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Complementary effects of species and genetic diversity on productivity and stability of sown grasslands

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Abstract

Plant species diversity regulates the productivity1, 2, 3 and stability2,4 of natural ecosystems, along with their resilience to disturbance5,6. The influence of species diversity on the productivity of agronomic systems is less clear7, 8, 9, 10. Plant genetic diversity is also suspected to influence ecosystem function3,11, 12, 13, 14, although empirical evidence is scarce. Given the large range of genotypes that can be generated per species through artificial selection, genetic diversity is a potentially important leverage of productivity in cultivated systems. Here we assess the effect of species and genetic diversity on the production and sustainable supply of livestock fodder in sown grasslands, comprising single and multispecies assemblages characterized by different levels of genetic diversity, exposed to drought and non-drought conditions. Multispecies assemblages proved more productive than monocultures when subject to drought, regardless of the number of genotypes per species present. Conversely, the temporal stability of production increased only with the number of genotypes present under both drought and non-drought conditions, and was unaffected by the number of species. We conclude that taxonomic and genetic diversity can play complementary roles when it comes to optimizing livestock fodder production in managed grasslands, and suggest that both levels of diversity should be considered in plant breeding programmes designed to boost the productivity and resilience of managed grasslands in the face of increasing environmental hazards.
Complementary effects of species and genetic
diversity on productivity and stability of sown
grasslands
Iván Prieto1, Cyrille Violle1*, Philippe Barre2, Jean-Louis Durand2, Marc Ghesquiere2
and Isabelle Litrico2*
Plant species diversity regulatesthe productivity13and stability2,4
of natural ecosystems, along with their resilience to disturb-
ance5,6.Theinuence of species diversity on the productivity of
agronomic systems is less clear710. Plant genetic diversity is
also suspected to inuence ecosystem function3,1114, although
empirical evidence is scarce. Given the large range of genotypes
that can be generated per species through articial selection,
genetic diversity is a potentially important leverage of pro-
ductivityincultivatedsystems.Hereweassesstheeffectof
species and genetic diversity on the production and sustainable
supply of livestock fodder in sown grasslands, comprising single
and multispecies assemblages characterized by different levels
of genetic diversity, exposed to drought and non-drought con-
ditions. Multispecies assemblages proved more productive than
monocultures when subject to drought, regardless of the
number of genotypes per species present. Conversely, the tem-
poral stability of production increased only with the number of
genotypes present under both drought and non-drought con-
ditions, and was unaffected by the number of species. We con-
clude that taxonomic and genetic diversity can play
complementary roles when it comes to optimizing livestock
fodder production in managed grasslands, and suggest
that both levels of diversity should be considered in plant
breeding programmes designed to boost the productivity and
resilience of managed grasslands in the face of increasing
environmental hazards.
A large body of works in ecology has shown that both the
number of species and the diversity of functions carried out by
species in an ecosystem are of primary importance for the regulation
of ecosystem functioning and services6,15, in particular in grassland
systems. A greater number of species in an ecosystem has been
shown to have positive effects on sward productivity2,16, stability
of yield17 and response of natural ecosystems to disturbance18,in
line with theoretical expectations1,19. There is a parallel theoretical
line of evidence for the effects of genetic diversity on ecosystem
functions3,20, but experimental tests still remain scarce14,21, notably
in an agronomic context.
Here we quantied the productivity and temporal stability of
yield production and the resistance to stress of experimental sown
grasslands by comparison of single-species covers and multispecies
assemblages (characterized by different levels of genetic diversity;
Fig. 1). Most biodiversity experiments examined diversity effects
under natural or usually non-limiting growth conditions2,17,22.
However, in a world facing increasing climatic hazards, the relative
impact of biodiversity effects compared with those of environmental
stress remains unknown. Here we have additionally applied a
short-term yet intense drought event to simulate a situation that
already is, and is projected to be even more, common in many
crop land regions23. A total of 124 experimental plots were
planted, half of which were exposed to dry conditions during 6
weeks. Five perennial plant species (Lolium perenne, Festuca
arundinacea,Dactylis glomerata,Trifolium repens and Medicago
sativa) commonly used in the establishment of multispecies sown
grasslands in temperate climates7were cultivated in isolation
(monocultures) or together (multispecies assemblages). Each
species was represented by a set of ten genotypes. Each genotype
resulted from a 1.5-year cloning of plants (14,000 clones total)
issued from contrasted natural populations (Supplementary
Methods and Supplementary Table 1). Monocultures consisted of
50 individuals from ten genotypes per species (ve individual
plants per genotype with ten replicated plots per species).
Multispecies assemblages consisted of ten individuals from each
of the ve species (50 individuals in total) with varying levels of
genetic diversity: ten genotypes per species (one plant per genotype
per species, ten plots), ve genotypes (two plants per genotype per
species, 32 plots) or one genotype per species (ten plants per geno-
type per species, 32 plots). For the ve- and one-genotype assem-
blages, genotypes in each plot were randomly selected from the
ten-genotype pool. Using these three levels of genetic diversity in
multispecies assemblages allowed us to test the independent inu-
ence of genetic diversity on total biomass production of each assem-
blage. The comparison between the ten-genotype monocultures and
the ten-genotype multispecies assemblages was conducted to test
the direct impact of species diversity in multigenotypic covers. We
regularly harvested the above-ground biomass of all plots (six har-
vests in total) to evaluate the temporal variation of biomass pro-
duction over the course of the experiment and the role of both
species and genetic diversity in the stability of biomass production.
