中国科学院西部行动计划资助项目(KZCX2-XB2-01)；国家自然科学基金面上资助项目(30570281, 30872074)；国家科技基础条件平台建设子资助项目(2005DKA21006)；中国博士后科学基金资助项目(20080430589)；郑州市科技攻关资助项目(064SGDN19194-2, 074SCCG36112-2)
Bromus inermis Leyss. is a dominant rhizomatous grass in the Otindag Sandland of North China, where the environment is heterogeneous, and non-saline, low-saline, and high-saline patches form a mosaic of habitats. Ramets of B. inermis simultaneously inhabit many patches at different salinity levels. We hypothesized that clonal fragments in high- saline patches benefit from clonal integration. A factorial greenhouse pot experiment with salinity and rhizome- severing as main effects was conducted in which each clonal fragment consisted of two interconnected ramets. In one treatment, the proximal part of the clonal fragment received a salt treatment (300 mmol/L NaCl solution), and in another treatment the distal part received a salt treatment. Rhizome connections between neighboring ramets were severed or left intact. Rhizome severing dramatically decreased survival of salt-treated ramets. A cost-benefit analysis based on biomass production, number of shoots, number of rhizome nodes, and total rhizome length showed that untreated ramets supported connected ramets treated with salt by clonal integration but did not incur any cost from resource export. We speculate that clonal integration may be an important adaptation of B. inermis to heterogeneous saline environments that increases its growth and survival, and thus fitness, in semiarid sandy lands.