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Article

Helfried Scheifinger

Phenology is the study of the seasonal timing of life cycle events. The Belgian botanist Charles Morren introduced the term in 1853, which is a combination of two Greek words, φαίνω, which means to show, to bring to light, make to appear, and λόγος, which means study, discourse, or reasoning. The global change discussion has stimulated phenological research, which as a consequence greatly advanced as science and evolved to one of the main climate impact indicators. Many of the earliest systematic efforts to collect phenological observations took place in countries sharing the Alps, most of which are still operating phenological networks. These phenological data sets are generally freely available to researchers, and numerous essential contributions to the topic of phenology and climate have been built on those data sets. Plant physiological processes underlying the ability of the plants to adapt to the year-to-year variability of the climate still constitutes largely a black box. Since the experiments of René Antoine Ferchault de Reaumur in the 18th century, it is known that temperature constitutes the main environmental driver of the seasonal development of the mid- to high-latitude plants. Second to temperature, day length governs the seasonal cycle of some species as an additional factor. Therefore, temperature-driven phenological models are able to simulate the year-to-year variability of phenological entry dates accurately enough for various applications, such as climate change impact research or numerical pollen forecast models, where the beginning of flowering of some plants is linked with the release of allergic pollen into the atmosphere. Large-scale circulation patterns, like the North Atlantic Oscillation, determine the frequency and intensity of warm and cold spells and decadal temperature trends over Europe. Combined anthropogenic and natural forcings explain the advance of spring phenology over the last 50 years, which is also clearly discernible in the area of the Alps. The early phenological spring starts in Western Europe, whereas later in the season it makes progress with a stronger southerly component across the Alps. The combined temporal and spatial trends have been studied along elevational gradients. Trends toward earlier entry dates are stronger at higher elevations, which indicates that the elevational phenological gradient has weakened since the mid-20th century. Similarly, the vegetation response to temperature is observed to decrease when moving from high to low latitudes. In contrast, the temporal response of plant phenology to increasing temperatures is less clear. Some works indeed demonstrate a decreasing temperature sensitivity with increasing temperature, which is explained as a result of a reduced winter chilling that delays spring phenology or of a limiting effect due to a shorter photoperiod. Other works report no change of temporal temperature sensitivity with increasing temperatures. Indigenous midlatitude vegetation is able to withstand large temperature variations during winter and spring. The safety margin between last frost events, budding, and leaf emergence was found to be uniform across elevations and taxa, except for beech trees. The probability of freezing damage to natural vegetation is almost nil, but late frost risk constitutes a real threat to fruit growers. The ratio of phenological and last frost trends is ambiguous. An increase or decrease in frost risk depends on regions, elevations, and species. Vegetation at high altitudes is exposed to a harsh climate with a long-lasting snow cover, low temperatures, and a short growing season. Snowmelt is a necessary but insufficient requirement for the start of the growing season, which has to be supplemented by plant-specific temperature sums to activate the growth of most alpine and subalpine species. The seasonal cycle has to be completed within a short time. Advances in remote sensing technology have provided access to high-resolution landscape scale phenological information. Especially in remote areas, like the Alps, in situ observations could be supplemented by satellite observations. Observations from both methods, I -situ and remote sensing, have been applied to describe spring vegetation dynamics, but the correlation between these data sets have typically been weak because of differences in temporal and spatial scales and resolutions. A successfully combined description of the seasonal vegetation cycle is still lacking. The area of the European Alps offers a wealth of long chronicles, containing historical phenological observations some of which have been extracted and digitized. Grape harvest dates belong to the most readily available historical phenological observations, which have helped reconstruct summer temperatures as far back as the 15th century.

Article

The emergence of meteorology in Vietnam did not begin in 1898–1899, with the French installation of a central meteorological observatory in Phù Liễn, near Hải Phòng, and a network of meteorological stations across Indochina. Prior to the colonial time, the ethnic Vietnamese, as well as other ethnic groups such as the Cham, Muong, and Tay-Thai, developed their own knowledge of meteorological phenomena that functioned within their farming practices and cultural frameworks. While further research concerning traditional meteorological knowledge of minority groups in Vietnam is needed, substantial evidence allows a preliminary survey on the practices of the ethnic Vietnamese. Between 1000 and the 1850s, the Vietnamese expanded outwards from their original homeland in the lowlands of north and north-central Vietnam. They adopted the written language, thought systems, and technologies of imperial China, which predisposed them to an enduring Chinese-style meteorological ideology. The Vietnamese viewed weather extremes and other natural anomalies not merely as natural processes. Because meteorological phenomena were “Heaven-sent” warnings of cosmological disasters, Vietnamese dynastic rulers, as well as local farmers and rice producers, interpreted these signs as a demand for moral change. Redressing the authorities’ governance, according to their view, helped rehabilitate the equilibrium of the cosmos. Hence, the records of weather events in Vietnamese historical documents do not simply describe the conditions of past weather, but more importantly, the situations in which the cosmos was no longer in balance. One need not assume that premodern meteorology lacked material grounds. In Vietnam, meteorological knowledge and practices were strongly associated with wet rice cultivation. Vietnamese authorities maintained official agencies to produce yearly calendars that traced proper timing for rice crops, while the populace accumulated experience-based knowledge about seasonal rainfall. Intellectuals, too, expanded their interests to include meteorological knowledge because the subject enriched their philosophy of nature, as in the case of Confucian thinker Lê Quý Đôn (1726–1784), or their medical practices, as in the case of physician Lê Hữu Trác (1720–1791). The advances of Southeast Asian paleoclimate reconstruction since the beginning of the 21st century have added new ideas and methodologies to the study of premodern meteorology in Vietnam. A stronger partnership between climate scientists and historians will therefore facilitate more sophisticated investigations into the knowledge and practices that the Vietnamese developed to respond to weather and climate dynamics.