The comparison of biomass production of the ten-genotype
monocultures and the ten-genotype multispecies assemblages
showed signicantly higher biomass production for the successive
cuts when ve grassland species were grown together compared
with one-species situations (Fig. 2a, P< 0.01), with no signicant
effects of drought (Supplementary Table 2, P= 0.42). Interestingly,
these effects were driven by a signicant effect of species diversity
in the drought treatment only (P< 0.05). Along these lines, multi-
species assemblages established and reached a maximum pro-
ductivity on average 10% faster than monocultures as stressed by
higher plot-level maximum growth rates (Fig. 2c, P< 0.05). Again,
these effects were signicant only for communities subjected to
drought (Supplementary Table 2, P= 0.03). Overall, our ndings
provide support to biodiversity theories largely tested in ecological
1CNRS, CEFE UMR 5175, Université de Montpellier Université Paul Valéry EPHE, 1919 Route de Mende, Montpellier Cedex 5 34293, France. 2INRA,
URP3F, RD 150, site du chêne, BP 86006, Lusignan 86600, France. *e-mail: isabelle.litrico@lusignan.inra.fr;cyrille.violle@cefe.cnrs.fr
LETTERS
PUBLISHED: 30 MARCH 2015 | ARTICLE NUMBER: 15033 | DOI: 10.1038/NPLANTS.2015.33
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contexts4,6, and strikingly demonstrate the importance of incorpor-
ating species diversity in sown grasslands to favour forage yields24,
specically under stressful growth conditions25. Interestingly, the
ve-species diversity level often appears as a tipping pointin diver-
sityproductivity curves in ecological studies16. Despite signicant
effects of species diversity on biomass production, we did not nd
any effect on the temporal variability of biomass production (as
expressed by the coefcient of variation of community biomasses
assessed at each cut, six cuts in total) (Fig. 1e and Supplementary
Table 2). This suggests that, despite the frequently described positive
effect of species diversity on ecological stability in natural commu-
nities26, species diversity may have little impact on temporal crop
stability, at least at such levels of diversity.
The mechanisms leading to overyielding in biodiversity exper-
iments have been intensively debated in ecology and agronomy6,27.
These basically relate to two types of processes: the complementary
effects, that is the synergetic effects of species including partitioning
of resources (each using a specic portion of available resources in
multispecies assemblages), plant facilitation and/or reduced apparent
competition, and the selection effect that is the greater probability of
nding more productive species in species-rich assemblages (also
referred to as sampling effect6). Both processes probably act simul-
taneously in most assemblages, which explains the difculties dis-
tinguishing them6,28 but a statistical method to accurately
differentiate them has been developed29. Applying this method to
our experiment, we showed that multispecies assemblages were
characterized by a positive net biodiversity effect (ΔY=234.1
82.62 g m
2
,t= 2.83, d.f. = 9, P< 0.001), which highlights a signi-
cant diversity-caused overyielding in multispecies assemblages com-
pared with monocultures (15% increase on average). When we
partitioned this net effect into complementary and selection effects,
we observed that the average complementary effect was positive
(989.56 ± 112.24 g m
2
,t= 8.81, d.f. = 9, P< 0.001) whereas the
average selection effect was negative (755.37 ± 87.36 g m
2
,
Varying genetic
diversity only
Varying species
diversity only
(constant
genetic
diversity)
Monocultures (one species)
Multispecies assemblages (five species)
10 genotypes per
species
10 genotypes per
species
Five genotypes per species
One genotype per species
Medicago sativa L. Trifolium repens L. Lolium perenne L.
Festuca arundinacea Scherb. Dactylis glomerata L.
a
b
Figure 1 | Experimental manipulation of both species and genetic diversity. a, Plant communities were grown in microcosms for 1 year (n=124). Five
different species were grown either in monocultures (ten genotypes per species) or in ve-species multispecies assemblages with three levels of genetic
diversity (one, ve or ten genotypes per species, see Methods section for details). The comparison between mono- and multispecies assemblages with the
highest level of genetic diversity enabled testing for species diversity effects and the comparison among multispecies assemblages enabled testingfor
genetic diversity effects. b, Example of microcosms (front, multispecies assemblage microcosm).
LETTERS NATURE PLANTS DOI: 10.1038/NPLANTS.2015.33
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t=8.64, d.f. = 9, P< 0.001). Moreover the log
10
ratio between the
absolute value of selection and complementary effects averaged
0.27 ± 0.09, and was lower than zero (t=2.80, d.f. = 9, P=0.01)
indicating that absolute selection effects were lower than complemen-
tary effects (|SE| < |CE|). Together our ndings imply that the species
diversity-caused overyielding was primarily driven by complemen-
tary effects (resource use complementarity and/or facilitation), in
accordance with the results of many ecological experiments using
wild species28. This has important consequences in agronomical
and agroecological contexts since the synergetic effects of species
may be more important to account for than the choice of productive
species to incorporate in multispecies plant assemblages.
We found no effect of genetic diversity on biomass production
(P= 0.24) and plot-level growth rate (P= 0.53) when analysing the
three levels of genetic diversity (one, ve and ten genotypes per
species) of multispecies assemblages (Fig. 2b,d and Supplementary
Table 3). This suggests that species richness effects may be more
important than genetic richness effects for the control of pro-
ductivity of the studied multispecies assemblages. Conversely,
genetic diversity and drought both strongly impacted the stability
of biomass production, with the greatest stability (lowest coefcient
of variation) in the ten-genotype assemblages (P< 0.01) and, overall,
in communities that did not experience drought (Fig. 2f and
Supplementary Table 3, treatment effect P< 0.01). One key mechan-
ism advanced to explain the diversity effects on ecosystem stability is
the growth asynchrony of the different species of an assemblage19,
that is the fact that species produce their peak biomass at different
dates. Here we showed lower synchrony between species in the
ve- and ten-genotype assemblages (Fig. 3a, Supplementary
Table 3, P= 0.01) and a strong positive correlation between
species synchrony and the coefcient of variation in biomass pro-
duction (Fig. 3b, R
2
= 0.28, F
1,72
= 29.23, P< 0.001). This
Total biomass (g m−2)
Total biomass (g m−2)
2,500
3,000
3,500
4,000
15
Species diversity**
Treatment n.s.
ab
2,500
3,000
3,500
4,000 Genetic diversity n.s.
Treatment n.s.
Biomass production rate (g day−1 m−2)
Biomass production rate (g day−1 m−2)
15
20
25
30
35
15
Species diversity*
Treatment n.s.
15
20
25
30
35 Genetic diversity n.s.
Treatment n.s.
Number of species
Coecient of variation
in biomass production
Coecient of variation
in biomass production
0.0
0.6
0.8
1.0
1.2
15
Species diversity n.s.
Treatment n.s.
Number of genotypes
Number of species Number of genotypes
Number of species Number of genotypes
0.0
0.6
0.8
1.0
1.2
1510
1510
1510
Genetic diversity**
Treatment**
cd
ef
Irrigated
Drought
Figure 2 | Diversity effects on biomass production and stability. Effect of species (n=60, a,c,e) and genetic diversity (n=74,b,d,f) on total above-ground
biomass of the whole community, plot-level growth rate and community stability measured as the coefcient of variation in biomass production (six
harvests). Values are mean ± s.e.m. See Supplementary Material for more details. *P< 0.05; **P< 0.01; n.s., non signicant.
