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Blanco river riparian forest regeneration following a record flood in Central Texas

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The Blanco River is a very important resource for water supplies in the Hill Country of central Texas. Some communities and properties along the river use the surface water directly. But, the Blanco River is more significant in the role it plays in providing recharge to the karstic Trinity and Edwards Aquifers. Recent studies have given a better indication of the complexity of the interactions between surface water and groundwater in the area. Besides being a water supply to a population of several hundred thousand people, water originally flowing in the Blanco River provides flow to springs that host a number of endangered species. The Blanco River is characterized by alternating gaining and losing stretches due to the presence of springs that discharge water into the river and swallets that drain water from the river. Trinity units outcrop in the western part of the study area, and Edwards units outcrop in the eastern part of the study area. Normal faulting along the Balcones Fault Zone has juxtaposed the older, stratigraphically underlying Trinity units against the Edwards units to the east. The region consists primarily of Lower Cretaceous limestone, dolomite, and marl. One of the more significant springs along the Blanco River is Pleasant Valley Spring. During below-average flow conditions, Pleasant Valley Spring becomes the headwaters of the Blanco River even though the headwaters, under wet conditions, are about 50 km upstream. These studies, summarized in this paper, provide a greater understanding of the surface water and groundwater resources in the area which will help guide policies for groundwater management and preservation of springflows and groundwater supplies.
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Streams in the plains of eastern Colorado are prone to intense floods following summer thunderstorms. Here, and in other semiarid and arid regions, channel recovery after a flood may take several decades. As a result, flood history strongly influences spatial and temporal variability in bottomland vegetation. Interpretation of these patterns must be based on understanding the long-term response of bottomland morphology and vegetation to specific floods. A major flood in 1965 on Plum Creek, a perennial sandbed stream, removed most of the bottomland vegetation and transformed the single-thread stream into a wider, braided channel. Channel narrowing began in 1973 and continues today. In 1991, we determined occurrences of 150 vascular plant species in 341 plots (0.5 m^2) along a 7-km reach of Plum Creek near Louviers, Colorado. We related patterns of vegetation to elevation, litter cover, vegetative cover, sediment particle size, shade, and year of formation of the underlying surface (based on age of the excavated root flare of the oldest woody plants). Geomorphic investigation determined that Plum Creek fluvial surfaces sort into five groups by year of formation: terraces of fine sand formed before 1965; terraces of coarse sand deposited by the 1965 flood; stable bars formed by channel narrowing during periods of relatively high bed level (1973-1986); stable bars similarly formed during a recent period of low bed level (1987-1990); and the present channel bed (1991). Canonical correspondence analysis indicates a strong influence of elevation and litter cover, and lesser effects of vegetative cover, shade, and sediment particle size. However, the sum of all canonical eigenvalues explained by these factors is less than that explained by an analysis including only the dummy variables that define the five geomorphically determined age groups. The effect of age group is significant even when all five other environmental variables are specified as covariables. Therefore, the process of postflood channel narrowing has a dominant influence on vegetation pattern. Channel narrowing at Plum Creek includes a successional process: annual and perennial plants become established on the channel bed, sediment accretes around the vegetation, and increasing litter cover, shade, and scarcity of water eliminate species that are not rhizomatous perennials. However, successional trajectories of individual surfaces are modified by flow-related fluctuations of the bed level; surfaces deposited by the 1965 flood have had distinct sediment and vegetation since their formation. Species richness is highest on surfaces dating to 1987-1990; the many species restricted to this transitory assemblage are perpetuated by flood-related fluctuations in channel width. Since the 1965 flood, seedling establishment of the dominant trees (genus Populus) has occurred only on low surfaces formed during channel narrowing. Thus, the flood has indirectly promoted Populus establishment over a 26-yr period.
