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The effects of drought and shade on the performance, morphology and physiology of Ghanaian tree species.

Amissah L, Mohren GM, Kyereh B, Poorter L - PLoS ONE (2015)

Bottom Line: One central question is whether drought and shade have interactive effects on seedling growth and survival.When individual species responses were analysed, then for most of the traits only one to three species showed significant interactive effects between drought and shade.Overall our greenhouse results suggest that, in the absence of root competition shaded tropical forest tree seedlings may be able to survive prolonged drought.

View Article: PubMed Central - PubMed

Affiliation: Council for Scientific and Industrial Research-Forestry Research Institute of Ghana, KNUST, Kumasi, Ghana; Forest Ecology and Forest Management Group, Wageningen University, Wageningen, The Netherlands.

ABSTRACT
In tropical forests light and water availability are the most important factors for seedling growth and survival but an increasing frequency of drought may affect tree regeneration. One central question is whether drought and shade have interactive effects on seedling growth and survival. Here, we present results of a greenhouse experiment, in which seedlings of 10 Ghanaian tree species were exposed to combinations of strong seasonal drought (continuous watering versus withholding water for nine weeks) and shade (5% irradiance versus 20% irradiance). We evaluated the effects of drought and shade on seedling survival and growth and plasticity of 11 underlying traits related to biomass allocation, morphology and physiology. Seedling survival under dry conditions was higher in shade than in high light, thus providing support for the "facilitation hypothesis" that shade enhances plant performance through improved microclimatic conditions, and rejecting the trade-off hypothesis that drought should have stronger impact in shade because of reduced root investment. Shaded plants had low biomass fraction in roots, in line with the trade-off hypothesis, but they compensated for this with a higher specific root length (i.e., root length per unit root mass), resulting in a similar root length per plant mass and, hence, similar water uptake capacity as high-light plants. The majority (60%) of traits studied responded independently to drought and shade, indicating that within species shade- and drought tolerances are not in trade-off, but largely uncoupled. When individual species responses were analysed, then for most of the traits only one to three species showed significant interactive effects between drought and shade. The uncoupled response of most species to drought and shade should provide ample opportunity for niche differentiation and species coexistence under a range of water and light conditions. Overall our greenhouse results suggest that, in the absence of root competition shaded tropical forest tree seedlings may be able to survive prolonged drought.

No MeSH data available.


Related in: MedlinePlus

Performance of Ghanaian tree seedlings in terms of (a) survival and (b) relative biomass growth rate (RGR) in response to drought and shade.Shade treatments consisted of low light (5% of full sunlight, black bars) and high light (20% of full sunlight, grey bars). The water treatment consisted of a wet treatment (plants continuously watered for nine weeks) and dry treatment (water was withheld from seedlings for nine weeks). Means and standard error of the means are shown. Bars accompanied by a different letter are significantly different at P < 0.05 (ANOVA, Post hoc LSD test). n = 10 species.
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pone.0121004.g001: Performance of Ghanaian tree seedlings in terms of (a) survival and (b) relative biomass growth rate (RGR) in response to drought and shade.Shade treatments consisted of low light (5% of full sunlight, black bars) and high light (20% of full sunlight, grey bars). The water treatment consisted of a wet treatment (plants continuously watered for nine weeks) and dry treatment (water was withheld from seedlings for nine weeks). Means and standard error of the means are shown. Bars accompanied by a different letter are significantly different at P < 0.05 (ANOVA, Post hoc LSD test). n = 10 species.

Mentions: Drought led to a decrease in survival compared to the continuously watered plant in both shade (89% drought survival versus 100% for continuously watered plants) and light (53% drought survival versus 99.6% for continuously watered plants). No statistical test was carried out to test the difference in survival in the watered plants because survival was 100% in the 5% irradiance greenhouse and 99.6% in the 20% irradiance greenhouse. There was a significant difference between drought survival in the shade (5% irradiance) and drought survival in the high light (20% irradiance) in the dry treatment (Mann-Whitney U = 10.5, Z = -2.99, P < 0.01). Drought survival in high light was 1.7 fold lower than in shade, indicating that plants are hit harder by drought in exposed environments that are typical of gaps (Fig 1A). Both drought and shade led to a decrease in relative biomass growth rate (Three-way ANOVA, drought, P ≤ 0.001; shade P ≤ 0.001; Fig 1B). There was a significant interaction effect (P ≤ 0.001) of light and water on relative growth rate, indicating that the effect of drought depended on the light level under which plants were growing. Drought reduced relative growth rate more strongly under high light than in low light.


