Decomposition Rates of Slippery Elm and Silver Maple Leaves in Two Suburban Streams

1
Decomposition Rates of Slippery Elm and Silver
Maple Leaves in Two Suburban Streams

• Antonia Giardina and Ken Belt
• MEES 683, Spring 2003
• Stream Ecosystem Structure and Function

2
Need for Research

• Decomposition- a key process in streams
• Leaf litter decay rate- a measure of the
  decomposition process
• Less research on stream processes (function) than
  on structure (e.g., taxa richness, biotic
  indices, etc.)
• Little litter decomposition work on urban
  watersheds
• Data collection before/after restoration project

3
Two Suburban Watersheds

• Stewart April Lane (SAL)
• 1st Order Stream
• 0.4 mi2 Basin
• 12 Forest
• 40 Impervious

• Paint Branch
• (PB)
• 2nd Order Stream
• 1.3 mi2 Basin
• 21 Forest
• 9 Impervious

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Methods

• Deploy leaves in mesh bags in riffles/runs
• Retrieve 3 replicates of each species at weekly
  intervals
• 19 Feb 30 Apr 2003
• Dry at 50 degrees C Ash at 550 degrees C to
  obtain AFDM
• Use weekly samples to estimate the proportion of
  mass remaining
• ANCOVA used for statistical analysis

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Two Riparian SpeciesCollected from Middle
Patuxent River, Howard County (fall 2002)

• Slippery Elm
• Ulmus rubra
• Moist soils, lower slopes and floodplains, often
  on dry uplands
• Silver Maple
• Acer saccharinum
• Wet soils on streambanks, floodplains, swamps

Sutton and Sutton 1986
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Computation of the Decay Constant (k)
Wt / W0 e kt or Ln(Wt / W0) -kt (k is the
slope of the linear function)
k decay rate (day-1) Wt mass remaining at
time t (g) W0 initial mass (g) t time elapsed
(days)
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Null Hypotheses

• Decay constants for Silver Maple and Slippery Elm
  are not different from each other
• Decay constants at SAL and PB are not different
  from each other for either species

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Maple vs. ElmMaple decomposed significantly
faster than Slippery Elm only at SAL
Figure 1
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SAL vs. PBNo Significant Difference(Pgt0.05)
Figure 2
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Initial Mass Losses (1st week)
Figure 3
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Comparative Values of k
Table 1
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Controls on Decomposition

• Leaf Chemistry
• Water Chemistry
• Invertebrate Activity
• Microbial Activity

Table 2
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Controls on DecompositionCont.

• Physical Properties
• Temperature
• Hydrology
• Sediment

Table 3
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Hydraulic ImpactsLots of Precipitation
Figure 4
Leaf bag Deployment Collection
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Sediment AccumulationSAL leaf bags accumulated
sediment faster than PB
Figure 5
SAL
PBr
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Summary

• Maple decomposed faster at both sites, though
  only significantly faster at SAL
• Decomposition rates were higher at SAL than PB,
  but not significantly higher
• Why?
• Leaf quality
• Water chemistry
• Invertebrate activity
• hydrology