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Loss of native riparian vegetation and dominance of invasive species can have negative consequences for river and floodplain dynamics, trophic interactions, water quality, and riparian systems’ ability to buffer some of the impacts of climate change. In response, restoration and enhancement efforts have increased in scope and scale in recent years, despite the fact that there is limited information on the effectiveness of techniques. This paper describes one approach to riparian restoration and enhancement, termed Rapid Riparian Revegetation (R3), which promotes rapid cover of woody plants in a composition designed to mimic reference site conditions. Limited peer-to-peer learning opportunities and the significant investment in time and resources required to document practices, monitor outcomes and disseminate findings hampers practitioners’ ability to both systematically improve ecological restoration practices and to share lessons learned with broader audiences. This paper seeks to narrow this gap by describing in detail riparian revegetation project planning, management actions, and costs incurred within typical grant funded projects. Initial planting densities prescribed in this approach are typically in the range of 5,400 to 6,400 stems per hectare (approx. 2,200 to 2,600 per acre), with inter-planting in the second year at 1,300 to 1,600 stems per hectare (approx. 530 to 650 per acre). Most sites are established over six to seven years at a total cost of $11,000 to $20,000 per hectare (approx. $4,500 to $8,100 per acre). This approach evolved in and is tailored to Oregon’s Willamette Basin, but principles and practices are applicable to other regions.
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In frequently burned ecosystems, many plants persist by repeated resprouting from basal or belowground buds. This strategy requires that plants reach a balance between biomass loss and recovery, which depends on the shape of the relationship between pre- and post-fire size. Previous analyses of this relationship, however, have focused on the size of the largest stem, which ignores the importance of the multi-stem growth habit that is common in pyrogenic ecosystems. We hypothesized that the presence of multiple stems causes a substantial shift in the relationship between pre- and post-fire size and in the relationship between pre-fire size and size recovery. We measured the height and basal diameter, then calculated volume and biomass, of all stems of six tree species before and nine months after complete removal of aboveground biomass via coppicing. The number of resprouts was correlated with the original number of stems for four species. For all species, the relationship between pre-coppicing and resprout size fit a positive curvilinear function, and the shape of this curve did not differ for maximum and total stem size. Smaller individuals recovered a larger proportion of their pre-coppicing size than larger individuals, but the shape of the size recovery curves were the same regardless of whether the analysis was performed with all stems or only the largest stem. Our results indicate that measuring only the largest stem of multi-stemmed individuals is sufficient to assess the ability of individuals to recover after complete loss of aboveground biomass and persist under frequent burning.
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The definitive version is available at http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-8137. Riparian vegetation is exposed to stress from inundation and hydraulic disturbance, and is often rich in native and alien plant species. We describe 35 traits that enable plants to cope with riparian conditions. These include traits for tolerating or avoiding anoxia and enabling underwater photosynthesis, traits that confer resistance and resilience to hydraulic disturbance, and attributes that facilitate dispersal, such as floating propagules. This diversity of life-history strategies illustrates that there are many ways of sustaining life in riparian zones, which helps to explain high riparian biodiversity. Using community assembly theory, we examine how adaptations to inundation, disturbance and dispersal shape plant community composition along key environmental gradients, and how human actions have modified communities. Dispersal-related processes seem to explain many patterns, highlighting the influence of regional processes on local species assemblages. Using alien plant invasions like an (uncontrolled) experiment in community assembly, we use an Australian and a global dataset to examine possible causes of high degrees of riparian invasion. We found that high proportions of alien species in the regional species pools have invaded riparian zones, despite not being riparian specialists, and that riparian invaders disperse in more ways, including by water and humans, than species invading other ecosystems.
