Nitrogen removal from wastewater in vertical flow constructed wetlands containing LWA/gravel layers and reed vegetation

The influence of light weight aggregates made of fly ash from sewage sludge thermal treatment (FASSTT LWA) on the nitrogen removal efficiency from artificial wastewater in constructed wetlands (CW) with vertical flow reed bed was investigated. Thirty lysimeters with six different double-layer bed constructions (upper layer of FASSTT LWA with thicknesses of: 0 cm, 12 cm, 25 cm, 50 cm, and 100 cm of the total depth of the lysimeter, above a lower gravel layer), either with or without reed plants were operated with wastewater hydraulic loading rate of 4.67 mm/d. During a six-month experiment, high efficiency of ammonia removal was observed. The influence of FASSTT LWA as a bed material and the presence of reed on CW treatment efficiency was determined. The highest total nitrogen removal efficiency, 59.5%, was obtained in the CW with double-layer lysimeters consisting of 25% FASSTT LWA (upper layer), and 75% gravel (lower layer), and planted with reed.     

Effects of the halocline on water quality and phytoplankton composition in a shallow brackish lake (Lake Obuchi, Japan)

The relationships of the halocline to both water quality and phytoplankton composition in Lake Obuchi, a shallow brackish lake in northern Japan, were investigated from April 2001 to December 2004. The halocline in this lake became stronger in summer (July–September, mean maximum density gradient 4.3–5.8 ρ_tm⁻¹) but weaker in spring, fall, and winter (1.9–3.3 ρ_tm⁻¹). Although the difference in water quality between the upper and lower layers separated by the halocline was high in summer, nutrients (PO₄³⁻-P and NH₄⁺-N) were eluted from the bottom sediment as levels of dissolved oxygen decreased in the bottom layer because of the strong stratification caused by the halocline formed over the long term. Moreover, phytoplankton taxa composition also differed between the upper and lower layers in summer, but was similar in other seasons. The dominant phytoplankton taxa in the upper layer in summer were Skeletonema costatum and Cyclotella spp., whereas in the lower layer, Gymnodinium spp. (Dinophyceae) and Chlorophyceae, which prefer eutrophic and low dissolved oxygen conditions, dominated. This suggests that the halocline was related to differentiations in both water quality and ecosystem components between the upper and lower layers in the brackish lake water.     

Replica immunoelectron microscopic study of the upper surface layer in rat mandibular condylar cartilage by a quick-freezing method

A quick-freezing and deep-etching method in combination with replica immunoelectron microscopy was applied for examining localization of hyaluronic acid and fibronectin on the upper surface layer of rat mandibular condylar cartilage. Rat temporomandibular joints were dissected with articular disks in order to leave the articular cartilage surface intact. The disks were slightly cut with razor blades for exposing the condylar articular cartilage surface. They were quickly frozen with the isopentane-propane cryogen (–193°C) and prepared for freeze-fracturing and deep-etching replica membranes. They were additionally treated with 5% SDS and 0.5% collagenase to keep some antigens attached on the replica membranes. After such a treatment, a routine immunogold method was applied for clarifying the localization of hyaluronic acid and fibronectin in the upper surface layer. Small immunogold particles for hyaluronic acid were mainly localized around upper filamentous networks covered with amorphous materials, but large immunogold ones for fibronectin were localized on deep thicker fibrils. We have revealed the native architecture of the upper surface layer of mandibular condylar cartilage on the replica membranes and also three-dimensional localization of hyaluronic acid and fibronectin by the immunogold method.     

Impact of land use change on soil aggregate dynamics in the dry tropics

A 2‐year study was conducted to elucidate land use change (LUC) impact on the distribution of aggregate size fractions and associated carbon (C) concentration involving natural forest (NF), degraded forest (DF), cropland (CL), and biofuel plantation (JP, Jatropha plantation) in the dry tropical region of India across the soil profile (0–10, 10–20, and 20–30 cm). Across the seasons and the land uses, the proportion of macro‐ and microaggregates was maximum at upper and minimum at lower layer whereas mesoaggregates increase with depth. The trend of macro‐ and microaggregate fractions through the soil profile was NF > JP > DF > CL whereas that of mesoaggregates was CL > DF < JP > NF. Dry mean weight diameter was highest at upper layer and decreased down the depth in all the land uses and followed the trend NF > JP > DF > CL. Aggregate associated organic carbon (OC) concentration in all the fractions decreased from NF to DF, CL, or JP indicates that macroaggregate associated OC concentration was more susceptible to loss than that of meso‐ and microaggregate associated OC concentration. LUC induced decline in macroaggregate associated OC stock and increase in meso‐ and microaggregate associated OC stock; indicated redistribution of OC stock among aggregate fractions. It may be concluded that JP in dry tropics can be an efficient strategy for rehabilitation of degraded land as it improves aggregate structure and stability in the whole profile and aggregate associated OC stock in upper layer of soil.     

