Effects of rainfall pattern on the growth and fecundity of a dominant dune annual in a semi-arid ecosystem

Ruiru Gao, Xuejun Yang, Guofang Liu, Zhenying Huang, Jeffrey L. Walck

当前与未来降水格局的变化对半干旱生态系统中一年生植物有重要作用。我们研究了降水格局的变化对沙丘一年生植物生长和繁殖的影响。以历史和预测的5种降水数量和频度为梯度，测定了降水对毛乌素沙地一年生植物沙蓬生长和繁殖的影响。我们发现，降水数量和频度对所有生长和繁殖性状都有显著作用。随着降水数量的减少，植株高度、生物量、种子数量和繁殖成效下降，而根茎比上升。除了两个极端情况（1和120天间隔），所有生长和繁殖性状随着降水频度的增加而增加。子代萌发率随着干旱程度的增加而增加，可能存在母体效应。因此，沙蓬生长与繁殖对降水的可塑性对植物在半干旱的不可预测的环境中存活具有重要作用。

Abstract

Aims: Current and future changes in rainfall patterns – amount and frequency – may particularly impact annual plants in semi-arid ecosystems. The aim of this study was to investigate how changes in rainfall patterns affect the growth and fecundity of sand dune annuals.
Methods: The effects of gradients in five rainfall amounts and five frequencies, based on historical and predicted values, on growth and fecundity of Agriophyllum squarrosum, a dominant annual in Mu Us Sandland, were examined in the near natural habitat.
Results: Rainfall amount and frequency significantly affected all vegetative and reproductive traits. With decreased amount of rainfall, height, biomass, seed number, seed mass and reproductive effort decreased, while root/shoot ratio increased. Except for the two extreme frequencies (1- and 120-day intervals), values of all vegetative and reproductive traits increased with the increase of rainfall frequencies. Germinability of offspring seeds tended to increase with increasing aridity, suggesting that a maternal effect may have been present.
Conclusions: Our study shows that the plastic response in growth and fecundity of A. squarrosum to rainfall fluctuation allows the plant to survive and reproduce under current unpredictable environments as well as the increased variability predicted with climate change in semi-arid regions.