NATURE PLANTS DOI: 10.1038/NPLANTS.2015.33 LETTERS
NATURE PLANTS |www.nature.com/natureplants 3
corroborates the asynchrony hypothesis26 to explain the positive
effects of genetic diversity on the temporal stability of multispecies
assemblages and points to a similar mechanism explaining the lower
stability in communities subjected to stress. Interestingly, we have
shown that a greater genetic diversity within species increased the
between-species growth asynchrony in multispecies assemblages.
Collectively, we demonstrated the complementary effects of taxo-
nomic and genetic diversities on the productivity and stability of
assemblages of forage species: (1) biomass production is favoured
in high species diversity assemblages, notably when subjected to a
drought event, and (2) the temporal stability of biomass production
is primarily controlled by genetic diversity. The fact that the
maximum number of species and genotypes employed was equal
to the maximum diversity treatments (ve and ten for taxonomic
and genetic diversity, respectively) is a potential limitation for inter-
preting the effects of diversity per se. Moreover, the restricted area of
the microcosms and the short duration of the experiment can limit
extrapolation of these results. Nevertheless, this study is the rst
study evaluating the joint effects of the two facets of diversity in
an agronomic context and should stimulate other future experimen-
tal manipulations. Along these lines, our results thus suggest that
not only interspecic but also intraspecic interactions tend to
stabilize community biomass in genetically diverse communities26.
More broadly, this emphasizes the importance of improving our
knowledge about the role of intraspecic variability in the regulation
of biomass production and its temporal stability.
From a plant-breeding perspective, current programmes are still
largely monoculture driven, limiting the inclusion of plant diversity
in breeding schemes, whether at the specic or genetic level. Yet we
demonstrate here that complementary effects between species and
genotypes are pivotal and need to be accounted for. Including
both levels of diversity in breeding schemes thus appears crucial
to allow a proper selection of the best-suited species and genotypes
for building multispecies communities. Further experimental evi-
dence comes from a previous study30 that pointed out a modi-
cation of speciestraits and associated short-term phenotypic
changes for species grown and developed in mixtures. The phenoty-
pic changes described in30 might have driven the complementary
effects observed in our study. These and our own results point to
a difference in the performance and stability of species when
cultivated in monoculture or in multispecic culture. A renewal of
plant breeding programmes to include both levels of diversity
could speed the improvement of species grown in crop mixtures
through articial selection targeted on traits involved in these
complementary effects.
Methods
Experimental design. The experiment was performed at the Poitou-Charentes
INRA centre, Lusignan, France. A total of 124 plots 0.40 × 0.45 × 0.4 m were
established in March 2012 and lled with 4 cm of sterile sand to allow drainage and
the remainder lled with soil (315DO, Peltracom, France). Experimental plots were
split into two levels of species diversity; monocultures (single-species cultures,
50 plots = 5 species × 10 replicated monocultures) or multispecies assemblages
(mixed plant communities of ve species, 74 plots). Monocultures had one level of
genetic diversity consisting of ten genotypes per species. For multispecies
assemblages, three levels of genetic diversity were established: one, ve or ten
genotypes per species. In a given multispecies assemblage genotypes were randomly
chosen from the ten-genotype pool (diversity treatments section for details).
Experimental plots were randomly established in a chessboard-like structure so that
two communities were in contact only at their corners and potential border effects
were minimized (Fig. 1 in main text). Empty plots between communities were lled
with sand. Experimental plots were situated under an open greenhouse with a
transparent ceiling to allow radiation but prevent natural rain events. Plots were
irrigated bidaily with a sprinkler irrigation system. Soil water content (v/v) was
measured using a time domain reectometry probe (Trime) at regular intervals
during the experiment and remained over 45% (eld capacity). Following the fourth
cut on 15 September (117 days after the beginning of the experiment), half of the
plots (62) were subjected to a drought treatment consisting of total withdrawal of
plant irrigation over 6 weeks. Irrigation was then restored after the fth cut on
25 Oc tober when soil water content reached 5.97 ± 0.53% (mean ± s.e.m., n= 15),
that is approximately 20% of eld capacity on average. For each irrigation level,
monocultures of all species were replicated ve times, multispecies assemblages with
one or ve genotypes per species were replicated 16 times (that is 16 different
combinations of genotypes), and multispecies assemblages with ten genotypes per
species were replicated ve times. All the plots were randomized at each
irrigation level.
Species and genetic diversity. The ve species used in this study include three
perennial C
3
grasses (Lolium perenne L., Festuca arundinacea Scherb. and Dactylis
glomerata L.) and two nitrogen-xing legumes (Trifolium repens L. and Medicago
sativa L.). For each species, we obtained viable seeds from ten natural populations
(ecotypes) distributed along a latitudinal gradient from northern Africa to Russia
(Supplementary Table 1). Seeds were obtained from Plant Genetic Resources
(United States Department of Agriculture, USDA, Geneva, NY), the Institute of
Biological, Environmental and Rural Sciences (IBERS) and from the INRA Genetic
resources centre of forage species (Institute National de la Recherche Agronomique,
URP3F, Lusignan, France). Twenty seeds per population were germinated and one
randomly chosen plant per population was selected for cloning. The selected
individual (genotype) was subsequently cloned to obtain the number of genetically
identical plants needed to establish the mono- and multispecies assemblages plots. A
total of 14,000 clones were grown in individual pots for 45 days and then transferred
to mono- or multispecies communities.
Monocultures were established for each species and replicated ve times in each
treatment. Each monoculture contained the ten genotypes per species, 50 individual
plants total (ve clonal individuals per genotype) planted in a 0.24 × 0.24 m area
within the plot (0.40 × 0.45 × 0.4 m) to avoid potential border effects. The remaining
area was planted with a similar species × genotype composition but was not
considered in the analysis. Individual clones were spaced 3 cm from each other and
randomly spaced within the plot. Multispecies assemblages were composed of the
ve species planted at equal densities (ten individuals per species, 50 in total).
