Soil pH enhancement and alterations in nutrient and Bacterial Community profiles following Pleioblastus amarus expansion in tea plantations.

BACKGROUND: The expansion of bamboo forests increases environmental heterogeneity in tea plantation ecosystems, affecting soil properties and microbial communities. Understanding these impacts is essential for developing sustainable bamboo management and maintaining ecological balance in tea plantations. METHODS: We studied the effect of the continuous expansion of Pleioblastus amarus into tea plantations, by establishing five plot types: pure P. amarus forest area (BF), P. amarus forest interface area (BA), mixed forest interface area (MA), mixed forest center area (TB), and pure tea plantation area (TF). We conducted a comprehensive analysis of soil chemical properties and utilized Illumina sequencing to profile microbial community composition and diversity, emphasizing their responses to bamboo expansion. RESULTS: (1) Bamboo expansion significantly raised soil pH and enhanced levels of organic matter, nitrogen, and phosphorus, particularly noticeable in BA and MA sites. In the TB sites, improvements in soil nutrients were statistically indistinguishable from those in pure tea plantation areas. (2) Continuous bamboo expansion led to significant changes in soil bacterial diversity, especially noticeable between BA and TF sites, while fungal diversity was unaffected. (3) Bamboo expansion substantially altered the composition of less abundant bacterial and fungal communities, which proved more sensitive to changes in soil chemical properties. CONCLUSION: The expansion of bamboo forests causes significant alterations in soil pH and nutrient characteristics, impacting the diversity and composition of soil bacteria in tea plantations. However, as expansion progresses, its long-term beneficial impact on soil quality in tea plantations appears limited.

Assessing tea plantations biophysical and biochemical characteristics in Northeast India using satellite data.

Despite advancements in using multi-temporal satellite data to assess long-term changes in Northeast India's tea plantations, a research gap exists in understanding the intricate interplay between biophysical and biochemical characteristics. Further exploration is crucial for precise, sustainable monitoring and management. In this study, satellite-derived vegetation indices and near-proximal sensor data were deployed to deduce various physico-chemical characteristics and to evaluate the health conditions of tea plantations in northeast India. The districts, such as Sonitpur, Jorhat, Sibsagar, Dibrugarh, and Tinsukia in Assam were selected, which are the major contributors to the tea industry in India. The Sentinel-2A (2022) data was processed in the Google Earth Engine (GEE) cloud platform and utilized for analyzing tea plantations biochemical and biophysical properties. Leaf chlorophyll (Cab) and nitrogen contents are determined using the Normalized Area Over Reflectance Curve (NAOC) index and flavanol contents, respectively. Biophysical and biochemical parameters of the tea assessed during the spring season (March-April) 2022 revealed that tea plantations located in Tinsukia and Dibrugarh were much healthier than the other districts in Assam which are evident from satellite-derived Enhanced Vegetation Index (EVI), Modified Soil Adjusted Vegetation Index (MSAVI), Leaf Area Index (LAI), and Fraction of Absorbed Photosynthetically Active Radiation (fPAR), including the Cab and nitrogen contents. The Cab of healthy tea plants varied from 25 to 35 µg/cm2. Pearson correlation among satellite-derived Cab and nitrogen with field measurements showed R2 of 0.61-0.62 (p-value < 0.001). This study offered vital information about land alternations and tea health conditions, which can be crucial for conservation, monitoring, and management practices.

Distribution of trace metals in a soil-tea leaves-tea infusion system: characteristics, translocation and health risk assessment.

