Durant l’estiu els boscos emeten més concentració de monoterpens, les fragàncies relacionades amb la salut de les persones

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)

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.

Més informació: Bach, A.; Yáñez-Serrano, A.M.; Llusià, J.; Filella, I.; Maneja, R.; Penuelas, J. (2020). Human Breathable Air in a Mediterranean Forest: Characterization of Monoterpene Concentrations under the Canopy. International Journal of Environmental Research and Public Health. https://doi.org/10.3390/ijerph17124391

Font: Blog CREAF

Variable reproduction goes beyond masting


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.

Trade-off between gymnosperm resistance and resilience increases forest sensitivity to drought

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.