Pulse labelling of deep soil layers in forest with 13CH4: testing a new method for tracing methane in the upper horizons, understorey vegetation and tree stems using laser-based spectrometry

Abstract. Soil moisture in deep soil layers is a relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the variations in deep soil moisture and its influencing factors at a moderate watershed scale is important to ensure the sustainability of vegetation restoration efforts. In this study, we focus on analyzing the variations and factors that influence the deep soil moisture (DSM) in 80–500 cm soil layers based on a soil moisture survey of the Ansai watershed in Yan'an in Shanxi Province. Our results can be divided into four main findings. (1) At the watershed scale, higher variations in the DSM occurred at 120–140 and 480–500 cm in the vertical direction. At the comparable depths, the variation in the DSM under native vegetation was much lower than that in human-managed vegetation and introduced vegetation. (2) The DSM in native vegetation and human-managed vegetation was significantly higher than that in introduced vegetation, and different degrees of soil desiccation occurred under all the introduced vegetation types. Caragana korshinskii and black locust caused the most serious desiccation. (3) Taking the DSM conditions of native vegetation as a reference, the DSM in this watershed could be divided into three layers: (i) a rainfall transpiration layer (80–220 cm); (ii) a transition layer (220–400 cm); and (iii) a stable layer (400–500 cm). (4) The factors influencing DSM at the watershed scale varied with vegetation types. The main local controls of the DSM variations were the soil particle composition and mean annual rainfall; human agricultural management measures can alter the soil bulk density, which contributes to higher DSM in farmland and apple orchards. The plant growth conditions, planting density, and litter water holding capacity of introduced vegetation showed significant relationships with the DSM. The results of this study are of practical significance for vegetation restoration strategies, especially for the choice of vegetation types, planting zones, and proper human management measures.

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Soil contents and stoichiometry of carbon, nitrogen, and phosphorus in Finnish farmland and feedbacks on management patterns

10.5194/egusphere-egu21-12350 ◽

2021 ◽

Author(s):

Sichu Wang ◽

Oona Uhlgren ◽

Anna-Reetta Salonen ◽

Jussi Heinonsalo

Keyword(s):

Organic Matter ◽

Management Practice ◽

Combustion Method ◽

Agricultural Management ◽

Soil Columns ◽

Nitrogen And Phosphorus ◽

Deep Soil ◽

C:N:P Stoichiometry ◽

Soil Layers ◽

Soil C

<p>The coupled cycles and interactions of soil carbon (C), nitrogen (N), and phosphorus (P) are fundamental for soil quality and soil organic matter (SOM) formation. Low C:N ratios through nitrogenous fertilizer addition may accelerate SOM cycling and promote C mineralization in soil, whereas P limitations may decline C storage by reducing plant and microbial biomass production. Deeper soil layers&#8217; C-N-P stoichiometry has an important role in regulating SOM formation in subsoils. However, there is little information on soil C:N:P stoichiometry in deep soil layers of farmland. In this study, soil columns up to one meter were collected from 32 farms distributing across Finland with different soil texture and agricultural management history. The one-meter soil columns were cut into 10 cm deep slices and analyzed for the total organic carbon (TOC), total nitrogen (TN) by dry combustion method and total phosphorus (TP) contents by aqua regia digestion and ICP-OES method. Overall, the TOC, TN and TP contents all dropped sharply in 30-40 cm soil layers, but TP contents rose again in deep soil. The role of agricultural management practice (including crop rotation, crop cover, crop diversity and fertilization) on soil C:N:P stoichiometry as well as organic matter accumulation in the deep soil layers were explored. The preliminary results will be presented in the poster. The data deepens our understanding of soil C, N and P coupling and interaction related to soil C sequestration.</p>

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Characteristics of δD and δ18O of Reclaimed Mine Soil Water Profile and Its Source Water Bodies in a Coal Mining Subsidence Area with High Groundwater Level—A Case Study from the Longdong Coal Mining Subsidence Area in Jiangsu Province, China

Water ◽

10.3390/w12010274 ◽

2020 ◽

Vol 12 (1) ◽

pp. 274

Author(s):