Number of genotypes
Ψb
0.0
0.1
0.5
0.6
0.7
0.8
0.9
1.0
1510
aGenetic diversity*
Treatment**
Irrigated
Drought
Ψb
Coecient of variation
in biomass production
0.0
0.5
0.7
0.9
1.1
0.0 0.4 0.5 0.6 0.7 0.8 0.9 1
1 genotype per species
5 genotypes per species
10 genotypes per species
bR2 = 0.28, P < 0.001
Figure 3 | Genetic diversity and stability of biomass production. a, Effect of genetic diversity on species-level synchrony (Ψ
b
,n= 74, mean ± s.e.m.).
b, Ordinary least squares linear regression between plant community stability (coefcient of variation) and species synchrony (Ψ
b
) within multispecies
assemblages (n=74).Legendinaapplies to both panels. See Supplementary Material for detailed statistical results *P< 0.05; **P<0.01.
LETTERS NATURE PLANTS DOI: 10.1038/NPLANTS.2015.33
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Individuals from different species were randomly planted within the plots assuring
all possible interactions between all the species. For multispecies assemblages, three
levels of genetic diversity were established, one, ve or ten genotypes per species. For
the one- and ve-genotype multispecies assemblages, genotypes were randomly
chosen and propagated from the experimental pool of genotypes. Multispecies
assemblages thus had one genotype per species (ten individuals/genotype per
species) replicated 16 times (that is 16 different combinations of genotypes of each
species), ve genotypes per species (two individuals/genotype per species) replicated
16 times or all ten genotypes per species (one individual/genotype per species)
replicated ve times. All experimental plots were planted in March 2012 and the
experiment ran for 1 year until the last cut in March 2013. Above-ground biomass
was measured by species for each plot by cutting all individuals fromthe community
at the beginning of foliage senescence, that is approximately each month, allowing
for a 4-week regrowth period between cuts (once a month from July to December
2012 and once in March 2013). During the experiment no apparent plant mortality
was observed. See the Supplementary Information for calculations and
statistical analysis.
Received 27 November 2014; accepted 26 February 2015;
published 30 March 2015
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Acknowledgements
We thank Mark Vellend (Université de Sherbrook) and Xavier Morin (UMR 5175 CEFE-
CNRS) for their helpful comments. The URP3F technical team and particularly David
Alletru, Brigitte Bonneau, Dominique Denoue, Magali Caillaud, Franck Gelin and Pascal
Vernoux provided experimental assistance. The Agence National de la Recherche, France
(PRAISE, ANR-13-BIOADAP-0015) funded this work. C.V. was supported by the
European Research Council (ERC) Starting Grant Project Ecophysiological and
biophysical constraints on domestication in crop plants(Grant ERC-2014-StG-
CONSTRAINTS).
Author contributions
I.L. and P.B. designed the experiment and led the initial working group and set-up of the
experiment. I.L. and P.B. collected the data and I.P. organized the dataset. I.P. and C.V.
coordinated the analysis and write-up of the work and all authors contributed to writing a
nal version of the manuscript.
Additional information
Supplementary information is available online.
Reprints and permissions information is
available online at www.nature.com/reprints. Correspondence and requestsfor materials should
be addressed to C.V. and I.L.
Competing interests
The authors declare no competing nancial interests.
NATURE PLANTS DOI: 10.1038/NPLANTS.2015.33 LETTERS
NATURE PLANTS |www.nature.com/natureplants 5
... Plant genetic diversity has been shown to provide multiple ecosystem services (e.g. biological control 1 ) in terrestrial [1][2][3][4][5] and marine 6 ecosystems. In natural ecosystems, plant genetic diversity is a key component of species and ecosystem health and can be manipulated by modifying the population genetic richness of plants within or around managed lands 1,2,7 or aquatic habitats 8 . ...
... biological control 1 ) in terrestrial [1][2][3][4][5] and marine 6 ecosystems. In natural ecosystems, plant genetic diversity is a key component of species and ecosystem health and can be manipulated by modifying the population genetic richness of plants within or around managed lands 1,2,7 or aquatic habitats 8 . In particular, increasing plant genetic diversity can increase plant productivity 9,10 and crop yield 1 , suppress plant antagonists such as insect herbivores 11 , weeds (i.e. ...
Article
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Intraspecific genetic diversity is an important component of biodiversity. A substantial body of evidence has demonstrated positive effects of plant genetic diversity on plant performance. However, it has remained unclear whether plant genetic diversity generally increases plant performance by reducing the pressure of plant antagonists across trophic levels for different plant life forms, ecosystems and climatic zones. Here, we analyse 4702 effect sizes reported in 413 studies that consider effects of plant genetic diversity on trophic groups and their interactions. We found that that increasing plant genetic diversity decreased the performance of plant antagonists including invertebrate herbivores, weeds, plant-feeding nematodes and plant diseases, while increasing the performance of plants and natural enemies of herbivores. Structural equation modelling indicated that plant genetic diversity increased plant performance partly by reducing plant antagonist pressure. These results reveal that plant genetic diversity often influences multiple trophic levels in ways that enhance natural pest control in managed ecosystems and consumer control of plants in natural ecosystems for sustainable plant production.
... This is evident for grass-legume mixtures versus pure grass or legume forage stands under low N fertilization. Furthermore, a larger diversity in plant forms and phenology were shown to bring about more stable production with seasons and years (Prieto et al. 2015;Meilhac et al. 2019). Similarly, multi-species living mulch could offer advantages compared to a mono-specific living mulch. ...
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Both from the environmental and economical perspective, reducing the use of mineral nitrogen and herbicides is one of the future challenges in cereal production. Growing winter cereals on perennial legume living mulch such as white clover ( Trifolium repens L.) or lucerne ( Medicago sativa L.) is one of several options to reduce the need for mineral nitrogen fertilizer and herbicides in winter cereal production. Given the importance of winter cereals in the world, adopting this technique could greatly improve the sustainability of crop production. Through competition with the crop however, the living mulch can negatively affect cereal yield. Here, we (i) review how living mulch can be introduced in the system, (ii) synthetize potential advantages and disadvantages of that system, and (iii) explore different strategies to control the competition between the crop and living mulch. The major findings are that (i) competition between cereals and mulch can lead to significant yield reductions if not controlled properly and (ii) perennial legume varieties used as living mulch so far are varieties bred for forage production. We hypothesize that a dedicated breeding program might lead to living mulch varieties with a smaller impact on cereal yield compared to forage varieties, allowing to grow cereals with reduced nitrogen and herbicide inputs. We propose the main characteristics of an ideotype for such a perennial legume variety.
