European wildcat populations are subdivided into five main biogeographic groups: consequences of Pleistocene climate changes or recent anthropogenic fragmentation?

Extant populations of the European wildcat are fragmented across the continent, the likely consequence of recent extirpations due to habitat loss and over‐hunting. However, their underlying phylogeographic history has never been reconstructed. For testing the hypothesis that the European wildcat survived the Ice Age fragmented in Mediterranean refuges, we assayed the genetic variation at 31 microsatellites in 668 presumptive European wildcats sampled in 15 European countries. Moreover, to evaluate the extent of subspecies/population divergence and identify eventual wild × domestic cat hybrids, we genotyped 26 African wildcats from Sardinia and North Africa and 294 random‐bred domestic cats. Results of multivariate analyses and Bayesian clustering confirmed that the European wild and the domestic cats (plus the African wildcats) belong to two well‐differentiated clusters (average Ф_ST = 0.159, R_st  = 0.392, P > 0.001; Analysis of molecular variance [AMOVA]). We identified from c. 5% to 10% cryptic hybrids in southern and central European populations. In contrast, wild‐living cats in Hungary and Scotland showed deep signatures of genetic admixture and introgression with domestic cats. The European wildcats are subdivided into five main genetic clusters (average Ф_ST = 0.103, R_st  = 0.143, P > 0.001; AMOVA) corresponding to five biogeographic groups, respectively, distributed in the Iberian Peninsula, central Europe, central Germany, Italian Peninsula and the island of Sicily, and in north‐eastern Italy and northern Balkan regions (Dinaric Alps). Approximate Bayesian Computation simulations supported late Pleistocene–early Holocene population splittings (from c. 60 k to 10 k years ago), contemporary to the last Ice Age climatic changes. These results provide evidences for wildcat Mediterranean refuges in southwestern Europe, but the evolution history of eastern wildcat populations remains to be clarified. Historical genetic subdivisions suggest conservation strategies aimed at enhancing gene flow through the restoration of ecological corridors within each biogeographic units. Concomitantly, the risk of hybridization with free‐ranging domestic cats along corridor edges should be carefully monitored.     

Solar‐induced chlorophyll fluorescence is strongly correlated with terrestrial photosynthesis for a wide variety of biomes: First global analysis based on OCO‐2 and flux tower observations

Solar‐induced chlorophyll fluorescence (SIF) has been increasingly used as a proxy for terrestrial gross primary productivity (GPP). Previous work mainly evaluated the relationship between satellite‐observed SIF and gridded GPP products both based on coarse spatial resolutions. Finer resolution SIF (1.3 km × 2.25 km) measured from the Orbiting Carbon Observatory‐2 (OCO‐2) provides the first opportunity to examine the SIF–GPP relationship at the ecosystem scale using flux tower GPP data. However, it remains unclear how strong the relationship is for each biome and whether a robust, universal relationship exists across a variety of biomes. Here we conducted the first global analysis of the relationship between OCO‐2 SIF and tower GPP for a total of 64 flux sites across the globe encompassing eight major biomes. OCO‐2 SIF showed strong correlations with tower GPP at both midday and daily timescales, with the strongest relationship observed for daily SIF at the 757 nm (R² = 0.72, p < 0.0001). Strong linear relationships between SIF and GPP were consistently found for all biomes (R² = 0.57–0.79, p < 0.0001) except evergreen broadleaf forests (R² = 0.16, p < 0.05) at the daily timescale. A higher slope was found for C₄ grasslands and croplands than for C₃ ecosystems. The generally consistent slope of the relationship among biomes suggests a nearly universal rather than biome‐specific SIF–GPP relationship, and this finding is an important distinction and simplification compared to previous results. SIF was mainly driven by absorbed photosynthetically active radiation and was also influenced by environmental stresses (temperature and water stresses) that determine photosynthetic light use efficiency. OCO‐2 SIF generally had a better performance for predicting GPP than satellite‐derived vegetation indices and a light use efficiency model. The universal SIF–GPP relationship can potentially lead to more accurate GPP estimates regionally or globally. Our findings revealed the remarkable ability of finer resolution SIF observations from OCO‐2 and other new or future missions (e.g., TROPOMI, FLEX) for estimating terrestrial photosynthesis across a wide variety of biomes and identified their potential and limitations for ecosystem functioning and carbon cycle studies.     

