High-frequency seasonal variation of leaf fluorescence and reflectance in Mediterranean forest species under natural environmental conditions

The strategies of two evergreen Mediterranean tree species (Arbutus unedo L. and Quercus ilex L.) to face annual temperature variability and extreme event responses has been monitored in continuum by leaf fluorescence and reflectance. The effect of chilling spells and the accumulation of cold days with chilling and freezing temperatures on winter photo-inhibition was discussed in terms of modulation capacity for fluorescence parameters to daily temperature and irradiance conditions. Throughout the winter Q. ilex resulted less photoinhibited than A. unedo, showing a more dynamic response in all fluorescence parameters and a higher non-photochemical quenching capacity. These characteristics effectively act to maintain a higher electron transport capacity in Q. ilex than in A. unedo

Afforestazione e fissazione della CO2 atmosferica: qualche cifra indicativa dalla ricerca scientifica

Afforestation is often proposed as one of the most effective nature-based solutions to sequester carbon from the atmosphere, so mitigating the impending climate crisis. As a result, we have witnessed over the last few years a flourishing of projects aimed at planting new forests, particularly in periurban and agricultural settings, without a preliminary scientific discussion of their expected impact. In this contribution, we have therefore tried to summarize the evidence available for Italian settings, so as to define the range of sequestration rates that can be realistically expected. Moreover, we have tried to highlight some of the issues (age effects, single tree vs. stand perspective) that should be taken into account in the debate in order to harmonize results and approaches. Based on available evidence, under mesic conditions and with adequate cures at and after planting, we could realistically expect over the first decades a Net Ecosystem Production of about 3.5 t C ha-1 yr-1, in good agreement with results from other European deciduous tree plantations. Higher rates are definitely possible with fast-growing species (e.g., poplar, eucalypt) and intensive management, not always compatible with the environmental aims of such projects. In conclusion, afforestation can yield important results (also considering the other ecosystem services provided, particularly important in peri-urban and agricultural settings), although far from the C sequestration provided by the protection and sustainable management of existing forests

Let's Exploit Available Knowledge on Vegetation Fluorescence

The potential to measure vegetation fluorescence from space (1) and to derive from it direct information on the gross primary productivity (GPP) of terrestrial ecosystems is probably the most thrilling development in remote sensing and global ecology of recent years, as it moves Earth observation techniques from the detection of canopy biophysics (e.g., fraction of absorbed radiation) and biochemistry (chlorophyll and nitrogen content) to the realm of ecosystem function. The existence of a functional relationship between fluorescence and photosynthesis has been elucidated over the last decade by several laboratories, notably as part of the preliminary studies of the European Space Agency Fluorescence Explorer (FLEX) Earth Explorer Mission. The empirical observation presented by Guanter et al. (2) of a linear relationship between fluorescence radiance and GPP, however, provides the first experimental confirmation of the feasibility of the approach already thoroughly tested at leaf levelat the desired scale, despite the confounding effects associated with the satellite detection of such a faint signal. A word of clarification is needed here. The use of fluorescence as a probe of leaf photochemistry has been a staple of plant ecophysiology for decades, rooted in a sound understanding of photosynthetic energy dissipation. However, most past studies had to rely for the interpretation of results on active (pulse-saturated) techniques, making them unsuitable for remote-sensing applications. Over recent years, however, novel process based models have been developed for the interpretation of steady-state, solar-induced fluorescence at the leaf to canopy scale (3). We are therefore in a position to move beyond the mere empirical observation of an association between GPP and fluorescence radiance. In particular, Guanter et al. (2) base their analysis on the assumption of a constant ratio between photosynthetic and fluorescence light use efficiencies (equation 3 in ref. 2).We know, however, that the ratio is not constant, but changes widely in response to light, CO2, stomatal limitations, and extreme stress (4, 5). Whats more, we can make sense of such changes, thus extracting valuable information from the very scatter that is apparent in their data. However, this process will require the availability of more tailored instruments, such as the one planned for the FLEX mission. As already stressed by Guanter et al. (2), the spatial resolution of the Global Ozone Monitoring Experiment-2 sensor (40 80 km) makes it difficult to compare meaningfully the fluorescence signal with ground measurements, when only 6070% of the footprint consists of the desired land-cover type (table S1 in ref. 2), suggesting that this could be largely responsible for the low signals observed in European grasslands. Moreover, the overpass time of the MetOp-A satellite (9:30 AM) implies that fluorescence is generally measured under light-limiting conditions, when fluorescence is only marginally affected by stomatal closure even under stress conditions. This result could explain the seasonal mismatch with daily GPP observed in natural ecosystems in the absence of irrigation (figure 4 in ref. 2). We hope, therefore, that this welcome contribution to this fast-advancing field will help demonstrate the potential of the new technique, and pave the way for more refined studies under both a technological and scientific point of view

Coconut coir as a sustainable nursery growing media for seedling production of the ecologically diverse quercus species

Peat, a non-sustainable resource, is still predominately used in forest nurseries. Coconut coir might provide an alternative, renewable, and reliable growing media but few studies have evaluated this media type in forest nurseries. We assessed the influence of pure coir, in combination with various fertilization regimes, on the growth and physiology of three ecologically diverse Quercus species seedlings (Q. robur, Q. pubescens, and Q. ilex) during nursery cultivation. Seedlings were grown using peat and pure coir in combination with three fertilization treatments (standard, K-enriched, and P-enriched). Data were collected for: (1) growth and physiological traits; (2) detailed above- and below-ground morphological traits by destructive analysis; and (3) NPK content in leaves, shoot and roots, and in the growing media, following cultivation. Peat and coir in combination with the various fertilization treatments affected above- and below-ground morphology and, to a lesser extent, the physiological traits of Quercus seedlings. Large effects of the substrate occurred for most morphological variables, with peat being more effective than coir in all studied species. Fertilization also produced significant differences. The effect of K-enriched fertilization on plant growth was clear across the three species and the two growing media. P-enriched fertilization in peat was the only combination that promoted a higher amount of this element in the tissues at the end of cultivation. Despite their smaller size, seedlings produced in coir were compatible with standard Quercus forest stocktype size, and showed a proportionally higher root system development and fibrosity. Our results suggest that coir can be used as an alternative substrate to grow Quercus species seedlings, and that fertilization can offset coir deficiencies in chemical properties. As several functional traits drive planting performance under varying environmental conditions. according to the Target Plant Concept, coir might thus serve as an acceptable material for seedling cultivation in some cases