... High functional trait diversity may promote grassland productivity via plant Communicated by Brian J. Wilsey. community complementarity, where trait variability allows diverse resource acquisition strategies (Liang et al. 2015;Prieto et al. 2015). Land use such as mowing (harvesting plant material for forage) plays an important role in driving plant functional diversity change (Bernhardt-Römermann et al. 2011;Delgado de la Flor et al. 2020). ...
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Understanding the mechanisms of grassland productivity variation is critical for global carbon cycling and climate change mitigation. Heretofore, it is unknown how different environmental factors drive small-scale spatial variation in productivity, and whether land use intensification, one of the most important global changes, can regulate the processes that drive productivity change. Here we performed an 18-year exclosure experiment across six sites with high-intensity mowing/grazing history in northern China to examine the effects of land use intensification on plant functional diversity, soil properties, and their relative contributions to above-ground net primary productivity (ANPP). We found that plant functional diversity and soil properties contributed to the variation in ANPP both independently and equally in enclosed grasslands (plant diversity: 20.6%; soil properties: 19.5%). Intensive land use significantly decreased the Rao’s quadratic entropy (RaoQ) and community-weighted mean value (CWM) of plant height, and further suppressed the contributions of plant functional diversity to ANPP. In contrast, intensive land use increased soil available N, P, pH, electrical conductivity, and homogeneity of soil available P, and strengthened their contributions to ANPP (31.5%). Our results indicate that high-intensity land use practices in grasslands decrease the role of plant functional diversity, but strengthen the effects of soil properties on productivity. We, therefore, suggest that plant functional diversity can be used effectively to boost productivity in undisturbed grasslands, while soil properties might be a more critical consideration for grassland management in an areas with increased land use.
... According to Schöb et al. (2015) intraspecific diversity of barley increased biomass by complementarity effects while increased species diversity of weeds increased biomass through selection effects (highly productive species increasing mixture productivity). Prieto et al. (2015) found in grassland experiments that increased species diversity contributed to higher productivity under droughts compared to monocultures while intraspecific diversity increased the temporal stability of productivity, concluding that both levels of diversity contribute in complementary ways to resilience of plant communities. Another study also found that cultivar diversity in grassland mixtures increased productivity and production stability (Meilhac et al., 2019). ...
Thesis
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This thesis combines experimental work on heterogeneous crop populations (HP) and species mixtures (SM) with a social scientific and participatory approach. Chapter 1 introduces crop communities as a concept to integrate multiple approaches to diversify farming systems. HPs provide intraspecific and SM interspecific diversity in crop communities. A key challenge for the genetic improvement of HPs, especially for root traits is to combine effective selection to improve HPs while maintaining intraspecific diversity. In Chapter 2 a hydroponic system was tested for its suitability to non-destructively assess root traits on a population level in order to achieve genetic gain and maintain diversity. The hydroponic selection for long seminal roots led to an increase of seminal root length by 1.6 cm (11.6%) in a single generation with a heritability of 0.59, thus providing a method for population level selection of root traits. Chapter three reports on a multifunctional evaluation of SM. Seven wheat HP and eight line cultivars from central Europe and Hungary were tested as pure stands (100% sowing density) and in SM with a winter pea cultivar with 70% wheat and 50% pea sowing density under organic conditions. SM increased cereal grain quality, weed suppression, resource use efficiency, yield gain and reduced lodging relative to pea pure stands, indicating multifunctionality. Effects were greater in 2018/19, characterized by dry and nutrient poor conditions than in 2019/20 when nutrient levels were higher. Wheat entries varied considerably for protein content and yield in both, SM and monocultures. Under higher nutrient availability, entry-based variation was reduced in both systems and peas were suppressed. HPs were more stable across environments for yield and protein than line cultivars. Depending on year, different line cultivars outperformed the HPs for either protein content or yield. Results have to be interpreted with caution due to limited number of environments. Chapter 4 reports on a qualitative social scientific investigation. Socially shared models of SM adoption were built from interview data with farmers to identify the main factors for SM adoption: (1) perceived relative mixture performance, (2) suitability within the farm context, (3) challenges and opportunities in mixture management due to increased complexity, (4) knowledge and technology as resources to handle mixture management and (5) quality standards in the food value chain. The final chapter 5 engages in a broader discussion of the contribution of complementarity and facilitation to the studied systems and identifies the spatiotemporal design of crop communities and its interplay with agroecological interactions, farm management and economics as research priority. The thesis is concluded by delivering an explicit definition and conceptual model for crop communities and crop community systems.
... In some cases, this has caused entire crop varieties to become imperilled-for example, coffee in Latin America 92 and potato during the Irish potato famine 93 , or removed from the food system entirely (for example, Gros Michel banana 94 ). Biodiversity-ecosystem stability relationships are some of the most reproducible patterns in ecology [95][96][97][98][99] . As a result, there is mounting effort to increase the aboveground macrobiological diversity of our managed landscapes. ...
Article
Microbial life represents the majority of Earth’s biodiversity. Across disparate disciplines from medicine to forestry, scientists continue to discover how the microbiome drives essential, macro-scale processes in plants, animals and entire ecosystems. Yet, there is an emerging realization that Earth’s microbial biodiversity is under threat. Here we advocate for the conservation and restoration of soil microbial life, as well as active incorporation of microbial biodiversity into managed food and forest landscapes, with an emphasis on soil fungi. We analyse 80 experiments to show that native soil microbiome restoration can accelerate plant biomass production by 64% on average, across ecosystems. Enormous potential also exists within managed landscapes, as agriculture and forestry are the dominant uses of land on Earth. Along with improving and stabilizing yields, enhancing microbial biodiversity in managed landscapes is a critical and underappreciated opportunity to build reservoirs, rather than deserts, of microbial life across our planet. As markets emerge to engineer the ecosystem microbiome, we can avert the mistakes of aboveground ecosystem management and avoid microbial monocultures of single high-performing microbial strains, which can exacerbate ecosystem vulnerability to pathogens and extreme events. Harnessing the planet’s breadth of microbial life has the potential to transform ecosystem management, but it requires that we understand how to monitor and conserve the Earth’s microbiome. Efforts to futureproof global microbial biodiversity are proposed, in particular in managed landscapes, to monitor, manage and restore the soil fungal microbiome.
