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Integrating agricultural production with livestock systems can restore soil quality from poorly managed pastures, reduce greenhouse gas emissions, and increase carbon sequestration. We evaluated soil fertility, litter decomposition, and stabilization in extensive continuous grazing without management, intensified rotation grazing, integrated crop-livestock, livestock-forestry, crop-livestock-forestry systems, and a forest for comparison. Intensified systems showed the highest cation concentrations due to tree nutrient use while extensive systems had lowest nitrogen and carbon:nitrogen values. Forest sites had lower phosphorus and carbon:nitrogen ratios than pastures but higher organic matter, nitrogen, and nitrogen:phosphorus ratios. Higher decomposition rates and lower stabilization factors were found in open pastures compared to areas with trees and the forest. A structural equations model indicated direct negative effects of shading by trees on decomposition rates, possibly correlated with lower temperatures or different decomposer composition due to differential litter composition in systems with trees. Increased radiation had adverse effects on the stabilization factor and positive effects mediated by soil base saturation, which was higher in more open pastures. Integrated systems including forestry presented similar decomposition rates and stabilization factors to forest sites, although the responsible mechanisms may differ, with higher nutrient limitation for decomposers in forest sites due to higher nitrogen:phosphorus ratios. Therefore, our results indicate that better management practices can improve nutrient cycling in intensified and integrated livestock production systems and contribute to stabilizing the soil organic matter. [ABSTRACT FROM AUTHOR]

Societal Impact Statement As cities grow, it is essential to understand how landscape management decisions in urban spaces alter ecosystem function. This study demonstrates that the ubiquitous practice of long‐term leaf litter removal in suburbs, even in relatively small patches of a yard, reduces the soil's ability to cycle nutrients in plant litter and results in lower amounts of carbon stored in the soil. Even two years of retaining leaves where they previously were removed is insufficient to restore decomposition rates or carbon pools. This research is an important step in creating best practices for litter management to maintain essential ecosystem functions, like carbon sequestration, water holding capacity, and soil fertility. Summary Seasonal senesced leaf litter removal eliminates considerable organic material from suburban soils annually. We test if this disturbance alters decomposition and carbon cycles and depletes soils of organic matter over time, creating persistent legacy effects. We used a factorial experimental design to implement 1–2 years of current leaf litter manipulations (remove or retain fallen leaves) within historically raked and unraked areas in suburban Maryland yards. We then compared total organic soil carbon and decomposition using a standardized substrate decomposition methodology (Tea Bag Index) across treatment plots. Long‐term litter removal in suburban yards reduced decomposition rates by 17% and total soil organic carbon concentration by up to 24% compared to areas where leaf litter was retained in situ. In contrast, short‐term management changes (1–2 years) did not significantly impact decomposition rates or total organic soil carbon concentrations. Our findings suggest that long‐term suburban litter raking creates legacy effects that alter decomposition and carbon storage process trajectories that are not easily reversed. This is important in understanding urban ecosystem function and sustainable management.

Societal Impact Statement: As cities grow, it is essential to understand how landscape management decisions in urban spaces alter ecosystem function. This study demonstrates that the ubiquitous practice of long‐term leaf litter removal in suburbs, even in relatively small patches of a yard, reduces the soil's ability to cycle nutrients in plant litter and results in lower amounts of carbon stored in the soil. Even two years of retaining leaves where they previously were removed is insufficient to restore decomposition rates or carbon pools. This research is an important step in creating best practices for litter management to maintain essential ecosystem functions, like carbon sequestration, water holding capacity, and soil fertility. Summary: Seasonal senesced leaf litter removal eliminates considerable organic material from suburban soils annually. We test if this disturbance alters decomposition and carbon cycles and depletes soils of organic matter over time, creating persistent legacy effects.We used a factorial experimental design to implement 1–2 years of current leaf litter manipulations (remove or retain fallen leaves) within historically raked and unraked areas in suburban Maryland yards. We then compared total organic soil carbon and decomposition using a standardized substrate decomposition methodology (Tea Bag Index) across treatment plots.Long‐term litter removal in suburban yards reduced decomposition rates by 17% and total soil organic carbon concentration by up to 24% compared to areas where leaf litter was retained in situ. In contrast, short‐term management changes (1–2 years) did not significantly impact decomposition rates or total organic soil carbon concentrations.Our findings suggest that long‐term suburban litter raking creates legacy effects that alter decomposition and carbon storage process trajectories that are not easily reversed. This is important in understanding urban ecosystem function and sustainable management. [ABSTRACT FROM AUTHOR]

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large‐scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass‐loss rates and stabilization factors of plant‐derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy‐to‐degrade components accumulate during early‐stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass‐loss rates and stabilization, notably in colder locations. Using TBI improved mass‐loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early‐stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models. [ABSTRACT FROM AUTHOR]

Alpine wetlands are critical ecosystems for global carbon (C) cycling and climate change mitigation. Ecological restoration projects for alpine grazing wetlands are urgently needed, especially due to their critical role as carbon (C) sinks. However, the fate of the C pool in alpine wetlands after restoration from grazing remains unclear. In this study, soil samples from both grazed and restored wetlands in Zoige (near Hongyuan County, Sichuan Province, China) were collected to analyze soil organic carbon (SOC) fractions, arbuscular mycorrhizal fungi (AMF), soil properties, and plant biomass. Moreover, the Tea Bag Index (TBI) was applied to assess the initial decomposition rate (k) and stabilization factor (S), providing a novel perspective on SOC dynamics. The results of this research revealed that the mineral-associated organic carbon (MAOC) was 1.40 times higher in restored sites compared to grazed sites, although no significant difference in particulate organic carbon (POC) was detected between the two site types. Furthermore, the increased MAOC after restoration exhibited a significant positive correlation with various parameters including S, C and N content, aboveground biomass, WSOC, AMF diversity, and NH4+. This indicates that restoration significantly increases plant primary production, litter turnover, soil characteristics, and AMF diversity, thereby enhancing the C stabilization capacity of alpine wetland soils. [ABSTRACT FROM AUTHOR]

Alpine wetlands, critical ecosystems in high-altitude mountain areas, play essential roles in water conservation, biodiversity protection, and carbon (C) sequestration. These ecosystems are particularly sensitive to climate change, with temperature and precipitation variations significantly impacting their structure and functional processes, such as litter decomposition, a key mechanism for C stabilization. This study focused on the Zoige wetland, a representative alpine wetland located on the eastern edge of the Qinghai-Tibet plateau. An incubation experiment was conducted with soil samples under simulated wet and dry moisture conditions to evaluate the environmental impacts on litter decomposition within this ecosystem. In this study, we employed the Tea Bag Index method, utilizing standardized litter, alongside native litter bags to compare the decomposition processes. This comparison between the uniform composition of standardized litter and the chemically diverse native plant litter aims to provide a comprehensive understanding of litter decomposition dynamics in alpine wetland ecosystems. Our finding showed that both standardized and native litter decomposition significantly decreased under dry conditions, in contrast to wetter condition. The components of both standardized and native litter exhibited a decrease over time, with the easily decomposable fractions breaking down swiftly, in contrast to the slower decomposition of the more resistant components. Furthermore, soil exo-enzyme activities varied significantly with environmental conditions. Wet conditions were observed to enhance soil microbial activity, whereas dry conditions resulted in shifts in microbial biomass C and nitrogen, indicative of drought resilience. The correlation analysis revealed that the composition of native litter is the primary factor influencing its decomposition. In contrast, the decomposition of standardized litter was influenced by both its composition and soil microbial activity. Thus, the distinction between the influences on native and standardized litter decomposition highlights the necessity of considering both litter quality and microbial interaction in ecological studies. This approach offers critical insight into the advantages and limitations of each decomposition methodology within alpine wetland ecosystems.

