جستجوی مقالات مرتبط با کلیدواژه « soil respiration » در نشریات گروه « کشاورزی »

Soil is a dynamic natural system and interface between land, air, water, and life, which performs vital services for human sustenance. The increasing population growth has led to the excessive use of this natural resource to provide food, clothing and other human needs. This has led farmers in different parts of the world to improper exploitation of inferior and marginal lands such as pastures and forests located on sloping lands. However, on the one hand, these lands have low potential and on the other hand, they have a high potential for erosion. Soil quality is usually introduced as the ability of the soil to interact with the ecosystem maintain the productivity of the quality of different parts of the environment and thus improve the health of plants, animals and humans. The quality of soil and its importance for the development of sustainable agriculture are more important nowadays. Land use change is one of the most important current problems of our country, especially in the Hyrcanian forest lands in the north of the Iran. The objectives of this study were to evaluate the effects of land use change on some soil quality indicators in north of Iran.

A part area in the south of Lahijan was selected including 3 land uses: Natural Forest (NF), Tea plantation (TP) and paddy rice (PR) cultivation. In each land use 10 soil samples were collected at 0-20 cm depth and transferred to the laboratory. Undisturbed soils samples by core was taken for measurement of bulk density. A part of sample passed through the 4 mm sieve for measurement of aggregate stability and three indices comprised mean weight diameter: MWD, geometric mean diameter: GMD and water stable aggregates: WSA were calculated. Other soil properties such as pH, Calcium carbonate equivalent (CCE), soil organic matter (SOM), particulate organic carbon (POC), and soil respiration also measured.

The statistical results in this study showed that due to the change of land use from forest to tea and rice cultivation, the amount of organic carbon decreased, while the amount of pH and calcium carbonate increased. As a result of changing the use of forest land to other two land uses, the indicators of stability of soil aggregates (MWD, GMD and WSA) have significantly decreased, and as a result, the bulk density of the soil has increased. The amount of MWD was 1.95 mm in the forest, 1.2 mm in the tea plantation, and 0.45 mm in the rice cultivation. The amount of particulate organic carbon as one of the indicators of soil quality in forest lands was observed in the maximum amount. In addition to the reduction of particulate organic matter, this change is also caused by the excessive traffic of machines. Soil microbial respiration was analyzed as a soil biological indicator. The results showed that the average microbial respiration in the natural forest was equal to 300 mg C/ day.g soil, and in the two other land uses of tea and rice cultivation, it was calculated as 200 and 120 mg C/ day.g soil, respectively. Positive and significant relationship between SOM and MWD confirmed that soil organic matter had high contribution for soil aggregate formation and its stability.

This research was conducted to investigate the impacts of land use changes in the north of Iran in Gilan province on some soil quality indicators. The results of this research showed that the soil’s chemical, physical, and biological characteristics have shown significant differences due to land use change. In forest soils, the highest amount of organic carbon, and the lowest amount of pH was observed, which is due to the high accumulation of organic matter and high leaching of cations. Due to the degradation of organic carbon in the other two uses, the bulk density and aggregate stability indicators have decreased. The intense cultivation operations in the other two uses, especially in the paddy fields, have destroyed the soil structure. Also, more organic carbon in forest soils has led to more microbial respiration. In total, all soil quality indicators have decreased with the change in land use in the study area. Therefore, land conversion and especially deforestation in the studied region should be avoided. In total, the results showed that land use change in the study area has caused land degradation and reduced the soil quality and soil health indicators, and it is necessary to consider it in land use planning, land improvement, and sustainable land management.

