Plan for Masters of Forestry Project submitted 2002


A Characterization of Vegetation and Soils along Restored Streams
in the North Carolina Piedmont

Melissa Ruiz


Introduction

Agricultural expansion and urban development have caused damage to waterways due to erosion, sedimentation, channelization, and damming. Restoration has become a primary method in man's attempt to protect nature from human destruction. Through the process of restoration, a new stream channel is constructed or the existing one is rehabilitated, the banks are stabilized, and vegetation is planted. It is an attempt to restore waterways by recreating a functioning ecosystem, not just an element of an ecosystem. Baseline data is necessary to track the progress of these streams over time. This includes riparian vegetation, which is a vital part of the restored community. It is the transitional zone that links terrestrial and aquatic components (Baatrup-Pedersen et al. 1999).

Objectives


The principle purpose of this study is to characterize plants and soils in the riparian zones of restored streams in the Piedmont area. This assessment can be a useful predictor of stream system development and success. Stream restoration is a relatively new field therefore it is not likely to find projects more than 5 years old. As a result, stream restorations in this study range in age from 1 to 3 years old. Planting vegetation in the riparian zone is a requirement of most restorations. This includes native tree species that are components of the desired future plant community. Other components of the community can be established through natural recruitment. One objective is to describe the vegetation in the riparian zone in order to establish baseline data for future observations and monitoring. The data will also be used to determine if exotic species are invading the riparian zones, to what degree, and how this will affect the establishment of the desired community.

A second objective is to characterize the soils in the riparian zones. Soil stores and recycles nutrients based on its properties, microclimate and microorganisms. Riparian vegetation is largely influenced by soil and hydrology. The chemical and physical properties of the soil are one of the many causes of variation in plant community composition. Soils change over time therefore it is important to record its properties after restoration.

Literature Review

Due to the fact that streams and other waterways provide many things for humans, including nourishment, energy, and transportation; they tend to be misused or overused leading to ecosystem damage (Gore 1985). They are altered by damming, channelization, culverts, and lining with concrete. Pollution, sedimentation and an increase in water use have all led to degradation of waterways (NRC 1992). Siltation impaired 40 percent of surveyed stream miles and bank erosion almost 23 percent (NRC 1992). Restoration has become necessary in a world where humans are continuously manipulating nature and using its resources. If we want to continue life on this planet, we must work to repair the Earth's ecosystems (Hobbs & Harris 2001). It is necessary to start restoring before substantial losses of biodiversity have occurred (Dobson et al. 1997). Stream restoration has enormous potential (Brookes & Shields 1996). Streams and restored streams serve as wildlife corridors, wetland multipliers of ecosystem integrity, scenic, and recreational resources (Ferguson 1991). They also recycle nutrients, purify water, and recharge groundwater (NRC 1992).
But managing and restoring streams for these purposes is a relatively new practice. In the past streams were managed to move stormwater downstream and protect property in urban areas (Brown 2000) or to create farmland. Restorations were isolated to programs that improved trout streams for recreation (Brown 2000) or for water quality, which became an issue in the 1950's (Brookes & Shields 1996). It wasn't until the mid 70's that geomorphologists began restoration and rehabilitation of small rivers and streams (Brookes & Shields 1996). Today, the public supports an increase in environmental protection through many programs and some believe restoration should be the centerpiece of these programs (NRC 1992).

The idea of restoration has become accepted and it is being carried out around the United States as part of an effort to improve water quality and aquatic ecology (NRC 1992). There are many definitions and goals of restoration. Restoration should be holistic, with attention given to geomorphic, hydrological, biological, aesthetic, and water quality aspects of the system (Osborne et al. 1993). It is not the manipulation of isolated elements; rather it is a holistic process (NRC 1992). A good restoration attempts to recreate a functioning ecosystem of a desired type, not just an element of an ecosystem. In order to carry out a successful restoration, baseline data should be collected and goals should be established. From there a project plan can be produced that includes critical aspects such as a topographic and hydraulic design, a soil design, a revegetation design and habitat features (Jensen & Platts 1990).

Many times structures are installed in streams while allowing the continuation of abusive grazing, logging or other land use practices (Beschta 1995). The most important step in the restoration of waterways is to stop those activities that are causing degradation or preventing recovery (Kauffman et al. 1997). Once degradation has ceased, more active manipulations of the stream can proceed in hopes to restore function and structure.