Mengyu Ge ◽

Baozhang Chen

Keyword(s):

Soil Water ◽

Coal Mining ◽

Surface Waters ◽

Meteoric Water ◽

Mine Soil ◽

Deep Soil ◽

Soil Layers ◽

Subsidence Area ◽

Coal Mining Subsidence ◽

Δd And Δ18o

Coal mining, as one of the key drivers of land degradation worldwide, caused land subsidence problems. In this study, we conducted experimental research to explore the reclaimed mine soil (RMS) water dynamics and its sources in relation to reclaimed land use types using stable water isotopes in the Longdong coal mining area with high groundwater level in east China. We collected water samples seven times in 2017 from all of these water bodies (precipitation, surface waters (river water and water from subsidence pits (WSP)), groundwater and soil water). Our main findings are three fold: (1) the values of slope and intercept of the local meteoric water line of Craig (LMWL) of precipitation for the study area are higher than the global meteoric water line of Craig (GMWL) because of the humid monsoon climate zoon, and the values of δD and δ18O of surface waters and soil water and groundwater deviated from LMWL to some extent with a range of 5–30%, and the D and 18O of precipitation and the surface waters have higher seasonal variation than groundwater; (2) the values of δD and δ18O of RMS for the whole soil profile (0–100 cm) are lower than that of precipitation and have obvious seasonal variations and great fluctuation in the topsoil (0–30/40 cm) and decrease at depth (30/40–70 cm) and stable in deep soil layers (below 70 cm deep); (3) the RMS with forest and crop enhanced water infiltration capacity and soil water mixing strength compared with the waste RMS, so establishment of forest and crops should be encouraged in the RMS; (4) the main sources of topsoil (0–30 cm for crop and 0–40 cm for forest) of RMS are precipitation through infiltration, the main supply for deep soil water (below 70 cm deep) is groundwater, and the soil water for the middle deep soil layers (30/40–70 cm) is mainly from mixing sources of precipitation, groundwater, and river water through pant root water absorbing and groundwater upshifting.

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Two potato (Solanum tuberosum) varieties differ in drought tolerance due to differences in root growth at depth

Functional Plant Biology ◽

10.1071/fp14105 ◽

2014 ◽

Vol 41 (11) ◽

pp. 1107 ◽

Cited By ~ 19

Author(s):

Jaime Puértolas ◽

Carlos Ballester ◽

E. David Elphinstone ◽

Ian C. Dodd

Keyword(s):

Solanum Tuberosum ◽

Drought Tolerance ◽

Root Growth ◽

Water Deficit ◽

Solanum Tuberosum L ◽

Shoot Biomass ◽

Genotypic Differences ◽

Deep Soil ◽

Soil Layers ◽

Cultural Conditions

To test the hypothesis that root growth at depth is a key trait explaining some genotypic differences in drought tolerance in potato (Solanum tuberosum L.), two varieties (Horizon and Maris Piper) differing in drought tolerance were subjected to different irrigation regimes in pots in a glasshouse and in the field under a polytunnel. In the glasshouse, both cultivars showed similar gas exchange, leaf water potential, leaf xylem ABA concentration and shoot biomass independently of whether plants were grown under well watered or water deficit conditions. Under well watered conditions, root growth was three-fold higher in Horizon compared with Maris Piper, 3 weeks after emergence. Water deficit reduced this difference. In the polytunnel, applying 60% or less irrigation volume compared with full irrigation significantly decreased tuber yield in Maris Piper but not in Horizon. This was coincident with the higher root density of Horizon in deep soil layers (>40 cm), where water content was stable. The results suggest that early vigorous root proliferation may be a useful selection trait for maintaining yield of potato under restricted irrigation or rainfall, because it rapidly secures access to water stored in deep soil layers. Although selecting for vigorous root growth may assist phenotyping screening for drought tolerance, these varieties may require particular environmental or cultural conditions to express root vigour, such as sufficiently deep soils or sufficient water shortly after emergence.