Soils of high mountains significantly differ in the soil organic matter (SOM) content, but the factors of such diversity are still not completely known. We have studied physicochemical and microbiological soil properties and have estimated parameters of standard material decomposition based on the Tea bag index (TBI)—stabilization factor (STBI) and decomposition constant (kTBI)—in 16 subalpine, alpine, and subnival plant communities of the Teberda National Park (northwestern Caucasus) We tested the following hypotheses: (1) SOM is one of predictors of STBI and kTBI in the high-mountain zone along with other physicochemical soil properties; (2) the SOM content is greater at high STBI and low kTBI; (3) the SOM content correlates with belowground plant productivity. The main gradients of the studied soils include moisture content (automorphic vs. hydromorphic soils) and the concurrent SOM accumulation, as well as the altitudinal gradient (a decrease of soil basal respiration with altitude). The enrichment in nitrogen (e.g. the SOM quality) of the labile fraction is the best predictor of the decomposition rate. The parameter STBI decreases with the increase in the total carbon content and loss on ignition, while the correlation between kTBI and SOM is positive only in automorphic soils. Thus, the soils rich in organic matter are characterized by low stabilization factor and relatively high decomposition rate. The SOM content in plant communities with herbaceous dominants is in positive correlation with the production of fine roots, which reflects the important role of productivity in organic matter accumulation. [ABSTRACT FROM AUTHOR]

Tundra soils are one of the world's largest organic carbon stores, yet this carbon is vulnerable to accelerated decomposition as climate warming progresses. The landscape‐scale controls of litter decomposition are poorly understood in tundra ecosystems, which hinders our understanding of the global carbon cycle. We examined the extent to which the thermal sum of surface air temperature, soil moisture and permafrost thaw depth influenced litter mass loss and decomposition rates (k), and at which spatial thresholds an environmental variable becomes a reliable predictor of decomposition, using the Tea Bag Index protocol across a heterogeneous tundra landscape on Qikiqtaruk–Herschel Island, Yukon, Canada. We found greater green tea litter mass loss and faster decomposition rates (k) in wetter areas within the landscape, and to a lesser extent in areas with deeper permafrost active layer thickness and higher surface thermal sums. We also found higher decomposition rates (k) on north‐facing relative to south‐facing aspects at microsites that were wetter rather than warmer. Spatially heterogeneous belowground conditions (soil moisture and active layer depth) explained variation in decomposition metrics at local scales (< 50 m2) better than thermal sum. Surprisingly, there was no strong control of elevation or slope on litter decomposition. Our results reveal that there is considerable scale dependency in the environmental controls of tundra litter decomposition, with moisture playing a greater role than the thermal sum at < 50 m2 scales. Our findings highlight the importance and complexity of microenvironmental controls on litter decomposition in estimates of carbon cycling in a rapidly warming tundra biome. [ABSTRACT FROM AUTHOR]

Tidal salt marshes are widespread along the World's coasts, and are ecologically and economically important as they provide several valuable ecosystem services. In particular, their significant primary production, coupled with sustained vertical accretion rates, enables marshes to sequester and store large amounts of organic carbon and makes them one of the most carbon‐rich ecosystems on Earth. Organic carbon accumulation results from the balance between inputs, that is, organic matter produced by local plants or imported, and outputs through decomposition and erosion. Additionally, organic matter deposition actively contributes to marsh vertical accretion, thus critically affecting the resilience of marsh ecosystems to rising relative sea levels. A better understanding of organic‐matter dynamics in salt marshes is key to address salt‐marsh conservation issues and to elucidate marsh importance within the global carbon cycle. Toward this goal, we empirically derived rates of organic matter decomposition by burying 712 commercially available tea bags at different marshes in the microtidal Venice Lagoon (Italy), and by analyzing them following the Tea Bag Index protocol. We find values of the decomposition rate (k) and stabilization factor (S) equal to 0.012 ± 0.003 days−1 and 0.15 ± 0.063, respectively. Water temperature critically affects organic matter decomposition, enhancing decomposition rates by 8% per °C on average. We argue that, at least in the short term, the amount of undecomposed organic matter that actively contributes to carbon sequestration and marsh vertical accretion strongly depends on the initial organic matter quality, which is a function of marsh and vegetation characteristics. Plain Language Summary: Salt marshes are important coastal environments regularly flooded by the tide and dominated by herbaceous plants, providing several valuable ecosystem services. They are, however, threatened by the effects of climate changes and human interferences. As organic matter accumulated in salt‐marsh soil importantly contribute to surface elevation necessary for marshes to keep up with sea level rise and to store atmospheric carbon, this project aims to improve our understanding of decomposition processes affecting organic matter preservation and their controls in salt‐marsh environment. Toward this goal, following the so‐called Tea Bag Index protocol, we buried 712 commercially available tea bags in salt‐marsh soils of the Venice Lagoon (Italy) measuring the reduction of their organic content due to decomposition processes after 3 months. Our results confirm that salt marshes are among biomes with the slowest decomposition rates. However, we observed a loss of about two‐thirds of the initial labile organic mass after 90 days and that initial litter quality, depending on litter and vegetation characteristics, exerts a primary control on the amount of preserved organic matter contributing to carbon sequestration and marsh accretion. Key Points: Decomposition rates in Venice marshes display a mean value of 0.012 ± 0.003 days−1, confirming them among biomes with the slowest decomposition ratesWe find that a one degree increase in temperature leads to a 8% increase in decomposition ratesLitter quality exerts a primary control on the amount of preserved organic matter contributing to carbon sequestration and marsh accretion [ABSTRACT FROM AUTHOR]

The Bag Index (TBI) is a novel approach using standardized materials (i.e., commercial tea bags) to evaluate organic matter decomposition by determining two indexes: the early stage decomposition constant k (k_TBI) and litter stabilization factor S (S_TBI). k_TBI is defined as the decomposition constant of an asymptote model describing the decomposition curve of rooibos tea, whereas S is the ratio of the stabilized to total hydrolysable fractions of green tea. However, it was recently revealed that both k_TBI and S_TBI deviate from the actual S and k values accurately determined by fitting an asymptote model to the time series mass of green and rooibos teas remaining (k_fitting and S_fitting, respectively). Nevertheless, k_TBI and S_TBI, which can be determined in a cost- and labor-effective manner, might indicate the relative values of k_fitting and S_fitting across different soils and be useful for comparative analyses. Therefore, this study investigated the positive correlations of k_TBI and S_TBI with k_fitting and S_fitting, respectively, in which case these indexes are useful for comparative analyses. However, the result showed that k_TBI was negatively correlated with k_fitting. This study underscores the importance of obtaining time-series data for accurately determining the decomposition constant of an asymptote model describing the decomposition curve of rooibos tea. S_TBI was positively correlated with S_fitting, implying that S_TBI can be used as an indicator of S.

The Tea Bag Index (TBI) approach is a standardized method for assessing litter decomposition in terrestrial ecosystems. This method allows determination of the stabilized portion of the hydrolysable fraction during the decomposition process, and derivation of a decomposition constant (k) using single measurements of the mass-loss ratios of green and rooibos teas. Although this method is being applied to aquatic systems, it has not been tested if the TBI-based decomposition curves accurately represent the changes in remaining mass of the teas in these environments, where initial leaching tends to be higher than in terrestrial ecosystems. Here, we first tested a critical assumption of the TBI method that green tea decomposition plateaus during the standard incubation period of 90 days, and then tested the accuracy of a TBI-based asymptote model, which was determined using another essential assumption of the TBI approach: the ratio of the decomposable hydrolysable fraction to the total hydrolysable fraction of rooibos tea is the same as that of green tea. Validation data were obtained by incubating tea bags in water samples taken from a stream, a pond, and the ocean in Kumamoto, Japan. We found that green tea decomposition did not plateau during the 90-day period, contradicting a key assumption of the TBI method. The other key assumption was also violated, because the TBI-based asymptote models disagreed with actual decomposition data. Subtracting the leachable fraction from the initial tea mass improved the TBI-based model, but discrepancies with the actual decomposition data remained. Thus, we conclude that the TBI approach, which was developed for a terrestrial environment, is not appropriate for aquatic ecosystems.

