Radon diffusion through thin plastics

Decrease in productivity of pastureland is a common problem in dry areas and needs to be enhanced through conservation and management of soil biodiversity and available plant resources. Diversity and population dynamics of soil arthropods, and soil nutrients were studied in different silvopastoral (tree-integrated grassland) systems for effective management and enhancement of grassland productivity. The most prominent combinations of trees and grasses in silvopastoral systems of the selected sites were Prosopis cineraria with Cenchrus ciliaris and C. biflorus (PC), Acacia nilotica with Elusine compressa and C. ciliaris (AN), Zizyphus nummularia with C. ciliaris and E. compressa (ZN), Capparis decidua with C. biflorus and Digitaria marginatus (CD) and A. senegal with C. ciliaris and D. marginatus (AS). Pure grass blocks outside tree canopy were selected as control plots. Acari, Myriapoda, Coleoptera, Isoptera, Collembola and other soil arthropods were the major soil faunal groups. Relative densities of Acari, Myriapoda and other arthropods were highest in silvopastoral systems and those of Coleoptera, Isoptera and Collembola were highest in pure grass plots. Variations in soil arthropod populations in response to rainfall, soil water content and soil temperature indicated greater sensitivity of these groups to environmental factors. The highest densities and negative relative tree effect (RTE) values of Acari, Myriapoda and other soil arthropods in the ZN, Coleoptera in the AS, Isoptera in the CD and Collembola in the AN systems indicated that these soil arthropods preferred the silvopastoral systems involved. Seasonal variations in soil organic matter and available NH4-N, NO3-N and PO4-P were similar to those of soil arthropods. The concentrations of soil nutrients were highest in the ZN system, which had the highest densities of soil arthropods. The other systems with high populations and soil nutrient status were the CD and AS. Silvopastoral systems based on Z. nummularia, C. decidua and A. senegal promoted soil arthropod populations and enhanced soil nutrient status, highlighting the positive role of tree presence and the need for proper management to promote soil biodiversity, nutrient cycling and sustained production in a fragile environment.

Afforestation of a floodplain system in Paraguay with eucalyptus: Effects on soil properties and nutrient stocks

Factors determining soil nutrient distribution in a small-scaled watershed in the purple soil region of Sichuan Province, China

The abundance of living cells in wood—mainly as interconnected axial and ray parenchyma networks—varies widely between species. However, the functional significance of this variation and its role in plant ecological strategies is poorly understood, as is the extent to which different parenchyma fractions are favored in relation to soil nutrients and hydraulic functions. We analyzed wood tissue fractions of 16 Australian angiosperm species sampled from two nearby areas with similar climate but very different soil nutrient profiles and investigated structure-function links with soil and tissue nutrient concentrations and other plant traits. We expected the variation in parenchyma fractions to influence nutrient concentrations in wood xylem, and to find species with lower parenchyma fractions and accordingly lower nutrient requirements on lower-nutrient soils. Surprisingly, both axial and ray parenchyma fractions were mostly unrelated to tissue and soil nutrient concentrations, except for nitrogen concentration in stem sapwood. Species from low nutrient soils showed higher fractional P translocation from both leaves and sapwood, but little patterning with respect to tissue nitrogen. While species from high and low nutrient soils clearly clustered along the soil-fertility axis, their tissue composition varied independently from plant functional traits related to construction costs and hydraulic anatomy. Our findings imply that there is considerable variation among species in the nutrient concentrations within different parenchyma tissues. The anatomical composition of wood tissue seems unrelated to plant nutrient requirements. Even though xylem parenchyma is involved in metabolic functions such as nutrient translocation and storage, parenchyma abundance on its own does not directly explain variation in these functions, even in co-occurring species. While parenchyma is highly abundant in wood of angiosperm trees, we are still lacking a convincing ecological interpretation of its variability and role in whole-tree nutrient budgets.

