I am an Academy of Finland Research Fellow working at the University of Helsinki (Sept 2013 - Sept 2018).
I have a with a Kone Foundation experienced researcher grant to carry out the project, "How does the spectrum of radiation penetrating forests canopies change with latitude and how does this change influence understorey phenology through interactions with other environmental factors."
I am a member of the EU Cost Action UV4Growth, reviewing the effects of UV-B radiation on plant morphology and on flavonoid accumulation and function.
I study the effects of light quality signals on plant ecophysiology in collaboration with Pedro J Aphalo (Sensory photobiology and ecophysiology of plants - SenPEP) and Heikki Hänninen (Plant Ecophysiology and Climate Change Group - PECC).
Abstract: Subalpine grasslands are highly seasonal environments and likely subject to strong variability in nitrogen (N) dynamics. Plants and microbes typically compete for N acquisition during the growing season and particularly at plant peak biomass. During snowmelt, plants could potentially benefit from a decrease in competition by microbes because of greater plant N uptake associated with active growth and freeze-thaw cycles restricting microbial growth. In managed subalpine grasslands, we expect these interactions to be influenced by recent changes in agricultural land-use, and associated modifications in plant and microbial communities. At a subalpine grassland site in the Central French Alps, a pulse of 15N was added to the soil at the end of snowmelt, allowing us to compare the dynamics of inorganic N uptake in plants and microbes during this period with that previously reported at the peak biomass in July. In all grasslands, specific plant (per g of biomass) dissolved inorganic N (DIN) uptake was two to five times greater at snow-melt than at peak biomass, whereas the specific microbial DIN uptakes were similar between the two sampling dates. On an area basis, plant communities took more DIN than microbial communities at the end of snowmelt, and the intensity of this DIN uptake by plants differed across land use types. Consequently, N partitioning after snowmelt switches in favor of plant communities allowing them to support their growing capacities at this period of the year. Seasonal differences in microbial and plant N-related dynamics were also affected by past (terraced vs. unterraced) rather than current (mown vs. unmown) land use. In terraced grasslands, microbial biomass N remained similar across seasons, whereas in unterraced grasslands, microbial biomass N was higher and microbial C : N lower at the end of snowmelt as compared to peak biomass. Further investigations on microbial community composition and their organic N uptake dynamics are required to better understand the decrease in microbial DIN uptake.
Abstract: European beech (Fagus sylvatica) reaches the south-western limit of its distribution in northern Spain, beyond which the Mediterranean climate is thought to restrict further expansion of the species range. Consequently, current and future climate change in the region is expected to push back the range margin and threaten the survival of local beech populations. In a provenance trial of pan-European beech populations growing under harsh conditions in La Rioja, we tested whether associations between the timing of spring phenology assessed over three years affected the performance of beeches at the site, and whether they exhibited a trade off between growth rate and survival. In particular, we considered whether the relationship between performance under conditions of summer drought and spring frost at the trial site was dependent on the climate at the site of provenance origin. We report that early-flushing provenances from continental climates in the south-east and parts of central Europe were among the tallest after ten years of growth in the trial: for instance from Val di Sella, northern Italy (mean bud burst day 114 and height 173 cm); Gotze Delchev, Bulgaria (day 115, height 135 cm); and Aarberg, Switzerland (day 118, height 151 cm). While late-flushing provenances from maritime climates in northern and western Europe were among the shortest in the trial: for instance from Soignes, Belgium (day 124, height 73 cm); Gullmarsberg, Sweden (day 122, height 69 cm); and Bathurst Estate, southern England (day 122, height 85 cm). There was no evidence that early flushing increased the mortality of trees at the trial site. The large-scale geographical patterns in flushing strategy reflected a trade off between pre-emptive growth before the summer drought and susceptibility to late frosts. Our findings emphasise the need to conserve populations from the range edge in the south of Europe, the Balkans and western Alps, whose combination of early flushing and drought resistance may become desirable traits for the improved future performance of beech in response to climate change.
Abstract: Patterns of intraspecific variation in functional traits have been widely studied across plant species to find
out what general suites of traits provide functional advantage under specific environmental conditions.
Much less is known about this variation within tree species and, in particular, about its relationship with
performance variables such as photosynthetic rates under water deficit. Nevertheless, this knowledge is
fundamental to understand the adaptive potential of drought sensitive tree species to increased aridity
as predicted in the context of climate change.
Intraspecific variation in photosynthetic performance and other leaf functional traits in response to
water availability were examined in a glasshouse experiment using seedlings of six European beech
populations. The physiological response of seedlings to a “water stress†treatment was compared to a
“control†treatment along an experimental cycle of progressive soil water deficit and recovery. We found
evidence of intraspecific variation in beech’s photosynthetic performance and other leaf functional traits
in response to water availability. We also detected intraspecific variation in leaf-level tolerance of water
deficit and phenotypic plasticity to water availability suggesting a pattern shaped by both regional and
local scale effects. The Swedish population was particularly sensitive to water deficit, being the only
population showing impaired photochemical efficiency under the experimental water deficit. Leaf-level
tolerance of water deficit was related to PNUE, but not to other functional traits, such as WUE, SLA or
leaf nitrogen content, that have been described to vary across species in adaptation to drought tolerance.
Our results support the idea that general trends for variation in functional traits across species do not
necessarily reflect a similar pattern when observed at the intraspecific level. The observed functional
variation between beech populations reaffirms the importance of local adaptation to water deficit in the
context of climate change.
