Pampered inside, pestered outside? Poorter, Hendrik; Fiorani, Fabio; Pieruschka, Roland ...
New phytologist,
December 2016, Letnik:
212, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Plant biologists often grow plants in growth chambers or glasshouses with the ultimate aim to understand or improve plant performance in the field. What is often overlooked is how results from ...controlled conditions translate back to field situations. A meta-analysis showed that labgrown plants had faster growth rates, higher nitrogen concentrations and different morphology. They remained smaller, however, because the lab plants had grown for a much shorter time.We compared glasshouse and growth chamber conditions with those in the field and found that the ratio between the daily amount of light and daily temperature (photothermal ratio) was consistently lower under controlled conditions. This may strongly affect a plant’s source: sink ratio and hence its overall morphology and physiology. Plants in the field also grow at higher plant densities. A second meta-analysis showed that a doubling in density leads on average to 34% smaller plants with strong negative effects on tiller or side-shoot formation but little effect on plant height. We found the r
2 between lab and field phenotypic data to be rather modest (0.26). Based on these insights, we discuss various alternatives to facilitate the translation from lab results to the field, including several options to apply growth regimes closer to field conditions.
Summary
It is increasingly acknowledged that plant–soil feedbacks may play an important role in driving the composition of plant communities and functioning of terrestrial ecosystems. However, the ...mechanistic understanding of plant–soil feedbacks, as well as their roles in natural ecosystems in proportion to other possible drivers, is still in its infancy. Such knowledge will enhance our capacity to determine the contribution of plant–soil feedback to community and ecosystem responses under global environmental change.
Here, we review how plant–soil feedbacks may develop under extreme drought and precipitation events, CO2 and nitrogen enrichment, temperature increase, land use change and plant species loss vs. gain. We present a framework for opening the ‘black box of soil’ considering the responses of the various biotic components (enemies, symbionts and decomposers) of plant–soil feedback to the global environmental changes, and we discuss how to integrate these components to understand and predict the net effects of plant–soil feedbacks under the various scenarios of change.
To gain an understanding of how plant–soil feedback plays out in realistic settings, we also use the framework to discuss its interaction with other drivers of plant community composition, including competition, facilitation, herbivory, and soil physical and chemical properties.
We conclude that understanding the role that plant–soil feedback plays in shaping the responses of plant community composition and ecosystem processes to global environmental changes requires unravelling the individual contributions of enemies, symbionts and decomposers. These biotic factors may show different response rates and strengths, thereby resulting in different net magnitudes and directions of plant–soil feedbacks under various scenarios of global change. We also need tests of plant–soil feedback under more realistic conditions to determine its contribution to changes in patterns and processes in the field, both at ecologically and evolutionary relevant time‐scales.
Lay Summary
Plants are known to influence belowground microbial community structure along their roots, but the impacts of plant species richness and plant functional group (FG) identity on microbial communities ...in the bulk soil are still not well understood. Here, we used 454‐pyrosequencing to analyse the soil microbial community composition in a long‐term biodiversity experiment at Jena, Germany. We examined responses of bacteria, fungi, archaea, and protists to plant species richness (communities varying from 1 to 60 sown species) and plant FG identity (grasses, legumes, small herbs, tall herbs) in bulk soil. We hypothesized that plant species richness and FG identity would alter microbial community composition and have a positive impact on microbial species richness. Plant species richness had a marginal positive effect on the richness of fungi, but we observed no such effect on bacteria, archaea and protists. Plant species richness also did not have a large impact on microbial community composition. Rather, abiotic soil properties partially explained the community composition of bacteria, fungi, arbuscular mycorrhizal fungi (AMF), archaea and protists. Plant FG richness did not impact microbial community composition; however, plant FG identity was more effective. Bacterial richness was highest in legume plots and lowest in small herb plots, and AMF and archaeal community composition in legume plant communities was distinct from that in communities composed of other plant FGs. We conclude that soil microbial community composition in bulk soil is influenced more by changes in plant FG composition and abiotic soil properties, than by changes in plant species richness per se.