Landslide disaster risk reduction necessitates the investigation of different geotechnical causal factors for slope failures. Machine learning (ML) techniques have been proposed to study causal factors across many application areas. However, the development of ensemble ML techniques for identifying the geotechnical causal factors for slope failures and their subsequent prediction has lacked in literature. The primary goal of this research is to develop and evaluate novel feature selection methods for identifying causal factors for slope failures and assess the potential of ensemble and individual ML techniques for slope failure prediction. Twenty-one geotechnical causal factors were obtained from 60 sites (both landslide and non-landslide) spread across a landslide-prone area in Mandi, India. Relevant causal factors were evaluated by developing a novel ensemble feature selection method that involved an average of different individual feature selection methods like correlation, information-gain, gain-ratio, OneR, and F-ratio. Furthermore, different ensemble ML techniques (Random Forest (RF), AdaBoost (AB), Bagging, Stacking, and Voting) and individual ML techniques (Bayesian network (BN), decision tree (DT), multilayer perceptron (MLP), and support vector machine (SVM)) were calibrated to 70% of the locations and tested on 30% of the sites. The ensemble feature selection method yielded six major contributing parameters to slope failures: relative compaction, porosity, saturated permeability, slope angle, angle of the internal friction, and in-situ moisture content. Furthermore, the ensemble RF and AB techniques performed the best compared to other ensemble and individual ML techniques on test data. The present study discusses the implications of different causal factors for slope failure prediction.

Degradation of soil functions in storing and cycling nutrients may be related to topography and land-use change. The research aimed to analyze the impact of land-use changes and slope positions on soil function in nutrient stock within Kalikungkuk micro watershed of East Java, Indonesia. Four different land-uses such as vegetable crops, agroforestry, shrub and forest were selected with three slope positions (e.g. ridge, slope, and valley), and three replications of each. Soil samples were collected at 0-10, 10-30, 30-50, and 50-100 cm depth of soil. Variables measured included soil properties (e.g. bulk density, soil texture, pH, CEC, soil nutrients). Slope positions impact on differences in soil physical (i.e. soil bulk density, soil texture) and chemical (i.e. total N, exchangeable K) properties. In addition, forest conversion to other land-uses (i.e. agroforestry, shrub, vegetable crops) decreased soil nutrient concentration (i.e. total C, total N, Ca, Mg, Na), and consequently resulted in degradation of soil nutrient stocks of especially C and N. The strong positive correlation between soil nutrient stock (e.g. C and N) and vegetation cover such as canopy cover, basal area, and litter (r = 0.63 – 0.78, r table 1% = 0.39) showed the benefit of biodiversity in maintaining soil function on the nutrient stock.

Peat formation is the main key to carbon sequestration in the Peat Swamp Forest (PSF). The research aims to analyze alternative possibilities for peat formation based on the available soil nutrients and dried biomass. In a complete randomized block design, a factorial trial was applied using two treatment combinations in three blocks: factor A (sampling plots, land cover) and Factor B (dried biomass). Data were analyzed using two-way ANOVA and Tukey Honestly Significant Difference test at a significance level of 5%. A high supply of dried below-ground biomass did not follow the production of rooting litter at high soil nutrients. Most of the biomass was transported upwards into above-ground biomass. All land covers produced above-ground biomass which had the potential to form peat with significant differences for all parameters studied. The potential for peat formation was highly dependent on the various types of land covers (e.g. peat forest), environmental factors, the composition of the seed bank, and the species ability to compete. Restoration actions (revegetation, rewetting, and revitalization) aim to stimulate the development of peat-forming species. The research benefits are expected to enrich PSF's ecological restoration thinking so that PSF can be restored and returned to near its initial condition.

