Effects of acidification on leaf litter decay and utilization in a whole-ecosystem experiment
Recent work suggests that the manipulation of natural ecosystems may be best to detect effects on complex processes such as decay of terrestrial leaf liter. Care must be taken when analyzing results, and involve three steps: detecting change, attributing change to the manipulation, and identifying mechanisms. Red oak and paper birch leaf decomposition were studied in 1987-1990 in Little Rock Lake, site of a divided-basin (treatment and reference), artificial acidification project in northern Wisconsin. Randomized intervention analysis detected a reduction in oak decay in 1987 (treatment basin pH 5.2) and 1988 (pH 5.1), when compared to pretreatment (1983) and reference conditions (pH 6.2). Rates of birch decay were not affected to the same extent, and not until further pH reductions in 1989 (pH 4.8) and 1990 (pH 4.9). The study of spatial and temporal patterns of leaf decay in additional reference lakes in 1987-1990 revealed leaf decay to be a lake-specific parameter (different among lakes consistent among years), controlled by in-lake characteristics, such as pH, which alone accounted for 58% and 48% of the variation in oak and birch decay. Because microbial (especially bacterial) colonization of decaying leaves is important, and some populations are sensitive to acidification, these populations were studied. Benthic invertebrates in the reference basin relied heavily on leaf carbon (78% to 93% of assimilated carbon of terrestrial origin), while invertebrates in the treatment basin did not (e.g, % TC chironomids and oligochaetes 56.6%). Slower rates of decay and impacts on microbial colonizers after acidification appear to have reduced the utilization of leaf carbon in Little Rock Lake.
- Research Organization:
- Minnesota Univ., Minneapolis, MN (United States)
- OSTI ID:
- 39159
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1994
- Country of Publication:
- United States
- Language:
- English
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