Abstract: Lolium perenne (cv. AberDart) was grown at 14 locations along a latitudinal gradient across Europe (37-68°N) to study the impact of ultraviolet radiation (UV) and climate on aboveground growth and foliar UV-B absorbing compounds. At each location, plants were grown outdoors for 5 weeks in a replicated UV-B filtration experiment consisting of open, UV-B transparent (cellulose diacetate) and UV-B opaque (polyester) environments. Fourier transform-infrared spectroscopy was used to compare plant metabolite profiles in relation to treatment and location. UV radiation and climatic parameters were determined for each location from online sources and the data were assessed using a combination of anova and multiple regression analyses. Most of the variation in growth between the locations was attributable to the combination of climatic parameters, with minimum temperature identified as an important growth constraint. However, no single environmental parameter could consistently account for the variability in plant growth. Concentrations of foliar UV-B absorbing compounds showed a positive trend with solar UV across the latitudinal gradient; however, this relationship was not consistent in all treatments. The most striking experimental outcome from this study was the effect of presence or absence of filtration frames on UV-absorbing compounds. Overall, the study demonstrates the value of an European approach in studying the impacts of natural UV across a large latitudinal gradient. We have shown the feasibility of coordinated UV filtration at multiple sites but have also highlighted the need for open controls and careful interpretation of plant responses.
Abstract: Recent molecular and physiological studies have demonstrated that
ultraviolet-B radiation (UV-B) can affect some of the processes involved in leaf
growth, but the phases of leaf growth affected have not been clearly delimited.
We used functional growth analysis to assess the effects of UV-B radiation on
the time course of leaf growth in seedlings of two birch species (Betula pendula
and Betula pubescens). Our aim was to identify the phase(s) of leaf development
affected by UV-B radiation. In a greenhouse study, 1-year-old birch
seedlings were subjected to three daily doses of supplemental UV-B radiation
treatments (UV-B+) and no UV-B radiation controls (UV-B−). Leaf growth
measurements every 2 days were complemented by assessment of other
functional traits over a 4-week period at the start of the growing season. Using
fitted curves, we were able to determine that the rate of leaf expansion was
slowed by the UV-B+ treatment in leaves of B. pendula because of a slower
maximum leaf growth rate compared with plants under the UV-B− controls,
but that compensation toward the end of the period of expansion negated this
difference when leaves reached their final size. UV-B+ had little effect on the
rate of B. pubescens leaf growth despite a larger reduction in leaf final size
due to UV-B+ than occurred in B. pendula leaves. In conclusion, effective
regulation ameliorated the effects of UV-B radiation on leaf and seedling
growth in B. pendula, whereas in B. pubescens, reductions in leaf final size
under UV-B+ were consistent with a slightly reduced rate of height growth.
Abstract: Atmospheric nitrogen (N) deposition
increasingly impacts remote ecosystems. At high
altitudes, snow is a key carrier of water and nutrients
from the atmosphere to the soil. Medium-sized subalpine
grassland terraces are characteristic of agricultural
landscapes in the French Alps and influence
spatial and temporal snow pack variables. At the
Lautaret Pass, we investigated snow and soil characteristics
along mesotopographic gradients across the
terraces before and during snowmelt. Total N concentrations
in the snowpack did not vary spatially and were
dominated by organic N forms either brought by dry
deposition trapped by the snow, or due to snowmicrobial
immobilization and turnover. As expected,
snowpack depth, total N deposited with snow and
snowmelt followed the terrace toposequence; more
snow-N accumulated towards the bank over longer
periods. However, direct effects of snow-N on soil-N
cycling seem unlikely since the amount of nitrogen
released into the soil from the snowpack was very small
relative to soil-N pools and N mineralization rates.
Nevertheless, some snow-N reached the soil at thaw
where it underwent biotic and abiotic processes. In situ
soil-N mineralization rates did not vary along the
terrace toposequence but soil-N cycling was indirectly
affected by the snowpack. Indeed, N mineralization
responded to the snowmelt dynamic via induced
temporal changes in soil characteristics (i.e. moisture
and T) which cascaded down to affect N-related
microbial activities and soil pH. Soil-NH4 and DON
accumulated towards the bank during snowmelt while
soil-NO3 followed a pulse-release pattern. At the end
of the snowmelt season, organic substrate limitation
might be accountable for the decrease in N mineralization
in general, and in NH4 ? production in particular.
Possibly, during snowmelt, other biotic or abiotic
processes (nitrification, denitrification, plant uptake,
leaching) were involved in the transformation and
transfer of snow and soil-N pools. Finally, subalpine
soils at the Lautaret Pass during snowmelt experienced
strong biotic and abiotic changes and switched
between a source and a sink of N.
Abstract: Seasonal variations and the differential effect of drought on photosynthetic parameters involved in carbon assimilation in forest species have been poorly studied under natural conditions. Limitations to diffusion and biochemical factors affecting leaf carbon uptake were analyzed in young beech seedlings (Fagus sylvatica L.) growing in natural gaps of a beech-wood at the southern limit of the species. Half of the seedlings received periodic watering in addition to natural rainfall to reduce the severity of the summer drought which is typical in the area. Plant water status was evaluated by measuring predawn water potential. Basic biochemical parameters were inferred from photosynthesis-CO2 curves (A-Cc) under saturating light and chlorophyll fluorescence. The curves were established from data collected on three dates during the summer months. The main variables studied included: stomatal and mesophyll conductance to CO2 (gs and gm respectively), maximum velocity of carboxylation (Vcmax) and maximum electron transport capacity (Jmax). The gm was estimated by two methodologies: the curve-fitting and J constant methods.