Soil nutrient depletion and inefficient fertilizer management remain major challenges for sustainable agriculture in Tanzania’s Southern Highlands. This study evaluates a low-cost, non-invasive dielectric sensing approach to monitor soil nutrient and moisture variability using a log-periodic dipole antenna (LPDA) system integrated with a nano vector network analyzer (NanoVNA). Soil samples from the middle and lower catena positions in Mbeya City were treated with varying concentrations (0–12.5%) of UREA and calcium ammonium nitrate (CAN), and dielectric properties permittivity and conductivity were measured under controlled moisture levels (10–40%). The results showed strong positive correlations between UREA concentration, dielectric constant (r = 0.905), and conductivity (r = 0.858), particularly in the lower catena. CAN showed a reliable response in the middle catena (r = 0.913 for εr) but inconsistent trends in the lower catena. Moisture content had a significant non-linear effect on dielectric behavior, with a peak response at 40% moisture. A two-way ANOVA confirmed statistically significant main and interaction effects (p < 0.05) for fertilizer type, concentration, and catena position. These findings validate the LPDA-NanoVNA system as an effective soil nutrient and moisture monitoring tool. The dielectric method is especially promising for supporting site-specific fertilizer applications and precision farming. UREA is more suitable for dielectric-based assessments in variable terrain, while CAN is more effective in stable slope environments. The approach advances low-cost, scalable technologies for climate-smart agriculture and aligns with SDG 15 goals on sustainable land use and soil health.

Arbuscular mycorrhizal fungi (AMF) can facilitate plant invasions, particularly in nutrient-depleted soils. Establishment of this mutualism often depends on both soil nutrients and secondary chemicals released by plants. Yet, it remains unclear how invasive plants maintain or enhance AMF colonization in nutrient-deficient soil. We investigated the effects of different levels of nitrogen (N: 0, 2, or 10 ppm) and phosphorus (P: 0, 6, or 25 ppm) added to sand in a factorial design on three flavonoids (isoquercitrin, quercitrin, quercetin) associated with AMF colonization in root exudates of Triadica sebifera from introduced and native populations. We assessed effects of soil nutrients alone on secondary chemical metabolism with sterilized growth substrate treatments. We found that plants from introduced populations had higher root exudate concentrations of quercitrin and quercetin plus greater AMF colonization than those from native populations under every N and P treatment combination. The effects of P availability on flavonoids depended on N availability. Flavonoid concentrations and AMF colonization decreased with P addition under no N treatment but increased with P addition under low N treatment. P addition had smaller effects on AMF colonization under the high N treatment. In sterilized growth substrate, P addition had stronger effects on quercitrin than quercetin. These results suggest that soil nutrients may influence AMF colonization by modifying flavonoids in root exudates. Our findings provide evidence that the responses of flavonoid metabolism to soil nutrients are an important driver of AMF colonization and the ability of invasive plants to sustain performance under nutrient stress.

This study was conducted with the main objective of determining the linkages between poverty and land management practices in Uganda. The study used the 2002/03 Uganda National Household Survey (UNHS) and more focused data collected from a sub-sample of 851 households of the 2002/03 UNHS sample households. We found that farmers in Uganda deplete about 1.2 percent of the nutrient stock stored in the topsoil per year, which leads to a predicted 0.31 percent reduction in crop productivity. The value of replacing the depleted nutrients using the cheapest inorganic fertilizers is equivalent to about 20 percent of household income obtained from agricultural production. Econometric analysis of the survey results provides evidence of linkages between poverty and land management practices. Land investments increase agricultural productivity and income and conserve natural resources. Many inputs and land management practices increase crop production per acre. We observed an inverse farm size – crop productivity relationship but a negative association of farm size and per capita income. Education of female household members has generally a limited impact on land management, while male education is associated with greater use of inorganic fertilizer. Both female post-secondary and male primary and secondary education are associated with higher crop productivity. Larger families use more erosive practices but realize higher value of crop production per acre but have lower per capita income. Access to financial capital, markets and roads has limited effect on land management. However, access to financial capital and non-farm opportunities increase crop productivity and per capita household income and access to roads contributes to higher per capita household income and less soil nutrient depletion. These results support the Uganda government poverty reduction strategy through building rural roads, and increasing access to financial capital and non-farm opportunities. Both the traditional and the new agricultural extension program increase use of fertilizer and crop productivity, suggesting that investment in extension services could significantly contribute to agricultural modernization and poverty reduction. The results suggest the need to give incentives for technical assistance programs to operate in remote areas, where access to extension services is limited. Perennial crop producers deplete soil nutrients more rapidly, implying the need to promote measures to restore soil nutrients in perennial (especially banana) production areas. We find no significant differences in crop productivity or income per capita associated with differences in land tenure systems. Our findings suggest that customary land tenure, which is the most common form of tenure, is not a constraint to improvements in land productivity or use of sustainable land management. Overall, our results provide general support for the hypothesis that promotion of poverty reduction and agricultural modernization through technical assistance programs and investments in infrastructure and education can improve agricultural productivity and help reduce poverty. However, they also show that some of these investments do not necessarily reduce land degradation, and may contribute to worsening land degradation in the near term. Thus, investing in poverty reduction and agricultural modernization is not sufficient to address the problem of land degradation in Uganda, and must be complemented by greater efforts to address this problem. Authors' Abstract

