Canadian intersite decomposition experiment (CIDET)

• Introduction
• Research results: Measures of litter quality
• Research results: Comparison of 3rd-year results and model predictions
• Research results: Controls on litter decomposition
• Research results: Effects of climate change on litter decomposition
• CIDET Publications and Presentations
• CIDET working group

---

Research results: Effects of climate change on litter decomposition

Predicted changes in mean annual temperature and precipitation for 4 regions from two global circulation models (Table 6) indicate that these regions are likely to experience an increase in mean annual temperature of 1.5 and 4.6oC and an increase in precipitation of between 1 and 2%. These will affect decomposition rates (based on % mass remaining after 3 years) which are predicted to increase 4 to 7% of contemporary rates because of increased temperature and precipitation (Table 6, climate change alone).

This increase may be partially offset by evidence that plants growing under elevated CO₂ concentrations produce litter with high lignin : nitrogen ratios which slows the rate of decomposition. This change would be small compared to the increased rate of decomposition derived from climatic change.

Table 6. Predicted changes in mean annual temperature (°C), precipitation (%), and 3-year mass remaining (%) of jack pine needles for four forest regions of Canada, based on two doubled CO₂ General Circulation Model scenarios: CCC - Canadian Climate Centre GCM II (Boer et al. 1992), and GISS - Goddard Institute for Space Studies transient GCM (Russell et al. 1995). Mass changes were calculated using combined regression in Figure 8, predicted changes in mean annual temperature and precipitation, and an increase in Klason lignin:nitrogen ratio (L:N) of 30%.

Predicted changes in mean annual temperature (°C), precipitation (%), and 3-year mass remaining (%) of jack pine needles for four forest regions of Canada, based on two doubled CO₂ General Circulation Model scenarios

Region	Temperature change				Mass Remaining
	Predicted				Current	Predicted
	CCC		GISS			Climate Change alone		Climate change and L:N
	oC	%	oC	%	%	CCC %	GISS %	CCC %	GISS %
N. Alberta and N. Saskatchewan	+4.3	+10	+1.9	+13	68.2	60.7	64.4	63.7	67.4
N. Ontario	+4.6	+12	+1.8	+6	61.1	52.6	57.7	55.6	60.7
S.E. Ontario and S.W. Quebec	+4.4	+4	+1.5	+6	51.0	43.6	47.9	46.6	50.9
Atlantic Provinces	+4.0	+1	+2.0	+5	47.9	41.3	43.9	44.3	46.9

---