Search Results (17)

China has approximately 3.43 million hectares of tea plantations, which offer significant potential for carbon sequestration and the reduction of CO₂ emissions. However, the mechanisms underlying the stability and mineralization of soil organic carbon (SOC) in different tea plantations remain unclear. This study aimed to comprehensively evaluate the effects of chemical, physical, and microbial factors on SOC mineralization in tea plantations with different methods of forest conversion to tea plantations and different ages of tea plants. Our findings indicate that forest conversion to tea plantation methods and tea planting age significantly influence SOC mineralization. Specifically, the SOC mineralization in tea plantations reclaimed by clear-cutting and burning (FMT4) was lower than in those reclaimed by partial cutting (MT3, MT30, and MT150). This variation is attributed to differences in the chemical structure of SOC, which showed higher proportions of aromatic C (33.4%) and carbonyl/carboxyl C (7.8%), alongside lower proportions of O-alkyl C, in the FMT4 tea plantation compared to the others. Additionally, SOC mineralization was significantly higher in the MT150 tea plantation (15.23 g C kg⁻¹ SOC) than in the MT3 (10.11 g C kg⁻¹ SOC), MT30 (10.38 g C kg⁻¹ SOC), and MT200 plantations (9.13 g C kg⁻¹ SOC). Notably, although the MT200 tea plantation had a higher proportion of O-alkyl C (42.4%) than the MT3 and MT30 plantations (36.4%), and was similar to the MT150 plantation (43.1%), its SOC mineralization remained lower due to the higher clay content (278 g kg⁻¹). Correlation analysis and random forest analysis further revealed that physical properties, particularly clay content, are the most significant factors regulating SOC mineralization, followed by the chemical structure, such as O-alkyl C and aromatic C, as well as other physicochemical properties like the carbon-to-nitrogen (C/N) ratio, and microbial properties like Gram-positive bacteria. In conclusion, our study highlights the complex interplay of soil physical properties and SOM chemical structure and microbial properties in regulating SOC mineralization, providing valuable insights for improving carbon management in tea plantations. Full article

Revealing the changes in organic carbon (OC) and labile organic carbon (LOC) fractions in soil aggregates is of great significance for better understanding of soil carbon sources and carbon sink effects in tea plantations. In this study, soil samples were collected at the 0–20 cm depth in tea plantations with different stand ages (including 0 years (nudation), 8 years, 15 years, and 23 years) in Guangxi, China. Then, soil samples were divided into different sized aggregates (including >2 mm, 2–1 mm, 1–0.25 mm, and <0.25 mm) by a suitable moisture classification method for the determination of OC and LOC fractions. In this study, soil aggregate stability (as indicated by the mean weight diameter (MWD) and geometric mean diameter (GMD)) was the highest at 15 years of tea cultivation, indicating that these (15-year-old) tea plantations had stable aggregate structure and provided physical protection for soil carbon storage. At the 0–20 cm depth, the stocks of soil OC and LOC fractions were mainly distributed in >2 mm aggregates, regardless of the stand ages, implying that these aggregates were the main carriers of soil OC and LOC fractions in tea plantations. During tea cultivation, the stocks of soil OC and LOC fractions first increased and then decreased, reaching the highest levels at 15 years, which indicated that the critical point of soil from carbon sink to carbon source was 15 years after tea cultivation. Therefore, attention should be paid to the protection of soil structure in the late (15–23 years) stage of tea cultivation, so as to maintain the carbon sink effect of soil in tea plantations in Guangxi, China. Full article