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Deep Soil Layers of Drought-Exposed Forests Harbor Poorly Known Bacterial and Fungal Communities

Frontiers in Microbiology ◽

10.3389/fmicb.2021.674160 ◽

2021 ◽

Vol 12 ◽

Author(s):

Beat Frey ◽

Lorenz Walthert ◽

Carla Perez-Mon ◽

Beat Stierli ◽

Roger Köchli ◽

...

Keyword(s):

Community Structure ◽

Microbial Community ◽

Vertical Distribution ◽

Soil Depth ◽

Shannon Index ◽

Fungal Communities ◽

Soil Microbiome ◽

Deep Soil ◽

Soil Layers ◽

The Vertical Distribution

Soil microorganisms such as bacteria and fungi play important roles in the biogeochemical cycling of soil nutrients, because they act as decomposers or are mutualistic or antagonistic symbionts, thereby influencing plant growth and health. In the present study, we investigated the vertical distribution of the soil microbiome to a depth of 2 m in Swiss drought-exposed forests of European beech and oaks on calcareous bedrock. We aimed to disentangle the effects of soil depth, tree (beech, oak), and substrate (soil, roots) on microbial abundance, diversity, and community structure. With increasing soil depth, organic carbon, nitrogen, and clay content decreased significantly. Similarly, fine root biomass, microbial biomass (DNA content, fungal abundance), and microbial alpha-diversity decreased and were consequently significantly related to these physicochemical parameters. In contrast, bacterial abundance tended to increase with soil depth, and the bacteria to fungi ratio increased significantly with greater depth. Tree species was only significantly related to the fungal Shannon index but not to the bacterial Shannon index. Microbial community analyses revealed that bacterial and fungal communities varied significantly across the soil layers, more strongly for bacteria than for fungi. Both communities were also significantly affected by tree species and substrate. In deep soil layers, poorly known bacterial taxa from Nitrospirae, Chloroflexi, Rokubacteria, Gemmatimonadetes, Firmicutes and GAL 15 were overrepresented. Furthermore, archaeal phyla such as Thaumarchaeota and Euryarchaeota were more abundant in subsoils than topsoils. Fungal taxa that were predominantly found in deep soil layers belong to the ectomycorrhizal Boletus luridus and Hydnum vesterholtii. Both taxa are reported for the first time in such deep soil layers. Saprotrophic fungal taxa predominantly recorded in deep soil layers were unknown species of Xylaria. Finally, our results show that the microbial community structure found in fine roots was well represented in the bulk soil. Overall, we recorded poorly known bacterial and archaeal phyla, as well as ectomycorrhizal fungi that were not previously known to colonize deep soil layers. Our study contributes to an integrated perspective on the vertical distribution of the soil microbiome at a fine spatial scale in drought-exposed forests.

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Soil Layers Properties of a Profile Developed on the Past Depositional Series on Merbabu Volcano Central Java Indonesia

Journal of Tropical Soils ◽

10.5400/jts.2019.v24i2.53-63 ◽

2019 ◽

Vol 24 (2) ◽

pp. 53

Author(s):

Mohammad Nurcholis ◽

Susila Herlambang ◽

Sri Aminah Suwartikaningsih ◽

Dian Fiantis ◽

Dwi Fitri Yudiantoro

Keyword(s):

Soil Profile ◽

Soil Morphology ◽

Deep Soil ◽

Sand Fraction ◽

Soil Layers ◽

Central Java ◽

Development Processes ◽

Different Characteristics ◽

Physical And Chemical ◽

Black Color

A wide and deep soil profile (around 1200 cm) was observed at Ketep Park West Slope of Merbabu volcano Central Java, Indonesia to identify the soil morphology, physical and, chemical and mineralogical properties. Results showed that several soil development processes occurred in each volcanic deposits with different characteristics. Most soil layers met some of andic soil properties criteria such bulk density <0.9 g.cm-3, P retention of >85%, and (Alo + ½ Feo) >2.0%. A thin melanic material showing black color layer was found at the lower part of the soil profile, i.e. in depth from 726 to 798 cm. The dominant material in most soil layers is an allophane. Minerals in the sand fraction were dominated by labradorite and augite, with some layers were hypersthene and green hornblende.

