Role In Agroecosystems Research Articles

Depth-dependent Effects of Leguminous Crops on Soil Nitrogen-Fixing Microbial Communities Correlated with Carbon Degradation

Abstract Legumes play critical roles in agroecosystems by modulating nitrogen-fixing microorganisms to enhance soil fertility and promote crop productivity. Current research on the effects of legumes predominantly focuses on surface soil, lacking a comprehensive analysis of their overall impact across multiple soil layers and an in-depth understanding of associated microbial mechanisms. Here, the community structure of soil nitrogen-fixing microorganisms in three soil layers (0-20, 20-50, and 50-100 cm) under legume and non-legume cultivation was investigated through metagenomic sequencing. We found that only in topsoil (0-20 cm) legume treatment exhibited a significantly higher relative abundance of nitrogen-fixing genes than non-legume treatment. Under legume cultivation, the relative abundance of nitrogen-fixing genes was significantly higher in the topsoil layer than in deeper layers, whereas non-legume treatment displayed an inverse depth-dependent pattern. Combining soil physicochemical properties, the relative abundance of nitrogen-fixing genes correlated significantly with soil moisture, total carbon (TC), and dissolved organic carbon (DOC) content. Both TC and DOC were identified as key drivers of these genes. Subsequently, a similar depth-dependent pattern within the relative abundance of soil carbon degradation genes was found in response to the cultivation of both crops. The relative abundances of soil carbon degradation genes were negatively correlated with nitrogen-fixing genes under legume treatment individually, distinct from non-legume treatment. Our findings highlight the depth-dependent impact of legumes on nitrogen fixation and the critical interaction between soil carbon degradation and nitrogen fixation, providing insights into carbon management in legume cultivation practices to enhance nitrogen fixation in future agriculture.

Radiation-Tolerant Fibrivirga spp. from Rhizosphere Soil: Genome Insights and Potential in Agriculture.

The rhizosphere of plants contains a wide range of microorganisms that can be cultivated and used for the benefit of agricultural practices. From garden soil near the rhizosphere region, Strain ES10-3-2-2 was isolated, and the cells were Gram-negative, aerobic, non-spore-forming rods that were 0.3-0.8 µm in diameter and 1.5-2.5 µm in length. The neighbor-joining method on 16S rDNA similarity revealed that the strain exhibited the highest sequence similarities with "Fibrivirga algicola JA-25" (99.2%) and Fibrella forsythia HMF5405T (97.3%). To further explore its biotechnological potentialities, we sequenced the complete genome of this strain employing the PacBio RSII sequencing platform. The genome of Strain ES10-3-2-2 comprises a 6,408,035 bp circular chromosome with a 52.8% GC content, including 5038 protein-coding genes and 52 RNA genes. The sequencing also identified three plasmids measuring 212,574 bp, 175,683 bp, and 81,564 bp. Intriguingly, annotations derived from the NCBI-PGAP, eggnog, and KEGG databases indicated the presence of genes affiliated with radiation-resistance pathway genes and plant-growth promotor key/biofertilization-related genes regarding Fe acquisition, K and P assimilation, CO2 fixation, and Fe solubilization, with essential roles in agroecosystems, as well as genes related to siderophore regulation. Additionally, T1SS, T6SS, and T9SS secretion systems are present in this species, like plant-associated bacteria. The inoculation of Strain ES10-3-2-2 to Arabidopsis significantly increases the fresh shoot and root biomass, thereby maintaining the plant quality compared to uninoculated controls. This work represents a link between radiation tolerance and the plant-growth mechanism of Strain ES10-3-2-2 based on in vitro experiments and bioinformatic approaches. Overall, the radiation-tolerant bacteria might enable the development of microbiological preparations that are extremely effective at increasing plant biomass and soil fertility, both of which are crucial for sustainable agriculture.

