Browsing by Author "Talat Afreen"

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Assessment of diversity, distribution and antibacterial activity of endophytic fungi isolated from a medicinal plant Adenocalymma alliaceum Miers
(2011) Ravindra N. Kharwar; Satish K. Verma; Ashish Mishra; Surendra K. Gond; Vijay K. Sharma; Talat Afreen; Anuj Kumar
A study was conducted for isolation, identification and antibacterial potential of fungal endophytes of Adenocalymma alliaceum Miers., (Bignoniaceae), a medicinal shrub vine plant which has long history for its usages in curing various disorders. A total of 149 isolates of endophytic fungi representing 17 fungal taxa were obtained from 270 segments (90 from each stem, leaf and petiole) of this plant. Hyphomycetes (77.85%) were the most prevalent, followed by Ascomycetes (8.05%) and Coelomycetes (4.03%) respectively. A considerable amount of fungal isolates was kept under (10.07%) Mycelia-Sterilia (MS). Leaf harboured maximum colonization of endophytic fungi (72.22%) which was greater than stem (67.78%) and petiole (25.54%). The Jc similarity index was maximum (0.619) between stem vs leaf followed by leaf vs petiole (0.571) and stem vs petiole (0.428). The dominant endophytic fungi were Alternaria alternata, Aspergillus niger, Stenella agalis, Fusarium oxysporum, Curvularia lunata and Fusarium roseum. Among twelve endophytic fungi tested for antibacterial activity, crude extracts of nine endophytic fungi (75%), showed antibacterial potential against one or more clinical human pathogens. Alternaria alternata, Curvularia lunata, Penicillium sp. and Chaetomium globosum exhibited significant antibacterial activity against 4 of 5 tested pathogens, showing broad spectrum activity. This investigation explains the value of sampling from different tissues of a host plant for the greater species diversity, and additionally, the antibacterial screening of some endophytic fungi from this specific medicinal plant may represent a unique source for many of the useful antibacterial compounds. © 2011 Springer Science+Business Media B.V.
Conservation of tropical agriculture in the era of changing climate
(Springer Singapore, 2020) Talat Afreen; Amit K. Singh
Warmer climate or tropical agriculture is already at its ecological maxima and is more vulnerable to climate change. Increase in temperature and intermittent drought in growing season, which is of due to weaken monsoonal circulation, will have devastating effect on agriculture productivity. The study reported that the productivity of tropical agriculture will be reduced due to climate change by 2100. Research related to climate change in tropics showed an increase in temperature and decrease in rainfall. Thus, the conservation of tropical agriculture is becoming imperative to have a continuous supply of food for the evergrowing population. In this chapter, we are discussing the conservation practices such as the use of improved variety of crops and livestock; change in cropping system (agroforestry), water conservation practices (drip irrigation, ground and surface water recharge), etc., to achieve the goal of sustainable agriculture. Further, we have also suggested climate-smart agriculture practices as they help in the mitigation of greenhouse gasses (GHGs) emission and other pollutants which deteriorate the environment vigorously. © Springer Nature Singapore Pte Ltd. 2020. All rights reserved.
Differential response of graminoid and forb species to precipitation variability in a constructed dry tropical grassland
(Springer, 2024) Talat Afreen; Hema Singh
Precipitation and temperature are the two major drivers of species distribution on the earth. Change in precipitation has severe effects on the species composition of all ecosystems including grassland. In the present study, we have tried to assess the effect of precipitation on two major functional groups of tropical grassland i.e. graminoid (grasses and sedges) and forbs (herbaceous flowering plants). The study was performed in three rainout shelters with three different rain doses (16T, 11T, and 8T) and one unsheltered plot (open C) with ambient rain. Each sheltered and unsheltered plot has three 1 × 1 m randomly assigned subplots of uninvaded indigenous grassland plots (NIG). The study revealed that the aboveground net primary production (ANPP) of graminoids + forbs of the tropical grassland increase with the increase in precipitation. A significant positive correlation of ANPP was found with total inorganic – N (TIN) and soil moisture (SM) and a significant negative with microbial biomass nitrogen (MBN). Regression analysis reveals that after soil moisture, total inorganic – N and N – mineralization are the major determinants for the ANPP. However, when graminoid and forb species are studied separately, graminoids showed a positive response to increased precipitation while forbs did not show such a response. Indicating that the major contributor to the ANPP response toward precipitation increase is graminoid species in a dry tropical grassland. The study indicates the sensitivity of Indian grassland to the change in rainfall quantity, as studied forbs species decrease in both low and high precipitation. Showing that in tropics, forbs species may extinct as of their narrow range of tolerance due to precipiation change, in turn affecting the biodiversity of the area. This is the new possibility of research for researchers around the world. Moreover, to draw any conclusion a detailed study considering the nature of resource acquisition, root length, root architect, and competitive behavior among graminoids and forbs must be done separately, in relation to the precipitation. © International Society for Tropical Ecology 2023.
