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Liparis loeselii is a rare and declining orchid species restricted to rich fens in the Northern Hemisphere. Habitat destruction, eutrophication, drainage and scrub encroachment have been suggested as reasons for the decline. However, which factors are most important is not well understood. Based on vegetation and environmental properties from extant, potential and historical L. loeselii sites, we 1) developed habitat suitability models from either Ellenberg Indicator Values, which were derived from known habitat preferences of co‐occurring plant species, or field‐measured environmental properties, and 2) identified the primary reasons for the observed decline of L. loeselii. We found nutrient status to be the most important predictor for L. loeselii occurrence, followed by hydrology proxies (Ellenberg reaction and Ellenberg moisture). Vegetation height and Ellenberg light were of minor importance. Effect partitioning based on sites, from which L. loeselii has gone locally extinct, pinpointed eutrophication and drainage to be the most likely primary drivers of the species' demise. Phosphorus limitation induced by discharge of calcium‐rich groundwater seems to be crucial for L. loeselii to sustain populations in landscapes dominated by intensive agriculture. [ABSTRACT FROM AUTHOR]

In order to correctly evaluate the phosphating effect on the surface of galvanized steel plate,the two most typical phosphating film evaluation methods,namely P ratio and crystal coverage rate determination method were compared and analyzed.Different methods were used to determine P ratio and crystal coverage rate of phosphating film,respectively.Results showed that when the accuracy of XRD data of phosphating film could not be determined,the method of measuring the diffraction peak area of P phase and H phase was more accurate than that of determining the P ratio.When the XRD data of phosphating film was accurate,the P ratio calculated by directly measuring the diffraction intensity of P phase and H phase was more accurate.When there were many grain shapes and complex grain distribution in SEM morphology,the crystal coverage rate of phosphating film could be measured more accurately according to Q/JL J130012-2018.When the grain distribution was relatively uniform,the crystal coverage rate of the phosphating film could be measured by Photoshop software analysis method,which was more intuitive to observe the distribution of grain interstice.

Nitrogen deposition usually increases plant N:P stoichiometry and potentially intensifies phosphorus limitations for plant aboveground or belowground growth. However, the effects of P addition on N:P stoichiometry, aboveground biomass (AGB), and belowground biomass (BGB) of the subtropical Chinese fir (Cunninghamia lanceolata) with N deposition remains poorly understood. A 1-year study was conducted to examine the effects of N deposition (0, 30, and 60 kg N ha-1 yr-1 ; N0, N30, and N60) and P application (0, 20, and 40 mg kg-1 ; P0, P20, and P40) on biomass production and N:P stoichiometry in Chinese fir seedlings. N60 alone significantly increased the total biomass; AGB; BGB; N concentrations in the leaves, branches, and roots; and root N:P ratio. P addition alone significantly increased total biomass and AGB. P40 significantly increased P concentration in the leaves, branches, stems, and roots but did not influence N concentration and decreased the N:P ratio. Compared to that with N60 alone, P40 combined with N60 significantly increased the AGB, N concentration in the branches and roots, and N:P ratio of the leaves but significantly decreased the BGB and root-shoot ratio ratio. Total biomass and AGB were significantly and positively correlated with leaf N and P concentrations. Leaf N concentration was significantly and positively correlated with soil available N concentration. Leaf P concentration exhibited a significant and positive correlation with soil available P. These findings provide new ideas about the effect of P addition on Chinese fir biomass accumulation and N:P stoichiometry under N deposition. [ABSTRACT FROM AUTHOR]

Organic grassland farmers are caught between the pressure to operate profitably and the need to ensure ecosystem services like nature conservation. Phosphorus (P) management is at the core of this dilemma: grassland legumes, which are vital for nitrogen (N) inputs, forage quantity and quality, have high P requirements. However, rising soil P contents lead to decreased phytodiversity. We examined this 'P dilemma' based on data of a study in typical organically managed grasslands in north-eastern Germany. We found a slight, but not significant negative correlation between the soil P contents and phytodiversity. Such a negative correlation was much clearer in broader ecological studies of European grasslands, probably due to a scale effect. Despite comparably small P concentrations, we detected only moderate species richness. Thus, other factors besides P concentrations are limiting phytodiversity here, probably N concentrations. The P concentrations in the biomass of various legume species indicated P limitations for most of them. We conclude that a bundle of adapted management measures could reconcile economic and environmental requirements of organic farmers to a certain degree and thus lessen the conflict between the two ecosystem services 'biodiversity' and 'forage production'. [ABSTRACT FROM AUTHOR]