Prey diversity of Polistes rothneyi koreanus in different landscapes using DNA barcoding

For the present study, we investigated the prey of Polistes rothneyi koreanus, which is the most common social wasp in South Korea, and the relationship between prey diversity and vegetation cover around their nests. Prey was collected over two 6‐hr sampling from seven nests between July and mid‐August 2015 in Daegu, Gyeongsan and Gunwi in South Korea. To analyse the prey spectrum, we identified species using DNA barcodes; to analyse vegetation cover, we used the normalized difference vegetation index in a 200 m radius around the nests. A total of 338 prey samples were collected, and eight orders, 24 families, and 65 species were identified, demonstrating a much broader prey spectrum than those previously recorded for Polistes spp. Lepidoptera were the most prevalent, with 158 samples and 47 species. Nest 7, located in a rural area, had the highest numbers of samples and species per worker (5.2 and 1.9, respectively). Lepidoptera accounted for over half of the prey spectrum for all nests, and the families Noctuidae and Geometridae accounted for 60% of all Lepidoptera. Tenodera sinensis (Mantodea) and Gabala argentata (Noctuidae) were the most ubiquitous species, collected at five locations. Six species and some genera of prey are designated as pests in South Korea, indicating that P. r. koreanus also has a beneficial role in pest control. A higher vegetation cover was associated with significantly higher prey species diversity (R² = .4597, p < .1) and abundance (R² = .5986, p < .05), indicating that vegetation cover is an important factor for maintaining colonies. Therefore, the recent increase in green spaces in South Korean cities is probably a major contributor to the increased density of social wasps.     

Using field photography to study avian moult

Methods to obtain moult data from wild birds have not changed much over the last century and most studies still depend on checking museum specimens or capturing birds. Here we assess the applicability of systematic field photography for detecting and scoring moult in adult Black Skimmers Rynchops niger from southern Brazil. Moult data extracted from photographs have a high within‐ (R_GLMM = 0.98) and between‐observer repeatability (R_GLMM = 0.97) and show very good fit to current Underhill–Zucchini moult models (R² = 0.75). Photography offers the advantages of being less invasive, requiring less equipment and human effort, being feasible in areas where captures may not be possible, and causing less disturbance, so enhancing the number of sampled individuals.     

Combined analyses of kinship and FST suggest potential drivers of chaotic genetic patchiness in high gene‐flow populations

We combine kinship estimates with traditional F‐statistics to explain contemporary drivers of population genetic differentiation despite high gene flow. We investigate range‐wide population genetic structure of the California spiny (or red rock) lobster (Panulirus interruptus) and find slight, but significant global population differentiation in mtDNA (Φ_ST = 0.006, P = 0.001; D_{est_Chao} = 0.025) and seven nuclear microsatellites (F_ST = 0.004, P < 0.001; D_{est_Chao} = 0.03), despite the species’ 240‐ to 330‐day pelagic larval duration. Significant population structure does not correlate with distance between sampling locations, and pairwise F_ST between adjacent sites often exceeds that among geographically distant locations. This result would typically be interpreted as unexplainable, chaotic genetic patchiness. However, kinship levels differ significantly among sites (pseudo‐F_16,988 = 1.39, P = 0.001), and ten of 17 sample sites have significantly greater numbers of kin than expected by chance (P < 0.05). Moreover, a higher proportion of kin within sites strongly correlates with greater genetic differentiation among sites (D_{est_Chao}, R² = 0.66, P < 0.005). Sites with elevated mean kinship were geographically proximate to regions of high upwelling intensity (R² = 0.41, P = 0.0009). These results indicate that P. interruptus does not maintain a single homogenous population, despite extreme dispersal potential. Instead, these lobsters appear to either have substantial localized recruitment or maintain planktonic larval cohesiveness whereby siblings more likely settle together than disperse across sites. More broadly, our results contribute to a growing number of studies showing that low F_ST and high family structure across populations can coexist, illuminating the foundations of cryptic genetic patterns and the nature of marine dispersal.     

