关键词: 群落外貌, 种的数量特征, 优势种, 频度, 多样性, 水热因子

Abstract

Ephemerals, including annual ephemerals and ephemeroid plants, are characterized by short-term growth rhythms and specific biological traits adapted to deserts or temperate broad-leaved deciduous forests. Few studies have been carried out on ephemeral community composition and their relationships with temperature and precipitation regimes in the desert. Between 2005 and 2008, we monitored early-spring ephemeral communities in 201 quadrats along 25 line transects in the Mosuowan area of the Dzungaria Desert, northern Xinjiang where ephemerals represent a special desert floral group. We also collected temperature and precipitation data to analyze the effects of these factors on ephemeral adaptation. We found that ephemerals dominated the plant community in early spring, accounting for 52% of species observed. Six of seven species with a frequency over 40% were ephemerals, they were Eremopyrum orientale,Malcolmia scorpioides,Arnebia decumbens, Lappula semiglabra, Tetracme quadricornis andAtriplex dimorphostegia. Abundance of ephemerals has closely negatively relationship with the winter temperature in the previous year, suggesting that low temperature in the previous winter facilitates sprouting of ephemerals in the current year. However, community structure depended more on temperature and precipitation in early spring in the current year than the previous year. Annual changes in Shannon-Wiener and Pielou indices of these communities were consistent with annual changes in total amount of spring and winter precipitation. Therefore, variation in temperature and precipitation regimes is likely the main factor involved with inter-year changes in the structure of ephemeral plant communities in the Dzungaria Desert, Xinjiang.

Key words: physiognomy, species quantitative traits, dominant species, frequency, diversity, hydro-thermic factors, Dzungaria desert