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Media type:
E-Article
Title:
How important are species richness, species evenness and interspecific differences to productivity? A mathematical model
Contributor:
Nijs, Ivan;
Roy, Jacques
imprint:
Wiley, 2000
Published in:Oikos
Language:
English
DOI:
10.1034/j.1600-0706.2000.880107.x
ISSN:
0030-1299;
1600-0706
Origination:
Footnote:
Description:
<jats:p>We present a theoretical model to quantify the influence of diversity on productivity and nutrient acquisition in plant communities during exponential growth. The model fractionates diversity into three components, namely species richness (<jats:italic>S</jats:italic>), species evenness (<jats:italic>E</jats:italic>
) and the degree of difference between species (<jats:italic>D</jats:italic>). The influence
of each of these components is assessed individually: <jats:italic>S</jats:italic> is varied
by changing the number of species, <jats:italic>E</jats:italic> by changing their population
size, and <jats:italic>D</jats:italic> by changing the range of species traits critical to
productivity (specific nutrient uptake rate, Σ<jats:sub><jats:italic>r</jats:italic></jats:sub>,
or nutrient use efficiency, <jats:italic>NUE</jats:italic>). <jats:italic>D</jats:italic> was quantified as the
coefficient of variation of Σ<jats:sub><jats:italic>r</jats:italic></jats:sub> or <jats:italic>NUE</jats:italic>. All
three components of diversity enhance the biomass and nutrient stocks in
the community, but the response patterns are different. Species richness
has a saturating influence, whereas effects of <jats:italic>E</jats:italic> and <jats:italic>D</jats:italic> are
linear and exponential, respectively. In all cases the non‐linear
dependence of productivity and nutrient acquisition on Σ<jats:sub><jats:italic>r</jats:italic></jats:sub> and <jats:italic>NUE</jats:italic> during exponential growth was the single
mechanism underlying these effects. This causes the presence of plants
with extreme traits to promote productivity, and <jats:italic>S</jats:italic>, <jats:italic>E</jats:italic> and
<jats:italic>D</jats:italic> all affect the abundance and/or intensity of these extremes. The
model offers a framework to explain differences between experimental
observations, and suggests a concept of diversity where <jats:italic>S</jats:italic> and
<jats:italic>E</jats:italic> are structural components and <jats:italic>D</jats:italic> a qualitative or
functional component, which modulates the influence of the two others. We
propose to explicitly recognise <jats:italic>D</jats:italic> as an integral constituent of plant diversity in future studies.</jats:p>