The effects of metal pollution on tea are of great concern to consumers. We apply Geographic information systems technology to study the distribution of heavy metal elements in tea plantation ecosystems in Jiangsu Province, explore the relationships among metals in the soil, tea leaves and tea infusions, and assess the human safety risks of metals. The concentrations of nine metals in a soil-tea leaves-tea infusion system were studied at 100 randomly selected tea plantations in Jiangsu Province, China. Concentrations of selected metals, zinc (Zn), nickel (Ni), manganese (Mn), chromium (Cr) and copper (Cu), were quantified using an inductively coupled plasma-optical emission spectrometer (ICP-OES), and cadmium (Cd), arsenic (As), plumbum (Pb) and mercury (Hg) were quantified using inductively coupled plasma-mass spectrometry (ICP-MS). Arc-Map 10.3 was used for the spatial analysis of metals in soil, tea leaves and tea infusions. We found that the contents of Mn, Ni and Zn are high level in soil, tea leaves and tea infusions. The Mn level showed a spatial distribution pattern with greater concentrations at the junction of Nanjing and Yangzhou, southwest of Changzhou and west of Suzhou. The hazard index (HI) values in north-central Nanjing, southern Suzhou, southwestern Changzhou and northern Lianyungang were relatively greater. The Zn, Ni, Mn, Cr and Cu levels in the soil-tea infusion system were 17.3, 45.5, 54.5, 1.5 and 14.3%, respectively. The order of the leaching rates of the elements was Ni > Cr > Zn > Mn > Cu. The relative contribution ratios of HI were in the order of Mn > Ni > Cu > Zn > Cr > Pb > Cd > As > Hg. In tea infusions, the Mn level has the greatest potential health risks to consumers. Moreover, using Csoil it was inferred that the safety thresholds of Zn, Ni, Mn, Cr and Cu in soil were 27,700, 50, 1230, 493,000 and 16,800 mg L-1, respectively. The content of heavy metals in soil and tea varies greatly in different regions of Jiangsu Province, 92% of the soil has heavy metal content that meets the requirements of pollution-free tea gardens, 91% of tea samples met the requirements of green food tea. The thresholds for Ni (50 mg L-1) and Mn (1230 mg L-1) can be used as maximum limits in tea plantation soils. The consumption of tea infusions did not pose metal-related risks to human health.

"Who will stand up for us?" the social determinants of health of women tea plantation workers in India.

INTRODUCTION: The tea estate sector of India is one of the oldest and largest formal private employers. Workers are dependent on plantation estates for a range of basic services under the 1951 Plantation Labour Act and have been subject to human rights violations. Ad hoc reports related to poor health outcomes exist, yet their determinants have not been systematically studied. This study in Assam, situated in Northeast India, sought to understand the Social Determinants of Health (SDH) of women plantation workers with an aim to offer directions for policy action. METHODS: As part of a larger qualitative study, 16 FGDs were carried out with women workers in three plantations of Jorhat district covering permanent and non-permanent workers. Informed consent procedures were carried out with all participants individually. Data were analyzed thematically using Ritchie and Spencer's framework based on an adapted conceptual framework drawing from existing global conceptual models and frameworks related to the SDH. RESULTS: Determinants at structural, intermediary and individual levels were associated with health. Poverty and poor labour conditions, compounded by the low social position of women in their communities, precluded their ability to improve their economic situation. The poor quality of housing and sanitation, inadequate food and rations, all hampered daily living. Health services were found wanting and social networks were strained even as women were a critical support to each other. These factors impinged on use of health services, diet and nutrition as well as psychosocial stress at the individual level. CONCLUSION: Years of subjugation of workers have led to their deep distrust in the system of which they are part. Acting on SDH will take time, deeper understanding of their relative and/or synergistic contribution, and require the building of stakeholdership. Notwithstanding this, to have heard from women workers themselves has been an important step in visibilizing and building accountability for action on the health and SDH of women in plantation estates.

Glyphosate resistance in Eleusine indica: EPSPS overexpression and P106A mutation evolved in the same individuals.

