Influence of BHC and fenvalerate on mineralization and availability of some plant nutrients in soil.
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Carbon↗
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Evaluation and refinement of a continuous seed germination and early seedling growth test for the use in the ecotoxicological assessment of soils.
Four higher plant species (Avena sativa L., oat; Lepidium sativum L., cress; Brassica rapa Metzg., turnip; and Phaseolus vulgaris L., bush bean) and 15 soils including five mineral oil-contaminated soils were tested to assess a soil-based continuous seed germination and early seedling growth bioassay. Seed germination was recorded and the shoot biomass of 14-day seedlings measured. An automatic self-watering system was compared with the daily hand watering. Results obtained from this study show that the self-watering system had minor effects on both seed germination and early seedling growth, and that soil nutrient status rather than soil texture significantly affected both seedling emergence and shoot biomass. Proportional dilution of suspicious samples from primary tests with an appropriate control soil is recommended for secondary tests. Shoot biomass is a more sensitive measurement endpoint than seed germination. Bush bean should not be recommended for use due to its low sensitivity to mineral oil and poor germination in soil.
Biomass↗
The nonmycorrhizal root--a strategy for survival in nutrient-impoverished soils.
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Adaptation, Physiological↗
[Effect of atmospheric CO2 enrichment on soil microbes and related factors].
This paper summarized the effects of atmospheric CO2 enrichment on soil microbes and their related factors, including soil microflora, soil respiration, soil microbial biomass, and higher plant-microbe symbiosis. The factors related to soil microbic activity such as litter decomposition, root exudates, soil nutrient availability, nutrient use efficiency and soil fauna were also affected by the CO2 enrichment.
Air↗
[Suitability of low-valent P-compounds as nutrients for soil micro-organisms (author's transl)].
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Aspergillus↗
Responses of Picea, Pinus and Pseudotsuga roots to heterogeneous nutrient distribution in soil.
The spatial distribution of plant-available mineral nutrients in forest soils is often highly heterogeneous. To test the hypothesis that local nutrient enrichment of soil leads to increased root proliferation in the nutrient-rich soil zone, we studied the effects of nutrient enrichment on the growth and nutrient concentrations of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) roots. Three-year-old seedlings were grown for 9 months in split-root containers filled with nutrient-poor forest mineral soil, with one side supplemented with additional mineral nutrients. Root dry weight and root length in Scots pine and Norway spruce were increased in the nutrient-supplemented soil compared with the nonsupplemented side, whereas root growth in Douglas-fir was unaffected by nutrient enrichment. Of the three species examined, Norway spruce exhibited the highest root and shoot growth and the highest nutrient demand. Specific root length (m g(-1)) and the number of root tips per unit root length were not affected by local nutrient addition in any of the species. Despite increased root growth in Norway spruce and Scots pine in nutrient-supplemented soil, their root systems contained similar nutrient concentrations on both sides of the split-root container. Thus, coniferous trees may respond to local nutrient supply by increased root proliferation, but the response varies depending on the species, and may only occur when trees are nutrient deficient. As a response to local nutrient enrichment, increases in root dry matter or root length may be better indicators of pre-existing nutrient deficiencies in conifers than increases in root nutrient concentrations.
Journal Article↗
[Study on nutritional characteristics of Pogostemon cablin].
This paper studied the soil nutrient status, the nutrient contents of Pogostemon cablin nutritional organs, the relationship between soil available nutrients and nutritional elements contents of Pogostemon cablin, the nutritional elements contents of leaves and their proportions in different growth periods of the plant, the reuse of the nutritional elements of leaves in Pogostemon cablin base of Guangdong Institute of Chinese Medicine. The results provided scientific basis for the research on the fertilization and special fertilizers of Pogostemon cablin.
Fertilizers↗
Role of rainfall intensity and hydrology in nutrient transport via surface runoff.
