DOI: 10.25952/y2fq-yr97
title: Drivers of pasture physiology and biomass production in tree-pasture systems

description: Demand for animal-based foods is predicted to increase reliance on productive pasture systems. Concurrently, increasing climate hazards such as heat stress will reduce productivity of pasture systems. Trees in managed agricultural landscapes may enhance pasture productivity and resilience to climate change. However, the impact of paddock trees on pasture performance and the extent to which tree cover can buffer the impacts of climate change on pasture species is unclear. 
This dataset presents data collected for the thesis entitled “Drivers of pasture physiology and biomass production in tree-pasture systems”. In the thesis, the influence of scattered or isolated paddock trees on pasture biomass, pasture leaf functional traits and soil chemical properties are presented. Pasture performance and soil chemical properties at different proximities from scattered paddock tree canopies (under canopy, at canopy edge and in open pasture field) were examined. In addition, the impact of different paddock tree densities, represented by tree arrangements/spatial configurations (scattered, strip-planted and clustered) on pasture performance and climate resilience are highlighted. Climate modelling using two climate emission scenarios – the best-case scenario (SSP1-2.6) and the worst-case scenario (SSP5-8.5) were used to predict the thermal safety margins of pasture species at the different tree arrangements.
In pasture systems with scattered paddock trees, both aboveground and belowground pasture biomass were significantly higher under trees but similar at the tree canopy edges and within the open pasture fields. Similarly, soil nutrients were richer under tree canopies compared with open pasture fields. Paddock tree arrangements enhanced leaf functional traits and photosynthetic thermal tolerance of co-occurring pasture species, but responses were species-dependent. The denser tree arrangements, clustered and strip-planted, facilitated greater leaf nitrogen capture compared to the less dense tree arrangement, scattered tree. Climate models predicted significant reductions in thermal safety margins of pasture species, irrespective of the tree arrangement. Despite these reductions, the high leaf critical temperatures of the pasture species suggest less probability for the exceedance of photosynthetic heat tolerance limits.
Understanding photosynthetic thermal thresholds and leaf functional traits is critical for climate change adaptation. A controlled environment experiment was conducted on 18 common pasture species from the Northern Tablelands of Australia – representing four functional types and two photosynthetic pathways – to assess their thermal thresholds and functional traits. Additionally, a glasshouse experiment examined the physiological and growth responses of two selected species under heat stress and recovery to evaluate their acclimation and recovery responses. Photosynthetic traits were generally conserved across classification levels in common pastures from the Northern Tablelands of Australia, while leaf biochemical and growth traits varied with level of plant type. Acclimation and recovery responses to heat stress in leaf functional traits were species-dependent.
The thesis highlights the beneficial impacts of paddock trees on pastures and soil nutrients and supports calls to maintain or increase trees in managed agricultural landscapes. It informs the design of tree-pasture systems and demonstrates potential for increasing pasture growth and nutritional quality. Characteristics of leaf functional traits in pasture species are highlighted. This thesis also demonstrates impacts of heat stress on leaf functional traits and contributes to understanding of the impacts of climate change on pasture species.
description: Demand for animal-based foods is predicted to increase reliance on productive pasture systems. Concurrently, increasing climate hazards such as heat stress will reduce productivity of pasture systems. Trees in managed agricultural landscapes may enhance pasture productivity and resilience to climate change. However, the impact of paddock trees on pasture performance and the extent to which tree cover can buffer the impacts of climate change on pasture species is unclear. 
This dataset presents data collected for the thesis entitled “Drivers of pasture physiology and biomass production in tree-pasture systems”. In the thesis, the influence of scattered or isolated paddock trees on pasture biomass, pasture leaf functional traits and soil chemical properties are presented. Pasture performance and soil chemical properties at different proximities from scattered paddock tree canopies (under canopy, at canopy edge and in open pasture field) were examined. In addition, the impact of different paddock tree densities, represented by tree arrangements/spatial configurations (scattered, strip-planted and clustered) on pasture performance and climate resilience are highlighted. Climate modelling using two climate emission scenarios – the best-case scenario (SSP1-2.6) and the worst-case scenario (SSP5-8.5) were used to predict the thermal safety margins of pasture species at the different tree arrangements.
In pasture systems with scattered paddock trees, both aboveground and belowground pasture biomass were significantly higher under trees but similar at the tree canopy edges and within the open pasture fields. Similarly, soil nutrients were richer under tree canopies compared with open pasture fields. Paddock tree arrangements enhanced leaf functional traits and photosynthetic thermal tolerance of co-occurring pasture species, but responses were species-dependent. The denser tree arrangements, clustered and strip-planted, facilitated greater leaf nitrogen capture compared to the less dense tree arrangement, scattered tree. Climate models predicted significant reductions in thermal safety margins of pasture species, irrespective of the tree arrangement. Despite these reductions, the high leaf critical temperatures of the pasture species suggest less probability for the exceedance of photosynthetic heat tolerance limits.
Understanding photosynthetic thermal thresholds and leaf functional traits is critical for climate change adaptation. A controlled environment experiment was conducted on 18 common pasture species from the Northern Tablelands of Australia – representing four functional types and two photosynthetic pathways – to assess their thermal thresholds and functional traits. Additionally, a glasshouse experiment examined the physiological and growth responses of two selected species under heat stress and recovery to evaluate their acclimation and recovery responses. Photosynthetic traits were generally conserved across classification levels in common pastures from the Northern Tablelands of Australia, while leaf biochemical and growth traits varied with level of plant type. Acclimation and recovery responses to heat stress in leaf functional traits were species-dependent.
The thesis highlights the beneficial impacts of paddock trees on pastures and soil nutrients and supports calls to maintain or increase trees in managed agricultural landscapes. It informs the design of tree-pasture systems and demonstrates potential for increasing pasture growth and nutritional quality. Characteristics of leaf functional traits in pasture species are highlighted. This thesis also demonstrates impacts of heat stress on leaf functional traits and contributes to understanding of the impacts of climate change on pasture species.