Seasonal movements of small-island birds along habitat and elevation gradients highlights the conservation value of small-scale agroforests

Knowledge on species distributions and seasonal movement patterns within landscapes is important for understanding their ecology and roles in agroecosystems, and is critical for enabling their effective conservation and monitoring, particularly in small-island states where conservation resources are limited. We undertook bird surveys to examine species distributions across a range of agricultural land-use intensities and elevations on the Caribbean island of Grenada by collecting data over 6 repeated monthly surveys (3 wet season, 3 dry season) at sites located in a variety of habitats spread over 6–300 m elevation. We observed a gradual upslope increase in bird species diversity and abundance from the mid-wet season to the late-dry season, as well as a movement from reduced-canopy habitats to closed-canopy habitats in the dry season. The mid-elevation hillsides of Grenada consist of a diverse mosaic of closed canopy secondary forest patches, interspersed among more open agroforests and small-scale cropping and grazed areas. These agroecosystems appear to provide important habitats to birds throughout the year, especially open canopy agroforests in the wet season. We also found that open mixed agroforests contained a greater diversity of fruit, flower, and seed resources than closed canopy habitats such as secondary forest, cacao agroforests, young secondary forests, or dry forest scrub; and that plant food diversity was highest in the wet season. However, bird abundance significantly increased in closed canopy forest habitats during the dry season, suggesting that intact canopy forests provide important dry season habitat for many Grenadian birds, which may be particularly important for species in drier lowland areas experiencing more intensive agricultural land use and urban and resort development. Overall, this research demonstrates the importance of maintaining the functional connectivity of treed habitats at local and landscape scales for species conservation, as well as the contribution of diverse, small-scale agriculture to maintaining small-island bird communities.

Occurrence of black queen cell virus in wild bumble bee communities in China.

Wild bumble bees (Hymenoptera: Apidae) play a vital role in agro-ecosystems as important pollinators. However, they are threatened by virus pathogens that are widespread in honey bees. Previous studies have reported that viruses were able to be transmitted across bee genera and caused potential danger to wild bumble bees. China is a global biodiversity hotspot for bumble bees. However, the impact of viruses on the wild bumble bee communities remains elusive. Black queen cell virus (BQCV) is one of the most common honey bee viruses. Here, a total of 72 wild bumble bee samples from 17 geographic regions of China were tested for BQCV. Thirteen positive samples were identified and sequence comparison of partial capsid genes demonstrated a genetic identity of 99.69% to 100%. A phylogenetic tree analysis also showed a close relationship between 13 BQCV isolates and others from a variety of recorded hosts in China. Meanwhile, a distinct evolutionary branch of China isolates was formed when clustering isolates from worldwide bumble bee species. A correlation between BQCV and their geographic locations were observed (P < 0.05). This study not only provides the first evidence of widespread BQCV in wild bumble bee communities in China but also detects a distinct set of genetically identical or closely related BQCV variants that circulate and evolutionarily differ from other countries.

Role of Plant Growth Promoting Rhizobacteria (PGPR) as a Plant Growth Enhancer for Sustainable Agriculture: A Review

The rhizosphere of a plant is home to helpful microorganisms called plant growth-promoting rhizobacteria (PGPR), which play a crucial role in promoting plant growth and development. The significance of PGPR for long-term agricultural viability is outlined in this review. Plant growth processes such as nitrogen fixation, phosphate solubilization, and hormone secretion are discussed. Increased plant tolerance to biotic and abiotic stress, reduced use of chemical fertilizers and pesticides, and enhanced nutrient availability, soil fertility, and absorption are all mentioned as potential benefits of PGPR. PGPR has multiple ecological and practical functions in the soil’s rhizosphere. One of PGPR’s various roles in agroecosystems is to increase the synthesis of phytohormones and other metabolites, which have a direct impact on plant growth. Phytopathogens can be stopped in their tracks, a plant’s natural defenses can be bolstered, and so on. PGPR also helps clean up the soil through a process called bioremediation. The PGPR’s many functions include indole acetic acid (IAA) production, ammonia (NH3) production, hydrogen cyanide (HCN) production, catalase production, and more. In addition to aiding in nutrient uptake, PGPR controls the production of a hormone that increases root size and strength. Improving crop yield, decreasing environmental pollution, and guaranteeing food security are only some of the ecological and economic benefits of employing PGPR for sustainable agriculture.

Species-Specific Responses of Insectivorous Bats to Weather Conditions in Central Chile.