Does change in precipitation magnitude affect the soil respiration response? A study on constructed invaded and uninvaded tropical grassland ecosystem
(Elsevier B.V., 2019) Talat Afreen; Hema Singh
Change in precipitation in tropics would have a severe consequence on soil CO 2 flux and on its major determinants like soil temperature and soil moisture. Variation in climatic condition also supports the establishment of invasive species in the area. In this communication an attempt is made to assess the impact of change in precipitation regime on soil CO 2 flux in a constructed tropical grassland with and without an invasive plant, Hyptis suaveolens. Three rainout shelters with manipulated precipitation doses (i) of 800 mm (20% the below average), (ii) 1100 mm (average) and (iii) 1600 mm (60% above the average) were established, along with one unsheltered plot (open C) receiving ambient precipitation. Each rain-out shelter containing three sub-treatments viz. (i) bare plots with no vegetation, (ii) uninvaded indigenous grassland plots (NIG), and (iii) grassland plots invaded with H. suaveolens (IG). Significant high soil CO 2 flux was found in plots receiving maximum precipitation (1600 mm) and low in plots receiving minimum precipitation (800 mm). Furthermore, vegetated plots (NIG and IG) exhibited higher soil CO 2 flux than the non-vegetated plots. Among the vegetated plots, IG plots receiving maximum precipitation (1600 mm) had highest soil CO 2 flux, followed by IG plots receiving 1100 mm, and 800 mm precipitation. Seasonal and monthly observations showed that maximum soil CO 2 flux occurred in rainy season, (in July), and minimum in winter season (in January). The important controlling factors for soil CO 2 flux were soil moisture, root biomass and soil temperature. In this study soil moisture explained 61% variability in the soil CO 2 flux. A linear combination of moisture and root biomass explained 74% variability in soil CO 2 flux, and when temperature was added in the multiple regression a total of 79% variability in soil CO 2 flux was accounted for. These findings would help us to understand the biological thresholds of tropical ecosystem related to precipitation regime. It will encourage researchers around the globe to develop ecosystem models, which would enable to forecast the impact of climate change on nutrient cycling. © 2019 Elsevier Ltd
Impact of rainfall variability on the ecophysiology of Hyptis suaveolens: a study in the constructed tropical grassland
(Springer, 2020) Talat Afreen; Vartika Singh; Vinod Kumar Yadav; Rahul Prasad Singh; Hema Singh
Hyptis suaveolens is considered one of the most potent invaders in the eastern part of Uttar Pradesh, India. Climate change especially precipitation variability along with invasion has enormous consequences. To understand how an invasive plant (H. suaveolens) performs and interacts with precipitation variability, particularly in tropical monsoon climate, is vital. To assess the above, three rainout shelters with simulated rainfall of 1600 mm (60% more rainfall than ambient), 1100 mm (average rainfall) and 800 mm (20% less rainfall than ambient) along with one unsheltered plot (open C) were established. Three invaded grassland (IG) and three uninvaded grasslands (NIG) patches of 1 × 1 m2 size were established randomly in each sheltered and unsheltered plot. Among the studied physiological properties and growth measurements, photosynthetic rate, height, diameter and biomass varied significantly with precipitation, in general, the maximum value of these in plots receiving maximum precipitation. Also, the aboveground biomass of H. suaveolens was found to be more sensitive towards precipitation treatment than belowground biomass. H. suaveolens biomass was linearly related to soil moisture (R2 = 0.73), and a linear combination of SM and soil pH increased the R2 value by 19%. The results indicate that H. suaveolens mediates certain soil properties especially related to N-mineralisation, to maintain a constant supply of nutrient, for faster growth under the favourable condition of enhanced precipitation. These findings suggest that the population of H. suaveolens has not evolved drought tolerance, so it is likely that H. suaveolens will not spread in the part of the world which is drier either naturally or due to climate change. © 2020, Springer Nature Switzerland AG.
