Aerial and soil seed banks enable populations of an annual species to cope with an unpredictable dune ecosystem

Ruiru Gao1,2, Xuejun Yang1, Fan Yang1,2, Lingling Wei1, Zhenying Huang1,* and Jeffrey L.Walck3

1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China, 2University of Chinese Academy of Sciences, Beijing 100049, China and 3Evolution and Ecology Group, Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132, USA * For correspondence. E-mail zhenying@ibcas.ac.cn

气生与土壤种子库促进了一种一年生植物对荒漠沙丘环境的适应性

同时形成气生和土壤种子库是一些植物在不可预测生境中的种群维持机制。但我们对于这两种种子库在沙丘环境中植物种群动态中的作用还不了解。我们对鄂尔多斯沙地中荒漠植物沙米的种子传播、萌发、幼苗出土和存活进行了研究,以确定两种种子库的不同作用。我们发现,在整个生长季节中,气生种子库都高于土壤种子库的数量,种子传播与风速有正相关关系。与土壤种子库相比,气生种子库的种子在低温下的萌发率较低,但在光照条件下较高。早出土的幼苗(4月15日-5月15日)因出现霜冻而死亡,但晚一个月出土的幼苗存活至成功繁殖。因此,种子传播时间不同以及两种种子库之间的不同萌发特性为幼苗出土和建成创造了不同的时机,因而成功适应不可预测的生境。

Abstract
BACKGROUND AND AIMS:
Simultaneous formation of aerial and soil seed banks by a species provides a mechanism for population maintenance in unpredictable environments. Eolian activity greatly affects growth and regeneration of plants in a sand dune system, but we know little about the difference in the contributions of these two seed banks to population dynamics in sand dunes.
METHODS:
Seed release, germination, seedling emergence and survival of a desert annual, Agriophyllum squarrosum (Chenopodiaceae), inhabiting the Ordos Sandland in China, were determined in order to explore the different functions of the aerial and soil seed banks.
KEY RESULTS:
The size of the aerial seed bank was higher than that of the soil seed bank throughout the growing season. Seed release was positively related to wind velocity. Compared with the soil seed bank, seed germination from the aerial seed bank was lower at low temperature (5/15 °C night/day) but higher in the light. Seedling emergence from the soil seed bank was earlier than that from the aerial seed bank. Early-emerged (15 April-15 May) seedlings died due to frost, but seedlings that emerged during the following months survived to reproduce successfully.
CONCLUSIONS:
The timing of seed release and different germination behaviour resulted in a temporal heterogeneity of seedling emergence and establishment between the two seed banks. The study suggests that a bet-hedging strategy for the two seed banks enables A. squarrosum populations to cope successfully with the unpredictable desert environment.