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Woody cover, when expressed at the scale of the 207 km(2) Cusenbary Draw basin, remained unchanged (similar to 23%) from 1955 to 1990. When expressed at the scale of range sites, woody cover declined on sites with relatively high production potential and increased on sites with relatively low production potential. Change in woody cover distribution at sub-range site scales, increased low and high woody covers and decreased intermediate woody cover, would be expected to lead to increased water yield at the basin scale because there was an apparent threshold woody cover (similar to 20%) above which simulated evapotranspiration (ET) changed little with increasing woody cover. This potential increase, however, was more than offset by the decreased water yield due to increased ET loss associated with compositional changes of woody vegetation from oak to juniper. A set of woody cover-ET regression curves was developed for different range sites based on simulation studies using the SPUR-91 hydrologic model. Based on these woody cover-ET regression curves and GIS analysis, no brush management would result in a 35% decrease in water yield, while a hypothetical brush management cost-share program would increase water yield by 43% over the 1990 level. Benefits in water yield and forage production from brush management differ in different range sites. A brush management cost-share program that preferentially allocated brush management to sites with deep soil and the highest forage production potential increased water yield by 50%, compared to a 100% increase if brush management were preferentially allocated on sites with shallow soil and highest water yield potential. These model results illustrate that the spatial scale of assessment and spatial distribution of brush management among range sites should be important concerns associated with developing and evaluating brush management policies.
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Riparian zones possess an unusually diverse array of species and environmental processes. The ecological diversity is related to variable flood regimes, geograph-ically unique channel processes, altitudinal climate shifts, and upland influences on the fluvial corridor. The resulting dynamic environment supports a variety of life-history strategies, biogeochemical cycles and rates, and organisms adapted to disturbance regimes over broad spatial and temporal scales. Innovations in riparian zone management have been effective in ameliorating many ecological issues related to land use and environmental quality. Riparian zones play essential roles in water and landscape planning, in restoration of aquatic systems, and in catalyzing institutional and societal cooperation for these efforts.
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While some studies aim to generalise the attributes of woody encroachers, examining their functional differences across biogeographic regions may also be instructive. Most of Texas is encroached by Prosopis glandulosa, but on the eastern Edwards Plateau, a limestone plateau with thin soils, P. glandulosa is rare and Juniperus ashei is dominant. We hypothesised that P. glandulosa is excluded from sites where bedrock at a depth of 1 m or less restricts the development of taproots, thus rendering this normally deep-rooted species too vulnerable to drought. To test this idea, we monitored the physiological status of the two species on a site where both species were encroaching and the soil was 1·5–2·5 m deep, thus relatively deep for the Edwards Plateau region but not for regions where P. glandulosa dominates. Data were collected across three tree size classes from May to November 2006. Stem water potentials were similar across species and water potentials and photosynthetic rates decreased with tree size. Based on isotopic evidence, the effective rooting depth of P. glandulosa increased with tree size, but not in J. ashei. P. glandulosa had a higher rate of leaf gas exchange overall as expected for a drought-avoider; except for large trees during a summer drought, when species differences in photosynthesis rates diminished and the stomatal conductance for J.ashei exceeded that of P. glandulosa. We speculate that restrictions of soil depth may limit the invasiveness of P. glandulosa in part through negative effects on large trees, which may lower fecundity. Copyright © 2009 John Wiley & Sons, Ltd.
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The Blanco River, which flows through the limestone Balcones Canyonlands of central Texas (USA), experienced catastrophic flooding in May 2015 that resulted in significant biogeomorphic disturbance to its riparian corridor. High-resolution aerial and satellite imagery from pre- and post-flooding for a 55-km reach of river were used to map and categorize patterns of disturbance by degree of severity ranging from complete floodplain stripping to no disturbance. The most severe disturbance occurred within the floodway near the channel and decreased with lateral distance into the 100- and 500-year floodplains. Disturbance patterns previously identified in the literature including meander scour, parallel chute scour, convex bank erosion, and macroturbulent scour were all present following this event, as well as substantial disturbance proximal to tributary confluences. In the aftermath of this event, TreeFolks, a local nonprofit organization, engaged with the community to actively replant and restore the riparian corridor of the Blanco River on public and private lands. These reforestation efforts supplement the natural passive recovery of the riparian corridor, enabling the system to recover more quickly and be resilient to future flood events.
