Indirect facilitation becomes stronger with seedling age in a degraded seasonally dry forest.

TORRES, R. C.; RENISON, D.

ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY

GAUTHIER-VILLARS/EDITIONS ELSEVIER

Lugar: Paris; Año: 2016 vol. 70 p. 138 - 143

1146-609X

In seasonally dry forests direct facilitation by woodyspecies due to amelioration of harsh abiotic conditions could be important during germination and earlyestablishment of tree seedlings, and under some species but not others. Recentresearch suggests that at later stages facilitation by woody species may be indirectdue to protection of saplings from herbivores, implying that under absence ofherbivores reforestation programs may plant saplings in unprotected open sites.We used the native tree Lithraea molleoides from central Argentina as a model species to testthis hypothesis. We performed a seeding and planting experiment simulatingearly and late establishment respectively, which included 234 study plotssituated in herbaceous, shrub and tree patches ofdiffering species composition and under two herbivore treatments (grazed andungrazed) and replicated at three sites. Seedling counts averaged 0.82% of the sown seeds after6 months, were highest under shrubs and lowest in open patches, and wereinfluenced by woody species composition only in tree patches (all P values<0.05).At seedling stages we detected no influence of herbivory (P=0.4) nor of indirectfacilitation due to herbivory (herbivory×patch type P=0.7). Survival of plantedsaplings was 53% after 3 years and over winter dieback affected 76% of thesaplings. At saplingstages we found an increasing importance of indirect facilitation throughprotection from herbivores, as we recorded the highest saplingsurvival and growth at tree and shrub patches and the lowest in open patches(all P values<0.001), and a negative effect of livestock (P<0.001) mainlyon the open patches (herbivory×patch type P=0.07 and P=0.001 for survival andgrowth, respectively). We found nosignificant influence of woody species composition on sapling survival andgrowth (all P values>0.05). We conclude that direct facilitation is involved at allstudied stages while indirect facilitation becomes increasingly important atthe sapling stage.