Earthworms and soil microorganisms contribute to soil health, quality, and fertility, but their importance in agricultural soils is often underestimated. This study aims at examining whether and to what extent the presence of earthworms (Eisenia sp.) affected the (a) soil bacterial community composition, (b) litter decomposition, and (c) plant growth (Brassica oleracea L., broccoli; Vicia faba L., faba bean). We performed a mesocosm experiment in which plants were grown outdoors for four months with or without earthworms. Soil bacterial community structure was evaluated by a 16S rRNA-based metabarcoding approach. Litter decomposition rates were determined by using the tea bag index (TBI) and litter bags (olive residues). Earthworm numbers almost doubled throughout the experimental period. Independently of the plant species, earthworm presence had a significant impact on the structure of soil bacterial community, in terms of enhanced α- and β-diversity (especially that of Proteobacteria, Bacteroidota, Myxococcota, and Verrucomicrobia) and increased 16S rRNA gene abundance (+89% in broccoli and +223% in faba bean). Microbial decomposition (TBI) was enhanced in the treatments with earthworms, and showed a significantly higher decomposition rate constant (kTBI) and a lower stabilization factor (STBI), whereas decomposition in the litter bags (dlitter) increased by about 6% in broccoli and 5% in faba bean. Earthworms significantly enhanced root growth (in terms of total length and fresh weight) of both plant species. Our results show the strong influence of earthworms and crop identity in shaping soil chemico-physical properties, soil bacterial community, litter decomposition and plant growth. These findings could be used for developing nature-based solutions that ensure the long-term biological sustainability of soil agro- and natural ecosystems. [ABSTRACT FROM AUTHOR]

Researchers have studied the impact of various anthropogenic activities on litter decomposition rates because of their large impact on the future carbon budget and climate change. However, any assessment of the global-scale impact of anthropogenic activity on litter decomposition requires standardized methods that can exclude the variability of litter chemistry. The Tea Bag Index (TBI) is widely used as a standardized method to obtain both the decomposition constant k of early-stage litter decomposition and the stabilization factor S. Recently, a tea bag manufacturer changed the materials and size of the tea bag mesh from a 0.25 mm woven mesh to a nonuniform, nonwoven mesh. To test whether these changes in mesh materials have any effect on the TBI approach, an incubation study was performed. Obtaining time series decomposition data for both green and rooibos teas, two essential assumptions of the TBI approach were examined: (i) that most of the unstabilized hydrolyzable fraction of green tea is decomposed within 90 days (unless the environment is unfavorable for decomposition) and (ii) the S of green tea is equal to that of rooibos tea. The results did not show a clear breakdown of the first assumption of the TBI approach due to the changes in mesh materials, and they did not support the second assumption. The S of rooibos tea determined by fitting an asymptote model to the time series data was significantly larger than the TBI-based S. In conclusion, the TBI may be undeterminable using nonwoven tea bags.

The Bag Index (TBI) is a novel approach using standardized materials (i.e., commercial tea bags) to evaluate organic matter decomposition by determining two indexes: the early stage decomposition constant k (k_TBI) and litter stabilization factor S (S_TBI). k_TBI is defined as the decomposition constant of an asymptote model describing the decomposition curve of rooibos tea, whereas S is the ratio of the stabilized to total hydrolysable fractions of green tea. However, it was recently revealed that both k_TBI and S_TBI deviate from the actual S and k values accurately determined by fitting an asymptote model to the time series mass of green and rooibos teas remaining (k_fitting and S_fitting, respectively). Nevertheless, k_TBI and S_TBI, which can be determined in a cost- and labor-effective manner, might indicate the relative values of k_fitting and S_fitting across different soils and be useful for comparative analyses. Therefore, this study investigated the positive correlations of k_TBI and S_TBI with k_fitting and S_fitting, respectively, in which case these indexes are useful for comparative analyses. However, the result showed that k_TBI was negatively correlated with k_fitting. This study underscores the importance of obtaining time-series data for accurately determining the decomposition constant of an asymptote model describing the decomposition curve of rooibos tea. S_TBI was positively correlated with S_fitting, implying that S_TBI can be used as an indicator of S. [ABSTRACT FROM AUTHOR]

Peatlands provide multiple ecosystem services, including extensive carbon sequestration and storage, yet many peatlands have been degraded or destroyed. Peatlands' carbon storage capacity is connected to inherently low decomposition rates, causing the buildup of organic matter. This pattern could be explained by waterlogged conditions that reduce the amount of available oxygen for the decomposer community, a low pH that inhibits bacterial decomposition, or colder temperatures lowering metabolic rates. This study focused on edge effects on decomposition in the transition zone (lagg) between Sphagnum bogs and the surrounding forest, with the expectation that decomposition is lowest in the bog and highest in the forest but with a mix of factors causing intermediate decomposition rates near the bog edge. Transitional decomposition rates were measured across six bogs in central Sweden during the summer of 2021, following the Tea Bag Index. Three 20‐m transects, each containing seven pairs of tea bags, were buried across the margins of each bog, centered at the edge of the Sphagnum moss. Soil moisture content, pH, and plant composition were also recorded at each burial site, and temperature loggers placed evenly among four of the bogs. Our results confirmed our hypothesis regarding edge effects, with soil moisture levels showing a strong negative interaction with decomposition rate. The interaction between pH and decomposition rate was significant, but with an unexpected negative relation, most likely due to low pH in the surrounding forest. Temperature displayed no significance, and plants indicative of low decomposition rates included Vaccinium oxycoccos, Drosera rotundifolia, and Sphagnum species. In contrast to other studies, we did not find an increase in decomposition with increased species richness among the studied bog ecosystems. In conclusion, there is an edge effect on decomposition, and maintaining, or restoring, the hydrology of a peatland is the most important factor for continued carbon storage, with a rough estimation of an area decomposition rate possible to be estimated based on its vegetation. [ABSTRACT FROM AUTHOR]

Abstract Peatlands provide multiple ecosystem services, including extensive carbon sequestration and storage, yet many peatlands have been degraded or destroyed. Peatlands' carbon storage capacity is connected to inherently low decomposition rates, causing the buildup of organic matter. This pattern could be explained by waterlogged conditions that reduce the amount of available oxygen for the decomposer community, a low pH that inhibits bacterial decomposition, or colder temperatures lowering metabolic rates. This study focused on edge effects on decomposition in the transition zone (lagg) between Sphagnum bogs and the surrounding forest, with the expectation that decomposition is lowest in the bog and highest in the forest but with a mix of factors causing intermediate decomposition rates near the bog edge. Transitional decomposition rates were measured across six bogs in central Sweden during the summer of 2021, following the Tea Bag Index. Three 20‐m transects, each containing seven pairs of tea bags, were buried across the margins of each bog, centered at the edge of the Sphagnum moss. Soil moisture content, pH, and plant composition were also recorded at each burial site, and temperature loggers placed evenly among four of the bogs. Our results confirmed our hypothesis regarding edge effects, with soil moisture levels showing a strong negative interaction with decomposition rate. The interaction between pH and decomposition rate was significant, but with an unexpected negative relation, most likely due to low pH in the surrounding forest. Temperature displayed no significance, and plants indicative of low decomposition rates included Vaccinium oxycoccos, Drosera rotundifolia, and Sphagnum species. In contrast to other studies, we did not find an increase in decomposition with increased species richness among the studied bog ecosystems. In conclusion, there is an edge effect on decomposition, and maintaining, or restoring, the hydrology of a peatland is the most important factor for continued carbon storage, with a rough estimation of an area decomposition rate possible to be estimated based on its vegetation.