Influence of changing patterns of precipitation and temperature on tropical soil ecosystem
(Springer Singapore, 2019) Talat Afreen; Hema Singh; J.S. Singh
Tropical soils are nutrient limited and are markedly influenced by seasonality. The seasonal precipitation affects soil wet-dry cycle and has significant consequences for ecosystem functioning and processes. It has been predicted that in tropical countries, a substantial change will occur in the annual mean temperature and precipitation regimes in the future. However, we have little knowledge as to how the soil properties and processes will change with the change in the climatic conditions in tropics. In this chapter, we have tried to collate studies related to the effect of changing climatic condition (temperature and precipitation) on the soil in the tropics. The change in precipitation, than temperature, has more impact on the ecosystem processes in the tropics. Within the tropics the moist and dry ecosystems respond differently to the change in precipitation. Perhaps experimental studies using rain-out shelters may provide more precise information on the effect of the changing pattern of precipitation and drought on the health and vigour of tropical soils. There is a conspicuous lack of literature on the effect of temperature on tropical soils; for getting a complete picture and more precise information, we need more focused studies related to climate change in the tropical region. © Springer Nature Singapore Pte Ltd. 2019.
Invasion by Hyptis suaveolens modifies the effects of altered rainfall variability on nutrient cycling across seasons in a dry tropical grassland experiment
(Taylor and Francis Ltd., 2023) Talat Afreen; Prakash Rajak; Hema Singh
Ecosystems often recover rapidly when changes in climatic conditions are moderate, but extreme changes may push the ecosystem beyond its biological threshold, resulting in rather profound changes in its functioning and species composition. We experimentally evaluated how the ecosystem functioning of tropical grassland may change under changing precipitation variability by investigating shifts in soil properties and their relation to plant invasions. We found that soil moisture, soil pH, inorganic N content (NO3 - N + NH4 - N), N mineralization rate, and soil CO2 flux increase with a rise in rainfall. Moreover, the grassland plots invaded by Hyptis suaveolens, particularly those with increased precipitation, demonstrated elevated mineralization rates, substantial nutrient accumulation, and a reduced microbial biomass in comparison to the uninvaded plots. Our study highlighted that, following soil moisture (SM) and soil temperature (ST), N mineralization emerged as the third primary driver of soil CO2 flux. Enhanced precipitation led to increased N mineralization and subsequent CO2 emissions. The results indicate that escalated CO2 flux in invaded plots could be linked to invasive H. suaveolens adverse effects on soil processes, potentially leading to short-term inefficient nutrient cycling and elevated CO2 emissions, with potential consequences for the overall stability of the ecosystem. © 2024 Université Laval.
