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1
Sawada, Y., LAG Aylmore et JM Hainsworth. « Development of a soil water dispersion index (SOWADIN) for testing the effectiveness of soil-wetting agents ». Soil Research 27, no 1 (1989) : 17. http://dx.doi.org/10.1071/sr9890017.
Texte intégralRésumé :
Computer-assisted tomography (CAT) applied to gamma-ray attenuation measurements has been used to develop an index termed the soil water dispersion index (SOWADIN), which describes quantitatively the amount and distribution of water in soil columns. The index, which is determined by classifying pixels in a scanned slice into three categories according to their attenuation coefficients, contains two numerical values. The first value corresponds to the water content of the scanned slice and the second value is a measure of the dispersion of the water throughout the slice. Artificially wetted zones were created in soil columns to give one-third of the scanned layer wetted with various patterns of wetted-area distribution. The SOWADIN values obtained accurately reflected the differences in water distribution associated with the different patterns. Application of SOWADIN to columns of a water-repellent sand before and after treatment with a soil-wetting agent clearly illustrates both the increase in water content and improvement in water distribution in the soil column following treatment.
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Halihan, Todd, John Paul Hager, Lucie Guertault et Garey A. Fox. « Detecting Macropore Fingering Using Temporal Electrical Resistivity Imaging ». Applied Engineering in Agriculture 37, no 5 (2021) : 861–70. http://dx.doi.org/10.13031/aea.14294.
Texte intégralRésumé :
HighlightsSingle macropores can be detected using temporal electrical resistivity imaging under controlled conditions.Macropore flow can be detected based on preferentially wetted fingers of increased conductance.Macropore activation does not appear to require saturated surface conditions to induce preferential flow.Abstract. Riparian soils are uniquely susceptible to the formation of macropores, which are hypothesized to promote fast transport of water and contaminants through upper soil layers. Electrical Resistivity Imaging (ERI) can locate spatial heterogeneities in soil wetting patterns and evaluate differences due to vegetation, thus optimizing the design of riparian buffers. Temporal ERI (TERI) imaging was conducted in a fine and coarse field setting with artificial macropores to evaluate flow under unsaturated simulated rainfall conditions and saturated infiltrometer conditions. While single macropores are detectable using TERI datasets, the results in an average field setting would detect the wetted area surrounding a macropore, not the macropore itself. The results were similar for both the primary fine grain soil site in Oklahoma as well as the coarse grain site in North Carolina. TERI data indicated that without artificial conditions with low noise conditions, a single macropore would not be detected, a wetted zone would be the best detection. In ordinary field evaluation of natural macropores, the TERI technique would detect the wetted zone around a macropore similar to a high hydraulic conductivity zone in a heterogeneous soil matrix. Finally, the results confirmed that macropore activation does not require saturated conditions to generate preferential flow. Keywords: Hydrogeophysics, Preferential flowpaths, Riparian buffers, Temporal electrical resistivity imaging.
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Sokołowska, Zofia, Katarzyna Szewczuk-Karpisz, Marcin Turski, Agnieszka Tomczyk, Marta Cybulak et Kamil Skic. « Effect of Wood Waste and Sunflower Husk Biochar on Tensile Strength and Porosity of Dystric Cambisol Artificial Aggregates ». Agronomy 10, no 2 (6 février 2020) : 244. http://dx.doi.org/10.3390/agronomy10020244.
