Riparian vegetation

This study examined the patterns of plant functional trait variation in relation to geomorphology, disturbance and a suite of other environmental factors in the riparian margin of the Upper Hunter River, New South Wales, Australia. Vegetation was surveyed on three geomorphic surfaces (point bar, bench and bank) along a 5.5-km stretch of the Upper Hunter River. Functional traits relating to plant growth and reproduction were collected for the identified species. anova and principal components analysis were used to compare the trait assemblages of species associated with each geomorphic unit. Pearson's correlation coefficients were used to investigate trait variation with respect to environmental variables. There were clear differences in the plant functional trait assemblages associated with the three geomorphic units. Generally the point bar was associated with species that were herbaceous, with small seed mass, a short stature and a high specific leaf area (SLA). Conversely, the bench was associated with grasses that had unassisted seed dispersal and intermediate seed mass and SLA, while species on the bank had tall stature, large seed mass, a high SLA and a perennial life cycle. Variation along the primary gradient of plant functional trait composition was most strongly related to disturbance frequency and to a lesser extent soil nutrients and the proportion of clay and silt, while variation along the secondary gradient was associated with variation in substrate texture as well as soil nutrients.

Over the past 35 years, a trend of decreasing water clarity has been documented in Lake Tahoe, attributable in part to the delivery of fine grained sediment emanating from upland and channel erosion. A recent study showed that the Upper Truckee River is the single largest contributor of sediment to Lake Tahoe, with a large proportion of the sediment load emanating from streambanks. This study combines field data with numerical modeling to identify the critical conditions for bank stability along an unstable reach of the Upper Truckee River, California. Bank failures occur during winter and spring months, brought on by repeated basal melting of snow packs and rain-on-snow events. Field studies of young lodgepole pines and Lemmon's willow were used to quantify the mechanical, hydrologic, and net effects of riparian vegetation on streambank stability. Lemmon's willow provided an order of magnitude more root reinforcement (5.5 kPa) than the lodgepole pines (0.5 kPa); the hydrologic effects of the species varied spatially and temporally and generally were of a smaller magnitude than the mechanical effects. Overall, Lemmon's willow provided a significant increase in bank strength, reducing the frequency of bank failures and delivery of fine grained sediment to the study reach of the Upper Truckee River.

Riparian vegetation and management of surface water, the case of the Inaouène-Wadi watershed (NW Morocco). Integrated management of water resources interfere, directly or indirectly, with the biodiversity conservation. In Morocco, most studies on plant diversity of wetland interested especially ecological and functioning aspects. In this work, we tried to establish a relationship between human activities (planning, pollution …) and wetland flora and its conservation status. The specific plant diversity (Spermatophyta and Pteridophyta) of the Inaouène River was estimated based on the riparian flora exploration of 21 stations. The main ecological and anthropogenic factors (sampling, planning …) affecting plant groups were discussed as elements interfering with the rivers management. The study highlights the dependence of the population vis-à-vis plant resources, which may have a negative impact on surface water, and more rational measures should be taken, namely the plantation of the ...

Riparian vegetation performs important
ecosystem functions, since it maintains regional
biodiversity and provides a range of environmental
services. However, anthropogenic activity, land use
type, and edge effects are factors that modify the
riparian species assemblage and properties. The
present study analyzes the influence of adjacent land
use on the structure and diversity of riparian vegetation
in four hydrographic regions that form the
watershed of the river Duero, in the state of Michoaca
´n, Mexico. Using a survey of woody plants of dbh
C 2.5 cm in ten different 0.1 ha sites, we found that
the average number of stems and individuals was
lower under agricultural (AGR) and urban (URB) land
use, compared to forested areas (FOR). The proportion
of multistemmed plants differs among land uses: this
value was greater in AGR than in the FOR and URB
categories. This proportion also differed among the
four hydrographic regions. The land use type FOR
presented the highest alpha and beta diversity, with a
high number of native species occurring only in areas defined by this land use. The results indicate that the
category FOR plays an important role in the conservation
of regional flora and is a possible source of
germplasm for restoration programs in sites degraded
by human disturbance. This study shows how anthropogenic
activities affect riparian vegetation and highlights
the importance of further study of this
ecosystem to apply sustainable management strategies
that are compatible with its conservation.