Rainfall fluctuation causes the invasive plant Prosopis juliflora to adapt ecophysiologically and change phenotypically
(Springer Science and Business Media Deutschland GmbH, 2025) Prakash Rajak; Talat Afreen; Akhilesh Singh Raghubanshi; Hema N. Singh
Understanding the impact of rainfall variability on the ecophysiology of invasive plants in tropical grasslands is crucial for sustainable ecosystem management. Climate change alters rainfall patterns, which, in turn, may influence the functional traits and physiological responses of plants. Recent studies have explored how fluctuating precipitation affects plant growth and broader ecological dynamics. In this study, we examined these effects on Prosopis juliflora under three different rainfall treatments using rainout shelters: low rainfall (LR, 500 mm, 50% less than ambient), normal rainfall (NR, 1000 mm, representing average ambient rainfall), and high rainfall (HR, 1400 mm, 40% more than ambient). Each shelter was divided into three replicate plots (2 m x 2 m) in a randomized block design. P. juliflora seedlings (20 seedlings per subplot) were transplanted into each subplot within a 4m2 area, with a 0.5 m distance between each plant, and data were collected one year after plot establishment (2020). The physiological parameters measured included leaf traits, growth metrics such as biomass, height, diameter, photosynthetic rate, leaf area (LA), specific leaf area (SLA), leaf carbon (LC), the leaf carbon-to-nitrogen (C/N) ratio, and the root-to-shoot ratio. These parameters showed significant positive responses to changes in precipitation i.e. increase with the increase in rainfall. However, water use efficiency (WUE), leaf nitrogen (LN), leaf dry matter content (LDMC), and root length (RL) showed negative responses i.e. decrease with the increase in rainfall and were highest in the LR plots. Our findings suggest that the ecophysiology and functional traits of P. juliflora are strongly influenced by rainfall variability. The species exhibits considerable phenotypic plasticity, thriving in both drought and elevated precipitation conditions. This adaptability has important implications for its invasive potential and the overall functioning of ecosystems under shifting climatic conditions. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.
Relative availability of inorganic N-pools shifts under land use change: An unexplored variable in soil carbon dynamics
(Elsevier B.V., 2016) Pratap Srivastava; Praveen Kumar Singh; Rishikesh Singh; Rahul Bhadouria; Dharmendra Kumar Singh; Shivam Singh; Talat Afreen; Sacchidanand Tripathi; Pardeep Singh; Hema Singh; Akhilesh Singh Raghubanshi
Land use change (LUC) may detrimentally affect the soil organic carbon (SOC) within different soil fractions; directly supplemented by significant contribution to soil CO2 efflux (SCE). To understand the governing mechanism, experimental data were collected for SOC and SCE along with soil physico-chemical, microbial and aggregate characteristics across adjacent secondary forest (SF)-grassland (GL)-cropland (CL) sequence in dry tropical ecosystems. A significant change in SOC and SCE was observed from SF to GL and CL systems, respectively; though moderately from GL to CL system. Respective decrease in SOC (31 and 42%); soil ammonium-N to nitrate-N ratio (ANR; 96 and 86%), microbial biomass C (MBC; 30 and 50%), nitrogen (MBN; 6 and 33%) and MBC/MBN ratio (25 and 24%); whereas increase in SCE (43 and 57%) and soil nitrate-N availability (340 and 592%) was observed from SF to GL and CL systems. Moreover, aggregate physical distribution shifted toward smaller size fractions; whereas aggregate-associated total C and KMnO4-labile-C concentration and carbon management index (CMI) across aggregate-size fractions decreased linearly with the land use sequence. SOC was majorly governed by macro-aggregate water stability (WASmacro) and MBC; whereas SCE by CMI of macro-aggregate (CMImacro) fraction. Furthermore, the ANR showed positive correlation with microbial (i.e. MBC and MBC/MBN ratio) and macro-aggregate physical (i.e. WASmacro) and chemical stability (i.e. CMImacro). It indicates that a shift in the microbial community with the land use may affect the relative availability of inorganic N pools and associated aggregate characteristics. Thus, our results indicate that a shift in ANR with LUC may be an unexplored and crucial indicator of soil C dynamics mediating quantitative and qualitative changes in microbial and aggregate characteristics in dry tropical ecosystems. Further, a critical emphasis is needed on the relationship of SOC dynamics with ANR for future studies at various spatiotemporal scales worldwide to recognize its potential role as ecological indicator of SOC dynamics. Also, its inclusion under climatic models may help to better predict the future climate. © 2016 Elsevier Ltd. All rights reserved.