Tea (Camellia sinensis (L.) Kuntze) plantations have been rapidly expanding in recent years in developing countries, but there is a lack of knowledge about the effects of woodland conversion to tea plantations and tea plantation aging on soil organic carbon (SOC) accumulation in subtropical regions, which may be a critical issue for accurately estimating the regional C balance in tea planting areas. Thus, in this study, we selected four tea plantations with ages ranging from 5 to 23 years, along with an adjacent mature pine forest (PF, more than 60 years of age), to investigate the effects of woodland conversion to tea plantations and stand age on SOC. Lignin phenols and amino sugars were used to distinguish the contributions of plant-derived C and microbial-derived C to SOC. The results showed that when PF is converted to a tea plantation, 54.12% of the SOC content in the topsoil is lost, with reductions of 84.77% in plant-derived C and 10.23% in microbial-derived C; however, there is a slight increase in microbial-derived C in the deep-layer soil. The tea planting age only has a negative effect on microbial-derived C in the topsoil. Additionally, the plant aboveground biomass, ratio of carbon to nitrogen, total nitrogen concentration, and clay–silt content are key environmental variables influencing SOC accrual, explaining 59.8% of the total variance. SOC and plant-derived C are thus implicated in the quick response to decreasing plant inputs with land conversion and do not accumulate with increasing tea plantation age under the current tea plantation management practices. Generally, more attention should be focused on SOC loss with woodland conversion to tea plantations at the regional scale, and more effective practices can be applied to enhance SOC accrual in subtropical tea plantations. Full article

Optimizing soil carbon content is essential for mitigating climate change. Understanding the soil organic carbon (SOC) contents and their relationship with plantation age is important for enhancing SOC in tea plantations. However, there is still a lack of studies in quantifying the SOC–age curve of the whole life cycle in tea plantations. Thus, in this study, we collected 140 soil samples aged 3 to 60 years in the four representative regions (Anxi, Datian, Qingliu, and Fuzhou) in Fujian Province to quantify the SOC contents and their relationship with plantation age. We found that the average SOC was 14.6 ± 6.1 g/kg in the four sampling regions. Nitrogen (N) emerged as having a highly significant positive correlation with SOC (R² = 0.9). We also found a significant negative correlation between SOC and mean annual temperature (MAT) (R² = 0.6), and a significant positive correlation with mean annual precipitation (MAP) (R² = 0.6). The SOC increased with plantation age at 3–20 years old and peaked at 16–20 years old. After 35 years, the SOC decreased gradually with the aging of the plantation. The results indicated that tea plantations could be renewed after the age of 35. These results showed that optimizing age structure is important in enhancing SOC in tea plantations and is meaningful in achieving carbon neutrality. Full article

Nitrogen (N) and phosphorus (P) play crucial roles in tea planting, but information on how the long-term excessive application of chemical N fertilizer affected N and P in subtropical tea plantations remains limited. In this study, soil and leaf samples were collected along a chronosequence of tea plantations (0-, 5-, 10-, 18- and 23-year-old plantations) with excessive N input but no P application to investigate the effects of planting age on N and P availability. Diverse soil N forms and P fractions, and the concentrations of leaf N and P were measured. The results showed that (1) ${\mathrm{N}\mathrm{O}}_3^{-}$-N and dissolved organic nitrogen (DON) concentrations in both topsoil and subsoil, and the N concentration of mature leaf showed significant upward trends with tea plantation age; (2) the concentrations of available phosphorus (AP), NaHCO₃-P_i in labile P pool, NaOH-P_i and D.HCl-P_i in moderately labile P pool in both layers of soil and that the P concentration of mature leaf also increased with age; (3) the N concentration of mature leaves had closely significant logarithmic relations with ${\mathrm{N}\mathrm{O}}_3^{-}$-N concentration, while the TP (total P) concentration of mature leaves had significant positive correlations with AP; and (4) the ratio of N/P in tea leaves indicated a slightly P limitation in tea plantations. We concluded that the ${\mathrm{N}\mathrm{O}}_3^{-}$-N concentration, instead of TN (total N) of ${\mathrm{N}\mathrm{H}}_4^{+}$-N, would be a good indicator to reflect N availability for tea trees, and the increasing of ${\mathrm{N}\mathrm{O}}_3^{-}$-N concentration in soil has a diminishing promoting effect on the TN concentration of mature leaves. The long-term application of chemical N fertilizer had not lead to serious P limitation in subtropical tea plantations. Generally, our study could contribute to improving our understanding of N and P availability and optimizing fertilization management in subtropical tea plantations. Full article

