Canadian Forest Service Publications

Nitrogen translocation between clonal mother and daughter trees at a grassland-forest boundary. 2014. Pinno, B.D.; Wilson, S.D. Plant Ecology 215(3):347-354.

Year: 2014

Issued by: Northern Forestry Centre

Catalog ID: 35398

Language: English

Availability: Order paper copy (free), PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1007/s11258-014-0305-3

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There is abundant evidence from short-term experiments using herbs that nutrients can be translocated from mother ramets to daughter ramets, but there is little long-term evidence from woody plants. Here, we examine translocation in field populations of a clonal tree over two growing seasons. We applied 15N to mothers or daughters in clones of Populus tremuloides at the northern edge of the North American Great Plains, where mother ramets form closed-canopy stands on relatively nutrient-rich soils, and daughter ramets occur nearby in relatively nutrient-poor grasslands. Unlabeled daughters in clones with labeled mothers had δ15N values significantly greater than those in unlabeled clones, confirming translocation from mothers to daughters. However, unlabeled mothers in clones with labeled daughters also had δ15N values significantly greater than those in unlabeled clones, indicating translocation from daughters to mothers. Further, the total foliage accumulation of added 15N was significantly (c. 10x) greater in mothers than in daughters, suggesting that more N was translocated from daughters to mothers, than from mothers to daughters. Thus, 15N moved both from mothers to daughters and from daughters to mothers, with net flow toward mothers. Because long-lived woody ramets in the field face nutrient competition from other ramets, interspecific neighbors, and soil microbes, the environmental availability of nutrients for uptake may be low for both mother and daughter ramets, causing translocation within a clone to be toward larger ramets with greater demand.

Plain Language Summary

Some plants spread through shared root systems rather than, or in addition to, spreading by seeds. Such interconnected plants share nutrients, water, and energy. This sharing has been studied to date only in herbaceous (or non-woody) plants in greenhouses, rather than in woody plants in natural settings. One of the trees that spreads by root systems is trembling aspen. We studied how aspen share a key nutrient, nitrogen, in the aspen parkland ecoregion near Regina, Saskatchewan, where large “mother” trees form forest stands and smaller “daughter” trees grow in the surrounding grassland. Analysis of nitrogen isotopes showed nitrogen transfer in both directions: from mothers to daughters, and from daughters to mothers. Overall, more nitrogen flowed towards the larger mother trees. These results suggest that nutrients may be moving across ecosystem boundaries, from grassland to forest, through the root systems of trembling aspen. This information helps us to understand basic ecological aspects of how aspen forests grow and obtain nutrients.