1- Introduction:
A. Definition of riparian zones
Even though the meaning of riparian zone has subsequently been extended to accommodate an immense strip of land alongside channels (Malanson, 1993), the fundamental meaning known to the majority of the people includes only vegetation along the bed as well as banks of river channels and streams (Tanskey, 1911). The floodplain and the riparian zone are now often taken to be one and subsequently, the same entity. Riparian zones are ecological boundaries, or ecotones, that physically separate terrestrial and aquatic ecosystems (Burt T.P et al, 2002). The riparian ecotones are vital regulators of material movement through the catchment system and, thus their ecological significance and management potential has become a subject of great studies (Naiman and Decamps, 1990).
In the United States, the goal of riparian ecosystems management should be to protect, restore, and compensate for previous degradation (Young K. A., 2000). Furthermore, understanding the causes of the riparian zones degradation will assist greatly in river restorations efforts. Riparian areas are critical habitat for countless plants and animals in t he arid west. There are numerous things that have the potential in contributing in riparian zone degradation. Among them, livestock, wildfire, as well as invasive or non-native species as well as aggressive urban development are the most physically predominant cause of riparian ecosystem degradation in the south western part of the United States. Up until recently in New Mexico, livestock grazing is the leading cause of riparian degradation. Impacts to vegetation, stream and river hydrology as well as geomorphology can separately or synergistically affect stream and river functioning and many wildlife species (Boone K.J.OSU.EDU). In New Mexico as well as countless areas like it, many land uses show an absence of respect for the value of healthy and vigorous riparian ecosystem and subsequently have resulted in the deterioration of not only riparian areas, but also the entire landscape. Generally speaking, land abuses that have degraded riparian zones include logging, water diversion for agricultural needs or municipal uses, mining roads, channelization, urbanization, industries as well as irrigation. In the south west, particularly, it is most likely that livestock grazing has been the most widespread cause of ecological degradation of stream ecosystems or riparian zones.
C. Objective of Wiki space
The goal of the wiki space is provide a “go to” place where various topic and articles on river restoration have been compiled by graduate students. This is a great place to start with when one would like to have a quick overview on riparian zones or systems in general.
2- Significance of Riparian Zones
A. Riparian Z structure - geomorphology, vegetation, habitat
The geomorphic template upon which the riparian forest develops is constantly undergoing change induced by the discharge regime (Brinson M.M., 1991). The drainage network from headwaters to the estuary represents a mosaic of sites that may be aggrading, degrading or may be maintaining a steady state (Naiman R.J. and Decamps H. 1999). Even sites in steady states where the downstream movement of deposited materials is balanced by the alluvial transport from upstream, the stream channels will continue to meander laterally and down-valley so that the physical features of the riparian zone continue to change (Dunne T. and Leopold L.B. 1979). In riparian floodplains, having a ridge-and-swale topography, vegetative patch types alternate between those on topographic lows adapted to long hydro-periods and those on topographic highs with species also found in mesic uplands (Mertes L. et al.,1995).
Most riparian zones are covered with a remarkable variety of woody vegetation from shrubs serving as refuges for small mammals to trees offering nesting and perching sites for birds. In addition, riparian forests act as refuges in adjacent areas and, in some cases, as corridors for migrations and dispersal (Brinson M.M et al., 1981).
B. Riparian Zone processes - sedimentation, hydrology, hydraulics, nutrients
Multifaceted exchanges among hydrology, geomorphology, solar radiation, temperature, as well as fire influence the structure, dynamics and composition of riparian zones/systems (Brinson M.M., 1991). This literature suggested that hydrology including its interactions with the local geology is the most important factor of the riparian ecosystems.
There are two particular aspects in fluvial geomorphology which help understand patterns and processes in riparian vegetation. These aspects include site-specific erosion and deposition, and lateral channel migration. Lateral channel migration may be slow (cm/yr) to fast (1km/yr), depending of the type of stream hydraulics, and this substantially influences the composition and demography of the vegetation communities (Brinson M.M., 1991)
Riparian vegetation modifies sediment transport either by physically entrapping materials, which appears to be most important in relatively low gradient environments, or by altering channel hydraulics. Accretion of sediment and organic matter by vegetation can be substantial especially during flood events. Sediment supply greatly depends upon land use, climate, and tectonic activity. In addition, rates of erosion and deposition ranges from a couple of millimeters to several meters per year (Naiman & Decamps, 1999).
Naiman and Decamps have concluded that alteration of channel hydraulics is accomplished either by roots or by large woody debris in the channel at low flows and by stems at high flows. All provide physical structure that slows water current, decreases the stream power as well as holds material in place. In addition, woody debris produced by the vegetation shapes channel morphology by redirecting flows of water and sediment, sorting sediments as wells as either retaining or moving materials(Hupp C.R. and Osterkamp W.R. 1995).
