Introduction

The objectives of forest practice regulations for riparian zones are:

• Provide high levels of protection to stream resources especially anadromous fisheries
• Insofar as possible, allow the continuous growing and harvesting of trees.

Two main criteria must be addressed by the regulations:

• The width of the streamside area that is to be protected
• The amount and type of vegetation to be retained in the protected area.

A comparison of the riparian protection rules of California and Oregon suggests several changes in the California regulations to better address the objectives. First, the regulations can be modified to increase the width of the riparian management area along larger streams. Secondly, the requirements to retain a certain percentage of the existing canopy can be modified to retain a certain basal area of conifers. In addition, the requirements for determining the width of riparian management zones can be modified to include additional criteria including the inner gorge, the 50 year flood plain, and the extent of riparian vegetation.

Many benefits are provided to stream ecosystems by the riparian area. Riparian trees shade the stream and occasionally fall into the stream to become large woody debris. Large woody debris affects channel morphology in many ways, including the creation of cover, velocity shelter, pools, and beds of spawning gravel. The root masses of trees near the stream bank create pools, undercut banks, and backwater areas and also help maintain bank stability. The riparian area provides the stream ecosystem with nutrients from insects, leaves, needles, and branches. Relative humidity is increased under the riparian canopy which is important for certain species. In cold climates, the riparian vegetation can reduce or prevent ice formation. The riparian vegetation also reduces the velocity of floodwaters, effectively storing floodwater and reducing the impact of floods. As the velocity of floodwater is reduced, sediment is deposited on the floodplain. This removes large amounts of sediment from the active stream channel. By affecting water velocity and creating roughness in the channel, riparian vegetation can also play a complex role in channel evolution.

Advantages of the Oregon Riparian Regulations for Anadromous Salmonid Protection

Lorensen et al. (1994) describe several ways in which Oregon’s approach to riparian management provides better protection of anadromous salmonid stocks. One advantage of the Oregon regulations, compared to rules in California, is that riparian management areas are scaled to the size of the streams. For example, larger streams are required to have wider buffer strips. By tailoring riparian management to the size of the stream, large woody debris can be produced where it will create the most stream habitat diversity and benefits to fisheries.

Another advantage of the Oregon regulations is the use of basal area to define the retention requirement for conifers. The regulations require retention of a certain amount of conifer basal area following harvest. Because the landowner can harvest all timber in excess of the basal area retention requirement, a strong incentive is created for fully restocking conifers in streamside areas. This eventually makes more large woody debris available to the stream.

Another advantage of the Oregon regulations is the improved logistics of conifer regeneration in the riparian management zone. The regulations allow the landowner to retain the basal area as large or small trees, in clumps or evenly spaced. This allows the creation of openings in the canopy to increase conifer regeneration. Furthermore because these regulations do not specify the number of trees to be retained, there is no bias toward retaining small trees. The result is the regeneration and retention of large trees in the riparian area. Over time, a greater number of conifers of a larger size will be produced. A portion of these large trees will fall into the stream and create habitat diversity for anadromous fisheries.

In cases where stream restoration is needed, the Oregon regulations provide incentives for landowners to put wood in streams. These incentives include allowing more timber harvest, impacting less land base, and reducing constraints on other management activities or administrative requirements, or providing additional management flexibility. The large woody debris that is placed in the streams will immediately provide cover and habitat for anadromous fish.

In the Oregon regulations, the riparian management zone in areas of steep exposed rock, soil, or talus slope is measured as horizontal distance rather than slope distance. This results in a wider buffer in these potentially unstable areas. The benefits to anadromous fisheries include reduced erosion of the steep areas, increased possibility of woody debris being supplied from upslope, and other benefits of the riparian area such as nutrients from leaves.

Proposed Changes in California Forest Practices for Riparian Management

1) Increased width of riparian management zones on larger streams

The first recommended change in the California riparian regulations is to increase the width of buffers required on medium and large streams. The stream classification system in the California regulations does not differentiate between large and small streams. In contrast, the Oregon regulations stratify streams based on average annual flow, which allows the larger streams to be targeted for retention of more streamside vegetation.

As streams increase in size, their capacity to transport woody debris also increases. The higher flows that occur on large streams can transport woody debris of a larger size. The larger streams usually carry away most of the small woody debris unless larger pieces are available to provide stability. In large streams, large woody debris such as conifer logs with root wads are needed to initiate the creation of debris jams. Therefore larger pieces of woody debris assume greater importance as stream size increases.

Not only are larger streams capable of carrying larger pieces of wood, they also have more frequent high flows and move woody debris downstream at a higher rate. Due to more rapid removal of wood from large streams, more rapid recruitment of large woody debris is necessary to maintain high habitat diversity in these streams. More rapid recruitment of large woody debris is only possible if the riparian area is heavily forested with large trees. By increasing the width of the riparian management zone, the rate of wood recruitment is increased because more trees are available to fall into the stream.

The California regulations provide wider stream protection zones in areas having steep slope. Because streams in steep areas are usually small and high in the watershed, this regulation effectively creates greater protection for small streams. Because small streams have less water power, they are less capable of transporting woody debris. Therefore, in small streams, smaller pieces of woody debris can provide the stable structures needed to create habitat diversity. While there are many important reasons to provide increased buffer widths on small streams on steep slopes, the biological need for large woody debris is greater on large streams than small streams.

