Initial carbonate weathering is linked with vegetation development along a 127-year glacial retreat chronosequence in the subtropical high mountainous Hailuogou region (SW China)

Abstract

Aims The retreat of glaciers is exposing new terrains to primary plant succession around the globe. To improve the understanding of vegetation development along a glacier retreat chronosequence, we (i) evaluated a possible link between base metal (Ca, Mg, K, Na) supply and vegetation establishment, (ii) determined the rates of the establishment of soil and plant base metal stocks, and (iii) estimated the size of the main base metal fluxes. Methods We determined base metal stocks in the soil organic layer, the mineral topsoil (0–10 cm), and in leaves/needles, trunk, bark, branches and roots of the dominating shrub and tree species and estimated fluxes of atmospheric deposition, plant uptake and leaching losses along the 127-yr Hailuogou chronosequence. Results Total ecosystem Ca and Mg stocks decreased along the chronosequence, while those of K and Na were unrelated with ecosystem age. Fortyfour and 30% of the initial stocks of Ca and Mg, respectively, were leached during the first 47 years, at rates of 130 ± 10.6 g m−2 year−1 Ca and 35 ± 3.1 g m−2 year−1 Mg. The organic layer accumulated at a mean rate of 288 g m−2 year−1 providing a bioavailable base metal stock, which was especially important for K cycling. Conclusions We suggest that the initial high Ca bioavailability because of a moderately alkaline soil pH and carbonate depletion in 47 years, together with the dissolution of easily-weatherable silicates providing enough Mg and K to the pioneer vegetation, contributed to the establishment of the mature forest in ca. 80 years.

Base cations release in soils along the 127‐year Hailuogou glacial retreat chronosequence

“…With increasing time, the soils have developed A and O horizons of increasing thickness. The intense carbonate weathering in the early stage of the chronosequence and the rapid establishment of the vegetation decreased soil pH from 8.0 to 5.8 in only 47 yr (Basdediós et al., 2022).…”

“…Soil pH, effective cation‐exchange capacity (ECEC), concentrations of exchangeable Ca, Mg, K, and Na, and Ca carbonate concentrations were taken from Basdediós et al. (2022). The inorganic C (i.e., after muffling the samples at 550 °C to remove organic matter) and total S concentrations of the stone fraction were determined by combustion in a CNS Elemental Analyzer (EuroEA, HEKAtech GmbH).…”

“…The fast vegetation succession is surprising, because the Gongga Mountain and the derived glacial debris is mainly composed of granite (Searle et al., 2016), a nutrient‐poor substrate, particularly with respect to Ca and Mg (Schmitt et al., 2012). However, the Hailuogou glacial debris also contains carbonates originating from meta‐sedimentary rocks (Roger et al., 1995; Searle et al., 2016), which are leached out of the topsoil in 47 yr after glacial retreat (Basdediós et al., 2022).…”

“…A mix of mineral constituents in the parent material, for example, carbonates and easily weatherable silicates, might release a wide variety of nutrients through weathering that become easily available for plant uptake. Once a soil organic layer is established, it can store and supply a large quantity of the nutrients required by the vegetation (Basdediós et al., 2022; Jobbágy & Jackson, 2004; Lilienfein et al., 2001; Wilcke et al., 2002). Because at the beginning of the vegetation succession on glacial debris the soil is usually free of organic matter, mineral weathering together with the nutrient input by atmospheric deposition drives the supply of all macronutrients but N, which is acquired by microbial N 2 fixation from the atmosphere except in bituminous sediments and metamorphites (Houlton et al., 2018).…”

“…To explain the lack of a relationship between ecosystem age and K and Na stocks, Basdediós et al. (2022) suggested that K and Na were constantly released from silicate mineral pools at low rates which were taken up by the organisms of the ecosystem with little losses.…”