Addendum J Methods for Sampling Riparian Habitat and Specifications for Plant Material Quality

Addendum (J): Methods for Sampling Riparian Habitat and Specifications for Plant Material Quality

This Addendum contains the procedures and minimum specifications for determining and configuring sample areas and techniques for both plot sampling and transect sampling to be conducted in conjunction with preparation of a Mitigation Restoration Plan as required by Section 27.10.G.

a. Determine the sample areas within which plots or transects will be established in accordance with Reference Site requirements. The following qualities shall be included in the sample area:

b. Sample areas for significant vegetation stands should include stands of mature and healthy vegetation that meet the minimum cover or density definitions in the ESL for those resources being impacted.

c. Sample areas’ area shall be large enough to include all species belonging to the plant community.

d. The habitat should be relatively uniform throughout a single sample area. Each habitat type shall be sampled separately.

i. Plots or transects shall be distributed throughout the sample area in a manner to capture all of the variability within that sample area. Plots or transects can be either located randomly within a sample area or according to an orderly sampling scheme (e.g., on a grid, at regular intervals, etc.)—as long as the result is that the sample area is accurately described by the plot number and arrangement.

ii. The sampling locations must be approved as part of the Mitigation Restoration Plan review process, and must be representative of the area being sampled.

a. Plot sampling, or quadrant sampling, can be used to describe a variety of plant community characteristics of an area that is too large for a complete vegetation inventory to be feasible.

b. The parameters to be addressed include: diversity (species present), cover, and density (number of species in a given area).

c. The number of plots or transects conducted within each sample area should be sufficient to characterize the range of vegetation conditions within it.

i. Plot size and shape should fit the nature of the vegetation community to be sampled. Circular plots are generally recommended with these field mapping standards, as they are more efficient to accurately establish in the field.

ii. Plot size should be large enough to include a significant number of individual plants, representing all dominant species, but small enough that plants can be counted without duplication or omission of individuals.

iii. Suggested plot sizes that are typically appropriate for vegetation in the context of riparian habitat are listed below. Site characteristics may necessitate using a different plot size or shape (i.e., if the riparian vegetation entity is not wide enough). Plot shape and size should be consistent throughout.

a) Circular plots (preferred): 10-meter radius (314 m² or 3,380 ft²)

b) Square plots: 15–20 meters per side (225 m²–400 m² or 2,422 ft²– 4,306 ft²)

c) Rectangular plots: 15 meters x 20 meters (300 m² or 3,229 ft²)

Transects may be conducted according to the point intercept and belt transect methods. The method is based on a 50-meter point transect centered on a 2×50-meter plot (i.e., the belt transect). Using this method, vegetation is sampled by points at 0.5-meter intervals along the 50-meter transect to determine cover. The surveyor will note the species encountered at each interval. In addition, individuals of each perennial species rooted within the 2×50-meter plot will be counted to determine density and diversity. All annuals present in the 2×50-meter plot will also be noted.

a. Plant materials may consist of salvaged plants or cuttings as well as container plants grown in traditional or tall pots from seed collected locally specifically for the project. Container plants will be grown at a nursery that specializes in producing high-quality native plant species for habitat restoration projects.

b. Native soil shall be used in the plant containers if possible. If more native soil is needed than is available to fill plant containers, each container shall receive some native soil mixed with an appropriate commercial nursery soil mix.

c. Container plants must be grown outdoors and in full sunlight. Prior to container plants being delivered to the project site, they shall be hardened off from water, so they may be able to sustain themselves under potential drought conditions once planted.

d. Deep-planting techniques for woody species are permitted in order to achieve maximum survival with minimal irrigation. This may include deep-planting of dormant pole cuttings as well as the use of container stock grown in tall pots.

All plant materials shall be inspected by Town staff prior to installation to ensure they are healthy, disease free, and of proper species, quantities, and sizes.