Effect of Soil Texture and Moisture on the Activity of Entomopathogenic Nematodes Against Female Boophilus annulatus Ticks

Soil texture, chemistry and moisture have a profound effect upon the activity and persistence of entomopathogenic nematodes (EPNs). Whereas nematodes’ natural habitat is within the soil, ticks and other arthropod pests prefer to stay on the soil surface and under stones or leaf litter; they spend much of their life cycle in the humid environment of the soil upper layer, therefore consideration of the effect of the soil environment on nematode activity is a pre-requisite for the sucessful use of EPNs against arthropod pests. In the present study we investigated the effects of soil type, and humidity on various nematode strains and on their effectiveness against ticks. Many infective juveniles (IJs) of Steinernema carpocapsae and S. riobrave were found in the uppermost soil layer whereas the heterorhabditid strains were almost absent from the upper 6 cm of the soil profile. The IJs of S. feltiae, and the S. carpocapsae strain S-20, exhibited an intermediate behavior. It was found that the activity of IJs of S. carpocapsae in the soil upper layer (1 cm depth) was strongly affected by soil type: the greatest number of IJs were recorded from sandy loam soil; less were found in the lighter soils – ‘Marine sand’ and ‘Calcareous sandstone’ – and only very few were recovered from heavy soils. Strikingly, even when the soil moisture was low and the number of nematodes found in the upper layer correspondingly low, tick mortality remained high. The results demonstrate: (a) the possible use of the nematodes as an anti-tick agent; (b) the importance of knowing the exact interaction of nematodes with the immediate environment of the pest, in order to optimize the pest-control activity of the nematode.     

Biomass,production and activity of bacteria in the Black Sea,with special reference to chemosynthesis and the sulfur cycle

Abundance, morphological composition, vertical distribution, production and activity of total bacterioplankton and its specific groups in the Black Sea were investigated in August–September 1989. The total bacterioplankton was highest in the upper mixed layer (0.7–1 × 10⁶ cells ml^–1), corresponding to that in mesotrophic basins. In the N-E shallow part of the sea it attained 3 × 10⁶. Below the thermocline (50–100 m) the total number of bacteria decreased to 0.2–0.4 × 10⁶ ml^–1. In the redox gradient zone (zone of O₂-H₂S interface), it increased again. In deep anoxic waters the bacterioplankton, numbering 0.15–0.2 × 10⁶ ml^–1, was functionally inactive. Its biomass was 12–40 mg C m^–3 in the upper mixed layer, 5–10 mg C m^–3 in the intermediate cold layer (40–100 m depth), and 10–20 mg C^–3 in the redox zone. Maximum production rates occurred in the upper mixed layer (8–20 mg C^–3 d^–1) and in the redox-zone, 80–90% of it was due to chemosynthesis of thiobacilli. Below 200 m, microbial production decreased to about zero in the anoxic zone. Maximum activity of heterotrophic bacteria was recorded in the upper mixed layer, while thiobacilli and methaneoxidezing bacteria were most active in the redox-zone. Here, the maximum rates of H₂S and of thiosulfate oxidation, as well as maximum sulfate reduction were recorded. Chemical oxidation of H₂S was dominant. These results are discussed with respect to the present ecological situation of the Black Sea.     

Comparison between the soil seed banks of a burnt and an unburnt Quercus pyrenaica Willd. forest

Soil samples from burnt and unburnt sites dominated by Quercus pyrenaica Willd. forest in León province (NW Spain) were collected, separated into an upper layer (0–2 cm depth) from a lower layer (2–5 cm), put in a greenhouse, and seeds allowed to germinate.A total of 670 identified seedlings comprising 56 species and belonging to 24 families were recorded. Most seedling were herbaceous perennials (hemicryptophytes: 59%), followed by annuals (therophytes: 23%). Many species that germinated from buried seeds were not observed as plants at any site, and came from exogenous communities. The principal means of seed dissemination were anemochory (45%) and autochory (23%).The number of species as well as seedlings was not significantly different between soils from the burnt and unburnt sites, but seedlings were more numerous in samples from the unburnt sites, as the number of seedlings was always highest in the upper soil layer. Germination behaviour of four particular species was characterized.Seedlings from the seed bank temporarily were found in the early stages of recovery of the burnt Quercus pyrenaica forests.     