Eriophorum angustifolium (Cyperaceae) is a pioneer clonal sedge colonizing bare peat surface of harvested peatlands in central Europe. It forms circular patches of densely aggregated ramets, followed by central die-back and ring formation as circles develop. This study experimentally tested the importance of inter-ramet competition, interference with litter, soil nutrient depletion, and architectural constraints for radial clonal spread and ring formation process. Effects of fertilization, litter addition and competition of neighbor ramets on growth and survival of tillers transplanted into four distinct zones within individual circle were detected only in the first zone (green band) with high ramet density. This suggested that both above-ground competition for light and below-ground competition for soil nutrients can play an important role in population dynamics of E. angustifolium. A field study of clonal growth has shown that rhizomes orient preferentially towards the periphery. As the old ramets within the interior of the tussock died due to senescence and inter-ramet competition, disproportionately more ramets are recruited on the periphery, which reduce axillary bud availability within the interior of the tussocks. We also explored the soil nutrient content (NH4-N, NO3-N and PO4-P). High values of NO3-N outside the circles and low values inside patches might partly explain why Eriophorum rhizomes are oriented into open space. High accumulation of phosphorus (PO4-P) in the centre of the patches was attributed to the leaching of phosphorus from decaying Eriophorum plants. We suggest that processes of nutrient foraging and utilization are responsible for development of circular patches of E. angustifolium in the harsh environment of cut-away peatland.

The influence of abiotic stress and phenotypic plasticity on the distribution of invasive Alternanthera philoxeroides along a riparian zone

Patches of wooded vegetation in nutrient-poor grassland characteristically contain high soil moisture and nutrient availability compared with surrounding grassland. These ‘islands of fertility’ appear stable in size, suggesting that tree recruitment at the patch boundary is limited. We hypothesize that tree establishment in adjacent grassland is limited by (1) competition for resources, (2) fire or (3) herbivory. In a South African grassland, we measured moisture availability and conducted a bioassay experiment to analyse whether soil nutrient limits tree recruitment at the patch boundary. We thus measured nutrient concentrations of maize plants grown in patch, boundary and grassland soil. To investigate whether browsing or fire affected tree seedlings at the patch boundary, we burned plots including patches, and used fences to exclude browsers. Neither soil moisture nor nutrient availability at the boundary differed from inside the patches, suggesting that tree recruitment at the boundary is not resource limited. Both fire and browsing combined caused a significantly lower tree seedling growth at the patch boundary, suggesting that these two factors can impede tree recruitment. The balance between positive feedback mechanisms facilitating tree recruitment, and the negative impact of fire and browsing can explain the apparent stability of these islands of fertility.