... The analysis of 50 Lolium perenne cultivars from the French forage seed catalog revealed high genetic diversity in heading date with differences of up to 45 days between the earliest and latest cultivars, all sites and years considered (Figure 2). The intraspecific variability in heading date is similar to that observed between sites and years, thus constituting an interesting pool of genetic resources to increase diversity and durability of grasslands (Prieto et al., 2015;Litrico et al., 2016). Lastly, models of reproductive development should lead to better predictions of the dynamics of biomass quantity and quality in order to optimize grassland management. ...
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In the context of climate change and agrosystem complexification, process-based models of the reproductive phenology of perennial grasses are essential to optimize the agronomic and ecologic services provided by grasslands. We present a functional–structural model called L-GrassF, which integrates the vegetative and reproductive development of individual Lolium perenne plants. The vegetative development in L-GrassF was adapted from a previous model of perennial ryegrass where leaf elongation and tillering dynamics partially result from self-regulated processes. Significant improvements have been made to this vegetative module in order to deal with the whole growing cycle during which plants are exposed to contrasting temperatures. The reproductive module is a new functionality describing the floral induction of the individual tiller from daily temperature and photoperiod as well as its phenological state. From the interactions between the vegetative and reproductive developments, L-GrassF simulates the dynamics of plant architecture, the floral transition and heading date (HD) at tiller level. A sensitivity analysis was performed on L-GrassF and showed that parameters controlling the kinetics of leaf elongation and leaf appearance rate have a significant impact on HD. After calibration, L-GrassF was able to simulate the HD on seven L. perenne cultivars grown in a broad range of environmental conditions, as provided by an independent data set. We conclude that L-GrassF is a significant step towards better prediction of grassland phenology in contrasted conditions.
... Biodiversity positively affects community productivity, as well as ecosystem service provisioning, and has been observed across multiple biomes (Polley et al., 2013;Tilman et al., 2006;Zhang et al., 2019). According to numerous empirical and theoretical studies, diversity-dependent overyielding is influenced by certain underlying mechanisms, such as complementary (e.g., resource partitioning) and selection (i.e., the role of a particular species) effects (Loreau and Hector, 2001;Prieto et al., 2015). Despite this, considerable debate still remains on the context dependency of biodiversity-productivity relationships. ...
Article
Plant and soil microbial community composition play a central role in maintaining ecosystem functioning. Most studies have focused on soil microbes in the bulk soil, the rhizosphere and inside plant roots, however, less is known about the soil community that exists within soil aggregates, and how these soil communities influence plant biomass production. Here, using field-conditioned soil collected from experimental ungrazed and grazed grasslands in Inner Mongolia, China, we examined the composition of microbiomes inside soil aggregates of various size classes, and determined their roles in plant-soil feedbacks (PSFs), diversity-productivity relationships, and diversity-dependent overyielding. We found that grazing induced significantly positive PSF effects, which appeared to be mediated by mycorrhizal fungi, particularly under plant monocultures. Despite this, non-additive effects of microbiomes within different soil aggregates enhanced the strength of PSF under ungrazed grassland, but decreased PSF strength under intensively grazed grassland. Plant mixture-related increases in PSF effects markedly enhanced diversity-dependent overyielding, primarily due to complementary effects. Selection effects played far less of a role. Our work suggests that PSF contributes to diversity-dependent overyielding in grasslands via non-additive effects of microbiomes within different soil aggregates. The implication of our work is that assessing the effectiveness of sustainable grassland restoration and management on soil properties requires inspection of soil aggregate size-specific microbiomes, as these are relevant determinants of the feedback interactions between soil and plant performance.
Article
Genetic diversity can have important ecological consequences on population dynamics and ecosystem functions and processes. While the direct effect of genetic diversity on population performance has been widely documented, its soil legacy effect has received little attention. To assess both the direct and soil legacy effects of genetic diversity on population performance, we conducted a plant-soil feedback experiment with 12 genotypes of a clonal plant Hydrocotyle vulgaris. We first conditioned soils (conditioning phase) by growing populations of H. vulgaris consisting of 1, 2, 4 and 8 genotypes in the soils and then tested the soils (test phase) by growing populations consisting of all 12 genotypes in sterilized bulk soils inoculated with each of the conditioned soils at a volume ratio of 10%. At the end of the conditioning phase, both biomass and the number of ramets of the populations of H. vulgaris first decreased and then increased with increasing genotypic diversity, indicating a direct effect of genetic diversity on population performance. At the end of the test phase, both biomass and number of ramets were significantly higher when the populations were grown in the soils conditioned by the populations consisting of 1 and 2 genotypes than when they were grown in the soils conditioned by the populations consisting of 4 and 8 genotypes, suggesting a soil legacy effect. Therefore, genetic diversity can have both a direct and a soil legacy effect on population productivity and size of H. vulgaris. These results highlight the importance of intraspecific differences on population performance and suggest that soil legacy effects should also be considered to fully understand the role of genetic diversity.
Article
Genetic relatedness and diversity of 62 cultivars and breeding lines of tetraploid Italian ryegrass (Lolium multiflorum Lam.; 39 accessions) and its interspecific hybrids, Festulolium (18 accessions), and hybrid ryegrass (Lolium × hybridum Hausskn.; 5 accessions), mainly from Japan, were revealed based on 2,824 genome‐wide allele frequencies obtained by the genotyping by random amplicon sequencing‐direct (GRAS‐Di) method using bulk genomic DNA testing. Genomic composition of each accession was estimated according to the occurrence of 77,373 unique GRAS‐Di sequences in the reference population consisting of diploid Italian ryegrass, meadow fescue (Festuca pratensis Huds.), and perennial ryegrass (Lolium perenne L.). The high correlation coefficient (0.98) between the fescue‐specific reads ratio and the previously obtained f‐ratio of genomic in situ hybridization in Festulolium cultivars suggests the usefulness of this simple method. Both cluster analysis based on Nei's standard genetic distance (DST) and principal component analysis (PCA) showed that groups were formed largely by species. However, the complex heritage of Lolium‐Festuca (Festulolium) materials could not be determined by species registration or breeding history alone. Some Festulolium accessions were closely related to Italian ryegrass, whereas some defined as Italian ryegrass may actually be interspecific hybrids. The high genetic diversity of Festulolium compared to Italian ryegrass and hybrid ryegrass revealed by PCA seems due to the wide range of fescue‐specific read ratios (0.04–33.0%). Tetraploid Italian ryegrass did not show clear structural differentiation, but some genetic relationships attributable to breeding history were demonstrated. Mean pairwise DST of tetraploid Italian ryegrass cultivars was significantly lower than that of diploids. Tetraploids and diploids could be separated by PCA plot. Although mean expected heterozygosities of tetraploid and diploid cultivars were not significantly different, the results suggest that the utilization of diploid genetic resources is effective in maintaining and increasing the genetic diversity of breeding populations of tetraploid Italian ryegrass.