Glyphosate bioavailability in soil

Biodegradation of glyphosate in sod-podzol soil by both the indigenous micro flora and the introduced strain Ochrobactrum anthropi GPK 3 was studied with respect to its sorption and mobility. The experiments were carried out in columns simulating the vertical soil profile. Soil samples studied were taken from soil horizons 0–10, 10–20, and 20–30 cm deep. It was found out that the most of the herbicide (up to 84%) was adsorbed by soil during the first 24 h; the rest (16%) remained in the soluble fraction. The adsorbed glyphosate was completely extractable by alkali. No irreversible binding of glyphosate was observed. By the end of the experiment (21st day), glyphosate was only found in extractable fractions. The comparison of the effect of the introduced O. anthropi GPK 3 and indigenous microbial community on the total toxicant content (both soluble and absorbed) in the upper 10 cm soil layer showed its reduction by 42% (21 mg/kg soil) and 10–12% (5 mg/kg soil), respectively. Simultaneously, 14–18% glyphosate moved to a lower 10–20 cm layer. Watering (that simulated rainfall) resulted in a 20% increase of its content at this depth; 6–8% of herbicide was further washed down to the 20–30 cm layer. The glyphosate mobility down the soil profile reduced its density in the upper layer, where it was available for biodegradation, and resulted in its concentration in lower horizons characterized by the absence (or low level) of biodegradative processes. It was shown for the first time how the herbicide biodegradation in soil can be increased manifold by introduction of the selected strain O. anthropi GPK 3.     

Clipperton, a possible future for atoll lagoons

Closure of the Clipperton Island atoll (10°17′ N 109°13′ W), now a meromictic lake, is estimated to have occurred between 1839 and 1849. It was still closed in 2005. Brackish waters in the upper layer (0–10 m) were oxygenated, while saline waters in the deep layer (>20 m) were anoxic. Allowing for the methodological difficulties of earlier measurements, the physical characteristics of the lagoon did not seem to have changed significantly since the last expedition (1980). The intermediate layer between brackish and saline waters was characterized by a strong density gradient and a temperature inversion of up to 1.6°C. Microbial activity, water exchange between the deep layer and surrounding oceanic waters and the geothermal flux hypothesis are discussed. The low DIN and SRP concentrations observed in the upper layer, despite high nutrient input by seabird droppings, reflect the high nutrient uptake by primary producers as attested by the elevated overall gross primary production (6.6 g C m⁻² day⁻¹), and high suspended photosynthetic biomass (2.23 ± 0.23 μg Chl a l⁻¹) and production (263 ± 27 μg C l⁻¹ day⁻¹). Phytoplankton composition changed in 67 years with the advent of new taxa and the disappearance of previously recorded species. The freshwater phytoplanktonic community comprised 43 taxa: 37 newly identified during the expedition and 6 previously noted; 16 species previously found were not seen in 2005. The closure of the lagoon, combined with the positive precipitation–evaporation budget characteristic of the region, has induced drastic changes in lagoon functioning compared with other closed atolls.     

Role of avoidance behavior in the response of Folsomia candida to above‐freezing cooling temperatures

Although avoidance behavior is thought to be one of the major strategies for arthropods to cope with cold, there is a general lack of data supporting its use. This study tested the suggestion that Collembola migrate deeper into the soil to avoid cooling temperatures during the transition from summer to winter. We released mature hemi‐edaphic Folsomia candida Willem (Collembola: Isotomidae) in large (5 301 cm³) and small (306 cm³) soil microcosms exposed to ambient temperatures ranging between 5 and 20 °C. Springtails released in the large microcosms for periods of 2, 3, and 4 weeks dispersed throughout the soil column but remained more abundant in the upper third layer of the soil column whether exposed to weekly decreasing temperatures or a constant ambient temperature of 20 °C. Both small (juvenile) and large (mature) springtails exposed to cooling were more abundant in the upper third than in the middle or lower third of the soil columns after 2, 3, or 4 weeks. Groups of F. candida released in small microcosms provided with a positive soil temperature gradient displayed the same vertical distribution, with 90% of individuals clustered in the top 4.5 cm of the 15‐cm column whether exposed to air temperatures of 5, 10, 15, or 20 °C. Results from the two types of microcosms demonstrated that the vertical distribution of springtails remains strongly biased to the upper soil layer regardless of the temperature of their environment and whether the temperature in the soil column was uniform or graduated. This supports our prediction that hemi‐edaphic species such as F. candida do not relocate to warmer deeper soil layers, but tend to remain in the surface soil layer where they can acclimate to the cooling temperature.     