Insectivorous bats play a crucial role in agroecosystems by providing invaluable pest control services. With the escalating impacts of climate change, a comprehensive understanding of the environmental factors influencing bat activity becomes imperative for their conservation in agricultural landscapes. This study investigates the influence of weather conditions, specifically air temperature and relative humidity, on the timing activity and the relative abundance of five insectivorous bat species in central Chile. Data from automatic bat detectors and climatological stations are utilized for analysis. Our results unveil species-specific behaviors, with Tadarida brasiliensis exhibiting early emergence and extended activity periods compared to other bat species. Histiotus montanus and Lasiurus villosissimus display delayed onsets on more humid evenings, whereas Lasiurus varius and T. brasiliensis initiate activity earlier on colder nights compared to warmer ones. Relative humidity emerges as a key factor influencing relative abundance for all species, with more minutes with bat passes detected on drier nights. These findings suggest that global warming may influence observed bat behaviors, potentially altering foraging patterns and activity levels of these bat species. Moreover, as climate change continues, understanding the long-term impact on bat populations and their adaptive strategies is crucial for effective conservation measures. Further studies exploring these dynamics can provide valuable insights for shaping conservation efforts in the face of evolving environmental challenges.

The role of ant-mediated biological interactions in agroecosystems

Abstract Ants are common in agroecosystems, where they can significantly impact agricultural production and yield through interactions with other organisms. By regulating crop-damaging insects and occasionally pollinating flowers, ants provide ecosystem services. However, ants can harm crops through herbivory, tending hemipterans, eating beneficial arthropods, or vectoring disease. In this review, we provide an overview of the roles played by ants in agroecosystems through their interactions with other species. We categorize ant species interactions as beneficial or harmful, direct or indirect, and address the importance of context-dependency. In addition to reviewing the role of ant-mediated biological interactions in agroecosystems, we discuss management implications that should be considered when supporting or suppressing ants. This article provides new insights and suggests promising directions for utilizing ants to implement more sustainable agricultural practices in agroecosystems across the globe. We propose that ants play critical roles in agroecosystems through their interactions with other organisms and should be considered when making management decisions.

Assembly of cereal crop fungal communities under water stress determined by host niche

Crop-associated fungi play an important role in agroecosystems. However, a comprehensive understanding of the ecological mechanisms governing fungal community assembly is lacking. Here, we established a wheat (Triticum aestivum) and oat (Avena sativa) cropping system and sampled crop associated fungal communities under different water stresses. The results show that fungal community assembly in the soil-plant continuum is mainly determined by host niches rather than water stress and genotype. However, within the same host niche, water stress and genotype significantly influenced the assembly of fungal communities. This finding was further supported by the network complexity and dissimilarity-overlap analysis. Epiphytes and leaf endosphere exhibited a complex network structure, characterized by strong positive interactions among the members of the mycobiome. The network complexity of the phylloplane increased under drought stress. The analysis of microbial source tracking revealed that the fungi in the roots primarily originated from the bulk soil, while most fungi in the leaves originated from unknown sources under different water stress. In addition, crop mycobiome was governed by a few dominant taxa, with Sordariomycetes identified as an important biomarker taxon for roots and Trichosporonales for leaves. This study provides comprehensive empirical evidence on the assembly mechanisms of crop fungal communities.

Biotic homogenization, lower soil fungal diversity and fewer rare taxa in arable soils across Europe

Soil fungi are a key constituent of global biodiversity and play a pivotal role in agroecosystems. How arable farming affects soil fungal biogeography and whether it has a disproportional impact on rare taxa is poorly understood. Here, we used the high-resolution PacBio Sequel targeting the entire ITS region to investigate the distribution of soil fungi in 217 sites across a 3000 km gradient in Europe. We found a consistently lower diversity of fungi in arable lands than grasslands, with geographic locations significantly impacting fungal community structures. Prevalent fungal groups became even more abundant, whereas rare groups became fewer or absent in arable lands, suggesting a biotic homogenization due to arable farming. The rare fungal groups were narrowly distributed and more common in grasslands. Our findings suggest that rare soil fungi are disproportionally affected by arable farming, and sustainable farming practices should protect rare taxa and the ecosystem services they support.

