Abstract
Forests are the most important land ecosystems that can mitigate the earth’s ongoing climate change through their ability to sequester CO2 as C stock in forest biomass and soil. Short-rotation deciduous hardwoods or N2-fixing species are ideal candidates for afforestation and reforestation, given that most of the carbon accumulates in the first 30 years. Alders match both of the above-mentioned features, and Italian alder, which is less dependent on riparian habitats and more drought tolerant, is an ideal candidate. Despite this, few studies exist of this tree species and its effect on soil organic matter. In this study, we focused on litter input and leaf litter decomposition dynamics, forest floor leaf litter and topsoil (0–5 cm) organic matter, and patterns of covariation from litter to topsoil. The leaf litter was rich in nitrogen and decomposed quickly (k = 0.002 day−1). There was a large organic carbon stock, which varied in the leaf litter (from 1.7 ± 0.3 Mg/ha in January to 0.4 ± 0.1 Mg/ha in July) and was stable in the topsoil (on average 28.6 ± 1.5 Mg/ha). Stocks for total nitrogen, cellulose, lignin, water and ethanol extractables, and total phenols were also evaluated. In order to investigate patterns of covariation in these stocks from litter to soil, we used two-block partial least squares. The first axis showed that from January to July there was a reduction of total nitrogen, lignin and cellulose in the forest floor leaf litter, while in the topsoil there was a decrease in water extractables and total organic carbon. The second axis showed minor phenomena involving phenols, water and ethanol extractables, and total N. The fast turnover of dissolved organic matter fractions (water and ethanol extractables), linked with cellulose and lignin dynamics, might suggest that within the Italian alder ecosystem there is a reasonably fast formation of stable C compounds in the soil. Thus, Italian alder is an ideal species for afforestation and reforestation, which could be particularly interesting for land-use policies.
Highlights
Forests are the most important land ecosystems that can mitigate the earth’s ongoing climate change [1]
We focused on: (a) litter input and leaf litter decomposition dynamics; (b) forest floor leaf litter and topsoil (0–5 cm) organic matter quality and quantity; and (c) patterns of covariation between the litter and topsoil
Our study aims to provide wide-ranging insight into organic matter quantity and dynamics in an Italian-alder-dominated ecosystem, which can be used to evaluate the potential impact of this species on soil during afforestation or reforestation strategies
Summary
Forests are the most important land ecosystems that can mitigate the earth’s ongoing climate change [1]. Carbon (C) stock in forest biomass and soil is mostly responsible for this mitigation potential [2,3,4]. The aforementioned stock is the highest in the organic and mineral soils of temperate and boreal forests [5]. In temperate forest ecosystems, a key role belongs to the tree species that make up the largest part of the forest canopy [15,16,17]. Plantations with fast-growing tree species could mitigate CO2 emissions as their woody biomass could be a possible substitute for fossil fuels [19]
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