Plants interact simultaneously with each other and with soil biota, yet the relative importance of competition vs. plant–soil feedback (PSF) on plant performance is poorly understood. Using a ...meta‐analysis of 38 published studies and 150 plant species, we show that effects of interspecific competition (either growing plants with a competitor or singly, or comparing inter‐ vs. intraspecific competition) and PSF (comparing home vs. away soil, live vs. sterile soil, or control vs. fungicide‐treated soil) depended on treatments but were predominantly negative, broadly comparable in magnitude, and additive or synergistic. Stronger competitors experienced more negative PSF than weaker competitors when controlling for density (inter‐ to intraspecific competition), suggesting that PSF could prevent competitive dominance and promote coexistence. When competition was measured against plants growing singly, the strength of competition overwhelmed PSF, indicating that the relative importance of PSF may depend not only on neighbour identity but also density. We evaluate how competition and PSFs might interact across resource gradients; PSF will likely strengthen competitive interactions in high resource environments and enhance facilitative interactions in low‐resource environments. Finally, we provide a framework for filling key knowledge gaps and advancing our understanding of how these biotic interactions influence community structure.
Belowground drivers of plant diversity van der Putten, Wim H.
Science (American Association for the Advancement of Science),
01/2017, Letnik:
355, Številka:
6321
Journal Article
Recenzirano
Long before Ernst Haeckel coined the term "ecology" in 1866, nature explorers, such as Alexander von Humboldt, observed that vegetation composition changes with climate. However, it still remains ...unclear what determines the local composition and species richness of vegetation. Understanding the roles of belowground invertebrates and microbes is particularly challenging. On pages 173 and 181 of this issue, respectively, Teste et al. (1) and Bennett et al. (2) report field studies that elucidate the role of soil microorganisms as drivers of plant community composition.
Recent demonstrations of the role of plant–soil biota interactions have challenged the conventional view that vegetation changes are mainly driven by changing abiotic conditions. However, while this ...concept has been validated under natural conditions, our understanding of the long‐term consequences of plant–soil interactions for above‐belowground community assembly is restricted to mathematical and conceptual model projections. Here, we demonstrate experimentally that one‐time additions of soil biota and plant seeds alter soil‐borne nematode and plant community composition in semi‐natural grassland for 20 years. Over time, aboveground and belowground community composition became increasingly correlated, suggesting an increasing connectedness of soil biota and plants. We conclude that the initial composition of not only plant communities, but also soil communities has a long‐lasting impact on the trajectory of community assembly.
Plants cope with the environment in a variety of ways, and ecological analyses attempt to capture this through life-history strategies or trait-based categorization. These approaches are limited ...because they treat the trade-off mechanisms that underlie plant responses as a black box. Approaches that involve the molecular or physiological analysis of plant responses to the environment have elucidated intricate connections between developmental and environmental signals, but in only a few well-studied model species. By considering diversity in the plant response to the environment as the adaptation of an information-processing network, new directions can be found for the study of life-history strategies, trade-offs and evolution in plants.
Current climate change has led to latitudinal and altitudinal range expansions of numerous species. During such range expansions, plant species are expected to experience changes in interactions with ...other organisms, especially with belowground biota that have a limited dispersal capacity. Nematodes form a key component of the belowground food web as they include bacterivores, fungivores, omnivores and root herbivores. However, their community composition under climate change‐driven intracontinental range‐expanding plants has been studied almost exclusively under controlled conditions, whereas little is known about actual patterns in the field. Here, we use novel molecular sequencing techniques combined with morphological quantification in order to examine nematode communities in the rhizospheres of four range‐expanding and four congeneric native species along a 2,000 km latitudinal transect from South‐Eastern to North‐Western Europe. We tested the hypotheses that latitudinal shifts in nematode community composition are stronger in range‐expanding plant species than in congeneric natives and that in their new range, range‐expanding plant species accumulate fewest root‐feeding nematodes. Our results show latitudinal variation in nematode community composition of both range expanders and native plant species, while operational taxonomic unit richness remained the same across ranges. Therefore, range‐expanding plant species face different nematode communities at higher latitudes, but this is also the case for widespread native plant species. Only one of the four range‐expanding plant species showed a stronger shift in nematode community composition than its congeneric native and accumulated fewer root‐feeding nematodes in its new range. We conclude that variation in nematode community composition with increasing latitude occurs for both range‐expanding and native plant species and that some range‐expanding plant species may become released from root‐feeding nematodes in the new range.
In Europe, we explored latitudinal community shifts for nematodes—abundant soil organisms that include root herbivores—in the rhizospheres of climate change‐driven range‐expanding plant species. We sampled nematode communities of several range‐expanding plant species along their expansion trajectory and compared these nematode communities with those of related plant species that are native along the entire expansion gradient. We show that nematode communities change with latitude, but that the strength of nematode community shifts strongly depends on range‐expanding plant species.
Plant–soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant–soil ...feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species.
We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of ‘own’ and ‘foreign’ soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR.
All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment.
We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands.
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