Unique ethylene-regulated touch responses of Arabidopsis thaliana roots to physical hardness

Although touch responses of plant roots are an important adaptive behavior, the molecular mechanism remains unclear. We have developed a bioassay for measuring root-bending responses to physical hardness in Arabidopsis thaliana seedlings. Our test requires a two-layer solid medium. Primary roots growing downward through an upper layer of 0.3% phytagel either penetrate the lower layer or bend along an interface between the upper and lower layers with different concentrations (0.2–0.5%, corresponding to 1.57–6.79 gw mm⁻² in hardness). In proportion to increasing hardness of the lower layer, we found that the percentage of bending roots increased and ethylene production decreased, suggesting an inverse relationship between the root-bending response and ethylene production. Studies with ethylene biosynthesis modulators and mutants also suggested that bending and non-bending responses of roots to medium hardness depend, respectively, on decreased and increased ethylene biosynthesis. In addition, the degrees of root-tip softening and differential root-cell growth, both possible factors determining root-bending response, were enhanced and attenuated by decreased and increased amounts of ethylene, respectively—also in bending roots and non-bending roots. Our findings indicate that ethylene regulates root touch responses, probably through a combination of root-tip softening (or hardening) and differential root-cell growth.     

The effect of water turbidity on the near-surface water temperature of larval habitats of the malaria mosquito <Emphasis Type="Italic">Anopheles gambiae</Emphasis>

Water temperature is an important determinant in many aquatic biological processes, including the growth and development of malaria mosquito (Anopheles arabiensis and A. gambiae) immatures. Water turbidity affects water temperature, as suspended particles in a water column absorb and scatter sunlight and hence determine the extinction of solar radiation. To get a better understanding of the relationship between water turbidity and water temperature, a series of semi-natural larval habitats (diameter 0.32 m, water depth 0.16 m) with increasing water turbidity was created. Here we show that at midday (1300 hours) the upper water layer (thickness of 10 mm) of the water pool with the highest turbidity was on average 2.8°C warmer than the same layer of the clearest water pool. Suspended soil particles increase the water temperature and furthermore change the temperature dynamics of small water collections during daytime, exposing malaria mosquito larvae, which live in the top water layer, longer to higher temperatures.     

Preparation and Characterization of Electrospun PLCL/Poloxamer Nanofibers and Dextran/Gelatin Hydrogels for Skin Tissue Engineering

In this study, two different biomaterials were fabricated and their potential use as a bilayer scaffold for skin tissue engineering applications was assessed. The upper layer biomaterial was a Poly(ε-caprolactone-co-lactide)/Poloxamer (PLCL/Poloxamer) nanofiber membrane fabricated using electrospinning technology. The PLCL/Poloxamer nanofibers (PLCL/Poloxamer, 9/1) exhibited strong mechanical properties (stress/strain values of 9.37±0.38 MPa/187.43±10.66%) and good biocompatibility to support adipose-derived stem cells proliferation. The lower layer biomaterial was a hydrogel composed of 10% dextran and 20% gelatin without the addition of a chemical crosslinking agent. The 5/5 dextran/gelatin hydrogel displayed high swelling property, good compressive strength, capacity to present more than 3 weeks and was able to support cells proliferation. A bilayer scaffold was fabricated using these two materials by underlaying the nanofibers and casting hydrogel to mimic the structure and biological function of native skin tissue. The upper layer membrane provided mechanical support in the scaffold and the lower layer hydrogel provided adequate space to allow cells to proliferate and generate extracellular matrix. The biocompatibility of bilayer scaffold was preliminarily investigated to assess the potential cytotoxicity. The results show that cell viability had not been affected when cocultured with bilayer scaffold. As a consequence, the bilayer scaffold composed of PLCL/Poloxamer nanofibers and dextran/gelatin hydrogels is biocompatible and possesses its potentially high application prospect in the field of skin tissue engineering.     

