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Title: Differential responses of C 3 and C 4 grasses to shrub effects in a sub‐humid grassland of South America
Abstract Questions

Plant–plant interactions are key processes that strongly affect the survival, growth and reproduction of individuals in plant communities. In grasslands, the micro‐environment generated under the canopy of shrubs could differentially affect co‐occurring species with different abiotic requirements. In a C3/C4grassland with scattered shrubs, we asked the following questions: (a) Does the aerial effect, the below‐ground effect, and the net effect of shrubs affect the vegetative and reproductive biomass, the number of tillers, the biomass allocation, and the leaf elongation rate of grasses? and (b) Do these effects differ between C3and C4grasses?

Location

Temperate sub‐humid grassland of Uruguay.

Methods

We planted one C3and two C4grasses under a shrub canopy and in adjacent open sites. Half of the grasses were planted with a fabric bag to reduce root competition with the shrub. We measured leaf elongation rate, the number of tillers produced and the biomass of the grasses in every treatment. We also measured photosynthetic photon flux density (PPFD), air temperature and wind speed under shrub canopies and in adjacent open sites.

Results

Root biomass, aerial biomass and reproductive biomass, the number of tillers and the leaf elongation rate of the C4grasses were negatively affected by the reduction in radiation and probably by below‐ground competition with the shrub. On the other hand, the leaf elongation rate of the C3grasses was positively affected by the shrub canopy.PPFD, air temperature and wind speed were lower under shrubs than in adjacent open sites.

Conclusions

Our results show the interplay between plant interactions and photosynthetic metabolism on the vegetative and reproductive performance of grasses. The micro‐environmental conditions generated below shrub canopies create a more appropriate site for the growth of C3than for C4grasses. These results show that shrubs may differentially affect co‐occurring species with different abiotic requirements.

 
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NSF-PAR ID:
10461592
Author(s) / Creator(s):
 ;  ;
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Journal of Vegetation Science
Volume:
30
Issue:
2
ISSN:
1100-9233
Page Range / eLocation ID:
p. 203-211
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  4. Abstract

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  5. Abstract Aims

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    Methods

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    Results

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    Conclusions

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