264 
Reflectance (%) Reflectance (%) 
Bare Soil - - - - • Pine (lyr) : Pine (3 >ts) pine (lOyrs) —— .» - Pine (23yrc) Pine (48yrs) 
Waer Dedduooi ————. ora*» Road Ur tan Area 
Figure 3 : AVIRIS reflectance spectra, (a) without atmospheric corrections, (b) with atmospheric corrections. 
II.4 Laboratory analyses 
* Chemical measurements 
Chemical analyses of total nitrogen (N), lignin (L) and cellulose were conducted by Europe Sol*. Total 
nitrogen (N) was calculated as 6.25 times the Kjeldahl nitrogen content (A.O.A.C., 1970), after digesting 
samples in a block digestor using sulphuric acid. Lignin and cellulose were determined using a modified Van 
Soest and Wine (1970) method: 
- s tep 1 : hydrolysis of samples in neutral detergent solution for one hour yields neutral detergent fibre (NDF), 
i.e. hemicellulose, cellulose, lignin and mineral matter. 
- step 2 : hydrolysis of NDF in acid detergent solution (cetyltrimethylammonium bromide) for one hour yields 
acid detergent fibre (ADF), i.e. cellulose (Cell S), lignin and mineral matter. Comparison with step 1 gives 
hemicellulose (Hemi) concentration. 
- step 3 : lignin (L) and mineral matter are measured as the fraction of ADF that is insoluble in sulphuric acid; 
comparison with step 2 gives cellulose (Cell S) concentration. 
- step 4 : the loss of weight up on ashing the mineralised residue leaves mineral matter; comparison with 
step 3 yields lignin (L) concentration. 
* Europe Sol is a laboratory for plant analyses, 45 rue de Geronis, 31200 - Toulouse, France.