Sclerophylly (hard leaves) has evolved independently in different woody plant genera and has been traditionally considered as a stress-tolerance trait. However, the underlying drivers for this functional trait are still a matter of debate; it has been proposed as an adaptive response to miscellaneous stress factors, such as nutrient scarcity, drought stress, herbivory, and cold tolerance, and due to the large investment costs of sclerophylly, it is generally associated with a longer leaf life span.

The genus Quercus constitutes a unique living laboratory to understand global adaptive patterns along the leaf economic spectrum in forest trees. With more than 400 species, oaks are distributed along six zonobiomes and its versatility has resulted in a wide range of variations in leaf functional traits and contrasting adaptive strategies. However, although this wide variability cannot be explained alone by any of the ecological factors considered, such as drought, nutrient scarcity, low temperatures during vegetative period, and physical damage, neither any of them could be fully discarded. Noteworthy, our study also suggests that these constraints may have a synergistic effect, and from a functional point of view, we can conclude that in oaks leaf habit largely modulates the physiological implications of sclerophylly.

Alonso-Forn, D., Sancho-Knapik, D., Ferrio, J.P. et al. Revisiting the Functional Basis of Sclerophylly Within the Leaf Economics Spectrum of Oaks: Different Roads to Rome. Curr Forestry Rep (2020). https://doi.org/10.1007/s40725-020-00122-7

Invitation to contribute to Special Issue "Stable Isotopes in Forest Ecosystem Research"
Deadline for submission: 31 May 2019

Dr. Juan Pedro Ferrio, ARAID-CITA, Spain
Prof. Dr. M. Larry Lopez C., Yamagata University, Japan
Guest Editors

Special issue information:

Globally, forests are able to fix about 30% of annual anthropogenic CO₂ emissions, and may be responsible for 70–90% of continental water losses. Therefore, understanding forest response to environmental drivers is crucial to anticipate and eventually mitigate the impacts of future global change. For this purpose, stable isotopes analysis has become a particularly suitable tool, offering time- and space-integrated information on the environmental effects on tree physiology and the implications for carbon, water and nutrient ecosystem balances. In this Special Issue, we invite studies developing applications of stable isotopes in forest ecology, tree physiology and ecohydrology, as well as modelling or empirical studies aimed at improving our mechanistic understanding of isotope fractionation in trees.

In particular, we encourage studies on the application of stables isotopes to the study of:

• ecological interactions in relation to the use of resources, e.g. nutrients, water, light;
• genetic variability in water uptake and water use efficiency in trees;
• nutrient balance of forests in response to environmental or anthropogenic changes;
• nitrogen dynamics: soil-mycorrhiza-plant interface;
• interaction between forests and the hydrological cycle;
• physiological response to different silvicultural treatments or disturbances;
• whole-tree and ecosystem carbon and water balances;
• validation and/or development of mechanistic models of isotope fractionation;

Submediterranean forests are considered an ecotone between Mediterranean and Eurosiberian ecosystems, and are very sensitive to global change. A decline of Scots pine (Pinus sylvestris L.) and a related expansion of oak species (Quercus spp.) have been reported in the Spanish Pre-Pyrenees. Although this has been associated with increasing drought stress, the underlying mechanisms are not fully understood, and suitable monitoring protocols are lacking. The aim of this study is to bring insight into the physiological mechanisms anticipating selective decline of the pines, with particular focus on carbon and water relations. For this purpose, we performed a sampling campaign covering two growing seasons in a mixed stand of P. sylvestris and Quercus subpyrenaica E.H del Villar. We sampled seasonally twig xylem and soil for water isotope composition (δ18O and δ2H), leaves for carbon isotope composition (δ13C) and stems to quantify non-structural carbohydrates (NSC) concentration, and measured water potential and leaf gas exchange. The first summer drought was severe for both species, reaching low predawn water potential (−2.2 MPa), very low stomatal conductance (12 ± 1.0 mmol m−2 s−1) and near-zero or even negative net photosynthesis, particularly in P. sylvestris (−0.6 ± 0.34 μmol m−2 s−1 in oaks, −1.3 ± 0.16 μmol m−2 s−1 in pines). Hence, the tighter stomatal control and more isohydric strategy of P. sylvestris resulted in larger limitations on carbon assimilation, and this was also reflected in carbon storage, showing twofold larger total NSC concentration in oaks than in pines (7.8 ± 2.4% and 4.0 ± 1.3%, respectively). We observed a faster recovery of predawn water potential after summer drought in Q. subpyrenaica than in P. sylvestris (−0.8 MPa and −1.1 MPa, respectively). As supported by the isotopic data, this was probably associated with a deeper and more reliable water supply in Q. subpyrenaica. In line with these short-term observations, we found a more pronounced negative effect of steadily increasing drought stress on long-term growth in pines compared with oaks. All these observations confer evidence of early warning of P. sylvestris decline and indicate the adaptive advantage of Q. subpyrenaica in the area.

