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Resource Availability Alters Biodiversity Effects in Experimental Grass-Forb Mixtures.

Siebenkäs A, Schumacher J, Roscher C - PLoS ONE (2016)

Bottom Line: Shading did not alter diversity effects and overyielding.Diversity effects did not increase with species richness and were independent of functional group or growth stature composition.Our field experiment shows that positive diversity effects are possible in grass-forb mixtures irrespective of differences in light availability, but that the chance for the complementary use of resources increases when nutrients are not available at excess.

View Article: PubMed Central - PubMed

Affiliation: UFZ, Helmholtz Centre for Environmental Research, Department of Community Ecology, Theodor-Lieser-Strasse 4, 06120, Halle, Germany.

ABSTRACT
Numerous experiments, mostly performed in particular environments, have shown positive diversity-productivity relationships. Although the complementary use of resources is discussed as an important mechanism explaining diversity effects, less is known about how resource availability controls the strength of diversity effects and how this response depends on the functional composition of plant communities. We studied aboveground biomass production in experimental monocultures, two- and four-species mixtures assembled from two independent pools of four perennial grassland species, each representing two functional groups (grasses, forbs) and two growth statures (small, tall), and exposed to different combinations of light and nutrient availability. On average, shade led to a decrease in aboveground biomass production of 24% while fertilization increased biomass production by 36%. Mixtures were on average more productive than expected from their monocultures (relative yield total, RYT>1) and showed positive net diversity effects (NE: +34% biomass increase; mixture minus mean monoculture biomass). Both trait-independent complementarity effects (TICE: +21%) and dominance effects (DE: +12%) positively contributed to net diversity effects, while trait-dependent complementarity effects were minor (TDCE: +1%). Shading did not alter diversity effects and overyielding. Fertilization decreased RYT and the proportion of biomass gain through TICE and TDCE, while DE increased. Diversity effects did not increase with species richness and were independent of functional group or growth stature composition. Trait-based analyses showed that the dominance of species with root and leaf traits related to resource conservation increased TICE. Traits indicating the tolerance of shade showed positive relationships with TDCE. Large DE were associated with the dominance of species with tall growth and low diversity in leaf nitrogen concentrations. Our field experiment shows that positive diversity effects are possible in grass-forb mixtures irrespective of differences in light availability, but that the chance for the complementary use of resources increases when nutrients are not available at excess.

No MeSH data available.


Related in: MedlinePlus

Effects of resource availability on (a) relative yield totals (RYT), and (b) Dmax.Shown are means (± 1 SE) across two- and four-species mixtures per resource treatment. Treatments manipulating resource availability are abbreviated with: F-S- = no fertilization, no shading, F-S+ = no fertilization, shading, F+S- = fertilization, no shading, and F+S+ = fertilization, shading. Results of tests for overall means of RYT ≠ 1 and Dmax ≠ 0, respectively, for each resource treatment are indicated for different levels of significance with * p ≤ 0.05, ** p ≤ 0.01 and *** p ≤ 0.001. Levels of significance from linear mixed effects models (Table 2) for effects of shade, fertilization and their interaction are given in the upper right corner.
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pone.0158110.g003: Effects of resource availability on (a) relative yield totals (RYT), and (b) Dmax.Shown are means (± 1 SE) across two- and four-species mixtures per resource treatment. Treatments manipulating resource availability are abbreviated with: F-S- = no fertilization, no shading, F-S+ = no fertilization, shading, F+S- = fertilization, no shading, and F+S+ = fertilization, shading. Results of tests for overall means of RYT ≠ 1 and Dmax ≠ 0, respectively, for each resource treatment are indicated for different levels of significance with * p ≤ 0.05, ** p ≤ 0.01 and *** p ≤ 0.001. Levels of significance from linear mixed effects models (Table 2) for effects of shade, fertilization and their interaction are given in the upper right corner.

Mentions: In total, 67% of the mixtures (N = 64) showed non-transgressive overyielding (i.e. RYT > 1). Fertilization had negative effects on relative yield totals (Table 2, Fig 3a). On average, the RYTs were > 1 without fertilization while the RYTs were not significantly different from 1 across fertilized communities. Irrespective of light and nutrient availability, RYTs did not differ depending on species richness, functional group or growth stature composition (Table 2).