Texte intégralRésumé :
This paper focuses on the tensile strength (Q) and porosity of Dystric Cambisol cylinders with and without biochars (0.1% or 5% dose) obtained from wood waste (BC1) and sunflower husks (BC2). The experiments were performed on air-dried and wetted artificial aggregates remolded from unfractionated soil and its selected fractions (1–0.25, 0.25–0.1, 0.1–0.05, and <0.05 mm). The obtained results indicated that the biochar addition reduced the tensile strength of all examined samples, regardless of the type of biomass used in pyrolysis. This effect was more significant with the larger biochar dose of 5%. When cylinders formed from a wetted 1–0.25 mm fraction with 5% BC2, the Q reduction equaled as much as 0.048 MPa. The noted decrease in tensile strength was mainly associated with the formation of macropores in the cylinders (of maximum radii: 4.77 µm BC1 and 5.78 μm BC2). The highest tensile strength was observed in the air-dried samples formed from the largest silica-rich fraction (1–0.25 mm) without biochar (0.078 MPa for the air-dried cylinders and 0.066 MPa for the wetted ones). The higher Q parameter for the air-dried remolded soil aggregates was probably related to the dehydration of soil gels and the thermal transformation of iron and alumina oxides during drying.
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Menzies, NW, et LC Bell. « Evaluation of the influence of sample preparation and extraction technique on soil solution composition ». Soil Research 26, no 3 (1988) : 451. http://dx.doi.org/10.1071/sr9880451.
Texte intégralRésumé :
Soil solutions were extracted by immiscible liquid displacement with trichlorotrifluoroethane and by centrifuge drainage from surface and subsoil samples having a wide range of chemical and physical properties. Extractions were performed on field-moist samples and on air-dry samples which were re-wetted to different matric suctions and for different lengths of time. The composition of the soil solution obtained was the same with both methods of extraction when samples had been pre-wet to a matric suction of 0-1 bar. Immiscible liquid displacement extracted solution from a krasnozem surface soil at suctions as great as 15 bar; in contrast, centrifuge drainage failed to extract solution from this soil at >3 bar. The concentration of ions in solutions extracted by displacement from soils with increasing matric suction rose to a far greater extent than that anticipated if concentration was the only mechanism operating. In re-wet air-dry samples, major cations and anions were at equilibrium levels in solution after incubation for 1 day; longer incubation times resulted in an artificial elevation of ionic strength through mineralization of organic matter in some surface samples. The levels achieved after 1 day were similar to those present in solutions extracted from field-moist samples.
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Ahmed, Mutez A., Eva Kroener, Maire Holz, Mohsen Zarebanadkouki et Andrea Carminati. « Mucilage exudation facilitates root water uptake in dry soils ». Functional Plant Biology 41, no 11 (2014) : 1129. http://dx.doi.org/10.1071/fp13330.
Texte intégralRésumé :
As plant roots take up water and the soil dries, water depletion is expected to occur in the rhizosphere. However, recent experiments showed that the rhizosphere was wetter than the bulk soil during root water uptake. We hypothesise that the increased water content in the rhizosphere was caused by mucilage exuded by roots. It is probably that the higher water content in the rhizosphere results in higher hydraulic conductivity of the root–soil interface. In this case, mucilage exudation would favour the uptake of water in dry soils. To test this hypothesis, we covered a suction cup, referred to as an artificial root, with mucilage. We placed it in soil with a water content of 0.03 cm3 cm–3, and used the root pressure probe technique to measure the hydraulic conductivity of the root–soil continuum. The results were compared with measurements with roots not covered with mucilage. The root pressure relaxation curves were fitted with a model of root water uptake including rhizosphere dynamics. The results demonstrated that when mucilage is added to the root surface, it keeps the soil near the roots wet and hydraulically well conductive, facilitating the water flow from dry soils towards the root surface. Mucilage exudation seems to be an optimal plant trait that favours the capture of water when water is scarce.
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Stewart, D. J., C. M. Taylor, C. E. Reeves et J. B. McQuaid. « Biogenic nitrogen oxide emissions from soils : impact on NO<sub>x</sub> ; and ozone over west Africa during AMMA (African Monsoon Multidisciplinary Analysis) : observational study ». Atmospheric Chemistry and Physics 8, no 8 (29 avril 2008) : 2285–97. http://dx.doi.org/10.5194/acp-8-2285-2008.
