Relative contributions of taxonomic and functional diversity to the assembly of plant communities hosting endemic Dianthus species in a mountain steppe

Plant community assembly is the outcome of long-term evolutionary events (evident as taxonomic diversity; TD) and immediate adaptive fitness (functional diversity; FD); a balance expected to shift in favour of FD in 'harsh' habitats under intense selection pressures. We compared TD and FD responses along climatic and edaphic gradients for communities of two species (Dianthus pseudocrinitus and D. polylepis) endemic to the montane steppes of the Khorassan-Kopet Dagh floristic province, NE Iran. 75 plots at 15 sites were used to relate TD and FD to environmental gradients. In general, greater TD was associated with variation in soil factors (potassium, lime, organic matter contents), whereas FD was constrained by aridity (drought adaptation). Crucially, even plant communities hosting different subspecies of D. polylepis responded differently to aridity: D. polylepis subsp. binaludensis communities included a variety of broadly stress-tolerant taxa with no clear environmental response, but TD of D. polylepis subsp. polylepis communities was directly related to precipitation, with consistently low FD reflecting a few highly specialized stress-tolerators. Integrating taxonomic and functional diversity metrics is essential to understand the communities hosting even extremely closely related taxa, which respond idiosyncratically to climate and soil gradients.

The role of extracellular polymeric substances (EPS) in chemical-degradation of persistent organic pollutants in soil: A review

Persistent organic pollutants (POPs) in soil show high environmental risk due to their high toxicity and low biodegradability. Studies have demonstrated the degradation function of microbial extracellular polymeric substances (EPS) on POPs in various matrices. However, the degradation mechanisms and the factors that influence the process in soil have not been clearly illustrated. In this review, the characteristics of EPS were introduced and the possible mechanisms of EPS on degradation of organic pollutants (e.g., external electron transfer, photodegradation, and enzyme catalysis) were comprehensively discussed. In addition, the environmental conditions (e.g., UV, nutrients, and redox potential) that could influence the production and degradation-related active components of EPS were addressed. Moreover, the current approaches on the application of EPS in biotechnology were summarized. Further, the future perspectives of enhancement on degradation of POPs by regulating EPS were discussed. Overall, this review could provide a new thought on remediation of POPs by widely-existing EPS in soil with low-cost and minimized eco-disturbance.

Nitrogen fertilization rate affects communities of ammonia-oxidizing archaea and bacteria in paddy soils across different climatic zones of China

Nitrogen fertilization has important effects on nitrification. However, how the rate of nitrogen fertilization affects nitrification potential, as well as the communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), remains unclear. We performed a large-scale investigation of nitrification potential and ammonia-oxidizer communities in Chinese paddy fields at different nitrogen fertilization rates across different climatic zones. It was found that the nitrification potential at the high nitrogen fertilization rate (≥150 kg-1 N ha-1) was 23.35 % higher than that at the intermediate rate (100-150 kg-1 N ha-1) and 20.77 % higher than that at the low rate (< 100 kg-1 N ha-1). The nitrification potential showed no significant variation among different nitrogen fertilization rates across climatic zones. Furthermore, the AOA and AOB amoA gene abundance at the high nitrogen fertilization rate was 481.67 % and 292.74 % higher (p < 0.05) than that at the intermediate rate, respectively. Correlation analysis demonstrated a significant positive correlation between AOB abundance and nitrification potential. AOA and AOB community composition differed significantly among nitrogen fertilization rates. Moreover, soil NH4+ content, pH, water content, bulk density, and annual average temperature were regarded as key environmental factors influencing the community structure of ammonia-oxidizers. Taken together, the nitrogen fertilization rate had a significant impact on the communities of AOA and AOB but did not significantly alter the nitrification potential. Our findings provide new insights into the impact of nitrogen fertilization management on nitrification in rice paddy fields.

The role of topographic and soil factors on woody plant encroachment in mountainous rangelands: A mini literature review