Loss of soil nutrients in runoff accelerates eutrophication of surface waters. This study evaluated P and N in surface runoff in relation to rainfall intensity and hydrology for two soils along a single hillslope. Experiments were initiated on 1- by 2-m plots at foot-slope (6%) and mid-slope (30%) positions within an alfalfa (Medicago sativa L.)-orchardgrass (Dactylis glomerata L.) field. Rain simulations (2.9 and 7.0 cm h(-1)) were conducted under wet (spring) and dry (late-summer) conditions. Elevated, antecedent soil moisture at the foot-slope during the spring resulted in less rain required to generate runoff and greater runoff volumes, compared with runoff from the well-drained mid-slope in spring and at both landscape positions in late summer. Phosphorus in runoff was primarily in dissolved reactive form (DRP averaged 71% of total P), with DRP concentrations from the two soils corresponding with soil test P levels. Nitrogen in runoff was mainly nitrate (NO3-N averaged 77% of total N). Site hydrology, not chemistry, was primarily responsible for variations in mass N and P losses with landscape position. Larger runoff volumes from the foot-slope produced higher losses of total P (0.08 kg ha(-1)) and N (1.35 kg ha(-1)) than did runoff from the mid-slope (0.05 total P kg ha(-1); 0.48 kg N ha(-1)), particularly under wet, spring-time conditions. Nutrient losses were significantly greater under the high intensity rainfall due to larger runoff volumes. Results affirm the critical source area concept for both N and P: both nutrient availability and hydrology in combination control nutrient loss.
Environmental Monitoring↗
[Minimum application rates for high-yielding rice production system in the Taihu Lake region as a field measure for controlling N and P agricultural loading].
Excess application with the poor efficiency of fertilizers is one of the major problems confronting the sustainable agricultural development. Whereas, loss of N and P nutrients from farmlands to surface waters is considered as one of the major sources inducing eutrophication. In order to work out a minimum fertilizer application rate for both keeping conventional yield and reducing nutrient loading of non point source pollution, an experiment of formulated fertilization scheme on rice at different rates and nutrient ratios by incorporating the soil supply potential was conducted in a paddy soil Wunitu in Kunshan City, Suzhou. The soil nutrient can supply a yield at 6.75 t/hm2 at least for one cropping season. Among the fertilization treatments, a maximum yield of 9.79 t/hm2 was obtained at fertilization (N + P) rate of 300 kg/hm2kg N and P at a ratio of N to P being 3:2 or 1:1. However, with much lower fertilization (N + P) rate at 240 kg/hm2 with the same ratio a high yield of 9.69 t/hm2 was reached. The fertilizer efficiency of the later was 3 times as that of the former rate. Thus, a economical and environmentally sound mode of fertilization in such paddy soils as total N and P 240 kg/hm2, with N:P:Kratio being 3:2:0 or 1:1:0 was developed. Further study would be directed to a innovation of combination of reducing fertilization rate with rotated fertilization for alternative crops.
Crops, Agricultural↗
[Effect of forest litter on microenvironment conditions of forestland].
Litter is a very important component in forest ecosystem. This paper made a systematic review on the previous studies about the effects of litter on forestland microsites. Litter significantly reduced the light on the soil surface of forestlands, and the light transmittance was varied with the type, water content and weight of litter. The spectral composition of the light was dramatically shifted to longer wavelengths after transmitted through forest capony, especially through moist litter leaves, intact forest litter, and even the thinner soil layer, which greatly reduced the R/FR ratio and PPFD (photosynthetic photo flux density) beneath litter and surface soil (2 mm depth), and resulted in a stronginhibitory effect on the germination of photoblastic seeds, and on the growth of seedling and sapling. It was the reason why the appearance of massive numbers of pioneer plants and their successful establishment required relatively large gaps of the forest canopy. Many references concerned the effects of litter on soil nutrient cycling and water and soil conservation. The previous studies indicated that litter could create a moist micro-site above soil, and make soil more moist and fertile. Furthermore, litter could also increase the numbers of arthropods such as Carabidae adults and larvae, crickets, millipedes, spiders, ants and others. An increase in the activity of herbivorous arthropods might produce the negative effects on the establishment of individual seedlings. Although the mechanical barrier of litter was neglected in the paper, litter might act as a mechanical impediment to the emergence of the seedlings of pioneer species with small seeds. The effects of litter on micro-sites were of complexity because it varied greatly with the density, age, structure and species composition of the canopy, sunfleck frequency, presence of gaps, as well as litter thickness, moisture, and species composition, and also with climate and topography factors. The effects of litter were comprehensive, including positive and negative effects on seed germination and seedling growth. Each effect of litter on regeneration was dependent on species physiology, litter physical properties and environmental conditions. Therefore, it should be encouraged to integrate the physical properties (such as changing light, temperature and moisture) of litter with the physiological ecology (including seed, germination and growth natures) of species, and with environment (vegeneration, climate and topography propersities) on the basis of combination of regeneration patterns of litter, understory and gap scales.
Animals↗
Functional significance of dauciform roots: exudation of carboxylates and acid phosphatase under phosphorus deficiency in Caustis blakei (Cyperaceae).