Preprint
The intra- and interspecific facets of biodiversity have traditionally been quantified and analysed separately, limiting our understanding of how evolution has shaped biodiversity, how biodiversity (as a whole) alters ecological dynamics, and hence eco-evolutionary feedbacks at the community scale. Here, we propose using candidate genes phylogenetically-conserved across species and sustaining functional traits as an inclusive biodiversity unit transcending the intra- and interspecific boundaries. This framework merges knowledge from functional genomics and functional ecology, and we first provide conceptual and technical guidelines for identifying phylogenetically-conserved candidate genes (PCCGs) within communities, and for measuring inclusive biodiversity from PCCGs. We then explain how biodiversity measured at PCCGs can be linked to ecosystem functions, which may unify recent observations that both intra- and interspecific biodiversity are important for ecosystem functions. We then highlight the eco-evolutionary processes shaping PCCGs diversity patterns, and argue that their respective role can be inferred from concepts derived from population genetics. Finally, we explain how PCCGs may shift the field of eco-evolutionary dynamics from a focal-species approach to a more realistic focal-community approach. This framework provides a novel perspective to investigate the global ecosystem consequences of diversity loss across biological scales, and how these ecological changes further alter biodiversity evolution.
Article
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In experimental plant communities, relationships between biodiversity and ecosystem functioning have been found to strengthen over time, a fact often attributed to increased resource complementarity between species in mixtures and negative plant-soil feedbacks in monocultures. Here we show that selection for niche differentiation between species can drive this increasing biodiversity effect. Growing 12 grassland species in test monocultures and mixtures, we found character displacement between species and increased biodiversity effects when plants had been selected over 8 years in species mixtures rather than in monocultures. When grown in mixtures, relative differences in height and specific leaf area between plant species selected in mixtures (mixture types) were greater than between species selected in monocultures (monoculture types). Furthermore, net biodiversity and complementarity effects were greater in mixtures of mixture types than in mixtures of monoculture types. Our study demonstrates a novel mechanism for the increase in biodiversity effects: selection for increased niche differentiation through character displacement. Selection in diverse mixtures may therefore increase species coexistence and ecosystem functioning in natural communities and may also allow increased mixture yields in agriculture or forestry. However, loss of biodiversity and prolonged selection of crops in monoculture may compromise this potential for selection in the longer term.
Article
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Abstract The relationship between biological diversity and ecological stability has fascinated ecologists for decades. Determining the generality of this relationship, and discovering the mechanisms that underlie it, are vitally important for ecosystem management. Here, we investigate how species richness affects the temporal stability of biomass production by reanalyzing 27 recent biodiversity experiments conducted with primary producers. We find that, in grasslands, increasing species richness stabilizes whole-community biomass but destabilizes the dynamics of constituent populations. Community biomass is stabilized because species richness impacts mean biomass more strongly than its variance. In algal communities, species richness has a minimal effect on community stability because richness affects the mean and variance of biomass nearly equally. Using a new measure of synchrony among species, we find that for both grasslands and algae, temporal correlations in species biomass are lower when species are grown together in polyculture than when grown alone in monoculture. These results suggest that interspecific interactions tend to stabilize community biomass in diverse communities. Contrary to prevailing theory, we found no evidence that species' responses to environmental variation in monoculture predicted the strength of diversity's stabilizing effect. Together, these results deepen our understanding of when and why increasing species richness stabilizes community biomass.
Article
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THE functioning and sustainability of ecosystems may depend on their biological diversity1-8. Elton's9 hypothesis that more diverse ecosystems are more stable has received much attention1,3,6,7,10-14, but Darwin's proposal6,15 that more diverse plant communities are more productive, and the related conjectures4,5,16,17 that they have lower nutrient losses and more sustainable soils, are less well studied4-6,8,17,18. Here we use a well-replicated field experiment, in which species diversity was directly controlled, to show that ecosystem productivity in 147 grassland plots increased significantly with plant biodiversity. Moreover, the main limiting nutrient, soil mineral nitrogen, was utilized more completely when there was a greater diversity of species, leading to lower leaching loss of nitrogen from these ecosystems. Similarly, in nearby native grassland, plant productivity and soil nitrogen utilization increased with increasing plant species richness. This supports the diversity-productivity and diversity-sustainability hypotheses. Our results demonstrate that the loss of species threatens ecosystem functioning and sustainability.
Article
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A coordinated continental-scale field experiment across 31 sites was used to compare the biomass yield of monocultures and four species mixtures associated with intensively managed agricultural grassland systems. To increase complementarity in resource use, each of the four species in the experimental design represented a distinct functional type derived from two levels of each of two functional traits, nitrogen acquisition (N2-fixing legume or nonfixing grass) crossed with temporal development (fast-establishing or temporally persistent). Relative abundances of the four functional types in mixtures were systematically varied at sowing to vary the evenness of the same four species in mixture communities at each site and sown at two levels of seed density. Across multiple years, the total yield (including weed biomass) of the mixtures exceeded that of the average monoculture in >97% of comparisons. It also exceeded that of the best monoculture (transgressive overyielding) in about 60% of sites, with a mean yield ratio of mixture to best-performing monoculture of 107 across all sites. Analyses based on yield of sown species only (excluding weed biomass) demonstrated considerably greater transgressive overyielding (significant at about 70% of sites, ratio of mixture to best-performing monoculture = 118). Mixtures maintained a resistance to weed invasion over at least 3 years. In mixtures, median values indicate
Article
Ecological and agronomic research suggests that increased crop diversity in species-poor intensive systems may improve their provision of ecosystem services. Such general predictions can have critical importance for worldwide food production and agricultural practice but are largely untested at higher levels of diversity. We propose new methodology for the design and analysis of experiments to quantify diversity-function relationships. Our methodology can quantify the relative strength of inter-specific interactions that contribute to a functional response, and can disentangle the separate contributions of species richness and relative abundance. Applying our methodology to data from a common experiment at 28 European sites, we show that the above-ground biomass of four-species mixtures (two legumes and two grasses) in intensive grassland systems was consistently greater than that expected from monoculture performance, even at high productivity levels. The magnitude of this effect generally resulted in transgressive overyielding. A combined analysis of first-year results across sites showed that the additional performance of mixtures was driven by the number and strength of pairwise inter-specific interactions and the evenness of the community. In general, all pairwise interactions contributed equally to the additional performance of mixtures; the grass-grass and legume-legume interactions were as strong as those between grasses and legumes. The combined analysis across geographical and temporal scales in our study provides a generality of interpretation of our results that would not have been possible from individual site analyses or experimentation at a single site. Our four-species agricultural grassland communities have proved a simple yet relevant model system for experimentation and development of methodology in diversity-function research. Our study establishes that principles derived from biodiversity research in extensive, semi-natural grassland systems are applicable in intensively managed grasslands with agricultural plant species.
