Soil Depth Research Articles

Can silvopasture with arboreal legumes increase root mass at deeper soil layers and improve soil aggregation?

AbstractSilvopastoral system (SPS) is a multifunctional agroforestry practice. This study evaluate soil properties and root biomass under SPS in Pernambuco, Brazil. The experiment was established in 2011. The treatments were (1) monoculture signalgrass (MS) [Urochloa decumbens (Stapf.) R. D. Webster], (2) intercropped pasture of signalgrass with legume Gliricidia (SG) [Gliricidia sepium (Jacq.) Steud.], and (3) intercropped pasture of signalgrass with legume sabiá (SS) (Mimosa caesalpiniifolia Benth). Treatments were allocated in randomized complete block design with three replications. Samples were collected at 0‐ to 10‐, 10‐ to 20‐, 20‐ to 40‐, 40‐ to 60‐, 60‐ to 80‐, 80‐ to 100‐, and 100‐ to 120‐cm soil depths. Soil samples were also taken from the native forest (NF) considered as a reference at the same Experimental Station. Legume SPS (SG and SS) presented greater root biomass per unit area compared to MS at 60‐ to 80‐cm depth (p < 0.05); however, MS had greater root biomass per hectare at the top layers. The average values of the weighted mean diameter of soil aggregates were 3.20, 3.19, 3.07, and 3.27 mm in MS, SG, SS, and NF, respectively, at 0‐ to 120‐cm depths. The SPS increased soil cation exchange capacity in deeper layers, indicating greater biological activity at greater depth. Grasslands and SPS store 235 Mg C ha−1 with 71% of that found in deeper layers (20–120 cm). SPS with signalgrass intercropped with arboreal legumes has potential to improve deep soil C storage and resilience of livestock systems in tropical regions.

Unraveling soil geochemical, geophysical, and microbial determinants of the vertical distribution of organic phosphorus pesticide pollutants

Pesticide contamination has emerged as a global threat to humans. Here, we investigate the soil distribution pattern of organic phosphorus pesticide contamination at a pesticide manufacturing site in northern China, exploring their relationships with soil properties and microbial communities. The concentrations of four organic phosphorus pesticides (i.e., phorate, terbuthion, fenitrothion, and parathion) decreased substantially with soil depths from the surface down to 2 m. However, terbuthion, fenitrothion, and parathion had second-peak concentrations at a depth of 8 m. The concentrations of those organic phosphorus pesticides were negatively correlated with soil water content, but positively correlated with sulfide, pH, and total phosphorus. The distribution patterns of organic phosphorus pesticides closely aligned with that of soil organic matter and clay minerals, especially in the presence of montmorillonite, kaolinite, and chlorite. Various bacterial genera known to degrade organic phosphorus pesticides, such as Flavobacterium, Bacillus, Acinetobacter, Lactobacillus, Pseudomonas, Sphingomonas, and Thiobacillus, were correlated with these pesticides. Since these genera were among the top 50 abundant genera in our samples, they might play a significant role in the degradation of organic phosphorus pesticides. Together, this study unveils previously unrecognized pesticide-soil-microbe interactions, thus providing an important knowledge basis for environmental remediation strategies.

Greater variation of soil organic carbon in limestone- than shale-based soil along soil depth in a subtropical coniferous forest within a karst faulted basin of China