In this study, the impact of boxwood moth pest defoliation on the dynamics of leaf litter and soil nutrients in the Cheshmebolbel boxwood (Buxus hyrcana) reserve was evaluated. A random sampling technique was employed to collect litter layer samples (using a 400 cm2 frame) and soil samples (using a metal cylinder with an 8 cm diameter and a 10 cm depth) from 32 sites in unpolluted and polluted boxwood stands. The results revealed that only soil moisture percentage differed significantly among the soil physical variables, whereas all chemical soil variables showed significant differences between the two polluted and unpolluted boxwood sites. Furthermore, basal respiration (0.14, 0.12), metabolic rate, microbial ratio, and carbon availability index were significantly higher in the polluted sites compared to the unpolluted site, while no significant difference was observed based on the microbial-carbon respiration index. The principal component analysis (PCA) results demonstrated a distinct separation of the two sites, both polluted and unpolluted, along the first axis, based on both litter and soil variables. In this context, nitrogen, metabolic rate, moisture, nitrate, ammonium, and stimulated respiration (0.30, 0.39) exhibited a positive correlation with the first axis, representing the concentration of the unpolluted stand. On the other hand, C/N ratio, potassium, magnesium, calcium, and microbial biomass carbon displayed a negative correlation with the first axis, representing the concentration of unpolluted sites. In general, the findings of this research underscore the substantial influence of defoliation induced by pest outbreaks on an important aspect of forest ecosystem health, performance, and nutrient cycling.

 Microbial respiration and microbial carbon biomass are two important biological indicators for assessing ecosystem quality that can be used to determine ecosystem health. The aim of this study was to investigate the change in soil microbial activities in forest different structure in Kurdistan province.

  Four one-hectare sample plots (100×100 meters) were selected in Baneh (two sample plots), Marivan and Sarvabad counties and structural characteristics of stands were measured. In order to investigate the changes in soil microbial activities in each sample plot, seven soil samples were taken from a depth of 0-10 cm in each site (a total of 28 soil samples) in August 2019 (28 samples in total). In this study, microbial activities including soil respiration, induced soil respiration, nitrification potential and microbial carbon biomass were compared in four stands (site). One-Way ANOVA and Duncan's test were used to evaluate the significance of differences in soil microbial characteristics between the four sites.

  The results showed that there was a significant difference between the parameters of soil respiration, induced soil respiration and microbial carbon biomass of soil between the four studied stands, but no significant difference was observed in terms of nitrification potential. Also, for soil respiration, induced soil respiration and microbial carbon biomass of soil parameters in Belveh site with 2.45 (mg CO2.g -1  dm. 24 -1 ), Belveh site with 48.21 (mg CO2.100g -1  dm. 24 -1), Dolah-Naw site with 280.9 (µg N.g-1 dm.5h-1) and Saraki site with 5.35 (mg carbon biomass /100 gr) had the highest average. Therefore, for nitrification potential of Doleh Naw (with young aged coppice forest) site was the highest values ​​and highest value of soil respiration, induced soil respiration observed in  Belveh site (unaged coppice forest with to two story layer).

 Therefore, forest structure area effects on soil microbial characteristics (soil respiration, induced soil respiration and microbial carbon biomass). For sustainable forest management, it is recommended to study soil microbial activities in periodic monitoring and positive effect microbial carbon biomass on forest, in Sareki and Belveh site (area lowest average of microbial carbon biomass), afforestation with native species be done.

Soil in forest ecosystems is a giant source for storage of atmospheric carbon that would increase its contribution against climate warming under proper management. In the current research, soil and litter contribution in carbon sequestration were compared between a 50 years old enclosure (less degraded) and un- enclosure (degraded) wild pear stands. Besides, some soil characteristics including soil moisture, bulk density, organic carbon, total nitrogen, phosphorus, and soil microbial respiration were studied. In each stand, 5 soil samples and 10 litter samples were collected from each plot and the characteristics were compared with T-student independent analysis. The results clearly indicated that soil carbon storage and carbon storage in coarse litter due to greater tree covers in enclosure field were two times higher than un- enclos6ure. Meanwhile, carbon storage in fine litter was same in the both stands. Phousphurus content and total nitrogen in soil of enclosure field were 6 and 2 times higher than un- inclosure, respectively. Moisture content Not only was higher in less degraded field (36%) in comparison with degraded one (21%) but also soil microbial respiration in less degraded field was higher around 31% when compared with degraded field. Finally, it can be proposed that enclosure management not only can improve soil carbon storage more than two times but also can increase soil fertility. This finding highlights the importance of enclosure management in Zagros region for maintaining of soil functions.

