Forest leaf litter and near infrared reflectance spectroscopy
The use of infrared spectroscopy (NIRS) to determine plant leaf litter chemical compositions, for in situ decomposability and mass loss. Material for investigation was collected as part of a broad nutrient cycling and decomposition study in Australian wet tropical rainforest in the area between Daintree and Townsville, North Queensland. Samples were obtained from litterfall, and litterbag decomposition studies. Subsets of samples were selected using principal components analysis for wet chemistry and calibration development. The concentrations of nitrogen, phosphorous, carbon, magnesium, calcium, acid detergent fibre, acid detergent lignin, α-cellulose, and total phenolics were modeled and predicted in the litterbag (2 treatments, 18 sites in total spanning 6 collections per site and 350 days of exposure, n = 860) and litterfall (40 plots, 2 years of monthly to bimonthly collections, n = 2860) samples. In addition, all these constituents plus magnesium and total phenolics were examined in the litterfall samples. A best subset model including climate and soil fertility variables only slightly out-predicted the NIR decomposability model (r2 = 0.87). The NIR decomposability model significantly predicted potential in situ decomposability in the majority of the litterfall samples. The NIRS approach to forest nutrient cycling and decomposition studies allows for great savings in time and money compared to standard techniques, and also provides a more holistic understanding of the processes and ecosystems in question.