New Zealand Journal of Marine and Freshwater Research abstracts
Preliminary estimates of mass-loss rates, changes in stable isotope
composition, and invertebrate colonisation of evergreen and deciduous leaves
in a Waikato, New Zealand, stream
BRENDAN J. HICKS
J. LEE LABOYRIE
Department of Biological Sciences
University of Waikato
Private Bag 3105
Hamilton, New Zealand
Abstract Rates of mass loss are important in the choice of
tree species used in riparian rehabilitation because leaves that break down
fast should contribute to stream food-webs more rapidly than leaves that break
down more slowly. To examine comparative mass-loss rates of some native
evergreen and introduced deciduous trees in a New Zealand stream, fallen leaves
were incubated in bags with 2 x 3 mm mesh openings. The native trees were
mahoe (
Melicytus ramiflorus), kahikatea (
Dacrycarpus
dacrydioides), silver beech (
Nothofagus menziesii), rewarewa
(
Knightia excelsa), tawa (
Beilschmiedia tawa), and the introduced
trees were silver birch (
Betula pendula) and alder (
Alnus
glutinosa). The leaf bags were left in the Mangaotama Stream for 28 days
from mid April to mid May 1995 when mean water temperature was 14.5deg.C,
giving a total of 406 degree days. Rates of mass loss followed the sequence:
mahoe > silver birch > alder > kahikatea > silver beech >
rewarewa > tawa. Mean mass-loss rate for mahoe, assuming a negative
exponential model, was 0.0507
k day
-1 (0.00350
k
(degree day)
-1), and for tawa was 0.0036
k day
-1
(0.00025
k (degree day)
-1). C:N ratio decreased on average
from 45:1 to 35:1, and d
15N increased between 0.7 and
3.0[[perthousand]] (1.8 +/- 0.41[[perthousand]], mean +/-1 standard error),
excluding kahikatea. Changes in d
13C were smaller and not consistent
in direction. Biomass of invertebrates was greatest in bags that had lost
25-45% of their initial leaf biomass.
Keywords mass loss; leaf litter; invertebrate colonisation;
carbon; nitrogen; stable isotopes
M98029
Received 11 June 1998; accepted 10 December 1998
Short communication
PDF file of entire paper: medium quality (963K); (scanned from paper original: notes about this process)
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