Using co‐occurrence network topology in assessing ecological stress in benthic macroinvertebrate communities

Ecological monitoring of streams has often focused on assessing the biotic integrity of individual benthic macroinvertebrate (BMI) communities through local measures of diversity, such as taxonomic or functional richness. However, as individual BMI communities are frequently linked by a variety of ecological processes at a regional scale, there is a need to assess biotic integrity of groups of communities at the scale of watersheds. Using 4,619 sampled communities of streambed BMIs, we investigate this question using co‐occurrence networks generated from groups of communities selected within California watersheds under different levels of stress due to upstream land use. Building on a number of arguments in theoretical ecology and network theory, we propose a framework for the assessment of the biotic integrity of watershed‐scale groupings of BMI communities using measures of their co‐occurrence network topology. We found significant correlations between stress, as described by a mean measure of upstream land use within a watershed, and topological measures of co‐occurrence networks such as network size (r = ?.81, p < 10^–4), connectance (r = .31, p < 10^–4), mean co‐occurrence strength (r = .25, p < 10^–4), degree heterogeneity (r = ?.10, p < 10^–4), and modularity (r = .11, p < 10^–4). Using these five topological measures, we constructed a linear model of biotic integrity, here a composite of taxonomic and functional diversity known as the California Stream Condition Index, of groups of BMI communities within a watershed. This model can account for 66% of among‐watershed variation in the mean biotic integrity of communities. These observations imply a role for co‐occurrence networks in assessing the current status of biotic integrity for BMI communities, as well as their potential use in assessing other ecological communities.     

Reasons for Relinquishment and Return of Domestic Cats (Felis Silvestris Catus) to Rescue Shelters in the UK

ABSTRACT

Significant numbers of cats enter rescue and re-homing facilities each year, over half of which are relinquished directly by owners. Identifying the reasons why owners decide to give up their pet is an important step in the development of education strategies to encourage retention of cats by their owners. In addition, identifying why adopting owners fail to retain their new cats is important in the refinement of homing policies. Characteristics of 6,089 cats relinquished and returned to 11 rescue facilities in the UK were recorded over a year. In addition, information was collected on the reason why owners gave up, or brought back, their pet. Sixty percent of cats and kittens entering shelters were relinquished by owners, with 19% being due to owner circumstances, such as moving to rented accommodation or changes in family circumstances. Seven percent were for behavioral reasons, and 5% because of the occurrence of allergy or asthma in owners. Returned cats were significantly more likely to be older (Mann Whitney U, Z = –9.167, p < 0.001) and neutered (Pearson χ² = 110.0, df = 2, p < 0.001) than the general relinquished population. The reasons for original relinquishment and return of owned cats were also significantly different (Pearson χ² = 84.4, df = 6, p < 0.001), with 38% of cats being returned for behavioral reasons, and 18% because of allergy or asthma. The commonest behavioral reason for both relinquishment and return was aggression between cats in the household.     

Remotely sensed C3 and C4 grass species aboveground biomass variability in response to seasonal climate and topography

Seasonal climate and topography influence C3 and C4 grass species aboveground biomass (AGB). Climate change further threatens these grasses AGB, thereby compromising their ability to provide ecosystem goods and services. This emphasises the need to monitor their AGB for well‐informed management. New‐generation sensors, with improved resolution capabilities present an opportunity to explore C3 and C4 AGB. This study therefore investigated the response of remotely sensed C3 and C4 grasses AGB to seasonal climate and topography. Overall, the spatial and temporal responses of AGB due to seasonal climate and topography were observed across the study area. For example, in March, a marked increase in C4 AGB was associated with an increase in rainfall, with the highest significant positive relationship (R² = 0.82, p < 0.005). Elevation had very significant positive relationship (R² = 0.84; p < 0.005) with C3 and highest negative (R² = ?0.77; p < 0.005) with C4 AGB. During the winter fall, AGB significantly decreased from averages of 2.592 and 1.101 kg/m² in winter (May), to 0.718 and 0.469 kg/m² in August, for C3 and C4 grasses, respectively. These findings provide a key step in monitoring rangelands and assessing management practices to boost productivity.     

