European Journal of Soil Science最新文献

Northern peatlands are important pools of soil organic carbon (SOC) and show a fine-scale feature of hummocks and hollows. However, there remains uncertainty about the magnitude of SOC–climate feedbacks because of the knowledge gap about the fine-scale spatial pattern and temperature sensitivity (Q₁₀) mechanism of SOC decomposition. We collected peatland soils from the Greater Khingan Mountains in Northeastern China to investigate how soil enzyme kinetics control the hummock–hollow pattern of the Q₁₀ of SOC decomposition. Results revealed that soil enzyme kinetic parameters (maximum reaction velocity [V_max] and Michaelis constant [K_m]) were greater in hollows compared to hummocks. In the 0–15 cm depth, the catalytic efficiencies (K_cat) of β-1,4-glucosidase (BG) and acid phosphatase (AP) were greater in hollows than in hummocks, but the K_cat of 4-N-acetylglucosaminidase (NAG) was reversed. In the 15–30 cm depth, the K_cat of NAG and AP was greater in hollows than in hummocks, but the K_cat of BG was reversed. Except for the K_m of NAG, all enzyme kinetic parameters increased with rising temperature. The Q₁₀ values of V_max and K_m were greater in hummocks than in hollows, with Q₁₀ values of V_max ranging from 1.48 to 2.22 and from 1.12 to 2.12 for hummocks and hollows, respectively. Similarly, the Q₁₀ values of K_m ranged from 0.70 to 1.67 and from 0.55 to 1.50 for hummocks and hollows, respectively. A positive correlation was observed between V_max and K_m, indicating that increases in K_m may counterbalance increases in V_max as temperature rises. The Q₁₀ values for SOC decomposition were greater in hummocks than in hollows, with average Q₁₀ values of 3.5 and 1.5 when temperature increased from 5°C to 15°C, respectively. Soil TP and the Q₁₀–V_max of NAG and AP have emerged as the best predictors of Q₁₀ values for SOC decomposition, and they were positively correlated with the Q₁₀ values for SOC decomposition. The larger phosphorus content and the high temperature sensitivity of hydrolase activities on hummocks suggest they would have a high potential for carbon mineralisation in the background of climate warming. These findings suggest that soil enzyme kinetic parameters and their Q₁₀ provide valuable tools for predicting the response of microbially mediated SOC decomposition to climate warming scenarios.

Soil organic carbon (SOC) plays a critical role in regulating ecosystem functions and mitigating climate change. Understanding the factors that influence SOC dynamics, particularly the effect of activation energy (E_a) on SOC sequestration, is essential for predicting soil carbon responses to environmental changes. E_a refers to the minimum energy required for SOC decomposition to occur, and it is influenced by biotic and abiotic factors. This study investigated the effects of plant traits, geoclimatic and soil properties on E_a. A total of 540 soil samples from 1 m soil profiles beneath 10 plant species at seven sites were collected in black soil regions of China and analysed for E_a and other respiration parameters,including maintenance respiration (R₀), mean respiration rates (R_mean), temperature sensitivity (Q₁₀) and respiration variability (R_variability) measurements, under laboratory incubations. We also designed plant litter addition experiments (0, 1, 2, 4, 8 species) to identify litter diversity effects on these indices. Our findings revealed that litter diversity and plant species identity were the primary drivers of E_a variations, exerting 2.2-fold and 5.4-fold greater influences than geoclimatic and soil factors, respectively. Furthermore, litter addition significantly enhanced E_a by 33%, with increasing litter diversity positively correlated with elevated E_a values. Larix gmelinii exhibited 2.7-fold and 1.2-fold higher E_a than Populus xiaohei and Quercus mongolica, respectively. Structural equation modelling (SEM) testified that high E_a promotes elevated R₀ and R_mean, ultimately enhancing C accumulation in glomalin-related soil proteins (GRSP), which include glycoproteins produced by arbuscular mycorrhizal fungi in soil. Our findings highlighted that diverse litter returns to soils and afforestation with suitable species (e.g., L. gmelinii) could increase SOC sequestration, which depends on GRSP-C accrual induced by the increase in E_a.

