1) Define geomorphology. What is the role of geomorphology in structuring floodplain ecosystems?
Geomorphology is about hownatural or non-natural processes transform the shapeand characters of the landscape. Above all, endogenic factor includes properties of rocks and also soil; exogenic factor includes formation processes, such as weathering, transportation, and erosion. Specifically in a river system, active hydrological force plays a major part in geomorphologic processes. Hence, factors like tectonic (relief), lithology (soil), climate (hydrology), river history, and human are important geomorphologic forces in structuring a fluvial system. The geomorphology features also affect how vegetation establishes.
Tectonic force: Earthquake could also induce formation of a lake by land sink and river cutoff, i.e. Reelfoot Lake. The lake was formed during New Madrid earthquakes around 1811 in Tennessee, USA.
Lithology: Soil quality relates to particle structure and its stability. For example, mineral contains and soil texture relate to stability of weathering or erosion. Sizes of soil particle also control the sedimentation process. Small particles like clay could be transported further. Clay plug happens when flow transportation force is smaller than sedimentation; clay plug thus blocks meandering channels. Soil types affect vegetation establishment.
On the other hand, vegetation could reduce the erodibility of the land and increase sedimentation. For example, loess structure breaks down by water erosion or wind blow. Such erosion gets worse if vegetation is absent. This is also a prevalent problem in the upper Mississippi River Basin because most of the riverine areas were transformed into agricultural lands a hundred years ago, like what we saw in West Tennessee.
Climate: The geomorphologic change of a river comes from its geologic history as well as hydrological feature and sediment loads. A river could be abandoned by sedimentation and changed river course. Topographic change of a river system relates to hydrologic pattern. Overtopped flooding will induce further deposition of sediment away from river channel and thus forms ridge and swale.
River history: Mississippi River was with braided channels in the past but now become meandered ones. Because stream power increased with larger scouring force to the riverbed, flow focuses on a single channel.
Human: From European settlement to present, urbanization, agricultural lands have removed vegetation cover. River control systems like levees, channelization, and dams have increased discharge quantity, stream power.
Overall, geomorphologic variance in a floodplain influences the topography, hydroperiod, and edaphic quality. Those features are favored by different group of vegetation. Vegetation groups and hydrologic connectivity change influence the availability of food resources to wildlife. Also, the variability affects wildlife migration and niches.
2) Define and explain hydrologic connectivity as it pertains to floodplain ecosystems. Discuss temporal and spatial variability in connectivity and associated ecological processes. In what ways can hydrologic connectivity be disrupted? What effects can disruption have on floodplain ecosystems?
Hydrologic connectivity is about how water moves within a floodplain ecosystem. River connectivity changes with river stages and geomorphologic features. The change of river connectivity also affects ecological functions. For example, the height of the water level in growing season could define the chance of survival to plants.
For example, oxbows are cut off from river for a long time; higher river stage may also replenish nutrients to the river. Generally, oxbows are important habitats for fish. Ridge and swale are formed from point bar as stream migrates across the floodplain, the variance of topography and vicinity of water provides important habitat for birds, amphibians, and more animals. Turtles with different species, and sexes utilize the habitat with their own niches, i.e. Graptemys psudogeographica females and Trachemys scripta females and males mostly use in river while G. psudogeographica males prefer scours. Temporary changes of river stage affect the water levels. Plant species also have different tolerance to flooding. Baldcypress, water tupelo and water elm mostly occur in oxbows and water hickory, overcup oak, green ash, and red maple could be found in shallower area with less water flooding. As hydroperiod gets shorter and elevation gets higher, you will find out more Black gum, white oak, cherrybark oak, and water oak.
Hydrological connectivity can be disrupted by human utilization, climate change, and channelization and also river structure. If the rivers are channelized, stream power could be enhanced within narrower, shorter water path and essentially scouring down the riverbed. Consequently, nick point shifts upland and thus lower riverbed of upstream rivers. And again the level of groundwater in the upper stream basin will be lowered adjusting to the lowered riverbed. Upper stream wetlands thus degrade with few water source.
