Un equip d’investigació internacional on ha participat en Josep Peñuelas explora els factors que més afecten el comportament de les plantes i com es poden incloure als models predictius per perfeccionar-los. L’estudi, publicat a Nature Plants, vol millorar la comprensió del cicle global del carboni i els serveis ecosistèmics i quin futur els espera si els boscos canvien davant el canvi climàtic.
Bosc de coníferes. Public Domain.
“Hem trobat que si representem els principis d’evolució, autoorganització i maximització d’entropies (l’organització aleatòria d’alguns processos naturals) en els models, podrien predir millor el comportament de les plantes complexes, i la vegetació en general, en relació amb els canvis ambientals”, explica en Josep Peñuelas, investigador del CSIC al CREAF.
Aquests factors que proposa l’estudi ja s’han utilitzat anteriorment per separat per entendre aspectes concrets del funcionament de les plantes, però les implicacions que tenen quan es combinen encara no s’havien entès del tot. Profunditzar-hi és important per conèixer millor com afectarà el canvi climàtic a aquestes dinàmiques.
Franklin O, Harrison S, Dewar R, Farrior C, Brännström A, Dieckmann U, Pietsch S, Falster D, Penuelas J, et al. (2020). Organizing principles for vegetation dynamics. Nature Plants DOI: 10.1038/s41477-020-0655-x
Afforestation is considered an effective strategy for increasing carbon sequestration and mitigating climate change and it has undoubtedly increased C stored in biomass. Afforestation has been widely implemented in many countries since the 1990s, increasing the area of planted forests globally by about 1.05 × 108 ha Picture by Pixabay
Afforestation is the term used to refer the establishment of forests where previously there have been none, or where forests have been missing for a long time and has been proposed as an efficient method for removing carbon dioxide and mitigating climate change. The success of the goals of mitigation, however, depends on both the area of trees planted and the potential for carbon (C) sequestration of each afforestation. However, afforestation-induced changes in soil organic C (SOC) are poorly quantified due to the paucity of large-scale sampling data.
In a new
study published in the journal Nature
plants authors provide the first comprehensive assessment of the
afforestation impact on SOC stocks with a pairwise comparative study of samples
from 619 control-and-afforested plot pairs in northern China.
Authors found
context-dependent effects of afforestation on SOC: afforestation increases SOC
density (SOCD) in C-poor soils but decreases SOCD in C-rich soils, especially
in deeper soil. Thus, the fixed biomass/SOC ratio assumed in previous studies
could overestimate the SOC enhancement by afforestation. “By extrapolating the
sampling data to the entire region, we estimate that afforestation increased
SOC stocks in northern China by only 234.9 ± 9.6 TgC over the last three
decades. The study highlights the importance of including pre-afforestation
soil properties in models of soil carbon dynamics and carbon sink projections”
explained Dr. Hong from the Sino-French Institute for Earth System Science,
College of Urban and Environmental Sciences, Peking University, China.
The results
of the study strongly suggest that estimated afforestation C sink potentials
that do not account for background soil C stocks or the potentially negative
effects of afforestation is overly optimistic. The authors claim that these
findings also indicate that the assumption of a fixed ratio between soil and
biomass C, which has been widely used in previous studies for estimating soil C
stocks is unreliable.
“According to this study pre-afforestation soil
properties and original vegetation type need to be included in models of soil
carbon dynamics; and extensive global-scale field investigations are required
to improve the estimation of soil carbon stocks. Furthermore, the dependence of
soil C changes on background soil C and tree species highlights the importance
of site and species choices for maximizing afforestation C sequestration” said
Prof. Josep Penuelas from CREAF-CSIC Barcelona.
Reference: Hong, S., Yin, G.,
Piao, S., Chen, A., Cong, N., Dybzinski, R., Peñuelas, J., Zeng, H. 2020.
Divergent responses of soil organic carbon to afforestation. Nature Sustainability, doi:
https://doi.org/10.1038/s41893-020-0557-y.
