Mineralisation of organic matter in intact versus sieved/refilled soil cores

Soil Research ◽  
2002 ◽  
Vol 40 (1) ◽  
pp. 149 ◽  
Author(s):  
R. Stenger ◽  
G. F. Barkle ◽  
C. P. Burgess
Keyword(s):  
Organic Matter ◽  
N Mineralisation ◽  
Soil Cores ◽  
Nitrogen Mineralisation ◽  
Soil C ◽  
Soil Microbial ◽  
Conditioning Period ◽  
Incubation Study ◽  
Soil C And N ◽  
C And N

In a 6-month laboratory incubation study, we compared the net C and N mineralisation of the soil organic matter (SOM) of 3 pasture soils and the mineralisation of glucose-C in intact versus sieved/refilled soil cores. The main questions were whether the net C and N mineralisation differed between intact and sieved/refilled soil cores after a conditioning period of 4 weeks, and how much the C and N mineralisation of SOM differed among the similarly managed pasture soils. Apart from the net nitrogen mineralisation in one soil, there were no significant differences in cumulated mineralisation of C or N from SOM between the core types. In a fine-textured soil, net mineralisation of glucose-C differed significantly between core types, which was attributed to the different distribution of the amended glucose in intact and sieved/refilled cores. Net C and N mineralisation of SOM were closely correlated in the sieved/refilled cores, whereas no significant correlation was found in the intact cores. Expressing net C and N mineralisation as percentages of total soil C and N showed a more than 2-fold maximum difference between the soils in spite of similar long-term organic matter input. Subsequent studies should be done using more replicates and wider diameter, better controllable cores on ceramic plates. CO2, net nitrogen mineralisation (NNM), soil microbial biomass.

The magnitude of temperature increase matters: how will soil organic mineralization respond to future climate warming?

2020 ◽  
Author(s):  
Jie Zhou ◽  
Yuan Wen ◽  
Lingling Shi ◽  
Michaela Dippold ◽  
Yakov Kuzyakov ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Climate Warming ◽  
Temperature Increase ◽  
Microbial Growth ◽  
N Cycling ◽  
Soil C ◽  
Soil Microbial ◽  
Soil C And N ◽  
C And N ◽  
C And N Cycling

<p>The Paris climate agreement is pursuing efforts to limit the increase in global temperature to below 2 °C above pre-industrial level. The overall consequence of relatively slight warming (~2 °C), on soil C and N stocks will be dependent on microorganisms decomposing organic matter through release of extracellular enzymes. Therefore, the capacity of soil microbial community to buffer climate warming in long-term and the self-regulatory mechanisms mediating soil C and N cycling through enzyme activity and microbial growth require a detailed comparative study. Here, microbial growth and the dynamics of enzyme activity (involved in C and N cycling) in response to 8 years warming (ambient, +1.6 °C, +3.2 °C) were investigated to identify shifts in soil and microbial functioning. A slight temperature increase (+1.6 °C) only altered microbial properties, but had no effect on either hydrolytic enzyme activity or basic soil properties. Stronger warming (+3.2 °C) increased the specific growth rate (μ<sub>m</sub>) of the microbial community, indicating an alteration in their ecological strategy, i.e. a shift towards fast-growing microorganisms and accelerated microbial turnover. Warming strongly changed microbial physiological state, as indicated by a 1.4-fold increase in the fraction of growing microorganisms (GMB) and 2 times decrease in lag-time with warming. This reduced total microbial biomass but increased specific enzyme activity to be ready to decompose increased rhizodeposition, as supported by the higher potential activitiy (V<sub>max</sub>) and lower affinity to substrates (higher K<sub>m</sub>) of enzymes hydrolyzing cellobiose and proteins cleavage in warmed soil. In other words, stronger warming magnitude (+3.2 °C) changed microbial communities, and was sufficient to benefit fast-growing microbial populations with enzyme functions that specific to degrade labile SOM. Combining with 48 literature observations, we confirmed that the slight magnitude of temperature increase (< 2 °C) only altered microbial properties, but further temperature increases (2-4 °C) was sufficient to change almost all soil, microbial, and enzyme properties and related processes. As a consequence, the revealed microbial regulatory mechanism of stability of soil C storage is strongly depended on the magnitude of future climate warming.</p>