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Flooding and sediment deposition provide many benefits to riparian plants, including dispersal of propagules, new seedbeds for germination, and transient pulses of water and nutrients during early growth. Though many riparian species are adapted to flood disturbance, sediment deposition can also be a stressor to existing plants, limiting their survival and growth. Though many field studies document short-term changes in plant density immediately following floods, an outstanding question remains to what degree plants can survive and re-emerge following fluvial deposition events. We conducted two year-long studies to quantify the response of riparian trees to sediment deposition, testing a range of species, sizes and burial depths. One experiment focused on long-term survival following complete burial for seedlings and saplings of cottonwood (Populus fremontii), tamarisk (Tamarix ramosissima), and box elder (Acer negundo). A second experiment focused on cottonwood seedling response to more moderate deposition events, comparing survival and vigor (height, diameter growth, and leaf production) across a range of treatments from 10 to 50 cm sediment depth. Complete burial killed all tamarisk and cottonwood plants; however all box elder survived and resprouted from the sediment surface in the following growing season. In the partial burial experiment, cottonwood survival was higher in the shallower deposition treatments and for larger plants across all treatments. Cottonwood seedlings with exposed stem length longer than ∼20 cm were highly likely to survive (>90%), whereas plant survival was severely reduced for stems with greater portions of their stems buried. Seedlings that survived partial burial experienced a positive, compensatory response in the following growing season, with height increment and canopy expansion proportional to the depth of sediment added. These results suggest that flood-borne sediment deposition events, either under natural or river management conditions, may have non-linear effects on the survival of existing riparian tree cohorts. The severity of the disturbance effects will depend on the magnitude of the event and the initial size of the plants. Together with field studies on riparian plant demography and experiments that test plants’ vulnerability to flood disturbance, our study extends understanding of the drivers of plant mortality in fluvial corridors.
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Abandoned meanders are former river meanders cut-off from the active channel that occur in the floodplain in various stages of infilling. Their compositional diversity, ecological function, and persistence are highly variable in space and time. This study examines the spatial variability of vegetation dynamics, logging history, and hydrogeomorphic controls on abandoned meander forests in the Congaree River floodplain, South Carolina. The methods used for this study combine field-based vegetation (structure and composition) surveys with high-resolution digital terrain models, and 2D hydrodynamic modeling, soils data, and logging histories to explain spatial variability in forest patterns and hydrogeomorphic conditions. Annual duration and frequency of hydrologic connectiv ity to flood waters, topographic complexity, and logging history explained the greatest variability between sites. Un-logged old-growth forests were the most diverse, and differences in the canopy and understory demonstrated a long term process of species turnover indicative of changing hydrogeomorphic conditions from more hydric to less hydric as the abandoned channel continues to infill. Selective logging for Taxodium distichum (bald cypress) and clear cut logging created abrupt changes to community composition, whereby the recovering forests did not return to pre-disturbance assemblages. Landscape scale variability in hydrogeomorphic conditions and species biological tolerances controlled recruitment of the second-growth forests producing diverse structural and compositional patterns. The extent and intensity of logging impacts to T. distichum had not been previously documented, and its recovery within the floodplain is a major management concern particularly on account of current dam-related flow alterations. Floodplain forests dynamics of Eastern Coastal Plain river systems are ideal indicator sites for monitor ing and predicting ecosystem responses to natural and human-induced changes. Sustainable management of these forests are critical to their future health.
