Changes in snow cover depth and duration predicted by climate change scenarios are expected to strongly affect high-altitude ecosystem processes. This study investigates the effect of an ...exceptionally short snow season on the phenology and carbon dioxide source/sink strength of a subalpine grassland. An earlier snowmelt of more than one month caused a considerable advancement (40 days) of the beginning of the carbon uptake period (CUP) and, together with a delayed establishment of the snow season in autumn, contributed to a two-month longer CUP. The combined effect of the shorter snow season and the extended CUP led to an increase of about 100% in annual carbon net uptake. Nevertheless, the unusual environmental conditions imposed by the early snowmelt led to changes in canopy structure and functioning, with a reduction of the carbon sequestration rate during the snow-free period.
Aims
Grasslands are among the largest ecosystems in the world and store up to 30% of the global reserves of carbon. Decomposition processes have a crucial role in maintaining carbon balance, but few ...studies have investigated the heterogeneity of this process at small scale, especially in alpine ecosystems. We aimed at investigating the interactions between decomposition and environmental heterogeneity at microscale (i.e. elevation gradient <1 m) in a subalpine grassland on the western Italian Alps characterised by the presence of parallel hummock and hollow areas.
Methods
In the study area we monitored microenvironmental drivers (soil temperature and soil water content), plant distribution and decomposition. The latter was studied through a litter bags approach followed by elemental analysis,
13
C NMR and FT-IR spectroscopies.
Results
Microtopography exerted a direct and indirect control over litter decomposition by affecting plant species distribution and microclimatic conditions. The different elemental and biochemical properties of plants, interacting with microtopography, led to a higher decomposition rate of forb than grass litter, and in hollow than in hummock areas. The observed differences were both quanti- and qualitative.
Conclusions
Decomposition processes bridge the gap between plant community structure and ecosystem functioning, determining a feedback mechanism that maintains ecosystem heterogeneity at the microscale.
Fallopia japonica succeeds in invading different ecosystems likely because of its huge biomass production. This biomass is characterized by low nutritional quality and low decomposition rates but ...knowledge on whether these features are correlated to microbial decomposers is still lacking. The aims of this work were: i) to determine litter decomposition rates of native grassland vegetation and F. japonica under different conditions in a year-round experiment; ii) to evaluate litter quality and/or site effect on the decomposition of the invader and native vegetation and iii) to characterize mycoflora isolated from F. japonica and native vegetation litter. The results showed that F. japonica litter decomposes 3–4 times slower than that of native grassland, mainly due to its low N content and consequently high C/N ratio both in leaves and stems. As decomposition proceeds C/N in F. japonica litter decreases to values approaching those of the grassland litter. Site had no effect on the decomposition rates of F. japonica and grassland litter. Total fungal load and composition differed between F. japonica and native litter, and also varied across sites. These results indicate that the successful invasive plant F. japonica affects the structure and functions of the invaded ecosystem through a huge production of low quality, slow-decomposing litter that selects saprotrophic fungi.
•F. japonica litter decomposition is 3–4 times slower than that of native litters.•C/N of F. japonica litter decreases progressively to reach the values of the grassland.•No differences were detected in litter decomposition due to the environment.•Differences occurred in mycoflora associated with alien and grassland litter.•F. japonica alters ecosystems through the large amount of low quality litter.
This research aims at developing a remote sensing technique for monitoring the interannual variability of the European larch phenological cycle in the Alpine region of Aosta Valley (Northern Italy) ...and to evaluate its relationships with climatic factors. Phenological field observations were conducted in eight test sites from 2005 to 2007 to determine the dates of completion of different phenological phases. MODerate Resolution Imaging Spectrometer (MODIS) 250 m 16‐days normalized difference vegetation index (NDVI) time series were fitted with double logistic curves and the dates corresponding to different features of the curves were determined. Comparison with field data showed that the features of the fitted NDVI curve that allowed the best estimate of the start and end of the growing season were the zeroes of its third derivative (MAE of 6 and 4 days, respectively). The start and end of season were also estimated with the spring warming (SW) and growing season index (GSI) phenological models. MODIS start and end of season dates generally agreed with those obtained by the SW and GSI climate‐driven phenological models. However, phenological models provided erroneous results when applied in years with anomalous meteorological conditions. The relationships between interannual variability of the larch phenological cycle and climate were investigated by comparing the mean start and end of season yearly anomalies with air temperature anomalies. A strong linear relationship (R2=0.91) was found between mean spring temperatures and mean start of season dates, with an increase of 1 °C in mean spring temperature leading to a 7‐day anticipation of mean larch bud‐burst date. Leaf coloring dates were found to be best related with mean September temperature (R2=0.77), but with higher spring temperatures appearing to lead to earlier leaf coloring.
