Identifying Crop and Orchard Growing Stages Using Conventional Temperature and Humidity Reports

Abstract

Vegetation is a climate modifier: It is a primary modifier, such as the Amazon rain forest, or secondary modifier, such as the agricultural fields of Pannonian lowlands in Central Europe. At periods of winter crop spring renewal and the start of the orchard growing season, enhanced evapotranspiration shifts energy balance partitions from sensible toward latent heat flux. This surface flux alteration converges into the boundary layer, and it can be detected in the daily variations of air temperature and humidity as well as daily temperature range records. The time series of micrometeorological measurements and phenological observations in dominant plant canopies conducted by Forecasting and Reporting Service for Plant Protection of the Republic of Serbia (PIS) are explored to select indices that best record the signatures of plant growth stages in temperature and humidity daily variations. From the timing of extreme values and inflection points of relative humidity (R1 and R2) and normalized daily temperature range (DTR/Td), we identified the following stages: (a) start of flowering (orchard)/spring start of the growing season (crop), (b) full bloom (orchard)/development (crop), (c) maximum LAI reached/yield formation (orchard and crop), and (d) start of dormancy (orchard)/leaf drying (crop). The average day of year (DOY) for dominant plants corresponds to the timing obtained from climatological time series recorded on a representative climate station.