This study determined the influence of soil nitrogen and phosphorus on the colonisation dynamics of arbuscular mycorrhizal fungi (AMF) and Dark Septate Endophytes (DSE) in plant species adapted to nutrient poor soils. Plant colonisation dynamics were investigated using a field experiment and a manipulative greenhouse experiment on Australian native seedlings. Tubestock of Poa labillardierei were transplanted into the field to large tracts of land of high and low nutrient availability, near Sydney, Australia, and root colonisation was determined from monthly plant collections over three months, between late austral autumn and through winter. In the greenhouse experiment, two native shrubs and one grass, respectively, Rhagodia candolleana, Dodonaea triquetra and P. labillardierei, were germinated from seeds and grown under a full factorial nitrogen and phosphorus fertilisation experiment for three months before root colonisation was determined. The selected study species were of varied mycotrophy. AMF colonisation in both experiments was lowest in plants from high nutrient treatments. Removal of either nitrogen or phosphorus from the fertiliser resulted in the same patterns of colonisation, with AMF being greater when either nutrient was removed. DSE colonisation was greatest in high nutrient soils. However, colonisation did not vary with nutrient treatments in the glasshouse experiment, suggesting that nitrogen and phosphorus minimally affect DSE colonisation. The difference in AMF and DSE colonisation patterns demonstrates a distinction in how different fungal symbionts are affected by abiotic factors. Both nitrogen and phosphorus are important drivers of colonisation dynamics of AMF. The results indicate the potential for disparate controls of AMF and DSE root associations.

Climate change and overgrazing significantly constrain the sustainability of meadow land and vegetation in the livestock industry on the Tibetan-Plateau ecosystem. In context of climate change mitigation, grassland soil C sequestration and forage sustainability, it is important to understand how manure regimes influence SOC stability, grassland soil, forage structure and nutritional quality. However, the responses of SOC fractions, soil and forage structure and quality to the influence of manure gradient practices remain unclear, particularly at Tianzhu belt, and require further investigation. A field study was undertaken to evaluate the soil bulk density, aggregate fractions and dynamics in SOC concentration, permanganate oxidizable SOC fractions, SOC stabilization and soil nutrients at the soil aggregate level under manure gradient practices. Moreover, the forage biodiversity, aboveground biomass and nutritional quality of alpine meadow plant communities were also explored. Four treatments, i.e., control (CK), sole sheep manure (SM), cow dung alone (CD) and a mixture of sheep manure and cow dung (SMCD) under five input rates, i.e., 0.54, 1.08, 1.62, 2.16 and 2.70 kg m-2, were employed under randomized complete block design with four replications. Our analysis confirmed the maximum soil bulk density (BD) (0.80 ± 0.05 g cm-3) and micro-aggregate fraction (45.27 ± 0.77%) under CK, whilst the maximum macro-aggregate fraction (40.12 ± 0.54%) was documented under 2.70 kg m-2 of SMCD. The SOC, very-labile C fraction (Cfrac1), labile C fraction (Cfrac2) and non-labile/recalcitrant C fraction (Cfrac4) increased with manure input levels, being the highest in 2.16 kg m-2 and 2.70 kg m-2 applications of sole SM and the integration of 50% SM and 50% CD (SMCD), whereas the less-labile fraction (Cfrac3) was highest under CK across aggregate fractions. However, manures under varying gradients improved SOC pools and stabilization for both macro- and micro-aggregates. A negative response of the carbon management index (CMI) in macro-aggregates was observed, whilst CMI in the micro-aggregate fraction depicted a positive response to manure addition with input rates, being the maximum under sole SM addition averaged across gradients. Higher SOC pools and CMI under the SM, CD and SMCD might be owing to the higher level of soil organic matter inputs under higher doses of manures. Moreover, the highest accumulation of soil nutrients,, for instance, TN, AN, TP, AP, TK, AK, DTPA extractable Zn, Cu, Fe and Mn, was recorded in SM, CD and SMCD under varying gradients over CK at both aggregate fractions. More nutrient accumulation was found in macro-aggregates over micro-aggregates, which might be credited to the physical protection of macro-aggregates. Overall, manure addition under varying input rates improved the plant community structure and enhanced meadow yield, plant community diversity and nutritional quality more than CK. Therefore, alpine meadows should be managed sustainably via the adoption of sole SM practice under a 2.16 kg m-2 input rate for the ecological utilization of the meadow ecosystem. The results of this study deliver an innovative perspective in understanding the response of alpine meadows' SOC pools, SOC stabilization and nutrients at the aggregate level, as well as vegetation structure, productivity and forage nutritional quality to manure input rate practices. Moreover, this research offers valuable information for ensuring climate change mitigation and the clean production of alpine meadows in the Qinghai-Tibetan Plateau area of China.