SITE DESCRIPTION
Area: 21.9 ha
Slope: 15.4°
Aspect: S24°E
Elevation: 488-762 m
Gage type: V-notch weir, San Dimas flume
Initial year: 1962
The USDA Forest Service installed a V-notch weir and San Dimas flume
in Watershed 5, and has measured streamflow since January 1, 1962.
Prior to treatment, the watershed was surveyed into 360 25 x 25
meter plots to be used for research (7/29/1982; G. Rowe, B. Simpson,
and L. Stuart, Surveyors). These plots were divided into vegetation
zones based on the trees present before the whole-tree harvest in
1983. This dataset contains a map of plots and vegetation zones.
WHOLE-TREE HARVEST EXPERMIMENT
A commercial whole-tree harvest was carried out on W5, a management
practice that is regaining interest due to rising demand for
biofuels. Compared to conventional stem-only harvests, whole-tree
harvesting involves the removal of most of the above-ground biomass
(boles and branches), raising concerns about nutrient removals and
impacts on site productivity. In this application, all trees greater
than 5 cm d.b.h. were cut with chain-saws and a track-mounted feller
buncher equipped with hydraulic shears. Trees were harvested and
removed from the watershed between October 1983 and January 1984, at
which time there was a machine accident, leaving the upper one-third
of the watershed uncut. Trees from most of the upper portion of the
watershed were removed during the following summer. Felled trees in
one small area (~12% of the watershed) were not removed until 1985,
and about 3% of the watershed was inaccessible and remained uncut.
In this treatment, no buffer of trees was left along the stream
channel. A map indicating partially cut W5 plots is included in this
dataset. 180 t/ha of biomass were removed in this harvest.
GRID PLOT MAP
Watershed 5 is overlain by a 25 x 25 meter slope-corrected grid
delineated on the ground by plastic orange poles slid over white
fiberglass stakes at each grid corner. The grid was surveyed in the
summer of 1982 in preparation for the whole-tree harvest. When
measurements began, low corner stakes were labeled with an X-Y
coordinate system. Grid cells with more than 50 percentof their area
lying outside the watershed boundary were not included and not
staked. At the conclusion of the survey, the grid cells (or
"plots") were numbered consecutively from the top left
(west) of the watershed to the bottom. After the whole-tree harvest,
the tall orange poles were added for visibility in the anticipated
dense regrowth. Each cell is now identified in permanent marker on
the orange poles either by X-Y coordinates, or plot number written
on the NW corner stake. The markings wash off and need to be renewed
every few years.
GRID ELEVATION TABLE
This table primarily lists the the NW corner of a grid cell. Where
there are multiple entries for a plot, the second entry indicates
elevation at a second corner – these are the corners of outer grid
cells.