Goosegrass is one of the most widespread weeds in orchards and tea plantations in China, and glyphosate is a popular herbicide used to control it. However, high glyphosate selection pressure has led to some populations becoming resistant. The objectives of this research were to determine resistance levels and possible resistance mechanisms of goosegrass populations from several tea plantations in Zhejiang Province in China. The resistance indexes in four goosegrass populations (SH, SY, CA and CX) ranged from 4.9 to 13.4, and lower shikimate accumulation in these populations compared with a glyphosate-susceptible (GS) population confirmed their resistance to glyphosate. No mutations in the target gene EPSPS were found in populations SH and SY, however, the expression of EPSPS in these two populations was 9.3 and 29.7 times higher than that in the GS population, respectively. In the CX population, a P106S mutation in EPSPS was found in 6.7% of the individuals and another 80.0% of individuals had EPSPS amplification. In population CA, all the individuals had a P106A mutation and 86.7% of them had amplification in EPSPS. The EPSPS copy numbers ranged from 5.2 to 62.3 in these four resistant populations. There was a positive correlation between signal intensities of primary anti-EPSPS antibody and the copy number of the EPSPS protein, as indicated by immunoblot analysis. In population CA, with high-level resistance to glyphosate, both P106A mutation and amplification in EPSPS evolved in the same individuals in this population.

Pest management through Bacillus thuringiensis (Bt) in a tea-silkworm ecosystem: status and potential prospects.

Bacillus thuringiensis (Bt) is a soil bacterium that forms spores containing crystals comprising one or more Cry or Cyt proteins having potential and specific insecticidal activity. Different strains of Bt produce different types of toxins, affecting a narrow taxonomic group of insects. Therefore, it is used in non-chemical pest management, including inherent pest resistance through GM crops. The specificity of action of Bt toxins reduces the concern of adverse effects on non-target species, a concern which remains with chemical insecticides as well. To make use of Bt more sustainable, new strains expressing novel toxins are actively being sought globally. Since Bt is successfully used against many pests including the lepidopteran pests in different crop groups, the insecticidal activity against Samia cynthia (Drury) (Eri silkworm) and Antheraea assamensis Helfer (Muga silkworm) becomes a concern in the state of Assam in India which is a predominantly tea- and silk-producing zone. Though Bt can be used as an effective non-chemical approach for pest management for tea pests in the same geographical region, yet, it may potentially affect the silk industry which depends on silkworm. There is a need to identify the potentially lethal impact (through evaluating their mortality potential) of local Bt strains on key silkworm species in North Eastern India. This will allow the use of existing Bt for which the silkworms have natural resistance. Through this review, the authors aim to highlight recent progress in the use of Bt and its insecticidal toxins in tea pest control and the potential sensitivity for tea- and silk-producing zone of Assam in India.

Systematic review assessing the effects of amendments on acidic soils pH in tea plantations.

Soil acidification has emerged as a critical limiting factor for the sustainable development of the tea industry. In this article, a comprehensive review of 63 original research articles focusing on the impact of amendments on the pH in tea plantations soil was conducted. Through meta-analysis, the effect of applying soil amendments to increase the pH of tea plantation soil and its influencing factors were investigated. The results revealed that lime had a significant impact, increasing the pH by 18% in tea plantation soil, while rapeseed cake had a minimal (2%) effect. It was observed that as the quantity of amendments and pH levels increased, so did their impact on the pH of tea plantation soil. Subgroup analysis within biochar showed varying effects, depending on soil pH, with an 11% increase in acidic soil. Among these amendments, biochar produced at pyrolysis temperature ranging from 501-600 °C and derived from animal waste demonstrated significant effect on increasing soil pH in tea plantations by 9% and 12%, respectively. This study offers valuable insights into improving and ensuring the health and sustainability of tea plantations.

Ecological risk assessment of heavy metals in tea plantation soil around Tai Lake region in Suzhou, China.