1) You are in charge of stream restoration in western Tennessee for Tennessee Department of Environment and Conservation, and must design a comprehensive plan to address restoration issues. Please outline and briefly explain your overall goals and objectives. Also, please compare and contrast the restoration methods that we observed and discussed in West Tennessee including re-creating meandering streams (and their location in the watershed), purposely creating valley plugs in tributaries, and developing drop structures on streams.
My priority is to set up focal areas. In Tennessee, the agricultural lands are inducing land erosion and increase channelization of the rivers. First, I will find areas with higher ecological instability, such as increased hydroperiod, stream power, and lose river connectivity and higher biodiversity loss as my target ecosystem restoration areas. But I understand that we will definitely be facing a lot of conflicts. So, secondly I only ask for 20% improvement in the health of our stream, forest, and wildlife.
The only thing to get rid of conflicts and get things going is to purchase target lands and also search cooperation with neighbor farmers. We will try to bribe them in getting a wetland mitigation, EPA assistance on improving water quality, or agricultural improvement program.
As we saw how Jody did in Arkansas, we could apply similar method in producing such cooperation scheme. We will restore hydroperiod pattern of a Green tree reservoir with river water braided/ meandered amid the forest in winter. In spring, agricultural landowners could work on their desired crops. Plants are shown to have larger growth with abundant water and thus they provide enough food sources to fauna. Crop will be cut in the fall, where prairie land becomes inundated by river water. Inundation helps wildlife reproduction. Frequent inundation of soils could enhance fertilization for next spring. Meanwhile, forests remain dry in the growing season with more chances of seedling survival.
Here is my procedure,
Step1. Choose target area of restoration
èIdentifying the area with most rainfall.
èIdentifying areas with most stream power
èIdentifying areas with the worst channelization occurs
èIdentifying areas with diverse ecosystem
èThen yes, purchase them all or find ways to cooperate with landowners
Step 2. Implementing measures by severity
à Worst disturbed area such as valley plug, gully erosion, no generation of plants should be implement drop structures and bank stabilization methods in slowing the water velocity, stream power, and vegetation dying. (Case studies are applied from West Tennessee)
à Moderate problems on forests degradation with abandoned stream that lost connectivity from river or prolonged flooding problem.
à Restoring vegetation groups according to the Potential Natural Vegetation. In supplementary, we also induce native understory grass and shrubs. Because they could establish quickly in floodplain area, they are able to provide vegetation mat for woody trees, i.e. Swamp loosestrife (Dacodon verticillatus) in the Reelfoot Lake provides a living mat for the basement of baldcypress trees.
Step 3. Active responses to hydroperiod
à Increase the quantity of water absorption in the upper stream.
à Don’t manipulate the timing the flooding during growing season and be careful about the water level. Because over manipulate will only decrease the original function of the ecosystem.
Step 4. Maintenance and monitoring
à Removal of aggressive invasive species: target species are water hyacinth or similar aquatic species. Because those species grow rapidly and seriously block the living space of the other native plants.
2) Explain the Potential Vegetation Community concept by Klimas et al. What were the major steps/data layers needed? Give examples where this approach to classifying and managing floodplains would work or not work in other floodplain ecosystems and explain why or why not.
The PNV concept is to classify vegetation groups and match their natural occurrence with abiotic features. The reason is very straightforward. Plants follow abiotic features because every species could have their niches and living requirements like limitations of nutrients, water, or light. In this model, they use three factors, hydrology, geomorphology, and soil; and their target is the Mississippi floodplain.
Steps
First, overall field sampling and classification. Then forest dominance type is divided into groups according to their geomorphic and hydrologic settings. Second, combine hydrology, geomorphology, and soils from the field. Seek out unique combinations of the three variables for which little or no vegetation sample data had been collected. Primary inputs to the PNV model were geomorphology, soils, and hydrology (flood frequency). The potential group will be mapped in the GIS map. The PNV will be examined over again with HGM classification protocols in the field.
PNV concept may not work on other ecosystems. In yellow river of China, the major problems have been wind and water erosion, pollution, and urbanization. Hence, extra criteria should be taken into account.
