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Simon PierceAlessandra LuzzaroAlessandro Ossola

Bruno Cerabolini

The use of species diversity and functional diversity as indicators of the environmental and economic value of

subalpine herbaceous communities (Foppolo – Orobie Alps)

Università degli Studi dell’Insubria, VareseUniversity of Insubria, Varese, Italy

Cattle herder’s hut (Malga)

Pasture (Prato pascolo)

Rumicion alpini Polygono-Trisetion

How do species diversity and functional diversity contribute to the value of sub-alpine pasture?

San Simone, near Foppolo, Orobie Alps, Italy

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The Polygono-Trisetion vegetation is dominated by Polygonum bistorta, but a number of grasses such as Deschampsia caespitosa and Phleum alpinum are important elements. This vegetation has fewer species, but a greater number of species that account for a significant proportion of cover.

The Rumicion alpini vegetation is strongly dominated by a single species (Rumexalpinus) and has a greater number of infrequent species (cover <1).

Species richness

Rumicion alpini

Polygono-Trisetion

Total number of species observed throughout all surveys 31 28

Number of species with cover ≥1

16.4

15

Mean number of species recorded in each survey

11

14.2

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DiversityDiversity indicesindices

Simpson’s diversity index (reciprocal) (D)

Simpson’s uniformity index (E)

Shannon’s diversity index (H)

Shannon’s uniformity index (J)

n=5

S = number of speciesPi = species relative abundance

There is greater biodiversity (richness and evenness) and uniformity in the Polygono-Trisetionvegetation according to Simpson, but no difference according to Shannon

Belowground biomass0-30 cm n=5

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Soil chemical characteristics confirm that the substrate underlying the Polygono-Trisetionvegetation is more acidic, relatively nutrient poor and has less cation exchange capacity (CEC)

n=5, Student’s t-test

Mean leaf nitrogen contents (LNC) are high for both vegetation types, but LNC is higher forRumicion alpini vegetation, and leaves are of greater nitrogen quality (lower C:N)

(Rumex alpinus has an extremely high LNC of 6.4% and accounts for 52% of the vegetation)

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The Polygono-Trisetion vegetation has a greater leaf area index (LAI): the canopy is “closed” to greater degree and intercepts more sunlight, potentially driving greater photosynthetic activity and productivity

The Polygono-Trisetion vegetation produces more biomass and a denser canopy with feweravailable mineral resources and less nitrogen in the leaves

How?

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RRegenerative ability

(rapid life cycle, survival as seeds)(disturbance = biomass destruction, affectedtissues cannot recover)

Grime J. P. 2001. Plant Strategies, Vegetation Processes and Ecosystem Properties. Second Edition. Wiley, Chichester, UK.

CControl of resource capture

SResistance of sub-optimal

periods for metabolic function

Reynoutria japonica(Competitor)Arabidopsis thaliana

(Ruderal)

The primary axes of specialisation in plants (CSR theory)

Festuca glauca(Stress-tolerator)

(stress = sub-optimal function, affectedtissues can recover)

CSR classification

Hodgson, J.G., Wilson, P.J., Hunt, R., Grime, J.P. and Thompson, K. 1999. Allocating CSR plant functional types: a soft approach to a hard problem. Oikos 85: 282-294.

The seven traits are simple and rapid to measure in situ, allowing many plants to be investigated in real vegetation

Lateral spread

Canopy height (distance from the ground to the highest laminar part)

Flowering start (onset)

Flowering period

Leaf dry matter content~investment in structure

Specific leaf area~photosynthetic tissue density

Leaf dry weight~leaf “size”

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Greater functional diversity and co-dominance by contrasting functional typessuggests that there is a greater range of niches in the Polygono-Trisetion habitat

The dominant species of both communities exhibit a “CR” strategy

Polygonumbistorta

Rumexalpinus

In the pasture there is a greater diversity of plant strategies, including a number of stress-tolerant Poaceae that co-dominate with Polygonum bistorta

Rumicion alpiniPolygono-Trisetion

Prato

Polygonumbistorta

Rumexalpinus

Most subordinate species share the strategy of profiting from the gaps and opportunities between plants of the dominant species.

The available niches for subordinatesappear to be similar.

Greater diversity reflects wider nicheoccupation.

Available resources and opportunities are fully exploited, closing the canopy and maximisingbiomass production.

Rumicion alpiniPolygono-Trisetion

Prato

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The Rumicion alpini vegetation is nitrogen-rich but is not considered as valuable as the Polygono-Trisetion vegetation: it is used as pasture once a year, during which the vegetationis effectively destroyed.

The Polygono-Trisetion vegetation is a balanced source of nitrogen and carbon, and it has a more extensive range and greater belowground biomass for the regeneration of abovegroundbiomass, meaning that it can be relied upon for sustainable exploitation.

The Rumicion alpini vegetation is an extremely rich source of nitrogen, but does not contain so much carbon (carbon-rich cellulose is a key resource needed to make milk), only occursin a small zone near the cattle herder’s hut, does not recover from grazing within the sameyear, and Rumex species contain oxalates that are toxic to cattle in large quantities.

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Conclusions:

• The value of pasture vegetation (Polygono-Trisetion) reflects the functional diversity of species occupying a greater range of niches

• Most of this biomass is invested below ground, potentially facilitating regeneration following grazing and mowing, and thus sustainable exploitation of the vegetation.

• The economic value and sustainable use of vegetation do not appear to be a function of species diversity per se, but of functional diversity and the extent to which opportunities within the habitat are exploited

Main conclusion: species diversity alone is not an ideal indicator of economic and ecological value, but knowledge of species and functional diversity (phytosociology + functional analysis) provides a highly detailed description of the vegetation and the processes that shape it.

– despite the limiting edaphic environment, functional diversity maximisesexploitation of available resources (light & nutrients), producing a greater amount of biomass that is rich in nitrogen and carbon.

Caccianiga M., Luzzaro A., Pierce S., Ceriani R.M. & Cerabolini B. 2006. The functional basis of a primary succession resolved by CSR classification. Oikos 112: 10-20.

Ceriani R.M., Pierce S. & Cerabolini B. 2008. Are morpho-functional traits reliable indicators of inherent relative growth rate for prealpine calcareous grassland species? Plant Biosystems (in press).

Pierce S., Vianelli A. & Cerabolini B. 2005. From ancient genes to modern communities: the cellular stress response and the evolution of plant strategies. Functional Ecology 19(5): 763-776.

Pierce S., Ceriani R.M., De Andreis R., Luzzaro A. & Cerabolini B. 2007. The leaf economics spectrum of Poaceae reflects variation in survival strategies. Plant Biosystems 141(3): 337-343

Pierce S., Luzzaro A., Caccianiga M., Ceriani R.M. & Cerabolini B. 2007. Disturbance is the principal α-scale filter determining niche differentiation, coexistence and biodiversity in an alpine community. Journal of Ecology 95: 698-706.

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Il progetto di ricerca è stato finanziato dal Centro Flora Autoctona della Regione Lombardia

Il Centro Flora Autoctona è un Ente Regionale gestito dal Parco Monte Barro (LC), che promuove lo studio, la conservazione e la coltivazione di piante autoctone lombarde a fini conservazionistici e per interventi di ingegneria naturalistica.Visita il sito internet: http://centroflora.parcobarro.it