The qualitative characteristics of forest soils can change under the influence of complex climatic interactions, soil type, management type, and tree species type. The aim of this study was to investigate the variability of soil quality characteristics in two forest plantations of Quercus castaneifolia C. A. Mey and Pinus radiate D. Don in Wood and PaperForests of Mazandaran Province. In both stands, 36 samples were randomly selected for determination of soil physical characteristics, in one season (autumn), and chemical and biological characteristics, in four seasons (autumn, winter, spring and summer). Physical characteristics (clay, silt, sand, moisture, bulk density and lime), chemical characteristics (pH, EC, nitrogen, phosphorus, potassium, carbon to nitrogenratio) and soil biology (soil respiration, microbial biomass carbon, fine root biomass, metabolic rate, and urease enzyme activity) were measured. The results of this study showed that the concentration of nitrogen, phosphorus and enzyme urease activity in oak stands was significantly higher than pine stand (p < /span><0.01), but potassium concentrations were significantly (p < /span><0.01) higher in the pine stand. In all seasons, the rate of soil respiration in the pine stand was higher than in the oak, but this difference was only significant in summer (p <0.05). Characteristics such as carbon to nitrogen ratio, soil carbon, microbial biomass carbon, fine root biomass, and metabolic coefficient were significantly higher in pine stand than in oak in all seasons (p <0.01). The results of this study showed that, in the nitrogen cycle, the oak stand, but in relation to the carbon cycle and global warming, the pine stand had more effects on the soil characteristics. Overall, the practical results of this study suggest that, to improve soil conditions in the degraded forestlands in northern parts of Iran, plantation of oak species is preferred.

The decline of trees has been raised as one of the main problems in arid and semi-arid regions. Understanding the type and extent of the relationships among different environmental factors – e.g. soil characteristics as the basis for growth and development of plant species - and natural disturbances can be facilitated the ways of sustainable forest management and a useful tool for monitoring them. This study aimed to compare some soil physical, chemical and microbial properties in relation to the oak decline in the southern Zagros forest in Malekshahi county in Ilam province. The two-way analysis of variance showed that the effect of elevation, as well as the interaction between oak vitality classes and elevation on soil salinity, organic carbon, nitrogen, potassium and lime were significant. Among soil chemical properties, the factors of organic carbon (OC), nitrogen (N), Potassium (K) and electrical conductivity (EC) of the understory of trees were significantly affected by elevation, oak vitality classes and the elevation by vitality interaction. Higher values of these characteristics observed under the healthy oak trees in highland, which indicated a decreasing trend with increasing rates of drought in this elevation class. The effect of elevation and oak vitality and their interaction on sand, clay and bulk density was significant. The results showed that the soil saturated moisture content was significantly lower under dead trees (33.9%) in middle land and semi-dried trees (32.28%) in lowland than other trees. The percentage of sand was higher under dead trees than semi-dried and healthy trees in lowland and midland. A minimum amount of soil bulk density was found at all three classes of elevation under the semi-dried trees showed. The interaction between elevation and vitality was significant on basal respiration (BR) and substrate-induced respiration (SIR). The highest values of BR and SIR observed under healthy trees in highland (71.22 and 97.32 mgCO2-C kg-1 day-1) which a decreasing trend has been found with the increasing intensity of tree dieback in the study area. The amount of N, OC, and K showed the highest value under healthy oak trees in highland. According to the obtained results, it can be concluded that the soil chemical and biological properties can be able to predict the decline of trees along the elevation gradient.

