Enhancing tree belt productivity through capture of short‐slope runoff water

Abstract

A selection of multi-stemmed, drought-tolerant mallee eucalypts, planted in belt form and integrated with crops in dryland agricultural areas of Australia, may be able to produce biomass as a commercially attractive feedstock for biofuel production. This study aimed to determine if small (40-50 cm high) bunds along mallee belts could trap otherwise underutilized surface water runoff within paddocks, thereby increasing water available to the mallee trees and their growth rates. An experiment was established in 5 year-old Eucalyptus polybractea (RT Baker) mallee belts near the town of Narrogin in the central wheatbelt area of Western Australia. Bunds led to significant (12%) increases in biomass accumulation after about 2 years and 35% increases at around 3 years. Bunds also led to significant increases in predawn leaf water potential and significant decreases in soil water deficit within 12 months, which persisted for the remainder of the 39 month trial. We suggest that the increase in biomass accumulation was largely due to increased water availability, but that increased nutrient supply from run-on and trapping of organic residues may have also had some effect on bunded plots, despite our attempts to mitigate this effect by experimentally adding nutrients to all treatments. Results show that installing bunds along mallee belts would be a cost-effective investment at sites where within-paddock runoff is likely (i.e. gently sloping and with a loamy sand or heavier soil texture). Installation costs should be offset by improved biomass production within a few years and ongoing improvements in growth over the long term.

Determinants of the economic viability of mallee eucalypts as a short rotation coppice crop integrated into farming systems of Western Australia

“…For instance, gains in mallee productivity could be realized by including small (40–50 cm) water retention bunds to capture any surface water flow. Experimental data show that after 3 years, belts with bunds produced 35% more biomass (Bennett et al., 2015). Spencer et al.…”

Climate regulation, energy provisioning and water purification: Quantifying ecosystem service delivery of bioenergy willow grown on riparian buffer zones using life cycle assessment

“…Methodological simplifications predispose CLCA studies to overlook potentially positive environmental consequences that may arise in certain landscape contexts, as identified using a wider ecosystem approach (Valentine et al 2012;Bennett et al 2014). Trees and other low-input perennial bioenergy feedstock planted within agricultural landscapes have the potential to regulate water flow rates and nutrient transfer from soil to water, and also to reduce soil erosion and wind damage (Bennett et al 2014;Carsan et al 2014).…”

“…Trees and other low-input perennial bioenergy feedstock planted within agricultural landscapes have the potential to regulate water flow rates and nutrient transfer from soil to water, and also to reduce soil erosion and wind damage (Bennett et al 2014;Carsan et al 2014). Default emission factors for nitrate leaching, phosphorus runoff and ammonia volatilisation used in LCA studies are typically not calibrated to landscape-context-dependent hydrological and nutrient cycling parameters (Arbault et al 2014).…”

“…Unfertilised willow cultivated on riparian buffer zones and tile drainage filtration areas can achieve greater net environmental benefit compared with randomly sited fertilised willow cultivation, owing to a significant water purification effect that complements the climate regulation benefit associated with fossil fuel substitution. Ecosystem services such as water purification are highly dependent on site-specific hydrological connectivity and nutrient loading, one reason why increasing attention is being paid to the landscape context of bioenergy crop cultivation (Valentine et al 2012;Bennett et al 2014). Yet, such ecosystem services are rarely reflected in LCA studies that commonly rely on default emission factors independent of landscape context.…”

Aviation biofuel from integrated woody biomass in southern Australia

“…Specifically, the longstanding proposition that the problem of dryland salinity can be addressed by tree planting for biomass or other purposes, to increase water use in situ , has generally not shown discernible improvements at a catchment scale . This is due to limitations with the design of tree belts and the limited extent of tree planting in salinized catchments . Revegetation as an integral part of other catchment actions, such as drainage and diversion of surface water and groundwater pumping, is now recommended to address the environmental impact of altered hydrology under current farming systems.…”