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Publisher Summary This chapter describes the various geomorphic and hydrologic processes such as catchments that influence riparian system development and maintenance. Catchments are areas of the land surface in which all the runoff drains to a single point on a stream or river channel, and are bounded by drainage divides; catchments have been known to range from hundreds of square meters in size to millions of square kilometers. Catchment drainage networks may have dendritic, palmate dendritic, or trellised forms, depending on the nature of underlying geology. These networks vary in drainage density and gradient, which affect riparia by impacting flood intensity and stream power, respectively. The most basic geomorphic processes in catchments are erosion, transport, and deposition. These processes operate across all time and space scales but vary in relative importance along drainage networks. Erosive processes dominate headwater regions, whereas deposition processes dominate the bottom of catchments draining to the ocean or into enclosed basins. Transport dominates in the mid-reaches of river systems. Erosion scours and eliminates riparian habitats and occurs when the shear stress imposed by flowing water exceeds the shear strength of the material over which it flows. The dominant forms of erosion include down-cutting and lateral movement of channels and scouring of channels and floodplains. Hydrologic processes strongly influence riparian habitats as the transport medium for sediments, but the presence or absence of water by itself is also an important control on riparian form and function. Flooding is a key process that distributes surface water to riparian environments and sets up gradients that drive surface water-groundwater exchanges. Four characteristics of floods, which are especially important to riparian and floodplain ecosystems are magnitude, frequency, timing, and duration.
Article
QuestionsDoes flooding reduce the prevalence of exotic plant species and promote native riparian plant species?LocationField study, two regulated lowland rivers, SE Australia.Methods We used a large flood in spring to test predictions of vegetation response to flooding. We predicted that the species richness of exotic taxa (mostly terrestrial annual/biennial grasses and forbs in the study systems) would be reduced by flooding, while the richness of native riparian species adapted to fluvial disturbance would increase. We surveyed the riparian vegetation at three sites on each of two regulated rivers in the summers before and after a large flood in early spring that inundated all of the sites on one river, and one site on the other river; the remaining sites were not flooded. Overall, the study was a natural experiment with a before–after control–impact design.ResultsAs predicted, flooding dramatically reduced the richness of exotic taxa, particularly of terrestrial grasses. However, some invasive flood-tolerant exotic taxa, such as blackberries and willows, were promoted by the floods. Flooding reduced the cover of most native taxa, but did not affect overall native taxon richness. In contrast, the richness and cover of native summer annuals increased following the flood.Conclusions Our study provides evidence to support the use of managed floods to reduce the prevalence of terrestrial exotic taxa within the riparian zones of regulated rivers. The frequency and intensity of flow pulses necessary to keep terrestrial exotics at low levels requires further research.
Article
1. Effects of the frequency and duration of flooding on the structural and functional characteristics of riparian vegetation were studied at four sites (n = 80, 50 × 50 cm, plots) along medium-sized naturally meandering lowland streams. Special focus was on rich fens, which – due to their high species richness – are of high priority in nature conservation. 2. Reed beds, rich fens and meadows were all regularly flooded during the 20-year study period, with a higher frequency in reed bed areas than in rich fen and meadow areas. In rich fens, species richness was higher in low frequency flooded areas (≤3 year−1) than in areas with a high frequency of flooding (>3 year−1) or no flooding, whereas species richness in reed beds and meadows was unaffected by flood frequency. 3. The percentage of stress-tolerant species was higher in low intensity flooded rich fen areas than in high intensity and non-flooded areas, indicating that the higher species richness in low frequency flooded rich fens was caused by competitive release. We found no indication that increased productivity was associated with high flooding frequencies. 4. We conclude that the restoration of morphological features in stream channels to increase the flooding regime can be beneficial for protected vegetation within riparian areas, but also that groundwater discharge thresholds and critical levels for protected vegetation should be identified and considered when introducing stream ecosystem restoration plans.
Article
The October 1998 flood on the upper Guadalupe River system was produced by a 24-hour precipitation amount of 483 mm at one station, over 380 mm at several other stations, and up to 590 mm over five days, precipitation amounts greater than the 100-year storm as prescribed in Weather Bureau Technical Papers 40 (1961) and 49 (1964). This study uses slope-area discharge estimates and published discharge and precipitation data to analyze flow characteristics of the three major branches of the Guadalupe River on the Edwards Plateau. The main channel of the Guadalupe has a single large flood-control structure at Canyon Dam and five flood dams on the tributary Comal River. On the upper San Marcos River there are five detention dams that regulate 80% of its drainage. The Blanco River, which has no structural controls, generated a peak discharge of 2,970 m3/s from a 1,067 km2 basin. Downstream of Canyon Dam, the Guadalupe River generated a peak discharge greater than 3,000 m3/s from an area of 223 km2. The event exceeded the capacity of both the Comal River and San Marcos flood-control projects and produced spills that inundated areas greater than the 100-year floodplain defined by the Federal Emergency Management Agency.
