Higher Carbon Mineralization Research Articles

Exploring the mystery of soil carbon mineralization: Insights from incubation experiments and kinetic modeling

Soil carbon mineralization is vital for carbon sequestration but affected by factors like soil type and residue quality. Understanding the process and factors is still incomplete, including the interplay between soil properties and organic residues and the need for accurate kinetic models. Research faces significant challenges in describing carbon mineralization dynamics. The present study aimed to investigate carbon mineralization in three soils located in Tamil Nadu, India (S1, S2 and S3) that possess distinct textures. The study also focused on the effects of five different plant residues (Rice, maize, sugarcane, cotton and turmeric) on carbon mineralization in these soils. Incubation experiments were conducted for 150 days, and CO2 evolution was measured at different time intervals of 7, 10, 15, 30, 60, 90, 120 and 150 days. The performance of three kinetic models (Zero order model, exponential kinetic model and first order model) was also evaluated in predicting carbon mineralization using experimental data. The results showed that the rate and extent of carbon mineralization varied significantly among the different soils and residues. The highest carbon mineralization was observed in rice (989.02 µg C/g/day) and maize (966.53 µg C/g/day) residue, while the lowest was in sugarcane (752.09 µg C/g/day) residue. Among the kinetic models, the first-order kinetic model provided the best fit for all treatments (R2=0.98). The findings suggest that soil texture and residue quality play crucial roles in carbon mineralization. The first order kinetic model can be useful for predicting carbon mineralization in different soil-residue systems. These results have implications for managing soil carbon sequestration and mitigating climate change.

Changes in Chemical and Microbial Soil Parameters Following 8 Years of Deadwood Decay: An Experiment with Logs of 13 Tree Species in 30 Forests

Deadwood may alter the chemical and microbial properties of forest soils. However, it is unclear how downed deadwood (logs) of different tree species affect nutrients, microbial activity and biomass in different forest soils and regions. We investigated the effect of logs on underlying soils after 8 years of decomposition in an experiment consisting of 13 log tree species replicated at 30 forest sites across three German regions with distinct climate and geology. Soils beneath logs were compared to soils without recognizable influence of deadwood (control) 8 m away. Carbon, nitrogen, phosphorous and calcium concentrations increased by 5–18% in the soils under logs, whereas soil potassium, magnesium, iron, manganese and aluminum were not or slightly negatively affected by logs. Soils beneath logs exhibited 33%, 18% and 54% higher carbon mineralization, microbial biomass and ergosterol (component of fungal cell membranes) contents, respectively. Despite major differences in decay rates, the effect on soil properties hardly differed among the 13 log tree species. The effect of logs on microbial and chemical soil parameters increased with decreasing concentration of carbon, nitrogen, phosphorous and pH in the prevailing forest soils. Consequently, the strongest effects of logs on soil parameters occurred in plots with low soil nutrient contents and low soil pH. Our results suggest that logs of all tree species primarily increase the microbial activity and nutrient contents of acidic and nutrient-poor soils.

How titanium dioxide and zinc oxide nanoparticles do affect soil microorganism activity?

The increasing use of nanoparticles (NPs) in recent years has posed a potential threat to the natural ecosystem. The aim of this study was to determine the C and N mineralizations of different textured (clay and sandy) soils at increasing doses of (25, 50 and 100 mg kg−1) TiO2 NPs and ZnO NPs that are biological synthesized from Peganum harmala L. plant extract, and to reveal their potential effects on the soil ecosystem. The carbon (C) and nitrogen (N) mineralizations were respectively determined by the CO2 respiration method and the Parnas-Wagner method under the controlled laboratory conditions for 42 days (28 °C, 80% of field capacity). The highest carbon mineralization among all applications was in clay soils mixed with 100 mg kg−1 TiO2 NPs. In clay soils treated with ZnO NPs, the treatment of 50 mg kg−1 ZnO NPs increased microorganism activity (P < 0.001). Carbon mineralization rates were found to be higher in sandy soils compared to clay soils (P < 0.05). It was observed that these rates were higher in the TiO2 NPs treated soils compared to the ZnO NPs treated soils. The nitrogen mineralization ratios were found to be higher in clay soils compared to sandy soils. All of these results indicate that the microorganisms affected from both the presence of TiO2 NPs and ZnO NPs and differences of texture in these two soils.

