Hydrothermal treatment as a complementary tool to control the invasive Pampas grass (Cortaderia selloana).

The rapid spread of invasive Pampas grass (PG) is having not only ecosystems impact, but also significant economic and social effects. The tonnes of bulky waste from the plant disposal require proper treatment to avoid seed dispersal, greenhouse gas emissions and landscape damage. In the pursuit of zero-waste management, hydrothermal treatment (HT) appears as a challenging alternative. The possibility of mobile HT systems offers an alternative to accomplish on-site both the PG waste management and the application of the resulting by-products within a circular framework. As a first step, this research shows that, without a prior drying step, the hydrothermal treatment at 100-230 °C under autogenous water vapor pressure for only 30 min allows safe seeds inertization, while a stable carbon-enriched solid and an aqueous stream are generated. Prolonging the process for 2 h has no profitable effects. As the reaction temperature increases, the PG residue is converted into a material with 49-58 wt% of carbon, 41-32 wt% of oxygen and 3-4 wt% of ash. The pH (~6.3), low electrical conductivity (1.21-0.86 dS/m), high carbon content, open porosity (5-8 m2/g) and improved performance in seed germination and in the early growth test suggest the potential of HT-solids derived at 100-120 °C as amendment to sequester carbon in the soil and improve its physico-biological properties. The phytotoxicity detected in the peat/lignite-like solids obtained at 200-230 °C limits its application in soil, but calorific values of 22-24 MJ/kg indicate their suitability as CO2-neutral fuel. The agrochemical analysis of the liquid by-products indicates poor value on their own, but their use supplemented with compost may be an option.

A local dormancy cline is related to the seed maturation environment, population genetic composition and climate.

BACKGROUND AND AIMS: Seed dormancy varies within species in response to climate, both in the long term (through ecotypes or clines) and in the short term (through the influence of the seed maturation environment). Disentangling both processes is crucial to understand plant adaptation to environmental changes. In this study, the local patterns of seed dormancy were investigated in a narrow endemic species, Centaurium somedanum, in order to determine the influence of the seed maturation environment, population genetic composition and climate. METHODS: Laboratory germination experiments were performed to measure dormancy in (1) seeds collected from different wild populations along a local altitudinal gradient and (2) seeds of a subsequent generation produced in a common garden. The genetic composition of the original populations was characterized using intersimple sequence repeat (ISSR) PCR and principal co-ordinate analysis (PCoA), and its correlation with the dormancy patterns of both generations was analysed. The effect of the local climate on dormancy was also modelled. KEY RESULTS: An altitudinal dormancy cline was found in the wild populations, which was maintained by the plants grown in the common garden. However, seeds from the common garden responded better to stratification, and their release from dormancy was more intense. The patterns of dormancy variation were correlated with genetic composition, whereas lower temperature and summer precipitation at the population sites predicted higher dormancy in the seeds of both generations. CONCLUSIONS: The dormancy cline in C. somedanum is related to a local climatic gradient and also corresponds to genetic differentiation among populations. This cline is further affected by the weather conditions during seed maturation, which influence the receptiveness to dormancy-breaking factors. These results show that dormancy is influenced by both long-and short-term climatic variation. Such processes at such a reduced spatial scale highlight the potential of plants to adapt to fast environmental changes.