Soil aggregate stability and soil organic matter fractions under agropastoral systems established in native savanna

Soil Research ◽  
1996 ◽  
Vol 34 (6) ◽  
pp. 891 ◽  
Author(s):  
AJ Gijsman
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Disturbance ◽  
N Content ◽  
Soil C ◽  
Size Classes ◽  
Soil C And N ◽  
C And N

An area of native savanna on an Oxisol in the Eastern Plains of Colombia was opened and sown to various rotations of grass or grass-legume pasture with rice. After 4.5 years, the soil was sampled for studying the effect of land conversion on soil aggregation and on the distribution of total and particulate soil organic matter across the aggregate size classes. The size distribution of undisturbed aggregates did not vary among treatments. Five different methods were used to measure wet aggregate stability (WAS). The choice of method affected the WAS average across treatments as well as the differences among treatments. The only consistent observation was the lower WAS under monocropped rice compared with the other treatments. Inclusion of a legume in a pasture hardly affected aggregate stability. In contrast to the WAS measurements, which were carried out with soil aggregates of 1-2 mm, wet sieving of whole-soil samples revealed additional differences among treatments: large macroaggregates (>2 mm) proved less stable under those treatments that involved soil disturbance through ploughing and harvesting. Total soil C and N content did not vary among treatments, despite considerable differences in plant production levels. The C concentration, but not the N concentration, declined with decreasing aggregate size. The distribution of whole-soil C and N content across aggregate size classes depended more on the amount of soil in a certain size class than on the size class's C or N concentration. Those treatments that involved frequent soil disturbance had a smaller fraction of large macroaggregates (>2 mm) and, as a consequence, less C and N in the large macroaggregate fraction. The particulate organic matter (POM) fraction accounted for only 6.2-8.5% of total soil carbon. The small size of this pool makes it unlikely that POM can serve in these Oxisols for estimating the amount of soil organic matter with medium turnover rate, as suggested by others.

scholarly journals Using Diffuse Reflectance Spectroscopy as a High Throughput Method for Quantifying Soil C and N and Their Distribution in Particulate and Mineral-Associated Organic Matter Fractions

2021 ◽  
Vol 9 ◽  
Author(s):  
Paulina B. Ramírez ◽  
Francisco J. Calderón ◽  
Michelle Haddix ◽  
Emanuele Lugato ◽  
M. Francesca Cotrufo
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
High Throughput ◽  
Diffuse Reflectance ◽  
N Content ◽  
Soil C ◽  
Mir Spectroscopy ◽  
C Pools ◽  
Soil C And N ◽  
C And N

Large-scale quantification of soil organic carbon (C) and nitrogen (N) stocks and their distribution between particulate (POM) and mineral-associated (MAOM) organic matter is deemed necessary to develop land management strategies to mitigate climate change and sustain food production. To this end, diffuse reflectance mid-infrared spectroscopy (MIR) coupled with partial least square (PLS) analysis has been proposed as a promising method because of its low labor and cost, high throughput and the potential to estimate multiple soil attributes. In this paper, we applied MIR spectroscopy to predict C and N content in bulk soils, and in POM and MAOM, as well as soil properties influencing soil C storage. A heterogeneous dataset including 349 topsoil samples were collected under different soil types, land use and climate conditions across the European Union and the United Kingdom. The samples were analyzed for various soil properties to determine the feasibility of developing MIR-based predictive calibrations. We obtained accurate predictions for total soil C and N content, MAOM C and N content, pH, clay, and sand (R2> 0.7; RPD>1.8). In contrast, POM C and N content were predicted with lower accuracies due to non-linear dependencies, suggesting the need for additional calibration across similar soils. Furthermore, the information provided by MIR spectroscopy was able to differentiate spectral bands and patterns across different C pools. The strength of the correlation between C pools, minerals, and C functional groups was land use-dependent, suggesting that the use of this approach for long-term soil C monitoring programs should use land-use specific calibrations.

