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Among-Site Variation in Riparian Vegetation of the Southern California Transverse Ranges

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Jacob Bendix at Syracuse University
Jacob Bendix
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Abstract

Data from 37 sites in the Transverse Ranges in southern California were used to assess the influence of a variety of environmental variables on among-site variation in riparian vegetation. Ordination and regression analyses indicated that elevation, unit stream power, fire history and valley width all have significant impacts on the composition of this vegetation. TWINSPAN classification generated four species groups: a Baccharis glutinosa/Salix laevigata group that appears related to low elevations, high stream power and recent fire; a Populus fremontii/Alnus rhombifolia group associated with high stream power, but longer time since burning and higher elevations; a Salix lasiolepis/Rosa californica group typically found at high elevation sites with low stream power; and a Platanus racemosa/Adenostoma fasciculatum group that did not show a clear environmental preference.
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The University of Notre Dame
Among-Site Variation in Riparian Vegetation of the Southern California Transverse Ranges
Author(s): Jacob Bendix
Source:
American Midland Naturalist,
Vol. 132, No. 1 (Jul., 1994), pp. 136-151
Published by: The University of Notre Dame
Stable URL: http://www.jstor.org/stable/2426208
Accessed: 26/03/2010 11:04
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... The spatial distributions of riparian plants reflect differing tolerances along gradients of water availability and disturbance, in addition to biotic interactions Osterkamp 1996, Bendix andHupp 2000). Divergent responses of species to these drivers result in distinctive community types associated with particular hydrogeomorphic settings (Bendix 1994, Shaw and Cooper 2008, Angiolini et al. 2011. Thus, associations between vegetation composition and hydrogeomorphic channel types provide a means for evaluating ecologically meaningful differences in riparian habitat among channel types. ...
... As a primary determinant of streamflow velocity and sediment transport capacity (Knighton 1998), bed slope governs the disturbance regimes that directly affect plant communities (Hupp 1982, Baker 1989, Bendix 1997. Spatial variation in sediment transport and deposition controls the distribution and character of fluvial landforms, thereby influencing patterns of flood inundation that shape the distributions of plant species and vegetation types (Hupp 1982, 1986, Bendix 1994, Bendix and Hupp 2000. At larger spatial scales, bed slope and related covariates (e.g. ...
... Within the study area, bedrock channels occur at the highest elevations and piedmont headwaters occur at moderate elevations, while incised alluvium and braided channels are found at the lowest elevations. Compositional differences in riparian vegetation along elevation gradients have been recognized in mountainous drylands elsewhere (Baker 1989, Bendix 1994, Sieben et al. 2009, Polvi et al. 2011, Engelhardt et al. 2015. ...
Applying a Hydrogeomorphic Channel Classification to understand Spatial Patterns in Riparian Vegetation
Article
Full-text available
  • Mar 2018
Questions Hydrogeomorphic channel classifications are widely employed to understand natural phenomena in earth sciences, but they are rarely used in riparian vegetation studies. However, when these types of classifications correspond to physical process domains (discrete landscape units with consistent abiotic attributes), they may be useful in distinguishing habitat and vegetation types. We assessed the ecological significance of a hydrogeomorphic stream channel classification by addressing the following questions: (1) Does perennial plant community composition differ among hydrogeomorphic channel types? (2) Which species and functional groups contribute to compositional variation among channel types in the Sonoran Desert? (3) What are the stream reach‐scale geomorphic drivers of compositional variation?. Location Sonoran Desert, Arizona, USA. Methods We compared perennial riparian plant community composition among five a priori hydrogeomorphic channel types at 86 stream reaches in arid ephemeral watersheds. Floristic differences among channel types were assessed using PerMANOVA. Generalized linear models were used to identify species and functional groups whose abundance differed among channel types. Abiotic drivers of compositional differences were identified by correlations among biotic and abiotic matrices. Results Community composition differed significantly among channel types, with distinctive vegetation in bedrock, piedmont headwater, and braided channels. While different from other channel types, vegetation in bedrock with alluvium and incised alluvium channels was broadly similar, but could be distinguished by the abundance of common species and functional groups. The density of drought deciduous subshrubs, as well as large woody plants with evergreen, drought deciduous, and photosynthetic stem phenology contributed to the observed compositional variance. Bed slope was the primary driver of compositional differences among channel types, with elevation providing additional explanatory power. Conclusions Hydrogeomorphic channel classifications corresponding to distinctive fluvial process domains are useful for understanding spatial variability in riparian habitats and resulting differences in plant community composition in the Sonoran Desert. Analogous spatial patterns of riparian plant communities previously reported from other arid regions suggest that these general channel types are broadly applicable. This article is protected by copyright. All rights reserved.