Lithology strongly influences soil microbial traits and edaphic factors and in turn soil organic carbon (SOC) dynamics. However, the effect of lithology on microbial traits, edaphic factors and resulting SOC physical fractions variation along soil depth remains inadequately understood in karst faulted basin of China. This understanding is critical for improving SOC stability. By separating SOC into labile particulate organic carbon (POC) and stable mineral-associated organic carbon (MAOC) over karst limestone and non-karst shale soil in a subtropical coniferous forest, we aimed to assess potential regulatory mechanisms underlying lithology-associated SOC stability variations across soil depth by integrating soil nutrients, mineralogical characteristics, and microbial traits. We found that SOC and its fractions were higher in limestone than in shale soil, which implying vegetation restoration effects on SOC and its fractions partly depending on lithology. Additionally, we found that the effects of soil depth on SOC and its fractions were greater in limestone soils than shale soils, and the ratios of MAOC to SOC (MAOC:SOC) and MAOC to POC (MAOC:POC) show a opposite trend in response to soil depth between two the lithologies. Variation partitioning and random forest analyses revealed that among multiple factors, the variation of SOC stability assessed via MAOC:SOC was mainly explained by microbial traits than soil nutrients and mineral properties. Contrast to soil depth, structural equation modeling analyses showed that lithology was the primary factor controlling the SOC stability when microbial traits, soil nutrients and mineralogical characteristics were controlled as conditional variables. Overall, these results highlight the crucial role of lithology in regulating the SOC stability along soil depth, which improve our understanding and management of soil carbon (C) pool in karst faulted basin of southwest China.

Debris flows analysis through quantitative evaluation of soil depth distribution under limited data

Soil depth is essential in studying natural disasters such as landslides and debris flow hazards. Despite the importance of soil depth in the mechanism of erosion-entrainment during the debris flow process, research on soil-depth data for analyzing debris flows is limited. Therefore, this study focused on the Gallam-ri area with a watershed of 0.9 km2 to evaluate the soil depth mapping under limited data and significance of these maps for debris flow simulations. Based on the knocking pole test data, two-dimensional distribution soil depth maps were constructed using the S and Z models, the Kriging method, and a method that applies some values uniformly as the soil depth (U model). The accuracy of soil depth mapping methods was quantitatively evaluated using R2 and root mean squared error analysis. Since soil depth demonstrated independent patterns with land-surface data, soil depth maps using S and Z models have structural limitations showing R2 of 0.0003 and 0.002, respectively. The debris flows were analyzed through numerical model Deb2D, and the soil depth most significantly influenced the erosion volume and the damaged area. Analyses using S and U models showed 94 % and 98 % high similarity to the simulation results through the Kriging method, respectively. However, considering overall analyses, the S model was analyzed to be the most stable in constructing soil depth maps and simulating debris flows for ungauged basins.

Effect of fire on microbial necromass carbon content is regulated by soil depth, time since fire, and plant litter input in subtropical forests

Effect of fire on microbial necromass carbon content is regulated by soil depth, time since fire, and plant litter input in subtropical forests

Crop diversity significantly enhances soil carbon sequestration via alleviating soil inorganic carbon decline caused by rhizobium inoculation

Increasing crop diversity and nitrogen (N) fertilizer application have been identified as effective strategies for enhancing productivity and soil organic carbon (SOC) storage in agroecosystems. However, the impact of these management practices on soil inorganic carbon (SIC) in agroecosystems remains unclear. At present, we evaluated the effects of maize/faba bean intercropping, N application rates, and inoculation rhizobia of faba bean on SIC in the top 20 cm of soil depth using a 13-year crop diversity field experiment. Our results showed that the soil total carbon (TC) content increased significantly by 5.9 % and 7.0 % compared to faba bean monoculture and maize monoculture, respectively, after 13 years of continuous intercropping. Intercropping increased the pedogenic carbonate (PIC) content by 36.7 %, resulting in an 8.9 % higher SIC content compared to faba bean monoculture. Additionally, intercropping significantly reduced the dissolution of lithogenic carbonate (LIC) by 17.5 %, leading to a 7.6 % higher SIC content compared to maize monoculture. The formation of PIC was associated with an increase in soil available cations especially Ca2+ in intercropping. The conservation of LIC was related to the higher soil available Mg2+ in intercropping than monoculture. Faba bean inoculated with rhizobia significantly decreased SIC content due to soil acidification after 13 years of continuous cropping. Intercropping also significantly increased SOC and C3-derived SOC content compared to maize monoculture and increased C4-derived SOC content compared with faba bean monoculture. Soil organic carbon showed a positive correlation with SIC across all cropping systems, and the SOC fractions could affect the neoformation of PIC and dissolution of LIC. Our results demonstrate that intercropping can increase SIC content, which further promotes soil carbon sequestration. This study highlights the significance of increasing crop diversity on cropland carbon sequestration and provides practical implications for mitigating carbon emissions.