A modular procedure to assess the magnitude, distribution, and potential for channel instabilities at a large number of sites has been designed and implemented. The procedure, based on diagnostic interdisciplinary criteria of alluvial channel morphology and associated riparian vegetation, is presented. The modules include (1) initial site evaluations, (2) GIS-based data input and management, (3) ranking of relative channel stability, (4) identification of spatial trends, (5) ranking of socio-economic impacts and identification of most “critical” sites, and (6) collection of additional field data for more detailed evaluation of the magnitude and type of future instabilities and the effects of proposed mitigation measures. The procedure, using site evaluation forms as the fundamental means of data collection, takes a trained person 1 to 1.5 hours to complete. Site evaluation forms can be altered according to the specific environment being studied and the objectives of the study.An objective ranking scheme based on physical attributes extracted from the GIS data base permits the identification of the most unstable channel sites and, thereby, focuses attention on potentially “critical” sites. If a significant concern about a bridge or adjacent lands arises, or if mitigation measures are considered, various methods to estimate future channel changes are proposed. These include (1) numerical alluvial channel modeling, (2) empirical models of channel evolution, (3) regime equations, and (4) empirical relations based on process dominance in different fluvial environments. The methods require differing amounts of additional field data and provide results of varying detail and accuracy. The decision on which method to use must be based on the objectives and resources of the agency involved in the evaluation study.

Main channel and floodplain vegetation generally influence the flow behaviour in the flooding rivers or compound channels. The hydraulics of vegetated compound channels is complex and still not fully understood. The aim of the research was to enhance the knowledge on the effects of two-line staggered arrays with closed-spacing emergent vegetation or roughness elements along the riparian zone on the non-mobile bed compound straight and meandering channels flows. The experiments were carried out in the hydraulics laboratory of Faculty of Civil Engineering, Universiti Teknologi Malaysia. The experimental investigations were focused on an asymmetrical compound straight channel and a straight, vertical floodplain-walls meandering channel with a sinuosity of 1.54. In addition, the Shiono and Knight Method (SKM) was examined to simulate the transverse distributions of velocity in non-vegetated and vegetated compound straight channels. The physical processes experimentally investigated were stage-discharge, flow resistance, three-dimensional turbulent flow structures, boundary shear stress, momentum transfer and drag force for selected flood flow depths in both compound channels. The densest riparian vegetation increased 6.1% and 32% of flow depth in compound straight and meandering channels, respectively. It also generated the largest flow resistance in both channels. The secondary currents movements were limited due to the presence of floodplain vegetation and the current strength in meandering channel was stronger than in straight channel. The floodplain vegetation also lowered boundary shear stress and a maximum of 77.8% boundary shear stress drop was observed for the densest vegetation case in compound meandering channel. Momentum transfers between main channel and floodplain were quantified as transverse Reynolds and apparent shear stresses. Peak stresses were found in the shear layer zones and increased with density of riparian vegetation. The vegetative-induced drag force FD was calculated using force balance approach and the result showed that it increased with flood flow depth. In addition, the smallest riparian vegetation spacing produced the largest drag coefficient CD in both non-mobile bed compound channels. The hydraulic simulations showed that SKM was able to produce well prediction of the depth-averaged velocity in non-vegetated and vegetated compound straight channels. The findings also revealed that compound meandering channel flow was more complex since its structures were spatially varied along the meander due to channel geometrical properties.

Includes only chapter 1 and 7, see other chapters main page.