Precipitation of the warmest quarter and temperature of the warmest month are key to understanding the effect of climate change on plant species diversity in Southern African savannah

In this study, we test for the key bioclimatic variables that significantly explain the current distribution of plant species richness in a southern African ecosystem as a preamble to predicting plant species richness under a changed climate. We used 54,000 records of georeferenced plant species data to calculate species richness and spatially interpolated climate data to derive nineteen bioclimatic variables. Next, we determined the key bioclimatic variables explaining variation in species richness across Zimbabwe using regression analysis. Our results show that two bioclimatic variables, that is, precipitation of the warmest quarter (R² = 0.92, P < 0.001) and temperature of the warmest month (R² = 0.67, P < 0.001) significantly explain variation in plant species richness. In addition, results of bioclimatic modelling using future climate change projections show a reduction in the current bio‐climatically suitable area that supports high plant species richness. However, in high‐altitude areas, plant richness is less sensitive to climate change while low‐altitude areas show high sensitivity. Our results have important implications to biodiversity conservation in areas sensitive to climate change; for example, high‐altitude areas are likely to continue being biodiversity hotspots, as such future conservation efforts should be concentrated in these areas.     

Emperipolesis mediated by CD8+ T cells correlates with biliary epithelia cell injury in primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune disease characterized by chronic destruction of the bile ducts. A major unanswered question regarding the pathogenesis of PBC is the precise mechanisms of small bile duct injury. Emperipolesis is one of cell‐in‐cell structures that is a potential histological hallmark associated with chronic hepatitis B. This study aimed to clarify the pathogenesis and characteristics of emperipolesis in PBC liver injury. Sixty‐six PBC patients, diagnosed by liver biopsy combined with laboratory test, were divided into early‐stage PBC (stages I and II, n = 39) and late‐stage PBC (stages III and IV, n = 27). Emperipolesis was measured in liver sections stained with haematoxylin‐eosin. The expressions of CK19, CD3, CD4, CD8, CD20, Ki67 and apoptosis of BECs were evaluated by immunohistochemistry or immunofluorescence double labelling. Emperipolesis was observed in 62.1% of patients with PBC, and BECs were predominantly host cells. The number of infiltrating CD3⁺ and CD8⁺ T cells correlated with the advancement of emperipolesis (R² = 0.318, P < .001; R² = 0.060, P < .05). The cell numbers of TUNEL‐positive BECs and double staining for CK19 and Ki67 showed a significant positive correlation with emperipolesis degree (R² = 0.236, P < .001; R² = 0.267, P < .001). We conclude that emperipolesis mediated by CD8⁺ T cells appears to be relevant to apoptosis of BEC and thus may aggravate the further injury of interlobular bile ducts.     

Melanin quantification by in vitro and in vivo analysis of near‐infrared fluorescence

Objective measurements of melanin can provide important information for differentiating melanoma from benign pigmented lesions and in assessing pigmentary diseases. Herein, we evaluate near‐infrared (NIR) fluorescence as a possible tool to quantify melanin. Various concentrations of in vitro Sepia melanin in tissue phantoms were measured with NIR fluorescence and diffuse reflectance spectroscopy. Similar optic measurements were conducted in vivo on 161 normal human skin sites. Diffuse reflectance spectroscopy was used to quantify the melanin content via Stamatas–Kollias algorithm. At physiologic concentrations, increasing in vitro melanin concentrations demonstrated higher fluorescence that was linearly correlated (R² = 0.99, p < .001). At higher concentrations, the fluorescence signal plateaued. A linear relationship was also observed with melanin content in human skin (R² = 0.59, p < .001). Comparing the fluorescence and reflectance signals with in vitro and in vivo samples, the estimated melanin concentration in human skin ranged between 0 and 1.25 mg/ml, consistent with previous quantitative studies involving invasive methods.     