Article
Human-driven ecosystem simplification has highlighted questions about how the number of species in an ecosystem influences its functioning. Although biodiversity is now known to affect ecosystem productivity, its effects on stability are debated. Here we present a long-term experimental field test of the diversity–stability hypothesis. During a decade of data collection in an experiment that directly controlled the number of perennial prairie species, growing-season climate varied considerably, causing year-to-year variation in abundances of plant species and in ecosystem productivity. We found that greater numbers of plant species led to greater temporal stability of ecosystem annual aboveground plant production. In particular, the decadal temporal stability of the ecosystem, whether measured with intervals of two, five or ten years, was significantly greater at higher plant diversity and tended to increase as plots matured. Ecosystem stability was also positively dependent on root mass, which is a measure of perenniating biomass. Temporal stability of the ecosystem increased with diversity, despite a lower temporal stability of individual species, because of both portfolio (statistical averaging) and overyielding effects. However, we found no evidence of a covariance effect. Our results indicate that the reliable, efficient and sustainable supply of some foods (for example, livestock fodder), biofuels and ecosystem services can be enhanced by the use of biodiversity.
Chapter
This chapter focuses on biomass productivity of mixtures and provides a comparison of the biomass yields of mixtures with those of their components'. It discusses the types of interaction causing non-transgressive deviations of mixture yields from mid-monoculture values. The chapter discusses mechanisms causing transgressive deviation that ensure that the yield of the mixture is either less than that of the lower-yielding monoculture or more than that of the higher-yielding monoculture. Most binary mixtures have been recorded as yielding at a level between the yields of the components' monoculture. This non-transgressive yielding can be predicted on the assumption of competition among components for the same resources. Such competition leads to equal proportional increases and decreases of plant biomass compared with per-plant performance of the components in monocultures.
Article
Biodiversity regulates ecosystem functions such as productivity, and experimental studies of species mixtures have revealed selection and complementarity effects driving these responses. However, the impacts of intraspecific genotypic diversity in these studies are unknown, despite it forming a substantial part of the biodiversity.In a glasshouse experiment we constructed plant communities with different levels of barley (Hordeum vulgare) genotype and weed species diversity and assessed their relative biodiversity effects through additive partitioning into selection and complementarity effects.Barley genotype diversity had weak positive effects on aboveground biomass through complementarity effects, whereas weed species diversity increased biomass predominantly through selection effects. When combined, increasing genotype diversity of barley tended to dilute the selection effect of weeds.We interpret these different effects of barley genotype and weed species diversity as the consequence of small vs large trait variation associated with intraspecific barley diversity and interspecific weed diversity, respectively. The different effects of intra- vs interspecific diversity highlight the underestimated and overlooked role of genetic diversity for ecosystem functioning.
Article
To predict the ecological consequences of biodiversity loss, researchers have spent much time and effort quantifying how biological variation affects the magnitude and stability of ecological processes that underlie the functioning of ecosystems. Here we add to this work by looking at how biodiversity jointly impacts two aspects of ecosystem functioning at once: (1) the production of biomass at any single point in time (biomass/area or biomass/ volume), and (2) the stability of biomass production through time (the CV of changes in total community biomass through time). While it is often assumed that biodiversity simultaneously enhances both of these aspects of ecosystem functioning, the joint distribution of data describing how species richness regulates productivity and stability has yet to be quantified. Furthermore, analyses have yet to examine how diversity effects on production covary with diversity effects on stability. To overcome these two gaps, we reanalyzed the data from 34 experiments that have manipulated the richness of terrestrial plants or aquatic algae and measured how this aspect of biodiversity affects community biomass at multiple time points. Our reanalysis confirms that biodiversity does indeed simultaneously enhance both the production and stability of biomass in experimental systems, and this is broadly true for terrestrial and aquatic primary producers. However, the strength of diversity effects on biomass production is independent of diversity effects on temporal stability. The independence of effect sizes leads to two important conclusions. First, while it may be generally true that biodiversity enhances both productivity and stability, it is also true that the highest levels of productivity in a diverse community are not associated with the highest levels of stability. Thus, on average, diversity does not maximize the various aspects of ecosystem functioning we might wish to achieve in conservation and management. Second, knowing how biodiversity affects productivity gives no information about how diversity affects stability (or vice versa). Therefore, to predict the ecological changes that occur in ecosystems after extinction, we will need to develop separate mechanistic models for each independent aspect of ecosystem functioning.
Article
There is mounting evidence that biodiversity increases the stability of ecosystem processes in changing environments, but the mechanisms that underlie this effect are still controversial and poorly understood. Here, we extend mechanistic theory of ecosystem stability in competitive communities to clarify the mechanisms underlying diversity-stability relationships. We first explain why, contrary to a widely held belief, interspecific competition should generally play a destabilising role. We then explore the stabilising effect of differences in species' intrinsic rates of natural increase and provide a synthesis of various potentially stabilising mechanisms. Three main mechanisms are likely to operate in the stabilising effects of biodiversity on ecosystem properties: (1) asynchrony of species' intrinsic responses to environmental fluctuations, (2) differences in the speed at which species respond to perturbations, (3) reduction in the strength of competition. The first two mechanisms involve temporal complementarity between species, while the third results from functional complementarity. Additional potential mechanisms include selection effects, behavioural changes resulting from species interactions and mechanisms arising from trophic or non-trophic interactions and spatial heterogeneity. We conclude that mechanistic trait-based approaches are key to predicting the effects of diversity on ecosystem stability and to bringing the old diversity-stability debate to a final resolution.