Seedlings withstood moderate water stress as the leaf predawn water potential (Ψpd) measured during the study was within the range -0.2 to -0.5 MPa. Mild drought caused gs and gm to decrease only slightly in response to Ψpd. However both diffusional parameters explained most of the limitations to CO2 uptake. Furthermore, non-stomatal limitations were also important, since they limited net photosynthesis as water stress increased. In addition, it should be highlighted that biochemical limitations, prompted by Vcmax and Jmax, were related mainly to ontogenic factors, without any clear relationship with drought under the moderate water stress experienced by beech seedlings through the study.
The results may help to further understanding of the functional mechanisms influencing the carbon fixation capacity of beech seedlings. This capacity may influence the total carbon balance of beech seedlings, and feed forward to impact on their growth and survival in drought-prone environments such as those in the south of Europe.
Abstract: The interactive effects of photosynthetically active radiation (PAR) on plants’ acclimation to ultraviolet
(UV) radiation were examined under field conditions in two barley varieties (Barke, Bonus). Plants,
pre-treated under UV exclusion and low PAR intensities, were subsequently exposed to four radiation
treatments representing the combination of low [−] and high [+] UV and PAR intensities. Selective UV
and PAR filters were used for UV exclusion and reduction of PAR to ca 25% of ambient irradiance. A system
of modulated lamps was used to enhance UV to ca 200% of ambient.
Changes in flavonol and chlorophyll content, chlorophyll fluorescence, gas-exchange and leaf hyperspectral
reflectance were studied during seven days of acclimation to the new treatments. At the end of
this period morphological analysis of aboveground biomass was carried out.
The [UV+PAR−] treatment significantly reduced the photosynthetic activity of barley leaves; the reduction
was more pronounced in old than young leaves and greater in the variety Barke than Bonus. Whereas,
[PAR+] treatment triggered photoprotective mechanisms which partially ameliorated the UV effects
on photochemistry and carbon assimilation. The [PAR+] treatment induced accumulation of flavonols,
mainly in young leaves, whereas in old leaves UV-induced accumulation was more pronounced. An
inverse proportion was found between flavonol content and specific leaf area irrespective of barley variety
and UV/PAR treatment. Enhanced UV radiation reduced the final leaf length, particularly in [PAR−]
plants, in young leaves and in variety Barke. However, [PAR+] mitigated the morphological effects induced
by the [UV+] treatment, particularly changes in SLA.
Abstract: We assessed the response of 11-year-old saplings
from six beech provenances growing in a common-garden
trial at the southwestern range limit. Provenances from
distinct climatic regions across the European beech distribution
were selected. The local Spanish provenance appeared
well suited to the site conditions, maintaining high rates of
assimilation even in midsummer, but so did the provenance of
southern continental origin, from Gotze-Delchev, Bulgaria.
Those provenances from cooler sites in central Europe, a
continental mountain climate in the Czech Republic and a
continental range-edge site in eastern Poland, along with a
German provenance of mild maritime origin, had good physiological
functionality in early summer but reduced carbon
assimilation (Aarea) and apparent soil–leaf hydraulic conductivity
(KL) in midsummer. The northern maritime provenance
from Sweden demonstrated severely-reduced photosynthetic
capacity. These groupings of provenances according to their
photosynthetic performance, stable carbon isotope composition
(δ13C; a proxy for water-use efficiency) and leaf water
potential under marginal conditions, during late summer in the
trial, suggest that they have divergent strategies for water use.
The research highlights large intraspecific differences among
beech provenances of distinct origin and strategies which are
expected to modify their response to drought, requiring future
genetic studies to explicitly determine the basis of this ecophysiological
differentiation.
Abstract: Aim To assess the effect of local adaptation and phenotypic plasticity on the
potential distribution of species under future climate changes. Trees may be
adapted to specific climatic conditions; however, species range predictions have
classically been assessed by species distributionmodels (SDMs) that do not account
for intra-specific genetic variability and phenotypic plasticity, because SDMs rely
on the assumption that species respond homogeneously to climate change across
their range, i.e. a species is equally adapted throughout its range, and all species are
equally plastic. These assumptions could cause SDMs to exaggerate or underestimate
species at risk under future climate change.
Location The Iberian Peninsula.
Methods Species distributions are predicted by integrating experimental data
and modelling techniques. We incorporate plasticity and local adaptation into a
SDM by calibrating models of tree survivorship with adaptive traits in provenance
trials. Phenotypic plasticity was incorporated by calibrating our model with
a climatic index that provides a measure of the differences between sites and
provenances.
Results We present a new modelling approach that is easy to implement and
makes use of existing tree provenance trials to predict species distribution models
under global warming. Our results indicate that the incorporation of intrapopulation
genetic diversity and phenotypic plasticity in SDMs significantly altered
their outcome. In comparing species range predictions, the decrease in area occupancy
under global warming conditions is smaller when considering our survival–
adaptationmodel than that predicted by a ‘classical SDM’ calibrated with presence–
absence data. These differences in survivorship are due to both local adaptation and
plasticity. Differences due to the use of experimental data in the model calibration
are also expressed in our results: we incorporate a nullmodel that uses survival data
from all provenances together. This model always predicts less reduction in area
occupancy for both species than the SDM calibrated with presence–absence.
Main conclusions We reaffirm the importance of considering adaptive traits
when predicting species distributions and avoiding the use of occurrence data as a
predictive variable. In light of these recommendations, we advise that existing
predictions of future species distributions and their component populations must
be reconsidered.