Paula Martín-Gómez, Mònica Aguilera, Jesús Pemán, Eustaquio Gil-Pelegrín & Juan Pedro Ferrio (2017) Contrasting ecophysiological strategies related to drought: the case of a mixed stand of Scots pine (Pinus sylvestris) and a submediterranean oak (Quercus subpyrenaica). Tree Physiology, Volume 37, Issue 11, 1 November 2017, Pages 1478–1492

URL:  https://doi.org/10.1093/treephys/tpx101

Some minerals, like gypsum, hold water in their crystalline structure. The activation energy of the dehydration reaction of gypsum is relatively low and the conversion of gypsum to bassanite (CaSO4H2O) or anhydrite (CaSO4) may take place at ambient conditions. Although still unexplored, the use of such crystallization water by organisms would point to a completely new water source for life, critical under dry conditions.

In this study we analyzed the hydrogen (2H) and oxygen (18O) isotope composition of the xylem water of shallow-rooted plants growing on gypsum, and compared it to the isotopic composition of the free and crystallization water of the gypsum soils where they grow. According to our results, the isotopic composition of the xylem sap of plants was closer to gypsum crystallization water than to free soil water, particularly during the dry summer. Bayesian stable isotope mixing models indicated that gypsum crystallization water accounted for up to 90% of the water used bythese species during summer. Plants could also uptake gypsum crystallization water during spring, when itaccounted for up to 30% of the xylem sap of plants. Although the underlying mechanisms require further research, this is the first experimental evidence in support of the role of gypsum crystallization water as a water source for life. Our results change the current paradigm on water use by plants, where water held in the crystalline structure of mineral rocks is not regarded as a potential source. Given the existence of gypsum on the surface of Mars and its widespread occurrence on arid regions worldwide, these findings have important implications for exobiology, the study of life under extreme conditions and arid land reclamation.

http://blogs.egu.eu/geolog/2015/04/22/drinkable-rocks/

Palacio, S., Azorn, J., Montserrat-Mart, G. and Ferrio, J. P.: Drinkable rocks: plants can use crystallization water from gypsum. Geophysical Research Abstracts Vol. 17, EGU2015-9011-1, 2015

Palacio, S., Azorn, J., Montserrat-Mart, G. and Ferrio, J. P.: The crystallization water of gypsum rocks is a relevant water source for plants. Nature Communications,5, 2014

In this study we described the characteristics of agriculture at its beginnings by comparing kernel and wood samples from ancient Near East sites - the birthplace of Western agriculture -- with present day samples. It is the first time that direct evidences enable to know humidity and fertility conditions of crops, as well as the process of cereal domestication developed by humans from the Neolithic (12,000 years ago) to early Roman times (around 2,000 years ago).

Source:
Jos L. Araus, Juan P. Ferrio, Jordi Voltas, Mnica Aguilera, Ramn Bux. Agronomic conditions and crop evolution in ancient Near East agriculture. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4953

I would like to draw your attention to our recent publication:

del Castillo J, Aguilera M, Voltas J, Ferrio JP (2013) Isoscapes of tree-ring carbon-13 perform like meteorological networks in predicting regional precipitation patterns. Journal of Geophysical Research Biogeosciences 118, 352-360

In this work, we managed to model spatial variability in mean annual precipitation from isotope data in a network of tree-ring sampling sites. Interestingly, the predictive ability of the models was almost identical to that obtained using a network of meteorological data with similar spatial density. This opens the possibility to upscale tree-ring reconstructions from local to regional levels.

Looking forward to getting your comments and suggestions about this study.

Figure: Comparison between A) annual precipitation according to the Atlas Climtico Digital de la Peninsula Ibrica (source: http://opengis.uab.es/wms/iberia/) and B) relative errors in isoscapes-estimated precipitation, based on the D13C of wood from Pinus halepensis and Quercus ilex (source: del Castillo et al. 2013).