Organic matter from riparian vegetation is a source of nourishment for aquatic organisms (Hynes H.B.N., 1963). It has been found that as general trend, the proportion of coarse particulate organic matter decreases as the river increases in size. The storage of coarse particulate organic matter increases during the wet season in headwater channels where retention is high, with the result that these reaches have more organic matters than do downstream reaches. In addition to particulate organic matter, riparian zones contribute to substantial amounts of dissolved organic matter to river ecosystem. Living riparian vegetation is also source of nourishment for numerous terrestrial animals, from insects to mammals that can considerably alter the system function by their feeding activities. Outbreaks of defoliating insects or plants can alter riparian forest production and subsequently alter water yield, nutrient cycling, as well as stream water chemistry (Swank W.T. et al., 1981).
Land-water interface reduces nutrient movements to streams which led to understanding the role played by riparian zones in controlling nonpoint sources pollution by sediment and nutrients in agricultural watersheds (Jacobs T.C et al., 1985).
C. RZ services - habitat provisioning, stream bank stabilization, nutrient cycling, improved WQ (link to Lana and Meghan)
3- Degradation of Riparian Zones
A. Floodplain development
Riverine floodplains cover a small portion the terrestrial and aquatic landscape; nonetheless they support high levels of environmental heterogeneity and biological diversity (Naiman et al., 1993). Floodplains are also among the most altered ecosystems in the whole wide world, yet their biological diversity continues to deteriorate at a drastic rate (Ward et al., 1999). In addition, (Thoms M.C. 2003) study demonstrated that floodplain development has had diverse impacts on the potential supply of dissolve organic carbon on the floodplain. Large floods potentially supply more dissolved organic carbon available than small floods because they inundate more of the floodplain surface. Two critical factors influencing floodplain degradation are river regulation by water storage as well as diversion schemes (Dynesius and Nilsson, 1994).
By the mid-20th century, the development of heavily vegetated floodplains mainly composed of salt cedars, often within the active channel, force many of these rivers and streams to narrow (Webb et al. 2004). This pattern of floodplain development and channel narrowing is dramatically seen in many southwestern rivers of the United States in general, and in New Mexico in particular. Salt cedars (Tamarix) may have first established on bare channel margins, sandbars, and islands along the lower watershed, and vertical accretion as well as lateral expansion of these stabilized floodplains occurred over the next decades (Adam S. and Cooper D., 2006).
Urban developments are also one of the many setbacks of floodplain welfare. Due to the convenient topography and the esthetically pleasing environment, floodplains areas appeal socio-economic activities therefore attract developers. Subsequently, these activities on the floodplain areas makes the restoration projects costly and time stressed. One the most effective ways to reducing costs of floodplain development is to restrict development activities with the floodplain areas (Zhai J. 2000).
B. Hydrologic manipulations - dams, water diversions
C. River engineering
D. Invasive species
Although common in nature, biological invasions have been accelerated through human activities (Ledge D.M, 1993). Life-history characteristics of invaders control the various stages of establishment, stabilization as well as expansion. The richest communities also have the greatest proportion of invasive species, along the rivers and within specific sites, although several interactive processes appear to control establishment of these exotics in riparian zones (Decamps H. et al. 1995), many of them still survive and thrive.
Natural environmental features may slow the rate of invasion. In addition, seed predation combined with folivores is also likely to slow the rate of expansion because of the seeds of the species are dispersed by flotation (Naiman J. and Decamps, 1999).
Although invasive species expansion can reduce native plant species diversity, there is no clear evidence it does. On the other hand, invasive exotic woody plants in arid as well as semi-arid riparian habitats such New Mexico are expected to replace or inhibit much of the native flora , but clear data supporting or rejecting these expectations do not exist as of yet (Brock J.H, 1994).
4- Restoration approaches
a. Natural flow regime (brief intro and then link to Ryan M)
Flooding through the riparian system is critical for its survival as well as its ability to thrive. Floods create heterogeneity within the riparian zone and thereby create distinct regeneration niches that facilitate the coexistence of congeneric species. Also, periodic flood disturbances of various intensities are critical for maintaining the four dominant tree species of the lowland floodplains pod carp forest as well. At local scales, floods affect species diversity of herbaceous plants through physical heterogeneities created by the erosion and or deposition of litter and silt.
B. Invasive species control
A lot of efforts and have allocated in fighting these undesirable invasive species, especially here in New Mexico. Millions upon millions of dollars as well as millions of men hours have been invested in controlling these exotics plant.