Land use change (LUC) has direct and indirect consequences on soil quality. To gain insight into how LUC influences the physical properties of soil, it can be advantageous to compare undisturbed ecosystems with those that have naturally evolved over time, as well as to use soil quality indices to pinpoint the sensitivity of each ecosystem and land use change (LUC). A soil survey was carried out in the six major ecosystems of the Nilgiri Hill Region: cropland (CL), deciduous forest (DF), evergreen forest (EF), forest plantation (FP), scrubland (SL), and tea plantation (TP), with those having an establishment for over 50 years being selected and analyzed for soil physical parameters. In addition, soil quality indices were also derived to pinpoint the vulnerability of each ecosystem to LUC. The results reveal that the changes in land use significantly altered the soil physical properties. The content of clay was higher in EF and DF and increased with the soil profile’s depth, whereas the sand content was higher in CL and TP and decreased with the depth increment. BD and PD were significantly lower in EF, DF, SL, and FP, whereas they were higher in CL and TP. PS and ASM followed a similar trend to BD and PD. Owing to undisturbed natural settings, an abundance of litter input, and higher carbon concentrations, the HC was higher in EF, DF, SL, and FP, whereas, in the case of anthropogenic-influenced ecosystems such as CL and TP, it was lower. We discovered that LUC has altered Ag S, WSA, and MWD. Due to tillage and other cultural practices, Ag S, WSA, and MWD were significantly lower in CL and TP. However, the results confirm that native ecosystems (EF and DF) with a higher carbon content prevent such degradation, thereby resulting in good Ag S, WSA, and MWD. Full article

Soil microbes are the key to revealing the mechanisms driving variation in soil biogeochemical processes. In recent decades, forests in Southeast China have been widely transformed into tea plantations due to the drivers of economic benefits. However, the changes in the soil microbial community and their potential function during the transition from a typical forest ecosystem to tea plantations remain poorly understood. This study investigated the soil microbial community in tea plantation soils with different planting ages, i.e., 6, 12, 23 and 35 years, and in an adjacent woodland control. We discovered that tea planting significantly increased soil bacterial richness (ACE and Chao1) and decreased fungal richness, the diversity of bacteria (Simpson and Shannon) show a trend of initially decreasing and then increasing while there was no significant effect on fungal diversity. After tea planting, the relative abundances of Actinobacteria and Proteobacteria increased by 180.9%–386.6% and 62.3%–97.5%, respectively; the relative abundances of Acidobacteria decreased by 11.4%–66.8%. However, the fungal phyla were not significantly different among different aged tea plantations and woodlands. FAPROTAX and FUNGuild revealed that the transition of natural woodland to tea plantations significantly increased the relative abundances of aerobic_chemoheterotrophy (14.66%–22.69%), chemoheterotrophy (34.36%–37.04%), ureolysis (0.68%–1.35%) and pathogenic fungi (26.17%–37.02%). db-RDA proved that the bacterial community structure was more strongly related to soil pH and available nitrogen (AN), while the main determinants of the fungal community composition were soil pH and soil organic matter (SOM). These findings indicate that tea planting has a strong effect on the soil microbial community and potential function. The change in soil pH during tea planting was the most important factor affecting the soil microbial community, while soil bacteria were more sensitive to tea planting than fungi. Full article

