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This study presents changes in the concentrations of nitrogen and phosphorus in two streams in Western Antarctica (Admiralty Bay, King George Island, South Shetlands) that differ in trophic status. The results suggest a decline in concentrations of the determined forms of N and P between 2001 and 2005. The decrease ranged from 9.3% for reactive phosphorus to 73.2% for ammonium-nitrogen. Such inferred declines in N and P concentrations are considered to reflect reduced deposition on land of organic matter brought in from the seas by the penguins nesting in the area. The ultimate cause of this is in turn the steady decline in abundance that is being noted for these penguins.
Light environments can have a considerable influence on how plants respond to defoliation through influencing the biomass allocation patterns and internal C/N ratio. Seedlings of Lolium perenne, a common perennial grass species, were grown for eight weeks under three different light environments (natural light, red light and shading) and two different defoliation treatments (no defoliation versus 50% aboveground biomass removal). This study was conducted to examine (1) the effects of light regimes and defoliation on biomass accumulation, biomass allocation and internal C/N ratio status in plants; (2) how the light regimes influence the pattern of compensatory growth after defoliation; and (3) the relationship between compensatory growth and the internal C/N ratio status. We found that red light altered the shoot-to-root allometry, enhanced the leaf C concentrations and induced N deficiency. By contrast, the leaf N concentrations of L. perenne were greater during shading treatment, which simultaneously enhanced shoot growth and stopped root growth. Under defoliation, red light increased shoot growth, not at the expense of root growth, which was not the same as in natural light and shading treatment. Moreover, regardless of the unclipped (no defoliation) and defoliation conditions, the L. perenne biomass partitioning between roots and shoots was significantly correlated with the leaf N concentrations and C/N ratio, indicating that allometric biomass allocation can be largely modulated by signals related to the C and N status of the plants. These results demonstrated that the leaf C and N status would be an appropriate indicator of compensatory growth after defoliation.
The aim of the work was to assess the temporal distribution of NO2 and NOx concentration in relation to wind direction and to determine the effect of major meteorological elements on the size of NO2 and NOx concentration in northwest Poland. In the area of the research, in the period from 1st May 2005 to 30th April 2007 the highest average concentration of NO2 and NOx, both during cold and warm half-years, occurred with southeasterly wind, and the lowest with south-westerly wind for NO2 and with north-easterly wind for NOx. The highest determination coeffi cients and, at the same time, the smallest estimation errors for multiple regression equations, describing the dependence of the concentration of NO2 and NOx from meteorological elements, were obtained with westerly wind in the cold half-year and with south-westerly wind in the warm half-year.
There were showed influence of the points (local and city reception basin outflow) and the areas (recreation area and wasteland) differentiation of pollution sources on the concentration of nitrogen and phosphorus compounds in water of Mały Jeziorak Lake. There were analyzed NO₃⁻, NO₂⁻, NH₄⁺, total P and PO₄⁻³ content. Results of the studies were indicated that the most components concentration was low in I class of water cleanliness. There was more ammonium and nitrate nitrogen content near the recreation area and more nitrate nitrogen content in spring and summer time near the dairy outflow. Moreover, higher total phosphorus content but not more than in I class of water cleanliness norm were in the lake water with village rain outflow and near the recreation area and, phosphates content in II class water cleanliness in spring time near the recreation area.
To assess nitrogen (N) resorption patterns in semi-arid sandy land, N concentrations in green leaves (Ng) and senesced leaves (Ns) of 35 species of shrubs and herbages were measured along habitats of decreasing soil total N (0.54 to 0.041 g g⁻¹ d.w. of top soil level) in Horqin Sandy Land (Inner Mongolia, China). These habitats are following: inter-dune grassland (IDG), fixed sand dune (FD), semi-fixed sand dune (SFD), semi-mobile sand dune (SMD), and mobile sand dune (MD) were considered. Results showed that Ng and Ns (i.e. nitrogen resorption proficiency, NRP) increased and leaf nitrogen use efficiency (NUE) decreased significantly with increasing soil N status across the above habitas, but nitrogen resorption efficiency (NRE) was not affected. The levels of Ng, Ns and NUE experience two stages across habitats: first, there were low Ng and Ns and high NUE in MD and SMD; second, there were high Ng and Ns and low NUE in IDG, FD and SFD. Plants from IDG, FD and SFD had incomplete N resorption during foliar senescence, but plants from MD and SMD had complete N resorption. Leaf NRE was determined by life forms which had no significant effect on Ng but on Ns and NUE. For all plants in the five habitats, NRE and NUE decreased with the sequence of grass, herb, shrub, while Ns showed a contrary tendency. Plants from strong N limitation habitats did not show higher NRE, but showed higher NRP and leaf NUE, so NRP was a more sensitive indicator of changes in N status than NRE. In conclusion, Leaf N resorption patterns were mainly determined by soil N status across habitats, and there were some consistent patterns among life forms.
