Limits...
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

Relationship between survival under stressful conditions (drought and high light) and (a) mean plasticity of nine traits, (b) Leaf mass fraction (LMF) plasticity.Relationship between relative growth rate under optimal conditions (continuous watering and 20% of full sunlight) and (c) mean plasticity and (d) root mass fraction plasticity. Plasticity for each trait was calculated as maximum minus minimum mean trait values divided by maximum mean trait values across four treatment combinations. For each species, mean plasticity was calculated as the average plasticity of 9 traits. Regression line and coefficient of determination are shown. Ns = not significant, * = p ≤ 0.05, ** = p ≤ 0.01, n = 10 species.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4383566&req=5

pone.0121004.g004: Relationship between survival under stressful conditions (drought and high light) and (a) mean plasticity of nine traits, (b) Leaf mass fraction (LMF) plasticity.Relationship between relative growth rate under optimal conditions (continuous watering and 20% of full sunlight) and (c) mean plasticity and (d) root mass fraction plasticity. Plasticity for each trait was calculated as maximum minus minimum mean trait values divided by maximum mean trait values across four treatment combinations. For each species, mean plasticity was calculated as the average plasticity of 9 traits. Regression line and coefficient of determination are shown. Ns = not significant, * = p ≤ 0.05, ** = p ≤ 0.01, n = 10 species.

Mentions: To evaluate whether trait plasticity was associated with seedling performance correlations were tested between mean plasticity (mean plasticity across nine traits) and RGR under optimal conditions (wet treatment in 20% light), between mean plasticity and survival under stressed condition (dry treatment in 20% light) and between plasticity in RGR and survival. RGR under optimal conditions was only significantly correlated with plasticity in RMF (r = 0.81, P ≤ 0.01; Table 4, Fig 4D). Survival under stressful conditions was only significantly and positively correlated with plasticity in leaf mass fraction (Fig 4B, r = 0.74, P = 0.014). Plasticity in survival was significantly negatively related to plasticity in leaf mass fraction (r = -0.71, P = 0.023). Plasticity in RGR was not significantly related to plasticity of any of the traits (Table 4).


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)

Relationship between survival under stressful conditions (drought and high light) and (a) mean plasticity of nine traits, (b) Leaf mass fraction (LMF) plasticity.Relationship between relative growth rate under optimal conditions (continuous watering and 20% of full sunlight) and (c) mean plasticity and (d) root mass fraction plasticity. Plasticity for each trait was calculated as maximum minus minimum mean trait values divided by maximum mean trait values across four treatment combinations. For each species, mean plasticity was calculated as the average plasticity of 9 traits. Regression line and coefficient of determination are shown. Ns = not significant, * = p ≤ 0.05, ** = p ≤ 0.01, n = 10 species.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0121004.g004: Relationship between survival under stressful conditions (drought and high light) and (a) mean plasticity of nine traits, (b) Leaf mass fraction (LMF) plasticity.Relationship between relative growth rate under optimal conditions (continuous watering and 20% of full sunlight) and (c) mean plasticity and (d) root mass fraction plasticity. Plasticity for each trait was calculated as maximum minus minimum mean trait values divided by maximum mean trait values across four treatment combinations. For each species, mean plasticity was calculated as the average plasticity of 9 traits. Regression line and coefficient of determination are shown. Ns = not significant, * = p ≤ 0.05, ** = p ≤ 0.01, n = 10 species.
Mentions: To evaluate whether trait plasticity was associated with seedling performance correlations were tested between mean plasticity (mean plasticity across nine traits) and RGR under optimal conditions (wet treatment in 20% light), between mean plasticity and survival under stressed condition (dry treatment in 20% light) and between plasticity in RGR and survival. RGR under optimal conditions was only significantly correlated with plasticity in RMF (r = 0.81, P ≤ 0.01; Table 4, Fig 4D). Survival under stressful conditions was only significantly and positively correlated with plasticity in leaf mass fraction (Fig 4B, r = 0.74, P = 0.014). Plasticity in survival was significantly negatively related to plasticity in leaf mass fraction (r = -0.71, P = 0.023). Plasticity in RGR was not significantly related to plasticity of any of the traits (Table 4).

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