How the anthropogenic addition of nutrients, especially nitrogen (N), impacts litter decomposition has attracted extensive attention, but how environmental factors other than nutrients affect the impacts of N addition on litter decomposition is less understood. Since different local litters could respond differently to N addition, standard materials are necessary for comparing the impacts among various environments. The present study tested if tea bags used for the Tea Bag Index (TBI) approach, i.e., constructing an asymptote model by using a green tea decomposition datum and a rooibos tea decomposition datum (single measurement in time), can be standard materials for testing the impacts of N addition on litter decomposition in aquatic ecosystems. A laboratory incubation experiment was performed using a water sample taken from a stream in Kumamoto, Japan. Since a recent study suggested that the TBI approach may be inapplicable to aquatic ecosystems, a time-series data approach, i.e., fitting models to time-series mass loss data of tea bags, was also used for testing if tea bag decomposition can pick up the impacts of N addition on aquatic litter decomposition. The time-series data approach demonstrated that N addition significantly suppressed rooibos tea decomposition, whereas green tea decomposition was not affected by N addition. The TBI approach was unsuitable for testing the sensitivity of the response of tea bag decomposition to N addition because the TBI-based asymptote model failed to predict the observed data, confirming the suggestion by a previous study. Overall, the present study suggested that the tea bags can be used as standard materials for testing the impacts of N addition on litter decomposition in aquatic ecosystems, but only when using a time-series measurement and not the TBI.

Agricultural management is mainly driven by soil degradation processes, where the synthetic fertilization regime is an important component in the disconnection of the ecological process that provides stability to soil functions. The soils around Mexico City, inside the Soil Conservation Zone (SCZ), have been used for a long time for agricultural production, depleting the soil organic matter and deteriorating soil structure. In this work, we present how different fertilization management methods could produce short-term changes in both organic matter content and soil structure of volcanic soils (Andic Anthrosols) inside the SCZ. We performed a field experiment where different kinds of fertilization systems were used: synthetic NPK, urea, cattle manure, vermicompost, and fertilization suppression on soil cultivated with Avena sativa L. After the oat harvest, we collected topsoil samples from each treatment to evaluate microstructure in thin sections (morphometry and micromorphology, including visual estimation of the organic residues decomposition), as well as organic matter stock, distribution, and decomposition, tested with a Tea Bag Index (TBI) experiment. Morphometric results showed that the pores' shape, size, and connectivity were improved by organic amendments. The visual evaluation of the degradation of the organic residues evidenced the high decomposition and low stabilization rates under inorganic fertilization and fertilization suppression treatments. However, we did not observe statistical differences in the decomposition rate (k) and stabilization factor (S) derived from the TBI. All findings suggest a) that the use of micromorphological and SOM functional characteristics is suitable for the integral evaluation of short-term changes in soils under agricultural management and b) the synthetic fertilization maintains a poorly structured soil with a low functionality condition that can be improved in a short-term improved with fertilization based on organic amendment addition. • Organic amendments improved the pores' shape, size, and connectivity. • High decomposition and low stabilization rates of OM under inorganic fertilization. • Micromorphology and SOM fractionation are suitable for short-term soil changes. [ABSTRACT FROM AUTHOR]

Decomposition is essential to carbon, nutrient, and energy cycling among and within ecosystems. Several methods have been proposed for studying litter decomposition by using a standardized and commercially available substrate. One of these methods is the Tea Bag Index (TBI) which uses tea bags (green and rooibos tea) incubated for ~90 days. The TBI is now applied all over the globe, but despite its usefulness and wide application, the TBI (as well as other methods) does not explicitly account for the differences in potential loss of litter mass due to initial leaching in habitats with large differences in moisture. We, therefore, studied the short‐term mass losses (3–4 h) due to initial leaching under field and laboratory conditions for green and rooibos tea using the TBI and contextualized our findings using existing long‐term mass loss (90 days) in the field for both aquatic and terrestrial environments. For both tea litter types, we found a fast initial leaching rate, which could be mistaken for decomposition through microbial activity. This initial leaching was higher than the hydrolyzable fraction given in the description of the TBI. We also found that leaching increased with increasing temperature and that leaching in terrestrial environments with high soil moisture (>90%) is almost as large as in aquatic environments. When comparing our findings to long‐term studies, we found that up to 30–50% of the mass loss of green tea reported as decomposition could be lost through leaching alone in high moisture environments (>90% soil moisture and submerged). Not accounting for such differences in initial leaching across habitats may lead to a systematic overestimation of the microbial decomposition in wet habitats. Future studies of microbial decomposition should adjust their methods depending on the habitat, and clearly specify the type of decomposition that the study focuses on. [ABSTRACT FROM AUTHOR]

Researchers have studied the impact of various anthropogenic activities on litter decomposition rates because of their large impact on the future carbon budget and climate change. However, any assessment of the global-scale impact of anthropogenic activity on litter decomposition requires standardized methods that can exclude the variability of litter chemistry. The Tea Bag Index (TBI) is widely used as a standardized method to obtain both the decomposition constant k of early-stage litter decomposition and the stabilization factor S. Recently, a tea bag manufacturer changed the materials and size of the tea bag mesh from a 0.25 mm woven mesh to a nonuniform, nonwoven mesh. To test whether these changes in mesh materials have any effect on the TBI approach, an incubation study was performed. Obtaining time series decomposition data for both green and rooibos teas, two essential assumptions of the TBI approach were examined: (i) that most of the unstabilized hydrolyzable fraction of green tea is decomposed within 90 days (unless the environment is unfavorable for decomposition) and (ii) the S of green tea is equal to that of rooibos tea. The results did not show a clear breakdown of the first assumption of the TBI approach due to the changes in mesh materials, and they did not support the second assumption. The S of rooibos tea determined by fitting an asymptote model to the time series data was significantly larger than the TBI-based S. In conclusion, the TBI may be undeterminable using nonwoven tea bags. [ABSTRACT FROM AUTHOR]

The Tea Bag Index (TBI), a novel approach to assessing organic matter decomposition using commercial tea bags, has been increasingly used in academic studies worldwide. This approach was designed to obtain an early-stage decomposition constant (k) indicative of early-stage decomposition rates and a litter stabilization factor (S) indicative of long-term carbon stability by using two types of teas—green and rooibos. However, despite the worldwide usage of the method, the accuracy of this approach has never been validated in terrestrial ecosystems. Here, the validity of this approach was tested by examining the two essential premises of the TBI using a laboratory incubation experiment. The first premise of the TBI—namely, that the unstabilized hydrolyzable fraction of green tea is mostly decomposed within 90 days—did not hold in the present study, which caused overestimations of the S of green tea. The second premise—namely, that the ratio of stabilized to total hydrolyzable fractions (i.e., S) of rooibos tea is equal to that of green tea—was also rejected, which resulted in substantial underestimations of the S of rooibos tea and k. Overall, the TBI largely underestimated the S of rooibos tea and k (more than 1.5 and 5 times smaller than those determined by time-series data, respectively). The present study suggests that time-series mass loss data of rooibos tea should be obtained to accurately determine k, rather than assuming that the S of rooibos tea is equal to that of green tea.