Tea plant [Camellia sinensis (L.) O. Kuntze] is one of the important foliar cash crops in China, and its root system absorbs heavy metal (HM) elements enriched in the soil and transports them to the over ground part. In order to ensure the safety of the soil ecological environment and tea raw materials in the tea production area, the HM contents of soil and tea plant leaves in Suzhou tea plantations were detected, the relationship between HMs and soil physicochemical properties was analyzed, and the ecological risk of HMs in tea plantation soils was evaluated by using relevant detection techniques and evaluation models. The results showed that the average pH of tea plantation soils around Tai Lake in Suzhou was within the range suitable for the growth of tea plants. The pH, soil organic matter, total nitrogen, available phosphorus and available potassium of tea plantation soil satisfying the requirements of high quality, high efficiency and high yield ('3H') tea plantation accounted for 47.06%, 26.47%, 8.82%, 79.41% and 67.65%, respectively. Site 2 fully met the requirements of '3H' tea plantation. In addition, the contents of cadmium (Cd) and mercury (Hg) were extremely variable, and the average contents exceeded the background value of soil in Jiangsu Province, but the HM contents of tea leaves all met the pollution-free standard, and the HM contents of tea leaves around Tai Lake in Suzhou were generally at a safe level. The composite ecological risk index ranged from 0.05 to 0.60, and 32 of the 34 sample sites (except site 21 and site 23) are the most suitable agricultural land for tea plantations.

Potential to Reduce Chemical Fertilizer Application in Tea Plantations at Various Spatial Scales.

Tea is the main commercial crop grown in China, and excessive application of chemical fertilizers in tea plantations is common. However, the potential to reduce chemical fertilizer use in tea plantations is unclear. In this study, Zhejiang Province was selected as the research object to systematically analyze the potential for tea plantation chemical-fertilizer reduction at different spatial scales. The geographic information system-based analytic hierarchy process method and Soil and Water Assessment Tool model were used to determine the chemical fertilizer reduction potential at the province scale and watershed scale, respectively. At the field scale, two consecutive years of field experiments were conducted on a tea plantation. Province-level analysis showed that 51.7% of the area had an average total fertilization intensity greater than 350 kg/hm2 and a high reduction potential. Watershed analysis revealed that chemical fertilizer reduction had better potential in reducing total nitrogen and total phosphorus inputs to runoff in the short term, whereas 50% organic fertilizer substitution was the best strategy to achieve long-term effects. The field experiments further proved that organic fertilizer substitution balanced tea growth and environmental protection. This study provides a useful method to investigate strategies to reduce chemical fertilizer use in tea-growing areas.

Organic amendments improved soil quality and reduced ecological risks of heavy metals in a long-term tea plantation field trial on an Alfisol.

Tea plantation can cause strong soil degradation, e.g. acidification, basic nutrient decrease and microbial diversity loss, naturally by its root activity and secondary by practically tremendous synthetic N input. Organic amendments application is considered a practical way to mitigate the above adverse consequence. However, the trade-off between agronomic and environmental effects on the application of the organic amendments is still under debate. Herein, we conducted a long-term field experiment with four treatments, including control (without and fertiliser) (CK), chemical fertiliser treatment (CF), chicken manure treatment (CM) and chicken manure combined with biochar treatment (CMB) to investigate the effects of organic amendments application on soil quality, heavy metal contamination and tea production in a tea plantation. Totally 16 plots were arranged randomly with a completely randomised design. The results showed that CM and CMB treatments improved soil nutrient, mitigated soil acidification and ameliorated soil porosity compared to CF treatment. CMB treatment displayed a relatively high tea yield and quality in three consecutive years of monitoring. However, CM and CMB treatments elevated the heavy metal (HM) potential ecological risk (RI) and Nemerow's composite index (Ps). CM treatment significantly increased available As, Pb, Cu and Zn concentrations compared to CF treatment, while CMB treatment significantly decreased available Cr and Cu concentrations and slightly decreased available Cd, Pb and Ni concentrations compared to CM treatment. But the increase of available As and Zn in CMB treatment compared to CM treatment also indicated adverse effects of biochar addition. The PLS-PM model showed HM risk had direct negative effects on tea quality. Moreover, soil fungal community revealed positive effects on tea yield and negative effects on tea quality. Overall, our study proved that CMB treatment could improve soil quality, reduce available Cr and Ni concentrations, maintain tea yield and increase tea quality.

Enhanced soil potential N2O emissions by land-use change are linked to AOB-amoA and nirK gene abundances and denitrifying enzyme activity in subtropics.