Optimizing Ridge–Furrow Ratio to Improve Water Resource Utilization for Wheat in the North China Plain

The shortage of water resources seriously limits sustainable production in agriculture, and the ridge–furrow planting pattern is an effective water-saving cultivation pattern. However, the mechanism of the ridge–furrow planting pattern that drives the efficient utilization of field water resources in the North China Plain (NCP) is still unclear. A two-year field experiment was conducted in the NCP from 2021 to 2023. The ridge–furrow planting patterns followed a randomized block design as follows: ridge–furrow ratios of 50 cm:50 cm (M2), 75 cm:50 cm (M3), and 100 cm:50 cm (M4). A traditional planting pattern was used as the control (M1). These were used to investigate the effects of different treatments on water use and roots. The results showed that M3 reduced the amount of irrigation, improved water distribution after irrigation, increased water use efficiency (WUE), and promoted root growth. Compared with other treatments, M3 increased soil water consumption at a 0–100 cm soil depth by 6.76–21.34% (average values over two years), root length density by 8.46–20.77%, and root surface area density by 7.87–22.13%. On average, M3 increased grain yields by 3.96–9.80%, biomass yields by 5.32–10.94%, and WUE by 4.5–9.87%. In conclusion, M3 is an effective planting pattern for improving the yield and WUE of wheat in the NCP.

The role of wild red deer on soil physical properties in a Mediterranean ecosystem: insights from a Portuguese mountain.

In this study we aimed to assess the role of wild red deer, along with other ungulates such as roe deer and wild boar, in the soil's physical properties, namely soil penetration resistance and depth (used as a proxy for soil compaction), hydraulic conductivity (a proxy for water infiltration), and the proportion of soil stable aggregates. Results showed that, at the density level found in our study area, red deer have a neutral effect at the soil level, not causing significant soil compaction or significantly influencing measured soil functions.

Intercropping in Coconut Plantations Regulate Soil Characteristics by Microbial Communities

Intercropping is a commonly employed agricultural technique that offers numerous advantages, such as increasing land productivity, enhancing soil health, and controlling soil-borne pathogens. In this study, Artemisia argyi, Dioscorea esculenta, and Arachis pintoi were intercropped with coconuts and compared with naturally growing weeds (Bidens pilosa), respectively. The regulatory mechanism of intercropping was examined by analyzing the variability in soil properties and microbial community structure across different intercropping modes and soil depths (0–20 cm, 20–40 cm, and 40–60 cm). The results indicate that intercropping can increase the diversity of soil bacteria and fungi. Moreover, as soil depth increases, the changes in microbial communities weaken. Intercropping reduced soil SOM and increased pH, which is directly related to the changes in the abundance of Acidobacteria in the soil. In various intercropping systems, the disparities resulting from intercropping with A. pintoi are particularly pronounced. Specifically, intercropping with A. pintoi leads to an increase in soil potassium and phosphorus levels, as well as an enhancement in the abundance of Bacillus sp., which plays a crucial role in the suppression of plant pathogenic fungi within the soil ecosystem. The results of the correlation analysis and structural equation modeling (SEM) suggest that the impacts of three intercropping systems on microbial composition and soil indicators exhibit considerable variation. However, a common critical factor influencing these effects is the soil phosphorus content. Furthermore, our findings indicate that intercropping resulted in lower soil nitrogen levels, exacerbating nitrogen deficiency and masking its impact on the microbial community composition.

