ABSTRACT
Future human well-being under climate change depends on the ongoing delivery of food, fibre and wood from the land-based primary sector. The ability to deliver these provisioning services depends on soil-based ecosystem services (e.g. carbon, nutrient and water cycling and storage), yet we lack an in-depth understanding of the likely response of soil-based ecosystem services to climate change. We review the current knowledge on this topic for temperate ecosystems, focusing on mechanisms that are likely to underpin differences in climate change responses between four primary sector systems: cropping, intensive grazing, extensive grazing and plantation forestry. We then illustrate how our findings can be applied to assess service delivery under climate change in a specific region, using New Zealand as an example system. Differences in the climate change responses of carbon and nutrient-related services between systems will largely be driven by whether they are reliant on externally added or internally cycled nutrients, the extent to which plant communities could influence responses, and variation in vulnerability to erosion. The ability of soils to regulate water under climate change will mostly be driven by changes in rainfall, but can be influenced by different primary sector systems' vulnerability to soil water repellency and differences in evapotranspiration rates. These changes in regulating services resulted in different potentials for increased biomass production across systems, with intensively managed systems being the most likely to benefit from climate change. Quantitative prediction of net effects of climate change on soil ecosystem services remains a challenge, in part due to knowledge gaps, but also due to the complex interactions between different aspects of climate change. Despite this challenge, it is critical to gain the information required to make such predictions as robust as possible given the fundamental role of soils in supporting human well-being.
Subject(s)
Climate Change , Soil , Ecosystem , New ZealandABSTRACT
BACKGROUND AND AIMS: Although density-specific stiffness, E/rho, (where E is Young's modulus and rho is wood density) is often assumed constant by the elastic similarity model, and in determination of critical buckling height (H(crit)), few studies have tested this assumption within species. Here this assumption is tested for Pinus radiata growing across an environmental gradient, and theory is combined with data to develop a model of Young's modulus. METHODS: Analyses use an extensive series of environmental plots covering the range of climatic and edaphic conditions over which P. radiata is grown in New Zealand. Reduced major axis regression was used to determine scaling exponents between log-log plots of H(crit) vs. groundline diameter (D), and E/rho vs. D. Path analysis was used to identify significant direct and indirect (through stem slenderness) edaphic and climatic influences on E. KEY RESULTS: Density-specific stiffness exhibited 3-fold variation. As E/rho scaled positively with D, the exponent of 0.95 between H(crit) and D exceeded the assumed value of 0.67 under constant E/rho. The final path analysis model included mean air temperature in early autumn (T(aut)) and slenderness as significant (P < 0.05) positive direct influences on E. Tree leaf area index and T(aut) were indirectly associated with E through their significant (P < 0.05) positive direct relationship with stem slenderness. Young's modulus was most sensitive to T(aut), followed by stem slenderness then leaf area index, and the final model explained 76 % of the variance in E. CONCLUSIONS: The findings suggest that within species E/rho variation may influence H(crit) and the scaling exponent between D and H(crit) so important in assumptions regarding allometric relationships. The model presented may provide a useful means of determining variation in E, E/rho and H(crit) across environmental gradients.
