Effect of topography on farm-scale spatial variation in extreme temperatures in the Southern Mallee of Victoria, Australia

Abstract

Extreme temperatures around flowering of wheat have the potential to reduce grain yield and at farm scale their impact can be spatially variable depending on topography. Twenty-five data loggers were installed at 0.8-m height across a 164-ha farm in the southern Mallee of Victoria, Australia to spatially record the daily course of temperatures around the average date of flowering of wheat in the region. The experiment was conducted during 2years period. In 1 year, the farm had no crop cover and in another year the farm had a wheat crop. Multiple linear regression analysis techniques were used to fit models relating daily extreme temperatures to the farm topographic features of elevation, aspect and slope, and the average maximum and minimum temperatures of each day at the farm in order to identify areas of high risk of extreme temperatures around the time of the flowering of wheat. The fitted regression models explained 90% and 97% of the variability in maximum and minimum temperatures, respectively, when the farm had no crop cover and 80% and 94% of the variability in maximum and minimum temperatures, respectively, when the farm had a wheat crop cover. When the farm had no crop, only minimum temperature was partially explained by the topography however, both maximum and minimum temperatures were partially explained by the topography when the farm had a wheat crop. From this study it was concluded that, (1) high temperature variations were found across the farm (2) temperature variations were only partially explained from the developed model presumably due to the flatter topography of the farm and (3) the relationships obtained from this study could be used in a crop model which can explain variation in grain yield based on the topography of a field.

Breeding for the future: what are the potential impacts of future frost and heat events on sowing and flowering time requirements for Australian bread wheat (Triticum aestivium) varieties?

“…Since 1890, fewer frost days and earlier last‐frost events were recorded in north‐east Australia (Stone et al ., ), while a trend for fewer frost days and more hot days (>35 °C) was observed across the whole of Australia from 1957 to 1996 (Collins et al ., ). These occurred with different intensities depending on the region considered and a great spatial variability in frost and heat events was identified in this study across the Australian wheatbelt (Figs and ), which is at least partly related to elevation and local topography for frost (Boer et al ., ; Dixit & Chen, ), and with latitude for heat events (Fig. ).…”

The sensitivity of topoclimatic models to fine-scale microclimatic variability and the relevance for ecological studies

“…Criticisms include: 1) standardised weather stations shelter instruments from conditions that most organisms experience (Wolfe 1945); 2) observations are made at a height of 1.5-2m and do not reflect the conditions relevant for ground dwelling fauna, germinating seeds, tender saplings or ecological processes (Geiger 1971;Ashcroft et al 2008;Graae et al 2012);3) observations are made on largely flat, unvegetated land, and do not reflect the environments (e.g. gorges / forests) that many species actually live in (Geiger 1971;Kennedy 1997;Suggitt et al 2011);and, 4) neither standardised weather station data nor interpolated macroclimatic grids capture the fine-scale climatic variations that actually occur at regional and landscape scales (Wolfe 1945;Lookingbill and Urban 2003;Dixit and Chen 2011;Scherrer and Körner 2011;.…”

“…These grids have grain sizes as fine as 5-100m and consider a broad range of fine-scale climate-forcing factors such as cold air drainage, topographic exposure and canopy cover (Lookingbill and Urban 2003;Ashcroft et al 2008;Fridley 2009;Vanwalleghem and Meentemeyer 2009;Dixit and Chen 2011;Shoo et al 2010;Holden et al 2011;. While the intent is to produce climatic grids that better capture ecologically meaningful fine-scale variations in climate, it is worth considering the degree to which the above four criticisms are actually overcome.…”

“…While the intent is to produce climatic grids that better capture ecologically meaningful fine-scale variations in climate, it is worth considering the degree to which the above four criticisms are actually overcome. For example, microclimatic loggers have been placed on the shady side of trees (Lookingbill and Urban 2003;Fridley 2009), wrapped in foil (Suggitt et al 2011), or placed inside PVC containers or other radiation shields (Lundquist and Huggett 2008;Vanwalleghem and Meentemeyer 2009;Dixit and Chen 2011;Shoo et al 2010;Holden et al 2011;. Therefore, the fine-scale grids are still produced using sensors that are protected from the conditions that many organisms experience.…”

Regional changes of climate extremes over Australia – a comparison of regional dynamical downscaling and global climate model simulations

“…Pryor et al, 2012), which allows for the simulation of important entities not resolved by GCMs. Examples include topography (Dixit and Chen, 2011;Duliere et al, 2011, Tselioudis et al, 2011Pryor et al, 2012), mesoscale weather patterns (Rummukainen, 2010;Feser et al, 2011), and important climate processes, which, due to coarser resolution, are more highly parameterized in GCMs than RCMs (e.g. convection, soil moisture, Gao et al, 2006;Roy et al, 2011).…”