Examining the impact of shade on above‐ground biomass and normalized difference vegetation index of <scp>C</scp>₃ and <scp>C</scp>₄ grass species in <scp>N</scp>orth‐<scp>W</scp>estern <scp>NSW</scp>,<scp> A</scp>ustralia

Abstract

Abstract Previous investigations have detected a directional trend in the normalized difference vegetation index ( NDVI ) of pastures around scattered paddock trees and identified shade from the tree as the most likely causal factor. This study uses a field experiment to quantify the effect of varying levels of shade on the above‐ground biomass and NDVI of three grass species native to Australia ( M icrolaena stipoides , C 3 , shade tolerant; A ustrodanthonia richardsonii , C 3 , prefers full sunlight, and C hloris ventricosa , C 4 , prefers full sunlight) in different seasons. The study demonstrates that shade had little influence on the above‐ground biomass of C 3 species but significantly reduced biomass in the C 4 species. Until early winter, the NDVI of each species was generally significantly higher in all shaded treatments than in the no‐shade treatment. This suggests that shaded plants retained a higher proportion of green biomass and/or changed leaf shape, increased leaf area and chlorophyll content. Regardless, although not proven in this experiment, it is likely shade prolonged the retention of green plant material into mid to late winter. Overall, this experiment explains the directional trends in NDVI around scattered trees found in previous work and suggests that shade from scattered trees prolongs green pasture production in a range of native grass species, without loss of C 3 pasture biomass.