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1 The Bogue Chitto River, Louisiana, USA, is a meandering river with 16 early successional tree species having > 1% relative dominance. We hypothesized that geomorphic processes associated with river planform promote predictable spatial patterns of tree species within each river bend by influencing the physical conditions under which the forest is initially established. We predicted that (i) species of trees differ in their location of recruitment along the point bar, and trees on older land reflect the spatial patterns of recent recruits; (ii) the location of recruitment differs among tree species in elevation, soil texture, herbaceous cover and light; and (iii) a specific pattern of elevation, soil texture and tree species in the earliest stage of forest succession characterizes multiple river bends in a reach.
Article
The geomorphic effectiveness of extreme floods increases with aridity and decreasing watershed size. Therefore, in small dry watersheds extreme floods should control the age structure and spatial distribution of populations of disturbance-dependent riparian trees. We examined the influence of extreme floods on the bottomland morphology and forest of ephemeral streams in a semiarid region. Along six stream reaches on the Colorado Piedmont we examined channel changes by analyzing a rectified sequence of aerial pho-tographs spanning 56 yr, and we investigated the spatial distribution of different-aged patches of forest by aging 189 randomly sampled cottonwood trees. Channel change in these ephemeral sand-bed streams is dominated by widening, which occurs over a span of hours during infrequent floods, and postflood narrowing, which occurs over decades between floods. Narrowing is accelerated where reliable moisture increases the density and growth rate of vegetation on the former bed. Reproduction of cottonwood trees has occurred mostly in former channel bed during periods of channel narrowing beginning after floods in 1935 and 1965 and continuing for as long as two decades. Thus cottonwood establishment is related to low flows at the time scale of a year, but to high flows at the time scale of decades. At sites that have not experienced major floods in the last 80 yr, little channel change has occurred, cottonwood reproduction has been limited, tree density has declined, and succession to grassland is occurring. Because channel change and tree reproduction in this region are driven by infrequent local events, channel width and tree age distributions vary greatly over time and among sites. For the same reason, riparian forests along these ephemeral streams can be as wide as forests along perennial rivers with much higher mean discharge.
Article
1. This paper introduces key messages from a number of papers emanating from the Second International Symposium on Riverine Landscapes held in August 2004 in Sweden, focusing on river restoration. Together these papers provide an overview of the science of river restoration, and point out future research needs. 2. Restoration tests the feasibility of recreating complex ecosystems from more simple and degraded states, thereby presenting a major challenge to ecological science. Therefore, close cooperation between practitioners and scientists would be beneficial, but most river restoration projects are currently performed with little or no scientific involvement. 3. Key messages emanating from this series of papers are: The scope, i.e. the maximum and minimum spatial extent and temporal duration of habitat use, of species targeted for restoration should be acknowledged, so that all relevant stages in their life cycles are considered. Species that have been lost from a stream cannot be assumed to recolonise spontaneously, calling for strategies to ensure the return of target species to be integrated into projects. Possible effects of invasive exotic species also need to be incorporated into project plans, either to minimise the impact of exotics, or to modify the expected outcome of restoration in cases where extirpation of exotics is impractical. 4. Restoration of important ecological processes often implies improving connectivity of the stream. For example, longitudinal and lateral connectivity can be enhanced by restoring fluvial dynamics on flood-suppressed rivers and by increasing water availability in rivers subject to water diversion or withdrawal, thereby increasing habitat and species diversity. Restoring links between surface and ground water flow enhances vertical connectivity and communities associated with the hyporheic zone. 5. Future restoration schemes should consider where in the catchment to locate projects to make restoration most effective, consider the cumulative effects of many small projects, and evaluate the potential to restore ecosystem processes under highly constrained conditions such as in urban areas. Moreover, restoration projects should be properly monitored to assess whether restoration has been successful, thus enabling adaptive management and learning for the future from both successful and unsuccessful restorations.
