2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
Methodology
Soils monitoring was conducted on September 30 and October 2, 2008 in conjunction with the
vegetation monitoring work. Soil samples were collected along each vegetation transect, at three
locations distributed along the elevation range of each transect. The samples were generally collected
at each end of the transect and at a mid-point along the transect that represented a median elevation and
were assigned a label of A, B, and C (Figure 1-2).
At each sampling point soil, small holes were dug to a depth of 5
and 15 centimeters to assess the pore water quality. Most holes
filled with pore water after being dug, which was measured for
salinity with a hand-held refractometer to the nearest part per
thousand (ppt) and for pH with a Hanna HI 9125 portable pH
meter inserted into the pore water. If the holes formed no
pooled water, interstitial soil water was filtered from the soil
using a syringe containing two No. 1 filter papers. Filtered
water was placed onto a refractometer and the salinity recorded.
If the sampling point along the transect occurred over open
water, the open water salinity and pH was measured instead.
Soil and pore water collection.
At the same locations, sediment samples were collected from the surface (upper 5 cm) and transported
to the laboratory for analysis of grain size distribution (ASTM D4464) and total organic carbon (TOC)
(EPA 9060A).
Results
The results of the soil assessment are presented in Table 1-3. In many cases the soil was so dry
(generally in sandy areas) it was not possible to extract water from the sample to make the field
measurement of pH or salinity. In some cases salinity could be measured while pH could not, because
only a few drops of water are needed to determine salinity, whereas the pH meter needs pooled water
to submerge the probe in. The table presents the mean grain size description for each sample; the full
grain size analyses for each sample are presented in Table 1-4.
TOC was highest in silty, vegetated areas, particularly in the Muted Pocket Marsh, which has a more
mature, dense, and diverse salt marsh than the other areas. Pore water pH in vegetated marsh was
generally in the 6 to 7 range, while the pH of areas inundated with tidal waters was around 8.3
generally. The only low pH (5.3) was measured in a basin of pooled water at CMTB 3A that had a
high iron content (the water and sediment were rusty red). Pore water salinity was highly variable
depending on its degree of exposure to tidal waters, elevation, and surrounding sediment grain size.
Discussion
The Monitoring Plan discusses that a knowledge of soil conditions will help determine which factors
might be controlling plant community diversity and productivity, and which types of plant
communities are likely to develop in the future. Although the plant diversity was documented in the
transect monitoring described above, it was generally very low or absent (in areas that had yet to be
colonized by vegetation). It is therefore difficult to seek correlations between marsh diversity and soil
characteristics at this early stage of marsh development. The present diversity of the marsh is likely
related to the length of time the marsh has been isolated from tidal influence and the degree to which
opportunitistic introduction of new marsh species has occurred.
Merkel & Associates, Inc. 34