Abstract: Little is known about how environmental factors
shape the short- and long-term responses of leaf respiration to
temperature under field conditions despite the importance of
respiration for plant and stand carbon balances. Impacts of
water availability and canopy cover on leaf dark respiration
(R) and temperature sensitivity were assessed in beech (Fagus
sylvatica L.) seedlings in a sub-Mediterranean population.
We studied seedlings established within canopy gaps
(39% global site factor; GSF) that were subject to either no
watering (unwatered plants; UW) or regular watering (2–
10% higher volumetric topsoil water content as summer progressed;
W plants) and seedlings established beneath the adjacent
understorey (12% GSF). Leaf R rose exponentially
with diurnal increases in temperature; the same temperature
sensitivity (Q10: 2.2) was found for understorey and gap
plants, irrespective of watering treatment. Respiration estimated
at 25 °C (R25) was lower in the understorey than the
gaps and was significantly lower in the unwatered than in the
watered gap plants by the end of summer (0.65 versus 0.80
μmol m−2 s−1). R25 declined with increasing summer temperature
in all plants; however, respiration estimated at the prevailing
ambient temperature did not change through the
summer. There were parallel declines in R25 and concentrations
of starch and soluble sugars with increasing summer temperature
for gap plants. We conclude that seasonal shifts in
temperature–response curves of beech leaf R occur in both
low- and high-light environments; since leaf R decreased with
increasing plant water deficit, such shifts are likely to be greater
whenever plants experience summer drought compared to
scenarios where plants experience high rainfall in summer.
Abstract: 1. Nitrogen (N) cycling is a key process determining ecosystem functioning in subalpine grasslands
where traditional mowing and manuring are being abandoned. However, the roles of the plant and
microbial communities in mediating changes inNavailability are still poorly understood.
2. We inoculated 15 subalpine grassland fields with dual-labelled ammonium nitrate (15NH4 + ,
15NO3
)) during July 2005 and used pool dilutions over 1 month to calculate inorganic N fluxes into
the microbial pool and uptake in plant communities by grasses, forbs and legumes. The effects of
current land abandonment were assessed by comparing manured and mown terraces (ancient croplands)
with other terraces where these practices have ceased, and mown versus unmown unterraced
meadows.
3. Rapid cycling of inorganicNand high soilNavailability in forb-dominated manured and mown
terraces resulted from fast plant N uptake and low microbial C:N ratio. In grass-dominated
unmown terraces, N cycling was slower and N retention was greater; microbial N uptake remained
similar to that in the other terraces, although a higher C:N ratio suggested a shift towards fungal
dominance.
4. In unterraced meadows, pH was low due to reduced mixing of soil with the underlying calcareous
rock. Soil [NH4 + ] was high and [NO3 ) ] low, but current management had no effect on N pool
size, although plant N uptake was greater in the mown than unmown fields. This may be partially
explained by high N retention by dominant Festuca paniculata tussocks. The microbial N pool and
N uptake were both low and the microbial C:N ratio was high, suggesting that fungi slowed N
cycling and reduced the influence of mowing onNturnover.
5. Synthesis. In these marginal long-term grasslands, with low productivity and high biodiversity
value, changes in ecosystem function associated with reduced management intensity were mediated
through slowerN cycling. This response was expressed as more gradual nutrient uptake but greater
retention by unmown plant communities, slower microbial uptake and smaller soilNpools. In contrast
to more productive ecosystems, such as north-western European grasslands, reduced management
is detrimental to both biodiversity and the maintenance of soil-related ecosystem services.
These costs will need to be balanced against potential benefits, such as carbon storage.
Abstract: Land use and climate changes induce shifts in plant functional diversity and
community structure, thereby modifying ecosystem processes. This is particularly true for
litter decomposition, an essential process in the biogeochemical cycles of carbon and nutrients.
In this study, we asked whether changes in functional traits of living leaves in response to
changes in land use and climate were related to rates of litter potential decomposition,
hereafter denoted litter decomposability, across a range of 10 contrasting sites.
To disentangle the different control factors on litter decomposition, we conducted a
microcosm experiment to determine the decomposability under standard conditions of litters
collected in herbaceous communities from Europe and Israel. We tested how environmental
factors (disturbance and climate) affected functional traits of living leaves and how these traits
then modified litter quality and subsequent litter decomposability.
Litter decomposability appeared proximately linked to initial litter quality, with
particularly clear negative correlations with lignin-dependent indices (litter lignin concentration,
lignin : nitrogen ratio, and fiber component).
Litter quality was directly related to community-weighted mean traits. Lignin-dependent
indices of litter quality were positively correlated with community-weighted mean leaf dry
matter content (LDMC), and negatively correlated with community-weighted mean leaf
nitrogen concentration (LNC). Consequently, litter decomposability was correlated negatively
with community-weighted mean LDMC, and positively with community-weighted mean LNC.
Environmental factors (disturbance and climate) influenced community-weighted mean
traits. Plant communities experiencing less frequent or less intense disturbance exhibited higher
community-weighted mean LDMC, and therefore higher litter lignin content and slower litter
decomposability. LDMC therefore appears as a powerful marker of both changes in land use
and of the pace of nutrient cycling across 10 contrasting sites.
