Canadian intersite decomposition experiment (CIDET)

Research results: Comparison of 3rd-year results and model predictions

Third year mass loss averaged 35% (65% mass remaining) across all sites and litter types. Within foliar litters, fescue decayed the most rapidly (42% remaining), western red cedar the least (75% remaining) (Table 3). Highest decay rates were observed at Pacific Cordilleran sites (SHL=43%, PMC= 46% mass remaining) and least in high latitude sites (INU=87%, WHI=83% mass remaining). More variation in decay was observed within site (Std. errors 1.5 to 2.9) than within a litter type (Std. errors 1.0 to 2.3).

Litter quality data were used in three simple models of litter decay to predict how mass loss of the different litter types could vary. Model rankings of foliar litter types varied somewhat, Aber's was more different and had the lowest range of predicted mass loss compared Melillo's or Taylor's. Pearson correlations coefficients of model to third year data were highest for Mellilo's (0.87 p=.0004) and Taylor's (0.80 p=.0029) and low and not significant for Aber's (0.50 p=0.1178) Spearman's rank correlation coefficient for each model to data was large and significant for Melillo's (0.91 p=.0001) and Taylor's (0.90 p=.0002) and low and not significant for Aber's (0.37 p=0.2589). The higher overall mass losses predicted by Aber's and Melillo's model compared to Taylor's probably reflects the locations for which the models were derived.

Ranking of litter types based on predictions of remaining percent mass from three models of litter decay, Aber et al 1990 (3 year decay), Melillo et al 1982 (3 year decay), Taylor et al 1992 (3 year decay), and based on 3rd year results of actual remaining percent mass. Aber's is a summed exponential decay model for three litter fractions each k a function of a lignocellulose index; Melillo's is an exponential decay model with k a function of the lignin:N ratio; Taylor's is a piecewise linear model of lignin and N.

Table 3. (a) Percent mass remaining after the first 3 years, meaned across the 12 litter types.

Percent mass remaining after the first 3 years, meaned across the 12 litter types.
Litter Type Mean std err Max Min
Whws 90.4 1.8 108.0 32.4
Whwb 86.8 2.3 112.8 12.2
Dbw 49.4 2.0 82.0 16.5
Ctp 75.3 1.9 110.6 32.0
Cdc 67.6 2.0 93.8 24.6
Csb 56.2 1.9 87.3 24.8
Dpt 56.3 1.6 93.4 22.5
Cpj 60.4 1.8 86.9 24.6
Dba 70.9 1.6 91.1 39.0
Cll 66.0 1.9 120.4 26.4
Gfh 41.8 1.0 67.5 19.8
Fbf 64.5 1.7 88.0 25.4

 

Table 3. (b) Percent mass remaining after the first 3 years meaned across 21 sites in CIDET.

Percent mass remaining after the first 3 years, meaned across 21 sites in CIDET.
Site Mean std err Max Min
BAT 77.5 2.6 120.4 30.6
CBR 52.2 2.8 100.4 24.6
CHA 52.8 2.8 97.1 16.5
GAN 55.5 2.9 103.3 28.4
GI1 80.1 2.2 103.1 39.9
GI2 71.7 2.4 100.6 38.2
HID 59.1 2.6 96.9 30.6
INU 86.9 1.5 106.5 54.6
KAN 68.1 2.3 98.7 30.0
MAR 44.1 2.4 83.3 12.2
MON 60.0 2.9 100.0 32.9
NH1 79.8 2.2 112.8 43.8
NH2 73.4 2.4 102.1 37.8
PAL 75.7 2.0 99.9 40.6
PET 52.6 2.4 90.8 25.4
PMC 46.5 2.9 95.8 17.8
SCH 69.9 2.6 101.6 29.2
SHL 43.4 2.4 92.8 22.2
TER 71.9 2.4 100.2 34.7
TOP 68.6 2.6 99.5 28.5
WHI 82.3 1.8 100.8 52.1
All Sites 65.4 0.7 120.4 12.2
Research results: Comparison of 3rd-year results and model predictions
Research results: Controls on litter decomposition

Project status

  • On-going

Team members