Mountainous rangelands provide key ecosystem goods and services, particularly for human benefit. In spite of these benefits, mountain grasslands are undergoing extensive land-cover change as a result of woody plant encroachment. However, the influence of topographic and soil factors on woody plant encroachment is complex and has not yet been studied comprehensively. The aim of this review was to establish current knowledge on the influence of topographic and soil factors on woody plant encroachment in mountainous rangelands. To find relevant literature for our study on the impact of topographic and soil factors on woody plant encroachment in mountain rangelands, we conducted a thorough search on ScienceDirect and Google Scholar using various search terms. Initially, we found 27,745 papers. We narrowed down the search to include only 66 papers published in English that directly addressed the research area. The effect of slope aspect and slope position on woody plant encroachment is complex and dynamic, with no universal consensus on their impact. Some studies found higher woody plant encroachment on the cooler slopes, while others found increased woody plant encroachment on the warmer slopes. Slope gradient has a significant impact on woody plant encroachment, with steeper slopes tending to have more woody plant encroachment than gentle slopes. Soil texture and depth are important soil factors affecting woody plant encroachment. Coarse-textured soils promote the growth of woody plants, while fine-textured soils limit it. The effect of soil depth on woody plant encroachment remain unclear and requires further research. Soil moisture availability, soil nutrient content and soil microbial community are influenced by topography, which in turn affect the woody plant growth and distribution. In conclusion, the spread of woody plants in mountainous rangelands is a complex and dynamic process influenced by a range of factors. Further research is needed to fully understand the mechanisms behind these interactions and to develop effective strategies for managing woody plant encroachment in mountainous rangelands.

Greenhouse gas fluxes from different types of permafrost regions in the Daxing'an Mountains, Northeast China

Global warming will increase the greenhouse gas (GHG) fluxes of permafrost regions. However, little is known about the difference in GHG fluxes among different types of permafrost regions. In this study, we used the static opaque chamber and gas chromatography techniques to determine the fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in predominantly continuous permafrost (PCP), predominantly continuous and island permafrost (PCIP), and sparsely island permafrost (SIP) regions during the growing season. The main factors causing differences in GHG fluxes among three types of permafrost regions were also analyzed. The results showed mean CO2 fluxes in SIP were significantly higher than that in PCP and PCIP, which were 342.10 ± 11.46, 105.50 ± 10.65, and 127.15 ± 14.27 mg m-2 h-1, respectively. This difference was determined by soil temperature, soil moisture, total organic carbon (TOC), nitrate nitrogen (NO3--N), and ammonium nitrogen (NH4+-N) content. Mean CH4 fluxes were -26.47 ± 48.83 (PCP), 118.35 ± 46.93 (PCIP), and 95.52 ± 32.86 μg m-2 h-1 (SIP). Soil temperature, soil moisture, and TOC content were the key factors to determine whether permafrost regions were CH4 sources or sinks. Similarly, PCP behaved as the sink of N2O, PCIP and SIP behaved as the source of N2O. Mean N2O fluxes were -3.90 ± 1.71, 0.78 ± 1.55, and 3.78 ± 1.59 μg m-2 h-1, respectively. Soil moisture and TOC content were the main factors influencing the differences in N2O fluxes among the three permafrost regions. This study clarified and explained the differences in GHG fluxes among three types of permafrost regions, providing a data basis for such studies.

Nitrogen input on organic amendments alters the pattern of soil-microbe-plant co-dependence

The challenges of nitrogen (N) management in agricultural fields include minimizing N losses while maximizing profitability and soil health. Crop residues can alter N and carbon (C) cycle processes in the soil and modulate the responses of the subsequent crop and soil- microbe-plant interactions. Here, we aim to understand how organic amendments with low and high C/N ratio, combined or not with mineral N may change soil bacterial community and their activity on the soil. Organic amendments with different C/N ratios were combined or not with N fertilization as follows: i) unamended soil (control), ii) grass clover silage (GC; low C/N ratio), and iii) wheat straw (WS; high C/N ratio). The organic amendments modulated the bacterial community assemblage and increased microbial activity. WS amendment had the strongest effects on hot water extractable carbon, microbial biomass N and soil respiration, which were linked with changes in bacterial community composition compared with GC-amended and unamended soil. By contrast, N transformation processes in the soil were more pronounced in GC-amended and unamended soil than in WS-amended soil. These responses were stronger in the presence of mineral N input. WS amendment induced greater N immobilization in the soil, even with mineral N input, impairing crop development. Interestingly, N input in unamended soil altered the co-dependence between the soil and the bacterial community to favor a new co-dependence among the soil, plant and microbial activity. In GC-amended soil, N fertilization shifted the dependence of the crop plant from the bacterial community to soil characteristics. Finally, the combined N input with WS amendment (organic carbon input) placed microbial activity at the center of the interrelationships between the bacterial community, plant, and soil. This emphasizes the crucial importance of microorganisms in the functioning of agroecosystems. To achieve higher yields in crops managed with various organic amendments, it is essential to incorporate mineral N management practices. This becomes particularly crucial when the soil amendments have a high C/N ratio.