Various methods are being utilized in controlling these invaters. For example, in the Middle Rio Grande and some other parts part of the region, goats and foreign beetles are being used to graze down the salt cedars…
C. Levee setbacks
Levees support riparian gallery forests that otherwise may flood frequently, however, the coarse deposits normally results in rapid drainage when water levels drop. Oxbow lakes are the most hydric of the riparian habitats, supporting species adapted to constant flooding and anaerobic soils (Naiman R.J. and Decamps H., 1999).
d. Bank de-stabilization (removal of control like rip-rap and jetty-jacks)
5-Examples of restoration projects
A. Rio Grande
B. Pecos River
C. San Joaquin
7- Conclusion:
8 – References
Tansley, A.G., 1911. Types of British Vegetation, Cambridge University Press, Cambridge.Waddington, J.M., Roulet, N., Hill, A.R., 1993. Runoff mechanisms in a forested groundwater discharge wetland. Journal of Hydrology 147, 37–60. Malanson, G.P., 1993. Riparian Landscapes, Cambridge Studies in Ecology, 296pp.
Burt T.P., Pinay G., Matheson F.E., Haycock N.E., Butturini A. et al. Water table fluctuations in the riparian zone: comparative results
from a pan-European experiment. Journal of Hydrology 265 (2002) 129–148
Boone K.J. Lifeblood of the west, Riparian Zones, Biodiversity, and Degradation by Livestock
KYLE A. YOUNG, Riparian Zone Management in the Pacific Northwest: Who’s Cutting What? DOI: 10.1007/s002670010076
Brinson MM. 1990. Riverine forests. In Forested Wetlands, ed. AE Lugo, MM Brinson, S Brown, 15:87-141. Amsterdam/New York: Elsevier
Robert J. Naiman and Henri Decamps, 1999. The ecology of interfaces: Riparian zones. Annu. Rev. Ecol. Syst. 1997. 28:621-58
Dunne T, Leopold LB, 1979, Water in Environmental Planning. San Francisco: Freeman
Mertes LAK et al., 1995. Spatial patterns of hydrology, geomorphology, and vegetation on the floodplain of the Amazon River in Brazil from a remote sensing perspective. Geomorphology 13:215-32
Hupp C.R. et al. 1995. Biogeomorphology, Terrestrial and Freshwater Systems. Amsterdam: El-sevier Sci.
Brinson M., Lugo A., and Brown S. 1981. Primary productivity, consumer activity, and decomposition in freshwater wetlands. Annu. Rev. Ecol. Syst. 12:123-61
Hynes HBN. 1963. Imported organic matter and secondary productivity in streams. Proc. 16th Int. Congr. Zool., Vol. 4, pp. 324-329
Jacobs T.C. and Gilliam JW. 1985. Riparian losses of nitrate from agricultural drainage waters. J. Environ. Qual. 14:472-78
Swank WT, Wade JB, Crossley DA, Todd RL. 1981. Insect defoliation enhances nitrate export from forest ecosystems. Oecologia 51:297-99
Lodge DM, 1993. Biological invasions: lessons for ecology. Trends Evol. Ecol. 8:133-37
Decamps H, Planty-Tabcchi AM, Tabacchi E, 1995. Changes in the hydrological regime and invasions by plant species along riparian systems of the Adour River, France. Regul. Riv. 11:23-33
Brock J.H, 1994. Tamarix spp. (salt cedar), an invasive exotic woody plant in arid and semi-arid riparian habitats of western USA. In Ecology and Management of Invasive Riverside Plants, ed. LC de Waal, LE Child, PM Wade, JH Brock, pp 27-44 . Chichester: Wiley
ADAM S. BIRKEN AND DAVID J. COOPER, 2006. PROCESSES OF TAMARIX INVASION AND FLOODPLAIN DEVELOPMENTALONG THE LOWER GREEN RIVER, UTAH. Ecological Applications, 16(3), 2006, pp. 110
Ward M., and Brock J. H., editors. Ecology and management of invasive riverside plants. John Wiley and Sons, Chichester, UK.
Dynesius M., and Nilsson C. 1994. Fragmentation and flow regulation of river systems in the northern third of the world. Science 266:753-762
Webb R., Belnap J., and Weisheit J. 2004. Cataract Canyon: a human and environmental history of the rivers in Canyonlands. University of Utah Press, Salt Lake City, Utah, USA.
Jinliang ZHAI, Wei DENG. 2000. FLOODING, FLOODPLAIN DEVELOPMENTAND MANAGEMENT IN CHINA. Ecosystem Service and Sustainable Watershed Management in North China International Conference, Beijing, P.R. China, August 23 - 25, 2000
Thoms M. C. 2003. Floodplain–river ecosystems: lateral connections and the implications of human interference. Geomorphology 56 (2003) 335-349