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Abstract. Chemical and meteorological parameters measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the African Monsoon Multidisciplinary Analysis (AMMA) campaign are presented to show the impact of NOx emissions from recently wetted soils in West Africa. NO emissions from soils have been previously observed in many geographical areas with different types of soil/vegetation cover during small scale studies and have been inferred at large scales from satellite measurements of NOx. This study is the first dedicated to showing the emissions of NOx at an intermediate scale between local surface sites and continental satellite measurements. The measurements reveal pronounced mesoscale variations in NOx concentrations closely linked to spatial patterns of antecedent rainfall. Fluxes required to maintain the NOx concentrations observed by the BAe-146 in a number of cases studies and for a range of assumed OH concentrations (1×106 to 1×107 molecules cm−3) are calculated to be in the range 8.4 to 36.1 ng N m−2 s−1. These values are comparable to the range of fluxes from 0.5 to 28 ng N m−2 s−1 reported from small scale field studies in a variety of non-nutrient rich tropical and sub-tropical locations reported in the review of Davidson and Kingerlee (1997). The fluxes calculated in the present study have been scaled up to cover the area of the Sahel bounded by 10 to 20 N and 10 E to 20 W giving an estimated emission of 0.03 to 0.30 Tg N from this area for July and August 2006. The observed chemical data also suggest that the NOx emitted from soils is taking part in ozone formation as ozone concentrations exhibit similar fine scale structure to the NOx, with enhancements over the wet soils. Such variability can not be explained on the basis of transport from other areas. Delon et al. (2008) is a companion paper to this one which models the impact of soil NOx emissions on the NOx and ozone concentration over West Africa during AMMA. It employs an artificial neural network to define the emissions of NOx from soils, integrated into a coupled chemistry-dynamics model. The results are compared to the observed data presented in this paper. Here we compare fluxes deduced from the observed data with the model-derived values from Delon et al. (2008).
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Lastiri-Hernández, Marcos Alfonso, Dioselina Álvarez-Bernal, Gustavo Cruz-Cárdenas, J. Teodoro Silva-García, Eloy Conde-Barajas et Ernesto Oregel-Zamudio. « Potential of Epipremnum aureum and Bacopa monnieri (L.) Wettst for Saline Phytoremediation in Artificial Wetlands ». Water 15, no 1 (2 janvier 2023) : 194. http://dx.doi.org/10.3390/w15010194.
Texte intégralRésumé :
The aim of this research was to evaluate the phytoremediative potential of Epipremnum aureum and Bacopa monnieri to improve the chemical properties of irrigation water exposed to the following two saline concentrations: highly saline (EC 2000 μS cm−1) and severely saline (EC 4000 μS cm−1). The artificial wetlands used in this experiment were of the free water surface type, considering a hydraulic retention time of 42 days. The evaluated treatments were configured as follows: T1 (B. monnieri [control, 300 μS cm−1]), T2 (B. monnieri [2000 μS cm−1]), T3 (B. monnieri [4000 μS cm−1]), T4 (E. aureum [control, 300 μS cm−1]), T5 (E. aureum [2000 μS cm−1]), T6 (E. aureum [4000 μS cm−1]), T7 (B. monnieri + E. aureum [control, 300 μS cm−1]), T8 (B. monnieri + E. aureum [2000 μS cm−1]), and T9 (B. monnieri + E. aureum [4000 μS cm−1]). The results showed that the species B. monnieri and E. aureum (both separately and together) showed a good ability to reduce the salinity of the irrigation water. However, B. monnieri showed a greater ability of phytoremediation, to the point of improving its chemical properties and reducing potential damage to the soil to use this water. In the highly saline group, B. monnieri accumulated 7.992 g per experimental unit and achieved to reduce of the pH from 7.96 to 7.75, EC from 2000 μS cm−1 to 670 μS cm−1, SAR from 13.54 to 3.91 and ESP from 20.17 to 5.83, which allowed it to go from (C3-S3) to (C3-S1). In the severely saline group, B. monnieri accumulated 13.494 g per experimental unit and achieved to reduce the pH from 8.14 to 7.91, EC from 4000 μS cm−1 to 1730 μS cm−1, SAR from 27.35 to 8.73, ESP from 40.35 to 13.01, which allowed it to go from (C4-S4) to (C3-S2).