残落物添加对农林复合系统土壤有机碳矿化和土壤微生物量的影响

The forest litter and crop straw residues are important components in the agroforestry system and play a key role in ecosystem carbon and nutrient cycle.During decomposition,to a great extent,the carbon mineralization is controlled by soil microorganisms.However,the quality of mixtures with various compositions is different due to difference in chemical compositions and physical structure from single component.Moreover,frequent addition of residues is reported to be able to keep the easily available compounds in soils in a high level.All the factors mentioned above were considered to have important effects on soil microbial activity.However,the effects of residue composition and addition frequencies on carbon mineralization,microbial biomass carbon and nitrogen have been seldom reported in the soil of agroforestry system.Poplars are the major tree component of traditional agroforestry systems throughout the south temperate central area of China.In this paper,an experiment was designed to study the influnce of different residue compositions and addition frequencies on carbon mineralization,microbial biomass carbon and nitrogen in the soil of poplar-wheat agroforestry system.The clay loam and silty loam in the experiment were collected from Sihong and Dafeng County of northern Jiangsu Province.The six treatments in the experiment were W: 16 g/kg(soil) wheat straw residue;P1: 16 g/kg(soil) poplar leaf litter;P1-W: 16 g/kg(soil) mixture of poplar leaf and wheat straw residue with 1 ∶1;P2: adding 4 g/kg(soil) poplar leaf litter every 8 days;P2-W: adding 2 g/kg(soil) poplar leaf litter every 8 days and 8 g/kg(soil) wheat straw residue at the first day,and CK: the control(without any addition).The soils with different treatments were incubated under the temperature of 25℃ at daytime and 15℃ at night for 31 days.The results showed that,for all the residue addition treatments,the carbon mineralization rates were higher in the daytime with the temperature of 25℃ than those in the night with 15℃(P 0.05).For the soils,the silty loam showed higher carbon mineralization rates than clay loam(P 0.05).After 8 days of incubation,the treatment P2 and P2-W showed higher carbon mineralization rates than the other treatments(p0.05),and the peak values occurred at 9,17,25 days.Mixed residues of poplar leaf and wheat straw could promote the cumulated carbon mineralization at the end of incubation,and the cumulated carbon mineralization was significantly higher in the treatment of adding poplar leaf litter serially(P2) than that of adding all at the first day(P1)(P0.05).Compared to the treatments of poplar leaf litter(P1) and wheat straw residues(W),mixed residues of poplar leaf and wheat straw significantly increased microbial biomass carbon and nitrogen in soil(P 0.05).Furthermore,the microbial biomass carbon and nitrogen were significantly higher in the treatment of adding poplar leaf litter serially(P2) than that of adding all at the first day(P1).However,compared to the CK,the content of soil inorganic nitrogen decreased significantly for all the residue addition treatments,especially in the mixed residues treatments(P1-W and P2-W).The results from this study suggested that residue composition and addition frequencies could enhance the decomposition process,and regulate carbon dynamic and nitrogen supply.Such study would provide an important information for a deeper understanding of the carbon and nitrogen cycle in agroforestry systems.

Tannin impacts on microbial diversity and the functioning of alpine soils: a multidisciplinary approach

In alpine ecosystems, tannin-rich-litter decomposition occurs mainly under snow. With global change, variations in snowfall might affect soil temperature and microbial diversity with biogeochemical consequences on ecosystem processes. However, the relationships linking soil temperature and tannin degradation with soil microorganisms and nutrients fluxes remain poorly understood. Here, we combined biogeochemical and molecular profiling approaches to monitor tannin degradation, nutrient cycling and microbial communities (Bacteria, Crenarcheotes, Fungi) in undisturbed winter time soil cores exposed to low temperature (0 degrees C/-6 degrees C), amended or not with tannins, extracted from Dryas octopetala. No toxic effect of tannins on microbial populations was found, indicating that they withstand phenolics from alpine vegetation litter. Additionally at -6 degrees C, higher carbon mineralization, higher protocatechuic acid concentration (intermediary metabolite of tannin catabolism), and changes in fungal phylogenetic composition showed that freezing temperatures may select fungi able to degrade D. octopetala's tannins. In contrast, negative net nitrogen mineralization rates were observed at -6 degrees C possibly due to a more efficient N immobilization by tannins than N production by microbial activities, and suggesting a decoupling between C and N mineralization. Our results confirmed tannins and soil temperatures as relevant controls of microbial catabolism which are crucial for alpine ecosystems functioning and carbon storage.