干旱区生态环境知识资源中心

We investigated whether seedling establishment in two alpine plants in Colorado was enhanced through maternally mediated nurse effects. To benefit from an association with maternal debris, seeds must remain with the debris, resulting in reduced risks to seedlings and enhancement of establishment success. Seedlings of Frasera speciosa (Gentianaceae) and Cirsium scopulorum (Asteraceae) were disproportionately abundant under decaying adult rosettes and infructescences relative to other microsites equidistant from the parent. Beneath decaying infructescences of both species, soil was significantly moister, and evaporation rates from hydrometers that mimicked young seedlings were significantly lower than in exposed (control) microsites. For F. speciosa, mean water potential of seedlings planted under infructescences was also significantly higher than that of seedlings planted into exposed plots. These data suggest that drought stress is reduced for seedlings associated with adult debris. In two populations of F. speciosa, adult cover had significant positive effects on seedling establishment in 1995. These advantages were mediated through enhanced survival of young seedlings, rather than emergence success. Cover enhanced seedling survival by 80% in one population and 145% in the other. In one population of C. scopulorum, no seedlings were established from seeds planted with or without debris in 1994 (an extremely dry year). However, in 1995 (a wetter year), seedlings were seven times more likely to emerge and about four times more likely to survive in association with debris than in exposed plots. These results show that associations with adult debris enhance offspring establishment success in both plant species, and provide one of the first demonstrations of conspecific nursing, a form of parental care, in plants.