Examining the impact of shade on above‐ground biomass and normalized difference vegetation index of C₃ and C₄ grass species in North‐Western NSW, Australia

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 (Microlaena stipoides, C3, shade tolerant; Austrodanthonia richardsonii, C3, prefers full sunlight, and Chloris ventricosa, C4, prefers full sunlight) in different seasons. The study demonstrates that shade had little influence on the above‐ground biomass of C3 species but significantly reduced biomass in the C4 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 C3 pasture biomass.

Morphogenesis, biomass and nutritive value of Panicum maximum under different shade levels and fertilizer nitrogen rates

“…Barnes et al . () found that shade greatly reduced biomass accumulation of a native Australian C 4 species, Chloris ventricosa , but had little effect on two native C 3 grasses. Under conditions of intense and permanent shade, the low photosynthetic capacity significantly decreased the biomass production of tropical forage grasses (Santiago‐Hernández et al ., ), which indicates that excessive shading should be avoided if high biomass production is required.…”

Productivity and nutritive value of Brachiaria decumbens and performance of dairy heifers in a long‐term silvopastoral system

“…However, pasture management in SPS is more complex when compared to an open pasture (OP). One of the main limitations in SPS is the decrease in the amount (i.e., photon flux density) and the quality (e.g., changes in the red: far red) of the photosynthetically active radiation (PAR) incident on the forage canopy with the age of the trees, which can reduce tillering and forage production and alter nutritive value (Abraham et al., ; Barnes et al., ; Neel & Belesky, ).…”

Effect of artificial shade and grazing removal on degraded grasslands: Implications of woody restoration for herbaceous vegetation

“…), although these effects depend on the physiology of individual species (Barnes et al . ). Shade can also alter substrate conditions, in particular soil moisture levels, as a result of reduced temperature and evapotranspiration (Ludwig et al .…”

“…etiolation). The direct effects of shade on pasture grasses have been well documented (Dodd et al 2005), although these effects depend on the physiology of individual species (Barnes et al 2015). Shade can also alter substrate conditions, in particular soil moisture levels, as a result of reduced temperature and evapotranspiration (Ludwig et al 2001), especially in areas that experience strong soil moisture deficits such as the Mackenzie Basin.…”