Fertilization Rapidly Alters the Feeding Activity of Grassland Soil Mesofauna Independent of Management History

Effect of long-term nutrient managements on biological and biochemical properties of semi-arid tropical Alfisol during maize crop development stages

Quantitative information on mineralization of soil organic carbon (SOC) under different long-term nutrient management practices is essential for better assessment of carbon (C) loss from soil. With an aim to evaluate long-term nutrient management effects on C mineralization kinetics in soils, a laboratory incubation study was conducted with soils collected from different depths (0–15, 15–30, 30–60, and 60–100 cm) of a 46-year old maize-wheat experiment. The treatments in the field involved long-term application of 100% N, 100% NP, 100% NPK, 150% NPK, 100% NPK + FYM (farmyard manure), and an unfertilized control. Long-term application of fertilizers significantly (p < 0.05) influenced organic C concentration and C mineralization kinetics in soil. Integrated application of inorganic fertilizers and organic manure (100% NPK + FYM) resulted in greater SOC accumulation and higher potentially mineralizable C in soil compared to other treatments. The microbial biomass carbon (MBC), basal soil respiration (BSR), carbon mineralization (Cmin), and microbial quotient (qMic) values were significantly higher under integrated application of NPK and FYM in maize-wheat system. The results showed that long-term application of FYM along with inorganic fertilizer enhanced SOC pool compared to solitary application of mineral fertilizers.

An experiment was conducted to study the yield components and yield of Boro rice (cv. BRRI dhan63) under different nutrient and weed management strategies. The experiment was laid out in a two factor randomized complete block design with three replications consisting of four nutrient management strategies viz. cowdung 10 t ha-1, recommended dose of chemical fertilizer (urea, triple super phosphate, muriate of potash, gypsum and zinc sulphate @ 258, 101, 120, 113 and 11.5 kg ha-1, respectively), 75% recommended dose of chemical fertilizer + cowdung 5 t ha-1 and 50% recommended dose of chemical fertilizer + cowdung 10 t ha-1; and five weed management strategies viz. weedy check, hand weeding twice at 15 and 30 days after transplanting (DAT), pre-emergence herbicide Panida at 3 DAT, post-emergence herbicide Granite at 10 DAT and Panida at 3 DAT + Granite at 10 DAT. Yield components and yield of Boro rice cv. BRRI dhan63 were significantly influenced by nutrient and weed management strategies. Application of 75% recommended dose of chemical fertilizer + cowdung 5 t ha-1 showed the highest values for all yield components and produced the highest grain yield (6.24 t ha-1) while among the weed management strategies, Panida at 3 DAT + Granite at 10 DAT produced the highest grain yield (6.39 t ha-1) and the interaction of this two treatments also produced the highest grain yield (6.97 t ha-1). Among the different nutrient management strategies, cowdung 10 t ha-1 produced the lowest values of most of the yield contributing characters and grain yield (4.92 t ha-1) while in case of weed management strategies weedy check produced the lowest grain yield (4.55 t ha-1) and the interaction of this two treatments also produced the lowest grain yield (4.05 t ha-1). Therefore, it can be concluded that 75% recommended dose of chemical fertilizer + cowdung 5 t ha-1 combined with Panida at 3 DAT + Granite at 10 DAT can be practiced for the cultivation of Boro rice cv. BRRI dhan63 to obtain the highest grain yield.

Nitrogen budgeting of rice-wheat cropping system under long-term nutrient management in an Inceptisol of north India

Organic manure application has its significant impact on the soil health. Low organic matter in tropical soils is a major factor contributing to their poor productivity. Soil properties have been continuously influenced by the management practices and land uses, in which latter one has been, identified as profound influence on soil properties especially on soil organic carbon. A thirteen year experiment on soybean based cropping system in a vertisol of central india under organic farming was used for this investigation An investigation was carried out on “Soil organic carbon dynamics under long-term nutrient management in soybean based cropping system” at the Indian Institute of Soil Science, Bhopal on an on-going research project on organic farming. The effect of organic, integrated and inorganic nutrient management was assessed in three cropping systems viz. soybean (JS 335)-wheat (Malwa Shakti), soybean-mustard (Pusa Bold) and soybean-gram (JG 130) on aggregate size fractions, carbon content in aggregate as well as soil organic carbon pools dynamics on a split plot experimental design with three replications. The study relevant to dynamics of soil organic carbon pools revealed higher content of soil organic carbon, labile carbon, water soluble carbon, SMBC as well as dehydrogenase activity that varied between 1.04 and 0.86 percent; 440 and 538 mg kg-1, 52.97 and 70.43; 288 and 375 mg kg-1, 88 and 137 µg TPF g-1 soil d-1, respectively in surface 0-15 cm soil under organic nutrient management.