The driving mechanism of soil organic carbon biodegradability in the black soil region of Northeast China

The biodegradability of soil organic carbon (BSOC), defined as soil mineralization C per unit of soil organic carbon (SOC), is considered to be an important indicator of SOC stability and is closely related to the global C cycle. However, the magnitude and driving mechanism of BSOC in farmland remain largely unexplored, especially at the regional scale. Here, we conducted regional scale sampling to investigate latitude distribution pattern of BSOC and the relative contributions of biotic (soil micro-food web) and abiotic (climate and soil) drivers to BSOC in the black soil region of Northeast China. Results showed that BSOC declined with increasing latitude, which indicates that as the latitude increases, SOC becomes more stable in the black soil region of Northeast China. Over a range of latitude from 43°N to 49°N, BSOC was negatively correlated with soil micro-food web metrics of diversity (indicated by species richness), biomass and connectance, and soil factors of soil pH and clay content (CC), while it was positively correlated with climate factors of mean annual temperature (MAT), mean annual precipitation (MAP) and soil factor of soil bulk density (SBD). Among those predictors, soil micro-food web metrics were the most direct factors contributing to the variations of BSOC, which exerted the largest total effect on BSOC (-0.809). Collectively, our results provide convincing evidence that soil micro-food web metrics play a direct vital role in determining the distribution pattern of BSOC over a range of latitudes in the black soil region of Northeast China. This highlights the necessity of considering the role of soil organisms in regulating C dynamics in prediction of SOC mineralization and retention in the terrestrial ecosystem.

Long-Read Sequencing Analysis Revealed the Impact of Forest Conversion on Soil Fungal Diversity in Limu Mountain, Hainan

Soil fungi are essential to soil microorganisms that play an important role in the ecosystem's soil carbon cycle and mineral nutrient transformation. Understanding the structural characteristics and diversity of soil fungal communities helps understand the health of forest ecosystems. The transition from tropical rainforest to artificial forest greatly impacts the composition and diversity of fungal communities. Hainan Limushan tropical rainforest National Park has a large area of artificial forests. Ecologists have conducted in-depth studies on the succession of animals and plants to regenerate tropical rainforests. There are few reports on the diversity of soil fungi and its influencing factors in the succession of tropical rainforests in Limu Mountain. In this study, 44 soil samples from five different stands were collected in the tropical rainforest of Limushan, Hainan. High-throughput sequencing of rDNA in its region was used to analyze fungal communities and study their α and β diversity. Analysis of variance and multiple regression models was used to analyze soil variables and fungal functional groups to determine the effects of interaction between fungi and environmental factors. A total of 273,996 reads and 1290 operational taxonomic units (OTUs) were obtained, belonging to 418 species, 325 genera, 159 families, eight phyla, 30 classes, and 73 orders. The results showed that the composition of soil fungal communities in the five stands was similar, with ascomycetes accounting for 70.5% and basidiomycetes accounting for 14.7%. α and β diversity analysis showed that soil fungi in Limushan tropical rainforest had high abundance and diversity. Multiple regression analysis between soil variables and functional groups showed that organic matter, TN, TP, TK, and AK were excellent predictors for soil fungi. TP was the strongest predictor in all functional groups except soil saprotroph. Organic matter and total nitrogen were the strongest predictors of soil rot. The transformation from tropical rainforest to artificial forest in Limushan did not change the soil fungal community structure, but the richness and diversity of soil fungi changed. The forest transformation did not lead to decreased soil fungal abundance and diversity. Different vegetation types and soil properties affect the diversity of soil fungal communities. We found that Caribbean pine plantations can improve soil fungal diversity, while long-term Eucalyptus spp. plantations may reduce soil fungal diversity.

Electron transfer capacity of humic acid in soil micro and macro aggregates in response to mulching years

Plastic film mulching can help farmers meet food production requirements and even increase output. Although the environmental impact of this mulch has received attention, uncertainty remains about certain soil components and the course of its long-term effects. In particular, it is not clear whether the long-term use of mulching film will affect the electron transfer capacity (ETC) of natural organic matter in the soil. This study evaluated the electron-accepting capacity (EAC) and electron-donating capacity (EDC) of soil humic acid (HA) in different-size aggregates in response to different film mulching years (0-6 years). The EAC of HA in the soil showed a downward trend as mulching years increased, while the EDC fluctuated. EAC decline in microaggregates (MIA) was more significant than that of macroaggregates (MAA). Film mulching changes the physical and chemical properties of soil and the activity of enzymes, changes the chemical structure of HA, and ultimately affects HA electron transfer. In addition, compared with that in MAA, the chemical structure of soil HA in MIA has a stronger correlation with enzyme activity and ETC and thus is more significantly affected by mulching. These results provide an in-depth understanding of the role of HA in soil aggregates of different sizes in processes related to the agricultural soil environment under mulching conditions.