Various evaluations have shown that agricultural operations can have a dramatic impact on the quality of soils. Therefore, knowledge of soil quality in agricultural and natural resources is essential for optimal land management and achieving maximum economic efficiency. In this research, the long-term effects of conventional agricultural management in three areas of Ziveh, Nazlo, and Sirdagh with different moisture properties. Four soil samples (including two cultivated soil samples and two adjacent un-cultivated soil samples as control) were collected from each region in West Azerbaijan province. Some soil biological and chemical properties were investigated. Basal respiration rates, respiration due to substrate, microbial biomass, microbial population and nematode populations were investigated. The results showed that cultivation reduced basal respiration, substrate induced respiration, microbial population and nematode population in the studied areas. Also in uncultivated land use basal respiration rates (1.25, 1.1 and 1.75) and substrate respiration (1.8, 2.2 and 1.4) increase related to cultivated in the studied areas Sirdaghi, Naslow and ziveh, respectively. Basal respiration, substrate-induced respiration, carbon availability index and population of nematodes were 1.25, 1.8, 1.6 and 3.28 times higher in uncultivated related to cultivated in Sirdaghi, respectively. In general, it can be concluded that unscientific cultivation operations and lack of increasing organic matter will result in a loss of biological properties, and in the long- time result a decrease in soil quality.

The aim of this study was to investigate soil respiration in the plantation stands of Acer velutinum, Quercus castaneifolia, Fraxinus excelsior and Pinus brutia and to compare them with the natural stands in Sari educational-research forest of Darabkola. In order to measure physical and chemical properties of soil in each stand, 10 points were selected systematic randomly and samples were taken at a depth of 0-10 cm with coring method. Percentage of moisture, bulk density, pH, EC, organic carbon and total nitrogen were measured in the laboratory. Six 6 tubes (diameter and height = 10 cm) were installed at a depth of 0 - 10 cm in each stands in early September and soil respiration was measured using CO2-Port device (Germany). The highest soil pH (7.33 ± 0.07), potassium (940.4 ± 4) and phosphorus (88.6 ± 1.52) were observed in Acer velutinum plantation and the lowest soil moisture content (35.21 ± 0.86), pH (6.83 ± 0.77) and EC (0.26 ± 0.02) were obtained in Pinus brutia plantation. The highest soil respiration was observed in Acer velutinum and Quercus castaneifolia plantation stands and the lowest was found in Pinus brutia and Fraxinus excelsior plantation stands, which was significantly lower than the control stand. In general, results showed that Acer velutinum plantation had positive effects on soil properties.

Healthy lifestyle on dry land depends on monitoring and maintenance of the ponds. The aim of this study was to assess the effects of surface water-inflows on biological characteristics of wetland soils around Arak Meyghan-Lake. Two soil layers (0-30 and 30-60 cm) in the 4 sites of surface water-inflows were sampled in May and November 2014. The sites were the release sites of treated-municipal-wastewater, Shahrab-River, Farah-River and sodium sulfate-processing plant wastewater. The number of culturable microorganisms in the samples was counted on solid media and the soil basal-respiration (BR), substrate-induced-respiration (SIR), metabolic-quotient (MQ) and microbial-coefficient (MC) were measured. The number of soil fungi in the site Farahan-River site and the numbers of soil bacteria, enteric bacteria and actinomycetes in the release site of municipal wastewater especially in topsoil and in spring were significantly higher compared to those in the 3 other sites (respectively 4.85, 6, 5.51 and 3.92 log numbers). The numbers of the studied microorganisms in soil in the release site of sulfate-plant wastewater were significantly low and the numbers of fungi and actinomycetes were negligible in the most samples. Soil SIR was the most susceptible and responsive index among the studied biological properties. The release of municipal-wastewater in the playa improved the soil biological indices like BR (0.102 mg CO2 g-1 soil day-1), SIR (3.688 mg CO2 g-1 soil day-1), and MC (0.196 mg Cmic mg-1 Corg) significantly. In contrast, the MQ was significantly high in the release site of Shahrab-River and sulfate-plant wastewater (2.60 and 2.52 (mg C-CO2 g-1 Cmic h-1) respectively), showing the negative effects and the higher salt tension in these sites. Although the release of municipal-wastewater in Meyghan-Lake had positive effects on soil biological characteristics, it may have negative effects on biodiversity of these salty soils.