Scopula subpunctaria (Herrich-Schaeffer) (Lepidoptera: Geometridae) is a leaf-eating pest in tea plantations that often causes serious economic losses. Arma chinensis (Fallou) (Hemiptera: Pentatomidae) as a polyphagous insect has become one of the main biological control agents for tea plantation pests due to its wide feeding habit, predatory ability, and adaptability. However, studies related to the predation using A. chinensis on the third instar S. subpunctaria have not been reported. In this study, we used the age-stage, two-sex life table method to analyze the developmental duration and fecundity of S. subpunctaria fed on tea, and A. chinensis fed on third instar S. subpunctaria larvae, under a 25 °C regime. The growth, development, survival, fecundity, and predation rates of the insect populations were investigated. The results showed that the predator and the prey can complete their respective life histories, but the developmental durations at each stage were different, and the developmental stages overlapped significantly. In addition, we used the computer program TIMING-MSChart to project the stage structure and the total population size of A. chinensis and S. subpunctaria. We also simulated the population changes of S. subpunctaria using an A. chinensis intervention. These results showed that S. subpunctaria can support A. chinensis to finish its life history and A. chinensis has great potential to control S. subpunctaria. This study contributes to the understanding of the biological characteristics of S. subpunctaria and provides a theoretical basis for releasing A. chinensis in the field to suppress S. subpunctaria. Full article

Land-use change is one of the most important driving factors of change in soil microbial diversity. Deforestation for tea plantations has transformed large areas of forestland in hilly areas of Southeast China. However, its impact on the soil fungal community structures and functions is still understudied. We compared the soil fungal communities and their functions in forestland (FD), a 3-year-old tea plantation (ZC3) and a 30-year-old tea plantation (ZC30) at 0–20 cm and 20–40 cm soil depths. The soil fungal community compositions and potential functions were analyzed using high-throughput sequencing techniques coupled with FUNGuild analysis. The results showed that the initial conversion from forestland to tea plantations significantly decreased soil fungal diversity. With an increase in the tea plantation age, the soil fungal diversity rebounded. The dominant phyla included Ascomycota, Basidiomycota, unclassified_k_fungi and Mortierellomycota, which were identified in all soil samples and accounted for 90% of all fungal communities. Non-metric multidimensional scaling analysis (NMDS) indicated that the soil fungal community was more responsive to the duration of tea planting than to the soil depth. FUNGuild analysis showed that the relative abundance of pathogenic and pathotrophic-saprotrophic fungi was higher while saprotrophs were lower in ZC30 compared with FD. Among the analyzed soil properties, soil available nitrogen, available phosphorus, available potassium and bulk density were the prime factors affecting the abundance and diversity of soil fungal community compositions. Network analysis showed that fungal microbial taxa increased positive interactions to enhance the adaptability of fungal microorganisms to long-term tea planting. Collectively, our results provide a clear view on the dynamic yet differential responses of fungal communities to land-use changes, and further emphasizes the need for long-term conventional tea plantations to adopt sustainable agricultural practices to reduce soil pathogenic fungi. Full article

Tea plants prefer NH₄⁺-N to NO₃⁻-N, and thus nitrification would be detrimental to the N uptake of tea. However, the effects of different stand ages on nitrification and nitrogen oxide (NO and N₂O) emissions in tropical and subtropical regions remain unclear. We performed an incubation experiment with tea field soils from different stand ages (5, 15, and 30 years) under different water contents in subtropical (Changsha, Hunan; C5L, C15L, C30L, C5H, C15H, C30H) and tropical regions (Baisha, Hainan; B5L, B15L, B30L, B5H, B15H, B30H). The results showed that the highest net nitrification rate was in C15L and B15. The results indicated that there was more NO₃⁻-N loss in the 15-y tea field soil in both regions. The highest nitrogen oxide emissions from the subtropical and tropical plots were in C15H and B30H. Available K was the key variable for NO and N₂O emissions in Changsha county, whereas SOM, pH, and available P were the key factors affecting NO and N₂O emissions in Baisha county. Our findings suggest that more attention should be paid to NO₃⁻-N loss in middle-aged (10–30 years) tea fields. Similarly, the focus should be given to nitrogen oxide emissions from middle-aged tea plantations in subtropical regions and old tea plantations (≥30 stand years) in tropical regions. Full article