Effects of occasional tillage on soil physical and chemical properties and weed infestation in a 10-year no-till system

Few studies have investigated how one-time targeted tillage of long-term no-till fields impacts topsoil properties and weed dynamics. An on-farm trial was implemented in 2020 to test the effects of occasional tillage (OT) in Morocco with a long-term no-tillage (NT) system and rainfed field crops: durum wheat (Triticum durum), faba bean (Vicia faba minor), and chickpea (Cicer arietinum). Four treatments were established, namely, continuous NT with crop residues maintained (“NT + residue”); continuous NT with crop residues not maintained (“NT-residue”); shallow inversion tillage (“shallow OT”); and deep non-inversion tillage (“deep OT”). We assessed the effect of these treatments on soil physical and chemical properties in 0–10 and 10–20 cm soil depths after crop harvest of the 2020–2021 (year 1) and 2021–2022 (year 2) growing seasons corresponding to 1 and 2 years after OT, respectively. In addition, we evaluated the effect of the treatments on weed populations and the effect of the legume crop rotated with wheat on soil nitrogen (N) and weed density. In year 1, deep OT reduced the water content at field capacity and available water capacity at 0–10 cm compared to continuous NT; the cation-exchange capacity (CEC) under deep OT was lower than in NT-residue and NT + residue at 0–10 cm and 10–20 cm, respectively. Furthermore, deep OT increased ammonium-N (NH4-N) at 0–10 and 10–20 cm compared to NT + residue but reduced exchangeable potassium (K) at 10–20 cm depth compared to NT-residue. In year 2, shallow OT had lower total porosity at 10–20 cm than NT + residue, while shallow and deep OT recorded higher water-stable aggregates at 0–10 cm than NT + residue; at 10–20 cm, deep OT recorded lower CEC than NT + residue. However, deep OT had higher nitrate-N (NO3-N) and available sulfur (S) than NT-residue at 10–20 cm. Occasional tillage did not significantly affect 10 out of 19 of the soil properties evaluated, including soil organic matter (SOM), in all the years and did not help reduce the stratification of soil nutrients in NT. In year 1, 50 days after OT, deep OT reduced the weed density by 46% compared to NT + residue, while in year 2, 406 days after OT, shallow OT reduced weed density by 53% compared to NT-residue. Regarding the effect of the legume rotated with wheat, faba bean appeared to be the better preceding or following wheat crop as it resulted in higher residual soil mineral N and lower weed infestation than chickpea.

Effects of phosphorus fertilizer type and dripline depth on root and soil nutrient distribution, nutrient uptake, and maize yield under subsurface drip fertigation

ContextSubsurface drip irrigation can potentially increase nutrient uptake by altering the spatial distribution of nutrients and roots, but the efficiency enhancement potential of different phosphorus (P) sources combined with varying dripline depths still requires further evaluation. MethodsWe established a 2-year field experiment with spring maize in 2021 and 2022 to determine the regulatory effects of three P sources [P1, monoammonium phosphate (MAP); P2, ammonium polyphosphate (APP); and P0, no P] and three dripline depths (D0, surface drip irrigation, 0 cm; D15, subsurface at 15 cm depth; and D30, subsurface at 30 cm depth) on the soil NO3-N, NH4-N and Olsen-P distribution, root distribution, nitrogen (N) fertilizer partial factor productivity (PFPN) and P use efficiency (PUE), and grain yield. ResultsWe found a significant coupling effect between the P source and dripline depth, both of which significantly impacted soil nutrients and root distribution, grain yield, PFPN, and PUE. In P1D15 and P2D15, the highest soil NO3-N and Olsen-P contents were observed at soil depths of 0–30 and 10–20 cm and at 0–30 and 10–30 cm, respectively. Similarly, in P1D30 and P2D30, which were 20–40 and 20–40 cm, and 20–40 and 30–60 cm, respectively. Compared to the other treatments, P2D15 and P1D30 exhibited considerable increases in root length density at the 30–60 cm soil depth of 37∼52 % and 28∼58 %, respectively. Regardless of the dripline depth, P0 resulted in the lowest yield during both growing seasons. P1D30 and P2D15 were found to be the optimal combinations for achieving higher grain yield, PFPN, and PUE, as they were able to achieve a high degree of coordination between soil available N and Olsen-P, as well as root distribution. ConclusionsThe recommended approach for optimizing nutrient and root spatial distributions under subsurface drip irrigation systems involves the use of poly-P fertilizer (APP) in conjunction with shallow dripline depth and ortho-P fertilizer (MAP) paired with deep dripline depth, which provides valuable guidance for co-fertigation practices involving N and P fertilizers.