Conversion of forestland to intensively managed agricultural land occurs worldwide and can increase soil nitrous oxide (N2O) emissions by altering the transformation processes of nitrogen (N) cycling related microbes and environmental conditions. However, little research has been conducted to assess the relationships between nitrifying and denitrifying functional genes and enzyme activities, the altered soil environment and N2O emissions under forest conversion in subtropical China. Here, we investigated the long-term (two decades) effect of converting natural forests to intensively managed tea (Camellia sinensis L.) plantations on soil potential N2O emissions, inorganic N concentrations, functional gene abundances of nitrifying and denitrifying bacteria, as well as nitrifying and denitrifying enzyme activities in subtropical China. The conversion significantly increased soil potential N2O emissions, which were regulated directly by increased denitrifying enzyme activity (52 %) and nirS + nirK gene abundance (38 %) as shown by structural equation modeling, and indirectly by AOB-amoA gene abundance and inorganic N concentration. Our results indicate that converting natural forests to tea plantations directly increases soil inorganic N concentration, resulting in increases in the abundance of soil nitrifying and denitrifying microorganisms and the associated N2O emissions. These findings are crucial for disentangling the factors that directly and indirectly affect soil potential N2O emissions respond to the conversion of forest to tea plantation.

Large-Scale Characterization of the Soil Microbiome in Ancient Tea Plantations Using High-Throughput 16S rRNA and Internal Transcribed Spacer Amplicon Sequencing.

There is a special interaction between the environment, soil microorganisms, and tea plants, which constitute the ecosystem of tea plantations. Influenced by environmental factors and human management, the changes in soil microbial community affected the growth, quality, and yield of tea plants. However, little is known about the composition and structure of soil bacterial and fungal communities in 100-year-old tea plantations and the mechanisms by which they are affected. In this regard, we characterized the microbiome of tea plantation soils by considering the bacterial and fungal communities in 448 soil samples from 101 ancient tea plantations in eight counties of Lincang city, which is one of the tea domestication centers in the world. 16S and Internal Transcribed Spacer (ITS) rRNA high-throughput amplicon sequencing techniques were applied in this study. The results showed that the abundance, diversity, and composition of the bacterial and fungal communities have different sensitivity with varying pH, altitude, and latitude. pH and altitude affect soil microbial communities, and bacterial communities are more sensitive than fungi in terms of abundance and diversity to pH. The highest α-diversity of bacterial communities is shown in the pH 4.50-5.00 and 2,200-m group, and fungi peaked in the pH 5.00-5.50 and 900-m group. Because of environmental and geographical factors, all microbes are similarly changing, and further correlations showed that the composition and structure of bacterial communities are more sensitive than fungal communities, which were affected by latitude and altitude. In conclusion, the interference of anthropogenic activities plays a more important role in governing fungal community selection than environmental or geographical factors, whereas for the bacterial community, it is more selective to environment adaptation than to adaptation to human activities.

A checklist of spiders in tea plantations of China.

BACKGROUND: Spiders are the most dominant predatory natural enemies of insect pests in the tea plantation ecosystem. There has been a large amount of literature published about the investigation of spider species in Chinese tea plantations from 1982 to 2020. Here, the spider species in Chinese tea plantations has been summarised and the dominant spider species in each regional tea plantation recorded. To date, there were 535 spider species from 40 families reported in Chinese tea plantations. NEW INFORMATION: There are 245 spider species from 13 families now being added to the checklist. A total of 89 spider species from 19 families were the dominant species, amongst them, Agelena labyrinthica, Allagelena difficilis, Neoscona theisi, Clubiona deletrix, Clubiona japonicola, Hylyphantes graminicola, Pardosa laura, Oxyopes sertatus, Evarcha albaria, Plexippus paykulli, Coleosoma octomaculatum, Ebrechtella tricuspidata and Xysticus ephippiatus were recorded in many tea plantations. The checklist will provide important data for the biodiversity and distribution of spiders in tea plantations of China.

Are Yellow Sticky Cards and Light Traps Effective on Tea Green Leafhoppers and Their Predators in Chinese Tea Plantations?

