ECOLOGICAL APPLICATIONS OF NEAR-INFRARED REFLECTANCE SPECTROSCOPY A TOOL FOR RAPID, COST-EFFECTIVE PREDICTION OF THE COMPOSITION OF PLANT AND ANIMAL-TISSUES AND ASPECTS OF ANIMAL PERFORMANCE

Many ecological studies rely heavily on chemical analysis of plant and animal tissues. Often, there is limited time and money to perform all the required analyses and this can result in less than ideal sampling schemes and poor levels of replication. Near infrared reflectance spe ctroscopy (NIRS) can relieve these constraints because it can provide quick, non-destructive and quantitative analyses of an enormous range of organic constituents of plant and animal tissues. Near infrared spe ctra depend on the number and type of C-H, N-H and O-H bonds in the ma terial being analyzed. The spectral features are then combined with re liable compositional or functional analyses of the material in a predi ctive statistical model. This model is then used to predict the compos ition of new or unknown samples. NIRS can be used to analyze some spec ific elements (indirectly - e.g., N as protein) or well-defined compou nds (e.g., starch) or more complex, poorly defined attributes of subst ances (e.g., fiber, animal food intake) have also been successfully mo deled with NIRS technology. The accuracy and precision of the referenc e values for the calibration data set in part determines the quality o f the predictions made by NIRS. However, NIRS analyses are often more precise than standard laboratory assays. The use of NIRS is not restri cted to the simple determination of quantities of known compounds, but can also be used to discriminate between complex mixtures and to iden tify important compounds affecting attributes of interest. Near infrar ed reflectance spectroscopy is widely accepted for compositional and f unctional analyses in agriculture and manufacturing but its utility ha s not yet been recognized by the majority of ecologists conducting sim ilar analyses. This paper aims to stimulate interest in NIRS and to il lustrate some of the enormous variety of uses to which it can be put. We emphasize that care must be taken in the calibration stage to preve nt propagation of poor analytical work through NIRS, but, used properl y, NIRS offers ecologists enormous analytical power.