Stomatal and Non-Stomatal Leaf Responses during Two Sequential Water Stress Cycles in Young Coffea canephora Plants

Understanding the dynamics of physiological changes involved in the acclimation responses of plants after their exposure to repeated cycles of water stress is crucial to selecting resilient genotypes for regions with recurrent drought episodes. Under such background, we tried to respond to questions as: (1) Are there differences in the stomatal-related and non-stomatal responses during water stress cycles in different clones of Coffea canephora Pierre ex A. Froehner? (2) Do these C. canephora clones show a different response in each of the two sequential water stress events? (3) Is one previous drought stress event sufficient to induce a kind of “memory” in C. canephora? Seven-month-old plants of two clones (’3V’ and ‘A1’, previously characterized as deeper and lesser deep root growth, respectively) were maintained well-watered (WW) or fully withholding the irrigation, inducing soil water stress (WS) until the soil matric water potential (Ψmsoil) reached ≅ −0.5 MPa (−500 kPa) at a soil depth of 500 mm. Two sequential drought events (drought-1 and drought-2) attained this Ψmsoil after 19 days and were followed by soil rewatering until a complete recovery of leaf net CO2 assimilation rate (Anet) during the recovery-1 and recovery-2 events. The leaf gas exchange, chlorophyll a fluorescence, and leaf reflectance parameters were measured in six-day frequency, while the leaf anatomy was examined only at the end of the second drought cycle. In both drought events, the WS plants showed reduction in stomatal conductance and leaf transpiration. The reduction in internal CO2 diffusion was observed in the second drought cycle, expressed by increased thickness of spongy parenchyma in both clones. Those stomatal and anatomical traits impacted decreasing the Anet in both drought events. The ‘3V’ was less influenced by water stress than the ‘A1’ genotype in Anet, effective quantum yield in PSII photochemistry, photochemical quenching, linear electron transport rate, and photochemical reflectance index during the drought-1, but during the drought-2 event such an advantage disappeared. Such physiological genotype differences were supported by the medium xylem vessel area diminished only in ‘3V’ under WS. In both drought cycles, the recovery of all observed stomatal and non-stomatal responses was usually complete after 12 days of rewatering. The absence of photochemical impacts, namely in the maximum quantum yield of primary photochemical reactions, photosynthetic performance index, and density of reaction centers capable of QA reduction during the drought-2 event, might result from an acclimation response of the clones to WS. In the second drought cycle, the plants showed some improved responses to stress, suggesting “memory” effects as drought acclimation at a recurrent drought.