Enhanced electrochemiluminescence from reduced graphene oxide–CdTe quantum dots for highly selective determination of copper ion

An electrochemiluminescence (ECL) sensor based on reduced graphene oxide–CdTe quantum dots (RGO–CdTe QDs) composites for detecting copper ion (Cu²⁺) was proposed. The ECL behaviours of the RGO–CdTe QD modified electrode were investigated with H₂O₂ as the co‐reactant. Quantitative detection of Cu²⁺ was realized as Cu²⁺ could effectively quench the ECL signal of the RGO–CdTe QDs. A wide linear range of 1.00 × 10^?14 to 1.00 × 10^?4 M (R = 0.9953) was obtained under optimized conditions, and a detection limit (S/N = 3) was achieved of as low as 3.33 × 10^?15 M. The proposed sensor also exhibited good stability and selectivity for the detection of copper ions. Finally, the analytical application of the proposed sensor was also evaluated using river water.     

Seasonal Variation in Occurrence of Pulmonary Embolism: Analysis of the Database of the Emilia‐Romagna Region,Italy

Seasonal variation in the occurrence of cardiovascular and cerebrovascular events, including pulmonary embolism (PE), has been reported; however, recent large‐scale, population‐based studies conducted in the United States did not confirm such seasonality. The aim of this large‐scale population study was to determine whether a temporal pattern in the occurrence of PE exists. The analysis considered all consecutive cases of PE in the database of all hospital admissions of the Emilia Romagna region in Italy at the Center for Health Statistics between January 1998 and December 2005. PE cases were first grouped according to season of occurrence, and the data were analyzed by the χ² test for goodness of fit. Then, inferential chronobiologic (cosinor and partial Fourier) analysis was applied to monthly data, and the best‐fitting curve for the annual variation was derived. The total sample consisted of 19,245 patients (8,143 male, mean age 71.6±14.1 yrs; 11,102 female, mean age 76.1±13.7 yrs). Of these, 2,484 were <65 yrs, 5,443 were between 65 and 74, and 11,318 were ≥75 yrs. There were 4,486 (23.3%) fatal‐case outcomes. PE occurred least frequently in spring (n=4,442 or 23.1%) and most frequent in winter (n=5,236 or 27.2%, goodness of fit χ²=75.75, p<0.001). Similar results were obtained for subgroups formed by gender, age, fatal/non‐fatal outcome, presence/absence of major underlying co‐morbid conditions, and specific risk factors. Inferential chronobiological analysis identified a significant annual pattern in PE, with the peak between November and December for the total sample of cases (p<0.001), males (p<0.001), females (p=0.002), fatal and non‐fatal cases (p<0.001 for both), and subgroups formed by age (<65 yrs, p=0.012; 65–74 yrs, p<0.001; ≥75 yrs, p=0.012). This pattern was independent of the presence/absence of hypertension (p=0.003 and p<0.001, respectively), pulmonary disease (p<0.001 and p<0.001, respectively), stroke (p<0.001 and p=0.004, respectively), neoplasms (p=0.005 and p=0.001, respectively), heart failure (p=0.022 and p<0.001, respectively), and deep vein thrombosis (p=0.002 and p<0.001, respectively). However, only a non‐statistically significant trend was found for subgroups formed by cases of diabetes mellitus, infections, renal failure, and trauma.     