This proposed change will improve conditions for anadromous salmonids by increasing the amount of woody debris recruited into medium- and large-sized streams, which will create more cover, pools, and other forms of habitat diversity. This will increase the "fish-friendliness" of these streams and will result in improved connectivity between various habitats. Connectivity is extremely important to allow expression of variation in life history patterns of anadromous fish (Lichatowich et al. 1995).

2) Modified vegetation retention requirements

Another recommended revision in the California riparian management regulations is to measure the required vegetation retention by basal area rather than percent canopy. The existing California riparian regulations specify the amount of canopy to be retained by type and by percent. The types of canopy are the understory canopy, the overstory canopy, and existing overstory conifer canopy. For streams that have aquatic species, the regulations also have a basal area requirement: "the retention of two living conifers per acre at least 16 inches diameter breast height and 50 feet tall within 50 feet" of the stream.

In the Oregon regulations, the vegetation retention requirements are based almost entirely on the minimum amount of conifer basal area to be retained. Except in the 20 foot wide no-harvest zone along the stream, conifer basal area in excess of the required minimum may be harvested. As previously noted, this increases incentives for landowners to keep the area fully stocked with conifers, and increases the number of large conifers recruited into the stream. In contrast the California regulations allow the operator to take half the canopy in the riparian area. No matter how much they grow, they can still only take half the canopy. The economic incentive to maintain full stocking is small compared to the incentives provided by the Oregon regulations.

Besides providing incentives for stocking conifers in the riparian area, the Oregon regulations also allow management flexibility and improve opportunities for conifer regeneration. Because the Oregon regulations target retention of conifer basal area rather than shade, they allow various management strategies that facilitate regeneration of conifers. The landowners are permitted to create occasional openings in the canopy which are necessary to regenerate valuable Douglas fir trees. In contrast, the California requirements target canopy retention. Shady conditions are created which are good for maintaining low stream temperatures but make conifer regeneration very difficult. By modifying the California regulations to target conifer basal area rather than percent canopy, there will be increased production of conifers in the riparian zone, increased rates of large woody debris input into the stream, and increased habitat diversity to benefit the fish. To ensure adequate shading on the stream, the revised vegetation retention requirements for California should include a 20 foot wide no-harvest zone along the stream as provided for in the Oregon regulations.

The canopy retention requirements in the California regulations not only make conifer regeneration difficult, they also do not result in retention of large conifers in the riparian zone. By retaining hardwoods, the forester can meet the requirement to retain 50% of the overstory and understory. The requirement to retain 25% of the existing conifer canopy can be met with small diameter trees. These hardwoods and small conifers are much less capable of initiating the creation of stream structures especially on medium and large streams. The California requirements for retaining two conifers 16 inches diameter breast height and 50 feet tall per acre amounts to less than 1 square foot per 1000 square feet and is also less than 1% of the conifer basal area retained under the Oregon regulations.

By modeling the California riparian vegetation retention requirements after the Oregon regulations, we can create stronger incentives to grow large conifers in the riparian zone, which will immensely benefit fish over the long-term.

3) Additional criteria for defining the riparian management zone

Similar to methods described in the USFS Record of Decision (1994), it is recommended that the California riparian regulations employ multiple criteria in determining the width of riparian management zones. The riparian management zone will be defined as the largest of the following:

• the top of the inner gorge
• the outer edges of the 50 year floodplain
• the outer edges of riparian vegetation
• the width based on stream class, average annual stream flow, and slope as shown in Chart 1.

Advantages of the California Approach to Riparian Management

In many cases, the California regulations provide wider protective buffers on streams than the Oregon regulations, especially on steep slopes. For example, on small fish-bearing streams on slopes over 50%, the California regulations require a 150 foot riparian management area while the Oregon regulations require only a 50 foot riparian management area.

The existing California regulations require that diversity in the riparian zone must be "similar to that found before harvest." The Oregon regulations encourage diversity by allowing large hardwood trees (except alder) to be included in the basal area targets. Although the California diversity requirement is vague, it is not optional like the Oregon regulation for keeping large hardwoods. Monitoring is needed to determine the relative effectiveness of these requirements.

Clearly benefits to anadromous salmonids are possible through revision of California’s Forest Practice Regulations for riparian management. A relatively non-controversial recommendation is redefining the vegetation retention requirements in terms of minimum conifer basal area rather than canopy percent. Anadromous salmonids would benefit from the resulting increase in large woody debris. Timber operators would possibly benefit (or break even) due to increased opportunities to regenerate and harvest conifers.

Conclusion

The recommendations for increased buffer widths on larger streams will further restrict timber harvesting and are likely to generate significant opposition. The potential long-term benefits to anadromous salmonids are also expected to be significant. It is hoped that wider buffers on larger streams will gradually improve stream ecosystem connectivity and allow expression of alternative life history patterns of anadromous salmonids. The additional criteria for buffer widths is expected to provide many widespread benefits, including reduced effects of floods, reduced sediment loads, and maintenance of stability in the inner gorge. All the recommended changes are expected to increase habitat diversity by recruiting more large woody debris into the stream. Over time, benefits to anadromous fisheries are expected to be considerable.

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