Un estudi de l’ICTA, el CREAF, el CTFC i la UAB caracteritza per primera vegada la química forestal de l’aire per sota la copa dels arbres en un alzinar mediterrani. Les concentracions màximes de monoterpens, els compostos orgànics volàtils relacionats amb la salut humana, es produeixen al juliol i agost, a primera hora del matí i de la tarda.
Montseny. Autor: Pixel (Wikimedia Commons)
La recerca Human Breathable Air in a Mediterranean Forest: Characterization of Monoterpene Concentrations under the Canopy realitzada per l’investigador Albert Bach, de l’Institut de Ciència i Tecnologia Ambientals de la Universitat Autònoma de Barcelona (ICTA-UAB), ha comprovat que els monoterpens que emeten les plantes dins d’un alzinar tenen nivells màxims durant el juliol i l’agost. Els monoterpens són les fragàncies que emeten les plantes per comunicar-se, fer fora depredadors o captar l’atenció dels pol·linitzadors, entre d’altres. Són compostos orgànics volàtils actualment en estudi per les seves propietats antiinflamatòries, neuroprotectores i antitumorogèniques. En la recerca hi han col·laborat els investigadors del CREAF Joan Llusià, Iolanda Filella i Josep Peñuelas, juntament amb altres del Centre de Ciència i Tecnologia Forestal de Catalunya (CTFC), del Consejo Superior de Investigaciones Científicas (CSIC) i del Departament de Geografia de la UAB.
L’estudi, impulsat per la Fundació Bancària La Caixa i publicat a l’ International Journal of Environmental Research and Public Health, demostra que al bosc podem trobar aquests compostos a l’aire d’una forma molt variable. N’hi haurà més o menys depenent de l’estació de l‘any i l’hora del dia, sobretot segons la temperatura que faci, la radiació solar i la humitat. De fet, l’estudi ha comprovat que les màximes concentracions es produeixen durant el juliol i l’agost a primera hora del matí (de 6 a 8h) i de la tarda (de 13 a 15h), quan fa més calor i sol.
Els resultats suggereixen que, durant l’estiu, les persones que caminen per aquest tipus de boscos estarien subjectes a una major absorció potencial de monoterpens en el seu torrent sanguini, especialment a primera hora del matí i a partir del migdia. Les concentracions obtingudes són similars o majors que en d’altres estudis que han demostrat la relació entre aquests compostos i la salut de les persones, no només al laboratori sinó també al bosc.
Bosc i salut
Quan estem en contacte amb el bosc experimentem una sèrie d’efectes en la nostra salut en general: als sistemes cardiovascular, immunitari, respiratori i nerviós, als que s’hi afegeixen canvis en el benestar fisiològic i psicològic.
Tot i el seu paper rellevant al binomi bosc-salut, aquests compostos han estat poc estudiats per sota de la copa dels arbres, que és on té lloc la interacció amb les persones. Per això, aquest estudi pioner obre un nou marc de recerca als boscos mediterranis i constitueix una aportació important per a la comunitat científica i de la sanitat pública.
According to a new study published in the journal Nature Plants authors suggest that the first of the potential factors triggering a highly variable seed production could have been, before wind pollination and predators evolved, nutrient scarcity. Picture by Pixabay
Nutrient scarcity, and climate, are long
existing evolutionary forces that have selected for multiple plant traits and
have constrained the physiology of plants since their early development.
In a new study published in the journal Nature plants authors propose a
mechanism by which nutrient scarcity may select for highly variable seed
production, with weather patterns inducing masting synchrony across
populations; they also discuss why wind-pollination and predator satiation
cannot be the only selective pressures that select for highly variable
reproduction.
Nutrient availability is a direct determinant
of the mean fruit production in agriculture and in the wild. In this study, authors
discuss why low nutrient availability may have been an important factor
selecting for highly variable and synchronized seed production, the latter in
combination with adaptation to variability in long-term climate patterns.