Influence of canopy openness,ungulate exclosure,and low‐intensity fire for improved oak regeneration in temperate Europe

Failed oak regeneration is widely reported in temperate forests and has been linked in part to changed disturbance regimes and land‐use. We investigated if the North American fire–oak hypothesis could be applicable to temperate European oaks (Quercus robur, Quercus petraea) using a replicated field experiment with contrasting canopy openness, protection against ungulate browsing (fencing/no fencing), and low‐intensity surface fire (burn/no burn). Survival, relative height growth (RGR_H), browsing damage on naturally regenerated oaks (≤300 cm tall), and changes in competing woody vegetation were monitored over three years. Greater light availability in canopy gaps increased oak RGR_H (p = .034) and tended to increase survival (p = .092). There was also a trend that protection from browsing positively affected RGR_H (p = .058) and survival (p = .059). Burning reduced survival (p < .001), nonetheless, survival rates were relatively high across treatment combinations at the end of the experiment (54%–92%). Most oaks receiving fire were top‐killed and survived by producing new sprouts; therefore, RGR_H in burned plots became strongly negative the first year. Thereafter, RGR_H was greater in burned plots (p = .002). Burning altered the patterns of ungulate browsing frequency on oaks. Overall, browsing frequency was greater during winter; however, in recently burned plots summer browsing was prominent. Burning did not change relative density of oaks, but it had a clear effect on competing woody vegetation as it reduced the number of individuals (p < .001) and their heights (p < .001). Our results suggest that young, temperate European oaks may respond similarly to fire as their North American congeners. However, disturbance from a single low‐intensity fire may not be sufficient to ensure a persistent competitive advantage—multiple fires and canopy thinning to increase light availability may be needed. Further research investigating long‐term fire effects on oaks of various ages, species‐specific response of competitors and implications for biodiversity conservation is needed.     

Characteristics of circulating CD31+ cells from patients with coronary artery disease

Recently, we reported the properties of CD31‐expressing cells in healthy individuals. However, the characteristics of CD31‐expressing cells derived from coronary artery disease (CAD) patients remain unknown. This study aimed to investigate the relationship between circulating CD31⁺ cells and CAD as well as their biological characteristics. Analysis with flow cytometry revealed that CD31⁺ cells (C‐CD31) from the peripheral blood (PB) of CAD patients exhibited low levels of T‐cell marker and high levels of macrophage marker compared with the PB‐CD31⁺ cells from healthy individuals (H‐CD31). In addition, the expression levels of multiple pro‐angiogenic and chemokine genes were significantly down‐regulated in C‐CD31. However, inflammatory gene IL‐1α was highly up‐regulated in C‐CD31. Patients with unstable angina (UA) had significantly more CD31⁺ cells in the PB than healthy control group (P < 0.001). Moreover, there were significant correlations between the number of CD31⁺ cells and cardiovascular (CV) disease activity (R = 0.318, P = 0.006) and the number of diseased coronaries (R = 0.312, P = 0.005). For the diagnostic category of UA, the area under curve was 0.803 (P < 0.001). In conclusion, C‐CD31 have impaired angiogenic potential and the number of circulating CD31⁺ cells were correlated with CV risk. These findings may contribute to the understanding of the pathogenesis of CAD.     

Using fish guilds to assess community responses to temperature and flow regimes in unregulated and regulated Canadian rivers

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Loss of retinal ganglion cells in a new genetic mouse model for primary open‐angle glaucoma

