I. Rábago, V. Bermejo, H. Calvete, S. Elvira, J. Sanz,

I. González-Fernández, H. García, F. Valiño, R. Alonso

Ozone, nitrogen and climate effects

on annual Mediterranean pastures

biodiversity and structure

1st Joint session EMEP/WGE

September 2015, Geneva

CLRTAP

Objectives

• Present results

• About O3-N-Climate interactions

• On mediterranean pastures

• AOT40 vs POD

From accumulated concentration to effective dose

• Mediterranean pastures characteristics

• Field research results: OTC (O3 + N)

• O3 interactions with climate

• Conclusions (Effects &Modelling)

Content

Annual Mediterranean pastures

November May July August

• Common Mediterranean landscape

• High biodiversity: Natura 2000

• Annual growth - dry out cycle from soil seed bank

Habitats directive 6310 – Dehesas Quercus spp

Habitats directive 6220 – Pseudosteppe grasses annuals

Annual Mediterranean pastures

EEA

• High O3 concentrations

• N deposition hot spots

mg N ha-1 yr-1 EMEP

O3 – AOT40 (µg m-3 h) N – Total dep. (mg m-2 y-1)

• High inter-annual variability meteorological conditions

• Soil moisture: Key variable for growth and spp composition

Annual Mediterranean pastures

Days since 01/01/09

González-Fernández et al. In preparation

• Open-top Chamber experiments, 6 years, 2 sites

• 21 species tested: grasses, legumes and non-legume

herbs, including species mixtures

• O3 exposure combined with N fertilization

• Response variables: growth parameters, pasture quality,

reproductive capacity, canopy composition

O3 and N effects: OTC experiments

O3 and N Interactions on annual pasture

**

*

**

ns

ns

**

Calvete-Sogo et al., Oecology, accepted with revision

Three different patterns

Clovers: more negatively O3-sensitive;

Legume non clover: positively O3-sensitive;

Non legumes: more N-responsive and

moderately O3-sensitive)

Important role of the competition

within the legume family regarding

O3 response

Ornithopus increase biomass under O3

exposure when in competition with O3-

sensitive species

Heterogeneous responses of the component species that

can affect: Structure & composition; Biodiversity; Quality

O3 and N effects annual Med pastures

• O3 effects on species composition

FA NFA NFA+ NFA++

Calvete-Sogo et al., Oecology, accepted with revision

O3 and N effects annual Med pastures

250

300

350

400

450

500

N0 N20 N40

g d

w m

-2FANFANFA+20NFA+40

• O3 reduces fertilization effect of N

Calvete-Sogo et al., 2014

YIELD /CANOPY

SCALE:

O3 limited the

fertilization effect

of the soil N

availability,

Higher N could

compensate O3

effects on yield

only when

concentrations

were moderate,

but not under high

O3 levels

O3 interaction with climate

Climatic conditions change annual pastures sensitivity to O3: • Gas exchange rates

• Changing growing seasons

• Change in species composition with varying O3 sensitivity

(legumes generally more O3 sensitive)

HUMID YEAR

Growing season 7 Oct – 19 July

T (year) = 14.0 ºC

Rain = 457 l m-2

Legumes most abundant (52%)

[O3] (canopy) = 28.7 ppb

AOT40 (3 months) = 9840 ppb.h

DRY YEAR

Growing season 28 Oct – 7 June

T (year) = 14.3 ºC

Rain = 215 l m-2

Dominated by grasses (94%)

[O3] (canopy) = 29.4 ppb

AOT40 (3 months) = 9573 ppb.h

O3 interaction with climate • Green biomass and stomatal conductance vary across years

Humid year

Dry year

MEDPAS -Modelled Field data (mean±SD)

Dry years less yield + low O3 absorption + more tolerant species (grasses) = less risk

González-Fernández et al. In preparation

Running cumulative AOT40, 45 days

O3 interaction with climate

• Maximum physiological activity not during highest O3

level season

Humid year HIGH RISK

Dry year HIGH RISK

O3 Critical level

Running cumulative POD1 of 45 days

O3 interaction with climate

• Soil Moisture is CRITICAL in (EMEP) O3 Modelling

Empirical Critical level

Humid year HIGH RISK

Dry year LOW RISK

Conclusions

• O3 x N x Climate interactions have been identifed

• O3 reduces fertilization effect of N, and N can compensate for

O3 effects

• O3 and N can affect annual Mediterranean pastures structure

and diversity through changes in plant to plant relationships

• Direction of change due to O3 x N will depend on O3 and N

deposition levels and species composition of the pasture

(management, climate, soil, etc)

• From AOT40 to POD for a better risk analysis

• POD model: effective dose; climate (change) conditions

• Soil Moisture is critical in (EMEP) O3 Modelling (POD)

Field Research

Modelling

Effe

cts

A

tmo

sp

he

ric

Conclusions

Climate O3 effects N effects

HUMID year (more legumes)

Higher O3 flux

More O3 sensitive spp Less N sensitive spp

DRY year (more grasses)

Lower O3 flux

Less O3 sensitive spp More N sensitive spp

Future climate: more arid climate will result in

reduced pasture productivity and quality and more

important N effects than O3 effects compared to

current conditions

Thank you for your

attention!