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Tiemeyer, B., et P. Kahle. « Nitrogen and dissolved organic carbon (DOC) losses from an artificially drained grassland on organic soils ». Biogeosciences Discussions 11, no 2 (25 février 2014) : 3023–64. http://dx.doi.org/10.5194/bgd-11-3023-2014.
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Abstract. Nitrate-nitrogen (NO3-N) as well as dissolved organic carbon (DOC) and nitrogen (DON) concentrations and losses were studied for three respectively two years in a small catchment dominated by a degraded peatland used as intensive grassland. Concentrations in the shallow groundwater were spatially and temporally very variable with NO3-N being the most dynamic component (7.3 ± 12.5 mg L–1). Average NO3-N concentrations of 10.3 ± 5.4 mg L–1 in the ditch draining the catchment and annual NO3-N losses of 19, 35 and 26 kg ha–1 confirmed drained peatlands as an important source of diffuse N pollution. The highest NO3-N losses occurred during the wettest year. Resulting from concentrations of 2.4 ± 0.8 mg L–1, DON added further 4.5 to 6.4 kg ha–1 to the N losses and thus formed a relevant component of the total N losses. Ditch DOC concentrations of 24.9 ± 5.9 mg L–1 resulted in DOC losses of 66 kg ha–1 in the wet year 2006/07 and 39 kg ha–1 in the dry year 2007/08. Both DOC and N concentrations were governed by hydrological conditions, but NO3-N reacted much faster and clearer on rising discharge rates than DOC which tended to be higher under dryer conditions. In the third year of the study, the superposition of a very wet summer and land use changes from grassland to arable land in a part of the catchment suggests that under re-wetting conditions with a high groundwater table in summer, NO3-N would diminish quickly, while DOC would remain on a similar level. Further intensification of the land use, on the other hand, would increase N losses to receiving water bodies.
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Tiemeyer, B., et P. Kahle. « Nitrogen and dissolved organic carbon (DOC) losses from an artificially drained grassland on organic soils ». Biogeosciences 11, no 15 (6 août 2014) : 4123–37. http://dx.doi.org/10.5194/bg-11-4123-2014.
Texte intégralRésumé :
Abstract. Nitrate–nitrogen (NO3–N) as well as dissolved organic carbon (DOC) and nitrogen (DON) concentrations and losses were studied for three and two years, respectively, in a small catchment dominated by a degraded peatland used as intensive grassland. Concentrations in the shallow groundwater were spatially and temporally very variable, with NO3–N being the most dynamic component (7.3 ± 12.5 mg L−1) and ranging from 0 to 79.4 mg L−1. Average NO3–N concentrations of 10.3 ± 5.4 mg L−1 (0 to 25.5 mg L−1) in the ditch draining the catchment and annual NO3–N losses of 19, 35 and 26 kg ha−1 confirmed drained peatlands as an important source of diffuse N pollution. The highest NO3–N losses occurred during the wettest year. Resulting from concentration of 2.4 ± 0.8 mg L−1 (0.7 to 6.2 mg L−1), DON added a further 4.5 to 6.4 kg ha−1 to the N losses and thus formed a relevant (15%) component of the total N losses. Ditch DOC concentrations of 24.9 ± 5.9 mg L−1 (13.1 to 47.7 mg L−1) resulted in DOC losses of 66 kg ha−1 in the wet year of 2006/2007 and 39 kg ha−1 in the dry year of 2007/2008. Ditch DOC concentration were lower than the groundwater DOC concentration of 50.6 ± 15.2 mg L−1 (14.9 to 88.5 mg L−1). Both DOC and N concentrations were governed by hydrological conditions, but NO3–N reacted much faster and clearer on rising discharge rates than DOC, which tended to be higher under drier conditions. In the third year of the study, the superposition of a very wet summer and land use changes from grassland to arable land in a part of the catchment suggests that, under re-wetting conditions with a high groundwater table in summer, NO3–N would diminish quickly, while DOC would remain on a similar level. Further intensification of the land use, on the other hand, would increase N losses to receiving water bodies.
