Design Approach - Project Planning and Management for Ecological Restoration - page 72

Developing your own reference database has several advantages. By knowing what your goals
are, you can collect the data directly related to those goals. Use prior available data to your advan-
tage, if it exists, but be selective and only use that which is relevant for your purposes. This elimi-
nates approximating or interpreting the data of others. The database forms a strong foundation for
developing a specific design. However, there are limitations to using reference databases. These
limitations involve the elements of time and location.
If your data are collected from a vegetation community with a long life, then you must make
sure that the various environmental factors affecting your site are similar to the reference site.
For riparian areas, this may not be straightforward, as the dam building programs during the past
century have modified the hydrology of numerous rivers and streams (box 5-1). Thus, the riparian
vegetation growing on a site may have been established under a different set of hydrologic condi-
tions than those conditions that presently affect your project site.
Box 5-1. Lesson Learned: Choose Your Reference Model Carefully
Restoration project planners used a nearby mature floodplain forest as a reference
model for the design of a riparian habitat mitigation project. The planners failed
to recognize that the surface and groundwater hydrology of the reference site had
changed considerably since the inception of this riparian forest as a result of dam
installation, groundwater withdrawal, land development, and water management ac-
tivities in the watershed. During the permitting process, success criteria were tied to
achieving a trajectory of vegetation growth that would lead toward the characteristics
of the reference site. Whether it will be possible to replicate the reference site in the
long run is questionable due to the changed conditions in the watershed hydrology.
Only time will tell.
The project designers learned that it is important to avoid choosing a relict stand of
vegetation as a reference site. They also learned that it is better to design a native plant
revegetation project based on a hypothetical model that takes into account current
watershed conditions.
Another example addresses weather: a series of wetter-than-normal years can influence the spe-
cies germination and pattern where in normal years the species would be a minor element in the
landscape. This situation is difficult to assess if you look at only one location over a short time. A
technique to handle this potential bias is to study several sites in the vicinity (Bonham 1989). When
working in a stream or creek where the natural hydrologic cycle or intensity has been altered, you
can expect that the vegetation being studied was established under a very different hydrologic
regime, one that may not occur today, so adjustments will need to be made.
The presence of unusual vegetation communities or species may prompt an investigation to
understand the circumstances that account for their presence. A period of unusual rainfall or
drought might produce site conditions that enable establishment. After a short time, the condi-