Michele Carbognani

Warming effects and plant trait control on the early-decomposition in alpine snowbeds

Background and aimsIn cold biomes, litter decomposition, which controls the nutrient availability for plants and the ecosystem carbon budget, is strongly influenced by climatic conditions. In this study, focused on the early litter decay within snowbed habitats, the magnitude of the short- and long-term influences of climate warming, the direction of the effects of warmer temperature and advanced snowmelt, and the control of microclimatic features and plant traits were compared.MethodsCombining experimental warming and space-for-time substitution, mass loss and nutrient release of different plant functional types were estimated in different climatic treatments with the litter bag method.ResultsPlant functional types produced a larger variation in the early-decomposition compared to that produced by climatic treatments. Litter decay was not affected by warmer summer temperatures and reduced by advanced snowmelt. Structural-related plant traits exerted the major control over litter decomposition.ConclusionsLong-term effects of climate warming, resulting from shifts in litter quality due to changes in the abundance of plant functional types, will likely have a stronger impact on plant litter decomposition than short-term variations in microclimatic features. This weaker response of litter decay to short-term climate changes may be partially due to the opposite influences of higher summer temperatures and advanced snowmelt time.

Current vegetation changes in an alpine late snowbed community in the south-eastern Alps (N-Italy)

During the last decades, a significant warming was observed in the Alps, cascading into a decrease in snowfall and snow-cover duration. Within the alpine landscape, snowbed communities are regarded as especially vulnerable to the predicted warmer temperatures and earlier snowmelt time. Albeit snowbeds represent a prominent component of the tundra biome, the current vegetation dynamics of these habitats are not yet well understood. In this study, the changes of vascular species richness, co-occurrence, composition, and abundance were evaluated within a late snowbed in the south-eastern Alps. The study was based on a re-survey of 11 permanent plots after a 6-year period. Species richness and abundance significantly increased and species co-occurrence shifted toward higher species segregation. Moreover, the changes in species richness at different spatial scales were related to different environmental factors, and a change in the proportion between snowbed and non-snowbed plants was found. The results suggest an increasing importance of competitive interaction among species in determining the future structure and composition of this community. In conclusion, there is strong evidence that this snowbed community is not in equilibrium with the current climate, and that changes in floristic composition and functional processes of this habitat are underway.

Effects of nutrient amendments on modular growth, flowering effort and reproduction of snowbed plants

Background: There have been few studies on the effects on alpine flora and vegetation of an increase in nutrient availability. Two main potential sources of increased nutrient availability in alpine ecosystems are enhanced mineralisation caused by climate warming and atmospheric nitrogen deposition. Little is known on how life history traits of different species are related at individual and community levels to enhanced nutrient availability. Aims: We investigated the effects of nitrogen and phosphorus addition on the modular growth, flowering and germination of four species: two snowbed specialists and two alpine generalists. Methods: We established in a late snowbed at the Gavia Pass, Italian Alps, a factorial experiment with four fertiliser treatments (N, P, Low N+P, and High N+P) and an unfertilised control. Nutrients were applied in 2003–2006 and we recorded the number of modules per individuals, total number of flowers, number of flowers per flowering module, and calculated the percentage of flowering modules in 2005 and 2006, and counted the number of seedlings in 2006. Results: The modular growth and flowering effort of the species appeared to be co-limited by N and P. The alpine generalists showed greater responses to fertilization in vegetative growth and flowering compared with snowbed specialists. The number of seedlings recorded indicated species-specific responses to nutrient addition. Conclusions: Our results suggest that enhanced nutrient availability stimulates modular growth and flowering effort in responsive alpine generalist species. This, in turn, could lead to an increase in their abundance, leading to changes in community structure in snowbeds with enhanced nutrient availability.

Micro-climatic controls and warming effects on flowering time in alpine snowbeds

Alpine snowbed communities are among the habitats most threatened by climate change. The warmer temperature predicted, coupled with advanced snowmelt time, will influence flowering phenology, which is a key process in species adaptation to changing environmental conditions and plant population dynamics. However, we know little about the effects of changing micro-climate on flowering time in snowbeds and the mechanisms underlying such phenological responses. The flowering phenology of species inhabiting alpine snowbeds was assessed with weekly observations over five growing seasons. We analysed flowering time in relation to micro-climatic variation in snowmelt date, soil and air temperature, and experimental warming during the snow-free period. This approach allowed us to test hypotheses concerning the processes driving flowering phenology. The plants were finely tuned with inter-annual and intra-seasonal variations of their micro-climate, but species did not track the same micro-climatic feature to flower. At the growing-season time-scale, the air surrounding the plants was the most common trigger of the blooming period. However, at the annual time-scale, the snowmelt date was the main controlling factor for flowering time, even in warmer climate. Moreover, spatial patterns of the snowmelt influenced the developmental rate of the species because in later snowmelt sites the plants needed a lower level of heat accumulation to enter anthesis. Phenological responses to experimental warming differed among species, were proportional to the pre-flowering time-span of plants, and did not show consistent trends of change over time. Finally, warmer temperature produced an overall increase of flowering synchrony both within and among plant species.

The memory of water: Archaeobotanical evidence of wetland plants from Modena (Emilia-Romagna, northern Italy) and palaeoecological remarks

Modena, founded by the Romans (183 BC), has always been conditioned by water in all its urban history. In the city, numerous archaeobotanical investigations have been carried out in order to reconstruct the natural landscape and human–environment interactions over time. During these investigations, four archaeological sites (two Roman and two medieval) have revealed deposits with a marked character of palaeobiocoenosis, largely resulting from the natural environment surrounding the sites, due to natural “seed rain”. These deposits are characterized by widespread evidence of plants related to water, constituting a valuable archive to investigate habitats which currently have become very rare and threatened, if they have not completely disappeared. The present paper aims to reveal the peculiarities of the Roman/medieval archaeocarpological floristic lists (through a comparison with the flora over the last two centuries in the area of Modena) and highlight the possible causes explaining the presence or the demise of several taxa, considering also the palaeoecological reconstruction of the environment in which they have been found.

Floristic composition, site conditions and diversity of poet’s daffodil (Narcissus radiiflorus Salisb.) hay meadows in the Venetian Pre-Alps and outer Dolomites (N-Italy): implications for conservation and restoration

Abstract Hay meadows are an important component of the alpine landscape, which evolved over millennia of human activities. When traditionally managed, hay meadows support a rich flora and are recognized for high species diversity. However, both intensification and abandonment can lead to a loss of biodiversity in this vegetation. In this paper, the focus was on the hay meadows where Narcissus radiiflorus Salisb. forms white mosaic carpets during the blooming period. This vegetation was studied through 26 phytosociological relevés, taken in the Venetian Pre-Alps and outer Dolomites (Northern Italy). Relevés were numerically classified and analysed in their relationships with site conditions. Moreover, diversity metrics were calculated for detecting the conservation status of hay meadows subjected to different types of disturbance. The results showed that poet’s daffodils’ dominance brings together hay meadows showing a substantial range of floristic and ecologic variation and that part of the stands dominated by Narcissus radiiflorus could be referred to a habitat type regarded as prioritary for nature conservation. Moreover, management-related variations in functional diversity suggested that the best practice recommended for conservation and restoration of this habitat is the continuation of traditional late mowing. This practice will allow preserving both biodiversity and ecosystem functions and services.