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... Mountain alders were found in over two-thirds of the plots, and were most common along steep, rocky channels in V-shaped valleys. Bendix (1994) found a high correlation between white alder (Alnus rhombifolia) and stream power (r = 0.41). This finding supports my field observations that alders were able to survive severe, scouring floods in 1996/1997 when individuals of other species, including willow and aspen, were decimated. ...
... The twelve ecosystem types I identified in the LTB are modestly separated in ordination space compared to ordinations of upland ecosystem types (for example, see Hix and Pearcy 1997). However, other studies of riparian and wetland types reflect similar or greater degrees of variation within classes (Taylor and Davilla 1986, Risser 1988, Zogg and Barnes 1995, Bendix 1994. The degree of distinctness for each ecosystem type varied. ...
... In particular, patterns in vegetation related to response and recovery from disturbance might be more clearly revealed through direct measures of disturbance history (Sprugal 1991, Hobbs and Huenneke 1992) and/or stream power (e.g. Bendix 1994) than through the variables measured herein. Other abiotic characteristics not included in this study, such as measures of rooting zone soil temperatures, soil chemistry, and hydrology, might provide important, direct measures of factors controlling plant species distribution. ...
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... The strongest drivers controlling the distribution of riparian vegetation in the SCR are groundwater and resulting perennial or intermittent surface flow conditions--as represented by longitudinal vegetation patterns--and flood disturbance, as represented by cross-sectional vegetation patterns (Stillwater Sciences 2007, Beller et al. 2011, Beller et al. 2016, Stillwater Sciences 2016. These drivers demonstrate the importance of surface water availability for vegetation recruitment and succession, and surface water or shallow groundwater for vegetation growth, and align well with those found in previous studies of riparian vegetation in semi-arid river systems, including the magnitude and frequency of flood disturbance (Bendix 1994(Bendix , 1997Harris 1999;Bendix and Hupp 2000), depth to groundwater (as reflected in preference for gaining versus losing reaches; Stromberg et al. 1996, Shafroth et al. 1998, and a combination of the two (Hupp and Osterkamp 1996, Lite 2003, Bagstad et al. 2006, Leenhouts et al. 2006, Osterkamp and Hupp 2010. ...
... Riparian vegetation dynamics are tightly coupled with riverine processes; flooding, scour, and sediment deposition strongly influence riparian plant species composition, distribution, and physical structure and are major drivers of riparian community succession along with depth to groundwater. At a fine scale, riparian zones can be seen as non-equilibrium ecosystems, in which patches of vegetation become established and are seasonally altered (and often extinguished) by inputs of water and nutrients and by deposition and scour of sediment (McBride and Strahan 1984;Stromberg et al. 1991;Bendix 1994Bendix , 1999Stromberg 1997). At a coarser scale, riparian corridors can be seen as a steady-state landscape, in which the formation and annihilation of vegetation patches tend to balance out over the long term (assuming climatic and hydrologic regimes remain relatively constant), resulting in a shifting mosaic (or spatially heterogeneous, temporally dynamic patchwork) of habitats that have evolved under the influence of frequent disturbance (Johnson et al. 1976, Wiens 2002, Whited et al. 2007). ...
