HEAT STRESS-CROP YIELDS INTERACTIONS UNDER SUMMER WARMING TRENDS: INSIGHTS FOR THE SOUTHERN CROPPING LOWLANDS OF ROMANIA
Journal Title: Revue Roumaine de Géographie/Romanian Journal of Geography - Year 2017, Vol 61, Issue 2
Abstract
Extreme heat is an emerging threat to the agricultural sector, which severely affected the crop yields in many regions of Romania during the last two decades. Here we investigate a 53-year climatology of daily maximum air temperatures to extract the regional characteristics of summer heat stress in the southern cropping lowlands of Romania (Oltenia and Muntenia regions) and to estimate the yield sensitivity of three major crops (winter wheat, grain maize and sunflower) to the changing heat stress under the ongoing warming. In our approach we aim to test the hypothesis of a cause-effect relationship between seasonal heat stress and the annual crop production at county level (NUTS3), considering the existing adaptation potential through irrigations, especially during the heat stress representative years of 2000, 2007 and 2012. Our results reveal that, in both cropping regions, there is a significant and spatial robust increase in the frequency and duration of heat stress, especially since the mid-1980s, confirming the findings of previous studies on climate variability and climate extremes. The changes in summer heat stress determined different and spatially variable crop yield sensitivities. The main findings of the regression analyses on heat stress-crop yield relationships are: summer heat stress allowed explaining 17 to 55% of the annual variability of yields at county level; during the hot and droughty summers of 2000, 2007 and 2012, the detrimental effect of heat stress on crop yields was particularly evident and worsened by the lack of efficient water compensations through irrigations (generally below 5% in Oltenia and 7% in Muntenia); heat stress was found to be an important predictor of crop yield failures, especially for maize crops; for the summer harvesting crops (winter wheat) and good high temperature and drought resistance (sunflower), the detrimental effects of heat stress appear less evident; recurrent heat stress days (HSD, HSDD) and heat stress spells (HSSfr) have had a greater influence on final crops than the persistent individual heat stress spells (HSSdurmax). Both agricultural regions are heat stress sensitive, but the cropping areas which underwent substantial crop production losses due to extreme high temperatures are located in the southernmost floodplain areas (e.g. in the Dolj, Olt, Gorj, Giurgiu, Călăraşi counties), where heat stress is particularly intense and frequent. Rehabilitation of irrigation emerges as an important adaptation measure in agriculture to reduce the current vulnerabilities and future impacts of heat stress on national food security.
Authors and Affiliations
DANA MICU, ELENA-ANA POPOVICI, LOREDANA-ELENA HAVRIŞ, CARMEN-SOFIA DRAGOTĂ
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