Genomic insights of a native bacterial consortium for wheat production sustainability

The use of plant growth-promoting bacteria as bioinoculants is a powerful tool to increase crop yield and quality and to improve nitrogen use efficiency (NUE) from fertilizers in plants. This study aimed to bioprospecting a native bacterial consortium (Bacillus cabrialesii subsp. cabrialesii TE3T, Priestia megaterium TRQ8, and Bacillus paralicheniformis TRQ65), through bioinformatic analysis, and to quantify the impact of its inoculation on NUE (measured through 15N-isotopic techniques), grain yield, and grain quality of durum wheat variety CIRNO C2008 grown under three doses of urea (0, 120, and 240 kg N ha−1) during two consecutive agricultural cycles in the Yaqui Valley, Mexico. The inoculation of the bacterial consortium (BC) to the wheat crop, at a total N concentration of 123–225 kg N ha−1 increased crop productivity and maintained grain quality, resulting in a yield increase of 1.1 ton ha−1 (6.0 vs. 7.1 ton ha−1, 0 kg N ha−1 added, 123 kg N ha−1 in the soil) and of 2.0 ton ha−1 (5.9 vs. 7.9 ton ha−1, 120 kg N ha−1 added, 104 kg N ha−1 in the soil) compared to the uninoculated controls at the same doses of N. The genomic bioinformatic analysis of the studied strains showed a great number of biofertilization-related genes regarding N and Fe acquisition, P assimilation, CO2 fixation, Fe, P, and K solubilization, with important roles in agroecosystems, as well as genes related to the production of siderophores and stress response. A positive effect of the BC on NUE at the studied initial N content (123 and 104 kg N ha−1) was not observed. Nevertheless, increases of 14 % and 12.5 % on NUE (whole plant) were observed when 120 kg N ha−1 was applied compared to when wheat was fully fertilized (240 kg N ha−1). This work represents a link between bioinformatic approaches of a native bacterial inoculant and the quantification of its impact on durum wheat.

LIFE TABLE ATTRIBUTES AND FEEDING EFFICIENCY OF OENOPIA SAUZETI (MULSANT) (COLEOPTERA: COCCINELLIDAE) FED ON APHID (APHIS GOSSYPII)

Ladybird beetles are play vital role in agroecosystem due to successful and efficient feeding behavior against aphids, the present research experiment was carried to find out the life history and feeding efficacy of oenopiasauzetifed on Aphis gossypii,at the laboratory of Biological Control, integrated pest management programme (IPMP), National Agriculture Research Centre (NARC), Islamabad. The results of the experiment revealed that the mean developmental time of immature stage 3rd and 4th instar have a significant difference with 3.72±0.11 and 3.87±0.036 days, while the egg to adult emergence was 39±0.35 days. The longevity has significant difference in male and female with the higher values at female 34.0 days. Similarly, the feeding efficiency was maximum in O. sauzeti females which feeds on 2227.1 mean number of Aphis gossypii, while the (409.25±1.42) mean numbers of aphids were consumed by larva. The maximum aphid consumption was observed at 4th instar larva (198.98±0.51 aphid) followed by 3rd instar larva (128.57±0.59 aphid). The mean oviposition time of O. sauzetion A. gossypii was recorded as 21.36 days and average eggs laid female-1 day-1 was 20.53, while the total laid eggs given by a female were 253.60. The apparent mortality (100qx) was maximum at egg stage (24) and the mortality survival ratio (MSR) was highest at pupal stage (0.53), similarly, the indispensable mortality (IM) was also observed high at pupal stage. The maximum survival fraction (Sx) was observed at the 4th larval stage (0.91) and the maximum life expectancy (ex) was observed at 1st larval instar (4.51) days. The total killer power (k-value) of the O. sauzetifor the complete generation was 0.49. This will help to develop an ecofriendly managing approach for the minimizing the aphids infestationin economical important crops.

AntTracker: A low-cost and efficient computer vision approach to research leaf-cutter ants behavior

Leaf-cutter ants play a crucial role in agroecosystems, and understanding their behavior is key to developing effective damage control strategies. While several tracking solutions exist for ants in controlled environments or on aerial images, accurately measuring ant behavior in the wild remains a challenge. In this work, we propose a three-stage processing pipeline that segments individual ants, tracks their movement, and classifies whether they are carrying a leaf using a convolutional neural network. The output of the pipeline includes a timestamped record of the activity on the trail, accounting for parameters such as ant velocity, size and if it is going from or to the nest. We use the recently developed portable device AntVideoRecord to register video of a selected ant trail. To validate our approach, we collected a labeled dataset and evaluated each stage using standard metrics, achieving a median F2 score of 83% for segmentation, MOTA of 97% for tracking and F1 of 82% for detecting ants carrying a leaf. We then carried out a larger use case in the wild, demonstrating the effectiveness of our approach in capturing the intricate behaviors of leaf-cutter ants. We believe our method has the potential to inform the development of more effective ant damage control strategies in agroecosystems.

