Drought is a major natural disaster worldwide. Understanding the correlation between meteorological drought (MD) and agricultural drought (AD) is essential for relevant policymaking. In this paper, standardized precipi-tation evapotranspiration index and standardized soil moisture index were used to estimate the MD and AD in the North China Plain (NCP) to identify the correlation between MD and AD during the growth period of winter wheat. In addition, we investigated the contributions of climate change (CC) and human activity (HA) to AD and the factors influencing the loss of winter wheat net primary production (NPP). Drought propagation time (PT) increased spatially from the southern to northern NCP (from 3 to 11 months). PT first increased and then decreased during the phenological period of winter wheat, and the decreasing trend was delayed with an increasing latitude. In general, the relative contribution of CC to AD was higher than that of HA; the correlation between MD and AD exhibited a weakening trend, particularly during the middle and late phenological stages of winter wheat. Precipitation was the main driver of the effects of HA on AD; the effects were stronger in areas with less precipitation. However, because of the improved irrigation conditions and scarce rainfall during the growth period of winter wheat in the study area, the effects of precipitation on AD were nonsignificant. Instead, tem-perature, wind, and total solar radiation, which are highly correlated with evapotranspiration, were identified as the primary drivers of AD; spatiotemporal variations were noted in these correlations. Prolonged drought PT reduced NPP; the sensitivity of winter wheat NPP to AD was higher in humid areas than in semiarid or semi-humid areas. NPP loss occurred primarily due to HA. Our findings revealed a correlation between MD and AD in agroecosystems and may facilitate policymaking related to drought mitigation and food security.

The emergence of Russia as a major grain exporter is not only crucial for the world commercial agriculture and food security, but also for the country's economy. Here we examine the past-to-future thermal suitability for winter wheat (Triticum aestivum, L. 1753) cultivation over Russia and compare it with the recent trends of wheat yields and harvested area. The analyses use a multi-model ensemble median of the most updated bias-corrected outputs from five CMIP5 Earth System Models (1950-2099) under two representative concentration pathways (RCP 4.5 and RCP 8.5) and the Era-Interim dataset (1979-2016). Our results show that the thermal suitability has increased by similar to 10 Mha per decade since 1980. Consistently, winter wheat yields and harvested area have also increased over the last decade by similar to 0.5 t/ha and similar to 4 Mha, respectively. Moreover, a potential for the Russian wheat sector may still be exploited if we consider the abandoned land (similar to 27 Mha) after the collapse of the Soviet Union. Our results also show that the increase in heat availability and the reduction of the frost constraint will likely move the thermal suitability toward the north-western and the Far East regions. Conversely, increases of extreme heat events are projected in the southern regions of Russia, which currently represent the most productive and intensively managed wheat cultivation area. Our findings imply both opportunities and risks for the Russian wheat sector that calls for sustainable and farsighted land management strategies to comprehensively face the consequences of global warming.

Autumn-sown field crops have important agronomic advantages (e.g., reduction of soil erosion and nutrient leaching, maximizing the use of spring moisture) and have the potential to be highly productive even though adverse winter conditions can negatively affect crop viability and yield. In the face of the unpredictable weather patterns and the expected shifts in climate in the near future, there is an imperative to develop methods to quantify both the risk of winter damage and how it is affected by altered climatic conditions and crop variety. We propose a set of indices to characterize synthetically the risk of crop damage stemming from cold spells, extended periods at low temperature, frequent occurrence of freeze-thaw cycles, and prolonged snow cover. An existing model of crop hardening and dehardening is further developed to account in full for the variability of lethal threshold temperature among individual plants. This model is coupled to a simple yet realistic description of crop-sensed temperature, so that required inputs are limited to crop-specific responses to low temperature and standard meteorogical data (average daily temperature and snow depth). This framework is applied to winter wheat under the current climatic conditions for central and southern Sweden. The roles of variety-specific hardening ability, temperature, and snow are assessed separately, thus obtaining indications of the potential impacts of variety selection and future predicted changes in temperature and snow cover in the region. Variety-specific hardening ability and response to exposure to low temperature may drastically alter the extent of winter damage. The most prevalent damaging mechanism depends on the climatic regime, with crops in colder areas benefiting from extended snow cover. A tradeoff between temperature (and hence latitude) and snow emerges, with locations at intermediate latitudes subjected to the highest risk of crop damage from exposure to low temperature and frequent freeze-thaw cycles. The same locations are also characterized by the highest inter-annual variability in the extent of winter damage - a fact that has potential implications for yield reliability. (C) 2014 Elsevier B.V. All rights reserved.