Primary open‐angle glaucoma (POAG) is one of the most common causes for blindness worldwide. Although an elevated intraocular pressure (IOP) is the main risk factor, the exact pathology remained indistinguishable. Therefore, it is necessary to have appropriate models to investigate these mechanisms. Here, we analysed a transgenic glaucoma mouse model (βB1‐CTGF) to elucidate new possible mechanisms of the disease. Therefore, IOP was measured in βB1‐CTGF and wildtype mice at 5, 10 and 15 weeks of age. At 5 and 10 weeks, the IOP in both groups were comparable (P > 0.05). After 15 weeks, a significant elevated IOP was measured in βB1‐CTGF mice (P < 0.001). At 15 weeks, electroretinogram measurements were performed and both the a‐ and b‐wave amplitudes were significantly decreased in βB1‐CTGF retinae (both P < 0.01). Significantly fewer Brn‐3a⁺ retinal ganglion cells (RGCs) were observed in the βB1‐CTGF group on flatmounts (P = 0.02), cross‐sections (P < 0.001) and also via quantitative real‐time PCR (P = 0.02). Additionally, significantly more cleaved caspase 3⁺ RGCs were seen in the βB1‐CTGF group (P = 0.002). Furthermore, a decrease in recoverin⁺ cells was observable in the βB1‐CTGF animals (P = 0.004). Accordingly, a significant down‐regulation of Recoverin mRNA levels were noted (P < 0.001). Gfap expression, on the other hand, was higher in βB1‐CTGF retinae (P = 0.023). Additionally, more glutamine synthetase signal was noted (P = 0.04). Although no alterations were observed regarding photoreceptors via immunohistology, a significant decrease of Rhodopsin (P = 0.003) and Opsin mRNA (P = 0.03) was noted. We therefore assume that the βB1‐CTGF mouse could serve as an excellent model for better understanding the pathomechanisms in POAG.     

Concentration‐dependent studies of Nd3+‐doped zinc phosphate glasses for NIR photoluminescence at 1.05 μm

Nd³⁺‐doped lead‐free zinc phosphate glasses with the chemical compositions (60‐x) NH₄H₂PO₄ + 20ZnO + 10BaF₂ + 10NaF + xNd₂O₃ (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) were prepared using a melt quenching technique. Vibrational bands were assigned and clearly elucidated by Raman spectral profiles for all the glass samples. Judd–Ofelt (J–O) intensity parameters (Ω_λ: λ = 2, 4, 6) were obtained from the spectral intensities of different absorption bands of Nd³⁺ ions. Radiative properties such as radiative transition probabilities (A_R), radiative lifetimes (τ_R) and branching ratios (β_R) for different excited states were calculated using J–O parameters. The near infrared (NIR) photoluminescence spectra exhibited three emission bands (⁴F_3/2 level to ⁴I_13/2, ⁴I_11/2 and ⁴I_9/2 states) for all the concentrations of Nd³⁺ ions. Various luminescence properties were studied by varying the Nd³⁺ concentration for the three spectral profiles. Fluorescence decay curves of the ⁴F_3/2 level were recorded. The energy transfer mechanism that leads to quenching of the ⁴F_3/2 state lifetimes was discussed at higher concentration of Nd³⁺ ions. These glasses are suggested as suitable hosts to produce efficient lasing action in NIR region at 1.05 μm.     

Influence of stand density on soil CO2 efflux for a Pinus densiflora forest in Korea

We investigated the influence of stand density [938 tree ha⁻¹ for high stand density (HD), 600 tree ha⁻¹ for medium stand density (MD), and 375 tree ha⁻¹ for low stand density (LD)] on soil CO₂ efflux (R _S) in a 70-year-old natural Pinus densiflora S. et Z. forest in central Korea. Concurrent with R _S measurements, we measured litterfall, total belowground carbon allocation (TBCA), leaf area index (LAI), soil temperature (ST), soil water content (SWC), and soil nitrogen (N) concentration over a 2-year period. The R _S (t C ha⁻¹ year⁻¹) and leaf litterfall (t C ha⁻¹ year⁻¹) values varied with stand density: 6.21 and 2.03 for HD, 7.45 and 2.37 for MD, and 6.96 and 2.23 for LD, respectively. In addition, R _S was correlated with ST (R ² = 0.77–0.80, P < 0.001) and SWC (R ² = 0.31–0.35, P < 0.001). It appeared that stand density influenced R _S via changes in leaf litterfall, LAI and SWC. Leaf litterfall (R ² = 0.71), TBCA (R ² = 0.64–0.87), and total soil N contents in 2007 (R ² = 0.94) explained a significant amount of the variance in R _S (P < 0.01). The current study showed that stand density is one of the key factors influencing R _S due to the changing biophysical and environmental factors in P. densiflora.