Long-term effects of afforestation with Pinus radiata on soil carbon, nitrogen, and pH: a case study

Soil Research ◽  
2011 ◽  
Vol 49 (6) ◽  
pp. 494 ◽  
Author(s):  
R. L. Parfitt ◽  
D. J. Ross
Keyword(s):  
Pinus Radiata ◽  
Mineral Soil ◽  
Early Spring ◽  
Early Years ◽  
Long Term Effects ◽  
Soil C ◽  
Soil Microbial ◽  
Soil C And N ◽  
C And N ◽  
Microbial C

Planting of Pinus radiata D. Don in previously grazed pastures is a common land-use change in New Zealand. Although carbon (C) accumulates relatively rapidly in the trees, there have been no studies of the annual effect on soil C content during the early years of establishment. Here, we study soil properties under P. radiata and pasture each year over 11 years after P. radiata was planted into pasture that had been grazed by sheep. Under the growing trees, grass was gradually shaded out by the unpruned trees, and completely disappeared after 6 years; needle litterfall had then increased appreciably. By year 9, soil microbial C and nitrogen (N), and net N mineralisation, were significantly lower under pine than under pasture. Soil pH, sampled at 0–100 mm in early spring each year, decreased by ~0.3 units under pine and increased by ~0.3 units under pasture. Close to the pine stems, total C and N decreased significantly for 3 years, while ~100 kg N/ha accumulated in the trees. Soil C and N increased in subsequent years, when litterfall increased. Overall, the mineral soil under pine lost ~500 kg N/ha over 11 years, consistent with uptake by the trees. Leaching losses (estimated using lysimeters) in year 9 were 4.5 kg N/ha.year. These data indicate that ~6 Mg C/ha may have been lost from the mineral soil at this site. The difficulties associated with measuring losses of C are discussed.

scholarly journals Soil Microbial Responses to 28 Years of Nutrient Fertilization in a Subarctic Heath

Ecosystems ◽  
2019 ◽  
Vol 23 (5) ◽  
pp. 1107-1119 ◽  
Author(s):  
Lettice C. Hicks ◽  
Kathrin Rousk ◽  
Riikka Rinnan ◽  
Johannes Rousk
Keyword(s):  
Community Structure ◽  
Soil Microorganisms ◽  
N Availability ◽  
Soil C ◽  
Soil Microbial ◽  
C And N Mineralization ◽  
Microbial Responses ◽  
Soil C And N ◽  
C And N

AbstractArctic and subarctic soils are typically characterized by low nitrogen (N) availability, suggesting N-limitation of plants and soil microorganisms. Climate warming will stimulate the decomposition of organic matter, resulting in an increase in soil nutrient availability. However, it remains unclear how soil microorganisms in N-limited soils will respond, as the direct effect of inorganic N addition is often shown to inhibit microbial activity, while elevated N availability may have a positive effect on microorganisms indirectly, due to a stimulation of plant productivity. Here we used soils from a long-term fertilization experiment in the Subarctic (28 years at the time of sampling) to investigate the net effects of chronic N-fertilization (100 kg N ha−1 y−1, added together with 26 kg P and 90 kg K ha−1 y−1, as expected secondary limiting nutrients for plants) on microbial growth, soil C and N mineralization, microbial biomass, and community structure. Despite high levels of long-term fertilization, which significantly increased primary production, we observed relatively minor effects on soil microbial activity. Bacterial growth exhibited the most pronounced response to long-term fertilization, with higher rates of growth in fertilized soils, whereas fungal growth remained unaffected. Rates of basal soil C and N mineralization were only marginally higher in fertilized soils, whereas fertilization had no significant effect on microbial biomass or microbial community structure. Overall, these findings suggest that microbial responses to long-term fertilization in these subarctic tundra soils were driven by an increased flow of labile plant-derived C due to stimulated plant productivity, rather than by direct fertilization effects on the microbial community or changes in soil physiochemistry.