Article
Using a series of aerial photographs taken between 1936 and 1996, we trace coevolution of floodplain and r par an forest on the Willamette River. Within-channel barforms appear to be the predominant incipient floodplain landform and habitat for primary succession. Interlinked development of bar(s) and erosion of near banks, filling of channels, and establishment and growth of cottonwoods and willows results in coalescence with older floodplain. Size and internal structure of riparian forest patches reflect evolution of underlying barforms or channel beds. Floodplain matures as the active channel migrates away by repetition of the bar formation and near-bank erosion process, or is progressively abandoned by infilling and/or constriction with a bar. Other parts of the floodplain are recycled as eroding banks provide the coarse sediment and large woody debris for building new bars. A multichannel planform is maintained as building bars split flow; channels lengthen as bars and islands join into larger assemblages. Avulsion appears to cut new channels only short distances. Given the central role of bars and islands in building new floodplain habitat, we identify their area as a geomorphic indicator of river-floodplain integrity. We measure an 80% decline in bar and island area between 1910 and 1988 within a 22-km section. Dams, riprap, logging, and gravel mining may all be contributing to diminished bar formation rates. Removing obstacles to natural riparian forest creation mechanisms is necessary to regenerate the river-floodplain system and realize its productive potential.
Article
In the early 1900s, baldcypress swamps were harvested en masse in coastal Louisiana, USA. In many areas, natural regeneration did not occur; instead, these areas converted to marsh or open water. One of the factors that may have been responsible for the lack of regeneration was shading of newly-germinated seedlings by herbaceous vegetation. Alternatively, prolonged flooding or complete submergence may have suppressed germination or growth rates of young seedlings and even caused mortality. This study investigated the effects of complete submergence and variable light regime on two age classes of baldcypress seedlings. Newly-germinated seedlings (under two weeks of age) subjected to complete submergence began to show clear signs of stress after approximately one month and substantial mortality following 45 days of submergence. In contrast, one-year-old seedlings submerged for as much as five months experienced up to 75% survival. In a four-way factorial experiment, two age classes of baldcypress seedlings were subjected to five light transmissions (100%, 80%, 50%, 30%, 20%), five flood durations (0 days, 14 days, 25 days, 35 days, 45 days), and two nutrient regimes (fertilized vs. not fertilized). At 100% light transmission, the newlygerminated seedlings suffered complete mortality after 35 days of submergence, whereas the one-year-old seedlings were largely unaffected by prolonged flooding or light regime. Fertilized one-year-old seedlings that were submerged for an entire month had considerably greater growth in height and diameter than seedlings grown under mesic conditions without fertilizer. This is particularly important in coastal Louisiana because several re-introductions (i.e., diversions) of Mississippi River water into declining swamps are planned or underway, and these diversions will periodically increase nutrient and flood levels.
Article
Lateral channel migration initiates complex and dynamic biogeomorphic responses that are fundamental to the creation and maintenance of riparian habitats along low-gradient, coastal plain rivers. This study examines the effects of lateral migration rates on the structure and composition of riparian forests along the Congaree River, Congaree National Park, in the Atlantic Coastal Plain, South Carolina. Lateral channel migration rates were measured in a GIS using aerial photos from 1938–2006. Forest variables were measured from a stratified-random sample of 25 paired edge-interior plots, and analyzed using Mann-Whitney tests, Spearman’s correlations, multi-response permutation procedures (MRPP), and non-metric multi-dimensional scaling (NMS) ordinations. Lateral channel migration produced a significant directional control on riparian forests. Pointbar forests exhibited classic forward succession dependent on spatial and temporal controls related to elevation, flood frequency, and lateral migration rates. Cutbank forests responded positively to exposure along the edge and increased in structural complexity with increasing proximity to the river; density, basal area, and richness varied inversely with lateral migration rates. Cutbank edges with low lateral migration allowed longer time for trees to colonize and they contained greater density, basal area, and richness. Cutbanks with high lateral migration contained lower tree density, basal area, and richness.