According to the authors, given the fact that
temporally variable sexual reproduction in nature seems to be common, they
conclude that factors others than wind pollination and predator satiation may
have played a role in shaping this reproductive trait. “We suggest that one of
these potential factors triggering a highly variable seed production, before
wind pollination and predators evolved, may have been nutrient scarcity because
of its role in determining the physiology of a broad range of organisms”, said
Dr. Fernández-Martínez from University of Antwerp and collaborator of the
Global Ecology Unit.
“This mechanism, which could have originated
during the early evolution of plants, may explain why, under low nutrient
availability, nutrient-conservative plants with highly variable reproduction
may have been preferentially selected in comparison to nutrient-spending plants
(with more constant reproduction).” said Prof. Josep Penuelas from CREAF-CSIC
Barcelona.
Reference: Fernández-Martínez,
M., Sardans, J., Sayol, F., LaMontagne, J.M., Bogdziewicz, M., Collalti, A.,
Hacket-Pain, A., Vacchiano, G., Espelta, J.M., Peñuelas, J., Janssens, I.A.
2020. Reply to: Nutrient scarcity cannot cause mast seeding. Nature Plants. DOI: 10.1038/s41477-020-0703-6.
According to a new study published in the journal Nature Ecology and Evolution the increase in gymnosperm sensitivity to drought suggests that their increasing intrinsic water use efficiency may not have alleviated the impacts of drought stress. Picture by Shutterstock
The frequency and intensity of droughts have
grown over the decades, leading to increased forest decline. The response of
forest to drought can be evaluated by its sensitivity to drought (resistance)
and the post-drought recovery rate (resilience). However, it remains uncertain
how drought resistance and resilience of forests have changed across the space
and over time under climate change.
In a new study published in the journal Nature Ecology and Evolution authors assessed
the spatio-temporal dynamics of forest resistance and resilience to drought
over the past century (1901-2015) with global tree ring data records from 2935
sites and associated plant trait data. Authors point out that this study based
on an analysis of long-term tree-ring data is the first one to report a
trade-off in their recent trends between gymnosperm resistance and resilience
to drought. According to the authors such decrease in drought resistance but
increase in their drought resilience may potentially indicate a recent
life-history strategy shift of gymnosperms in coping with changing climate and
drought stress regimes.
“Surprisingly, we found that the trade-off
between resistance and resilience for gymnosperms, previously reported only
spatially, also occurred at the temporal scale. In particular, drought
resilience significantly increased but resistance decreased for gymnosperms
between 1950-1969 and 1990-2009, indicating that previous models simulations
may have underestimated the impacts of drought on gymnosperm-dominated forests
under future climate change”, said the PhD student Xiangyi Li from the Sino-French Institute for
Earth System Science, College of Urban and Environmental Sciences, Peking
University, China.
“We suggest that the altered ecosystem carbon
cycle processes should be considered in the next generation of forest
simulators to improve their predictive capacity of future ecosystem functioning
and terrestrial carbon balance. The priority for further studies is to
establish a network for long-term and synchronized observations of plant growth
conditions and traits” said Prof. Josep Penuelas from CREAF-CSIC Barcelona.
Reference: Li, X., Piao, S.,
Wang, K., Wang, X., Wang, T., Ciais, P., Chen, A., Lian, X., Peng, S.,
Peñuelas, J. 2020. Temporal trade-off between gymnosperm resistance and
resilience increases forest sensitivity to extreme drought. Nature Ecology and Evolution.
Secondary compounds (PSCs ) in plants (formed
from primary metabolites in specific pathways) are major contributors to the
chemical diversity of nature.. The distribution of PSCs is heterogeneous across
the plant kingdom, and these compounds exhibit extensive variation both among and
within species. Knowledge of the effect of PSCs on belowground interactions in
the more diffuse community of species living outside the rhizosphere is sparse
compared with what we know about how PSCs affect aboveground interactions.
In a new study published in the journal Trends in Ecology and Evolution authors
illustrate that PSCs from foliar tissue, root exudates, and leaf litter
effectively influence such belowground plant–plant, plant–microorganism, and
plant–soil invertebrate interactions.
