Geoscience Reference
In-Depth Information
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Figure 5.4
marsh
representing the aggregate of (A) all profiles collected every 3 m along the 30-m transects, (B)
only profiles associated with undisturbed canopy locations, (C) only profiles associated with partial
canopy gaps, and (D) only profiles associated with severely lodged canopy locations.
Light attenuation profiles ([
●
] 9 and [
] 10 September) associated with a
Panicum hemitomon
5.3.2
Atypical Canopy Structures
Examples of disturbed or logged conditions at one or more locations within a site were found
in all marsh types. Relative to the number of occurrences, however, Juncus R. marshes contained
the fewest of these and Panicum H. and Spartina P. the most. Juncus R. canopies were most often
affected by wrack deposits or the subsequent marsh dieback or by fire and the subsequent recovery.
Animal herbivory and fire often affected Panicum H. marshes, but water with higher salinity
deposited by a storm surge seemed to have a lingering impact evident in the poststorm collections.
In the 2 years of data collections, a major storm and a fire affected Spartina A. sites. To a lesser
extent, Spartina P. sites were affected by storms and fire. The typical hummocky nature of this
marsh limited the usefulness of the logged indicator.
The first example contains light attenuation curves generated from two occupations 1 day apart
of a Panicum H. marsh site that was severely affected by animal activity following the occupation
(Figures 5.4A and B). Other than the magnitude of variance depicted by the error bars, little evidence
was present in the affected curves (Figures 5.4C and D) indicating the widespread abnormal canopy
structure. In fact, neglecting that only 1 day elapsed between collections, aggregating all profile
locations results in fairly reasonable profiles (Figure 5.4A). Excluding all affected profiles left few
observations in the undisturbed sample set; however, the aggregate of these remaining profiles
showed a more consistent depiction of canopy structure of little or no change in canopy structure
(Figure 5.4B).
A second example shows curves depicting site occupations in a lightly affected Panicum H.
marsh chronologically from October (before full senescence) to February (after senescence and
removal of most dead material), September (substantially before the initiation of senescence), and
December (after full senescence but before total dead material removal). Although differences
between the undisturbed (Figure 5.5B) and aggregated (Figure 5.5A) sequences were not dramatic
and only two of the occupations contained severely logged locations, inclusion of locations with
partial gap (Figures 5C and D) reduces the clarity of the trend consistent with expected seasonal