Experiments were conducted to evaluate the N: P ratio, as well as the effects of the interaction between this ratio and zooplankton, on phytoplankton in a tropical reservoir. Three experiments were performed in the presence (+Z) or absence (-Z) of zooplankton and the addition of N and P in different ratios (N : P molar ratio of 5, 16 and 60). In Experiment I, the total phytoplankton biomass and biomass by taxonomic class and species of theN: P 16-Z treatment did not differ significantly from that of the control, whereas for N: P 16+Z, there was a reduction in total phytoplankton. In Experiment II, there was a significant increase in Bacillariophyceae and the biomass of two species in the N: P 60-Z treatment. For the N: P 60+Z treatment, a significant reduction was observed in the total phytoplankton biomass and the biomass of three phytoplankton classes and three species. In Experiment III, there was an increase in the biomass of Dinophyceae with the N: P 5-Z treatment. In the N: P 5+Z treatment, there was a significant reduction in total phytoplankton biomass and the biomass of the phytoplankton class and five species. The findings of the present study reveal that zooplankton species native to a tropical reservoir can change the structure of the phytoplankton community and the response of these organisms to variations in nutrients. [ABSTRACT FROM AUTHOR]

To study the spatial and temporal trends of water quality in the Yuqiao Reservoir (Ji County, Tianjin) in China, water quality data for ten physical and chemical parameters from three monitoring stations (S1, S2 and S3) was collected from 1989 to 2007 and from an other three stations (S4, S5 and S6) during the period of 1999-2007. A one-way ANOVA was employed to evaluate the spatial variation of water quality for each station. The results showed that there were statistically significant spatial differences for most water quality parameters except temperature and dissolved oxygen in the entire reservoir, and the concentrations of most parameters were higher in the uppermost part of the reservoir. The temporal trend study was conducted using the Seasonal-Kendall's test. The results revealed improving trends of water quality from 1989 to 2007, including a reduction of total phosphorous, temperature and biochemical oxygen demand and an increase of dissolved oxygen. High N:P ratios, ranging from 52.61 to 78.75, indicated that the reservoir was a phosphorous-limited environment. This study suggests long-term spatial and temporal variations of water quality in the Yuqiao Reservoir, which could be informative for water quality managers and scientists. [ABSTRACT FROM AUTHOR]

The effect of different amount of monocalcium phosphate on productivity and egg quality of laying hens was investigated. Sixty laying hens were divided randomly into 3 groups (Groups 1-3) each of 20 hens. Group 1 (controls) were fed with diet supplemented with 0.6% of monocalcium phosphate, where amount of available phosphorus (P) was 0.40%. In Groups 2 and 3 (experimental) the diet was supplemented with 1.60% and 2.60% of monocalcium phosphate and with available amount of P -- 0.60% and 0.80%, respectively. The results showed that different amount of monocalcium phosphate, when the ratio of calcium (Ca) and P was 4.5-9:1, had no impact on feed conversion ratio, but have significant influence on the egg laying intensity. After 6 weeks of feeding, when ratio of Ca and P was 4.5:1, laying intensity of hens dropped to 14.6%. Further, the highest laying intensity (82.3%) was registered, when the ratio of Ca and P was 6:1. The eggshell weight, thickness and density were comparable and equally good, when available P in the hens diet was 0.4% or 0.6% and the ratio of Ca and P was 9:1 and 6:1, respectively. During the first 2 weeks of the experiment, when the ratio of Ca and P was 4.5:1 and available P was 0.8%, the eggshell parameters were improved compared to controls (Group 1). However, after 6 weeks of feeding the density, weight and thickness of eggshell in Groups 2 and 3 were statistically significantly lower compared to controls in Group 1 (P<0.05). [ABSTRACT FROM AUTHOR]

We determined concentrations of major nutrients in the vegetation of six habitat types (hummock, scrub, lawn, fen meadow, hollow and marginal stream), spanning a broad range of environmental conditions as regards water-table depth and water chemistry, in five mires on the southern Alps of Italy. Our study was based on chemical analyses of living tissues of plant species, grouped into growth-form based plant functional types (PFTs). We aimed at assessing to what extent the observed differences in tissue nutrient content were accounted for by community composition (both in terms of species and PFTs) and by habitat. Nutrient concentrations were overall lowest in Sphagnum mosses and highest in forbs, although the latter showed large variations presumably due to heterogeneity in mechanisms and adaptations for acquiring nutrients among species within this PFT. Nutrient content patterns in the other three PFTs varied greatly in relation to individual nutrients, with evergreen shrubs showing low nitrogen (N) concentrations, graminoids showing high N concentrations but low potassium (K) and magnesium (Mg) concentrations and deciduous shrubs showing rather high phosphorus (P) concentrations. Habitat accounted for a modest fraction of variation in tissue concentration of all nutrients except P. We concluded that the nutrient status of mire vegetation is primarily controlled by community composition and structure although habitat does exert a direct control on P concentration in the vegetation, presumably through P availability for plant uptake. [ABSTRACT FROM AUTHOR]

