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- Title
Soil-atmosphere interface: the impact of depositions on forest soils in Italy.
- Authors
Andreetta, Anna; Cecchini, Guia; Marchetto, Aldo; Carnicelli, Stefano
- Abstract
Acidification is a major soil-forming process. Emission of nitrogen (N) and sulphur (S)compounds has exposed forest ecosystems to acidifying anthropogenic deposition for severaldecades. Since the 1980s, the reduction of air emissions following the environmentalregulations has been resulted in a decline of pollutant depositions. Nevertheless, in Italy, Ndepositions are still high, among the highest in Europe. Nitrogen from depositions has beenfound to favour plant growth, contributing to organic carbon uptake. However, a continuousaccumulation of deposited inorganic N causes plant nutrient unbalances, and likelycontributes to soil acidification more than commonly reckoned. At the same time, depositionsof buffer elements are high and constant in Italy due to the proximity of the Saharansource. Within this context, our researches aim to explore the specific impacts ofpeculiar atmospheric deposition, hypothesising a strong influence of aeolian dusts,on forest soil ecosystem in Italy. Our main objectives are a) to evaluate the longterm trends in soil solution elemental fluxes in relation to depositions trends; b) toinvestigate the soil response to pollution change and recovery, individuating whether soilacidification is, or not, an active process; c) to identify sites where the transfer of reactiveN from atmospheric N pollution to fresh- or ground-waters is a real concern. Weanalysed data on deposition and elemental concentrations in soil solutions recorded atforest plots of the ICP Forests intensive monitoring network in Italy. We used aconceptual model based on input-output budgets estimating atmospherically derivedfluxes of elements that enter terrestrial ecosystem through deposition and losses ofelements through drainage water. For the base cation (BCE) budget, an estimateof rock-derived elements due to chemical weathering were also included in themodel. As for other countries in Europe, the concentration of SO4 in soil solutions significantlydecreased concomitantly with decreasing SO4 deposition, while, differently from theEuropean trends, an increase in BCE concentrations was found. The observed increase in soilsolution pH in northern sites followed an increase of BCE with a decrease of SO4 and nochange for NO3. In Central-Northern Italy, trends in soil solution pH were no significant;a neutralising effect on acidification was likely due to concomitant increases ofNO3 and BCE in soil solution. Further, the estimation of the overall BCE budget,comprising canopy and soil fluxes, evidenced a regular accumulation of K and Cain allsites, except for a site where soil base saturation is very high and a depletion ofCa was found. For Mg, depletion was strongly slowed down by the influence ofdeposition. It appears that in Italian forest soils, deposition of basic exchangeablecations is a major process, influencing both forest nutrition conditions and soildevelopment. Our results suggest that soil acidification should not be considered an activeprocess in forest sites of Italy. However, high inorganic nitrogen concentrations in soilsolutions were found in sites with high N deposition loads, where regular N fluxout of the rooting zone can represent a risk of ground- and fresh-water pollution.
- Subjects
ITALY; FOREST soils; SOIL acidification; SOIL solutions; SOIL pollution; CHEMICAL weathering; FOREST monitoring
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article