Moso bamboo (Phyllostachys edulis) is currently distributed across a wide geographical area in East Asia. As a common bamboo species occurring along a broad environmental gradient, there is a need to understand how environmental and biotic drivers affect belowground processes at large scales. In this study, we investigated the influence of climate, soil properties, stand characteristics, and organic matter input parameters as potential drivers of the initial decomposition process in Moso bamboo stands at a regional scale. Using the Tea Bag Index method, we estimated the initial decomposition rate (k) and stabilization factor (S; potential long-term carbon storage) from standard litter incubated at 13 sites across southern Japan and Taiwan. We found that both decomposition parameters were strongly affected by the climate. The climatic conditions during the incubation period better explained the variance in k. In contrast, the long-term climate was more important for S. Notably, temperature and precipitation interactively affected the initial decomposition rates. This interaction showed that in warmer sites, precipitation increased k, whereas in cooler sites, precipitation had no effect or even decreased k. Soil parameters had no influence on k and only had minor effects on S. A structural equation model showed that the stabilization factor was indirectly affected by stand density, which suggests that higher bamboo densities could increase litter stabilization by increasing above-and below-ground organic matter input. Our study highlights the central role of climate in controlling decomposition processes in Moso bamboo stands on a broad scale. Moreover, differences in stand structure can indirectly affect potential soil carbon storage through changes in organic matter input and soil conditions.

Abstract Background Nutrient cycling in tropical forests has a large importance for primary productivity, and decomposition of litterfall is a major process influencing nutrient balance in forest soils. Although large-scale factors strongly influence decomposition patterns, small-scale factors can have major influences, especially in old-growth forests that have high structural complexity and strong plant-soil correlations. Here we evaluated the effects of forest structure and soil properties on decomposition rates and stabilization of soil organic matter using the Tea Bag Index (TBI) in an old-growth riparian forest in southeastern Brazil. These data sets were described separately using Principal Components Analysis (PCA). The main axes for each analysis, together with soil physical properties (clay content and soil moisture), were used to construct structural equations models that evaluated the different parameters of the TBI, decomposition rates and stabilization factor. The best model was selected using Akaike’s criterion. Results Forest structure and soil physical and chemical properties presented large variation among plots within the studied forest. Clay content was strongly correlated with soil moisture and the first PCA axis of soil chemical properties, and model selection indicated that clay content was a better predictor than this axis. Decomposition rates presented a large variation among tea bags (0.009 and 0.098 g·g− 1·d− 1) and were positively related with forest structure, as characterized by higher basal area, tree density and larger trees. The stabilization factor varied between 0.211–0.426 and was related to forest stratification and soil clay content. Conclusions The old-growth forest studied presented high heterogeneity in both forest structure and soil properties at small spatial scales, that influenced decomposition processes and probably contributed to small-scale variation in nutrient cycling. Decomposition rates were only influenced by forest structure, whereas the stabilization factor was influenced by both forest structure and soil properties. Heterogeneity in ecological processes can contribute to the resilience of old-growth forests, highlighting the importance of restoration strategies that consider the spatial variation of ecosystem processes.

To understand the global impact of anthropogenic activities on litter decomposition, it is necessary to obtain large decomposition datasets using a standardized method. The Tea Bag Index (TBI) approach determines the decomposition constant (k) of an asymptote model of litter decomposition and a stabilized ratio of the hydrolyzable fraction (stabilization factor S) using a single measurement of the mass loss ratios of green and rooibos teas. This approach requires the assumption that S is equal for rooibos and green tea. Here, we performed a field experiment in four temperate forest stands that demonstrated that this assumption is not always true. In a forest on limestone soils, more than half of the mass loss ratios of rooibos tea exceeded the decomposable fraction predicted by the assumption and the green tea data, which implies that the S was higher for green tea than rooibos tea. This indicated that the main assumption is not always true. We also performed a random simulation study that demonstrated that the derivation of k based on this assumption leads to a biased positive relationship between k and S, regardless of whether the assumption is correct. Thus, we suggest that the use of k and S in an identical analysis causes biased results because these variables are not independent of each other under the assumption. These risks should be considered depending on the purpose of studies that use the TBI approach. [ABSTRACT FROM AUTHOR]

Background: Attempts to restore degraded highlands by tree planting are common in East Africa. However, up till now, little attention has been given to effects of tree species choice on litter decomposition and nutrient recycling. Method: In this study, three indigenous and two exotic tree species were selected for a litter decomposition study. The objective was to identify optimal tree species combinations and tree diversity levels for the restoration of degraded land via enhanced litter turnover. Litterbags were installed in June 2019 into potential restoration sites (disturbed natural forest and forest plantation) and compared to intact natural forest. The tested tree leaf litters included five monospecific litters, ten mixtures of three species and one mixture of five species. Standard green and rooibos tea were used for comparison. A total of 1,033 litters were retrieved for weight loss analysis after one, three, six, and twelve months of incubation. Results: The finding indicates a significant effect of both litter quality and litter diversity on litter decomposition. The nitrogen-fixing native tree Millettia ferruginea showed a comparable decomposition rate as the fast decomposing green tea. The exotic conifer Cupressus lusitanica and the native recalcitrant Syzygium guineense have even a lower decomposition rate than the slowly decomposing rooibos tea. A significant correlation was observed between litter mass loss and initial leaf litter chemical composition. Moreover, we found positive non-additive effects for litter mixtures including nutrient-rich and negative non-additive effects for litter mixtures including poor leaf litters respectively. Conclusion: These findings suggest that both litter quality and litter diversity play an important role in decomposition processes and therefore in the restoration of degraded tropical moist evergreen forest [ABSTRACT FROM AUTHOR]

Citizen science is becoming a significant contribution to large scale soil surveys. TeaComposition is a citizen science project introducing the Tea Bag Index (TBI) method to students in Australia to support research on soil decomposition using tea bags (green and rooibos). Soil microbial driven decomposition is an essential soil function that releases soil organic matter (SOM) and nutrients, i.e., soil ecosystem services. The TBI experiments enable citizens to understand this process (increasing soil connectivity) and this information is valuable for assessing urban soil conditions. With 430 TBI in-field incubations between 2017 and 2020, this project engaged more than 3200 students who tested the TBI method on more than 50 school grounds and collected soil samples for analyses of soil properties. Approximately 50% of the tea bags were recovered and mean TBI parameters were: decomposition rate (k) = 0.02 gd−1 and stabilisation factor (S) = 0.32. Soil texture, SOC and SI had the most significant relationships with TBI. Clay and Slaking Index (SI) had negative impacts on k (rs = -0.37, -0.22, p ≤ 0.05, respectively) and SOC had a negative effect for S (rs=-0.27; p ≤ 0.05). These results suggest a combination of high clay and SOC may be related to reduced potential for C sequestration. Regarding citizen science, this study suggests further research using a local tea brand and shorter burials. This suggestion aims to increase Australian citizen participation.