Species diversity of centipedes during a year-round survey at two vineyard sites in Northern Israel

Abstract Centipedes (Chilopoda) are mainly predators, which play essential roles in agroecosystems. In this work, pitfall traps were placed monthly during 1998 in two sites of vineyards in Northern Israel: the Geshur and Ramat Magshimim vineyards. The present research refers to the centipedes that were caught in these traps. Specimens of seven species of centipedes were caught in this work. Four centipede species were found in both vineyard sites: Thereuonema syriaca Verhoeff 1905, Scutigera coleoptrata (Linnaeus, 1758), Scutigeridae gen. species, and Hessebius barbipes (Porath, 1893). Two species were found in the Geshur, and not in the Ramat-Magshimim vineyard: Lithobius (Monotarsobius) sp., and Harpolithobius halophilus Verhoeff, 1941. One species was found in the Ramat-Magshimim, and not in the Geshur vineyard: Lithobius carinatus L. Koch, 1862. In the Geshur vineyard, 52 specimens of 6 centipede species were found. In the Ramat Magshimim vineyard, 20 specimens of 5 centipede species were detected. These differences are probably related to the Geshur vineyard being close to natural Mediterranean shrubland, while the Ramat Magshimim vineyard is situated between cultivated areas.

The Community Structure of Ants in Hordeum Vulgare and Grass Mixture Conditions in the Southwestern Part of Slovakia

Ants are an important bioindicative group that plays a significant role in agroecosystems. As a result of interspecific competition for food, they can displace native species. The aim of the research was to assess the influence of environmental variables (soil pH, soil moisture, potassium, phosphorus and nitrogen) and the influence of seasons on the dispersion of ants. Between 2018 and 2020, while investigating different types of crops, we recorded 864 individuals belonging to 9 species and 2 unspecified species (sp.). The dispersion of ants was affected by moisture, soil pH, phosphorus, potassium and nitrogen. In addition, an increase in value of the average number of individuals during spring and summer months was confirmed. We confirmed an increasing number of ant individuals with increasing values of potassium, phosphorus, nitrogen and soil moisture. A neutral pH of soil is optimal for ants. Our results yielded new information indicating that agricultural intensification negatively affects ants which are important for the production of biomass and reduces the number of pests which also affect crop yields.

Abundant bacterial subcommunity is structured by a stochastic process in an agricultural system with P fertilizer inputs

Soil microorganisms play an important role in agroecosystems and are related to ecosystem functioning. Nevertheless, little is understood about their community assembly and the major factors regulating stochastic and deterministic processes, particularly with respect to the comparison of abundant and rare bacterial subcommunities in agricultural systems. Here, we investigated the assembly of abundant and rare bacterial subcommunities in fields with different crops (maize and wheat) and phosphorus (P) fertilizer input at three different growth stages on the Loess Plateau. The high-throughput sequencing dataset was assessed using null and neutral community models. We found that abundant bacteria was governed by the stochastic process of homogenizing dispersal, but rare bacterial subcommunity was predominant by deterministic processes in maize and wheat fields due to broader niche breadths of abundant species. Soil nitrogen (N) and P also determined the assembly of abundant and rare soil subcommunities. The relative abundance and composition of the abundant and rare bacterial subcommunities were also influenced by soil nutrients (soil available P (AP) and NO3−-N) and agricultural practices (P fertilization and crop cultivation). In addition, the abundant bacterial community was more susceptible to P fertilizer input than that of the rare bacteria, and a higher relative abundance of abundant bacteria was observed in the P70 treatment both in maize and wheat soils. The microbial co-occurrence network analysis indicated that the maize field and low nutrient treatment exhibited stronger associations and that the abundant bacteria showed fewer interconnections. This study provides new insights toward understanding the mechanisms for the assembly of abundant and rare bacterial taxa in dryland cropping systems, enhancing our understanding of ecosystem diversity theory in microbial ecology.