The study shows that soil is a theater of
facilitation, symbiosis, and warfare deployed by plants and the various organisms
living in it, and PSCs have a major role mediating many of these interactions.
Plants and soil organisms have adapted to withstand, detoxify, or use the
cocktail of PSCs originally meant to harm some of them. ”Therefore,
understanding PSC-mediated relationships at the community scale and identifying
the compounds involved in these interactions is important for better insight
into the functioning of these systems and their evolution, especially in
changing environments” said Dr. Bodil K. Ehlers from Aarhus University, Denmark
According to the study climatic factors can
induce PSC production and select for different plant chemical types. “Therefore,
climate change can alter both quantitative and qualitative PSC production, and
how these compounds move in the soil. This can change the soil chemical environment,
with cascading effects on both the ecology and evolution of belowground species
interactions and, ultimately, soil functioning” said Prof. Josep Penuelas from
CREAF-CSIC Barcelona.
“We encourage the creation of open,
community-wide, curated, labeled, broad-spectrum PSC data sets across plant
species and soils, because this would greatly increase the transfer of knowledge
between scientists studying plants, microbes, and invertebrates in this
biological belowground theatre” added Prof. Josep Penuelas from CREAF-CSIC
Barcelona.
.Reference: Ehlers, B.K., Berg, M.P., Staudt, M., Holmstrup, M., Glasius, M., Ellers, J., Tomiolo, S., Madsen, R.B., Slotsbo, S., Penuelas, J. 2020. Plant Secondary Compounds in Soil and Their Role in Belowground Species Interactions. Trends in Ecology & Evolution, doi: 10.1016/j.tree.2020.04.001.
Plants
and vegetation play a critical role in supporting life on Earth, but there is
still a lot of uncertainty in our understanding of how exactly they affect the
global carbon cycle and ecosystem services. A new IIASA-led study explored the
most important organizing principles that control vegetation behavior and how
they can be used to improve vegetation models.
We rely on the plants that make up our planet’s
ecosystems to release oxygen into the atmosphere, absorb carbon dioxide (CO2),
and provide habitat and food for wildlife and humans. These services are
critical in the future management of climate change, especially in terms of CO2
uptake and release, but due to the many complex, interacting processes that
affect the ability of vegetation to provide these services, they remain difficult
to predict.
In an IIASA-led perspective published in the journal Nature Plants, an international team of
researchers endeavored to address this problem by exploring approaches to
master this complexity and improve our ability to predict vegetation dynamics.
They explored key organizing principles that govern these processes – specifically,
natural selection; self-organization (controlling collective behavior among
individuals); and entropy maximization (controlling the outcome of a large
number of random processes). In general, an organizing principle determines or
constrains how components of a system, such as different plants in an ecosystem
or different organs of a plant, behave together. Mathematically, such a
principle can be seen as an additional equation added to a system of equations,
allowing one or more previously unknown variables in the system to be
determined and thereby reducing the uncertainty of the solution.
A lot of research has gone into understanding and
predicting how plant processes combine to determine the dynamics of vegetation
on larger scales. To integrate process understanding from different
disciplines, dynamic vegetation models (DVMs) have been developed that combine
elements from plant biogeography, biogeochemistry, plant physiology, and forest
ecology. DVMs have been widely used in many fields including the assessment of
impacts of environmental change on plants and ecosystems; land management; and
feedbacks from vegetation changes to regional and global climates. However,
previous attempts to improve vegetation models have mainly focused on improving
realism by including more processes and more data. This has not led to the
expected success because each additional process comes with uncertain
parameters, which has in turn caused an accumulation of uncertainty and
therefore unreliable model predictions.
“Despite the ever-increasing availability of data, and
the fact that vegetation science, like many other scientific fields, is
benefitting from increasing access to big data sets and new observation
technologies, we also need to understand governing principles like evolution to
make sense of the big data. Current models are not able to reliably predict
long-term vegetation responses,” explains lead author Oskar Franklin, a
researcher in the IIASA Ecosystems Services and Management Program.