scholarly journals Structural and Functional Organization of the Root System: A Comparative Study on Five Plant Species

Plants ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1338 ◽  
Author(s):  
Adriano Sofo ◽  
Hazem S. Elshafie ◽  
Ippolito Camele
Keyword(s):  
Plant Species ◽  
Functional Organization ◽  
Net Primary Production ◽  
Early Stage ◽  
Root Traits ◽  
Soil C ◽  
Soil Microbial ◽  
Soil C And N ◽  
C And N ◽  
C And N Cycling

Plants are affected by soil environments to the same extent that they affect soil functioning through interactions between environmental and genetic factors. Here, five plant species (broad bean, pea, cabbage, fennel, and olive) grown under controlled pot conditions were tested for their ability to differently stimulate the degradation of standard litter. Litter, soil C and N contents were measured for evaluating chemical changes due to plant presence, while soil microbial abundance was evaluated to assess if it had a positive or negative catalyzing influence on litter decomposition. The architecture and morphological traits of roots systems were also evaluated by using specific open-source software (SmartRoot). Soil chemical and microbiological characteristics were significantly influenced by the plant species. Variations in soil C/N dynamics were correlated with the diversity of root traits among species. Early stage decomposition of the standard litter changed on the basis of the plant species. The results indicated that key soil processes are governed by interactions between plant roots, soil C and N, and the microbial metabolism that stimulate decomposition reactions. This, in turn, can have marked effects on soil chemical and microbiological fertility, both fundamental for sustaining crops, and can promote the development of new approaches for optimizing soil C and N cycling, managing nutrient transport, and sustaining and improving net primary production.

scholarly journals Interactive effects of belowground organic matter input, increased precipitation and clipping on soil carbon and nitrogen mineralization in a temperate steppe

2013 ◽  
Vol 10 (6) ◽  
pp. 9493-9521
Author(s):  
L. N. Ma ◽  
C. Y. Guo ◽  
X. P. Xin ◽  
S. Yuan ◽  
R. Z. Wang
Keyword(s):  
Organic Matter ◽  
N Mineralization ◽  
Interactive Effects ◽  
Mineralization Rate ◽  
Temperate Steppe ◽  
Soil Microbial Community Structure ◽  
Soil C ◽  
C And N Mineralization ◽  
Soil C And N ◽  
C And N

Abstract. Soil organic matter (SOM) inputs, increased precipitation and clipping (reducing belowground photosynthates allocation) are predicted to affect soil C and N cycling in temperate grassland ecosystems. However, the interactive effects between SOM inputs (or increased precipitation) and clipping on soil C and N mineralization in temperate steppes are still poorly understood. A field manipulation experiment was conducted to quantify the effects of SOM inputs, increased precipitation, clipping and their interactions on soil C and N mineralization in a temperate steppe of northeastern China from 2010 to 2011. The results showed that SOM inputs significantly increased soil C mineralization rate (CMR) and net N mineralization rate (NMR). Increased precipitation-induced enhancement of soil CMR essentially ceased after the first year, stimulation of soil NMR and NNR continued into the second year. However, clipping only marginally decreased soil CMR and NMR during the two years. There were significant synergistic interactions between SOM inputs (or increased precipitation) and clipping on soil CMR and NMR, as SOM inputs (or increased precipitation) showed greater effects on soil CMR and NMR under clipped plots than under unclipped plots, which could be explained by the relative shifts in soil microbial community structure because of bacterial biomass increases, and by the relative decreases in arbuscular mycorrhizal fungi biomass due to the reduction of belowground photosynthates allocation. These results highlight the importance of plants in mediating the responses of soil C and N mineralization to potentially increased SOM and precipitation by controlling belowground photosynthates allocation in the temperate steppe. Thus, the findings have important implications for improving prediction of C and N sequestration potential and its feedbacks to climate change in temperate steppe ecosystems.

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