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Effects of Drought, Pest Pressure and Light Availability on Seedling Establishment and Growth: Their Role for Distribution of Tree Species across a Tropical Rainfall Gradient.

Gaviria J, Engelbrecht BM - PLoS ONE (2015)

Bottom Line: Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests.Establishment success after one year did not reflect species distribution patterns.Together these processes sort species over longer time frames, and exclude species outside their respective home range.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Ecology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany.

ABSTRACT
Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis), high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively). To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of light and pests are less important.

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Related in: MedlinePlus

Gravimetric soil moisture (A) and canopy openness (B) in the dry and wet site across seasons.Colors indicate the end of the dry season 2012 (red), wet season 2012 (blue) and dry season 2013 (dark red). Included are results of an ANOVA for effects of site, season and site x season interactions. Different letters represent significant differences at the 0.05 level in a Tukey post-hoc test. Presented are means (thick horizontal lines), 95% CI (thin lines), and raw data (points).
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pone.0143955.g002: Gravimetric soil moisture (A) and canopy openness (B) in the dry and wet site across seasons.Colors indicate the end of the dry season 2012 (red), wet season 2012 (blue) and dry season 2013 (dark red). Included are results of an ANOVA for effects of site, season and site x season interactions. Different letters represent significant differences at the 0.05 level in a Tukey post-hoc test. Presented are means (thick horizontal lines), 95% CI (thin lines), and raw data (points).

Mentions: We recorded gravimetric soil moisture at each census, and averaged over the dry and wet seasons, respectively. For light availability, canopy openness was assessed once during the dry and wet season, respectively (Fig 2).


Effects of Drought, Pest Pressure and Light Availability on Seedling Establishment and Growth: Their Role for Distribution of Tree Species across a Tropical Rainfall Gradient.

Gaviria J, Engelbrecht BM - PLoS ONE (2015)

Gravimetric soil moisture (A) and canopy openness (B) in the dry and wet site across seasons.Colors indicate the end of the dry season 2012 (red), wet season 2012 (blue) and dry season 2013 (dark red). Included are results of an ANOVA for effects of site, season and site x season interactions. Different letters represent significant differences at the 0.05 level in a Tukey post-hoc test. Presented are means (thick horizontal lines), 95% CI (thin lines), and raw data (points).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664389&req=5

pone.0143955.g002: Gravimetric soil moisture (A) and canopy openness (B) in the dry and wet site across seasons.Colors indicate the end of the dry season 2012 (red), wet season 2012 (blue) and dry season 2013 (dark red). Included are results of an ANOVA for effects of site, season and site x season interactions. Different letters represent significant differences at the 0.05 level in a Tukey post-hoc test. Presented are means (thick horizontal lines), 95% CI (thin lines), and raw data (points).
Mentions: We recorded gravimetric soil moisture at each census, and averaged over the dry and wet seasons, respectively. For light availability, canopy openness was assessed once during the dry and wet season, respectively (Fig 2).

Bottom Line: Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests.Establishment success after one year did not reflect species distribution patterns.Together these processes sort species over longer time frames, and exclude species outside their respective home range.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Ecology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany.

ABSTRACT
Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis), high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively). To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of light and pests are less important.

Show MeSH
Related in: MedlinePlus