Most stream restorations are carried out to improve water quality, and elements such as riparian vegetation receive less attention (Osborne et al. 1993). Restoration focuses primarily on stabilization of stream banks to lessen sediment loads, and establishment of a more natural channel. There is inadequate consideration of the impacts of this restoration process, particularly construction damage to the surrounding area, to reach this goal. Excavation and channel construction result in soils that have been disrupted and mixed up, often leaving compacted, nutrient poor subsoils exposed. After construction there is often little or no attempt to ensure these soils will support the desired plant community.

Riparian vegetation is a vital part of the restored community. The riparian zone is recognized as an important component of stream restoration (Federal Interagency Stream Restoration Working Group 1998). A good restoration of a stream ensures sedimentation and the retention of deposited sediments; this is enhanced by the presence of vegetation (Thornton et al. 1997). It is valuable for fish and wildlife habitat, flood storage and desynchronization, nutrient cycling and water quality, recreation, and heritage values (Jensen & Platts 1990). The riparian zone links the stream environment to the terrestrial catchment allowing it to influence both (Osborne & Kovacic 1993). The zones can moderate temperature, reduce sediment input, stabilize stream banks, and serve as a source of organic matter (Osborne & Kovacic 1993). The zones act as a storage unit for carbon, nitrogen, phosphorous, and others, which are eventually passed along to the organic soil layer. They reduce nutrient leakage from the catchment towards the stream (Osborne et al 1993 and Brookes et al. 1996). The vegetation provides shade, cover, food, and organic debris including downed trees which are all necessary for wildlife habitat (Brookes et al. 1996 and Ferguson 1991).

Interactions among three fundamental ecosystem features - soils/geomorphology, hydrology, and biota, - are what give the riparian zone its value and character. For example, plant community composition is influenced by soil characteristics and hydrology (Kauffman et al. 1997). The roots of plants need oxygen, moisture, and nutrients to survive (Helliwell 1995). Chemical and physical properties of the soil affect the quantity and availability of these items to plants thereby helping to determine the distribution and characteristics of the plant communities.

Heavy equipment is used to grade the subsoil during restoration. This can result in a solid layer of material at the upper boundary to the subsoil (Gore 1995). The plants will not grow if the soil is highly compacted, insufficiently aerated or dry (Helliwell 1995). The soil must have a sufficient water capacity and allow for root penetration (Gore et al.1995). Plant roots need oxygen for respiration which produces the necessary energy to take up nutrients. Compaction decreases the oxygen concentration available to plants by reducing porosity (Wolkowski 1990).

After restoration, the composition and structure of the soil and vegetation will change over time. Restoration is similar to other types of disturbance. After disturbance the ecosystem goes through various phases of development. More nutrients are immobilized and not available to plants in mineral forms as succession advances (Biondini et al. 1985).

Methods


Study Areas

The study areas are a subset of restored streams that are monitored by the North Carolina Division of Water Quality. The streams are located in the piedmont of North Carolina and include rural and urban streams.

Data collection and Analysis

At each site the research will be conducted in the riparian zones of the stream corridors. Stream corridor is the term used to refer to the stream channel and the plant communities on either side (the riparian zone). A preliminary survey will help determine the necessary size and number of sample plots. Once this is established, presence/absence data will be collected for all vegetation types (trees, saplings, seedlings, shrubs, grasses, herbs and forbs). Presence is the occurrence of a rooted species, meaning at least one stem emerges from the soil in the plot (Peet et al. 1998). Percent cover will be visually estimated for each species using the Braun Blanquet system of cover classes (Mueller-Dombios & Ellenburg 1974). In this study, cover is defined as the percent of the plot beneath the vertical projection of the canopy of a species (Barbour et al. 1999).

Vegetation will be identified to the species level using the Manual of Vascular Flora of the Carolinas. Identification will take place during June, July and August of 2002. A list will be made of the species located at each site. Exotic species will be identified and a percent cover of the combined exotics will be calculated for each plot.

A preliminary study of soil profiles found in the study areas will be carried out. Then the number of samples as well as depth of each sample will be determined.

Plot locations will be recorded using a GPS in order to facilitate future monitoring.

Benefits

These questions are important for the future of restoration. Millions of dollars are spent to perform stream restorations. The goal is a good restoration - one with function and structure. It is necessary to evaluate the effects of construction on the establishment of riparian zone vegetation, as it is a vital part of this goal.

Schedule

The study will commence as of May 15, 2002, or as soon as the list of sites as been compiled. The survey will end by August 31, 2002 and soil samples will be analyzed by October 31, 2002. A final report will be submitted by March 31, 2002.