Labile Fraction of Organic Carbon in Soils from Natural and Plantation Forests of Tropical China

Labile organic carbon (LOC) is a key driver of forest ecosystem function and may mitigate global climate change through carbon sequestration. To explore the accumulation of LOC in tropical forest soils, we sampled from both planted and natural forests in Hainan Province, the southernmost province of China. We analyzed the concentrations of total organic carbon (TOC) and LOC and characterized various physicochemical properties such as pH and soil texture to understand their inter-relationships in tropical natural and plantation forests. Although the TOC concentration was higher in plantation forests (88.61 g/kg) than in natural forests (68.73 g/kg), the LOC concentration was higher in natural forests (5.12 mg/g) than in plantation forests (4.07 mg/g). Over a depth range of 0–50 cm from the surface, both forest types showed decreasing TOC and LOC concentrations with increasing soil depth, indicating surface aggregation. The soil is slightly acidic and primarily composed of sand particles. Correlation analysis showed a highly significant negative correlation between LOC concentration and soil pH in both forest types (p < 0.01). Soil LOC was positively correlated with soil clay and silt particles and negatively correlated with sand particles. This study provides valuable insights into soil carbon sequestration in tropical rainforest ecosystems in both plantation and natural tropical forests.

Soil chemical characteristics, yield and technological quality of sugarcane under subsurface drip irrigation with treated sewage effluent

ABSTRACT Sugarcane cultivation requires sustainable strategies to meet water and nutritional needs. This study tested the hypothesis that irrigation with treated sewage effluent (TSE) can meet the water needs of sugarcane plants, improving their technological quality and yield. The objective of this study was to assess the effects of subsurface drip irrigation (SDI) with TSE or surface reservoir water (SRW) on soil chemical characteristics and technological quality and productivity. Thus, an SDI system was installed at soil depths of 0.20 and 0.40 m to apply SRW and TSE to sugarcane plants, composing four irrigation treatments (TSE0.2 m, TSE0.4 m, SRW0.2 m and SRW0.4 m) and a control (non-irrigated treatment). Analyses of soil chemical characteristics in different layers showed no negative effects for the use of SDI, which maintained favorable soil conditions for sugarcane plantations. The surface layer (0–0.2 m) irrigated with SRW or TSE showed higher accumulation of nutrients and organic matter. The results confirmed the hypothesis that irrigation with TSE or SRW improves the technological quality and yield of sugarcane; the treatment TSE0.2 m showed the best results regarding increases in sugar yield and alcohol production. However, continuous monitoring of soil salinity is necessary in wastewater-irrigated agricultural systems.

Phenotypic plasticity of water-related traits reveals boundaries to the adaptive capacity of a dominant European grass species under increased drought

The intensification of droughts due to climate change is a global concern, and many plant species face increasing water deficits. Understanding the role of phenotypic plasticity in plant adaptation to these changing conditions is crucial. This research focuses on Bromopsis erecta, a dominant perennial grass in European and Mediterranean grasslands, to predict its potential adaptation to climate change. We assessed plants from shallow and deep soils (i.e., with contrasting water reserves) of a Mediterranean rangeland in southern France, and tested the effect of six years of experimentally increased summer drought compared to the ambient conditions on plant traits, survival and abundance. In both field and common garden experiments, we measured water-related traits, including static traits under non-limiting water conditions, and dynamic traits, such as rates of trait variation during drought. Trait plasticity was determined as a reaction norm to increasing soil water stress and was tested against changes in B. erecta abundance over the past decade, including the study period. Trait plasticity was detected only for leaf dry matter content (LDMC), revealing that the resource strategy of B. erecta became more conservative over less than a decade with higher LDMC and leaf thickness according to the plant economic spectrum. No plasticity was found for osmotic potential or specific leaf area. The variability of other traits was ascribed to the possible lagging effect of previous water stress and was associated more with soil depth than with previous summer drought intensity. The abundance decline of B. erecta, which dropped from 20 % to around 5 % in shallow soils, was not associated with the plasticity of LDMC but was positively correlated with variations in leaf base membrane damage, meaning unexpectedly, that plants exposed to the most severe summer drought also had the most sensitive leaf base membranes, a possible sign of maladaptive trait plasticity in the population. This key trait response reveals boundaries to the adaptive capacity of this perennial grass to survive pluri-annual drought.