In cranberry production systems, stands are covered by 1-5 cm of sand every 2-5 years to stimulate plant growth, resulting in alternate layers of sand and litter in soil upper layers. However, almost intact twigs and leaves remain in subsurface layers, indicating a slow decomposition rate. The Tea Bag Index (TBI) provides an internationally standardized methodology to compare litter decomposition rates (k) and stabilization (S) among terrestrial ecosystems. However, TBI parameters may be altered by time-dependent changes in the contact between litter and their immediate environment. The aims of this study were to determine the TBI of cranberry agroecosystems and compare it to the TBI of other terrestrial ecosystems. Litters were standardized green tea, standardized rooibos tea, and cranberry residues collected on the plantation floor. Litter decomposition was monitored during two consecutive years. Added N did not affect TBI parameters (k and S) due to possible N leaching and strong acidic soil condition. Decomposition rates (k) averaged (mean ± SD) 9.7 x 10-3 day-1 ± 1.6 x 10-3 for green tea, 3.3 x 10-3 day-1 ± 0.8 x 10-5 for rooibos tea, and 0.4 x 10-3 day-1 ± 0.86 x 10-3 for cranberry residues due to large differences in biochemical composition and tissue structure. The TBI decomposition rate (k) was 0.006 day-1 ± 0.002 in the low range among terrestrial ecosystems, and the stabilization factor (S) was 0.28 ± 0.08, indicating high potential for carbon accumulation in cranberry agroecosystems. Decomposition rates of tea litters were reduced by fractal coefficients of 0.6 for green tea and 0.4 for rooibos tea, indicating protection mechanisms building up with time in the tea bags. While the computation of the TBI stabilization factor may be biased because the green tea was not fully decomposed, fractal kinetics could be used as additional index to compare agroecosystems. [ABSTRACT FROM AUTHOR]

Abstract Human activities have led to increased deposition of nitrogen (N) and phosphorus (P) into soils. Nutrient enrichment of soils is known to increase plant biomass and rates of microbial litter decomposition. However, interacting effects of hydrologic position and associated changes to soil moisture can constrain microbial activity and lead to unexpected nutrient feedbacks on microbial community structure–function relationships. Examining feedbacks of nutrient enrichment on decomposition rates is essential for predicting microbial contributions to carbon (C) cycling as atmospheric deposition of nutrients persists. This study explored how long‐term nutrient addition and contrasting litter chemical composition influenced soil bacterial community structure and function. We hypothesized that long‐term nutrient enrichment of low fertility soils alters bacterial community structure and leads to higher rates of litter decomposition especially for low C:N litter, but low‐nutrient and dry conditions limit microbial decomposition of high C:N ratio litter. We leveraged a long‐term fertilization experiment to test how nutrient enrichment and hydrologic manipulation (due to ditches) affected decomposition and soil bacterial community structure in a nutrient‐poor coastal plain wetland. We conducted a litter bag experiment and characterized litter‐associated and bulk soil microbiomes using 16S rRNA bacterial sequencing and quantified litter mass losses and soil physicochemical properties. Results revealed that distinct bacterial communities were involved in decomposing higher C:N ratio litter more quickly in fertilized compared to unfertilized soils especially under drier soil conditions, while decomposition rates of lower C:N ratio litter were similar between fertilized and unfertilized plots. Bacterial community structure in part explained litter decomposition rates, and long‐term fertilization and drier hydrologic status affected bacterial diversity and increased decomposition rates. However, community composition associated with high C:N litter was similar in wetter plots with available nitrate detected, regardless of fertilization treatment. This study provides insight into long‐term fertilization effects on soil bacterial diversity and composition, decomposition, and the increased potential for soil C loss as nutrient enrichment and hydrology interact to affect historically low‐nutrient ecosystems.

Purpose: The standardized 'Tea Bag Index' enables comparisons of litter decomposition rates, a key component of carbon cycling, across ecosystems. However, tea 'litter' may leach more than other plant litter, skewing comparisons of decomposition rates between sites with differing moisture conditions. Therefore, some researchers leach tea bags before field incubation. This decreases comparability between studies, and it is unclear if this modification is necessary. Methods: We submerged green and rooibos tea bags in water, and measured their leaching losses over time (2 min – 72 h). We also compared leaching of tea to leaf and root litter from other plant species, and finally, compared mass loss of pre-leached and standard tea bags in a fully factorial incubation experiment differing in soil moisture (wet and dry) and soil types (sand and peat). Results: Both green and rooibos tea leached strongly, levelling-off at about 40% and 20% mass loss, respectively. Mass loss from leaching was highest in green tea followed by leaves of other plants, then rooibos tea, and finally roots of other plants. When incubated for 4 weeks, both teas showed lower mass loss when they had been pre-leached compared to standard tea bags. However, these differences between standard and pre-leached tea bags were similar in moist vs. dry soils, both in peat and in sand. Conclusions: Thus, despite large leaching losses, we conclude that leaching tea bags before field or lab incubation is not necessary to compare decomposition rates between systems, ranging from as much as 5% to 25% soil moisture. [ABSTRACT FROM AUTHOR]

Human activities have led to increased deposition of nitrogen (N) and phosphorus (P) into soils. Nutrient enrichment of soils is known to increase plant biomass and rates of microbial litter decomposition. However, interacting effects of hydrologic position and associated changes to soil moisture can constrain microbial activity and lead to unexpected nutrient feedbacks on microbial community structure–function relationships. Examining feedbacks of nutrient enrichment on decomposition rates is essential for predicting microbial contributions to carbon (C) cycling as atmospheric deposition of nutrients persists. This study explored how long‐term nutrient addition and contrasting litter chemical composition influenced soil bacterial community structure and function. We hypothesized that long‐term nutrient enrichment of low fertility soils alters bacterial community structure and leads to higher rates of litter decomposition especially for low C:N litter, but low‐nutrient and dry conditions limit microbial decomposition of high C:N ratio litter. We leveraged a long‐term fertilization experiment to test how nutrient enrichment and hydrologic manipulation (due to ditches) affected decomposition and soil bacterial community structure in a nutrient‐poor coastal plain wetland. We conducted a litter bag experiment and characterized litter‐associated and bulk soil microbiomes using 16S rRNA bacterial sequencing and quantified litter mass losses and soil physicochemical properties. Results revealed that distinct bacterial communities were involved in decomposing higher C:N ratio litter more quickly in fertilized compared to unfertilized soils especially under drier soil conditions, while decomposition rates of lower C:N ratio litter were similar between fertilized and unfertilized plots. Bacterial community structure in part explained litter decomposition rates, and long‐term fertilization and drier hydrologic status affected bacterial diversity and increased decomposition rates. However, community composition associated with high C:N litter was similar in wetter plots with available nitrate detected, regardless of fertilization treatment. This study provides insight into long‐term fertilization effects on soil bacterial diversity and composition, decomposition, and the increased potential for soil C loss as nutrient enrichment and hydrology interact to affect historically low‐nutrient ecosystems. [ABSTRACT FROM AUTHOR]

Abstract Alpine snowbed communities are characterized as having areas of longer lasting snow cover duration compared with the surrounding landscape. The predictable accumulation of deep and long‐lasting snow on lee side ridges drives a unique ecology, providing stable microclimatic conditions under the snow through winter, supplying meltwater in spring, and controlling many biological processes. The timing and rate of plant litter decomposition are key controls on the nutrient balance of snowbed communities, and are thought to be strongly driven by snow dynamics. However, little is known about how the patterns and timing of snowmelt affect decomposition, nor how long these effects last into the growing season. We investigated the influence of snowmelt timing on decomposition rates across an alpine snowbed community by burying standardized plant litter (rooibos and green tea), at three incubation times (whole year, winter+spring, and summer), across three snowmelt zones. Decomposition rate (as percent mass loss of tea) was significantly higher in early‐melting zones compared to late‐melting zones, particularly for the recalcitrant litter (rooibos tea). Decomposition was also affected by the season(s) of incubation and was greatest where tea was buried for the whole year, or only over summer, with winter + spring only incubations decomposing the least. However, decomposition was more strongly influenced by litter quality (type of tea) than either the timing of snowmelt or seasonality. These results provide further understanding about how changes to the timing of snowmelt may in turn transform these rare and unique plant communities.

