Glacier shrinkage, a notable consequence of climate change, is expected to intensify, particularly in high-elevation areas. While plant diversity and soil microbial communities have been studied, research on soil organic matter (SOM) and soil protein function dynamics in glacier forefields is limited. This limited understanding, especially regarding the link between microbial protein functions and biogeochemical functions, hampers our knowledge of soil-ecosystem processes along chronosequences. This study aims to elucidate the mechanistic relationships among soil bacterial protein functions, SOM decomposition, and environmental factors such as plant density and soil pH to advance understanding of the processes driving ecosystem succession in glacier forefields over time. Proteomic analysis showed that as ecosystems matured, the dominant protein functions transition from primarily managing cellular and physiological processes (biological controllers) to orchestrating broader ecological processes (ecosystem regulators) and increasingly include proteins involved in the degradation and utilization of OM. This shift was driven by plant density and pH, leading to increased ecosystem complexity and stability. Our confirmatory path analysis findings indicate that plant density is the main driver of soil process evolution, with plant colonization directly affecting pH, which in turn influenced nutrient metabolizing protein abundance, and SOM decomposition rate. Nutrient availability was primarily influenced by plant density, nutrient metabolizing proteins, and SOM decomposition, with SOM decomposition increasing with site age. These results underscore the critical role of plant colonization and pH in guiding soil ecosystem trajectories, revealing complex mechanisms and emphasizing the need for ongoing research to understand long-term ecosystem resilience and carbon sequestration.

Rainfall can alter the hydrothermal state of permafrost, subsequently affecting organic carbon decomposition and CO2 transport. However, the mechanisms by which rainfall influences organic carbon decomposition and carbon dioxide transport processes in permafrost remain unclear. In this study, a coupled permafrost water-heatvapor-carbon model, based on the surface energy-water balance theory, is employed to explore the effects of increased precipitation on permafrost moisture, temperature, organic carbon decomposition, and carbon dioxide transport through numerical simulations. The results are as follows: (1) with increased rainfall, surface latent heat flux rises while surface sensible heat flux declines, leading to a reduction in surface heat flux. The annual mean surface heat fluxes for the three precipitation conditions of no change in precipitation (zP = 0 mm), 50 mm increase in precipitation (zP = 50 mm) and 100 mm increase in precipitation (zP = 100 mm) are -0.1 W/m2, -0.2 W/m2 and -0.4 W/m2 respectively; and (2) as rainfall increases, soil moisture content increases significantly, but the impact of rainfall on soil moisture content diminishes with increasing soil depth; and (3) increased rainfall results in a decrease in soil carbon fluxes, soil organic matter decomposition rates, and CO2 concentrations. Compared to the case of constant precipitation, the surface carbon fluxes decreased by 0.04 mu mol center dot m-2s-1 and 0.08 mu mol center dot m-2s-1 under zP = 50 mm and zP = 100 mm, respectively. Additionally, the decomposition rate of soil organic matter at 10 cm depth decreased by 3.2 E-8 mol center dot m-2s-1 and 6.3 E-8 mol center dot m-2s-1, respectively, while the soil carbon concentration decreased by 3 mu mol/mol and 5 mu mol/mol, respectively.

Cryosols in tundra ecosystems contain large stocks of organic carbon as peat and as organic cryoturbated layers. Increased organic mater decomposition rate in those Arctic soils due to increasing soil temperatures and to permafrost thawing can lead to the release of greenhouse gases, thus potentially creating a positive feedback on global warming. Instrumentation was installed on permafrost terrain in Salluit (Nunavik, Canada; 62 degrees 14'N, 75 degrees 38'W) to monitor respiration of two Cryosols under both natural and experimental warmed conditions and to simultaneously monitor the soil solution composition in the active layer throughout a thawing season. Two experimental sites under tussock tundra vegetation were set up: one is on a Histic Cryosol (H site) in a polygonal peatland; the other one is on a Turbic Cryosol reductaquic (T site) on post-glacial marine clays. At each site an open top chamber was installed from mid-July to the end of August 2010 to warm the soil surface. Thermistors and soil moisture probes were installed both in natural (N), or non-modified, surface thermal conditions and in warmed (W) stations, i.e. under an open top chamber. At each station, ecosystem respiration (ER) was measured three times per day every second day with an opaque closed chamber linked to a portable IRGA. Soil solutions were also sampled every alternate day at 10, 20 and 30 cm depths and analysed for dissolved organic C (DOC), total dissolved nitrogen (TON) and major elements. The experimental warming thickened the active layer in the Histic soil while it did not in the Turbic soil. In natural conditions, average ER at the HN station (1.27 +/- 0.32 mu mol CO2 m(-2) s(-1)) was lower than at the TN station (1.96 +/- 0.41 mu mol CO2 m(-2) s(-1)). A soil surface warming of 2.4 degrees C lead to a similar to 64% increase in ER at the HW station. At the TW station a similar to 2.1 degrees C increase induced an average ER increase of similar to 48%. Temperature sensitivity of ER, expressed by a Q(10) of 2.7 in the Histic soil and 3.9 in the Turbic Cryosol in natural conditions, decreased with increasing temperatures. There was no difference in soil solution composition between the N and W conditions for a given site. Mean DOC and TDN contents were higher at the H site. The H site soil solutions were more acidic and poorer in major solutes than the T ones, except for NO. The induced warming increased CO2 fluxes in both soils; this impact was however more striking in the Histic Cryosol even if ER was lower than in the Turbic Cryosol. In the Histic Cryosol, the thickening of the active layer would made available for decomposition new organic matter that was previously frozen into permafrost; due to acidic conditions, CO2 would be directly emitted to atmosphere. In contrast, the smaller increase in ER in the Turbic Cryosol may indicate the lack of organic matter input and carbon stabilization because of cold, non-acidic and more concentrated soil solutions; at this site warming mainly stimulates plant-derived respiration without decomposing a newly available carbon pool. (C) 2013 Elsevier Ltd. All rights reserved.