The authors expect that apart from leading to better
tools for understanding and managing the biosphere, the proposed
“next-generation approach” may result in different trajectories of
projected climate change that both policy and the general public would have to
cope with.
Reference
Franklin O,
Harrison S, Dewar R, Farrior C, Brännström A, Dieckmann U, Pietsch S, Falster
D, ….Penuelas J,….et al. (2020). Organizing principles for vegetation dynamics.
Nature Plants DOI: 10.1038/s41477-020-0655-x
The
expansion of farmlands to meet the growing food demand of the world’s ever
expanding population places a heavy burden on natural ecosystems. A new IIASA
study however shows that about half the land currently needed to grow food
crops could be spared if attainable crop yields were achieved globally and
crops were grown where they are most productive.
The land sparing debate, which was
sparked around 2005 by conservation biologists, recognized that there is
usually a limit to the extent to which farmland can be made ‘wildlife friendly’
without compromising yields, while most threatened species only profit from the
sparing or restoration of their natural habitats. Interest in this topic
recently gained new momentum through the Half Earth project, which aims to
return half the area of land currently being used for other purposes to natural
land cover to restrict biodiversity loss and address other impacts of land use
such as greenhouse gas emissions.
According to the authors of the study published in Nature Sustainability, the need for this
type of strategy is urgent, given the increasing global demand for agricultural
products. The study is the first to provide insight into the amount of cropland
that would be required to fulfill present crop demands at high land use
efficiency without exacerbating major agricultural impacts globally.
“The main questions we wanted to address were
how much cropland could be spared if attainable crop yields were achieved
globally and crops were grown where they are most productive. In addition, we
wanted to determine what the implications would be for other factors related to
the agricultural sector, including fertilizer and irrigation water requirements,
greenhouse gas emissions, carbon sequestration potential, and wildlife habitat available
for threatened species,” explains study lead author Christian Folberth, a
researcher in the IIASA Ecosystems Services and Management Program.
The study results indicate that with high nutrient inputs
and reallocation of crops on present cropland, only about half the present
cropland would be required to produce the same amounts of major crops. The
other half could then in principle be used to restore natural habitats or other
landscape elements. The findings also show that land use is currently somewhat inefficient
and not primarily due to the upper limits to crop yields as determined by
climate in many parts of the world, rather, it is strongly subject to
management decisions.
It is difficult to say exactly how much biodiversity is
impacted as a direct result of agricultural activities, but it is estimated to
exceed safe boundaries, primarily due to habitat loss. In this regard, the researchers
evaluated two scenarios: the first proposes maximum land sparing without
constraints, except for the present cropland extent, while the second scenario
puts forward targeted land sparing that abandons cropland in biodiversity
hotspots and uniformly releases 20% of cropland globally. There were only
marginal differences between the two scenarios in most aspects, except for
wildlife habitat, which only increased significantly with targeted land sparing.
This however still enabled reducing the cropland requirement by almost 40%.
Furthermore, “we found that greenhouse gas emissions and
irrigation water requirements are likely to decrease with a reduced area of
cultivated land, while global fertilizer input requirements would remain
unchanged. Spared cropland could also provide space for substantial carbon
sequestration in restored natural vegetation. Yet, potentially adverse local
impacts of intensive farming and land sparing such as nutrient pollution or loss of income in rural areas
will need to be studied
further” says Prof. Josep Penuelas from CREAF-CSIC Barcelona, co-author of the
study and ERC-Synergy project co-lead.
“The results of our study can help policymakers and the
wider public to benchmark results of integrated land use scenarios. It also
shows that cropland expansion is not inevitable and that there is significant
potential for improving present land use efficiency. If the right policies are
implemented, measures such as improved production technologies can be just as
effective as demand-side measures like dietary changes,” says project co-lead and
former IIASA Ecosystems Services and Management Program Director Michael Obersteiner.
“However, in all cases such a process would need to be steered by policies to
avoid unwanted outcomes.”