Factors influencing heavy metal availability and risk assessment of soils at typical metal mines in Eastern China

China exemplifies the serious and widespread soil heavy metal pollution generated by mining activities. A total of 420 soil samples from 58 metal mines was collected across Eastern China. Total and available heavy metal concentrations, soil physico-chemical properties and geological indices were determined and collected. Risk assessments were applied, and a successive multivariate statistical analysis was carried out to provide insights into the heavy metal contamination characteristics and environmental drivers of heavy metal availability. The results suggested that although the degrees of pollution varied between different mine types, in general they had similar contamination characteristics in different regions. The major pollutants for total concentrations were found to be Cd and As in south and northeast China. The availability of Zn and Cd is relatively higher in south China. Soil physico-chemical properties had major effect on metal availability where soil pH was the most important factor. On a continental scale, soil pH and EC were influenced by the local climate patterns which could further impact on heavy metal availability. Enlightened by this study, future remediation strategies should be focused on steadily increasing soil pH, and building adaptable and sustainable ecological system to maintain low metal availabilities in mine site soils.

Desertification reversion alters soil greenhouse gas emissions in the eastern Hobq Desert, China

Deserts cover more than 41% of the world's total land area and are significant in the terrestrial carbon cycle. The impact of desertification reversion and revegetation on the physical and chemical properties of soil is well studied; however, this study seeks to further the understanding of how they impact the flux of greenhouse gases (GHGs). Three sandy sites of different desertification reversal stages in the Hobq Desert were selected. Variations in the characteristics of GHG flux and its response mechanism to environmental hydrothermal conditions and soil properties were analyzed. Higher soil carbon dioxide (CO₂) emissions were observed in the growing season, whereas nitrous oxide (N₂O) emissions were mainly observed in the non-growing season. Methane (CH₄) absorption showed no obvious seasonal change. Linear regression analysis revealed that GHGs in the study area were positively correlated with total nitrogen and organic carbon content, and the number of microorganisms present in the soil. Hydrothermal factors were critical controllers of soil CO₂ emissions, but they did not majorly influence CH₄ and N₂O fluxes. The results illustrate the importance of desertification reversal and revegetation in mitigating climate change, and that deserts have a significant role in the global carbon cycle.

The community composition variation of Russulaceae associated with the Quercus mongolica forest during the growing season at Wudalianchi City, China

BACKGROUND

Most species of the Russulaceae are ectomycorrhizal (ECM) fungi, which are widely distributed in different types of forest ecology and drive important ecological and economic functions. Little is known about the composition variation of the Russulaceae fungal community aboveground and in the root and soil during the growing season (June-October) from a Quercus mongolica forest. In this study, we investigated the changes in the composition of the Russulaceae during the growing season of this type of forest in Wudalianchi City, China.

METHODS

To achieve this, the Sanger sequencing method was used to identify the Russulaceae aboveground, and the high-throughput sequencing method was used to analyze the species composition of the Russulaceae in the root and soil. Moreover, we used the Pearson correlation analysis, the redundancy analysis and the multivariate linear regression analysis to analyze which factors significantly affected the composition and distribution of the Russulaceae fungal community.

RESULTS

A total of 56 species of Russulaceae were detected in the Q. mongolica forest, which included 48 species of Russula, seven species of Lactarius, and one species of Lactifluus. Russula was the dominant group. During the growing season, the sporocarps of Russula appeared earlier than those of Lactarius. The number of species aboveground exhibited a decrease after the increase and were significantly affected by the average monthly air temperature (r = -0.822, p = 0.045), average monthly relative humidity (r = -0.826, p = 0.043), monthly rainfall (r = 0.850, p = 0.032), soil moisture (r = 0.841, p = 0.036) and soil organic matter (r = 0.911, p = 0.012). In the roots and soils under the Q. mongolica forest, the number of species did not show an apparent trend. The number of species from the roots was the largest in September and the lowest in August, while those from the soils were the largest in October and the lowest in June. Both were significantly affected by the average monthly air temperature (r2 = 0.6083, p = 0.040) and monthly rainfall (r2 = 0.6354, p = 0.039). Moreover, the relative abundance of Russula and Lactarius in the roots and soils showed a linear correlation with the relative abundance of the other fungal genera.