Soil compaction is a worldwide environmental problem. Investigations on soil compaction have focused mainly on its effects on soil physical parameters and plant growth. There is an essential need to identify the effect of soil compaction on soil organisms and biological process, especially in arid and semiarid regions such as Iran. The main objective of this research was to investigate the effect of soil compaction and organic matter on soil respiration and microbial biomass carbon, urease activity, and soil nitrification. Therefore, a factorial experiment was conducted based on completely randomized design with three replications in greenhouse conditions. Treatments included different compaction levels (0, 10, and 20 %) and organic matter addition (0 and 2 %W/W from the bagasse compost). The results indicated that the effects of soil compaction and organic matter on soil respiration, microbial biomass carbon, urease activity, and soil nitrification rate were significant. Also, the interaction effect of soil compaction and organic matter on the measured biological properties were significant (p<0.01). Furthermore, the results showed that the value of all measured biological properties decreased with increasing soil compaction, whereas, increasing soil organic matter improved those properties and the amount of microbial respiration, microbial biomass carbon, urease activity and soil nitrification significantly increased. Therefore, increasing organic matter or plant residues is an important management approach that can improve soil characteristics and performance.

The conversion of forests to agricultural lands generally has damaging effects on soil qualitative indices. This study was conducted to investigate the effects of land use change on the physico- chemical and biological characteristics of the soils of Mokhtar Plain, Yasouj Region. Five soil samples (0- 30 cm) were taken from three land uses of dense forest, degraded forest, and dry farming. The physical, chemical and biological analyses were carried out in a completely randomized design. The results showed that by following the change in the forest land use to dry farming, the EC (56%), organic matter (67%), total nitrogen (71%), exchangeable potassium (48%), Basal respiration (42%), exhaled respiration (63%), fungi community (23%), acid phosphatase (59%), and alkaline phosphatase (79%) were decreased in the dry farming land use. However, the bacterial community (20%) and pH (5%) were increased in the dry farming land use and the amount of available phosphorus did not show any significant difference, as compared to the dense forest. In general, it can be concluded that by following forest degradation and change in land use, soil organic matter and its related indices, especially biological ones, are more affected. So, in order to maintain soil quality, appropriate management practices such as managed land use change, avoidance of tree cutting, especially on steep slopes, preventing of overgrazing, and addition of organic matter should be carried out in dry farming land use.

In the twentieth century, soil quality and health declining has become a major challenge due to application of poor and polluted water sources. Accordingly, the effect of different concentrations of cobalt chloride and cadmium chloride in irrigation water (0 (control), 100, 200 and 400 mM) on some soil microbial indices during vegetative growth of the medicinal Savory plant (Satureja hortensis L.), in two separate experiments was carried out in a completely randomized design with three replications in the research greenhouse of Agricultural Faculty in Ilam. The experiments were done in 5 kg-pots with 26 cm in height and 30 cm in diameter and longed for two months in 2014. The results showed the highest values of basal respiration rate and substrateinduced respiration in the control and the lowest values of these two indices in 400 mM concentrations of cadmium chloride and cobalt chloride. In terms of soil microbial biomass carbon, the highest value (308 mg.kg-1 soil) and the lowest value (190 mg.kg-1 soil) were found in the control and 400 mM concentration of cadmium chloride salt solution, respectively. The highest (27 mg.kg-1 soil) and the lowest (14 mg.kg-1 soil) values of soil microbial biomass nitrogen were found in control and 400 mM concentration of cadmium chloride, respectively. As well as, the lowest (19 mg.kg-1 soil) amount of soil microbial biomass nitrogen was obtained in 400 mM concentration of cobalt chloride salt solution. The highest amount of microbial quotient, metabolic coefficient and microbial biomass were observed in the control treatment. The microbial biomass carbon and microbial biomass nitrogen ratio increased by irrigation water with different concentrations of cobalt chloride. Increasing the concentrations of cadmium chloride and cobalt chloride showed a negative effect on the microbial quality of the soil, which will pay more attention to the quality of irrigation water for health and quality of the soil microbial community, and hence the quality and overall health of the plant, and ultimately represent health and food safety.

