Grassland Species Loss Resulting from Reduced Niche Dimension. Harpole, W. S. & Tilman, D. 446(7137):791–793.
Grassland Species Loss Resulting from Reduced Niche Dimension [link]Paper  doi  abstract   bibtex   
Intact ecosystems contain large numbers of competing but coexisting species. Although numerous alternative theories have provided potential explanations for this high biodiversity, there have been few field experiments testing between these theories. In particular, theory predicts that higher diversity of coexisting competitors could result from greater niche dimensionality1, for example larger numbers of limiting resources or factors. Alternatively, diversity could be independent of niche dimensionality because large numbers of species can coexist when limited by just one or two factors if species have appropriate trade-offs2. Here we show that plant coexistence and diversity result from the 'niche dimensionality' of a habitat. Plant species numbers decreased with increasing numbers of added limiting soil resources (soil moisture, nitrogen, phosphorus and base cations), which is consistent with theoretical predictions that an increased supply of multiple limiting resources can reduce niche dimension. An observational field study gave similar results. The niche dimension hypothesis also explained diversity changes in the classic Park Grass Experiment at Rothamsted. Our results provide an alternative mechanistic explanation for the effects of nutrient eutrophication on the diversity of terrestrial, freshwater and marine ecosystems. [Excerpt] [...] Our results suggest that a combination of a decreased number of limiting resources and changes in the identity of limiting factors resulting from indirect effects of productivity led to decreased niche dimension and diversity. Decreased resource heterogeneity may also have contributed to decreased niche dimension. [...] Our results suggest that human actions, such as eutrophication, that simplify habitats by decreasing their niche dimensionality can lead to long-term biodiversity loss. Loss of biodiversity could in turn further decrease ecosystem function. Our experimental and observational results from terrestrial grasslands are consistent with those recently found in aquatic systems. How species diversity scales with resource diversity in other systems will depend on the degree to which they are co-limited by multiple resources. Experiments are needed that manipulate multiple resources across important environmental gradients such as productivity and latitude in aquatic and terrestrial ecosystems. If niche axes are independent and approximately equal in importance, diversity should decrease linearly with the loss of niche dimension, but the consequences of niche loss may be even greater if species loss responds multiplicatively as suggested. [...]
@article{harpoleGrasslandSpeciesLoss2007,
  title = {Grassland Species Loss Resulting from Reduced Niche Dimension},
  author = {Harpole, W. Stanley and Tilman, David},
  date = {2007-03},
  journaltitle = {Nature},
  volume = {446},
  pages = {791--793},
  issn = {0028-0836},
  doi = {10.1038/nature05684},
  url = {https://doi.org/10.1038/nature05684},
  abstract = {Intact ecosystems contain large numbers of competing but coexisting species. Although numerous alternative theories have provided potential explanations for this high biodiversity, there have been few field experiments testing between these theories. In particular, theory predicts that higher diversity of coexisting competitors could result from greater niche dimensionality1, for example larger numbers of limiting resources or factors. Alternatively, diversity could be independent of niche dimensionality because large numbers of species can coexist when limited by just one or two factors if species have appropriate trade-offs2. Here we show that plant coexistence and diversity result from the 'niche dimensionality' of a habitat. Plant species numbers decreased with increasing numbers of added limiting soil resources (soil moisture, nitrogen, phosphorus and base cations), which is consistent with theoretical predictions that an increased supply of multiple limiting resources can reduce niche dimension. An observational field study gave similar results. The niche dimension hypothesis also explained diversity changes in the classic Park Grass Experiment at Rothamsted. Our results provide an alternative mechanistic explanation for the effects of nutrient eutrophication on the diversity of terrestrial, freshwater and marine ecosystems.

[Excerpt] [...] Our results suggest that a combination of a decreased number of limiting resources and changes in the identity of limiting factors resulting from indirect effects of productivity led to decreased niche dimension and diversity. Decreased resource heterogeneity may also have contributed to decreased niche dimension. [...] Our results suggest that human actions, such as eutrophication, that simplify habitats by decreasing their niche dimensionality can lead to long-term biodiversity loss. Loss of biodiversity could in turn further decrease ecosystem function. Our experimental and observational results from terrestrial grasslands are consistent with those recently found in aquatic systems. How species diversity scales with resource diversity in other systems will depend on the degree to which they are co-limited by multiple resources. Experiments are needed that manipulate multiple resources across important environmental gradients such as productivity and latitude in aquatic and terrestrial ecosystems. If niche axes are independent and approximately equal in importance, diversity should decrease linearly with the loss of niche dimension, but the consequences of niche loss may be even greater if species loss responds multiplicatively as suggested. [...]},
  keywords = {*imported-from-citeulike-INRMM,~INRMM-MiD:c-1187081,biodiversity,cations,complexity,ecosystem,ecosystem-change,grasslands,habitat-suitability,limiting-factor,multiplicity,niche-modelling,nitrogen,non-linearity,nutrients,phosphorus,plant-species-competition,primary-productivity,species-richness,trade-offs,water-resources},
  number = {7137}
}
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