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Welsh, Molly K., Sara K. McMillan et Philippe G. Vidon. « Impact of Riparian and Stream Restoration on Denitrification in Geomorphic Features of Agricultural Streams ». Transactions of the ASABE 63, no 5 (2020) : 1157–67. http://dx.doi.org/10.13031/trans.13777.
Texte intégralRésumé :
HighlightsDenitrification enzyme activity (DEA) was measured in stream sediments of restored and unrestored agricultural streams.Nitrate, sediment characteristics, riparian vegetation, and geomorphology influenced DEA.Pools at restored sites had lower organic carbon, coarser sediment textures, and lower denitrification potential.Restoration strategies should increase organic carbon and residence times through complex flowpaths.Abstract. Agricultural land use, channel modifications, and riparian vegetation composition can affect instream denitrification by altering geomorphic features, such as sediment texture, organic matter, retention time, and hyporheic exchange. Stream and riparian restoration is widely implemented in agricultural watersheds to mitigate excess nutrient export to sensitive downstream waters; however, the cumulative impact of channel reconstruction and altered channel and near-stream morphology on nitrogen dynamics remains poorly understood. We measured denitrification enzyme activity (DEA) and environmental variables (e.g., water chemistry, sediment texture, and organic matter) in different geomorphic features in agriculturally influenced streams in North Carolina with varied channel and riparian zone characteristics. Our results indicate that denitrification is primarily influenced by increased transport of nitrate (NO3-) to the streams in wetter months. Secondarily, structural factors, including riparian vegetation and stream geomorphology, impact denitrification by controlling the distribution of sediment texture and organic carbon. In the newly restored stream, we observed coarser streambed sediments and low sediment organic carbon, especially in scour pools constructed downstream from cross-vanes. Lower DEA was observed in restored pools (39.1 ng N g-1 dry mass h-1) compared to naturally occurring pools (70.7 to 278.1 ng N g-1 dry mass h-1). These results highlight the need for restoration strategies to be directed at increasing organic carbon and residence times through complex flowpaths (e.g., meanders, root wads, artificial woody debris dams). Keywords: Denitrification, Freshwater, Nitrogen, Restoration, Riparian, Stream, Water quality.
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Burnett, Michael W., Gregory R. Quetin et Alexandra G. Konings. « Data-driven estimates of evapotranspiration and its controls in the Congo Basin ». Hydrology and Earth System Sciences 24, no 8 (27 août 2020) : 4189–211. http://dx.doi.org/10.5194/hess-24-4189-2020.