The effect of forest fires and clearing of fire-destroyed stands on pedoecological conditions of natural forest regeneration

The study investigated the effect of forest fires and clearing of fire-destroyed stands on pedoecological conditions of forest regeneration in the Middle Ob pine forests. The study revealed that K content was elevated, pH changed to more neutral, and humus content (detritus) decreased in the upper layer of sod-podzolic soil. After clearing, the temperature of the upper soil layers increased somewhat and that of surface air increased 1.5–2 times. Air temperature was occasionally too high for pine seedlings to survive. The moisture content of the upper soil layer was up to 10% higher than on the control sites. The ecological conditions of the burned sites were generally hospitable for natural forest regeneration.     

Design of Infrared Plasma Absorber with High Refractive Index Sensitivity

Three layers of periodic artificial metamaterial sensing structure (including the upper metal particles, intermediate dielectric layer, and the lower reflective layer) with ultra-narrow band absorption were designed. The resonance characteristics and sensing properties were analyzed by the finite difference time domain (FDTD) method. The effect of localized surface plasmon resonance (LSPR) was obviously observed at the resonance wavelength of 911 nm, and it achieves nearly perfect absorption of exceeding 98% with a full width at half maximum (FWHM) of 3.5 nm. In addition, a wavelength sensitivity of 542 nm/RIU with a figure of merit (FOM) of 155 was obtained in the refractive index (RI) range from 1.00 to 1.35, which has a wide range of applications. The results show that the proposed structure has high absorption and RI sensitivity, which is suitable for bioengineering and medical detection.

     

Phase behaviour of oleanolic acid/stearyl stearate binary mixtures in bulk and at the air-water interface

The solid-liquid phase behaviour of oleanolic acid (OLA)/stearyl stearate (SS) was investigated by differential scanning calorimetry and polarizing optical microscopy. A eutectic type diagram, with the eutectic composition close to pure SS was obtained. Complementary studies by NMR, X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy were performed. A mutual influence was detected in mixtures: the low melting form of SS is favoured at low OLA molar fractions (X_OLA) and spherulitic structures appear at high X_OLA and high temperature. Additionally, H-bonding between OLA carbonyl groups increases in the presence of SS. The study of OLA/SS by the Langmuir method and Brewster angle microscopy revealed the organization at the air-water interface: OLA interacts with water in the first layer, while SS is completely segregated to the upper layer for X_OLA > 0.3, and it distributes in the first and upper layers for X_OLA < 0.3.     

Dead Sea water trajectories in the T–S space

The Dead Sea water column is composed, to a first approximation, of two water bodies: the deep waters, constituting most of the lake's volume, and a shallow upper layer a few meters thick. The temperature and salinity profiles can both be either stabilizing or destabilizing, depending on the regime and the season; if salinity is destabilizing, and double-diffusive processes are attained, the two water bodies mix at a much faster rate than normal turbulent diffusion can account for. The trajectories of the Dead Sea brines since 1977 belong to one of three different categories: upper layer under a meromictic regime, upper layer under a holomictic regime, and lower layer under a holomictic regime. The lower layer during the meromictic regime of 1979– 82 remained constant in its properties and its trajectory is thus represented by one single point. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ontogenetic vertical distribution and diel migration of the copepod Eucalanus inermis in the oxygen minimum zone off northern Chile (20-21{degrees} S)

The vertical and ontogenetic distribution, and diel verticalmigration (DVM), of Eucalanus inermis in relation to the strongvertical gradient in oxygen concentration associated with anintense oxygen minimum zone (OMZ) were studied at a coastalarea off northern Chile (20–21° S). A close relationshipbetween the abundance of the whole copepod population and lowoxygen waters was found, with most developmental stages remainingnear the base of the oxycline (30–80 m) and within theupper zone of the OMZ (30–200 m). All stages performedDVM but not at all the stations, mainly between the 30–60and 60–200 m strata; a small fraction (<20%) appearedin the surface layer (0–30 m) mostly at night. This strategyof movement would result in a better utilization of food resourcessince the strong physical and chemical gradients at the baseof the oxycline and upper OMZ boundary might serve as a siteof particle accumulation. A secondary fluorescence peak was,in fact, found at all the stations, coinciding with minimaldissolved oxygen (DO, <1 mL O₂ L^–1) at the base ofthe oxycline or in the upper OMZ boundary. The relevance ofthe biogeochemical flux involved in this diel migration patternwas assessed by calculating the potential active input of carbonand nitrogen from the upper layers into deeper the OMZ.     