Abstract: Refugia of mixed beech forest persist in the
central mountains of the Iberian Peninsula at the southwestern
limit of European beech (Fagus sylvatica L.)
distribution. The lack of beech regeneration is a concern
in this region that has experienced reduced rainfall and
higher temperatures over the past 30 years. Beech is
considered especially susceptible to climate change because
of its conservative shade-tolerant growth strategy; hence
seedling responses to drought stress in gaps and in the
understory are of particular interest. During the summer of
2007, a watering treatment raised the soil water content by
up to5%in gap and understory plots of beech seedlings in a
mixed beech forest. Root-collar diameter was increased by
our watering treatment in understory seedlings. Neither
drought-avoidance through stomatal closure nor physiological
drought-tolerance mechanisms were able to mitigate
the effects of water stress in the understory seedlings,
whereas osmotic adjustment enhanced the ability of the gap
seedlings to tolerate water stress. Overall, high photosynthetic
rates in the gaps, despite the photoinhibitory effects
of high radiation, allowed gap seedlings to survive and
grow better than the understory seedlings irrespective of
water availability. Our results indicate that further intensification
of summer drought, predicted for the Iberian
Peninsula, will hinder the establishment of a beech seedling
bank in the understory because of the conflicting seedling
trait responses to simultaneously withstand water stress
and to tolerate shade.
Abstract: This study was designed to test the hypothesis that the spectral composition of incident radiation, as defined by the
relative proportions of blue (B; λmax = 455 nm) and red (R; λmax = 625 nm) photons, can affect photosynthetic induction,
since B photons stimulate stomatal opening and are more effectively absorbed by leaves than R photons. Different stages
of photosynthetic induction, primarily determined by the photo-modulation of Rubisco activity and stomata opening,
were investigated in dark-adapted leaves of Fagus sylvatica transferred to saturating irradiance [800μmol(photon)
m–2 s–1] at B/R ratios of 1/3, 1/1, or 3/1.
In agreement with our hypothesis, photosynthesis was induced faster by irradiance with a high B/R ratio (3/1); as
demontrated by a higher IS60 (induction state 60 s after leaf illumination) and lower T90 (the time period required to
reach 90 % of maximum steady-state photosynthesis). However, there were no differences in induction between leaves
receiving equal (1/1) and low (1/3) B/R ratios. Electron transport was highly sensitive to radiation quality, exhibiting
faster induction kinetics with increasing B/R ratio. Such stimulation of carbon-assimilatory processes corresponds with
faster activation of Rubisco and lower non-photochemical quenching (NPQ) as the proportion of B photons is increased.
In contrast, the kinetics of stomatal opening was independent of the spectral composition of incoming radiation. Since
slightly higher absorption efficiency of high B/R radiation does not fully explain the changes in induction kinetics, the
other possible mechanisms contributing to the stimulation of electron transport and Rubisco activity are discussed.
Abstract: • In subalpine grasslands, changes in abiotic conditions with decreased management
intensity alter the functional composition of plant communities, leading to modifications
of ecosystem properties. Here, it is hypothesized that the nature of plant
feedbacks on soil moisture is determined by the values of key traits at the community
level.
• As community functional parameters of grasslands change along a gradient
of land uses, those traits that respond most to differences in abiotic conditions
produced by land use changes were identified. A vegetation removal experiment
was then conducted to determine how each plant community affected soil moisture.
• Soil moisture was negatively correlated with community root length and positively
correlated with canopy height, whereas average leaf area was associated with
productivity. These traits were successfully used to predict the effects on soil moisture
of each plant community in the removal experiment. This result was validated using
data from an additional set of fields.
• These findings demonstrate that the modification of soil moisture following land
use change in subalpine grasslands can be mediated through those plant functional
traits that respond to water availability.
Notes: Associated Commentary Available: Katharine N. Suding and Leah J. Goldstein.
Testing the Holy Grail framework: using functional traits to predict ecosystem change. New Phytologist (2008) 180: 559–562
Abstract: Climate change is expected to involve morefrequent
and intense summer droughts in the Mediterranean
region. This represents a threat for long-term
persistence of woody species, such as European holly (Ilex
aquifolium), that originated under humid climates during
the Tertiary period. The capacity of this species to persist
under increased water stress, both in gaps and in the
understory of an oak-dominated woodland, was assessed by
quantifying phenotypic plasticity in response to drought
and shade. Physiological responses in plant-water relations
and gas exchange were used as performance indicators
under the different environments. Phenotypic plasticity of
drought-stressed holly trees in response to changes in the
light environment was low relative to the known response
of co-occurring forest trees. Differences between morphological
traits (e.g. specific leaf area and leaf: sapwood ratio
in twigs) of sun- and shade-grown trees were small but
significant while physiological traits were largely unresponsive
to light availability. This supports the hypothesis
that late-successional shade-tolerant species exhibit greater
morphological than physiological plasticity. Sapling
acclimation capacity through physiological mechanisms
such as osmotic adjustment was insufficient to protect from
summer drought. Holly mainly inhabits oceanic climates
where extreme temperatures and droughts are unusual. Our
results suggest that the species occupies a narrowing niche
in continental Mediterranean habitats, and may lack the
capacity to persist under more-severe future climate scenarios
because of its low phenotypic plasticity in response
to light and drought stresses.
Abstract: †Background and Aims A standardized methodology to assess the impacts of land-use changes on vegetation and
ecosystem functioning is presented. It assumes that species traits are central to these impacts, and is designed to
be applicable in different historical, climatic contexts and local settings. Preliminary results are presented to show
its applicability.
†Methods Eleven sites, representative of various types of land-use changes occurring in marginal agro-ecosystems
across Europe and Israel, were selected. Climatic data were obtained at the site level; soil data, disturbance and nutrition
indices were described at the plot level within sites. Sixteen traits describing plant stature, leaf characteristics
and reproductive phase were recorded on the most abundant species of each treatment. These data were combined
with species abundance to calculate trait values weighed by the abundance of species in the communities. The ecosystem
properties selected were components of above-ground net primary productivity and decomposition of litter.