Caustis blakei produces an intriguing morphological adaptation by inducing dauciform roots in response to phosphorus (P) deficiency. We tested the hypothesis that these hairy, swollen lateral roots play a similar role to cluster roots in the exudation of organic chelators and ectoenzymes known to aid the chemical mobilization of sparingly available soil nutrients, such as P. Dauciform-root development and exudate composition (carboxylates and acid phosphatase activity) were analysed in C. blakei plants grown in nutrient solution under P-starved conditions. The distribution of dauciform roots in the field was determined in relation to soil profile depth and matrix. The percentage of dauciform roots of the entire root mass was greatest at the lowest P concentration ([P]) in solution, and was suppressed with increasing solution [P], while in the field dauciform roots were predominantely located in the upper soil horizons, and decreased with increasing soil depth. Citrate was the major carboxylate released in an exudative burst from mature dauciform roots, which also produced elevated levels of acid phosphatase activity. Malonate was the dominant internal carboxylate present, with the highest concentration in young dauciform roots. The high concentration of carboxylates and phosphatases released from dauciform roots, combined with their prolific distribution in the organic surface layer of nutrient-impoverished soils, provides an ecophysiological advantage for enhancing nutrient acquisition.
Acid Phosphatase↗
Raising groundwater differentially affects mineralization and plant species abundance in dune slacks.
The experience with restoring high water levels (i.e., rewetting) within restoration ecology is limited, and information on changes in soil nutrient supply is scarce. A reduction in nutrient supply is needed to restore the desired oligotrophic vegetation. We determined the effects of restoration of high water levels on decomposition and net carbon (C), nitrogen (N), and phosphorus (P) mineralization rates in wet dune slacks and its consequences for the relative abundance of eutrophic vs. oligotrophic species in the vegetation. This was done by analyzing these variables for valleys that experienced a large groundwater rise vs. valleys that had a small groundwater rise but the same current water level. In addition, the influences of underlying factors (waterlogging, vegetation dieback, and soil dynamics prior to groundwater rise) were separated in a transplantation experiment. Short-term effects of large groundwater rise were a massive dieback of vegetation, increased thickness of the fermentation layer, increased microbial decomposition activity, increased C mineralization, and decreased net N mineralization. Net P mineralization was not affected. The relative abundance of oligotrophic vs. eutrophic species was greater at large groundwater rise. Changes in decomposition and mineralization by large groundwater rise were, however, not caused by the vegetation dieback, but due to previous soil conditions. Soils experiencing waterlogged conditions for 3-4 years or more prior to large groundwater rise had lower C and higher net N mineralization rates at waterlogged conditions than soils that had experienced aerobic conditions, presumably due to differences in labile soil C contents. Contrary to expectations induced by previously determined nutrient pulses and measured vegetation dieback, large groundwater rise resulted in lower soil nutrient supply rates and more oligotrophic vegetation. If these trends continue on the longer term, restoration of high water levels may be effective in restoration ecology to establish oligotrophic, wet vegetation in dune slacks.
Carbon↗
Persistent antimicrobial resistance during soil remediation driven by residual heavy metal co-selection.
Remediation of heavy metal-contaminated soil is a global priority, particularly as reclaimed land increasingly intersects with urban development and human exposure. However, the ecological consequences of soil remediation, especially its impact on antimicrobial resistance (AMR) as a global health threat, have remained poorly understood. Here, we combined single-cell Raman-D₂O probing with genome-resolved metagenomics to monitor the dynamics of phenotypic and genotypic resistance to metals and antibiotics during a 120-day remediation of soils with three contamination levels from a lead-zinc smelting site. Although chemical remediation substantially reduced bioavailable metals (by 42%-65%), AMR was not diminished. Instead, both phenotypic activity and gene abundance of metal- and antibiotic-resistant microorganisms increased, resulting in a two- to three-fold increase in AMR-associated health risks. Among 76 metagenome assembled genomes (MAGs) from phenotypic resistance communities, all Cd resistance-associated MAGs harbored multidrug resistance genes, half of which were colocalized with metal resistance determinants, and their prevalence continued to rise with remediation. These findings reveal that although remediation alleviates acute metal toxicity, residual low-concentration bioavailable metals sustain evolutionary selection for resistance, highlighting a disconnect between chemical recovery and biological safety. Moreover, the improved soil nutrient and physiochemical properties of remediated soils further promoted the proliferation of antibiotic-resistant bacteria. This study offers new ecological insights into the unintended consequences of anthropogenic interventions, underscoring the need to integrate biological safety into soil health and safety assessments.
