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: Measures of litter quality

To characterize litter quality of the 11 standard litter types we analyzed the initial elemental contents (C, N, P, S, K, Ca, Mg) and C fractions (extractables, cellulose, hemicellulose, lignin) by wet chemical proximate analysis and solid-state C-13 CPMAS NMR. Litter types especially non conifer species varied greatly in their qualities. Principal component analysis (Table 2) showed that litter type could be distinguished by elemental macronutrient contents through the ratio of N+P+K:S, by proximate chemical analyses through the ratio of water soluble:acid fractions, and by NMR through the ratio of O alkyl:alkyl carbon.

Examination of proximate fractions from a selection of litter types showed that alkyl C from surface waxes and cutin, as well as the condensed tannins contribute to a large fraction of the acid insoluble residue "lignin". This "lignin" parameter plays a large role in several models of litter decay, but has little chemical or biological meaning.

Table 2: Summary of the Principal Component analyses of elemental content, proximate chemistry and NMR spectral data. For each of the top four principal components (PC) the eigenvalue and proportional (PrVar), cumulative (CumVar) variance explained are shown with eigenvectors and loading from each variable.

Summary of the Principal Component analyses of elemental content.

Eigenvalues				Eigenvectors
PC	Value	PrVar	CumVar	C	N	P	S	Ca	Mg	K
1	2.53	0.36	0.36	-0.30	0.40	0.42	-0.40	0.28	0.32	0.48
2	1.23	0.18	0.54	0.63	0.24	-0.07	-0.34	0.57	-0.16	0.47
3	0.98	0.14	0.68	0.09	0.36	0.48	0.29	-0.16	-0.71	0.14
4	0.68	0.10	0.77	0.40	0.53	-0.16	0.12	0.65	0.32	0.02

 

Summary of the proximate chemistry.

Proximate Chemical Fractions (mg/g)
PC	Value	PrVar	CumVar	NPE	WSE	ACID	LIG	ASH
1	2.21	0.44	0.44	0.44	0.508	-0.56	-0.25	0.31
2	1.34	0.27	0.71	0.36	-0.17	-0.42	0.74	-0.34
3	0.82	0.16	0.88	0.12	-0.42	0.02	0.25	0.86
4	0.62	0.12	0.99	0.79	-0.32	0.34	-0.34	-0.17

 

Summary of the NMR spectral data.

NMR Spectral Regions
PC	Value	vPrVar	CumVar	Alkyl	Methox	OAlkyl	Arom	Pheno	Carbox
1	2.44	0.41	0.41	-0.59	0.21	0.54	0.41	-0.09	-0.38
2	1.73	0.29	0.70	0.02	-0.05	-0.38	0.54	0.72	-0.19
3	0.95	0.16	0.85	0.13	0.96	-0.17	-0.16	0.06	-0.11
4	0.77	0.13	0.98	-0.41	0.17	0.03	0.11	0.19	0.87

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