Reference
Folberth C,
Khabarov N, Balkovič J, Skalský R, Visconti P, Ciais P, Janssens I, Peñuelas J,
Obersteiner M (2020). The global cropland sparing potential of high-yield
farming. Nature Sustainability DOI: 10.1038/s41893-020-0505-x
El CREAF participa en un estudi internacional a la tundra àrtica liderat per iDiV i descobreixen que les plantes de la tundra tenen una varietat de mecanismes molt més diversa del que es pensava anteriorment per fer front als climes freds. Igualment, comproven que en aquestes ambients extrems es mantenen les mateixes normes que en altres llocs del món: la mida de la planta i l’economia dels recursos expliquen la diversitat de la vida vegetal.
Les flors de campana blanca del bruc àrtic són adaptacions a la vida als extrems freds del bioma de la tundra. (Imatge: Elise Gallois)
Les plantes de la tundra àrtica usen una àmplia varietat d’estratègies per sobreviure a uns estius molt curts i a uns hiverns llargs i durs. Aquesta troballa, publicada a Nature Communication i liderat pel Centre Alemany per a la Investigació Integrativa de la Biodiversitat (iDiv), en col·laboració amb altres centres de recerca com el CREAF, indica que les plantes de la tundra tenen una varietat de mecanismes molt més diversa del que es pensava anteriorment per fer front a aquests climes freds. En un món que s’escalfa progressivament, aquestes plantes es beneficiaran el tenir una àmplia gamma de formes d’adaptar-se al clima canviant. A més l’estudi confirma que aquestes plantes que viuen en ambients extrems també es regeixen pels patrons generals que expliquen la biodiversitat de plantes sobre la terra: la mida i l’economia dels recursos .
A l’extrem nord-oest del Canadà, més enllà de les muntanyes cobertes de glaceres, al llarg del delta del Mackenzie i a l’altre costat de la Mar Àrtic, un científic està ajupit sobre una petita branqueta de bruc àrtic. S’ha passat tot el dia buscant les típiques taques de flors blanques característiques de la tundra que s’eleven en petits cúmuls. Amb el calibrador i el bloc de notes, les mans ara entumides, pren algunes mesures finals abans d’afanyar-se a tornar a la calor de la seva cabana. Les flors es gronxen alegrement a la brisa, el bruc àrtic roman molt còmode a l’extrem fred de la vida a la Terra.
La vida de les plantes àrtiques es troba als extrems del clima fred del planeta. (Imatge: Sandra Angers-Blondin)
Aquest científic, com era d’esperar, era jo. I les meves mans gairebé s’han recuperat. Per alguns pot ser sorprenent pensar que vaig passar la major part del meu temps en aquest entorn increïblement bell mirant el terra (escanejant periòdicament que no hi hagués ossos) i prenent mesures complexes de plantes àrtiques. No obstant això, les característiques de les plantes, poden dir-nos molt sobre les seves estratègies de vida i sobre com poden respondre a el canvi climàtic. A la tundra, que actualment s’està escalfant més del doble de ràpid que el planeta en el seu conjunt, poder vincular com l’augment de les temperatures modifica aquestes característiques (com ara l’alçada de les plantes) és extremadament valuós per comprendre com poden canviar els ecosistemes. Per descomptat, això només funciona si les plantes de tundra segueixen unes regles concretes.
Per a nosaltres, les persones que fem ciència, la idea que les plantes segueixen regles generals a l’hora de desenvolupar-se o de fer certes funcions és extremadament atractiva. Cercar patrons simples que expliquin la gran diversitat de vida vegetal a la Terra és una tasca que està en marxa des de fa més d’un segle, i potser des de les exploracions de Humboldt fa més de 200 anys. A més, sabem que si els patrons que observem es poguessin relacionar amb els canvis en el medi ambient o amb la coexistència d’espècies, podem revolucionar la nostra comprensió de l’ecologia de les plantes, segons alguns, el “Sant Grial” de l’ecologia.