Performance of two data-driven models that were developed using Artificial Neural Networks (ANNs) and Multiple Linear Regression (MLR) approaches were investigated in prediction of Total Nitrogen (TN) concentration in twenty-one river basins in Chugoku district of Japan. Comparison of TN concentration predictions, which were carried out using an ANN-based model and MLR-based model indicated that prediction of the former model (r²=0.94, p<0.01) was more accurate than that of the latter model (r²=0.85, p<0.01). Lack of a sufficient data set that might be considered an obstacle for cross-validating models that are developed was dealt with using a Monte Carlo-based sensitivity analysis of the developed models. This initiative could provide reliable information for judging predictive capacity of the developed models stochastically. Result of sensitivity analysis revealed that predictive capacity of the ANN-based model varied between 0-2 mg/L. Moreover, prediction of the negative outputs was not observed. using the ANN-based model for TN concentration in stream water.
Soil nutrient pattern can be a functional tool for grassland restoration. In order to promote the growth of a specific or group of expected plant species, it is necessary to measure the responses of different species to nutrient – rich patches and detect the differences among them. In this article, we measured aboveground biomass and morphological traits of six species as dry weight, length, surface area, specific root length and diameter of fine roots in response to nitrogen addition patches using ingrowth core method. The six species are Artemisia scoparia, Stipa bungeana, Artemisia sacrorum, Artemisia giraldii, Lespedeza dahurica and Astragalus melilotoides. All are the dominant species in different stages of secondary succession of loess hilly region, China. Twelve individuals of each species were selected to install ingrowth cores. Six of the individuals were used as treatment group, they were treated to install with four cores of no (addition’s control), low, medium and high levels of nitrogen additions. Another six of them were used as species’ control group, the four installed cores around them had no nitrogen addition. The results showed that: 1) After 105 days in situ, for all the six species, summed dry weight, length and surface area measured in the four cores of the treatment group were significantly greater than the corresponding values in species’ control group. In aboveground biomass, however, only A. scoparia in the treatment group had significantly outweighed that in the species’ control group. 2) Irrespective of nitrogen additions levels, significant differences of length, diameter and surface area existed among the six species, which implied that species had their intrinsic species specific morphological traits. 3) In dry weight, length and surface area, the responses of all the six species to nitrogen addition levels were positive, significantly more roots were grew into the cores with higher nitrogen additions; while in specific root length, the responses were negative. 4) Perhaps the six species had a special nitrogen requirement, as interaction effects of species and addition levels in surface area were found significant. 5) The foraging precision of the six species to nutrient-rich patches had positive but insignificant correlation with root system size; there existed a significant positive correlation between the precision and the sensitivity to the designed patchy habiats. 6) Among the six species, A. scoparia, A. sacrorum and S. bungeana have higher sensitivity and precision than L. dahurica and A. melilotoides in terms of foraging the nitrogen addition cores or patches. It seems that fast growing species that dominate in early successional stage, like A. scoparia and S. bungeana in our case, obtained more benefits from nutrient patchy habitat. We advised that, in infertile lands, fertiliser be applied in a patchy way to accelerate the restoration of old fields as early as possible once they were abandoned.
Foliar nutrient resorption is an important strategy which allows leaf nutrients to be reused rather than lost with leaf fall, particularly in nutrient-poor ecosystems where even small nutrient losses can have significantly negative impacts on plant survival, competitive ability, and fitness. However, plants vary greatly in nitrogen (N) and phosphorus (P) resorption among plant growth forms during leaf senescence, which may be vital to understand the role of plant growth forms in ecosystem functioning. Green and senesced leaf N and P concentrations of 39 plant species in sandy grassland (Horqin Sand Land) of northern China were analyzed to detect variations of nutrient resorption efficiency among plant growth forms. The results showed that nitrogen resorption efficiency (NRE) ranged from 29% to 74%, with an average (± SD) of 50.3 ± 11.2%, and phosphorus resorption efficiency (PRE) varied among species between 46% and 82%, with a mean (± SD) of 68.4 ± 6.9%, suggesting that nutrient resorption is a vital nutrient conservation strategy in this ecosystem. In addition, NRE and PRE differed significantly among the dominant plant growth forms in this sandy grassland. NRE for N-fixing species and graminoids were significantly lower relative to NRE for shrubs and forbs, but mean PRE of graminoids was significantly higher than those of N fixers, shrubs and forbs. These data give indirect evidence that the differentiation of N and P conservation serve as an important mechanism permitting the co-existence of growth forms in arid systems.
We observed, both in the leaves and roots of the vegetables examined, that the concentration of fluoride was in each case higher in vegetable samples in Łosień, 6 km from the “Katowice” Steel Works (fluorine emitters), than in the vegetable samples grown in Nowy Sącz, 200 km from the “Katowice” Steel Works (in the area of relatively low fluorine pollution). The highest F content was characteristic of beet (Beta vulgaris) leaves and root samples, the lower one was found in celery (Apium graveolens) leaves and root samples and the lowest one in savoy (Brassica oleracea) leaf samples. The highest and lowest F- concentrations in the leaf samples examined was c.a. 33 mg/kg D.W. (beet leaves from Łosień of 1995) and c.a. 11 mg/kg D.W. (savoy leaves from Nowy Sącz of 1996). Moreover, it was found that the observed growth of F- concentration in the savoy leaf samples, both from Łosień and Nowy Sącz, correlated with an increase of nitrogen concentration in them.
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