Sulfur (S) fertilization can alter the distribution of soil S fractions with varying degrees of bioavailability. However, long-term studies on the accumulation of these fractions and their relationship with plant availability are limited. This study aimed to: (i) quantify changes in soil S fractions using both physical and chemical fractionation methods, and (ii) assess their relationship with S bioavailability, as indicated by uptake in a test crop, after 10 years of continuous phosphorus (P) and S fertilization. The experiment consisted of a factorial combination of three P rates (0, 20, and 40 kg P ha⁻¹) and four S rates (0, 12, 24, and 36 kg S ha⁻¹) applied to cereals from 2000 to 2010, within a crop sequence of maize—full season soybean—double-cropped wheat/soybean. In 2010, a maize crop was sown as a test crop, and S uptake was considered indicative of bioavailable S. Soil samples were collected before sowing the test crop in 2010, and S fractions were separated physically as S in particulate organic matter (S-POM) via wet sieving, and chemically into inorganic S (Sin), ester sulfate (SOC; organic S not directly bound to C), and C-bonded organic S (SC). After 10 years of fertilization, S-POM, Sin, and SOC increased by 60%, 300%, and 83%, respectively, corresponding to increases of 4.6, 2.8, and 24.8 mg kg⁻¹ per 100 kg of cumulative applied S. S uptake by the test crop was positively associated with Sin and SOC, with uptake increases of 1.7 and 0.18 kg S ha⁻¹ for each 1 mg kg⁻¹ increase in these fractions, respectively. These results suggest that the Sin and SOC fractions explained the residual effects of 10 years of S fertilization in a Typic Argiudoll of the Pampas region, and may serve as reliable soil indicators for assessing long-term S fertility.

Phosphorus (P) is a crucial limiting nutrient in grassland ecosystems. Microorganisms play a vital role in soil P cycling and bioavailability. Grassland grazing profoundly affects soil P cycling, while the role of microbial-driven mechanisms in the regulation of soil P fractions by grazing intensity is yet unclear. Here, soil samples, primarily classified as calcic Chernozems, were collected from a long-term grazing experiment with grazing intensity gradients (0.0, 1.5, 3.0, 4.5, 6.0, 7.5, 9.0 sheep ha⁻¹) in a semi-arid grassland of Inner Mongolia. Soil chemical properties, P fractions, phospholipid fatty acid (PLFA) and functional gene abundance of inorganic P (Pi) solubilisation (pqqC) and organic P (Po) mineralisation (phoD) were measured. As grazing intensity increased, soil pH increased while soil dissolved nitrogen (DN) decreased. The marked decline in soil total PLFAs resulted in a linear reduction in soil labile Po. The gradual increase in pqqC gene abundance and constant phoD gene abundance with increasing grazing intensity suggested that the Pi solubilisation processes, not Po mineralisation processes, were pivotal for soil P transformation when the soil microbial community's growth was limited. The enhanced soil Pi solubilisation reduced soil moderately labile Pi, which in turn affected soil moderately resistant Pi and labile Pi. Under grazing intensity gradients, the increased soil pH and decreased soil DN were also involved in the regulation of soil P fractions' transformations via affecting soil total PLFAs and pqqC gene abundance. Our findings underscore the importance of Pi solubilisation processes in regulating soil P cycling under long-term grazing intensity gradients, thereby providing valuable insights for sustainable grassland management and ecosystem conservation in semi-arid regions.

Although the addition of biochar has been shown to improve soil quality, previous studies have applied biochar at a far higher rate than is realistic for many resource-poor farmers in the tropics. Thus, in order to be able to draw general conclusions, long-term experiments are required that mimic low-input cropping systems. This study aimed to determine the effect of continuous application of biochar-based soil amendments in a low-input cropping system on selected soil quality attributes, such as soil aggregation, labile carbon fractions, and litter decomposition rate. Different biochar-based soil amendments, namely (i) lignocellulosic biochar, (ii) bone char, and (iii) a biochar and compost mixture, were applied continuously for 9 years at a rate of 4 t ha⁻¹ y⁻¹. The effect of the biochar-based soil amendments was then compared with the mineral fertilizer treatment and the control (i.e., without chemical fertilizers and organic amendments). Compared with the control, the biochar-based soil amendments increased the mean weight diameter of soil aggregates (MWD) by 40%–70%, permanganate oxidized carbon (POXC) content by 45%–98%, particulate organic matter (POMC) content by 200%–300%, and microbial biomass carbon (MBC) content by 80%–180%. Similarly, the biochar-based soil amendments increased MWD, POXC, POMC, and MBC contents compared with the mineral fertilizer treatment (p < 0.001). This study demonstrates the benefits of applying biochar-based soil amendments for a long period, despite their low application rate. Such long-term experiments are crucial for sustainable environmental management because biochar remains in soils for centuries.