Alpine snowbed communities are characterized as having areas of longer lasting snow cover duration compared with the surrounding landscape. The predictable accumulation of deep and long‐lasting snow on lee side ridges drives a unique ecology, providing stable microclimatic conditions under the snow through winter, supplying meltwater in spring, and controlling many biological processes. The timing and rate of plant litter decomposition are key controls on the nutrient balance of snowbed communities, and are thought to be strongly driven by snow dynamics. However, little is known about how the patterns and timing of snowmelt affect decomposition, nor how long these effects last into the growing season. We investigated the influence of snowmelt timing on decomposition rates across an alpine snowbed community by burying standardized plant litter (rooibos and green tea), at three incubation times (whole year, winter+spring, and summer), across three snowmelt zones. Decomposition rate (as percent mass loss of tea) was significantly higher in early‐melting zones compared to late‐melting zones, particularly for the recalcitrant litter (rooibos tea). Decomposition was also affected by the season(s) of incubation and was greatest where tea was buried for the whole year, or only over summer, with winter + spring only incubations decomposing the least. However, decomposition was more strongly influenced by litter quality (type of tea) than either the timing of snowmelt or seasonality. These results provide further understanding about how changes to the timing of snowmelt may in turn transform these rare and unique plant communities. [ABSTRACT FROM AUTHOR]

Background: Nutrient cycling in tropical forests has a large importance for primary productivity, and decomposition of litterfall is a major process influencing nutrient balance in forest soils. Although large-scale factors strongly influence decomposition patterns, small-scale factors can have major influences, especially in old-growth forests that have high structural complexity and strong plant-soil correlations. Here we evaluated the effects of forest structure and soil properties on decomposition rates and stabilization of soil organic matter using the Tea Bag Index (TBI) in an old-growth riparian forest in southeastern Brazil. These data sets were described separately using Principal Components Analysis (PCA). The main axes for each analysis, together with soil physical properties (clay content and soil moisture), were used to construct structural equations models that evaluated the different parameters of the TBI, decomposition rates and stabilization factor. The best model was selected using Akaike's criterion. Results: Forest structure and soil physical and chemical properties presented large variation among plots within the studied forest. Clay content was strongly correlated with soil moisture and the first PCA axis of soil chemical properties, and model selection indicated that clay content was a better predictor than this axis. Decomposition rates presented a large variation among tea bags (0.009 and 0.098 g·g− 1·d− 1) and were positively related with forest structure, as characterized by higher basal area, tree density and larger trees. The stabilization factor varied between 0.211–0.426 and was related to forest stratification and soil clay content. Conclusions: The old-growth forest studied presented high heterogeneity in both forest structure and soil properties at small spatial scales, that influenced decomposition processes and probably contributed to small-scale variation in nutrient cycling. Decomposition rates were only influenced by forest structure, whereas the stabilization factor was influenced by both forest structure and soil properties. Heterogeneity in ecological processes can contribute to the resilience of old-growth forests, highlighting the importance of restoration strategies that consider the spatial variation of ecosystem processes. [ABSTRACT FROM AUTHOR]

Questions: Woody encroachment is increasingly affecting biodiversity and ecosystem functioning of savannah ecosystems worldwide, yet the direction and magnitude of these impacts often seem context‐dependent. Here, we investigated the potential of a trait‐based framework to understand the effect of the encroaching shrub Dichrostachys cinerea on plant species diversity and litter decomposition in a savannah system. Location: Savannah plains of Nech Sar National Park, South‐Ethiopian rift valley. Methods: We conducted a three‐month litter burial experiment using two standard 'tea bag index' litter types and three local litter types across 45 vegetation plots, equally spread across unencroached, sparsely encroached and densely encroached savannah locations. We additionally quantified the specific leaf area, leaf dry matter content, leaf nitrogen content and leaf area of both D. cinerea and all common savannah species in each plot, and surveyed soil characteristics and species diversity and composition at the plot level. Using this set‐up we explored the potential of the four recorded plant traits to predict changes in litter decomposition following D. cinerea encroachment, in addition to changes in soil characteristics and savannah species diversity and composition. Results: Dichrostachys cinerea encroachment introduced novel functional trait values that reoriented community level resource use towards a more acquisitive strategy. These trait changes were partly associated with a reduction of decomposition rates within encroached areas compared to unencroached areas. Unexpectedly, encroachment resulted in increased, rather than decreased, herbaceous species diversity in sparsely invaded plots, but not in densely invaded plots. Species composition nonetheless shifted strongly following encroachment, indicating a strong species turnover, likely towards more shade‐tolerant species. Conclusions: Functional traits can partly help explain effects of encroachment on litter decomposition, but other environmental and biotic drivers nonetheless seem to additionally impact decomposition rates. [ABSTRACT FROM AUTHOR]

Seagrass ecosystems are globally-significant 'blue carbon' sinks; however, there is concern that this capacity will decline if rising ocean temperatures accelerate microbial decomposition. Decomposition of plant litter is a key process in the global carbon cycle—it influences how much carbon is available for sequestration. Therefore, understanding the biogeochemistry underlying decomposition is essential to predicting the capacity of seagrass ecosystems to act as carbon sinks in the future. Here, we tracked the breakdown of standardised and natural litter of varying chemical recalcitrance (rooibos tea > seagrass leaves > green tea) combined with highly-sensitive microsensor technology to test (a) how elevated water temperatures affect short-term microbial turnover, and (b) provide novel information on how the decay dynamics of the tea litter compare to those of natural litter. We found that increased temperatures (+ 5–10 °C) boosted microbial activity for all substrates, exhibited as enhanced decay, oxygen consumption and sulphate reduction. Within the 1-month experiment, the green tea litter had a rapid Q10 response to the temperature increase, quickly exhausting the resources for microbes, while the response of the rooibos tea and seagrass litters became more apparent toward the end of the experiment. Our results suggest that the tea litters capture a range of decomposition traits and can be compared with natural litter using traditional exponential decay models. The enhanced temperature-driven organic matter turnover, even under anoxic conditions, highlights the vulnerability of fresh litter to microbial attack during the early stages of decay and the potential weakening of blue carbon accumulation rates under future climatic conditions. [ABSTRACT FROM AUTHOR]

Plant litter decomposition is a key ecological process that is mostly studied at the forest floor. However, decomposition generally starts in the canopy. In this study, we evaluated the effect of litter composition and climate on the initial phase of decomposition in the soil and two contrasting types of canopy microsites along an elevational gradient (0–2200 m a.s.l.). To this end, we incubated standard material composed by green (fast decomposing) and rooibos (slow decomposing) tea bags for three months. Tea bags were placed in soil (buried at 5 cm) and in the canopy at ca. 5 m above the ground in "micro-wetlands" (tank bromeliads) and dry crown microsites (branches). Along the elevational gradient, green tea decomposed faster than rooibos tea in all microsites and forests. Mass loss for both tea types was lowest on branches at all sites, except for green tea in a wet forest where decomposition did not significantly differ among microsites. In wet forests, decomposition did not differ between bromeliads and soil, while in a dry forest, decomposition was faster in bromeliads. We found that the effects of climatic variables [monthly average temperature (TEMP) and total precipitation (PREC) for the incubation months] on decomposition differed between microsites. Along the elevational gradient, the mass loss in soil was positively correlated with TEMP but not with PREC, whereas on branches, mass loss was negatively correlated with TEMP and positively correlated with PREC. Unlike on branches, mass loss in bromeliads slightly decreased with PREC and increased with TEMP. Our study shows that microsite conditions interact with climate (TEMP and PREC) leading to differences in the general decomposition patterns in the forest canopy. [ABSTRACT FROM AUTHOR]