This study aimed to identify the characteristics of Andisols under tea plantations affected by different Oldeman’s agro-climatic zones, of different ages, and containing different types of volcanic ash material. For this study, three tea plantation estates were chosen, the Ciater Site (CTR), Sinumbra Site (SNR), and Sedep Site (SDP), having Oldeman’s agro-climatic zones of A, B1, and B2, respectively. Three profiles (CTR-A, CTR-B, and SNR-A) were created from andesitic volcanic ash, and three profiles (SNR-B, SDP-A, and SDP-B) were created from basaltic volcanic ash materials. The CTR-A, SNR-B, and SDP-B profiles were obtained from Holocene parent materials, while the CTR-B, SNR-A, and SDP-A profiles were derived from Pleistocene parent materials. Soil samples were taken from the soil profiles from depths of 0 to 153 cm incrementally, dependent on each soil horizon thickness. The findings of the study reveal that the age of parent materials and the variance in agro-climatic zones result in considerable differences in soil chemical characteristics, such as pH (H₂O), base saturation (BS), and organic C, while the qualities of the basaltic and andesitic volcanic ash parent materials were also shown to be unaffected. All Andisol profiles went through cambic weathering processes. Moreover, the key pedogenetic strategies were the production of short-range-order minerals through the leaching of easily dissolved elements and the coprecipitation of SiO₂ and Al₂O₃ gels. Halloysite was formed by the resilication of short-range-order minerals, while gibbsite was formed by desilication. The XRD analysis indicated that amorphous materials predominated with some HIV and kaolinite minerals were also present. Full article

Cyclocarya paliurus is a well-known multifunctional tree species and its leaves are in especially high demand for tea production and medical utilization in China. To meet the enormous requirements of its leaf production, lots of C. paliurus plantations have been established for harvesting the leaves, producing a large quantity of pruning residues during their management. In this study, biochar at different pyrolysis temperatures (300 °C, 500 °C and 700 °C) were prepared, utilizing the pruning residues, and the effects of biochar additions pyrolyzed at different temperatures on soil properties, growth and leaf secondary metabolite accumulation in C. paliurus were investigated. The results showed that the chemical properties and FT-IR spectra of wheel wingnut-based biochar were significantly influenced by the pyrolysis temperatures, and the application of biochars pyrolyzed at different temperatures significantly affected soil pH and nutrient availability, as well as the growth, nutrient uptake and secondary metabolite accumulation of C. paliurus seedlings (p < 0.05). Correlation analysis indicated that the total contents of polyphenols, flavonoids and triterpenoids in C. paliurus leaves were negatively correlated with the contents of total phosphorus (P) and total potassium (K) in the leaves, but positively correlated with the ratios of carbon (C)/nitrogen (N) and C/P. After 200 days of biochar treatment, the highest biomass production and leaf secondary metabolite accumulation in C. paliurus were obtained in the addition of biochar pyrolyzed at 500 °C. The findings from this pot experiment provide a potential application in C. paliurus plantations, though long-term field experiments are required to optimize the quantity of biochar addition, based on soil conditions and stand age at the planting sites. Full article