Rivers have distinctive channel patterns such as multi-channel braiding and single-channel meandering. Why these different river patterns emerge is only qualitatively understood. Yet, we have not been able to retain dynamic meandering in laboratory experiments. The main objective of this thesis was to develop experimental settings in the laboratory that lead to dynamic meandering, in order to determine how rivers self-organize their morphology through interactions between channels, floodplain and vegetation. I unraveled these interactions in a series of controlled flume experiments. I found that classical similarity scaling as used in engineering scale models does not work well because the channel width-depth ratio that determines bar formation is a dependent parameter in self-formed channels. Therefore, I relaxed the scaling rules. Systematic small-scale tests showed that there is a narrow range of suitable conditions for continuous meandering regarding sediment mobility and bank strength. Initially, in a straight channel with a low width-depth ratio alternate bars develop and evolve into meander bends. An upstream perturbation is required to initiate bar formation, but the experiments showed that a static perturbation led to low amplitude bends. In contrast, a transversely moving inlet point caused high-amplitude dynamic meandering with scrolls bars and infrequent chute cutoffs. Floodplain development further defined the resulting river pattern. In experiments with only channel sediment, overbank flow led to chute cutoffs that terminated meander bend development and that were the onset of a braided river with multiple parallel channels. Bank erosion by bend migration is balanced by deposition of sediment forming new floodplains and cutoffs, as also confirmed by numerical modeling. I showed that vegetation and fine sediment on the floodplain decreased the number of chute cutoffs, allowing meander bends to grow further. The fine sediment adds cohesion to the floodplain and increased bank strength, while plants increased bank strength and roughness. The combination of flume experiments and numerical model results shows that channel dynamics are controlled by bankfull discharge conditions, but overbank flow is highly important in constructing and destroying the floodplain. The composition of the floodplain, e.g. cohesion of the banks and the presence of vegetation, determines whether a braided or a meandering river pattern develops.

Resumen.- El objetivo de este trabajo es analizar los cambios ecológicos operados en la cuenca del Río Cruz del Eje, mediante la interpretación de la historia socioeconómica, la escala antropológica, como evidencia de los cambios en el uso de la tierra y el agua. Se analizan las era Indígena (6000 A.C. 1528), era Colonial (1528 1810), era Criolla (18l0 1880 y era Aluvial (1880 en adelante) y se desarrolla la cronología de aquellos eventos históricos relevantes que produjeron cambios en la configuración del paisaje fluvial. Se reconocen intervenciones y actividades que actúan como factores que se ha comprobado son causantes de la disminución de la biodiversidad, el aumento de la erosión y el empeoramiento de la calidad del agua.

Summary. - The objective of this paper is to analyze the ecological changes operated in the Cruz del Eje river basin, through interpretation of the socioeconomic history, an anthropological scale, as evidence of changes in land and water usage. The periods considered were Indian era (6000 AC- 1528), Colonial era (1528 -1810), Creole era (18l0 -1880) and Alluvial era (1880 onwards). It is developed the chronology of those historical events that caused changes, in relevant settings riverscape. Interventions and activities are recognized as factors known causing the decline of biodiversity, the increased erosion and the deterioration of water quality.

We present a regional land-use history of the Palouse bioregion of southeastern Washington and west-central Idaho. Our objectives were to develop a history of European-American settlement and biological diversity in the region and use this history to understand how human activities have altered the land cover and ecological integrity of the Palouse bioregion. We compiled and interpreted available information on

Rivers are conduits for materials and energy; this, the frequent and intense disturbances that these systems experience, and their narrow, linear nature, create problems for conservation of biodiversity and ecosystem functioning in the face of increasing human influence. In most parts of the world, riparian zones are highly modified. Changes caused by alien plants — or environmental changes that facilitate shifts in dominance creating novel ecosystems — are often important agents of perturbation in these systems. Many restoration projects are underway. Objective frameworks based on an understanding of biogeographical processes at different spatial scales (reach, segment, catchment), the specific relationships between invasive plants and resilience and ecosystem functioning, and realistic endpoints are needed to guide sustainable restoration initiatives. This paper examines the biogeography and the determinants of composition and structure of riparian vegetation in temperate and subtropical regions and conceptualizes the components of resilience in these systems. We consider changes to structure and functioning caused by, or associated with, alien plant invasions, in particular those that lead to breached abiotic- or biotic thresholds. These pose challenges when formulating restoration programmes. Pervasive and escalating human-mediated changes to multiple factors and at a range of scales in riparian environments demand innovative and pragmatic approaches to restoration. The application of a new framework accommodating such complexity is demonstrated with reference to a hypothetical riparian ecosystem under three scenarios: (1) system unaffected by invasive plants; (2) system initially uninvaded, but with flood-generated incursion of alien plants and escalating invasion-driven alteration; and (3) system affected by both invasions and engineering interventions. The scheme has been used to derive a decision-making framework for restoring riparian zones in South Africa and could guide similar initiatives in other parts of the world.

