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

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Research results: Controls on litter decomposition

The 21 sites (Table 4) cover a broad range of conditions from the wet (yearly precipitation 1783 mm), mild (9.3oC mean annual temperature) Douglas-fir and western hemlock forested sites in the pacific cordilleran ecoclimatic region (SHL, PMC) to the dry (266 mm), cold (-9.8°C), black spruce forested sites in the subarctic (GI1, INU). Across all litter types, annual temperature was the best single climate predictor tested (r2=.316 all data; 0.722 sitemean), inclusion of annual precipitation improved the fit (r2=0.378 all data; 0.865 sitemean) (Figure 6).

Table 4: Site yearly climate normals, latitude and elevation. Wetland sites in italic.

Site yearly climate normals, latitude and elevation.

Site	Site Code	T 30yr oC	P 30yr mm	Lat. D	Elev. (m)
Inuvik	INU	-9.8	266	68	73
Gillam1	GI1	-5.2	485	56	140
Gillam2	GI2	-5.2	485	56	125
Schefferville	SCH	-4.8	769	54	500
Nelson House1	NH1	-3.9	542	55	288
Nelson House2	NH2	-3.9	542	55	260
Whitehorse	WHI	-1.2	361	60	667
Batoche	BAT	0.1	398	52	472
Prince Albert	PAL	0.1	398	53	476
Montmorency	MON	0.6	1494	47	670
Chapleau	CHA	1.1	834	47	460
Termundee	TER	1.8	371	51	536
Topley	TOP	2.5	513	54	1100
Kananaskis	KAN	2.8	657	51	1530
CB Rocky Harbour	CBR	4.2	1200	49	50
Gander	GAN	4.3	1130	48	115
Petawawa	PET	4.3	822	45	173
Morgan Arboretum	MAR	6.1	863	45	48
Hidden Lake	HID	6.3	547	50	650
Port McNeill	PMC	7.9	1783	50	100
Shawnigan Lake	SHL	9.3	1215	48	355

 

As noted previously, different litters covered a broad range or %N and %Klason lignin concentrations, with wood have greatly different from the foliar litter types (Table 5). Of all litter quality measures the ratio of % Klason lignin to % total N gave the best fit (r2= 0.265 all data; 0.738 typemean) though regressions differed with wood blocks excluded.

Table 5. Original nitrogen content and Klason lignin:N ratio for 11 litter types.

Original nitrogen content and Klason lignin:N ratio for litter types.

Litter type	Code	N(mg g-1)	Klason lignin:N
Aspen leaves	Dbt	6.7	21.4
Beech leaves	Dba	7.1	39.4
Bracken fern	Fbf	8.8	37.4
Black spruce needles	Csb	7.3	38.7
Douglas fir needles	Cdc	7.0	43.3
Fescue grass	Gfh	7.1	15.7
Jack pine needles	Cpj	12.8	25.6
Tamarack needles	Cll	5.9	40.6
White birch leaves	Dbw	7.2	33.3
Western hemlock wood blocks	Whw	2.4	122.6
Western red cedar needles	Ctp	6.4	55.5

The combination of lignin/N and annual temperature was highly significant (r2=.659, p<.001, all data) though inclusion of annual precipitation did improve the fit (r2=.729, p<.0001, all data).

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