Allochthonous Input and Processing Rates in Silver Creek

1
Allochthonous Input and Processing Ratesin
Silver Creek
M.N.Altman, E.C. First, and T.G. Horvath State
University of New York College at Oneonta

• Introduction According to The River Continuum
  Concept (Vannote et al. 1980), head water streams
  are influenced strongly by the riparian
  vegetation, which reduces autotrophic production
  by decreasing available sunlight and contributes
  large amounts of allochthonous detritus. With the
  lack of sunlight, the streams ecosystem depends
  on this organic material. The morphological
  adaptations of running water invertebrates are
  reflective of the characteristics of the local
  stream.

Methods We collected and categorized the
different allochthonous detritus which entered
Silver Creek. We also followed the decomposition
of beech and maple leaves which entered the
stream. Leaf packs of both maple and beech leaves
were placed randomly in numbered rows (1-16).
Each collection day a row was randomly selected,
collected and the leaf matter dried, weighed, and
checked for invertebrates at irregular intervals
over a 6-month period. Allochthonous inputs were
quantified via the use of wooden traps lined with
mesh screen. We placed 6 traps along the stream
bank (3 on each side) to collect lateral inputs,
and 6 within the stream channel to collect direct
inputs. These traps were checked and the contents
measured and recorded weekly over a 6-week period
from 15 October to 18 November 2004.
120
100
80
Total input (g)
60
40
20
0
Lateral input
Direct input
Figure 1 - Input was not significantly different
between lateral and direct input (t10,0.05
0.17 P 0.87). Error bars are 1 S.E.
30
25
20
Weekly average wind speed (mph)
15
10
5
0
0
100
200
300
400
500

• Results
• No significant difference between lateral or
  direct inputs of organic material.
• The majority of organic material that enters the
  stream is oak (44), birch (24), and maple
  (12).
• Weekly average wind speed and amount of organic
  material found in the stream are strongly
  related.
• Decomposition rates are slower for beech leaves
  than for maple leaves.
• Invertebrates present in leaf packs include
  predators (46), shredders (32), and
  collectors(22).

Amount collected (g)
Figure 2 - Correlation between wind speed and
amount of leaves collected. The Spearman
correlation coefficient 0.94 shows a fairly
strong relationship.
Collected By Species
Oak
Birch
Types of Invertebrates Found in Leaf Packs
Maple
Beech
Seeds/Stems
Aspen
Empididae Predator
Nemoura Shredder
Isoperla Predator
Chironomidae Collector
Baetidae Collector
Cheumatopysche Collector
Other
Dogwood
Invertebrates in Beech Leaf Packs
Invertebrates in Maple Leaf Packs
Invertebrates Present
32
46
22
Literature Cited Vannote, R.L., G.w. Minshall,
K.W. Cummins, J.R. Sedell, and C.E. Cushing.
1980. The river continuum concept. Can. J. Fish.
Aquat. Sci. 37 130-137