The Białowieża Primeval Forest (BPF) is the only forest area in temperate Europe where forest communities have developed a natural stand structure and a natural distribution of coarse woody debris ((CWD)=standing dead trees (SDT)+down woody material (DWM)). Stand and dead wood characteristics are influenced by ancient and recent historical factors and current processes, such as fires, competitive exclusion, storms, insect outbreaks, and forest management. The aim of the present study was to relate CWD to stand characteristics in mesic deciduous forest (Tilio–Carpinetum (TC)) and riparian forest (Circaeo–Alnetum (CA)). Direct comparison of managed forest to protected forest provides information about the impact of the forestry practices on TC stand and CWD characteristics. Approximately two-fold larger volume of trees was found in the Białowieża National Park (BNP) TC stands (from 336 to 555 m3 ha−1) than in the commercial forest ((CF), from 239 to 279 m3 ha−1). Irregular distribution of “legacy trees” (DBH>90 cm) accounted for most of the variability among the TC BNP stands. Even stronger differences within TC stands were revealed among the various developmental phases (from 147 m3 ha−1 in degradation phase to 630 m3 ha−1 in biostatic-optimal phase). Difference in rate of stand development was responsible for the variability of tree volume within CA (338 m3 ha−1 in early succession stand versus 634 m3 ha−1 in close-to-climax stand). CWD (mostly DWM) contributed about one-quarter of the total above ground wood biomass in BNP TC and CA ecosystems, ranging from 87 to 160 m3 ha−1. Higher relative abundance of spruce in DWM than in living stand volume and more spruce in old debris than in fresh debris suggests that the end of the spruce mortality wave was imminent. As a consequence, structural and dynamic changes in favour of smaller regeneration units are expected. A mere vestige of CWD was found in the CF ecosystem. Both stand and CWD data show a negative impact of former management on the forest ecosystems. In conclusion, special measures aimed at the restoration of ecological capacity of forest communities, including legacy retention and management for decadence, have been recommended. There is an urgent need for complementary studies to supply information necessary for successful adaptive management of the Białowieża Primeval Forest.

Die Trinkwassergewinnung stellt nicht nur eine extensive Form der Landnutzung dar, sie ist auch mit Restriktionen hinsichtlich des landwirtschaftlichen Einsatzes von Dünge- und Pflanzenschutzmitteln innerhalb der Schutzgebietszone verbunden, welche zur Entstehung und zum Erhalt von für den Naturschutz wertvollem, artenreichem Magergrünland führen können. Nach Beendigung der Trinkwassergewinnung unterliegen diese Flächen oft der Gefahr einer weniger umwelt- und naturschutzverträglichen Landbewirtschaftung, so dass eine administrative Sicherung solcher wertvollen Flächen sinnvoll ist. Dabei gilt es zu ermitteln, welche Schutzgüter im betreffenden Gebiet
vorkommen und welche Qualitäten wertgebend für ein Schutzgebiet sind. Anhand des vorliegenden Beitrages soll dargestellt werden, welche naturschutzfachlichen Wertigkeiten die Flächen einer ehemaligen Trinkwassergewinnung in der Ruhraue in Bochum-Stiepel aufweisen und wie sie planerisch einzuordnen sind, damit sie durch adäquate Pflege- und Entwicklungsmaßnahmen langfristig erhalten werden können. Des Weiteren soll die floristische und vegetationskundliche Bedeutung des vorhandenen Grünlandes im regionalen Kontext für den Bochumer Raum und für das Ruhrgebiet dargestellt werden. Dabei werden aus pflanzengeographischer und naturschutzfachlicher Sicht bemerkenswerte Taxa der Gefäßpfl anzen gesondert kommentiert und der naturschutzfachliche Wert des Gebietes diskutiert.