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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) net diversity effects (NE), (b) trait-independent complementarity effects (TICE), (c) trait-dependent complementarity effects (TDCE) and (d) dominance effects (DE).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 diversity effects ≠ 0 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.g004: Effects of resource availability on (a) net diversity effects (NE), (b) trait-independent complementarity effects (TICE), (c) trait-dependent complementarity effects (TDCE) and (d) dominance effects (DE).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 diversity effects ≠ 0 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: Light and nutrient availability, sown species richness, functional group or growth stature composition did not significantly affect NE (Table 2). The overall mean of net diversity effects (NE) was positive across all mixtures (test for overall mean > 0; p < 0.001; Fig 4a) and amounted to +128 (± 213) g m-2. Due to the different productivity-levels of the communities dependent on resource availability, the biomass gain in mixtures compared to the monocultures reached ~49% without fertilization irrespective of shading. Biomass gain was ~28% in fertilized unshaded mixtures and amounted to only ~13% in fertilized shaded mixtures. On average, positive net diversity effects were attributable to similar levels of positive trait-independent complementarity effects (TICE: +69 ± 193 g m-2) and positive dominance effects (DE: +55 ± 104 g m-2), while levels of positive trait-dependent complementarity effects were minor (TDCE: +3 ± 35 g m-2) (Fig 4b–4d). Trait-independent complementarity effects (TICE) did not vary dependent on light and nutrient availability, but varied greatly among mixtures within each resource treatment (Fig 4b). Again, the proportion of biomass gain attributable to positive TICE differed dependent on resource availability: in unfertilized mixtures it was ~35% in shaded and unshaded conditions, while it was ~16% in fertilized unshaded mixtures. On average, TICE became even negative in fertilized shaded communities (~3% biomass loss). Trait-dependent complementarity effects (TDCE) were slightly larger in unfertilized than in fertilized mixtures, irrespective of shading (Table 2, Fig 4c). Positive TDCE were significant in non-fertilized shaded mixtures and led to a biomass gain of ~6%, while TDCE did not significantly contribute to diversity effects in non-fertilized shaded mixtures (~3% biomass gain) and in fertilized mixtures (~1% biomass loss irrespective of shading). In contrast, dominance effects (DE) were slightly larger in fertilized than in non-fertilized mixtures, irrespective of shading (Table 2, Fig 4d). The biomass gain due to positive DE amounted to ~10% in non-fertilized mixtures while it was ~13% in fertilized non-shaded mixtures and ~16% in fertilized shaded mixtures. Sown species richness, functional group or growth statures composition had no additional effects on TICE, TDCE and DE (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) net diversity effects (NE), (b) trait-independent complementarity effects (TICE), (c) trait-dependent complementarity effects (TDCE) and (d) dominance effects (DE).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 diversity effects ≠ 0 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

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

pone.0158110.g004: Effects of resource availability on (a) net diversity effects (NE), (b) trait-independent complementarity effects (TICE), (c) trait-dependent complementarity effects (TDCE) and (d) dominance effects (DE).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 diversity effects ≠ 0 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: Light and nutrient availability, sown species richness, functional group or growth stature composition did not significantly affect NE (Table 2). The overall mean of net diversity effects (NE) was positive across all mixtures (test for overall mean > 0; p < 0.001; Fig 4a) and amounted to +128 (± 213) g m-2. Due to the different productivity-levels of the communities dependent on resource availability, the biomass gain in mixtures compared to the monocultures reached ~49% without fertilization irrespective of shading. Biomass gain was ~28% in fertilized unshaded mixtures and amounted to only ~13% in fertilized shaded mixtures. On average, positive net diversity effects were attributable to similar levels of positive trait-independent complementarity effects (TICE: +69 ± 193 g m-2) and positive dominance effects (DE: +55 ± 104 g m-2), while levels of positive trait-dependent complementarity effects were minor (TDCE: +3 ± 35 g m-2) (Fig 4b–4d). Trait-independent complementarity effects (TICE) did not vary dependent on light and nutrient availability, but varied greatly among mixtures within each resource treatment (Fig 4b). Again, the proportion of biomass gain attributable to positive TICE differed dependent on resource availability: in unfertilized mixtures it was ~35% in shaded and unshaded conditions, while it was ~16% in fertilized unshaded mixtures. On average, TICE became even negative in fertilized shaded communities (~3% biomass loss). Trait-dependent complementarity effects (TDCE) were slightly larger in unfertilized than in fertilized mixtures, irrespective of shading (Table 2, Fig 4c). Positive TDCE were significant in non-fertilized shaded mixtures and led to a biomass gain of ~6%, while TDCE did not significantly contribute to diversity effects in non-fertilized shaded mixtures (~3% biomass gain) and in fertilized mixtures (~1% biomass loss irrespective of shading). In contrast, dominance effects (DE) were slightly larger in fertilized than in non-fertilized mixtures, irrespective of shading (Table 2, Fig 4d). The biomass gain due to positive DE amounted to ~10% in non-fertilized mixtures while it was ~13% in fertilized non-shaded mixtures and ~16% in fertilized shaded mixtures. Sown species richness, functional group or growth statures composition had no additional effects on TICE, TDCE and DE (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