We studied the effect of soil tests and crop response-based long-term nutrient management on yield sustainability and soil health under rice-rice system in a Typic Haplustalf. The experiment was designed in randomized block design having five treatments, viz, control, the recommended dose of fertilizer (RDF), STCR–NPK for target yield of 6 t ha–1 for kharif rice and 5 t ha–1 for rabi rice (STCR–NPK6), STCR–NPK for 7 t ha–1 for kharif rice and 6 t ha–1 for rabi rice (STCR–NPK7), and STCR–IPNS for 7 t ha–1 for kharif rice and 6 t ha–1 for rabi rice (STCR–IPNS7), and these treatments were replicated thrice. The 10-year mean data suggested that minimum yield was observed from control whereas highest was achieved in STCR–IPNS7 in both kharif as well as rabi seasons. The highest sustainable yield index (SYI) was 0.93 in kharif and 0.77 in rabi rice was observed under STCR–IPNS7, and lowest in control. Soil fertility status revealed that disregard for external application of nutrients resulted in depletion of 108 kg N, 11.6 kg P, and 200 kg K ha-1 and intensity of nutrient depletion was lowest in STCR–IPNS followed by STCR–NPK7, STCR–NPK6, and RDF. The urease, phosphatase, and dehydrogenase activities and microbial biomass C were found to be higher in STCR–IPNS when compared with other nutrient management practices while minimum values were recorded in the control.

Change in phosphorus availability, fractions, and adsorption-desorption by 46-years of long-term nutrient management in an Alfisol of eastern India

Effects of long-term fertilization on soil gross N transformation rates and their implications

BackgroundThe 16S rRNA gene-based amplicon sequencing analysis is widely used to determine the taxonomic composition of microbial communities. Once the taxonomic composition of each community is obtained, evolutionary relationships among taxa are inferred by a phylogenetic tree. Thus, the combined representation of taxonomic composition and phylogenetic relationships among taxa is a powerful method for understanding microbial community structure; however, applying phylogenetic tree-based representation with information on the abundance of thousands or more taxa in each community is a difficult task. For this purpose, we previously developed the tool VITCOMIC (VIsualization tool for Taxonomic COmpositions of MIcrobial Community), which is based on the genome-sequenced microbes’ phylogenetic information. Here, we introduce VITCOMIC2, which incorporates substantive improvements over VITCOMIC that were necessary to address several issues associated with 16S rRNA gene-based analysis of microbial communities.ResultsWe developed VITCOMIC2 to provide (i) sequence identity searches against broad reference taxa including uncultured taxa; (ii) normalization of 16S rRNA gene copy number differences among taxa; (iii) rapid sequence identity searches by applying the graphics processing unit-based sequence identity search tool CLAST; (iv) accurate taxonomic composition inference and nearly full-length 16S rRNA gene sequence reconstructions for metagenomic shotgun sequencing; and (v) an interactive user interface for simultaneous representation of the taxonomic composition of microbial communities and phylogenetic relationships among taxa. We validated the accuracy of processes (ii) and (iv) by using metagenomic shotgun sequencing data from a mock microbial community.ConclusionsThe improvements incorporated into VITCOMIC2 enable users to acquire an intuitive understanding of microbial community composition based on the 16S rRNA gene sequence data obtained from both metagenomic shotgun and amplicon sequencing.

Ecological research based on both species and their traits helps us understand the mechanisms structuring ecological communities. Our aim was to dismantle the effects of environmental variables measured at multiple spatial scales on the taxonomic and functional trait composition of benthic macroinvertebrate communities and to clarify the relationship between the environment and communities in high-latitude streams. Traits were combined into unique trait combinations (site-by-traits matrix), called hereafter the overall trait composition of macroinvertebrate communities, and then the matrix was decomposed into progressively smaller parts of individual traits (site-by-individual trait matrix). The effects of variables from different spatial scales on the variation in the overall trait matrix, decomposed trait matrices, and taxonomic data were analyzed using redundancy analysis and partial linear regression modeling. Our analyses indicated that: 1) the taxonomic composition of communities was more closely associated with factors measured at larger spatial scales, and the trait composition of communities was more closely associated with factors measured at smaller spatial scales, even within 1 drainage basin; 2) decomposing overall trait composition to its individual components of single traits revealed important patterns related to the potential causal factors; and 3) the abundances of organisms exhibiting different traits may be linked strongly to different environmental variables operating at different spatial scales. Our findings highlight the benefits of describing both the taxonomic and trait composition of communities when exploring the drivers of community composition. They also have direct applications in monitoring the vulnerability of high-latitude streams to future environmental changes.

Summary1. We investigated the seasonal variation of biological traits and the influence of interannual rainfall variability on this pattern. Using long‐term survey data (6–19 years) from an intermittent and a perennial stream in the Mediterranean‐climate region of northern California, we examined 16 fuzzy‐coded biological traits (e.g. maximum size, life cycle duration, and mode of respiration).2. Seasonal habitat variability is higher in the intermittent stream than in the perennial stream. During the winter and spring wet‐season both streams flood; however, during the summer dry‐season, the intermittent stream forms isolated pools in (occasionally drying completely).3. Seasonal habitat variability influenced both taxonomic and biological trait composition. Distinct taxonomic communities were present in each season, particularly in the intermittent stream. The intermittent stream also exhibited more seasonal variation in biological traits than the perennial stream.4. Despite statistically significant seasonal variation, trait composition was relatively stable among seasons in comparison with taxonomic composition and abundance. Taxonomic composition varied considerably between seasons, because of high seasonal and interannual replacement of taxa resulting from seasonal habitat changes.5. The seasonality of taxonomic composition and abundance was sensitive to interannual rainfall variability. In dry years, the taxonomic composition of communities was more similar between seasons than in wet years, while trait composition was relatively insensitive to rainfall variability.6. Despite high seasonal variation in abundance and taxonomic composition, biological traits of aquatic macroinvertebrates varied less and exhibited seasonal stability, which may be a result of the unpredictability and harshness of stream environments.