Cottongrass es beneficia de l’escalfament del clima àrtic. (Imatge: Jeffrey Kerby / National Geographic Society)
Al 2016, un estudi dirigit per Sandra Díaz va donar un gran pas endavant. Els autors van descobrir que només dues dimensions: la mida de la planta (gran i llenyosa versus petita i no llenyosa) i l’economia dels recursos (adquisitiva versus conservadora) explicaven la majoria de les variacions de les plantes. En les seves paraules, “l’espectre global de la forma i funció de la planta és, en cert sentit, un pla galàctic dins el qual podem posar qualsevol planta, des del anís estrellat fins al gira-sol, en funció dels seus trets”.I què hi ha de les altres plantes de la tundra? Són una constel·lació molt unida, o una dispersió d’estrelles en tota la galàxia?
Ara tornem al nostre bruc àrtic. Amb fulles duradores i perennes, de la meitat de la mida d’un gra d’arròs, una estructura llenyosa que abraça el sòl i llavors gairebé massa petites per veure a simple vista, aquest arbust nan segurament ha d’ocupar els llocs més gelats i distants dins d’aquest pla galàctic de què parlava Díaz. I què hi ha de les altres plantes de la tundra? Són una constel·lació molt unida, o una dispersió d’estrelles en tota la galàxia? Dins d’una petita habitació que intentava captar els últims centelleigs d’una tardor escocès, els cervells brunzien.
La majoria de les dades de característiques de plantes del món s’obtenen de les regions temperades i dels tròpics. Hi ha molt poques dades disponibles de les plantes de la tundra. Això no seria un problema si volguéssim dibuixar patrons a tot el planeta en el seu conjunt, però volíem entendre les regles subjacents que s’amaguen en les condicions extremes en la tundra. Per això, la major barrera davant nostre radicava en les dades.
Les plantes àrtiques tenen una varietat i formes sorprenentment àmplies. (Imatge: Sandra Angers-Blondin)
Per solucionar-ho, vaig intensificar el poder de la col·laboració. Afortunadament, estava lluny de ser l’únic científic ajupit sobre una branqueta de bruc. Un equip de científics i científiques van ajudar-me a recopilar la informació que necessitàvem per comprendre la variació dels trets a la tundra. Amb l’ajuda de més de 100 contribuents, vam sumar més de 50,000 nous registres de característiques, i teníem les dades que necessitàvem per provar si les dues dimensions que afirmava Díaz en 2016 es mantenien igual a la tundra.Amb l’ajuda de més de 100 contribuents, vam sumar més de 50,000 nous registres de característiques de plantes.
En resum, la resposta és que les plantes de la tundra s’agrupen i ocupen un rang sorprenentment ampli de trets globals. Tot i que es troben en un extrem de la vida vegetal a la Terra, tenen estratègies notablement variades per capturar recursos i fer front a les condicions climàtiques extremes i a les estacions de creixement increïblement curtes de la tundra. Potser encara més sorprenent, les regles globals es mantenen extremadament bé en la tundra: les mateixes dues dimensions expliquen la majoria de la variació de característiques.
On ens deixa això? El nostre estudi suggereix que les relacions entre les característiques de les plantes i els canvis ambientals van més enllà de les dades globals i es compleixen també en cada bioma. Així, des de l’altíssim arbre de la sequoia fins al petit bruc àrtic, semblen sotmetre les mateixes relacions on la mida de la planta i l’economia dels recursos expliquen la majoria de les variacions de la vida vegetal a la Terra. El Sant Grial de l’ecologia vegetal pot estar a l’abast.El nostre estudi suggereix que les relacions entre les característiques de les plantes i els canvis ambientals van més enllà de les dades globals i es compleixen també en cada bioma.
RIn the far north-west of Canada, beyond the glacier-capped mountains, out along the Mackenzie delta and across the Arctic Sea, a scientist is crouched over a tiny sprig of Arctic heather. He has spent all day on the lookout for the patch of characteristic white flowers, rising just a few centimetres above the tundra. With caliper and notepad, hands now numb, he takes a few final measurements before hurrying back to the warmth of his cabin. The Arctic heather remains, flowers bobbing merrily in the breeze, quite at home at the cold edge of life on Earth.