Vertical distribution and influencing factors of soil organic carbon in the Loess Plateau, China

Accurate analysis and evaluation of the spatial distribution and the primary factors that affect regional soil organic carbon (SOC) together make an important step in assessing carbon sequestration potential. However, little information is available on distribution of regional SOC in deep soil layers. To analyze the spatial distribution of and factors influencing SOC in a 500 cm soil profile, 1440 soil samples were collected from 90 sites on the Loess Plateau in China. The primary factors dominating the spatial distribution of SOC were quantified using principal component analysis with multiple linear regression (PCA-MLR) analysis. Results showed that the mean SOC of the 500 cm soil profile ranged from 1.20 to 3.37 g kg^-1, decreasing with increasing soil depth. The SOC in the deep soil profile decreased across the types of land use in the following order: forestland > cropland > grassland. Based on the factors analyzed in this study, land use accounted for 22% of the variation in SOC and was the dominant factor controlling the spatial distribution of organic carbon in shallow soils (0-100 cm); while soil factors (including soil clay, soil water content, and soil bulk density) were dominant in deep soil layers (200-500 cm), averagely accounting for 44.3%. The SOC stock in the 0-20 cm soil layer was 1.34 kg m^-2, accounting for only a small proportion (8%) of the total carbon in the entire 500 cm soil profile. SOC stock in the 200-500 cm layer was 7.62 kg m^-2, accounting for 44% of the total carbon in the 0-500 cm soil profile. This study demonstrates that a large amount of organic carbon is stored in deep soil, indicating that a better understanding of the reserves and cycles of deep soil carbon is a critical factor in the effective management of terrestrial ecosystems.

Assessment of the pollution and ecological risk of lead and cadmium in soils

The aim of the study was to assess the content, distribution, soil binding capacity, and ecological risk of cadmium and lead in the soils of Malopolska (South Poland). The investigation of 320 soil samples from differently used land (grassland, arable land, forest, wasteland) revealed a very high variation in the metal content in the soils. The pollution of soils with cadmium and lead is moderate. Generally, a point source of lead and cadmium pollution was noted in the study area. The highest content of cadmium and lead was found in the northwestern part of the area-the industrial zones (mining and metallurgical activity). These findings are confirmed by the arrangement of semivariogram surfaces and bivariate Moran's correlation coefficients. Among the different types of land use, forest soils had by far the highest mean content of bioavailable forms of both metals. The results showed a higher soil binding capacity for lead than for cadmium. However, for both metals, extremely high (class 5) accumulation capacities were dominant. Based on the results, the investigated soils had a low (Pb) and moderate (Cd) ecological risk on living components. Soil properties, such as organic C, pH, sand, silt, and clay content, correlated with the content of total and bioavailable forms of metals in the soils. The correlations, despite being statistically significant, were characterized by very low values of correlation coefficient (r = 0.12-0.20, at p ≤ 0.05). Therefore, the obtained data do not allow to define any conclusions as to the relationships between these soil properties. However, it must be highlighted that there was a very strong positive correlation between the total content of cadmium and lead and their bioavailable forms in the soils.

Discrepant responses of the electron transfer capacity of soil humic substances to irrigations with wastewaters from different sources

An increasing area of agricultural land is irrigated with wastewater worldwide due to the scarcity of fresh water resources. Whether wastewater irrigations can affect the electron transfer capacity (ETC) of natural organic matter in soils is unclear. In this study, we assess the responses of the electron-accepting capacity (EAC) and electron-donating capacity (EDC) of soil humic substances (HS) to irrigations with wastewaters from different sources. We show that the EAC of soil HS increases and the EDC of soil HS decreases after irrigation with domestic wastewater. Conversely, the EAC of soil HS decreases and the EDC of soil HS increases after irrigation with industrial wastewater. The EAC and EDC of soil HS exert no changes after irrigation with pharmaceutical wastewater. Irrigations with wastewaters from different sources can cause the distinct directions of changes in the activities of lignin peroxidase and laccase by altering the content of labile organic carbon, heavy metals or antibiotics in soils, thereby changing the chemical structures and finally the ETC of HS along different directions. These results can provide insights into the role of HS in environmentally relevant processes in agricultural soils under the context of wastewater irrigations.

