Liu D., Ogaya R., Barbeta A., Yang X., Peñuelas J. (2018) Long-term experimental drought combined with natural extremes accelerate vegetation shift in a Mediterranean holm oak forest. Environmental and Experimental Botany. 151: 1-11.EnllaçDoi: 10.1016/j.envexpbot.2018.02.008
Increasing drought combined with natural extremes are expected to accelerate forest die-off and shifts in vegetation in the Mediterranean Basin. However, fewer studies have explored these climate-driven changes in forest ecosystems. A long-term (17-year) experimental drought (−30% precipitation) was established in a Mediterranean holm oak forest with high (H) and low (L) canopies to determine the changes in stem mortality, recruitment and composition shifts. Experimental drought increased annual stem mortality rate at the community level for both H- and L-canopies. Natural drought amplified the effects of experimental drought on stem mortality at the community level and of Q. ilex for H- and L-canopies. The timescales of natural drought, however, varied substantially with canopy types and species, with shorter timescales in L- than H-canopy and for Q. ilex than P. latifolia. Furthermore, experimental drought combined with natural extremes amplified the increases in stem mortality and decreases in growth for L-canopy. Contrasting responses between Q. ilex and P. latifolia for the relative in abundance and growth were observed in L-canopy and drought treatment reinforced the vegetation shift favoring P. latifolia. These findings suggest continuous drought regimes accelerated a vegetation shift, implying potential consequences for the functions and services for water-limited forest ecosystems. © 2018 Elsevier B.V.
Mu Z., Llusià J., Liu D., Ogaya R., Asensio D., Zhang C., Peñuelas J. (2018) Seasonal and diurnal variations of plant isoprenoid emissions from two dominant species in Mediterranean shrubland and forest submitted to experimental drought. Atmospheric Environment. 191: 105-115.EnllaçDoi: 10.1016/j.atmosenv.2018.08.010
We tested the effect of increasing drought conditions in the Mediterranean Basin on isoprenoid emissions for the coming decades by analyzing their effect experimentally on the dominant Mediterranean species Erica multiflora in a Garraf shrubland and Quercus ilex in a Prades forest in Catalonia (Spain). Drought was simulated in Garraf using automatically sliding curtains to decrease the amount of soil moisture by 5% and in Prades by partial rainfall exclusion and runoff exclusion for a 25% decrease. We measured photosynthetic rates (A), stomatal conductance (gs) and rates of isoprenoid emission in the morning and at midday for four seasons and determined the relationship of emission rates with environmental conditions. Terpenes were emitted by both species, but only E. multiflora emitted isoprene. α-Pinene and limonene were the most abundant terpenes. Isoprenoid emissions increased with air temperature and generally decreased as the amount of soil moisture increased. The results of this study suggest that higher isoprenoid emissions can be expected in the warmer and drier conditions predicted for the coming decades in the Mediterranean region. © 2018
Liu, D., Estiarte, M., Ogaya, R., Yang, X., Peñuelas, J. (2017) Shift in community structure in an early-successional Mediterranean shrubland driven by long-term experimental warming and drought and natural extreme droughts. Global Change Biology. : 0-0.EnllaçDoi: 10.1111/gcb.13763
Liu, D., Peñuelas, J., Ogaya, R., Estiarte, M., Tielbörger, K., Slowik, F., Yang, X., Bilton, M.C. (2017) Species selection under long-term experimental warming and drought explained by climatic distributions. New Phytologist. : 0-0.EnllaçDoi: 10.1111/nph.14925
Peñuelas, J., Sardans, J., Filella, I., Estiarte, M., Llusià, J., Ogaya, R., Carnicer, J., Bartrons, M., Rivas-Ubach, A., Grau, O., Peguero, G., Margalef, O., Pla-Rabés, S., Stefanescu, C., Asensio, D., Preece, C., Liu, L., Verger, A., Barbeta, A., Achotegui-Castells, A., Gargallo-Garriga, A., Sperlich, D., Farré-Armengol, G., Fernández-Martínez, M., Liu, D., Zhang, C., Urbina, I., Camino-Serrano, M., Vives-Ingla, M., Stocker, B.D., Balzarolo, M., Guerrieri, R., Peaucelle, M., Marañón-Jiménez, S., Bórnez-Mejías, K., Mu, Z., Descals, A., Castellanos, A., Terradas, J. (2017) Impacts of global change on Mediterranean forests and their services. Forests. 8: 0-0.EnllaçDoi: 10.3390/f8120463
Turnbull, M.H., Ogaya, R., Barbeta, A., Peñuelas, J., Zaragoza-Castells, J., Atkin, O.K., Valladares, F., Gimeno, T.E., Pías, B., Griffin, K.L. (2017) Light inhibition of foliar respiration in response to soil water availability and seasonal changes in temperature in Mediterranean holm oak (Quercus ilex) forest. Functional Plant Biology. 44: 1178-1193.EnllaçDoi: 10.1071/FP17032
