The Response of First Flowering Dates to Abrupt Climate Change in Beijing

Phenological data on the First Flowering Date(FFD) of woody plants in Beijing from 1963-2007 are analyzed.The correlation between each species’ yearly FFD and the mean monthly temperatures for every year over a 45-year period is used to identify the month in which temperature has the most effect on FFD. Through further analysis,the FFDs of 48 woody plant species are shown to have advanced an average of 5.4 days from 1990-2007 compared to 1963-1989.The results indicate that 70.8%of species flowered significantly earlier(7 days on average) during the period 1990-2007,while only one species(2.1%) flowered significantly later.Moreover,the responses of FFD to climate change are shown to be different in two climatic stages, defined by an abrupt climate change point.Thirty-three species which first flower in March and April are sensitive to temperature are examined.The correlation coefficients between FFD and temperature for 20 species during the latter period(1990-2007) are shown to be larger than during the former period(1963- 1989),with a difference of around -0.87 days per 1℃on average.The paper concludes that with the warming of climate,the linear trend of FFD variation,as well as its responsiveness to temperature,became more prominent during 1990-2007 than 1963-1989.The data analyzed in this study present a strong biological indicator of climate change in Beijing,and provide further confirmation of previous results from regional and local studies across the Northern Hemisphere.Phenophase variations indicate that the climate is changing rapidly.

Study on Prediction of the First Flowering Date of Osmanthus fragrans

[ Objective] The study aimed to forecast the first flowering date of Osmanthus fragrans. [ Method] Based on the data about flowering stage of O. fragrans in Guilin City from 1999 -2012, the correlation between meteorological factors and the first flowering date of O. fragrans was analyzed, and a forecast model for the first flowering date of O. fragrans was established. EResult] Among meteorological factors, precipitation, humidity, temperature and sunshine hours could obviously affect the first flowering date of O. fragrans, especially humidity in August, temperature and sunshine hours in September. The forecast model could exactly forecast the first flowering date in the partial early or too late year, and the av- erage error of date was 6 days. The factors influencing the first flowering date of O. fragrans are complex, and there is an artificial error in record data of the flowering stage, so using a single model to forecast the first flowering date have some disadvantages. When forecasting the first flower- ing date, we should consider all influencing factors to get a good forecast result. [ Conclusion] The research could provide a new method to forecast the first flowednq date of O. fraclrans.

Changes of the Flowering Time of Trees in Spring by Climate Change in Seoul, South Korea

Flowering onset has attracted much attention in ecological research as an important indicator of climate change.Generally,warmer temperatures advance flowering onset.The effect of climate warming on flowering onset is more pronounced in spring because the difference between atmospheric and water temperatures creates more rapid convection than in other seasons.We analyzed the correlation between 73 species of spring woody plants in Hongneung Arboretum in Seoul,South Korea and the spring minimum temperature and average precipitation over the past 50 years(1968–2018).The spring minimum temperature and average precipitation have increased over the past 50 years,resulting in the advance of the first flowing date(FFD)in all 73 species by 8.5 days on average.A comparison of FFD changes over time by dividing the survey period into three time periods confirmed the advance of the FFD in 50 species(68%of investigated species)by 11.1 days on average in both Period 2(1999–2008)and Period 3(2009–2018)relative to Period 1(1968–1975).Additionally,a delay of the FFD by 3.2 days on average was observed in 8 species.The FFD of Lonicera chrysantha(Caprifoliaceae)advanced by over 40 days and was highly correlated with the increased spring minimum temperature.Analysis of the sensitivity of plant responses to climate change revealed that a temperature rise of 1℃ was associated with an FFD advance of 1.2 days in all species.The species that was most sensitive to temperature change was Spiraea pubescens for.leiocarpa(Rosaceae),whose FFD advanced by 4.7 days per 1℃ temperature rise.Each increase in precipitation by 1 mm was found to result in a 0.1-day advance of the FFD of all species.Prunus tomentosa(Rosa-ceae)was the most sensitive species,that advanced by 2.6 days for each 1 mm increase in precipitation.Thus,for all species,the FFD was more sensitive to the change in temperature than in precipitation.Assuming that the current greenhouse gas(GHGs)emission levels or atmospheric CO_(2) concentration is maintained,Seoul’s spring minimum temperature is projected to rise by 2.7℃ over the next 50 years.Accordingly,considering only the global temperature change,the mean FFD of the study’s 73 species is projected to advance by an additional 3.4 days.

The decreasing spring frost risks during the flow- ering period for woody plants in temperate area of eastern China over past 50 years

The temperate monsoon area of China is an important agricultural region but late spring frosts have frequently caused significant damage to plants there. Based on phenological data derived from the Chinese Phenological Observation Network （CPON）, corresponding meteorological data from 12 study sites and phenological modeling, changes in flowering times of multiple woody plants and the frequency of frost occurrence were analyzed. Through these analyses, frost risk during the flowering period at each site was estimated. Results of these estimates suggested that first flowering dates （FFD） in the study area advanced significantly from 1963 to 2009 at an average rate of -1.52 days/decade in North-east China （P〈0.01） and -2.22 days/decade （P〈0.01） in North China. Over the same period, the number of frost days in spring decreased and the last frost days advanced across the study area. Considering both flowering phenology and occurrence of frost, the frost risk index, which measures the percentage of species exposed to frost during the flowering period in spring, exhibited a decreasing trend of -0.37% per decade （insignificant） in Northeast China and -1.80% per decade （P〈0.01） in North China, implying that frost risk has reduced over the past half century. These conclusions provide important information to agriculture and forest managers in devising frost protection schemes in the region.