The present study was carried out to investigate the effect of two species of Pinus eldarica and Robinia pseudoacacia on soil properties and carbon dioxide emission in the Khargoosh dareh forest park in Tehran. For this purpose, four plots of 20 × 20 meters sample were selected randomly and soil sampling was carried out from the center of each sample plot at a depth of 10 cm. Also the carbon dioxide emissions were measured at 35 points per stand. In order to investigate the effect of seasonal variation on Co2 emissions, measurements were done in both spring and autumn. The results showed that Robinia pseudoacacia increased potassium, nitrogen, phosphorus, electrical conductivity, organic carbon and nitrogen sequestration in soil compared to Pinus eldarica, but the acidity, organic matter, calcium carbonate, bulk density, moisture content, soil texture and carbon sequestration did not show any significant difference between two species.

Soil is a complex and dynamic biological system, and it still is difficult to determine the composition of microbial communities in soil. Most soil microorganisms are dormant, so their rate of respiration is low. However, their respiration can be stimulated by adding an easily decomposable substrate. Also, by adding a simple organic matter, respiration may rapidly increase to a maximum and remains at a constant rate for more than 4 h. Glucose is commonly used as a substrate because most soil microorganisms can readily utilize it as a carbon source. The substrate-induced respiration (SIR) method was modified and adapted to measure fungal, bacterial and total microbial contributions to glucose-induced respiration and the potentially active microbial biomass on decaying plant residues of different composition. Decomposing residues from natural and agricultural ecosystems were chopped and sieved to include the >1 mm fraction for routine SIR analyses on a continuous flow-through respiration system. Substrate induced respiration is a main factor for the assessment of the soil microbial activity. This technique is already used widely in soil microbial studies. Different factors such as the source of carbon, temperature and incubation may play a significant role in the amount of SIR. Therefore, optimizing the test conditions is one of the important criteria for SIR determination. For this purpose, statistical methods such as central composite design (CCD) and response surface method can be used as a useful tool for determining optimal conditions. This study was carried out to model and compare the effect of carbon source (glucose), temperature and incubation time on the SIR of forest and agricultural soils. In this research, 40 experiments were conducted for two soil types including agricultural soil (with relatively low organic matter content) and forest soil (with relatively high organic matter content). Soil samples were collected from the topsoil (0-20 cm) layer. In the laboratory, all visible roots were removed and the soil samples were divided into two parts. One part was kept in plastic bottles at 4°C for SIR analysis. And the rest was air dried in the shade at laboratory temperature for chemical and physical analysis. Electrical conductivity (EC) and pH were determined in saturated soil extract and organic carbon persent (%OC) was determined by di-chromate oxidation. Soil texture was determined using a Bouyoucos hydrometer in a soil suspension. Response surface methodology based on the central composite design was applied in modeling procedure. Different ranges of the independent variables including glucose (0.5-10 mg g-1), incubation time (1-10 hr), and temperature (15-30˚C) were used in central composite design experiments. Totally, 40 experiments based on the coded values of the independent variables were conducted for two soils. Experimental results indicated that the SIR in forest soil is two times greater than the agricultural soil, which may be related to the higher organic matter content and more microbial activity in this soil. Results also revealed the efficiency of the central composite design in predicting the SIR of forest (R2= 0.823) and agricultural (R2=0.919) soils. Among the three independent variables, the linear effect of temperature on the SIR were significant for both soils. However, the substrate (glucose) content has more significant effect in forest soil in comparison with agricultural soil which may be associated with the higher decomposable organic matter content of the forest soil. Glucose enhancement didn’t have significant effect on SIR alteration rate which can be attributed to low organic matter content in agricultural soil. Totally, with increasing time and temperature, the amount of SIR was significantly increased, however with increasing glucose, SIR amount was not significantly increased especially in the agricultural soil. In the forest soil, the process of SIR changes is clearly distinct in response to independent variables compared to agricultural soil. Maximum levels of the SIR in forest soil is clearly associated to the highest time and glucose levels. This indicates that increasing glucose and sufficient time in the forest soil, which contains high amounts of digestible organic matter, can stimulate microorganisms to decompose more organic matter and it outcome is increasing SIR. This study indicated the high efficiency of response surface methodology in SIR modeling for both forest and agricultural soils. However, the quantitative amounts of SIR were very different in two soils. The amounts of SIR in the forest soil were almost twice relative to agricultural soil. In the forest soil, the amounts of glucose and temperature were as the main variables in increasing SIR, while the temperature and time variables were more determinant in agricultural soil on it.

