Winter annual vegetation following a nuclear detonation in the northern mojave desert (Nevada test site)

• Published in: Radiation botany 1966-01, Vol.6 (1), p.69-82
• Main Author: Beatley, Janice C.
• Format: Article
• Language: English
• ISSN: 0033-7560
• DOI: 10.1016/S0033-7560(66)80093-5

Winter annual vegetation and environmental phenomena were observed and measured through the growing seasons of 1962–65, on 3 sites in north-eastern Yucca Flat within 2 miles of the “Sedan” underground thermonuclear detonation in July 1962. Cumulative γ-radiation recorded was of the magnitude of 4000–13,000 R. As a result of the regional precipitation regime in the autumn of 1962, there were no winter annuals present in the Sedan area, or in most other parts of the Test Site, during the growing season 1962–63. Seedlings of the first post Sedan populations, which appeared following September 1963 rains, were the largest and most vigourous of populations observed in any region of the Test Site. The exceptional size and vigour continued through the period of anthesis in May 1964, and were corroborated by measurements of average height, cover, biomass and survival of the spring populations, as compared with those on seven other sites in central and northern Yucca Flat. In the next generation, which germinated in the spring of 1965 following record precipitation (4–5 in.), there was neither higher survival of the Sedan populations nor exceptional development at any stage during the several-week growing season. The unusual vigour of the winter annual populations in the 1963–64 season is inferred to have been in part a “stimulatory” effect of the ionizing radiation to which the embryos in the seeds were exposed from July 1962 until time of germination in September 1963. Abnormal morphological development of frequent individuals of Chaenactis stevioides, the dominant winter annual on the Sedan sites, may also have been an effect of seed irradiation. On a observé la végétation annuelle d'hiver et mesuré les modifications du milieu, au cours des saisons 1962–65, en 3 zones du nord-est de la plaine du Yucca, à moins de deux miles de l'explosion thermonucléaire souterraine “Sedan” de juillet 1962. L'irradiation gamma totale enregistrée était de l'ordre de 4000 à 13,000 R. A la suite du régime régional des précipitations de l'automne 1962, on n'a pas rencontré de plantes annuelles d'hiver dans la zone Sedan, ni dans la plupart des autres zones de la région analysée durant la saison 1962–63. Les plantules des premières populations consécutives à l'explosion, apparues après les pluies de septembre 1963, ont été les plus grandes et les plus vigoureuses des populations observées dans l'ensemble de la région analysée. Cette taille, cette vigueur exceptionnelle s'est maintenu