Climatic suitability projection for deciduous fruit tree cultivation in main producing regions of northern China under climate warming.

China is the largest fruit producer and consumer market in the world. Understanding the growing conditions responses to climate change is the key to predict future site suitability of main cultivation areas for certain deciduous fruit trees. In this study, we used dynamic and growing degree day models driven by downscaled daily temperatures from 22 global climate models to project the effects of climate change on growing conditions for deciduous fruit trees under two representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios over 2 future time periods (represented by central years 2050s and 2085s) in northern China. The results showed a general increase of available winter chill for all sites under RCP4.5 scenario, and the most dramatic increase in chill accumulation could reach up to 36.8% in northeast regions for RCP8.5. However, the forecasted chill will decrease by 6.4% in southeast stations under RCP8.5 by 2085s. Additionally, the increase rate of growing season heat showed spatially consistency, and the most pronounced increase was found in the RCP8.5 by 2085s. For the southwest station, median heat accumulation increased by 20.8% in the 2050s and 37.1% in the 2085s under RCP8.5. Similar increasing range could be found in the northeast station; the median growing season heat increased by 19.8% and 38.8% in the 2050s and 2085s under RCP8.5, respectively. Moreover, the date of last spring frost was expected to advance and the frequency of frost occurrences was projected to decline in the study area compared to the past. Overall, the present study improves understanding regarding site-specific characteristics of climatic suitability for deciduous fruit tree cultivation in main producing regions of northern China. The results could provide growers and decision-makers with theoretical evidence to take adaptive measure to ensure fruit production in future.

Subseasonal prediction for bloom dates of tart cherries in Utah and Michigan, USA: merging phenological models with CFSv2 forecast.

Temperate fruit trees require chilling for rest completion, followed by sufficient heat accumulation for onset of growth and bloom. The application of phenological models to predict bloom dates has been widely used in orchard management. Examples of such application include selecting adapted cultivars less prone to early bloom, predicting needs for frost protection, and preventing damage from late spring freezes. This study merged the Utah (chill) and ASYMCUR (forcing) phenological models by combining chill units and heat units (measured in growing degree hours) to predict bloom dates of tart cherries (Prunus cerasus L.) in Utah and Michigan, the top producing states of the USA. It was found that the modified Utah model improves the estimation of chill units compared with the original one, while the original Utah model may still be suitable for use in the colder winter of Michigan (with its later bloom dates than Utah). The combined models were applied with the temperature predicted by the Climate Forecast System v2 (CFSv2) model. The prediction was applied twice a month, starting from 1 February to 1 May. The Utah-ASYMCUR model using the forecasted temperature from CFSv2 exhibits subseasonal performance in predicting the bloom dates for 6 weeks in advance. The prediction can offer growers a way to mitigate extreme climate anomalies.

Chilling requirement of Ribes cultivars.

It is usually thought that adequate winter chill is required for the full flowering of many temperate woody species. This paper investigates the sensitivity of blackcurrant bud burst and flowering to natural weather fluctuations in a temperate maritime climate, and compares a range of chill models that have been proposed for assessing the accumulation of winter chill. Bud break for four contrasting cultivars are compared in an exceptionally cold and in a mild winter in Eastern Scotland. The results confirm the importance of chilling at temperatures lower than 0°C and demonstrate that no single chilling function applies equally to all blackcurrant cultivars. There is a pressing need for further model development to take into account the relationship between chilling temperatures and warming temperatures occurring both during and after the chill accumulation period.