Does the phytotoxic shrub Heterothalamus psiadioides affect a plant community through allelopathy?

• Published in: Plant ecology Vol. 216; no. 1; pp. 87 - 97
• Main Authors: da Silva, Eliane R, Ferreira, Pedro M. A, Overbeck, Gerhard E, Soares, Geraldo L. G
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer-Verlag 01.01.2015; Springer; Springer Netherlands; Springer Nature B.V
• Subjects: Allelopathy; Applied Ecology; Baccharis; Biodiversity; biomass; Biomedical and Life Sciences; Community & Population Ecology; Ecology; forbs; grasses; Grasslands; Life Sciences; Phytotoxicity; Plant communities; Plant Ecology; Plant populations; Plant species; Plants; Seedlings; shrublands; Shrubs; Terrestial Ecology; Trees; Vegetation patterns; Grassland; Shrubland; Campos sulinos; Plant volatiles; Diversity; Allelopathic potential
• ISSN: 1385-0237; 1573-5052
• DOI: 10.1007/s11258-014-0418-8

Phytotoxicity has often been proposed as evidence of allelopathy. However, few studies have investigated allelopathy in natural field conditions. In South Brazilian grasslands, Heterothalamus psiadioides, a shrub establishing in dense stands, has shown strong phytotoxicity in laboratory assays. We conducted a field study to evaluate if this species also negatively affects a plant community through allelopathy. At a shrubland site, we established a phytotoxicity gradient, consisting of plots with H. psiadioides, plots with Baccharis patens—a shrub with minimal phytotoxicity—and plots without shrubs (no phytotoxicity). We assessed plant species cover, biomass, number of seedlings, diversity, richness, and plant community characteristics. Our study did not show evidences of plant inhibition near the phytotoxic species. We observed higher plant richness and diversity in plots with H. psiadioides than in plots with B. patens and without shrubs. The highest diversity near H. psiadioides was associated with greater forb cover, due to lower cover of dominant grasses. Differences in light incidence accounted for vegetation patterns more than allelopathic activity. Therefore, our study showed that the allelopathic potential of the evaluated species was overestimated based only on laboratory studies. We emphasize the relevance of conducting allelopathy studies in field and of having a similar species with low phytotoxicity in this kind of study. Results based only on laboratory assays and visual evidence of patterns in field may be misleading and may lead to an overestimation of the role of allelopathy in plant communities.