Soil Microbiology↗
Biotests and biosensors in ecotoxicological risk assessment of field soils polluted with zinc, lead, and cadmium.
The combined chemical and ecotoxicological hazard evaluation study was conducted on 60 smelter-influenced soils containing 1 to 13, 50 to 653, and 100 to 1,198 mg/kg of Cd, Pb, and Zn, respectively. For these soils (liquid-to-soil ratio = 10), water extractability of Zn, Cd, and Pb was less than 0.19% (median values). Acetic acid (0.11 M) extracted 23, 9.7, and 0.7% of Cd, Zn, and Pb, respectively. Although heavy metal concentrations in the studied soils were high, the toxic effects of water extracts were observed only in few samples and in few biotests (algae Selenastrum capricornutum and metal detector assay). For most of the aquatic test organisms (e.g., crustaceans, photobacteria), the bioavailable concentrations of metals in soil-water extracts were either subtoxic, or the adverse effects were compensated by soil nutrients, etc. However, analysis of the soils with recombinant Cd sensor Bacillus subtilis (pTOO24) showed that about 65% of these apparently subtoxic samples contained bioavailable Cd when analyzed in the suspension assay (detection limit 1.5 mg Cd/kg soil), indicating the desorption of Cd induced by direct contact of bacteria with soil particles. The median bioavailable fraction of Cd (1%) was 23-fold lower than the fraction extracted by acetic acid. The Pb-Cd sensor Staphylococcus aureus (pT0024) detected bioavailable Pb only in the suspensions of five of the most lead-polluted soils (>417 mg Pb/kg): the median bioavailability of Pb was 0.42%. Consequently, the hazard assessment relying on total metal levels in soils should be revised by critical comparison with data obtained from bioassays. Development and use of biosensors (excellent tools for mechanistic studies and signaling hazard already at subtoxic level) should be encouraged.
Bacillus subtilis↗
[Research advance in catalytic kinetics of soil hydrolase].
Soil hydrolase is a group of soil enzymes that participated in many important biochemical reactions in soil and correlated with soil nutrient transformations. The catalytic kinetics of soil hydrolase can illuminate the characteristics of its catalytic processes, its substantial properties, and its response to environmental changes. This paper summarized the kinds of soil hydrolase and the main soil biochemical reactions they catalyzed, and summed up the research advances of their catalytic kinetics in soil. Some advices were proposed in understanding their action mechanism and in regulating their catalytic processes.
Catalysis↗
Direct uptake of soil nitrogen by mosses.
Mosses are one of the most diverse and widespread groups of plants and often form the dominant vegetation in montane, boreal and arctic ecosystems. However, unlike higher plants, mosses lack developed root and vascular systems, which is thought to limit their access to soil nutrients. Here, we test the ability of two physiologically and taxonomically distinct moss species to take up soil- and wet deposition-derived nitrogen (N) in natural intact turfs using stable isotopic techniques (15N). Both species exhibited increased concentrations of shoot 15N when exposed to either soil- or wet deposition-derived 15N, demonstrating conclusively and for the first time, that mosses derive N from the soil. Given the broad physiological and taxonomic differences between these moss species, we suggest soil N uptake may be common among mosses, although further studies are required to test this prediction. Soil N uptake by moss species may allow them to compete for soil N in a wide range of ecosystems. Moreover, since many terrestrial ecosystems are N limited, soil N uptake by mosses may have implications for plant community structure and nutrient cycling. Finally, soil N uptake may place some moss species at greater risk from N pollution than previously appreciated.
Bryophyta↗
Effect of nitrogen and phosphorus addition on phenanthrene biodegradation in four soils.
Phenanthrene mineralization rates were found to vary widely among four soils; differences in soil nutrient levels was one hypothesis to explain this variation. To test this hypothesis, phenanthrene mineralization rates were measured in these soils with, and without, added nitrogen and phosphorus. Mineralization rates either remained unchanged or were depressed by the addition of nitrogen and phosphorus. Phenanthrene degradation rates remained unchanged in the soil which had the highest indigenous levels of nitrogen and phosphorus and which showed the largest increase in phosphorus levels after nutrients were added. The soils in which degradation rates were depressed had lower initial phosphorus concentrations and showed much smaller or no measurable increase in phosphorus levels after nutrients were added to the soils. To understand the response of phenanthrene degradation rates to added nitrogen and phosphorus, it may be necessary to consider the bioavailability of added nutrients and nutrient induced changes in microbial metabolism and ecology.
Biodegradation, Environmental↗