Riparian land uses affect the dry season soil CO2 efflux under dry tropical ecosystems
(Elsevier B.V., 2017) Rishikesh Singh; Hema Singh; Shivam Singh; Talat Afreen; Shweta Upadhyay; Ashutosh Kumar Singh; Pratap Srivastava; Rahul Bhadouria; A.S. Raghubanshi
Riparian ecosystems are amongst the most vulnerable ecosystems of the world. The natural gradients and increasing human perturbations under these ecosystems can be explored for understanding the soil carbon (C) dynamics, especially soil carbon dioxide (CO2) efflux. However, studies on soil CO2 efflux and its governing variables under different land uses of dry tropical riparian ecosystems are limited. Therefore, the present study aimed (1) to assess the impact of riparian land use on soil CO2 efflux, and (2) to identify the key drivers of soil CO2 efflux along the river Ganga, Varanasi, India. The riparian land uses taken in this study were moist sandy flat (MSF), uncultivated sandy land (USL) and cultivated sandy land (CSL) depending upon their slope and distance from river body to upland, respectively. Soil CO2 efflux and other soil biophysical properties were measured at 54 locations distributed in six sites having these land uses, in dry season of 2014–15. Soil biophysical properties considered in this study were soil organic C, soil moisture, bulk density, porosity, fine particles, microbial biomass C and soil pH. Riparian land uses were found to have significant impact over soil CO2 efflux with a respective increase of 222, 424 and 63%, for MSF to USL, MSF to CSL, and USL to CSL land use transitions (P < 0.01), respectively. Similarly, the regulators of soil CO2 efflux varied with the land uses. It showed strong positive correlation with soil organic C (r = 0.81), fine particles (r = 0.64) and porosity (r = 0.61), whereas negative correlation with soil moisture (r = 0.61) and bulk density (r = 0.62) for overall dataset. However, soil organic C, fine particles, microbial biomass C and soil pH at MSF; soil organic C and microbial biomass C at USL; and soil moisture, porosity and microbial biomass C at CSL land uses were observed to regulate soil CO2 efflux. The findings revealed that riparian land uses have significant control over soil CO2 efflux and its biophysical regulators which have relative control over it. Soil organic C, soil moisture, fine particles, porosity and microbial biomass C were identified as prevalent regulators of soil CO2 efflux under dry seasons. Overall, the results indicate that the biophysical variables in addition to human interferences (CSL land use) have pronounced regulation over soil CO2 efflux in dry tropical riparian ecosystems. © 2017 Elsevier B.V.
The impact of rainfall variability on selected soil properties and ecophysiological traits in Prosopis juliflora invaded plots
(Nature Research, 2025) Prakash Rajak; Talat Afreen; Akhilesh Singh Raghubanshi; Hema N. Singh
Prosopis juliflora is a major invasive species in tropical and subtropical regions. This study explores the link between precipitation, soil moisture, and plant growth, focusing on the invasive P. juliflora in a simulated altered rainfall regime. The study was conducted simultaneously by using three rainout shelters, Normal Rainfall (NR, 1000 mm) (ii) High Rainfall (HR, 1400 mm) (iii) Low Rainfall (LR, 500 mm). Each rainout shelter was divided into three subplots measuring 2 × 2 m to establish P. juliflora by transplanting 20 seedlings per 4 m2. After 1 years of establishments, plant growth, ecophysiological attributes and soil properties were recorded as per standard protocols. Increased rainfall led to higher soil moisture and promoted P. juliflora growth, biomass, and photosynthetic activity. Conversely, decreased rainfall triggered drought stress, impacting gas exchange and reducing growth. Statistical analysis showed significant (p < 0.05), SM, soil inorganic-N, N-mineralization, growth measurements, photosynthesis rate (Aarea), transpiration rate (E), height (H), diameter (D), root: shoot ratio, and biomass (AGB + BGB) exhibited the highest values in the HR plots during the rainy season and the lowest values in the LR plots during the summer season, following the trend HR > NR > LR. When different rainfall conditions were regressed against P. juliflora biomass, significantly positive linear relationships were observed. The findings suggest that P. juliflora adapts to changing rainfall regimes by allocating resources strategically. While it thrives under high precipitation, it exhibits surprising drought tolerance, potentially colonizing drier regions. Declining monsoon rainfall and increased precipitation intensity may boost P. juliflora’s invasiveness. © The Author(s) 2025.