fluctuations around stability, but with an overall declining trend. The persistence of flycatchers in the Truckee region likely was facilitated by the proximity of large (>100 ha) meadows with suitable breeding habitat interspersed with smaller meadows.

Relative to populations of willow flycatchers in lower elevation and non-mountainous regions, flycatchers in the South Lake and Truckee regions are constrained by the amount of time available to nest within a season. The nestling period and early fledgling period, and thus the month of July and early August, is a critical period determining reproductive success for an individual flycatcher. Riparian shrub density at the territory scale and extent of meadow inundation by water were the most influential habitat components.

Mathewson et al. (2011) recommended a meadow restoration initiative through-out several meadows of the Sierra Nevada within the current range of the flycatcher and at adjacent sites that supported flycatchers in the recent past. Habitat restoration would likely enhance nest success and it is one action that we can take on the nesting grounds that has some potential to increase juvenile recruitment and adult survival. Second, the study recommends moving grazing out of meadows with breeding flycatchers until the end of August. Current management practices allow for grazing starting in mid-July but this is a sensitive period for flycatchers in determining nesting survival, re-nesting possibilities, and post-fledgling survival. Brown-headed cowbird control would be beneficial in the short-term at some of the meadows that support currently breeding flycatchers but that for long-term sustainability meadow restoration will buffer the negative effects of parasitism. Last, these populations required continued monitoring to determine the effectiveness of meadow restoration efforts.

Great Gray Owl

In, 2010, it was documented that Yosemite's great gray owl (Strix nebulosa Yosemitensis) as genetically distinct from the great gray owl in western North America (Strix nebulosa nebulosa) (Hull et al. 2010). In addition to genetic differences, behavioral differences appear to exist in the Yosemite subspecies. These include differences in migration patterns, prey preference, and nest site selection. Each of these genetic and behavioral characteristics indicates the Sierra Nevada population of great gray owls has been isolated from other populations for an extensive period of time.

Yosemite, today, is the southernmost range and last sanctuary of almost all of California's great gray owls, listed as California State Endangered Species. Researchers estimate there are only about 200 to 300 individuals in California, and about 65% of the state's population resides in Yosemite. Great gray owls nest in the middle elevations of the park where forests and meadows meet. They can be active at any time of the day or night, preferring to hunt in open meadows and clearings within the forest. In the winter, they move downslope to snow-free areas where they can more easily access their rodent prey.

Wintering habitat of the Great Gray Owl was recently studied by Jepson et al. (2011). Little information is available on the winter ecology of the small, geographically isolated, genetically-unique population of great gray owls (Strix nebulosa) in the central Sierra Nevada, California. This population is comprised of facultative, elevational winter migrants and access to winter habitat is an important component of their ecology. Winter observations and remotely sensed habitat variables were used in a study by Jepson et al. (2011) to inform a predictive model of the environmental requirements and geographic distribution of this owl population. Using the modeled distribution map, the assessed the distribution of 20% probability of occurrence classes relative to owl habitat associations, ownership, current development, and projected future development patterns. Findings indicated that high probability class (81–100%) areas and the broader joint medium/medium-high/high probability class (41–100%) areas are uncommon on the landscape (0.2% and 5.0% of study area, respectively). High probability areas were characterized by Sierran Yellow Pine forest surrounding relatively small, flat areas of grassland, wet meadow, and riparian habitats, within the mid-elevation range. Approximately 32% of the high probability areas and 48% of the medium/medium-high/high probability areas occur on private lands. Of the areas on private lands, 32% of the high probability and 42% of the medium/medium-high/high probability areas occur on currently developed lands. Projected future development on private lands indicated that an additional 12% of the high and 18% of medium/medium-high/high suitability areas are slated for development by the year 2040. The study concluded by saying that future conservation planning efforts for the great gray owl in the Sierra Nevada will need to address management issues on both public and private lands (Jepson et al. 2011).


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