The concentrations of the foliar and surface soil nutrients and the variation with species and stand age were studied in Pinus spp. plantations in Zhanggutai area, northeast China. The results showed that the total N, total P and C: N ratio of the soil in P. sylvestris var. mongolica stands were significantly higher in comparison with those in P. tabulaeformis and P. densiflora stands. For P. sylvestris var. mongolica, the foliar P concentration appeared to decrease with age, and the foliar N and K concentrations did not show a consistent change with age. As for the different tree species of the similar age, the foliar N and P concentrations were significantly different (p<0.05), being with P. sylvestris var. mongolica>P. densiflora>P. tabulaeformis. The foliar N: P ratio of P. densiflora significantly was higher than P. sylvestris var. mongolica and P. tabulaeformis, while the foliar K was no obvious difference between the three tree species. There were significant correlation ( p<0.05) between soil total N and P, soil organic matter and total P, foliar N and P, but it did not show significant correlations between soil and foliar nutrient concentrations, which might attribute to the excessive litter raking, overgrazing and low soil moisture in this area. Based on the foliar N: P ratio, we introduced a combination threshold index of N: P ratio with their absolute foliar nutrient concentrations to determine the possible limiting nutrient. According to the critical N: P ratio and their absolute foliar N, P concentrations, the P. sylvestris var. mongolica stands showed a decreased N limitation degree with age, the P. densiflora stands showed unlimited by N and P in the whole, and the P. tabulaeformis stands showed co-limited by N and P. No significant difference in soil nutrient concentrations of the surface soils was found between 45, 29, 20-yr-old Pinus sylvestris var. mongolica plantation stands. [ABSTRACT FROM AUTHOR]

The amount of energy mobilized or stored as protein, expressed as a proportion of the total energy stored or mobilized (defined as the P ratio, Payne & Dugdale, 1977), was investigated in the young male (rapid growth) and adult female (slow growth) rat. Energy mobilization was induced by a 3 d fast and the changes in body content of fat and lean tissues were used to estimate the fasting P ratio (Pfast). Tissue storage was subsequently effected by 17 d of refeeding and the corresponding ratio (Prefed) was calculated from the amounts of lean and fat tissue regained. The same experimental protocol was used for measuring Pfast and Prefed in weanling (30d) and adult (130d) rats. Weight-matched individuals were assigned to three groups. All animals in group 1 were killed at the beginning of the experiment. Animals in group 2 were fasted for 3d and then killed. Group 3 animals were first fasted for 3d, then had free access to a stock diet for a further 17 d before being killed. During fasting, a close linear relationship was found between weight change and body energy changes (r 0·985, and r 0·92, P < 0·001 for weanlings and adult rats respectively) and between carcass N loss and urinary N loss (r 0·933, P < 0·001). These relationships were used to estimate the body energy and N content of each animal at the end of the initial fasting period. Hence, both Pfast and Prefed values could be calculated for all individuals at both ages. When Pfast and Prefed were calculated for adult rats, the mean values were similar (0·138 (SE 0·002) and 0·130 (SE 0·006) respectively). Individually, the Pfast, and Prefed values were correlated (r 0·54, P = 0·058). In weanling rats, the mean Prefed value was about 2·5 times the Pfast (0·421 (SE 0·0113) v. 0·156 (SE 0·004)). Despite the differences in Pfast and Prefed, the individual values were again correlated (r 0·668, P < 0·05). These results support the suggestion made by Payne & Dugdale (1977), that particular P- ratio values are characteristic of individuals and describe the extent to which protein is mobilized or stored during fasting or refeeding. These observations are discussed in relation to the predictions made by the Payne-Dugdale model. [ABSTRACT FROM PUBLISHER]

Increasing frequency and magnitude of climatic extremes, such as heat waves are expected to enhance abiotic stresses on ecological communities. It has been proposed that ecological communities in disturbed habitats may be most sensitive to climatic extremes, as disturbance may reduce density and diversity of higher trophic level organisms like predators. However, there is little experimental evidence that climatic extremes indeed have stronger impact on functioning of such trophically downgraded ecosystems. Here, we experimentally examine how removal of predators from soil communities affects plant performance under periodic heat waves. We used a native plant species, and a congeneric native that is currently expanding its range because of climate change. We used soil nematode communities as the model system, as these are most abundant soil animals and their communities are trophically diverse. Predatory nematodes were manually removed from intact soil nematode communities (mainly the adults as some juveniles are impossible to manually remove) to create a trophically downgraded soil. Intact nematode communities and communities with reduced predatory nematodes were added separately to soils that were planted with either the native Centaurea jacea or the range-expanding congener Centaurea stoebe. Half the experimental units were exposed periodically to experimental heat waves of 10 °C above the control temperature. Our results show that the C: N and C: N: P ratio of plant shoots in predator-reduced soils became lower when exposed to periodic heat waves, however, only in the native plant C. jacea. The decrease in C: N ratio corresponded with increase of an herbivorous nematode in trophically intact soils of C. jacea independent of warming, whereas this relationships disappeared in warmed and predator-reduced soils. Our results accordingly highlight that periodic heat waves may affect stoichiometry of certain plant species by altering trophic interactions in predator-reduced soils. • Predatory nematode loss and periodic warming shifted stoichiometry in a native plant. • Shifts in native plant stoichiometry associated with loss of herbivore nematodes. • No such effects were observed in a range-expanding plant. [ABSTRACT FROM AUTHOR]