Zhang, C., Filella, I., Liu, D., Ogaya, R., Llusià, J., Asensio, D., Peñuelas, J. (2017) Photochemical Reflectance Index (PRI) for detecting responses of diurnal and seasonal photosynthetic activity to experimental drought and warming in a Mediterranean shrubland. Remote Sensing. 9: 0-0.EnllaçDoi: 10.3390/rs9111189
Andresen, L.C., Müller, C., de Dato, G., Dukes, J.S., Emmett, B.A., Estiarte, M., Jentsch, A., Kröel-Dulay, G., Lüscher, A., Niu, S., Peñuelas, J., Reich, P.B., Reinsch, S., Ogaya, R., Schmidt, I.K., Schneider, M.K., Sternberg, M., Tietema, A., Zhu, K., Bilton, M.C. (2016) Shifting Impacts of Climate Change: Long-Term Patterns of Plant Response to Elevated CO2, Drought, and Warming Across Ecosystems. Advances in Ecological Research. : 0-0.EnllaçDoi: 10.1016/bs.aecr.2016.07.001
Benavides R., Escudero A., Coll L., Ferrandis P., Ogaya R., Gouriveau F., Peñuelas J., Valladares F. (2016) Recruitment patterns of four tree species along elevation gradients in Mediterranean mountains: Not only climate matters. Forest Ecology and Management. 360: 287-296.EnllaçDoi: 10.1016/j.foreco.2015.10.043
Evidence of tree regeneration failure of some species in the Iberian Peninsula forests warns us about the impact that the global change may exert on the preservation of Mediterranean forests, such as we know them. Predictions agree about an exacerbation of the summer drought there, acknowledged as the main limiting factor for the recruits' survival. On the other hand, many studies have also proved the relevant role that local heterogeneity has over the spatial distribution of forest species recruitment by providing safe sites. Therefore, to unravel how climate interacts with local factors over juveniles' performance seems crucial for the design of successful management strategies that allow facing the global warming. Here, we surveyed the natural recruitment of four dominant tree species in seven mountainous regions in the Iberian Peninsula, along entire elevational ranges as surrogates of their climatic ranges. Two of them have alpine and temperate distributions with populations at their rear edge in the Spanish mountains: Fagus sylvatica and Pinus uncinata; and the other two have a genuine Mediterranean distribution: Quercus ilex and Pinus nigra. Our main goal was to analyze for each species the effect of climate, local factors (i.e. light availability, stand structure and ground cover) and the interactions among them to identify the main drivers leading the regeneration process, assessed in terms of presence, abundance and mean annual growth of juveniles. The results showed different environmental factors determining the recruitment patterns of each species. Nevertheless, they highlighted the pervasive role exerted by both climate and fine scale factors, particularly the co-occurring vegetation on recruits' abundance, and the light availability on their growth. Moreover, we found some interactions among annual mean temperature and local factors, suggesting that climate and local heterogeneity act hierarchically, i.e. the local conditions may mitigate or exacerbate the impact of climate on juveniles. These results advocate for further research to increase our knowledge on the complex net of interactions among factors involved in recruitment at different scales, which in turn should be taken into account and incorporated in forthcoming management strategies. © 2015 Elsevier B.V.
Diaz-de-Quijano M., Kefauver S., Ogaya R., Vollenweider P., Ribas À., Peñuelas J. (2016) Visible ozone-like injury, defoliation, and mortality in two Pinus uncinata stands in the Catalan Pyrenees (NE Spain). European Journal of Forest Research. 135: 687-696.EnllaçDoi: 10.1007/s10342-016-0964-9
Ozone concentrations in the Pyrenees have exceeded the thresholds for forest protection since 1994. We surveyed the severity of visible O3 injuries, crown defoliation, and tree mortality of Pinus uncinata, the dominant species in subalpine forests in this mountain range, along two altitudinal and O3 gradients in the central Catalan Pyrenees and analysed their relationships with the local environmental conditions. The severity of visible O3 injuries increased with increasing mean annual [O3] when summer water availability was high (summer precipitation/potential evapotranspiration above 0.96), whereas higher [O3] did not produce more visible injuries during drier conditions. Mean crown defoliation and tree mortality ranged between 20.4–66.4 and 0.6–29.6 %, respectively, depending on the site. Both were positively correlated with the accumulated O3 exposure during the last 5 years and with variables associated with soil–water availability, which favours greater O3 uptake by increasing stomatal conductance. The results indicate that O3 contributed to the crown defoliation and tree mortality, although further research is clearly warranted to determine the contributions of the multiple stress factors to crown defoliation and mortality in P. uncinata stands in the Catalan Pyrenees. © 2016, Springer-Verlag Berlin Heidelberg.
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