Evaluation of the ecological sustainability of different cropping systems is crucial to achieve sustainable agriculture. This evaluation is accessible via soil quality assessment. Therefore, to study the mid-term effects of different conservation tillage systems (no tillage and minimum tillage) and cover cropping on the biological indicators of soil quality, a factorial experiment in a completely randomized block design was conducted in Dastjerd region (Hamedan). Three levels of tillage (NT: no tillage, MT: minimum tillage and CT: conventional tillage) and two levels of cover cropping (C1: Lathyrus sativus and C2: no cover crop) were applied for four consecutive years. Soil sampling was performed in the fourth year of experiment in two steps (1- before cover crop plantation, and 2- after harvesting main crop) with three replications. Most indices (total organic carbon, active carbon, basal respiration, phosphatase activity) were significantly affected by cover crop, tillage systems and sampling time, as the highest values were obtained in NT-C1 in time 2 and the lowest ones in CT-C2 in time 1. For instance, after four years application of treatments, the mean active carbon content was increased from 927 mg/kg in the conventional tillage no cover crop to 1350 mg/kg in the conservation tillage systems cover crop. Therefore, conservation tillage practices combined with Lathyrus sativus cover crop were shown to be the most appropriate management for soil quality maintenance and improvement.

With increase in fire frequency in the Zagros forests, long term and short term evaluation of soil quality is very important. In this study, changes in some physico-chemical and microbial properties of soils were compared in short, medium and long-term after fire. For this purpose, three post-fire treatments were selected and labeled as TSF=1, TSF=3 and TSF=10 years after fire. In the nearest neighbor of each fire treatment a relevant unburned area was selected as the control and labeled as C1, C3 and C10, corresponding to the post-fire treatments. Soil sampling was performed from the depth of 0-20 cm in 4 replications. Overall, 24 composite soil samples were collected for post-fire treatments and their relevant controls. Some physicochemical and microbial properties were measured in soil samples. Results showed no changes in soil texture. Soil saturated moisture decreased for TSF=1, while it was recovered for TSF=3 and TSF=10. Soil bulk density decreased both in TSF=1 and TSF=3, while no changes were observed for TSF=10 compared to C10. There was a significant increase in soil pH, CEC, EC, and P for TSF=1 compared to C1. However, for TSF=3 and TSF=10, pH and CEC were recovered to the pre-fire level and soil P and EC were significantly lower than their controls. Soil organic carbon and N remained significantly lower than their control in all treatments. No significant change was observed in soil C:N ratio in any treatment. Microbial carbon biomass significantly decreased for TSF=1 compared to C1, while no significant changes were observed for TSF=3 and TSF=10 compared to C3 and C10, respectively. Soil induced respiration increased significantly for TSF=1, while it decreased significantly for TSF=3 and TSF=10 controls. Soil basal respiration significantly decreased in all post-fire treatments compared to their controls. Metabolic quotient significantly increased for TSF=1 and TSF=3, however, it recovered in TSF=10 to the pre-fire level. There was a significant decrease in microbial quotient for TSF=1, however, it increased significantly for TSF=3 and recovered to the pre-fire level for TSF=10. All the treatments were significantly discriminated using multivariate analysis (discriminant analysis). It was concluded that EC, N, CEC, and P were the most important physicochemical properties while microbial biomass carbon, basal and induced respiration, and microbial quotient were the most important microbial properties of soil for discriminating treatments.