Traits associated with improved P-uptake efficiency in CIMMYT's semidwarf spring bread wheat grown on an acid Andisol in Mexico

Phosphorus deficiency is a major yield limiting constraint in wheat cultivation on acid soils. The plant factors that influence P uptake efficiency (PUPE) are mainly associated with root characteristics. This study was conducted to analyze the genotypic differences and relationships between PUPE, root length density (RLD), colonization by vesicular arbuscular and arbuscular mycorrhizal (V)AM fungi and root excretion of phosphatases in a P-deficient Andisol in the Central Mexican Highlands. Forty-two semidwarf spring-bread-wheat (Triticum aestivumL.) genotypes from CIMMYT were grown without (−P) and with P fertilization (+P), and subsequently in subsets of 30 and 22 genotypes in replicated field trials over 2 and 3 years, respectively. Acid phosphatase activity at the root surface (APASE) was analyzed in accompanying greenhouse experiments in nutrient solution. In this environment, PUPE contributed more than P utilization efficiency, in one experiment almost completely, to the variation of grain yield among genotypes. Late-flowering genotypes were higher yielding, because the postanthesis period of wheat was extended due to the cold weather at the end of the crop cycles, and postanthesis P uptake accounted for 40–45% of total P uptake. PUPE was positively correlated with the numbers of days to anthesis (at −P r=0.57 and at +P r=0.73). The RLD in the upper soil layer (0–20 cm) of the wheat germplasm tested ranged from 0.5 to 2.4 cm cm^-3 at –P and 0.7 to 7.7 at +P. RLD was the most important root trait for improved P absorption, and it was positively genetically correlated with PUPE (at –P r=0.42 and at +P r=0.63) and the number of spikes m^-2 (at –P r=0.58 and at +P r=0.36). RLD in the upper soil layer was more important with P fertilizer application. Without P fertilization, root proliferation in the deeper soil profile secured access to residual, native P in the deeper soil layer. (V)AM-colonisation and APASE were to a lesser degree correlated with PUPE. Among genoptypes, the level of (V)AM-colonisation ranged from 14 to 32% of the RLD in the upper soil layer, and APASE from 0.5 to 1.1 nmol s^-1 plant^-1 10^-2. This revised version was published online in June 2006 with corrections to the Cover Date.     

The effect of hydraulic lift on organic matter decomposition,soil nitrogen cycling,and nitrogen acquisition by a grass species

Hydraulic lift (HL) is the passive movement of water through plant roots, driven by gradients in water potential. The greater soil–water availability resulting from HL may in principle lead to higher plant nutrient uptake, but the evidence for this hypothesis is not universally supported by current experiments. We grew a grass species common in North America in two-layer pots with three treatments: (1) the lower layer watered, the upper one unwatered (HL), (2) both layers watered (W), and (3) the lower layer watered, the upper one unwatered, but with continuous light 24 h a day to limit HL (no-HL). We inserted ingrowth cores filled with enriched-nitrogen organic matter (¹⁵N-OM) in the upper layer and tested whether decomposition, mineralization and uptake of ¹⁵N were higher in plants performing HL than in plants without HL. Soils in the upper layer were significantly wetter in the HL treatment than in the no-HL treatment. Decomposition rates were similar in the W and HL treatments and lower in no-HL. On average, the concentration of NH₄ ⁺-N in ingrowth cores was highest in the W treatment, and NO₃ ⁻-N concentrations were highest in the no-HL treatment, with HL having intermediate values for both, suggesting differential mineralization of organic N among treatments. Aboveground biomass, leaf ¹⁵N contents and the ¹⁵N uptake in aboveground tissues were higher in W and HL than in no-HL, indicating higher nutrient uptake and improved N status of plants performing HL. However, there were no differences in total root nitrogen content or ¹⁵N uptake by roots, indicating that HL affected plant allocation of acquired N to photosynthetic tissues. Our evidence for the role of HL in organic matter decomposition and nutrient cycling suggests that HL could have positive effects on plant nutrient dynamics and nutrient turnover.