Planetary stations and Abyssal Benthic Laboratories: An overview of parallel approaches for long-term investigation in extreme environments

In spite of the apparent great differences between deep ocean and space environment, significant similarities can be recognized when considering the possible solutions and technologies enabling the development of remote automatic stations supporting the execution of scientific activities. In this sense it is believed that mutual benefits shall be derived from the exchange of experiences and results between people and organizations involved in research and engineering activities for hostile environments, such as space, deep sea, and polar areas. A significant example of possible technology transfer and common systematic approach is given, which describes in some detail how the solutions and the enabling technologies identified for an Abyssal Benthic Laboratory can be applied for the case of a lunar or planetary station

Retrospective Analysis of Wood Anatomical Traits Reveals a Recent Extension in Tree Cambial Activity in Two High-Elevation Conifers

The study of xylogenesis or wood formation is a powerful, yet labor intensive monitoring approach to investigate intra-annual tree growth responses to environmental factors. However, it seldom covers more than a few growing seasons, so is in contrast to the much longer lifespan of woody plants and the time scale of many environmental processes. Here we applied a novel retrospective approach to test the long-term (1926–2012) consistency in the timing of onset and ending of cambial activity, and in the maximum cambial cell division rate in two conifer species, European larch and Norway spruce at high-elevation in the Alps. We correlated daily temperature with time series of cell number and lumen area partitioned into intra-annual sectors. For both species, we found a good correspondence (1–10 days offset) between the periods when anatomical traits had significant correlations with temperature in recent decades (1969–2012) and available xylogenesis data (1996–2005), previously collected at the same site. Yet, results for the 1926–1968 period indicate a later onset and earlier ending of the cambial activity by 6–30 days. Conversely, the peak in the correlation between annual cell number and temperature, which should correspond to the peak in secondary growth rate, was quite stable over time, with just a minor advance of 4–5 days in the recent decades. Our analyses on time series of wood anatomical traits proved useful to infer on past long-term changes in xylogenetic phases. Combined with intensive continuous monitoring, our approach will improve the understanding of tree responses to climate variability in both the short- and long-term context

Environmental effects and biophysical constraints on xylem physiology and tree growth in conifers in the Alps

Trees are impressive long-living organisms that continuously increase in size by many orders of magnitude during ontogeny by accumulating xylem biomass in stem, branches and roots. While growing taller, trees continuously adjust the xylem structure to achieve an optimal balance of carbon costs for the competing biomechanical and hydraulic requirements. One of the main function of the xylem structure is the delivery of the water from the roots up to the leaves. This must be maintained during the ontogeny, when the hydrodynamic resistance increase due to the increase in the xylem path length. However, by widening the diameter of xylem conduit (from the stem apex downwards), trees are able to minimize the negative effect of height growth. Additionally, this widening is stable during ontogeny, thus determining the radial change in conduit dimension with cambial age (from the pith outwards), implying a dependency between the variation of conduit-lumen diameter with cambial age and the rates of stem elongation. These adjustments in the xylem structure remain permanently fixed and chronologically archived in the secondary xylem, and, given the tight link between structures and functions, these provide a ‘time component’ to functional responses induced by xylem plasticity, thus allowing to reconstruct growth dynamics under different environmental conditions. However, there is a lack of detailed information and standardized procedures to explore, at the intra-specific level, the long-term modifications of xylem traits over the full life-span of trees, together with their variability along axial and radial profiles. Additionally, little is known about the relationships between the structures and functions in a view of exploring the future challenges in how a plant’s hydraulic architecture may respond to the ongoing climate change. This thesis, represent a set of studies based on dendro-anatomical and physiological approaches aimed to: - identify priorities and trade-offs among xylem functions; - determine the anatomical traits responsible for them; - retrospectively analyze how these relationships vary during ontogeny under different environmental condition; - analyze the functional response to xylem modifications occurring during ontogeny; - investigate the possibility of retrospectively analyzed height growth based on hydraulic radial profiles. Furthermore, a guidance from sample collection to xylem anatomical data and a new approach to customize cell wall thickness measurements according to the specific aims of the study, were developed. This thesis has highlighted that the xylem anatomical structure of conifer trees (Larix decidua, Picea abies, Pinus cembra) showed a high priority and biophysical determination of traits linked to hydraulic efficiency, such as conduit size, to efficiently support assimilation necessary for tree growth. Besides, other functional traits linked to mechanical support and metabolic xylem functions showed more plastic responses to intrinsic and extrinsic factors. Due to the ontogenetic stability of axial patterns of conduit size, it was possible, based on radial profiles of xylem conduit diameter of tree rings, to estimate tree growth rate, even if species-site specific, and make comparison between trees living in different epochs. In addition, despite the risk of becoming more vulnerable to air seeding cavitation, trees showed to prioritize of hydraulic efficiency vs. safety during the ontogenetic development, as the increase in xylem conductance with tree height determined a contextual decrease in the hydraulic safety margin. This study showed the importance of taking into account the three dimensional anatomical trends to better understand of the trade-offs of hydraulic safety vs. efficiency shape up the tree architecture and affect its adjustments occurring during ontogeny to cope with the arising intrinsic (i.e., size-related) and extrinsic (i.e., environmental) constraints to growth