The influence of field margin characteristics on syrphid abundance

Field margins have an important ecological role in agroecosystems including hosting beneficial insect such as syrphids. However, little is known of syrphid preferences for different types of field margins. Syrphids were sampled in field margins in an organic agroecosystem to test the hypothesis that syrphid abundance in field margins depends not only on the floral resource abundance but also on field margin component type, field margin complexity, and adjacent land-use type. Floral resource abundance had the greatest influence on the number of syrphids surveyed. Field margin characteristics were deemed to effect syrphid abundance both independently of their effect on floral resources and by altering floral resource abundance. Syrphids were more abundant in field margins adjacent to cropped fields than those adjacent to grazed fields or roads. More syrphids were found in ditch components than in tree or grass strip components. The influence of floral resources on syrphid abundance varied depending on their botanical families, although no significant differences were observed for the effect of botanical family floral resource index on syrphid abundance. These findings demonstrate that field margin characteristics play an important role in facilitating plant–syrphid interactions and offer an insight in agroecosystem management for the promotion of beneficial insects. The influence of field margin characteristics on other beneficial insect groups should also be investigated.

Symbiotic Nodule Development and Efficiency in the Medicago truncatula Mtefd-1 Mutant Is Highly Dependent on Sinorhizobium Strains.

Symbiotic nitrogen fixation (SNF) can play a key role in agroecosystems to reduce the negative impact of nitrogen fertilizers. Its efficiency is strongly affected by the combination of bacterial and plant genotypes, but the mechanisms responsible for the differences in the efficiency of rhizobium strains are not well documented. In Medicago truncatula, SNF has been mostly studied using model systems, such as M. truncatula A17 in interaction with Sinorhizobium meliloti Sm2011. Here we analyzed both the wild-type (wt) A17 and the Mtefd-1 mutant in interaction with five S. meliloti and two Sinorhizobium medicae strains. ETHYLENE RESPONSE FACTOR REQUIRED FOR NODULE DIFFERENTIATION (MtEFD) encodes a transcription factor, which contributes to the control of nodule number and differentiation in M. truncatula. We found that, in contrast to Sm2011, four strains induce functional (Fix+) nodules in Mtefd-1, although less efficient for SNF than in wt A17. In contrast, the Mtefd-1 hypernodulation phenotype is not strain-dependent. We compared the plant nodule transcriptomes in response to SmBL225C, a highly efficient strain with A17, versus Sm2011, in wt and Mtefd-1 backgrounds. This revealed faster nodule development with SmBL225C and early nodule senescence with Sm2011. These RNA sequencing analyses allowed us to identify candidate plant factors that could drive the differential nodule phenotype. In conclusion, this work shows the value of having a set of rhizobium strains to fully evaluate the biological importance of a plant symbiotic gene.

Where the straw-derived nitrogen gone in paddy field subjected to different irrigation regimes and straw placement depths? Evidence from 15N labeling

Straw-derived N is an organic N source, that plays an important role in agroecosystems. However, quantitatively tracing the release and fate of exogenous straw-derived N in a rice-soil system amended by irrigation regime and straw placement depth is poorly understood. The objectives of this study were to determine the release and fate of straw-derived N in the rice-soil system under different irrigation regimes and straw placement depths. 15N-labeled rice straw was used for two consecutive years in a field experiment in Northeast China, and four treatments were established: (i) controlled irrigation + shallow straw return (5 cm depth, CSD1); (ii) controlled irrigation + deep straw return (15 cm depth, CSD2); (iii) flooded irrigation + shallow straw return (5 cm depth, FSD1); and (iv) flooded irrigation + deep straw return (15 cm depth, FSD2). We found that the temporal patterns of straw N release were best described by the one-pool model, which was helpful to predict the straw-derived N fluxes during straw decomposition under different irrigation regimes and straw placement depths. Controlled irrigation and shallow straw placement depth increased the straw N release rate, which was consistent with their effects on straw mass loss, especially in the first rice season, showing a decreasing order of CSD1 > CSD2 > FSD1 > FSD2. Irrigation regime and straw placement depth significantly affected the fate of straw-derived N in the rice-soil system. Controlled irrigation will not only increase plant utilization rates of straw-derived N at different straw placement depths but also promote soil sequestration of straw-derived N and reduce the loss of straw-derived N. Additionally, we also found that placing straw at a shallower depth can also increase straw-derived N utilization by plants. Coupling controlled irrigation and placing straw at a shallower depth (CSD1) resulted in the highest utilization of straw-derived N by plants. However, it is worth noting that placing straw at a shallower depth also increases the loss of straw-derived N, which may increase the risk of environmental pollution in a soil-rice system. This study expanded the theory of straw N release and effective utilization in agroecosystems, which is helpful to better predict gross N fluxes and fates of straw-derived N in the agroecosystem to formulate a scientific and reasonable mode of field management with straw return.