Differential Responses of Soil Nitrogen Forms to Climate Warming in Castanopsis hystrix and Quercus aliena Forests of China

Climate warming impacts soil nitrogen cycling in forest ecosystems, thus influencing their productivity, but this has not yet been sufficiently studied. Experiments commenced in January 2012 in a subtropical Castanopsis hystrix Hook. f. and Thomson ex A. DC. plantation and in May 2011 in a temperate Quercus aliena Blume forest, China. Four treatments were established comprising trenching, artificial warming (up to 2 °C), artificial warming + trenching, and untreated control plots. The plots were 2 × 3 m in size. In 2021 and 2022, soil nitrogen mineralization, soil nutrient availability, fine root biomass and microbial biomass were measured at 0–20 cm soil depth in 6 replicate plots per treatment. Warming significantly increased soil temperature in both forests. In the C. hystrix plantation, warming significantly increased available phosphorus (AP) and fine root biomass (FRB), but it did not affect soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) and their ratios. Warming depressed the net mineralization rate (NMR) and net ammonification rate (NAR) of the C. hystrix plantation, probably because the competition for nitrogen uptake by fine roots and microorganisms increased, thus decreasing substrates for nitrogen mineralization and ammonification processes. Trenching and warming + trenching increased the net nitrification rate (NNR), which might be related to decreased NH4+-N absorption of trees in the trenched plots and the increased microbial activity involved in soil nitrification. In the Q. aliena forest, warming significantly increased NH4+-N, MBC/MBN, Root C/N, Root N/P, and decreased pH, MBN, MBN/MBP and Root P; and there was no effect of trenching. Notably, the NAR, NNR and NMR were largely unaffected by long-term warming. We attributed this to the negative effect of increasing NH4+-N and decreasing MBN/MBP offsetting the positive effect of soil warming. This study highlights the vulnerability of subtropical forest stands to long-term warming due to decreased soil N mineralization and increased NO3−-N leaching. In contrast, the soil N cycle in the temperate forest was more resilient to a decade of continuous warming.

Application of coupled WetSpass-M and MODFLOW models to estimate spatial–temporal water balance components in the Chemoga watershed, Ethiopia

ABSTRACT The groundwater level in the Chemoga watershed has been declining due to an increase in water demand, anthropogenic activities, and climate change effects. This paper uses the WetSpass-MODFLOW coupling to evaluate the groundwater recharge in the Chemoga watershed. The MODFLOW groundwater flow simulation model is then used to simulate the hydraulic head distribution based on these findings. The input data of WetSpass models are soil, land cover, topography, slope, and groundwater depth, as well as monthly meteorological characteristics (such as temperature, wind speed, and rainfall). The long-term spatial and temporal average annual precipitation of 1,453 mm is distributed as 169 mm (11.63%) groundwater recharge and 879 mm (60.5%) surface runoff, while 405 mm (27.87%) is lost through evapotranspiration. In such seasonal variations, the groundwater head due to the wet/summer stress period varied from 4 to 41 m. While in the dry/winter stress period groundwater head varied from 3.5 to 39.8 m, and also the groundwater head due to the annual stress period varied from 3.7 to 40 m. The findings are extensive and can be applied to water resource management and groundwater resource development in a sustainable manner by safeguarding high groundwater recharge locations, and reevaluating allowable groundwater abstraction rates.

Spatio-temporal Dynamics of Land Use/Cover Change and Associated Carbon Stocks in Kanyabaha Wetland in Rukiga District, Uganda