Revealing the variation in soil aggregate-associated organic carbon (C_org) in tea plantations of various planting ages is crucial to shed more light on the accumulation and decomposition of soil C_org in the tea-planting period. This study measured the concentrations of soil C_org, active carbon (C_act), and recalcitrant carbon (C_rec) in different-sized aggregates obtained from tea plantations of various planting ages (8, 17, 25, and 43 years old) at the soil depths of 0–20 and 20–40 cm in southern Guangxi, China. According to the wet-sieving approach, soil aggregates were classified as macro- (>0.25 mm) and micro- (<0.25 mm) aggregates, and the former were further divided into coarse (>2 mm), medium (2–1 mm), and fine (1–0.25 mm) fractions. Based on the mean weight diameter (MWD), the stability of soil aggregates was the highest in the 17-year-old tea plantations, and it was closely related to the concentration of soil C_act (0–20 cm: R² = 0.9744, p < 0.05; 20–40 cm: R² = 0.8951, p < 0.05), but not C_org (0–20 cm: R² = 0.1532, p > 0.05; 20–40 cm: R² = 0.4538, p > 0.05), during the tea-planting process. In the 0–20 and 20–40 cm soil layers, the coarse and medium macro-aggregates had higher concentrations of C_org, C_act, and C_rec, regardless of the tea-planting age; meanwhile, the soil C_act/C_rec ratio, indicating the C_org availability, increased as aggregate size increased, implying that the soil C_org was younger and more labile in coarse macro-aggregates relative to finer aggregates. Moreover, the tea-planting age significantly affected the C_org, C_act, and C_rec reserves in both soil layers. To be specific, continuous tea planting facilitated the accumulation of soil C_org and C_rec, but their reserves’ increase rates decreased over time; meanwhile, the soil C_act reserve increased during the early (from 8 to 17 years) tea-planting stage and later decreased. Therefore, during the middle (from 17 to 25 years) and late (from 25 to 43 years) tea-planting stages, maintaining the soil as an C_act pool plays a vital role in facilitating the formation and stabilization of soil aggregates in southern Guangxi, China. Full article

In this study, we aim to develop an inexpensive site-specific irrigation advisory service for resolving disadvantages related to using immobile soil moisture sensors and to the differences in irrigation needs of different tea plantations affected by variabilities in cultivars, plant ages, soil heterogeneity, and management practices. In the paper, we present methodologies to retrieve two biophysical variables, surface soil water content and canopy water content of tea trees from Sentinel-2 (S2) (European Space Agency, Paris, France) images and consider their association with crop water availability status to be used for making decisions to send an alert level. Precipitation records are used as auxiliary information to assist in determining or modifying the alert level. Once the site-specific alert level for each target plantation is determined, it is sent to the corresponding farmer through text messaging. All the processes that make up the service, from downloading an S2 image from the web to alert level text messaging, are automated and can be completed before 7:30 a.m. the next day after an S2 image was taken. Therefore, the service is operated cyclically, and corresponds to the five-day revisit period of S2, but one day behind the S2 image acquisition date. However, it should be noted that the amount of irrigation water required for each site-specific plantation has not yet been estimated because of the complexities involved. Instead, a single irrigation rate (300 t ha⁻¹) per irrigation event is recommended. The service is now available to over 20 tea plantations in the Mingjian Township, the largest tea producing region in Taiwan, free of charge since September 2020. This operational application is expected to save expenditures on buying irrigation water and induce deeper root systems by decreasing the frequency of insufficient irrigation commonly employed by local farmers. Full article

Tea (Camellia sinensis (L.) O. Kuntze) leaves are harvested multiple times annually accompanied by a large amount of nitrogen (N) removed. Therefore, tea plantations are characterized by high requirements of N. This study aimed to assess the variations of N-level, apparent N remobilization efficiency (ANRE), and N utilization efficiency (NUtE) and their dynamic changes during growing seasons for twenty tea varieties. The N-level was highest in the one bud with two leaves as the youngest category, followed by mature leaves attached to green-red stems, and then by aging leaves attached to grey stems. The dynamic N-level presented different profiles of “S”-, “U”-, and “S-like”-shape in the three categories of leaves during the growing seasons. Here, specifically defined ANRE indicated N fluxes in a specific category of leaves, showing that sources and sinks alternate during the period of two consecutive rounds of growth. The dynamic of averaged NUtE followed an “S”-shape. The results revealed annual rhythms and physiological characters related with N indices, which were variety dependent and closely related with the amount of N requirements at proper time. An optimized NUtE is a complex character determined by the combination of tea plantation management and breeding practices to achieve sustainable development with economic benefit. Full article