The effects of drought and shade on the performance, morphology and physiology of Ghanaian tree species.

Amissah L, Mohren GM, Kyereh B, Poorter L - PLoS ONE (2015)

Performance of Ghanaian tree seedlings in terms of (a) survival and (b) relative biomass growth rate (RGR) in response to drought and shade.Shade treatments consisted of low light (5% of full sunlight, black bars) and high light (20% of full sunlight, grey bars). The water treatment consisted of a wet treatment (plants continuously watered for nine weeks) and dry treatment (water was withheld from seedlings for nine weeks). Means and standard error of the means are shown. Bars accompanied by a different letter are significantly different at P < 0.05 (ANOVA, Post hoc LSD test). n = 10 species.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383566&req=5

pone.0121004.g001: Performance of Ghanaian tree seedlings in terms of (a) survival and (b) relative biomass growth rate (RGR) in response to drought and shade.Shade treatments consisted of low light (5% of full sunlight, black bars) and high light (20% of full sunlight, grey bars). The water treatment consisted of a wet treatment (plants continuously watered for nine weeks) and dry treatment (water was withheld from seedlings for nine weeks). Means and standard error of the means are shown. Bars accompanied by a different letter are significantly different at P < 0.05 (ANOVA, Post hoc LSD test). n = 10 species.
Mentions: Drought led to a decrease in survival compared to the continuously watered plant in both shade (89% drought survival versus 100% for continuously watered plants) and light (53% drought survival versus 99.6% for continuously watered plants). No statistical test was carried out to test the difference in survival in the watered plants because survival was 100% in the 5% irradiance greenhouse and 99.6% in the 20% irradiance greenhouse. There was a significant difference between drought survival in the shade (5% irradiance) and drought survival in the high light (20% irradiance) in the dry treatment (Mann-Whitney U = 10.5, Z = -2.99, P < 0.01). Drought survival in high light was 1.7 fold lower than in shade, indicating that plants are hit harder by drought in exposed environments that are typical of gaps (Fig 1A). Both drought and shade led to a decrease in relative biomass growth rate (Three-way ANOVA, drought, P ≤ 0.001; shade P ≤ 0.001; Fig 1B). There was a significant interaction effect (P ≤ 0.001) of light and water on relative growth rate, indicating that the effect of drought depended on the light level under which plants were growing. Drought reduced relative growth rate more strongly under high light than in low light.

Bottom Line: One central question is whether drought and shade have interactive effects on seedling growth and survival.When individual species responses were analysed, then for most of the traits only one to three species showed significant interactive effects between drought and shade.Overall our greenhouse results suggest that, in the absence of root competition shaded tropical forest tree seedlings may be able to survive prolonged drought.

View Article: PubMed Central - PubMed

Affiliation: Council for Scientific and Industrial Research-Forestry Research Institute of Ghana, KNUST, Kumasi, Ghana; Forest Ecology and Forest Management Group, Wageningen University, Wageningen, The Netherlands.

ABSTRACT
In tropical forests light and water availability are the most important factors for seedling growth and survival but an increasing frequency of drought may affect tree regeneration. One central question is whether drought and shade have interactive effects on seedling growth and survival. Here, we present results of a greenhouse experiment, in which seedlings of 10 Ghanaian tree species were exposed to combinations of strong seasonal drought (continuous watering versus withholding water for nine weeks) and shade (5% irradiance versus 20% irradiance). We evaluated the effects of drought and shade on seedling survival and growth and plasticity of 11 underlying traits related to biomass allocation, morphology and physiology. Seedling survival under dry conditions was higher in shade than in high light, thus providing support for the "facilitation hypothesis" that shade enhances plant performance through improved microclimatic conditions, and rejecting the trade-off hypothesis that drought should have stronger impact in shade because of reduced root investment. Shaded plants had low biomass fraction in roots, in line with the trade-off hypothesis, but they compensated for this with a higher specific root length (i.e., root length per unit root mass), resulting in a similar root length per plant mass and, hence, similar water uptake capacity as high-light plants. The majority (60%) of traits studied responded independently to drought and shade, indicating that within species shade- and drought tolerances are not in trade-off, but largely uncoupled. When individual species responses were analysed, then for most of the traits only one to three species showed significant interactive effects between drought and shade. The uncoupled response of most species to drought and shade should provide ample opportunity for niche differentiation and species coexistence under a range of water and light conditions. Overall our greenhouse results suggest that, in the absence of root competition shaded tropical forest tree seedlings may be able to survive prolonged drought.

No MeSH data available.


Related in: MedlinePlus