Texte intégralRésumé :
Abstract. Evapotranspiration (ET) from tropical forests serves as a critical moisture source for regional and global climate cycles. However, the magnitude, seasonality, and interannual variability of ET in the Congo Basin remain poorly constrained due to a scarcity of direct observations, despite the Congo being the second-largest river basin in the world and containing a vast region of tropical forest. In this study, we applied a water balance model to an array of remotely sensed and in situ datasets to produce monthly, basin-wide ET estimates spanning April 2002 to November 2016. Data sources include water storage changes estimated from the Gravity Recovery and Climate Experiment (GRACE) satellites, in situ measurements of river discharge, and precipitation from several remotely sensed and gauge-based sources. An optimal precipitation dataset was determined as a weighted average of interpolated data by Nicholson et al. (2018), Climate Hazards InfraRed Precipitation with Station data version 2 (CHIRPS2) , and the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks–Climate Data Record product (PERSIANN-CDR), with the relative weights based on the error magnitudes of each dataset as determined by triple collocation. The resulting water-balance-derived ET (ETwb) features a long-term average that is consistent with previous studies (117.2±3.5 cm yr−1) but displays greater seasonal and interannual variability than seven global ET products. The seasonal cycle of ETwb generally tracks that of precipitation over the basin, with the exception that ETwb is greater in March–April–May (MAM) than in the relatively wetter September–October–November (SON) periods. This pattern appears to be driven by seasonal variations in the diffuse photosynthetically active radiation (PAR) fraction, net radiation (Rn), and soil water availability. From 2002 to 2016, Rn, PAR, and vapor-pressure deficit (VPD) all increased significantly within the Congo Basin; however, no corresponding trend occurred in ETwb. We hypothesize that the stability of ETwb over the study period despite sunnier and less humid conditions may be due to increasing atmospheric CO2 concentrations that offset the impacts of rising VPD and irradiance on stomatal water use efficiency (WUE).
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Ozerova, S. D. « Vegetation map of the “Lindulovskaya Roshcha” nature reserve ». Geobotanical mapping, no 2021 (2021) : 84–96. http://dx.doi.org/10.31111/geobotmap/2021.84.
Texte intégralRésumé :
The article presents the vegetation map of the “Lindulovskaya Roshcha” Nature Reserve (Fig. 1, 2), which is located in the Vyborg district, Leningrad Region (Karelian Isthmus). The reserve was organized in 1976 to protect the Lindulovskaya larch ship grove with the world’s oldest tree plantings. The idea of planting larch in the suburbs of St. Petersburg, necessary for the needs of shipbuilding, belonged to Peter the Great. However, it was possible to implement this project only in 1738, when the first planting of Siberian larch seeds collected in the Arkhangelsk region was carried out on agricultural land near the Lindulovka River (Roshchinka River at the present). There are 5 stages of larch planting in the reserve (Table 1). The age of the oldest plantings is 280 years, the youngest — about 40 years (see Fig. 4). Currently larch plantations occupy about 50 hectares. In addition to larch (Larix sibirica, L. dahurica, L. decidua) other tree species were planted in the 1920s: Pinus murrayana, Thuja plicata, Quercus robur, Ulmus glabra. In 1990 the “Lindulovskaya Roshcha” was included in the list of cultural heritage sites of UNESCO (“The historical centre of St. Petersburg and associated complexes of monuments”), as a place of growth of the oldest artificial plantations of larch in Russia and Europe. In order to study the patterns of distribution of plant communities, a vegetation map of the reserve was compiled for the first time on a scale of 1 : 50 000. 23 types of plant communities have been identified, of which 12 were natural and 11 were introduced (Fig. 3). The areal analysis showed that spruce forests occupy the largest areas (76 %), pine forests – 12 %, birch forests – 5 %; larch plantings account for 5 % of the territory (Table 2). Studies have shown that the species diversity of larch forests is much higher than in spruce stands, growing in similar conditions. The species composition of vascular plants of larch forests includes about 25–30 species, and in spruce forests – less than 10 species. It can be explained by the smaller closeness of larch stands compared to spruce ones and richer soils with a fairly powerful humus horizon. The vital condition of larch stands varies in plantings. On the one hand, this is due to the difference in the places of growth: in wetter habitats (on floodplain terraces) larch grows worse than on drained plains or valley slopes. On the other hand, the condition of larch stands is influenced by historical events and various planting methods. The deterioration of the condition of the larch was caused by military actions during the Second World War, when a large number of trees on the slopes of Roshchinka River valley were damaged and destroyed. In the post-war years, small areas were planted surrounded by spruce forests, which led to the fact that larch grew in less favourable conditions (competition from spruce increased) than earlier plantings on agricultural land or large cuttings.