Quantitative wood anatomy

Quantitative wood anatomy analyzes the variability of xylem anatomical features in trees, shrubs, and herbaceous species to address research questions related to plant functioning, growth, and environment. Among the more frequently considered anatomical features are lumen dimensions and wall thickness of conducting cells, fibers, and several ray properties. The structural properties of each xylem anatomical feature are mostly fixed once they are formed, and define to a large extent its functionality, including transport and storage of water, nutrients, sugars, and hormones, and providing mechanical support. The anatomical features can often be localized within an annual growth ring, which allows to establish intra-annual past and present structure-function relationships and its sensitivity to environmental variability. However, there are many methodological challenges to handle when aiming at producing (large) data sets of xylem anatomical data. Here we describe the different steps from wood sample collection to xylem anatomical data, provide guidance and identify pitfalls, and present different image-analysis tools for the quantification of anatomical features, in particular conducting cells. We show that each data production step from sample collection in the field, microslide preparation in the lab, image capturing through an optical microscope and image analysis with specific tools can readily introduce measurement errors between 5 and 30% and more, whereby the magnitude usually increases the smaller the anatomical features. Such measurement errors—if not avoided or corrected—may make it impossible to extract meaningful xylem anatomical data in light of the rather small range of variability in many anatomical features as observed, for example, within time series of individual plants. Following a rigid protocol and quality control as proposed in this paper is thus mandatory to use quantitative data of xylem anatomical features as a powerful source for many research topics

Overall energy performance of polyvalent heat pump systems

Buildings account for almost 40% of energy consumption in Italy, being one of the most energy-consuming and polluting sectors. The increasing electrification of HVAC systems requires an effort on the adoption of more efficient and sustainable technologies. The article aims to quantify the potential of polyvalent heat pumps, also in comparison to traditional heat pumps

Growth form and leaf habit drive contrasting effects of Arctic amplification in long-lived woody species

Current global change is inducing heterogeneous warming trends worldwide, with faster rates at higher latitudes in the Northern Hemisphere. Consequently, tundra vegetation is experiencing an increase in growth rate and uneven but expanding distribution. Yet, the drivers of this heterogeneity in woody species responses are still unclear. Here, applying a retrospective approach and focusing on long-term responses, we aim to get insight into growth trends and climate sensitivity of long-lived woody species belonging to different functional types with contrasting growth forms and leaf habits (shrub vs. tree and deciduous vs. evergreen). A total of 530 samples from 7 species (common juniper, dwarf birch, woolly willow, Norway spruce, lodgepole pine, rowan, and downy birch) were collected in 10 sites across Iceland. We modelled growth trends and contrasted yearly ring-width measurements, filtering in high- and low-frequency components, with precipitation, land- and sea-surface temperature records (1967-2018). Shrubs and trees showed divergent growth trends, with shrubs closely tracking the recent warming, whereas trees, especially broadleaved, showed strong fluctuations but no long-term growth trends. Secondary growth, particularly the high-frequency component, was positively correlated with summer temperatures for most of the species. On the contrary, growth responses to sea surface temperature, especially in the low frequency, were highly diverging between growth forms, with a strong positive association for shrubs and a negative for trees. Within comparable vegetation assemblage, long-lived woody species could show contrasting responses to similar climatic conditions. Given the predominant role of oceanic masses in shaping climate patterns in the Arctic and Low Arctic, further investigations are needed to deepen the knowledge on the complex interplay between coastal tundra ecosystems and land-sea surface temperature dynamics