Resource Availability Alters Biodiversity Effects in Experimental Grass-Forb Mixtures.

Siebenkäs A, Schumacher J, Roscher C - PLoS ONE (2016)

Effects of resource availability on (a) relative yield totals (RYT), and (b) Dmax.Shown are means (± 1 SE) across two- and four-species mixtures per resource treatment. Treatments manipulating resource availability are abbreviated with: F-S- = no fertilization, no shading, F-S+ = no fertilization, shading, F+S- = fertilization, no shading, and F+S+ = fertilization, shading. Results of tests for overall means of RYT ≠ 1 and Dmax ≠ 0, respectively, for each resource treatment are indicated for different levels of significance with * p ≤ 0.05, ** p ≤ 0.01 and *** p ≤ 0.001. Levels of significance from linear mixed effects models (Table 2) for effects of shade, fertilization and their interaction are given in the upper right corner.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920387&req=5

pone.0158110.g003: Effects of resource availability on (a) relative yield totals (RYT), and (b) Dmax.Shown are means (± 1 SE) across two- and four-species mixtures per resource treatment. Treatments manipulating resource availability are abbreviated with: F-S- = no fertilization, no shading, F-S+ = no fertilization, shading, F+S- = fertilization, no shading, and F+S+ = fertilization, shading. Results of tests for overall means of RYT ≠ 1 and Dmax ≠ 0, respectively, for each resource treatment are indicated for different levels of significance with * p ≤ 0.05, ** p ≤ 0.01 and *** p ≤ 0.001. Levels of significance from linear mixed effects models (Table 2) for effects of shade, fertilization and their interaction are given in the upper right corner.
Mentions: In total, 67% of the mixtures (N = 64) showed non-transgressive overyielding (i.e. RYT > 1). Fertilization had negative effects on relative yield totals (Table 2, Fig 3a). On average, the RYTs were > 1 without fertilization while the RYTs were not significantly different from 1 across fertilized communities. Irrespective of light and nutrient availability, RYTs did not differ depending on species richness, functional group or growth stature composition (Table 2).

Bottom Line: Shading did not alter diversity effects and overyielding.Diversity effects did not increase with species richness and were independent of functional group or growth stature composition.Our field experiment shows that positive diversity effects are possible in grass-forb mixtures irrespective of differences in light availability, but that the chance for the complementary use of resources increases when nutrients are not available at excess.

View Article: PubMed Central - PubMed

Affiliation: UFZ, Helmholtz Centre for Environmental Research, Department of Community Ecology, Theodor-Lieser-Strasse 4, 06120, Halle, Germany.

ABSTRACT
Numerous experiments, mostly performed in particular environments, have shown positive diversity-productivity relationships. Although the complementary use of resources is discussed as an important mechanism explaining diversity effects, less is known about how resource availability controls the strength of diversity effects and how this response depends on the functional composition of plant communities. We studied aboveground biomass production in experimental monocultures, two- and four-species mixtures assembled from two independent pools of four perennial grassland species, each representing two functional groups (grasses, forbs) and two growth statures (small, tall), and exposed to different combinations of light and nutrient availability. On average, shade led to a decrease in aboveground biomass production of 24% while fertilization increased biomass production by 36%. Mixtures were on average more productive than expected from their monocultures (relative yield total, RYT>1) and showed positive net diversity effects (NE: +34% biomass increase; mixture minus mean monoculture biomass). Both trait-independent complementarity effects (TICE: +21%) and dominance effects (DE: +12%) positively contributed to net diversity effects, while trait-dependent complementarity effects were minor (TDCE: +1%). Shading did not alter diversity effects and overyielding. Fertilization decreased RYT and the proportion of biomass gain through TICE and TDCE, while DE increased. Diversity effects did not increase with species richness and were independent of functional group or growth stature composition. Trait-based analyses showed that the dominance of species with root and leaf traits related to resource conservation increased TICE. Traits indicating the tolerance of shade showed positive relationships with TDCE. Large DE were associated with the dominance of species with tall growth and low diversity in leaf nitrogen concentrations. Our field experiment shows that positive diversity effects are possible in grass-forb mixtures irrespective of differences in light availability, but that the chance for the complementary use of resources increases when nutrients are not available at excess.

No MeSH data available.


Related in: MedlinePlus