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Gutierrez, Moises M., Micah V. Cameron-Harp, Partha P. Chakraborty, Emily M. Stallbaumer-Cyr, Jordan A. Morrow, Ryan R. Hansen et Melanie M. Derby. « Investigating a microbial approach to water conservation : Effects of Bacillus subtilis and Surfactin on evaporation dynamics in loam and sandy loam soils ». Frontiers in Sustainable Food Systems 6 (17 octobre 2022). http://dx.doi.org/10.3389/fsufs.2022.959591.
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Semi-arid regions faced with increasingly scarce freshwater resources must manage competing demands in the food-energy-water nexus. A possible solution modifies soil hydrologic properties using biosurfactants to reduce evaporation and improve water retention. In this study, two different soil textures representative of agricultural soils in Kansas were treated with a direct application of the biosurfactant, Surfactin, and an indirect application via inoculation of Bacillus subtilis. Evaporation rates of the wetted soils were measured when exposed to artificial sunlight (1000 W/m2) and compared to non-treated control soils. Experimental results indicate that both treatments alter soil moisture dynamics by increasing evaporation rates by when soil moisture is plentiful (i.e., constant rate period) and decreasing evaporation rates by when moisture is scarce (i.e., slower rate period). Furthermore, both treatments significantly reduced the soil moisture content at which the soil transitioned from constant rate to slower rate evaporation. Out of the two treatments, inoculation with B. subtilis generally produced greater changes in evaporation dynamics; for example, the treatment with B. subtilis in sandy loam soils increased constant rate periods of evaporation by 43% and decreased slower rate evaporation by 49%. In comparing the two soil textures, the sandy loam soil exhibited a larger treatment effect than the loam soil. To evaluate the potential significance of the treatment effects, a System Dynamics Model operationalized the evaporation rate results and simulated soil moisture dynamics under typical daily precipitation conditions. The results from this model indicate both treatment methods significantly altered soil moisture dynamics in the sandy loam soils and increased the probability of the soil exhibiting constant rate evaporation relative to the control soils. Overall, these findings suggest that the decrease in soil moisture threshold observed in the experimental setting could increase soil moisture availability by prolonging the constant rate stage of evaporation. As inoculation with B. subtilis in the sandy loam soil had the most pronounced effects in both the experimental and simulated contexts, future work should focus on testing this treatment in field trials with similar soil textures.
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He, Xiao-hui, Jian-hua Si, Li Zhu, Dong-meng Zhou, Chun-yan Zhao, Bing Jia, Chun-lin Wang, Jie Qin et Xing-lin Zhu. « Modeling habitat suitability of Hippophae rhamnoides L. using MaxEnt under climate change in China : A case study of H. r. sinensis and H. r. turkestanica ». Frontiers in Forests and Global Change 5 (11 janvier 2023). http://dx.doi.org/10.3389/ffgc.2022.1095784.
