Soil organic carbon (SOC) rapidly accumulates during ecosystem primary succession in glacier foreland. This makes it an ideal model for studying soil carbon sequestration and stabilization, which are urgently needed to mitigate climate change. Here, we investigated SOC dynamics in the Kuoqionggangri glacier foreland on the Tibetan Plateau. The study area along a deglaciation chronosequence of 170-year comprising three ecosystem succession stages, including barren ground, herb steppe, and legume steppe. We quantified amino sugars, lignin phenols, and relative expression of genes associated with carbon degradation to assess the contributions of microbial and plant residues to SOC, and used FT-ICR mass spectroscopy to analyze the composition of dissolved organic matter. We found that herbal plant colonization increased SOC by enhancing ecosystem gross primary productivity, while subsequent legumes development decreased SOC, due to increased ecosystem respiration from labile organic carbon inputs. Plant residues were a greater contributor to SOC than microbial residues in the vegetated soils, but they were susceptible to microbial degradation compared to the more persistent and continuously accumulating microbial residues. Our findings revealed the organic carbon accumulation and stabilization process in early soil development, which provides mechanism insights into carbon sequestration during ecosystem restoration under climate change.

Glacier foreland soils are known to be essential methane (CH4) consumers. However, global warming and increased glacier meltwater have turned some foreland meadows into swamp meadows. The potential impact of this change on the function of foreland soils in methane consumption remains unclear. Therefore, we collected Tibetan glacier foreland soils in the non-melting season from typical microtopography in swamp meadows (hummock and hollow). Three soil moisture conditions (moist, saturated, and submerged) were set by adding glacier runoff water. Soil samples were then incubated in the laboratory for two weeks at 10 center dot C and 20 center dot C. About 5 % of 13CH4/12CH4 was added to the incubation bottles, and daily methane concentrations were measured. DNA stable isotope probing (DNA-SIP) and highthroughput sequencing were combined to target the active methanotroph populations. The results showed that type Ia methanotrophs, including Crenothrix, Methylobacter, and an unclassified Methylomonadaceae cluster, actively oxidized methane at 10 center dot C and 20 center dot C. There were distinct responses of methanotrophs to soil moisture rises in hummock and hollow soils, resulting in different methane oxidation potentials. In both hummock and hollow soils, the methane oxidation potential was positively correlated with temperature. Furthermore, saturated hummock soils exhibited the highest methane oxidation potential and methanotroph populations, while submerged hollow soils had the lowest. This suggests that the in-situ hummock soils, generally saturated with water, are more essential than in-situ hollows, typically submerged in water, for alleviating the global warming potential of swamp meadows in the Tibetan glacier foreland during the growing season.

Glaciers retreating due to global warming create important new habitats, particularly suitable for studying ecosystem development where nitrogen is a limiting factor. Nitrogen availability mainly results from microbial decomposition and transformation processes, including nitrification. AOA and AOB perform the first and rate-limiting step of nitrification. Investigating the abundance and diversity of AOA and AOB is essential for understanding early ecosystem development. The dynamics of AOA and AOB community structure along a soil chronosequence in Tianshan No. 1 Glacier foreland were analyzed using qPCR and clone library methods. The results consistently showed low quantities of both AOA and AOB throughout the chronosequence. Initially, the copy numbers of AOB were higher than those of AOA, but they decreased in later stages. The AOB community was dominated by Nitrosospira cluster ME, while the AOA community was dominated by the soil and sediment 1. Both communities were potentially connected to supra- and subglacial microbial communities during early stages. Correlation analysis revealed a significant positive correlation between the ratios of AOA and AOB with soil ammonium and total nitrogen levels. These results suggest that variations in abundance and diversity of AOA and AOB along the chronosequences were influenced by ammonium availability during glacier retreat.

We assessed patterns in soil development at a recently deglaciated foreland on Anvers Island on the Antarctic Peninsula. Soil samples were collected along transects extending 35 m over bare ground from the edge of a receding glacier; the far end of these transects has been ice free for approximately 20 years. We also compared soils at the far end of these transects under bare ground to those under canopies of isolated individuals of Deschampsia antarctica, a caespitose grass, that had recently colonized the site (established for < 6 years). In addition, we compared soils at this young foreland to those in a well-developed tundra island that has been ice free for at least several hundred years. At the foreland site, soil moisture was greatest near the glacier, consistent with proximity to meltwater, and declined with distance from the glacier. This decline in soil moisture may explain the decrease in litter decomposition rates and the greater soil nitrate (NO3 (-)) concentrations that we observed with distance from the glacier. The greater soil moisture near the glacier likely promoted leaching and transport of NO3 (-) to drier soils away from the glacier. The presence of D. antarctica at the glacier foreland had little effect on soil properties, which is not surprising considering it had only colonized sampling areas during the previous 5 years. Compared to the foreland, which contained only mineral soil, soil at the older tundra site had a 2.5- to 5-cm-thick organic horizon that had much higher concentrations of total carbon, nitrogen, and NO3 (-).