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Comparative analysis of Piled Raft Foundation System (PRFS) settlements placed on soft soils via geotechnical centrifuge

Soils and Rocks ◽

10.28927/sr.2021.062321 ◽

2021 ◽

Vol 44 (2) ◽

pp. 1-12

Author(s):

Edgar Rodríguez Rincon ◽

Bernardo Caicedo Hormaza ◽

Juan Felix Rodríguez Rebolledo

Keyword(s):

Pore Pressure ◽

Soft Clay ◽

Clay Soils ◽

Deep Soil ◽

Consolidation Process ◽

Soil Layers ◽

Geotechnical Centrifuge ◽

Piled Raft ◽

Piled Raft Foundation ◽

Scale Models

The use of Piled Raft Foundations Systems (PRFS) has been extended to different types of soils, including soft clay soils. In this type of soil it is possible that, in addition to the consolidation process due to the presence of loads, a subsidence process is generated, associated with variations in pore pressure with depth. In many cases, these variations are associated with the loss of recharge of the aquifers or with the extraction of water from deep soil layers. In this work, the behaviour of some PRFS built on soft clay soils, which are subjected to the double consolidation process, are evaluated, both by loading and by the extraction of water from deep soil layers. The research is based on the implementation of reduced-scale models in a geotechnical centrifuge; the influence of the separation and number of piles on the deformation or settlement of the system is analysed. It is shown that, normally, groups of piles with greater separation control settlement more effectively. However, the settlements are greater when the soil is subjected to the weight of the structure in addition to a process of depletion of the pore pressure, because the settlement depends on the distribution of the piles, which is described using the Filling Factor (FF).

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Assimilation of surface soil moisture into a multilayer soil model: design and evaluation at local scale

Hydrology and Earth System Sciences ◽

10.5194/hess-18-673-2014 ◽

2014 ◽

Vol 18 (2) ◽

pp. 673-689 ◽

Cited By ~ 27

Author(s):

M. Parrens ◽

J.-F. Mahfouf ◽

A. L. Barbu ◽

J.-C. Calvet

Keyword(s):

Soil Moisture ◽

Land Surface ◽

Surface Soil ◽

Soil Column ◽

Cumulative Distribution ◽

Surface Soil Moisture ◽

Deep Soil ◽

Background Error ◽

Soil Layers ◽

Diffusion Scheme

Abstract. Land surface models (LSM) have improved considerably in the last two decades. In this study, the Interactions between Surface, Biosphere, and Atmosphere (ISBA) LSM soil diffusion scheme is used (with 11 soil layers represented). A simplified extended Kalman filter (SEKF) allows ground observations of surface soil moisture (SSM) to be assimilated in the multilayer LSM in order to constrain deep soil moisture. In parallel, the same simulations are performed using the ISBA LSM with 2 soil layers (a thin surface layer and a bulk reservoir). Simulations are performed over a 3 yr period (2003–2005) for a bare soil field in southwestern France, at the SMOSREX (Surface Monitoring Of the Soil Reservoir Experiment) site. Analyzed soil moisture values correlate better with soil moisture observations when the ISBA LSM soil diffusion scheme is used. The Kalman gain is greater from the surface to 45 cm than below this limit. For dry periods, corrections introduced by the assimilation scheme mainly affect the first 15 cm of soil whereas weaker corrections impact the total soil column for wet periods. Such seasonal corrections cannot be described by the two-layer ISBA LSM. Sensitivity studies performed with the multilayer LSM show improved results when SSM (0–6 cm) is assimilated into the second layer (1–5 cm) than into the first layer (0–1 cm). The introduction of vertical correlations in the background error covariance matrix is also encouraging. Using a yearly cumulative distribution function (CDF)-matching scheme for bias correction instead of matching over the three years permits the seasonal variability of the soil moisture content to be better transcribed. An assimilation experiment has also been performed by forcing ISBA-DF (diffusion scheme) with a local forcing, setting precipitation to zero. This experiment shows the benefit of the SSM assimilation for correcting inaccurate atmospheric forcing.

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