Article
Most research before 1960 into interactions among fluvial processes, resulting landforms, and vegetation was descriptive. Since then, however, research has become more detailed and quantitative permitting numerical modeling and applications including agricultural-erosion abatement and rehabilitation of altered bottomlands. Although progress was largely observational, the empiricism increasingly yielded to objective recognition of how vegetation interacts with and influences geomorphic process. A review of advances relating fluvial processes and vegetation during the last 50 years centers on hydrologic reconstructions from tree rings, plant indicators of flow- and flood-frequency parameters, hydrologic controls on plant species, regulation of sediment movement by vegetation, vegetative controls on mass movement, and relations between plant cover and sediment movement.
Article
A basic knowledge of the origin, development, and ecology of bottomland hardwood sites is important for assessing harvesting impacts on those sites. This paper presents an overview of the geologic origin and development of hardwood sites, species-site relationships and the natural patterns of ecological succession on those sites, and the implications of that information for forest management. Bottomland hardwoods occur on floodplain sites primarily in the Atlantic and Gulf Coastal Plains. Past geologic events led to the formation of broad stream valleys in those areas because of the erodible, sedimentary geologic materials. Natural patterns of ecological succession on floodplain sites are influenced by autogenic and allogenic processes in that the sites may undergo constant change because of deposition. Three natural patterns of succession are recognized for floodplain sites of major river bottoms—those occurring on permanently flooded sites, those on low elevation wet sites, and those on higher elevation, better drained sites. Floristic composition and successional patterns are strongly influenced by the hydrologic events on the sites and particularly by rates and types of deposition.
Article
Riparian vegetation and fluvial-geomorphic processes and landforms are intimately connected parts of the bottomland landscape. Relations among vegetation, processes, and landforms are described here for representative streams of four areas of the United States: high-gradient streams of the humid east, coastal-plain streams, Great Plains streams, and stream channels of the southwestern United States. Vegetation patterns suggest that species distributions in the humid east are largely controlled by frequency, duration, and intensity of floods. Along channelized streams, vegetation distribution is largely controlled by variation in fluvial geomorphic processes (cycles of degradation and aggradation) in response to increases in channel gradient associated with channelization. Similarly, riparian vegetation of Great Plains streams may be controlled by fluxes in sediment deposition and erosion along braided streams. Patterns of riparian vegetation in semi-arid regions may be most closely related to patterns of water availability, unlike most other streams in more humid environments. Channel-equilibrium conditions control stability of the coincident fluvial landform and attendant vegetation pattern throughout the continent. In most situations, riparian-vegetation patterns are indicative of specific landforms and, thus, of ambient hydrogeomorphic conditions.
Article
Thesis (Ph. D.)--University of Oklahoma, 1935. Includes bibliographical references (leaves 124-140).
Dynamic floodplain vegetation model development for the Kootenai River, USA
  • R Benjaker
  • G Egger
  • K Jorde
  • P Goodwin
BENJAKER, R., G. EGGER, K. JORDE, P. GOODWIN, AND N. GLENN. 2011. Dynamic floodplain vegetation model development for the Kootenai River, USA. Journal of Environmental Management 91:3058-3070.
  • M Gaskill
GASKILL, M. 25 September 2015. Run, river, run. Newsweek 58.
Effects of herbivory and flooding on reforestation of baldcypress (Taxodium distichum [L.]) saplings planted in Caddo Lake
  • B Keeland
  • R Draugelis-Dale
  • R Daville
  • J Mccoy
KEELAND, B., R. DRAUGELIS-DALE, R. DAVILLE, AND J. MCCOY. 2011. Effects of herbivory and flooding on reforestation of baldcypress (Taxodium distichum [L.]) saplings planted in Caddo Lake, Texas. Texas Journal of Science 63:47-68.