Wetlands play an important ecological function of sequestering atmospheric carbon dioxide and thereby moderating adverse impacts of climate change. It is therefore important to understand the dynamics of carbon stocks in wetland vegetation and soils. This study investigated the spatio-temporal dynamics of aboveground, belowground, and total carbon stocks in Kanyabaha Wetland, located in Rukiga District, Uganda, spanning from 1990 to 2021. Through field sampling and laboratory analysis, aboveground carbon stocks were assessed by harvesting vegetation biomass and converting it to carbon stock using established conversion factors. Soil samples collected at different depths (0-20cm, 20-50cm, 50-100cm) were analyzed for soil organic carbon content to determine belowground carbon stocks. The study reveals variable spatio-temporal patterns of carbon stocks across land use types, with papyrus-dominated areas exhibiting the highest aboveground carbon stocks (49.66 tC/ha), followed by small-scale farmlands (33.73 tC/ha) and tree plantations (23.01 tC/ha). Conversely, built-up areas exhibit the lowest carbon stocks (1.29 tC/ha). Temporal analysis reveals fluctuating patterns in carbon stocks, with increases observed in built-up areas and small-scale farmlands, and decreases in grasslands and tree plantations that could be due to changes in hydrological cycle. Belowground carbon stocks follow similar trends, with papyrus areas maintaining the highest stocks (39.96 tC/ha), particularly at deeper soil depths that exhibit the highest carbon accumulation due to its extensive network of papyrus rhizome. Changes in land use, especially reclamation of the wetlands for farming and settlements affected carbon capture and storage in the wetland ecosystem. These findings highlight the importance of targeted conservation of natural wetlands and sustainable land management strategies in the Kanyabaha Wetland catchment for enhanced carbon sequestration. Further, in depth studies in the variability of carbon stocks due to various eco-climatic factors and anthropogenic activities are necessary to support sustainable wetland land management practices in Uganda.

Land degradation vulnerability mapping using geospatial techniques: a case study of Nandakini River basin, NW Himalaya, India

ABSTRACT Land degradation is a significant global environmental issue, and its prevention has become a serious concern of the twenty-first century, particularly in the context of anthropogenic impact and climate change. It is crucial to map and assess the grade of land degradation to determine vulnerable areas. The Indian Himalayan region faces heightened risks with its steep terrain, active tectonics, heavy precipitation, and human interventions. This study focuses on the Nandakini Watershed. Employing AHP technique, the study calculates the Land Degradation Vulnerability Index (LDVI) using slope, terrain ruggedness, rainfall, temperature, LULC, soil depth, and organic carbon content. The results indicate that the upper region is highly vulnerable, and a higher slope influences the runoff in the area, followed by factors like NDVI and rainfall, collectively contributing to 62% of the overall index. In this context, the upstream regions of the watershed display a high LDVI, while most of the area falls within the low LDVI category. This indicates that approximately 2.10% of the study area is highly susceptible to soil erosion. RUSLE-based estimates have been used to further validate the LDVI result. The integrated LDVI offers a valuable tool for prioritising soil conservation and disaster mitigation.

Intra‐annual dynamics of soil and microbial C, N, and P pools in a Central Amazon Terra Firme forest

AbstractBackgroundTropical ecosystem functioning is influenced by seasonal fluctuations in precipitation, but the impact on soil nutrient cycling and microbial stoichiometry is not fully understood.AimThis study investigates the magnitude of intra‐annual fluctuations in nutrient availability and microbial biomass in a tropical forest soil by examining carbon (C), nitrogen (N), and phosphorus (P) pools.MethodsWe analyzed the total, extractable, and microbial C, N, and P contents and their stoichiometry in Terra Firme Ferralsols, representative for the central Amazon basin.ResultsWe observed intra‐annual variations in resource availability, particularly between wet and dry seasons. Despite relatively stable total C, N, and P stocks throughout the year, we observed a decrease in extractable organic C and available (Olsen) P and an increase in extractable N in the dry season compared to the wet season. Microbial biomass pools and stoichiometry also varied across sampling dates and soil depths: relative to microbial‐C and ‐N, microbial‐P decreased in both wet and dry season and increased in the transition from wet to dry season.ConclusionsOur research highlights intra‐annual variation in nutrient pools, particularly dynamic microbial carbon and nutrient fractions, in weathered tropical forest soils.