Conspecific leaf litter and root competition inhibits shrub emergence in the Patagonian steppe
A critical stage in the establishment of new individuals is seedling emergence and litter is a main factor affecting this stage. Recent research found that adults of Chuquiraga avellanedae are over-dispersed. Among several mechanisms, this pattern might be due to the negative influences of adults on seedlings through root competition. We performed field and glasshouse experiments to evaluate (i) the effects of C. avellanedae leaf litter and root presence on the emergence of conspecific seedlings, and (ii) the effects of leaf litter type (C. avellanedae litter, inert litter, no litter) and seed burial depth (seed at the surface or buried) on the emergence of C. avellanedae and Nassella tenuis (dominant grass) seedlings. The field experiment demonstrated root competition from adult plants on shrub seedlings, reducing seedling emergence. However, the effect of root competition did not differ between microsites (under-shrubs vs. between-shrubs). We dismiss the effect of allelopathy because inert litter (i.e., plastic leaves) had the same negative effect as C. avellanedae litter, indicating a mechanical effect. The glasshouse experiment revealed a species-specific response of seedling emergence. C. avellanedae litter limits the emergence of conspecific seedlings but was neutral with regard to the emergence of grass seedlings (N. tenuis). No differences in root competition between microsites and reduction of shrub seedlings by litter suggest that the over-dispersed pattern found for C. avellanedae is caused, at least partially, by litter effects on seedling emergence.
KeywordsShrub leaf litter Seedling emergence Root competition Grass-shrub steppes Over-dispersed distribution Microsite
We are especially grateful to Lina Videla and Cristian Barrionuevo for their assistance during field and laboratory work. Anonymous reviewers and Michael John Lawes provided thoughtful comments on the manuscript. Ana Casalini and Gustavo Pazos helped with data analysis. This work was supported by the National Research Council of Argentina CONICET (PIP 11220170100981). This paper was written within the framework of the PUE-IPEEC-2016 22920160100044. MVC and AJB are CONICET researchers.
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