The white bell flowers of the Arctic heather. Photo credit Elise Gallois
That scientist, unsurprisingly, was me. And my hands have almost recovered. It can come as a bit of a surprise to some that I spent the majority of my time in this breathtakingly beautiful environment staring at the ground (with periodic scans for bears) taking intricate measurements of Arctic plants. However, the characteristics of plants, known as plant traits, can tell us a huge amount about their life strategies and how they might respond to climate change. In the tundra, which is currently warming more than twice as fast as the planet as a whole, being able to link rising temperatures to traits such as plant height is extremely valuable in understanding how whole ecosystems might change. Of course, that only works if tundra plants follow the rules.
The idea that plants follow general rules relating to their form and function is extremely appealing. The search for simple patterns underpinning the vast diversity of plant life on Earth has been on the go for at least a century, and perhaps as far back as Humboldt’s explorations over 200 years ago . What is more, if patterns in plant traits could be linked to environment or to species co-existence, we could see a revolution in our understanding of plant ecology – the “holy grail” of ecology according to some.
Measuring the characteristics of plants, known as plant traits, can help us understand how they might respond to climate change. Photo credit Team Shrub
In 2016, a study led by Sandra Díaz provided a major step forward. The authors found that just two dimensions – plant size (large and woody vs small and non woody) and resource economics (acquisitive vs conservative) – explained the majority of variation in six fundamental plant traits across global plant species. In their words, “the global spectrum of plant form and function is thus, in a sense, a galactic plane within which we can position any plant—from star anise to sunflower—based on its traits.”
Now let’s return to our Arctic heather. With hardy evergreen leaves half the size of a grain of rice, a ground-hugging woody structure, and seeds almost too small to see, this dwarf shrub must surely occupy the most icy and distant of outposts within this galactic plane. And what about other tundra plants? Are they a close-knit constellation, or a scattering of stars throughout the galaxy? Inside a small room attempting to catch the last glimmers of a Scottish autumn, brains were whirring.
Arctic plant life on the edge. Photo credit Sandra Angers-Blondin
The greatest barrier before us lay in the data. The majority of the world’s plant trait data is collected from temperate regions and the tropics. Very little data was available for tundra plants. That might be appropriate to draw out patterns across the planet as a whole, but we wanted to understand if apparently underlying rules applied within the whole, in the extreme conditions in the tundra.
Step up the power of collaboration. Thankfully, I was far from the only scientist crouched over a sprig of heather. The “Tundra Trait Team”, led by Dr. Anne Bjorkman and Dr. Isla Myers-Smith and funded by the iDiv German Centre for Integrative Biodiversity Research and the Natural Environment Research Council of the UK, had been compiling just the information we needed to understand trait variation in the tundra. With help from well over 100 contributors, together adding over 50,000 new trait records, we now had the data we needed to test whether the two dimensions that framed the global spectrum of plant form and function held up in the tundra.
Cottongrass is benefiting from the warming Arctic climate. Photo credit Jeffrey Kerby, National Geographic Society
The answer in short, is that tundra plants occupy half of global trait space. The slightly longer answer is that although tundra plants do cluster together, they occupy a surprisingly wide range of global trait space. Although they are at the small end of plant life on Earth (as you might have expected), they still have remarkably varied strategies for capturing resources and coping with the extreme climatic conditions and incredibly short growing seasons of the tundra biome. Perhaps even more surprisingly, global rules hold up extremely well in the tundra: the same two dimensions explain the majority of trait variation.
Global plant trait relationships apply even at the cold extremes of life on Earth. Photo credit Sandra Angers-Blondin
Where does this leave us? Our study suggests that trait relationships are not simply emergent properties from global plant trait data, but say something fundamental about the rules that underpin evolution, community assembly, and ecosystem response to environmental change. So from the towering redwood tree to the tiny Arctic heather, global plant trait relationships really do seem to apply across the broad spectrum of plant life on Earth. The holy grail of plant ecology may indeed be within reach.
Author: Haydin Thomas. Researcher, University of Edinburgh
