Functional grouping of nitrogen fixing trees into discrete groups is a good approach to understanding their influence on ecosystem functioning in their new environment. Most of previous studies have reported faster leaf litter decomposition rates of nitrogen fixing than non-nitrogen fixing species. Meta-analysis using published data is the best way for functionally grouping of nitrogen fixing trees from non-nitrogen fixing trees based on litter decomposition rate. Meta-analysis was used for analyzing litter decomposition rate from published data. The data extracted from 5 papers and 16 species that used laboratory method and 27 papers and 41 species that used litterbag method. Leaf litter decay constant (k year-1) of the nitrogen fixing trees was not different from non-nitrogen fixing trees. Initial leaf litter quality (N or C/N, lignin/N, Tannin and Phenolics) of nitrogen fixing trees in all studies was higher than non-nitrogen fixing trees. Totally, it could be highlighted that leaf litter decomposition is species dependent and functional grouping of the tree species based on nitrogen fixing ability is not reasonable, although it is apparent that the litter quality of the two groups is different.

It is common that the around of seismic energy that was released could be estimated by aftershocks activity. This study is local station data of aftershocks, nearly 40 years in Iran. Reduce trend number of aftershocks analyze for eight earthquakes. Then time decay rate of aftershocks in the region was indicated. Next, decay curves of aftershocks for Omori, Utsu, Mogi and Kisslinger models were indicated. This study analyzed the aftershocks of the 1962 Buin-Zahra, the 1968 Dasht-e-Bayaz, the 1990 Rudbar, the 1990 Fork, the 1997 Ardabil, the 2002 Avaj, the 2004 Baladeh and the 2005 Zarand earthquakes. Aftershocks decay was indicated and it was obtained that the Omori model is the best model in Iran.

In order to determine the rate of litter decomposition in Alnus subcordata in two alder stands, litters from Vaz and Asalem with different parent materials were collected in autumn. Litters from each region were put in four vases for 7 months in laboratory conditions. Sampling was done within every 21 days. Nitrogen and carbon content were measured in each interval. On the first day, the comparative study between the two regions showed that there existed no significant difference between C and N content in litters.The amounts of N were 2.49 % and 2.62 % in litters of Vaz and Asalem respectively. Carbon content was 13.35 % in Vaz and 33.? % in Asalem. Rate of carbon variation indicated no significant difference in the two regions. Rate of nitrogen and CIN variation exhibited a significant difference in the two regions. CIN was reduced from 17.38 to 10.35 and from 15.12 to 10.67 in Vaz and Asaiem stands respectively.

In the railway transportation industry, the rail is considered to be the dominant source of rolling noise over the usual speed range (<160km/h). It has been well documented that the rate of decay of vibration along the rail is closely linked to the noise performance of the track. In this study, a finite element model of a periodic supported rail is developed in ABAQUS to study the acoustic performance of the rail. To compute the decay rates, acceleration responses along the rail are converted into the frequency domain and then the decay rates are obtained for each 1/3 octave band by processing the response levels. It is shown that the decay rate results obtained by FEM follow the same trend as the measured decay rate. Therefore the FEM decay rate can be used for generating comparisons between different tracks as an indicator of their acoustic performance. To test the vertical decay rate on a real track, a rail section at the Sadeghieh subway site is also tested and analyzed. To this end, the vertical responses of the rail are measured by two accelerometers. It is shown that at low frequencies (below the cut-on frequency), the decay rate resulting from the accelerometer on the sleeper place is 2dB less than the decay rate result from the accelerometer on the mid–point. However at high frequencies (above cut-on frequency), the decay rate results from both accelerometers correspond closely to each other.

The aim of this study was investigation of Carbon, Nitrogen and Phosphorus dynamics in Carpinus betulusL. leaf litter in organic layer of a broad-leaved mixed forest in Gorgan. Fresh litters were collected from five plots in district one, Shastkalate forest and were placed into some litterbags with 2 mm mesh. Then, they were located in the study site. Over one year (8 sampling), chemical analysis was carried out. Result showed total Nitrogen concentration in fresh litters was 1.5% and after one year increased to 1.9%. Phosphorus concentration in fresh litter was 0.134% and increased to 0.136% after one year. Carbon to Nitrogen ratio in fresh litter was 24.5, but after one year decreased to 17.4. Carbon to Phosphorus ratio in fresh litter was 282 and after one year decreased to 245. Weight of fresh litter was 14.65gr, but decreased to 8.23gr after one year. Nitrogen content, C/N and N/P ratios of Hornbeam leaf litters were correlated with secondary weight of litter. C/N and C/P ratios were appropriated for discriminating of decomposition phases. Hornbeam Leaf litters caused soil fertility and increased site indexes. It is necessary to useCarpinus in reforestation and rehabilitation of destroyed forest, considering climate, elevation and forest degradation density.

Purpose: Wastes were composted and applied as the soils amendment to improve soil fertility and crop productivity. The study aimed at assessing the nutrient uptake and growth of spinach (Spinacia oleracea L.) grown in soils amended with cow manure after a co-composting process.Methods: Sandy loam and silt loam soils were amended with cow manure after co-composting with poplar leaf litter at 1: 0, 1: 1, 1: 2 and 1: 3. The compost was applied to soil at the rate of 20 t ha-1. Spinach was grown for 8 weeks and then harvested to measure plant shoot biomass. Spinach shoot samples were digested and nutrient contents in the shoots were determined.Results: Co-composted manure significantly improved the growth and nutrients availability to the spinach. Dry biomass, P and K contents in spinach shoot varied among manure: leaf litter ratios: 1: 0\1: 1\1: 2\1: 3. Conversely, N, Zn, Fe, Cu and Cd contents in spinach shoot reduced with the manure amendment with increasing amount of leaf litter. Water extractable micro-elements in the post-harvest soils were found in the order of Zn [Fe [Cu [Cd. Co-compost amendments increased the P and K availability except N, NO3 and NH4 in the post-harvest soils. Trace elements in the post-harvest soils reduced with leaf additives in the compost.Conclusions: Co-composted cow manure with leaf litter proved to be superior in terms of bioavailability of plant nutrients over the composted manure without leaf litter. This may also assist in mitigating the environmental contamination of heavy metals in the farm lands.

Litter decomposition process is a vital process in forest biogeochemical cycles causing nutrient release into the soil. Lignin degradation is considered as the limiting step in litter decomposition. This research was done to study the factors regulating the litter mass loss of beech (Fagus orientalis lipsky), alder (Alnus subcordata C.A.Meyer), maple (Acer velutinum Boiss.) and Norway spruce (Picea abies (L) Karst) in late decomposition stages for 405 days using litterbag method in pure Norway spruce plantation in Lajim Region. The findings of this study showed that litter decomposition of all litters had a positive and significant correlation with initial litter nitrogen and manganese concentrations (P<0.05 and 0.01, respectively) and negative correlation with lignin concentration, C:N and lignin:N ratios (P<0.05). In addition, the results showed that the correlation between mass loss and releasing of nitrogen, manganese and lignin is significant and this correlation was negative only for manganese. According to the results, it was found that the composition of deciduous species litters, especially beech and spruce needles in the Hyrcanian mountainous forests can be effective in accelerating the decomposition process.