Distinct taxonomic and functional composition of soil microbiomes along the gradient forest-restinga-mangrove in southeastern Brazil

Soil microorganisms play crucial roles in ecosystem functioning, and the central goal in microbial ecology studies is to elucidate which factors shape community structure. A better understanding of the relationship between microbial diversity, functions and environmental parameters would increase our ability to set conservation priorities. Here, the bacterial and archaeal community structure in Atlantic Forest, restinga and mangrove soils was described and compared based on shotgun metagenomics. We hypothesized that each distinct site would harbor a distinct taxonomic and functional soil community, which is influenced by environmental parameters. Our data showed that the microbiome is shaped by soil properties, with pH, base saturation, boron and iron content significantly correlated to overall community structure. When data of specific phyla were correlated to specific soil properties, we demonstrated that parameters such as boron, copper, sulfur, potassium and aluminum presented significant correlation with the most number of bacterial groups. Mangrove soil was the most distinct site and presented the highest taxonomic and functional diversity in comparison with forest and restinga soils. From the total 34 microbial phyla identified, 14 were overrepresented in mangrove soils, including several archaeal groups. Mangrove soils hosted a high abundance of sequences related to replication, survival and adaptation; forest soils included high numbers of sequences related to the metabolism of nutrients and other composts; while restinga soils included abundant genes related to the metabolism of carbohydrates. Overall, our finds show that the microbial community structure and functional potential were clearly different across the environmental gradient, followed by functional adaptation and both were related to the soil properties.

Evaluating the potential health risk of toxic trace elements in vegetables: Accounting for variations in soil factors

Vegetable crop consumption is one of the main sources of dietary exposure to toxic trace elements (TEs). A paired survey of soil and vegetable samples was conducted in 589 agricultural sites in the Youxian prefecture, southern China, to investigate the effect of soil factors on the accumulation of arsenic, cadmium, mercury, and lead in different vegetables. A site-specific model was developed to estimate the health risk from vegetable consumption. The TE concentration varied in different plant species, and rape can be cultivated in contaminated areas for its potential use in restricting the transfer of TE from soil to edible plant parts. The accumulation of TEs in vegetables was governed by multiple factors, mainly element interaction, metal availability (extractable CaCl₂ fraction), and soil pH. Soil Zn may promote Cd accumulation in vegetables when soil Cd/Zn ratio>0.02. Cadmium is a major hazardous component. About 80.8% of the adult populations consuming locally produced vegetables had a daily Cd intake risk above the safe standard. Among investigated vegetables, radish is potentially hazardous for populations because of its high consumption rate and high Cd content but low Zn accumulation. The consumption of radish cultivated in highly acidic soil (4<pH≤5) and high Cd contamination (CaCl₂-Cd=1.0mgkg^-1) had a significant probability (89.4%) to be above the safe standard; while this risk was significantly decreased to 8.9% in soil of near-neutral pH (6<pH≤7). The wide range of TE concentrations and soil factors suggests that a site-specific risk assessment is needed for better and safer vegetable production.

Plant physiological and soil characteristics associated with methane and nitrous oxide emission from rice paddy

Methane (CH4) and nitrous oxide (N2O) are important greenhouse gases causing global warming and climate change. Efforts were made to analyze the CH4 and N2O flux in relation to plant and soil factors from rice (Oryza sativa L.) paddy. Ten popularly grown rice varieties namely Rashmisali, Bogajoha, Basmuthi, Lalkalamdani, Choimora (traditional varieties); Mahsuri, Moniram, Kushal, Gitesh and Profulla (high yielding varieties = HYV) were grown during monsoon season of July 2006. The CH4 and N2O emissions were measured the date of transplanting onwards at weekly interval along with soil and plant parameters. The seasonal integrated CH4 and N2O emission (Esif) from rice ranged from 8.13 g m(-2) to 13.00 g m(-2) and 121.63 mg N2O-N m(-2) to 189.46 mg N2O-N m(-2), respectively. Variety Gitesh emitted less N2O and CH4 amongst all the rice varieties. Both CH4 and N2O emission exhibited a significant positive correlation with leaf area, leaf number, tiller number and root dry weight. Soil organic carbon of the experimental field was associated with both CH4 and N2O emission whereas nitrate-N content of soil was associated with N2O emission. Methane emission showed significant positive correlations with soil temperature and crop photosynthetic rate. Traditional rice varieties with profuse vegetative growth recorded higher CH4 and N2O fluxes compared to HYVs. Gitesh and Kushal having low seasonal CH4 and N2O emission with higher yield potential can be recommended as low greenhouse gas emitting rice varieties.