HVAC solutions for energy retrofitted hotel in Mediterranean area

To meet the European targets for achieving high-performing buildings, the refurbishment of the existing building stock and, in particular, of historical buildings represents a great challenge. The research aims at identifying the most energy-effective HVAC configuration for retrofitting historical hotels in Mediterranean area, where the objective is to minimize the consumptions for both space heating and cooling. A Reference Building for an historical hotel was simulated in five Mediterranean cities and different HVAC solutions were assessed, using EnergyPlus software coupled with tools specifically set to emulate the energy behaviour of certain HVAC technologies, aiming to highlight the most efficient alternative

Toward NZEB by optimizing HVAC system configuration in different climates

Finding the most appropriate matching between envelope features and HVAC system configurations in function of different climates results fundamental for minimizing buildings’ energy consumptions. The research aims at presenting the most energy-performing HVAC system configurations for high-performing buildings. Different configurations were modeled for new non-residential Reference Buildings in seven European cities, using dynamic simulation software EnergyPlus and some evaluation tools specifically set to emulate the energy performance of some specific HVAC technologies. Finally, the results obtained were compared in order to outline some conclusions, useful as guidelines for optimizing the choice of HVAC systems in function of climate conditions

Hydraulic traits of Juniperus communis L. along elevations and European populations

Plant hydraulics play an important role in determining plant distribution and performance, by influencing their growth and productivity. Knowledge of the hydraulic amplitude and plasticity of species is thus a prerequisite for estimating future performance under climate change. We investigated hydraulic safety and efficiency in Juniperus communis L. to estimate its intra-specific hydraulic variability. We analysed plants growing along an elevational transect (700-2000 m a.s.l., Tyrol, Austria) and plants grown in a common garden experiment from seeds collected in various European regions (France, Austria, Ireland, Germany and Sweden). Vulnerability to drought-induced embolism (i.e. hydraulic safety) was assessed via Cavitron and ultrasonic acoustic emission techniques while specific hydraulic conductivity (i.e. hydraulic efficiency) was measured with a flow meter. Hydraulic safety (water potentials inducing 12, 50 and 88% loss of conductivity) and efficiency did not differ significantly neither across elevations nor between European provenancies. Common juniper proved to a be a species with high resistance to drouht stress and showed surprisingly homogenous hydraulic traits, despite sub-species are formed at higher elevation and plant morphology differed widely across provenancies. Due to its overall high hydraulic safety, this species can be considered as less susceptible to the effects of a warmer climate

Transient Effects of Snow Cover Duration on Primary Growth and Leaf Traits in a Tundra Shrub

With the recent climate warming, tundra ecotones are facing a progressive acceleration of spring snowpack melting and extension of the growing season, with evident consequences to vegetation. Along with summer temperature, winter precipitation has been recently recognised as a crucial factor for tundra shrub growth and physiology. However, gaps of knowledge still exist on long-living plant responses to different snowpack duration, especially on how intra-specific and year-to-year variability together with multiple functional trait adjustments could influence the long-term responses. To fill this gap, we conducted a 3 years snow manipulation experiment above the Alpine treeline on the typical tundra species Juniperus communis, the conifer with the widest distributional range in the north emisphere. We tested shoot elongation, leaf area, stomatal density, leaf dry weight and leaf non-structural carbohydrate content of plants subjected to anticipated, natural and postponed snowpack duration. Anticipated snowpack melting enhanced new shoot elongation and increased stomatal density. However, plants under prolonged snow cover seemed to compensate for the shorter growing period, likely increasing carbon allocation to growth. In fact, these latter showed larger needles and low starch content at the beginning of the growing season. Variability between treatments slightly decreased over time, suggesting a progressive acclimation of juniper to new conditions. In the context of future warming scenarios, our results support the hypothesis of shrub biomass increase within the tundra biome. Yet, the picture is still far from being complete and further research should focus on transient and fading effects of changing conditions in the long term