Final Report: Southwestern Willow Flycatcher (Empidonax traillii extimus) and Western Yellow-billed Cuckoo (Coccyzus americanus occidentalis) Surveys and Habitat Availability Modeling on the Santa Clara River, California, 26 March 2020
Technical Report
Full-text available
  • Mar 2020
Our project aimed to conduct population surveys for Southwestern Willow Flycatcher (Empidonax trailii extimus) and Yellow-billed Cuckoo (Coccyzus americanus) in 2018 and 2019, apply existing habitat models to illustrate and predict past, current, and future habitat suitabilities for these two species, and update and standardize classification and mapping of riparian vegetation to reflect recent conditions along the lower 50 miles of the Santa Clara River.
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... The site defensibility indicators used were fire and disturbance. Fire can destroy riparian vegetation or riparian species can be replaced by more fire tolerant species (Bendix 1994;Naiman et al. 2005). It is difficult to defend against and was heavily negatively weighted. ...
THE STRUCTURE AND COMPOSITION OF RIPARIAN VEGETATION IN TRINIDAD: A BASELINE FOR CONSERVATION AND RESTORATION
Thesis
Full-text available
  • Feb 2009
The structure and composition of riparian vegetation of 12 rivers in Trinidad were detailed, along with concurrent environmental and anthropogenic characteristics of the riparian zone and associated watershed. Cluster analysis, non-metric multi-dimensional scaling, and Spearman rank correlations were used to delineate riparian vegetation groups and indicator species, identify the most significant determinants of riparian vegetation groups and determine the most influential scale of variables. These data were used to develop a rapid assessment index to identify and prioritize riparian sites for conservation and restoration. An approximate riparian zone width of 30 m was suggested for Trinidad and a list of 57 native riparian species generated. Of 36 randomly chosen sites, only nine were in forested areas. Fifteen were in abandoned agricultural estates. The others were in agricultural, grassland and developed areas. An exotic species, Bambusa vulgaris, had the highest tree importance value and another exotic, Coffea sp., had the highest ground flora coverage. Nine major vegetation groups were identified and named according to dominant species,distribution and major determinants. These are Justicia secunda-Eschweilera subglandulosa (North Forest), Mora excelsa-Bactris major (South Forest), Saccharum officinarum (Agricultural), Axonopus compressus (Agricultural), Justicia secunda (Secondary Vegetation), Flemingia strobilifera (Fire Influenced), Sorghum sp. (Weedy Species), Acroceras zizanioides (Native Grasses) and Bambusa vulgaris (Bamboo) groups. With the exception of canopy closure, form factor and geomorphology, the best predictors of riparian vegetation groups were anthropogenic variables like the degree of upland and riparian zone edaphic modification, fire, channel modification, distance from paved roads, land ownership and pollution. Out of a 4-level hierarchy of variables, Meso scale (reach level) variables were most important in explaining riparian vegetation patterns. The rapid riparian index, which was developed, used eight variables to identify and prioritize sites for restoration and conservation. These included tree species richness, presence/absence of easily recognizable exotic and secondary vegetation species, and anthropogenic indicators like fire, channel modification and anthropogenic disturbance.
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... In this approach, vegetation species presence and/or cover was recorded and associated with elevation above the active channel, and by association with flood frequency and duration. Often, some type of multivariate analysis was used to classify species into groups that sort along hydrologic gradients (Harris, 1987;Auble et al., 1994;Bendix, 1994b;Rodríguez-González et al., 2010). ...
Riparian Vegetation and the Fluvial Environment: A Biogeographic Perspective
Chapter
  • Jan 2013
In this chapter, we review the historical arc of research on biogeomorphic interactions between fluvial geomorphology and riparian vegetation. We then report on an examination of the past 20 years of published research on this topic. Having classified studies according to the key relationships they have identified, we map those relationships to seek spatial patterns that emerge in terms of either physiographic environment or actual geographic location. We also consider the varied patterns of causal interactions that emerge at different spatial scales.