†Key Results The wide variety of land-use systems that characterize marginal landscapes across Europe was
reflected by the different disturbance indices, and were also reflected in soil and/or nutrient availability gradients.
The trait toolkit allowed us to describe adequately the functional response of vegetation to land-use changes, but
we suggest that some traits (vegetative plant height, stem dry matter content) should be omitted in studies involving
mainly herbaceous species. Using the example of the relationship between leaf dry matter content and aboveground
dead material, we demonstrate how the data collected may be used to analyse direct effects of climate and
land use on ecosystem properties vs. indirect effects via changes in plant traits.
†Conclusions This work shows the applicability of a set of protocols that can be widely applied to assess the
impacts of global change drivers on species, communities and ecosystems.
Abstract: Global environmental change affects the sustained provision of a
wide set of ecosystem services. Although the delivery of ecosystem
services is strongly affected by abiotic drivers and direct land use
effects, it is also modulated by the functional diversity of biological
communities (the value, range, and relative abundance of functional
traits in a given ecosystem). The focus of this article is on
integrating the different possible mechanisms by which functional
diversity affects ecosystem properties that are directly relevant to
ecosystem services. We propose a systematic way for progressing
in understanding how land cover change affects these ecosystem
properties through functional diversity modifications. Models on
links between ecosystem properties and the local mean, range, and
distribution of plant trait values are numerous, but they have been
scattered in the literature, with varying degrees of empirical
support and varying functional diversity components analyzed.
Here we articulate these different components in a single conceptual
and methodological framework that allows testing them in
combination. We illustrate our approach with examples from the
literature and apply the proposed framework to a grassland
system in the central French Alps in which functional diversity, by
responding to land use change, alters the provision of ecosystem
services important to local stakeholders. We claim that our framework
contributes to opening a new area of research at the interface
of land change science and fundamental ecology.
Abstract: Nitrogen (N) availability in grasslands varies with agricultural land use. Traditional management regimes of mowing for hay and
manuring in subalpine meadows maintain plant communities with exploitative functional strategies suited to fertile soils with fast
turnover of nutrients. We investigated whether the neglect of traditional practices has led to a reduction in N availability in two parallel
ecosystems (terraced and unterraced fields). Soil nitrate and ammonium contents were assessed using soil cores and ion exchange resins
over a 1-year period, and assays of microbial nitrifying and denitrifying enzyme activities, made early in the growing season. A large
difference in pH between the two ecosystems, caused by historical ploughing, facilitated greater N availability in terraced than unterraced
fields. Abandonment of manuring and mowing caused a reduction in N availability and N transformation processes, which correlated
with a shift in the plant community towards more-conservative functional strategies and greater dominance by grasses. We propose that
positive feedback between the grassland management regime and dominant plant functional strategy maintained high N availability in
these managed subalpine grasslands. When traditional practices of mowing and manuring are neglected, direct management effects
combined with the spread of grass species with conservative strategies force down N availability in the soil, reduce microbial activity,
change the pH, and lead to a long-term loss of characteristic herbaceous subalpine-meadow species.
Abstract: As a result of stratospheric ozone depletion, more solar ultraviolet-B radiation (UV-B,
280–315 nm) is reaching the Earth’s surface. Enhanced levels of UV-B may, in turn, alter
ecosystem processes such as decomposition. Solar UV-B radiation could affect
decomposition both indirectly, by changes in the chemical composition of leaves during
growth, or directly by photochemical breakdown of litter and through changes in
decomposer communities exposed to sunlight. In this experiment, we studied indirect
and direct effects of solar UV-B radiation on decomposition of barley (Hordeum vulgare).
We used barley straw and leaf litter grown under reduced UV-B (20% of ambient UV-B)
or under near-ambient UV-B (90% of ambient UV-B) in Buenos Aires, Argentina, and
decomposed the litter under reduced or near-ambient solar UV-B for 29 months in Tierra
del Fuego, Argentina.
We found that the UV-B treatment applied during growth decreased the decay rate. On
the other hand, there was a marginally significant direct effect of elevated UV-B during
the early stages of decomposition, suggesting increased mass loss. The effect of UV-B
during growth on decomposition was likely the result of changes in plant litter chemical
composition. Near-ambient UV-B received during plant growth decreased the concentrations
of nitrogen, soluble carbohydrates, and N/P ratio, and increased the concentrations
of phosphorus, cellulose, UV-B-absorbing compounds, and lignin/N ratio. Thus,
solar UV-B radiation affects the decomposition of barley litter directly and indirectly,
and indirect effects are persistent for the whole decomposition period.
Abstract: The peatlands of Tierra del Fuego are subject to increased solar ultraviolet-B radiation (UV-B) due to the influence of the Antarctic ‘ozone
hole’. Research into the effects of climate change and ozone depletion on peatlands has predominantly focused on the higher plant
community and neglected other organisms. In the second 3-year portion of a 6-year experiment, we intensified our investigations of the
response of the peatland surface microfaunal community to current and attenuated solar UV-B, and assessed possible links to changes in the
microenvironment. Near-ambient UV-B and reduced UV-B treatments were realised by stretching plastic film filters that differentially
attenuate UV-B over peatland sample plots. We extracted the microfauna and analysed the dissolved nutrients held within Sphagnum capitula
removed from the top 1-cm of the peatland. In line with previous findings in this system, testate amoebae were more abundant under nearambient
UV-B than under reduced UV-B. Populations of the most common genus, Assulina, and other less prominent amoebae species of
Heleopera and Euglypha, were consistently increased under near-ambient UV-B. Overall diversity of testate amoebae was also higher under
near-ambient UV-B than under reduced UV-B, whereas rotifers, nematodes and mites were less abundant under near-ambient UV-B.
