Spatial Interrelationships between Wheat Phenology, Thermal Time, and Terrain Attributes

Abstract

Spatial variation of winter wheat (Triticum aestivum L.) phenology across complex terrain has received little attention despite its importance for assessing overall crop status and making key precision management decisions. Temperature is the environmental factor explaining the greatest variation in phenology, and temperature varies across a landscape. Our primary hypothesis was that variability in thermal time (TT) by landscape position could explain the phenological variation, with a secondary hypothesis that spatial patterns of TT and phenology were related to terrain attributes. Four years of phenology and soil and air temperature data were collected from a 100-ha fi eld in northeast Colorado. Five developmental stages were monitored at 10 landscape sites each year. Terrain attributes were computed using 5-m-grid land surface elevation data. Spatial diff erences in reaching developmental stages across sites varied from 2 to 12 d within a year. Up to 96% of the phenological variation among years was explained when using a general TT model pooling all data. Refi ning the TT model, however, by using either air or soil TT at specifi c sites partially supported the primary hypothesis only for the relatively wetter 2004-2005 and 2006-2007 years (regression relationships explained up to 72% of the variation). Similarly, terrain attributes occasionally explained spatial patterns of phenology in the two wetter years, and attributes with the highest explanatory power varied among years and developmental stages. Further research is needed to better understand the controlling environmental factors and predict spatial patterns of wheat phenology for precision management using terrain attributes.

Reconciling the discrepancy in ground‐ and satellite‐observed trends in the spring phenology of winter wheat in China from 1993 to 2008

“…Meteorological SOS represents an average temperature status for a period of time and coincides with the cumulative effect of temperature to the onset of vegetation spring phenology [ Ault et al ., ]. We chose SOS as the study phenological event because (1) it determines the length of the growing season and is crucial for grain yield [ Wang et al ., ; Salazar‐Gutierrez et al ., ], (2) the algorithm for satellite‐based SOS identification is well established, and (3) the shift in winter wheat SOS is exclusively driven by temperature rather than differences in the cultivars and cropland management [ McMaster et al ., ; Xiao et al ., ], and thus, the observed changes in winter wheat SOS should synchronize with meteorological SOS dynamics. Our results demonstrated that compared with ground observations, satellite data correlated more closely with meteorological data in terms of both long‐term trends and interannual variations of winter wheat SOS.…”

Winter Wheat Phenology Simulations Improve when Adding Responses to Water Stress

“…The sensor was placed at a 1‐m height above the soil surface and maintained at this height regardless of the canopy height, which for our variety and environments was always less than the sensor height. Further details for this experiment can be found in McMaster et al (2012).…”

“…Weather data are given for different intervals related to seasons or periods for developmental stages. Updated fromMcMaster et al (2012).…”

Integration of a Three-Dimensional Process-Based Hydrological Model into the Object Modeling System

“…The field site has been described and studied previously regarding terrain analysis [31], spatial scaling of infiltration rates [32], temporal dynamics of measured soil moisture at different landscape positions [33], one-dimensional simulations of soil moisture ( [14,34]), and interrelationships between terrain and wheat development [35]. The watershed defined by an outlet at the eastern edge of the cropped field has an elevation range of 1559-1588 m, a mean annual precipitation of approximately 350 mm, and a mean annual evapotranspiration of approximately 1200 mm.…”