A sustainable agricultural landscape for Australia: A review of interlacing carbon sequestration, biodiversity and salinity management in agroforestry systems

Abstract

Transformation of the south-western Australian landscape from deep-rooted woody vegetation systems to shallow-rooted annual cropping systems has resulted in the severe loss of biodiversity and this loss has been exacerbated by rising ground waters that have mobilised stored salts causing extensive dry land salinity. Since the original plant communities were mostly perennial and deep rooted, the model for sustainable agriculture and landscape water management invariably includes deep rooted trees. Commercial forestry is however only economical in higher rainfall (>700 mm yr −1 ) areas whereas much of the area where biodiversity is threatened has lower rainfall (300-700 mm yr −1 ). Agroforestry may provide the opportunity to develop new agricultural landscapes that interlace ecosystem services such as carbon mitigation via carbon sequestration and biofuels, biodiversity restoration, watershed management while maintaining food production. Active markets are developing for some of these ecosystem services, however a lack of predictive metrics and the regulatory environment are impeding the adoption of several ecosystem services. Nonetheless, a clear opportunity exists for four major issues -the maintenance of food and fibre production, salinisation, biodiversity decline and climate change mitigation -to be managed at a meaningful scale and a new, sustainable agricultural landscape to be developed.

Effects of the shallow water table on water use of winter wheat and ecosystem health: Implications for unlocking the potential of groundwater in the Fergana Valley (Central Asia)

“…In other settings, salinity limits crop varieties suitable for irrigated soils and affects crop development and yield (Katerji et al, 2003). It also affects river, stream, and wetland ecosystems (Hart et al, 1990), impacts of climate change on river ecosystems (Suen and Lai, 2013), river diversions and ecology (Das et al, 2012), river environmental flow requirements (Sun et al, 2009), tolerance of macro-invertebrate and the ecosystem protection trigger values (Dunlop et al, 2008), sustainability of agricultural landscapes, carbon sequestration and biodiversity values (George et al, 2012), vegetation-groundwater interactions (Humphries et al, 2011), pesticide toxicity, ecosystem functions and ecosystem services (Schafer et al, 2012), bioavailability of Cu and Zn and other essential plant micronutrients (Speelmans et al, 2010), and causes changes in grain ultrastructure, amylase, protein and amino acid profiles under water, salinity, and combined stresses (Ahmed et al, 2013). These myriad ecosystem health linkages do imply that under shallow groundwater conditions salinity has implications for river basin health and ecosystems and thus imposes carrying capacity constrains in terms of water-savings and unlocking the potential of groundwater development for irrigation.…”

Plant: soil interactions in temperate multi-cropping production systems

“…Increases in SOC in agroforestry systems ranged from 12 to 77 % (Bambrick et al 2010). According to George et al (2012) plant diversity, productivity and carbon sequestration are interconnected. Carbon sequestration was found to be significantly higher in more diverse agroforestry systems compared to conventional crop systems (Thevathasan et al 2004).…”

“…Soil biodiversity in crop systems is the result of complex interactions between the planned aboveground diversity and the niches created through cultivation practices and rhizosphere processes. Functional diversity plays an important role in soil functioning (George et al 2012), including resilience towards stress, disturbance and disease, and the efficient use of resources, via interactions with rhizosphere processes that are important for plant growth, such as N-fixation, P mobilisation and facilitation, nutrient and water uptake via mycorrhizal fungi, and soil structural dynamics Ritz 2006;Song et al 2007a).…”

“…By intercropping trees and by increasing soil cover and root presence in the topsoil; run-off rates, the risk of soil erosion, salinity and nitrate leaching are reduced (Wang et al 2011;George et al 2012), while key nutrients are being restored (Altieri 1999;Whitmore and Schröder 2007). Further, agroforestry systems sequester more carbon through crop stands and affect organic matter inputs (Malézieux et al 2009;Oelbermann and Echarte 2011;George et al 2012).…”

“…These include: (i) more efficient and complementary use of available resources and niches (Malézieux et al 2009;Tosti and Guiducci 2010); (ii) facilitation via the roots (Vandermeer 1989;Hauggaard-Nielsen and Jensen 2005); (iii) enhanced soil fertility by intercropping nitrogen-fixers (HauggaardNielsen and Jensen 2005); (iv) increased resilience against pests and diseases (Trenbath 1993); (v) increased abiotic stress resistance due to higher levels of functional diversity within the system and resultant complex interactions between associated ecological and biochemical processes (Eisenhauer 2012;George et al 2012).…”