Concentrations of DOC and P were generally higher under near-ambient UV-B than under reduced UV-B. These changes, combined with the
changes previously reported in the plant and fungal communities, have the potential to influence peatland C storage, and surface nutrient
availability. The peatland microfaunal community under near-ambient solar UV-B may be regulated by the plant community through the
leaching of nutrients from leaf cells, and changes in Sphagnum morphology that affect the capitulum microenvironment.
Abstract: The influence of near-ambient and reduced
solar UV-B radiation on a peatland microfungal community
was assessed by exposing experimental plots to UVselective
filtration. Replicate plots were covered with
special plastic films to effect treatments of near-ambient
and attenuated solar UV-B. The microfungal community
from the top 1 cm of Sphagnum capitulum in a Tierra del
Fuego peatland was censused throughout three growing
seasons, between 1999 and 2002. Sphagnum capitula
under near-ambient UV-B were more compressed and held
more water than capitula under reduced UV-B. This water
had a greater conductivity and was more acidic under nearambient
UV-B, as would be expected with increased
leaching from the Sphagnum leaves. Nine regularly
occurring hyphal fungi from the peatland were identified,
at least to genus. Over three field seasons, no treatment
effect on total fungal colony abundance was recorded, but
individual species abundance was increased (Mortierella
alpina), decreased (Penicillium frequentans), or was
unaffected (P. thomii, Aureobasidium) by near-ambient
UV-B. Species richness was also slightly lower under
near-ambient UV-B. These treatment differences were
smaller than seasonal or inter-annual fluctuations in
abundance and species richness. In a growth chamber
experiment, lamp UV-B treatments indicated that realistic
fluxes of UV-B can inhibit fungal growth in some species.
In addition to this direct UV-B effect, we suggest that
changes in the peatland fungal community under nearambient
solar UV-B may also result from increased
nutrient and moisture availability in the Sphagnum
capitulum. The subtle nature of the responses of peatland
fungi to solar UV-B suggests that most fungal species we
encountered are well adapted to current solar UV-B fluxes
in Tierra del Fuego.
Abstract: • Tierra del Fuego is subject to increases in solar UV-B radiation in the austral spring and summer due to ozone depletion.
• Plastic films were used to filter solar UV-B radiation over peatland plots through six field seasons, resulting in near-ambient (c. 90%) and reduced (c. 17%) solar UV-B treatments.
• As in the first three field seasons of treatments, near-ambient UV-B caused reduced height growth but had no effect on biomass production of the moss Sphagnum magellanicum. It reduced leaf and rhizome growth of Tetroncium magellanicum. Height growth and morphology of Empetrum rubrum and Nothofagus antarctica were only affected by solar UV-B during the fourth to sixth field seasons. There was also a decrease in Tetroncium leaf nitrogen under near-ambient UV-B.
• Growth of Sphagnum was less affected than that of most emergent vascular plants. This enabled the Sphagnum mat to engulf more Nothofagus, and limit the escape of Empetrum under near-ambient UV-B. Yet, differences in the response of species to solar UV-B were not expressed as changes in plant community composition.
Notes: Associated Commentary Available: Pedro J Aphalo.
Do current levels of UV-B radiation affect vegetation? The importance of longterm experiments.New Phytologist (2003) 160: 273–280
Abstract: Tierra del Fuego, Argentina (551S), receives increased solar ultraviolet-B radiation (UV-B)
as a result of Antarctic stratospheric ozone depletion. We conducted a field study to
examine direct and indirect effects of solar UV-B radiation on decomposition of Gunnera
magellanica, a native perennial herb, and on the native community of decomposer
organisms. In general, indirect effects of UV-B mostly occur due to changes in the
chemical composition of litter, whereas direct effects during decomposition result from
changes in decomposer organisms and/or differences in the photochemical breakdown
of litter.We designed a full-factorial experiment using senescent leaves that had received
either near-ambient or attenuated UV-B during growth. The leaves were distributed in
litterbags and allowed to decompose under near-ambient or reduced solar UV-B during
the growing season. We evaluated initial litter quality, mass loss, and nutrient release of
decomposing litter, and microbial colonization of both initial litter and decomposed
litter. We found that litter that decomposed under near-ambient UV-B had significantly
less mass loss than litter that decomposed under reduced UV-B. The UV-B conditions
received by plants during growth, which did not affect mass loss and nutrient
composition of litter, affected fungal species composition but in different ways
throughout the decomposition period. Before the decomposition trial, Beauveria
bassiana and Penicillium frequentans were higher under reduced UV-B, whereas
Cladosporium herbarum and pigmented bacteria were more common under the nearambient
compared to the reduced UV-B treatment. After the decomposition period,
leaves that had grown under reduced UV-B showed higher frequency of Penicillium
thomii and lower frequency of Trichoderma polysporum than leaves that had grown
under near-ambient conditions. The UV-B condition received during decomposition also
affected fungal colonization, with Penicillium chrysogenum being more frequent in
leaves that had decomposed under reduced UV-B, while the other species were not
affected. Our results demonstrate that, in this ecosystem, the effects of UV-B radiation on
decomposition apparently occurred mostly through changes in the fungal community,
while changes in photochemical breakdown appeared to be less important.