In Chinese tea plantations, yellow sticky cards and light traps are increasingly used to control insect pests, especially the tea green leafhopper Empoasca onukii. In this study, a 16-week open-field experiment with daily weather monitoring was designed to test the responses of tea green leafhopper, parasitoids and spiders to yellow sticky cards and three light traps with different wavelengths (covered with sticky cards). An exclosure experiment was also designed to further test the influence of the three light systems (without sticky card) on the same species. The results showed that all three light emitting diode (LED) light traps (white, green and yellow) and yellow sticky cards attracted many more E. onukii male adults than females during the course of the open field experiment, with less than 25% of trapped adults being females. Parasitoids and spiders were also attracted by these systems. Weather variables, especially rainfall, influenced the trapping efficiency. In the exclosure experiment, the population of leafhoppers in the yellow sticky card treatment did not decline significantly, but the number of spiders significantly decreased. The green and white light treatments without sticky cards showed a significant control of E. onukii and no obvious harm to spiders. These results suggest that yellow sticky cards and light traps have limited capacity to control tea green leafhoppers. However, light, especially green light, may be a promising population control measure for tea green leafhoppers, not as killing agents in the traps, but rather as a behavioral control system.

Converting evergreen broad-leaved forests into tea and Moso bamboo plantations affects labile carbon pools and the chemical composition of soil organic carbon.

This study aimed to explore the effects of conversion from evergreen broad-leaved forests (EBFs) to tea plantations (TPs) and Moso bamboo (Phyllostachys heterocycla var. pubescens) plantations (MBPs) and the subsequent long-term intensive management on the soil carbon pool and the chemical composition of soil organic carbon (SOC). Soil samples from three layers (0-10, 10-30 and 30-60 cm, respectively) were collected from adjacent EBFs, TPs and MBPs in An'ji County, Zhejiang Province, China. The physico-chemical properties of soils, including bulk density, SOC and its different fractions were determined. The chemical composition of SOC was also measured using 13C-nuclear magnetic resonance spectroscopy (NMR). The results showed that conversion from EBFs to TPs and MBPs decreased the concentrations of water soluble organic carbon (WSOC), light and heavy fraction organic carbon (LFOC, HFOC) and humus carbon (HC) (P < 0.05), reduced the O-alkyl C and carbonl C content, but increased the alkyl C, Aromatic C, aromaticity and the ratio of alkyl C/O-alkyl C (A/O-A) (P < 0.05). These results suggested that intensive management markedly altered the chemical structure of SOC and labile carbon pools. Our results demonstrated that converting EBFs to TPs and MBPs had a negative effect on SOC content and a positive effect on SOC stability. Therefore, management practices such as rational fertilization and sod cultivation are recommended after land-use conversion.

Heard but not seen: Comparing bat assemblages and study methods in a mosaic landscape in the Western Ghats of India.

We used capture (mist-netting) and acoustic methods to compare the species richness, abundance, and composition of a bat assemblage in different habitats in the Western Ghats of India. In the tropics, catching bats has been more commonly used as a survey method than acoustic recordings. In our study, acoustic methods based on recording echolocation calls detected greater bat activity and more species than mist-netting. However, some species were detected more frequently or exclusively by capture. Ideally, the two methods should be used together to compensate for the biases in each. Using combined capture and acoustic data, we found that protected forests, forest fragments, and shade coffee plantations hosted similar and diverse species assemblages, although some species were recorded more frequently in protected forests. Tea plantations contained very few species from the overall bat assemblage. In riparian habitats, a strip of forested habitat on the river bank improved the habitat for bats compared to rivers with tea planted up to each bank. Our results show that shade coffee plantations are better bat habitat than tea plantations in biodiversity hotspots. However, if tea is to be the dominant land use, forest fragments and riparian corridors can improve the landscape considerably for bats. We encourage coffee growers to retain traditional plantations with mature native trees, rather than reverting to sun grown coffee or coffee shaded by a few species of timber trees.