Texte intégralRésumé :
Hippophae rhamnoides is widely known for its important ecological, economic, and social benefits. It is known as the pioneer plant of soil and water conservation, with homology in food and medicine. With the climate warming in recent years, the numbers of this species and countries with this plant have decreased steadily. H. r. sinensis and H. r. turkestanica have the widest distribution area in China, which account for more than 90% of the total national Hippophae rhamnoides resources. We firstly screened the presence data and downscale the environment variables (climate and soil) by correlation analysis. Secondly, based on the 232 occurrence data of H. r. sinensis and 10 environmental variables, the 73 occurrence data of H. r. turkestanica and 11 environmental variables, we simulated and predicted their suitable habitats in China, both at the current time and in the 2050S (2041–2060), and analyzed the dominant factors effecting its distribution by using MaxEnt. Finally, we studied the habitat variations and centroid migrations of these subspecies under future climate scenarios using the spatial analysis function of ArcGIS. The results indicated that the area of suitable habitat for H. r. sinensis is much larger than that of H. r. trkestanica in China. The suitable habitat of H. r. sinensis is concentrated in the middle and upper reaches of the Yellow River, mainly distributed in Shaanxi, Shanxi, Sichuan, Qinghai, Gansu, Ningxia, Tibet, and Inner Mongolia, and that of H. r. trkestanica is mainly distributed in Xinjiang and Tibet. The former is mainly affected by bio13 (precipitation of the wettest month), bio11 (mean temperature of the coldest quarte) and bio3 (Isothermality), and the latter is mainly affected by bio13 (precipitation of the wettest month), bio2 (mean diurnal range) and bio15 (precipitation seasonality), and the former is also more stable in the face of future climate change. They are more susceptible to climate than soil in their survival. Although, the two subspecies tend to expand and migrate toward lower latitude under future climate scenarios, there are some differences. H. r. sinensis will migrate westward, while H. r. trkestanica will migrate eastward as a whole. They have a high stability of suitable habitat and are not at risk of extinction in the future. The study’s findings help to clarify the resource reserve of Hippophae rhamnoides L. in China, which will help to guide the protection of wild resources and to popularize artificial planting in suitable areas, and provides scientific basis for the protection of ecological environment.
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Mathur, Manish, Preet Mathur et Harshit Purohit. « Ecological niche modelling of a critically endangered species Commiphora wightii (Arn.) Bhandari using bioclimatic and non-bioclimatic variables ». Ecological Processes 12, no 1 (27 février 2023). http://dx.doi.org/10.1186/s13717-023-00423-2.
Texte intégralRésumé :
Abstract Background The aim of this study is to examine the effects of four different bioclimatic predictors (current, 2050, 2070, and 2090 under Shared Socioeconomic Pathways SSP2-4.5) and non-bioclimatic variables (soil, habitat heterogeneity index, land use, slope, and aspect) on the habitat suitability and niche dimensions of the critically endangered plant species Commiphora wightii in India. We also evaluate how niche modelling affects its extent of occurrence (EOO) and area of occupancy (AOO). Results The area under the receiver operating curve (AUC) values produced by the maximum entropy (Maxent) under various bioclimatic time frames were more than 0.94, indicating excellent model accuracy. Non-bioclimatic characteristics, with the exception of terrain slope and aspect, decreased the accuracy of our model. Additionally, Maxent accuracy was the lowest across all combinations of bioclimatic and non-bioclimatic variables (AUC = 0.75 to 0.78). With current, 2050, and 2070 bioclimatic projections, our modelling revealed the significance of water availability parameters (BC-12 to BC-19, i.e. annual and seasonal precipitation as well as precipitation of wettest, driest, and coldest months and quarters) on habitat suitability for this species. However, with 2090 projection, energy variables such as mean temperature of wettest quarter (BC-8) and isothermality (BC-3) were identified as governing factors. Excessive salt, rooting conditions, land use type (grassland), characteristics of the plant community, and slope were also noticed to have an impact on this species. Through distribution modelling of this species in both its native (western India) and exotic (North-east, Central Part of India, as well as northern and eastern Ghat) habitats, we were also able to simulate both its fundamental niche and its realized niche. Our EOO and AOO analysis reflects the possibility of many new areas in India where this species can be planted and grown. Conclusion According to the calculated area under the various suitability classes, we can conclude that C. wightii's potentially suitable bioclimatic distribution under the optimum and moderate classes would increase under all future bioclimatic scenarios (2090 > 2050 ≈ current), with the exception of 2070, demonstrating that there are more suitable habitats available for C. wightii artificial cultivation and will be available for future bioclimatic projections of 2050 and 2090. Predictive sites indicated that this species also favours various types of landforms outside rocky environments, such as sand dunes, sandy plains, young alluvial plains, saline areas, and so on. Our research also revealed crucial information regarding the community dispersion variable, notably the coefficient of variation that, when bioclimatic + non-bioclimatic variables were coupled, disguised the effects of bioclimatic factors across all time frames.