Abstract: The southern part of Tierra del Fuego, in the southernmost tip of South America, is covered by dense Nothofagus spp. forests and
Sphagnum-dominated peat bogs, which are subjected to the influence of ozone depletion and to increased levels of solar ultraviolet-B
radiation (UV-B). Over the last 5 years we have studied some of the biological impacts of solar UV-B on natural ecosystems of this
region.We have addressed two general problems: (i) do the fluctuations in UV-B levels under the influence of the Antarctic ozone ‘hole’
have any measurable biological impact, and (ii) what are the long-term effects of solar (ambient) UV-B on the Tierra del Fuego
ecosystems? In this paper, we provide an overview of the progress made during the first 4 years of the project.We highlight and discuss
the following results: (1) ambient UV-B has subtle but significant inhibitory effects on the growth of herbaceous and graminoid species of
this region (growth reduction #12%), whereas no consistent inhibitory effects could be detected in woody perennials; (2) in the species
investigated in greatest detail, Gunnera magellanica, the inhibitory effect of solar UV-B is accompanied by increased levels of DNA
damage in leaf tissue, and the DNA damage density in the early spring is clearly correlated with the dose of weighted UV-B measured at
ground level; (3) the herbaceous species investigated thus far show little or no acclimation responses to ambient UV-B such as increased
sunscreen levels and DNA repair capacity; and (4) ambient UV-B has significant effects on heterotrophic organisms, included marked
inhibitory effects on insect herbivory. The results from the experiments summarized in this review clearly indicate that UV-B influences
several potentially important processes and ecological interactions in the terrestrial ecosystems of Tierra del Fuego.
Abstract: Seasonal variation and the differential effect of drought on photosynthetic parameters involved in carbon
assimilation in forest species have been poorly studied under natural conditions. Limitations to diffusion
and biochemical factors affecting leaf carbon uptake were analyzed in young beech seedlings (Fagus
sylvtica L.) growing in natural gaps of a beech-wood at the southern limit of the species. Half of the seedling
received periodic watering in addition to natural rainfall to reduce the severity of the summer drought
which is typical in the area. Plant water status was evaluated by measuring predawn water potential. Basic
biochemical parameters were inferred from photosynthesis-CO2 curves (A-Cc) under saturating light and chlorophyll
fluorescence. The curves were established on three dates during the summer months Main variables
studied included: stomatal and mesophyll conductance to CO2 (gs and gm respectively), maximum velocity
of carboxylation (Vcmax) and maximum electron transport capacity (Jmax). The gm was estimated by two
methodologies: the curve-fitting and J constant methods.
Seedlings withstood a moderate water stress as the leaf predawn water potential (Ψpd) measured during
the study was within the range –0.2 to –0.5 MPa. A mild drought caused gs and gm to decrease only
slightly in response to Ψpd. However both diffusional parameters explained most of the limitations to CO2 uptake.
Furthermore, non-stomatal limitations were also important limiting net photosynthesis as water stress
increased. In addition, it should be highlighted that the biochemical limitations, prompted by Vcmax and Jmax,
were related mainly to ontogenic factors, without any clear relationship with drought under the moderate
water stress experienced by beech seedlings through the study.
The results may help to further understand of the functional mechanisms influencing carbon fixation capacity
of beech seedlings. This capacity may influence the total carbon balance of beech seedlings, and feed
forward to their growth and survival under drought-prone environments such as those in the south of Europe.
Abstract: Spring phenology is considered one of the most important determinants of growth and survival in young
stands. It is relatively easy to monitor and is expected to respond to climate changes that will affect the favourable
period for growth in temperate regions. The response of trees to the environmental cues that govern
spring phenology is largely under genetic control and inter-populational differences exist within species. This
suggests that the trait undergoes site-specific selection. Data obtained through monitoring of bud burst at
multiple beech provenance-trials were compared with specific site and weather data to reveal geographical
clines in beech phenology.We fitted the Weibull function to harmonise phenology data collected using various
flushing scales and at different intensities of monitoring. By comparing data from 20 annual census of phenology
performed across 13 sites throughout Europe, we showed that accumulated temperature sum > 5°C
modelled the timing and duration of flushing more consistently than other temperature sum models > 0°C or
> 8°C, or simply Julian Day. Inconsistency in the number of degree hours required for flushing among sites,
reinforced the need for testing of more complex mechanistic models that include photoperiod, chilling period,
and summer drought in addition to temperature sum. South-North, East-West, and low-high elevational clines
were confirmed from the analysis. These findings; reinforce the need for caution in planting provenances
from the south-east of Europe, suited to warmer-drier summers, in more north-westerly sites; and highlight
the location of some potentially valuable late-flushing populations that also tolerate warm dry temperatures.
Notes: Beech is a dominant forest tree species of high economic as well as ecological importance with a
wide distribution range linking Scandinavia and the Mediterranean. Due to its functional flexibility and
large genetic plasticity, beech can be utilized to study wide reaching influences affecting ecosystems,
e.g. climate factors in different parts of Europe. The COST Action E52 «Evaluation of Beech Genetic Resources
for Sustainable Forestry» commenced March 2006. During the final meeting of this COST action
(Burgos, Spain, 4th to 6th of May, 2010) results of numerous research areas were presented, of
which a special selection is published here. Among them, the evaluation of data from provenance trials
located in most of the regions of beech occurrence show how well populations have adapted to certain
site-inherent environmental features, e.g. limited water availability, late frost occurrence, acidic
or calcareous soil, as well as how non-adapted populations react to such situations, and how successfully
they might cope with them. This is of great significance for assessing the value of both, a given
beech population and its ecosystem with respect to the conservation of beech ecosystems in a
broad sense and particularly the genetic resources of beech.