Understanding the drivers of community stability in times of increasing anthropogenic pressure is an urgent issue. Biodiversity is known to promote community stability, but studies of the biodiversity–stability relationship rarely consider the full complexity of biodiversity change. Furthermore, finding generalities that hold across taxonomic groups and spatial and temporal scales remains challenging because most investigations have narrow taxonomic, spatial, and temporal scopes. We used organismal data collected through the National Ecological Observatory Network (NEON) at sites across the contiguous United States to evaluate linkages between community stability and biodiversity change for four taxonomic groups: small mammals, ground beetles, fish, and freshwater macroinvertebrates. We defined community stability as constancy of aggregate species' abundance. We quantified change in biodiversity as (1) dissimilarity in community taxonomic and functional composition and species replacement and richness change components of that dissimilarity and (2) change in species' abundance distributions as captured by change in species rank, richness, and evenness. We found that community stability increased with species replacement and with contribution of species replacement to overall dissimilarity for all taxonomic groups, but declined with increasing change in species richness and evenness. This is consistent with the notion that temporal fluctuations in species abundance can help stabilize community properties. We also found that community stability was highest when change in community functional composition was either lower or higher than expected given reshuffling of each community's taxonomic composition. This suggests that long‐term community stability can result from fluctuations of functionally similar species in assemblages with high taxonomic reshuffling. On the contrary, the functional uniqueness of fluctuating species compensates for lower taxonomic reshuffling to drive stabilization of community properties. Our study provides an initial assessment of the relationship between community stability and biodiversity change and illustrates the utility of fine temporal resolution data collected across ecosystems and biomes to understand the general mechanisms underlying biodiversity–stability relationships.

Land use intensification has led to conspicuous changes in plant and animal communities across the world. Shifts in trait-based functional composition have recently been hypothesized to manifest at lower levels of environmental change when compared to species-based taxonomic composition; however, little is known about commonality in these responses across taxonomic groups and geographic regions. We investigated this hypothesis by testing for taxonomic and geographic similarities in the composition of riverine fish and insect communities across gradients of land use in major hydrologic regions of the conterminous United States. We analyzed an extensive dataset representing 556 species and 33 functional trait modalities from 8,023 fish communities, and 1,434 taxa and 50 trait modalities from 5,197 aquatic insect communities. Our results demonstrate abrupt threshold changes in both taxonomic and functional community composition due to land use conversion. Functional composition consistently demonstrated lower threshold responses compared to taxonomic composition for both fish (urban p = 0.069; agriculture p = 0.029) and insects (urban p = 0.095; agriculture p = 0.043) communities according to gradient forest models. We found significantly lower thresholds for urban versus agricultural land use for fish (taxonomic and functional p < 0.001) and insects (taxonomic p = 0.001; functional p = 0.033). We further revealed that threshold responses of functional composition were more geographically consistent than those of taxonomic composition to both urban and agricultural land use change. Traits contributing the most to overall functional composition change differed along urban and agricultural land gradients, and conformed to predicted ecological mechanisms underpinning community change. This study points to reliable early-warning thresholds that accurately forecast compositional shifts in riverine communities to land use conversion, and highlight the importance of considering trait-based indicators of community change to inform large scale land use management strategies and policies. This article is protected by copyright. All rights reserved.

Responses in taxonomic and functional composition of communities were analysed in small Amazonian streams at the small and large scale (habitat patches, river segment scale, and catchment scale). We hypothesised that similar responses in community structure to local environmental factors were a correlation between taxonomic and functional composition. To evaluate the response of taxonomic composition to environmental variables, redundancy analysis (RDA) and RLQ analysis were performed to investigate the response of community abundance (L) as a function of the environment (R) and traits (Q). The fourth-corner analysis was applied to summarize specific interactions between environmental variables and traits. Then, community taxonomic composition was associated with models at multiple scales of habitat (i.e. riparian/channel, substrates, and water variables). Likewise, the fourth-corner tests and RLQ axes showed associations between trait composition and environmental variables related to variables, such as riparian cover and channel morphology followed by variation in substrate size and composition. Unexpectedly, these results did not show specific associations between unique environmental variables and traits. At last, results showed that local conditions of stream habitat regulated community structure and functional composition of aquatic insects. Thus, these findings indicate that the local environmental filtering appears to be strongly associated with selected species traits adapted to occur in a range of habitat conditions. Despite the low number of analysed streams, these results provide important information for understanding the simultaneous variation in functional trait composition and community composition of aquatic insect assemblages.

Microbial mechanisms of the contrast residue decomposition and priming effect in soils with different organic and chemical fertilization histories