Short-term changes occurring in high mountain vegetation were analysed using the data from two Italian sites already part of the GLobal Observation Research Initiative in Alpine environments (GLORIA ...– central Apennines and southwestern Alps). The study focused on a set of floristic (endemics), structural (life forms) and ecological (thermic vegetation indicator) variables. Vegetation data were collected according to the GLORIA multi-summit standardized method during the last decade. The re-visitation revealed a moderate decrease in regional endemic flora and significant variations in structural and ecological parameters. The increase in caespitose hemicryptophytes in both sites, in suffruticose chamaephytes in the central Apennines and in rosette-forming hemicryptophytes in the southwestern Alps emerged, highlighting the rapid responses of the alpine vegetation to climate warming. The increase in perennial life forms is related with the expansion of graminoids and small woody plants. These life forms seem to be most suitable to face climate warming in Italian summits. The increase in the thermic vegetation indicator exceeds the mean European summits increment, and this is due to the expansion of thermophilic species. Short-term analyses with fine spatial and temporal resolutions are still necessary to improve our understanding concerning species behaviour in high-elevation ecosystems.
More nature in the city Capotorti, G; Bonacquisti, S; Abis, L ...
Plant biosystems,
11/2020, Letnik:
154, Številka:
6
Journal Article
Recenzirano
Odprti dostop
According to projects and practices that the Italian botanists and ecologists are carrying out for bringing “more nature in the city”, new insights for a factual integration between ecological ...perspectives and more consolidated aesthetic and agronomic approaches to the sustainable planning and management of urban green areas are provided.
Alien invasive plants threaten biodiversity, productivity and ecosystem functioning throughout the world. We examined the effect of Fallopia japonica on two native grassland species (Trifolium ...repens, Lolium perenne). We hypothesized that its negative effects on the native species are dependent on three mechanisms: (i) allelochemicals released and accumulated in soil with a history of invasion, (ii) altered soil biota and (iii) direct resource competition. We measured the response of the native species as the difference in their functional traits when grown under the three conditions. Our results demonstrate that neither allelochemicals nor soil biota from soil with history of F. japonica invasion had measurable effects on either species. Competition with the invader strongly reduced height, biomass and specific leaf area (SLA) of T. repens, while it had a lower effect on L. perenne. Furthermore, our results reveal that F. japonica took advantage of a positive plant-soil and plant-plant interaction. The results show that the prominent mechanism underpinning the invasion success of F. japonica in the grassland was the direct resource competition. This prominent role is also confirmed by the significant interactions between competition, allelochemicals and soil biota from soils with history of invasion of F. japonica on SLA of the native species.
In this work the occurrence of non-native species was recorded along the elevation gradient in the Alps, in order to establish their distribution pattern, their current altitudinal limits and to ...elucidate which species are presumably adapted to higher elevations. Plots were located along the course of rivers in five valleys from 100 to 2100 m a.s.l. Sixty-eight non-natives were recorded in the study area. The proportion of invasives was found to be much higher in the study area then in the whole administrative region. The number of non-natives per plot decreased strongly with increasing elevation. The great majority (94%) of the non-native species grows at the lowest elevations, while only 6% survive up to 1500 m and none was found above this limit. Results were interpreted considering the factors driving the invasion process (disturbance, the native communities' resistance to invasion, propagule pressure, climatic conditions) and plant traits with particular respect to pre-adaptation to the harsh climate, which increases progressively with elevation. Results confirm that the Alps are not immune from invasion, at least up to medium elevation.
The spread of the invasive and allergenic Ambrosia artemisiifolia L. in Italy was analysed and mapped using distribution data from a wide range of sources. Ambrosia artemisiifolia occupies 1057 ...floristic quadrants which are mostly distributed in the Po plain. The distribution obtained represents the basis to implement urgent management strategies.