Modelling direct field nitrogen emissions using a semi-mechanistic leaching model newly implemented in Indigo-N v3

Nitrogen plays a major role in agroecosystems as the key nutrient in agricultural production as well as a source of different emissions, which exceed currently planetary boundaries. N losses, conditioned by both pedoclimatic conditions and agricultural strategies (e.g. rotations, fertilisation), predominantly take the form of ammonia (NH3) volatilisation, nitrate (NO3) leaching, nitrification-driven nitric oxide (NOx) emission to air, and denitrification-driven nitrous oxide (NOx and N2O) emissions to air. The multiplication of initiatives and studies on nitrogen modelling resulted in a broad offer of complex simulation models (Tier 3) on one extreme of the gradient between feasibility and integration of processes. On the other side, a multiplication of initiatives has led to a broad offer of causal indicators in the form of proxies and considering one or a few input variables (Tier 1). A relevant compromise between those extremes lies in the development of operational models using a restricted number of parameters and input variables (Tier 2). Here, we propose a new semi-mechanistic operational model for the estimation of direct field N emissions (NH3, NO3, NOx and N2O) from contrasting agricultural situations: the Indigo-N v3 (I-N3) model. The gaseous emissions are based on Tier 1 (NOx) and Tier 2 (NH3, N2O) methods taken from the literature, with some enhancements, while we developed a totally new semi-mechanistic approach for nitrate leaching. A comparison of I-N3 outputs was performed with measurements of nitrate leaching in three countries (15 arable fields in France, 3 sugar cane fields at Reunion Inland, and 5 cropped fields in Kenya) and showed a reasonable predictive quality for temperate arable fields, and for some of the tropical fields (1 in Reunion and 3 in Kenya). It also performed better than the previous version of Indigo-N (IN-2) and the SALCA/SQCB models. In comparison with previous Tier 2 models, the newly developed Indigo-N v3 presents an original position on the gradient between integration of processes and feasibility of the simulation of processes. Another novelty of I-N3 lies in its broad scope, designed to be valid for temperate and non-temperate crops, including annual field crops, short-cycle vegetables, temporary grasslands and perennial grasses (such as sugarcane, miscanthus or switchgrass). Parameterisation and validation should be continued for further crops, such as associations and short cycle vegetables.

Pollinators in tropical ecosystems of Southern India with emphasis on the native pollinators Apis cerana indica and Tetragonula iridipennis

Ecosystems are rapidly urbanizing at the global and regional scales, particularly in the tropics, which has deleterious effect on hymenopteran pollinators. Based on the literature spanning multiple disciplines including ecology, pollination, agriculture, agroecology and entomology, this review deliberates on the pollinators and their global decline. Also, it turns the focus on honey bees and their role in agroecosystem. Relevant information from melissopalynology is brought together and the gaps and directions of future research on conservation and management of honey bees in tropical peninsular India are discussed. Focus is on the two species of the hived native Apis cerana indica F., and Tetragonula iridipennis Smith (Hymenoptera: Apidae), as these play a major role in transforming existing agricultural landscapes into agroecosystems, benefitting the farmers and maintaining ecological balance in tropical peninsular India. This review brings to the fore the fact that there is a tangible gap in reports and long-term studies of many native pollinators and in particular the two hived honey bees. Most studies present in a thorough manner visual observations of pollinators (bees) on plants but rarely combine them with quantifying the resources gathered from the plants, especially pollen. This combined approach is especially important to understand the hymenopteran pollinators from the purview of the pollination service they provide. It can be concluded that there is a pressing requirement for long-term observations along these lines with quantifiable pollen and vegetation data to arrive at meaningful plant-pollinator networks that are essential for conservation and management of the native Asiatic honey bees as pollinators.