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... A number of factors account for the lack of selection for postfi re seedling recruitment: (1) the unpredictability of fi re penetrating riparian woodlands, (2) the ready water source favors rapid and dense vegetative regrowth that results in intense competition for seedings, and (3) the severe surface scour resulting from annual winter fl ooding, which carries away any soil stored seed banks. Differences in species response to fi re are largely unexplored, although these are to be expected based on species differences in distribution along disturbance gradients (Harris 1987, Bendix 1994. ...
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... Fire is a prevalent ecological disturbance that has shaped vegetation composition and structure and maintained a patchwork of different successional stages throughout watersheds of the western United States (Agee 1998;Bendix 1994;Turner and Romme 1994). The historic role of fire in many terrestrial ecosystems and forest types of the western United States is well-understood (Arno et al. 1996;Covington and Moore 1994;Fulé et al. 1997Fulé et al. , 2003Schoennagel et al. 2004). ...
Riparian Fuel Treatments in the Western USA: Challenges and Considerations
Technical Report
Full-text available
  • Sep 2016
Fuel reduction treatments are being conducted throughout watersheds of the western United States to reduce hazardous fuels in efforts to decrease the risk of high-severity fire. The number of fuel reduction projects that include near-stream environments is increasing, bringing new challenges to riparian management. Riparian areas are protected by administrative regulations, some of which are largely custodial and restrict active management. However, riparian areas have also been affected by fire suppression, land use, and human disturbance, so manipulative treatments of vegetation and other fuels may be needed in some locations to maintain riparian biodiversity and restore valued functions. This report is a synthesis of current knowledge on the effects of wildfire and fuels treatments in riparian areas of the interior western United States, and includes the following: (1) a literature review of fire effects on riparian and aquatic characteristics and functions, provided as background for considering the need and potential impacts of fuel treatments; (2) a review of the potential effects of prescribed fire and mechanical treatments on riparian and aquatic resources and biota; (3) results of an online survey of resource managers, summarizing information about proposed and completed fuel reduction projects in riparian areas and wetlands in the interior west; (4) suggestions for pre-and post project-level monitoring for riparian fuels projects; and (5) a presentation of case studies, describing riparian fuel treatments with different objectives and methods. Research on the effects of fuel treatments on riparian and aquatic resources is limited, and monitoring of projects is highly encouraged, especially in watersheds supporting species of concern. Results of the online survey showed that habitat restoration is a common objective for many fuel treatments that include riparian areas; for each of the case studies, restoration of near-stream habitat for wildlife was a major goal. The integration of riparian fuel treatments with other aspects of fire and watershed management could potentially improve riparian condition in multiple stream and vegetation types.
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Fire Ecology and Management in Lowland Riparian Ecosystems of the Southwestern United States and Northern Mexico
Technical Report
Full-text available
  • Sep 2019
Lowland riparian ecosystems, defined as those occurring at elevations at or below 5,000 feet (1,564 meters), constitute a small fraction of total land area in the southwestern United States and northern Mexico, yet they are extremely important to human livelihoods and biotic communities. In the hotter and drier conditions projected under ongoing climate change, riparian ecosystems are increasingly critical to the well-being of humans and wildlife. Riparian areas have been modified in various ways and to a large extent through human endeavor to utilize resources more predictably. These alterations often interfere with multiple and complex ecological processes, making riparian areas vulnerable to disturbance and change. Few naturally functioning riparian areas remain in the region, and those that do are imperiled by climate change, groundwater pumping, land use, and altered disturbance regimes. Some evidence suggests that fire regimes are changing in southwestern riparian zones; wildfires may be increasing in frequency and severity. This literature review summarizes and synthesizes the state of the knowledge of wildfire and prescribed fire effects on physical processes and vegetation, and postfire rehabilitation.Changing fire regimes are likely to have drastic and potentially irreversible effects on regional biodiversity and ecosystem function. However, options are available for managing riparian ecosystems that could make them more resilient to fire and climate change. This study is intended to inform management and identify gaps in systematically reviewed literature.
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