Todaysoil pollution with heavy metals, especially cadmium due to its abundance in agricultural land has gained much more attention.In the present research, the effects of 0, 2 and 5 mg Cd kgˉ¹ soil were studied on soil respiration, mineralization of organic matter, urease activity and nitrification in a sandy clay loamsoil containing 2% vermicompost. Cadmium concentrations were examined in a factorial layout with a completely randomized design (CRD) with three replications under laboratory conditions during 3, 7, 31, 62 and 93 days. Before starting the experiment, the soil incubated for two weeks with vermicompost to achieve consistency in biological conditions. The results showed that cadmium had significant effect on the soil respiration and soil organic matter content but it did not have any effect on the specific activity of urease and soil nitrate concentration. On the other hand, the results revealed that incubation time had a significant influence on all determined parameters including specific activity of urease, soil respiration, the organic matter content and the nitrate concentration (P 0.01). The correlation coefficient between cadmium and examined parameters showed that cadmium treatment had no effect on urease activity and nitrification process and probably other soil properties affect the nitrification and urease activity in soil sample. Our results demonstratedthat among investigated factors soil respiration and organic carbon percentage are the most sensitive ones in treated cadmium concentrations.

IntroductionThe imbalance between anthropogenic emissions of CO2 and the sequestration of CO2 from the atmosphere by ecosystems has led to an increase in the average concentration of this greenhouse gas (GHG) in the atmosphere. Enhancing carbon sequestration in soil is an important issue to reduce net flux of carbon dioxide to the atmosphere. Soil organic carbon content is obtained from the difference between carbon input resulting from plant biomass and carbon losses the soil through different ways including soil respiration. CO2 emission varies largely during the year and is considerably affected by management type. The goal of this investigation was to study the effects of application of manure and chemical fertilizer on CO2 flux and carbon balance in agricultural system.
Materials and MethodsIn order to evaluate the carbon dynamics and effect of fertilizer and manure management on soil respiration and carbon budget for winter wheat, an experiment was conducted as a randomized complete block design with three replications in research field of Faculty of Agriculture of Ferdowsi University of Mashhad for two years of 2010-2011 and 2011-2012 . The experimental treatments were 150 and 250 kg chemical nitrogen (N1 and N2), manure (M), manure plus chemical nitrogen (F-M) and control (C). CO2 emission was measured six times during growth season and to minimize daily temperature variation error, the measurement was performed between 8 to 11 am. Chambers length and diameter were 50 cm and 30 cm respectively and their edges were held down 3 cm in soil in time of sampling so that no plant live mass was present in the chamber. Carbon budgets were estimated for two years using an ecological technique.
Results and DiscussionThe net primary production (NPP) was significantly higher in the F2 and F-M treatments with 6467 and 6294kg ha-1 in the first year and 6260 and 6410 kg ha-1 in the second year, respectively. The highest shoot to root ratio was obtained in F2 and the lowest was observed in control plot with 5.1 and 5.2 for first and second years, respectively. The trend of CO2 flux as 250, 220, 200, 170, 160 and 155 mg C m-2 h-1 was gained in the F-M, M, F2, F1 and root-excluded plots, respectively. In general, manure treatments had the highest heterotrophic respiration. The highest of annual soil respiration and heterotrophic respiration were also in M-F treatment with 3257 and 1150 kgC ha-1 for the first year and 3310, 1250 kgC ha-1 in second year, respectively. The annual NPP was 5000 and 5000 kgC ha-1 year-1 for M-F, 5077 and 5100 kgC ha-1 year-1 in F1 and 2065 and 1865 kgC ha-1 year-1 for the control treatment in 2010 and 2011, respectively. The range of annual net biome production (NBP) in the fertilizer and control treatments ranged from -400 to -150 kg C ha-1 year-1, suggesting the loss of carbon in the field. On the other hand, NBP in the M was 1400 and 1200 kgC ha-1 year-1 in 2010 and 2011, respectively and the M-F was 1300 and 1100 kgC ha-1 year-1 in 2010 and 2011, respectively.
ConclusionThe results of this experiment showed that in the wheat ecosystem, the carbon emission is higher than the carbon entry into the soil. The results also indicated that manure application in agro-ecosystems is a necessary approach to mitigate carbon losses in the winter wheat ecosystem and the results indicated a high correlation (> 0.9) between soil temperature and CO2 flux which was positive and exponential. Soil respiration increased under the influence of fertilizer treatments (both chemical fertilizer and manure) but, the main reason for the increased soil respiration under application of chemical fertilizers was autotrophic respiration. While both respiration of autotrophic and heterotrophic increased in manure treatment.