Background and aims: Intensification of savannah land-use is predicted to negatively influence soil biodiversity and functioning such as litter decomposition by detritivores. Loss of macrodetritivores, particularly termites, may be problematic in drier savannahs due to the capacity of macrodetritivores to sustain litter decomposition. Here we investigate how human land-use and spatiotemporal rainfall influence the contribution of macrodetritivores to plant litter decomposition. Methods: We measured decomposition using globally standardized litter: labile green and recalcitrant rooibos tea litter. The contribution of macrodetritivores to litter decomposition was determined through exclusion using meshed litterbags. Litter decomposition was determined in agricultural land, pastureland and wildlife protected areas during both wet and dry seasons and in mesic and wet rainfall regions across the borders of the Serengeti National Park, Tanzania. Results: Macrodetritivores consumed recalcitrant rooibos and mainly avoided labile green tea litter. On average macrodetritivores enhanced recalcitrant litter decomposition by 22%, but litter mass loss varied across land-uses, typically being higher on agricultural and pastureland compared to wildlife protected areas, and was sustained during periods of water scarcity. However, we observed instances of higher decomposition of recalcitrant litter by macrodetritivores in wildlife protected areas. In contrast, litter decomposition by microbes and microdetritivores was more constrained by seasonal and regional water availability with a minor influence of land-use. Conclusion: We found that moderate human-modification of savannahs is compatible with macrodetritivore litter decomposition. As savannahs become more intensely used by humans, raising ecological awareness among agropastoralist is required to ensure continued contribution of macrodetritivores to litter decomposition. [ABSTRACT FROM AUTHOR]

Climatic factors have long been considered predominant in controlling decomposition rates at large spatial scales. However, recent research suggests that edaphic factors and plant functional traits may play a more important role than previously expected. In this study, we investigated how biotic and abiotic factors interacted with litter quality by analyzing decomposition rates for two forms of standardized litter substitutes: green tea (high-quality litter) and red tea (low-quality litter). We placed 1188 teabags at two different positions (forest floor and 8 cm deep) across 99 forest sites in France and measured 46 potential drivers at each site. We found that high-quality litter decomposition was strongly related to climatic factors, whereas low-quality litter decomposition was strongly related to edaphic factors and the identity of the dominant tree species in the stand. This indicates that the relative importance of climate, soil and plant functional traits in the litter decomposition process depends on litter quality, which was the predominant factor controlling decomposition rate in this experiment. We also found that burying litter increased decomposition rates, and that this effect was more important for green tea in drier environments. This suggests that changes in position (surface vs. buried) at the plot scale may be as important as the role of macroclimate on decomposition rates because of varying water availability along the soil profile. Acknowledging that the effect of climate on decomposition depends on litter quality and that the macroclimate is not necessarily the predominant factor at large spatial scales is the first step toward identifying the factors regulating decomposition rates from the local scale to the global scale. [ABSTRACT FROM AUTHOR]

This study evaluated key assumptions underlying the Tea Bag Index (TBI) as a soil health assessment tool through a time series conducted under field conditions. The TBI assesses soil health by measuring the decomposition rates of standardized green and red tea over a 90-day incubation period. Our research was conducted on a degraded 33.6-ha agricultural site in North Saanich, British Columbia, where we compared two plots: a reference site and a grazed site, each representing distinct land use conditions. The first assumption evaluated was that the TBI metrics of S (stabilization rate) and k (decomposition rate) follow exponential decay models. While S adhered to this assumption, k did not, suggesting additional as yet undetermined influences on decomposition rates. We introduced new biological metrics, B g and B r , which followed polynomial models of decay, and may reflect the decomposition of different materials over time by different soil organisms. The second assumption tested was that a 90-day incubation period adequately captures the timeframe required for labile litter consumption. Our findings indicated that decomposition variance plateaued after 105 days, and that an increase in incubation time by 35 days increased the precision of mathematical decomposition models by a mean value of 18.1 %. The final assumption tested was that litter decomposition rate varies with land use. Our findings affirm that land use does affect litter decomposition rate, although the specific sources of that variance remain unclear. TBI accuracy can be improved by extending the litter incubation time to at least 105 days. Incorporating biological metrics (B g and B r) increases the TBI's precision. Our results reaffirm the TBI's sensitivity to land use differences, highlighting its potential as a cost-effective tool for assessing soil health under varying conditions. • The Tea Bag Index (TBI) is a simple, cost-effective and standardized method to assess organic matter decomposition rates. • The precision of TBI metrics can be increased by 18.1 percent by incubating organic materials for 105 rather than 90 days. • TBI decomposition metrics follow both exponential and polynomial curves, depending on the material and the metric. [ABSTRACT FROM AUTHOR]

Plants are affected by soil environments to the same extent that they affect soil functioning through interactions between environmental and genetic factors. Here, five plant species (broad bean, pea, cabbage, fennel, and olive) grown under controlled pot conditions were tested for their ability to differently stimulate the degradation of standard litter. Litter, soil C and N contents were measured for evaluating chemical changes due to plant presence, while soil microbial abundance was evaluated to assess if it had a positive or negative catalyzing influence on litter decomposition. The architecture and morphological traits of roots systems were also evaluated by using specific open-source software (SmartRoot). Soil chemical and microbiological characteristics were significantly influenced by the plant species. Variations in soil C/N dynamics were correlated with the diversity of root traits among species. Early stage decomposition of the standard litter changed on the basis of the plant species. The results indicated that key soil processes are governed by interactions between plant roots, soil C and N, and the microbial metabolism that stimulate decomposition reactions. This, in turn, can have marked effects on soil chemical and microbiological fertility, both fundamental for sustaining crops, and can promote the development of new approaches for optimizing soil C and N cycling, managing nutrient transport, and sustaining and improving net primary production.

Decomposition of plant litter is an important process in the terrestrial carbon cycle and makes up approximately 70% of the global carbon flux from soils to the atmosphere. Climate change is expected to have significant direct and indirect effects on the litter decomposition processes at various timescales. Using the TeaBag Index, we investigated the impact on decomposition of short-term direct effects of temperature and precipitation by comparing temporal variability over years, versus long-term climate impacts that incorporate indirect effects mediated through environmental changes by comparing sites along climatic gradients. We measured the initial decomposition rate (k) and the stabilization factor (S; amount of labile litter stabilizing) across a climate grid combining three levels of summer temperature (6.5-10.5°C) with four levels of annual precipitation (600-2700 mm) in three summers with varying temperature and precipitation. Several (a)biotic factors were measured to characterize environmental differences between sites. Increased temperatures enhanced k, whereas increased precipitation decreased k across years and climatic regimes. In contrast, S showed diverse responses to annual changes in temperature and precipitation between climate regimes. Stabilization of labile litter fractions increased with temperature only in boreal and sub-alpine sites, while it decreased with increasing precipitation only in sub-alpine and alpine sites. Environmental factors such as soil pH, soil C/N, litter C/N, and plant diversity that are associated with long-term climate variation modulate the response of k and S. This highlights the importance of long-term climate in shaping the environmental conditions that influences the response of decomposition processes to climate change. [ABSTRACT FROM AUTHOR]

Large herbivores are capable of modifying entire ecosystems with a combination of direct (for example browsing/grazing, trampling, defecation) and indirect (for example affecting plant species composition that then alters soil properties) effects. With many ungulate populations increasing across the northern hemisphere it is important to develop a general theory for how these animals can be expected to impact their habitats. Here we present the results of an 8-year experimental exclusion of moose (Alces alces) from 15 recent boreal forest clear-cut sites in Central Norway. We used standard univariate techniques to describe the treatment effect on multiple forest and soil properties and combined this with a multivariate Bayesian network structure learning approach to objectively assess the potential mechanistic pathways for indirect effects on soils and soil fertility. We found that excluding moose had predictable direct effects, such as increasing the ratio of deciduous to coniferous tree biomass and the canopy cover and decreasing soil bulk density and temperature. However, we found no treatment effects on any measures of soil processes or quality (decomposition, nitrogen availability, C/N ratio, pH, nutrient stocks), and furthermore, we found only limited evidence that the direct effects had cascading (indirect) effects on soils. These findings oppose the commonly held belief that moose exclusion will increase soil fertility, but still highlights the strong ability of moose to directly modify forested ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Decomposition is one of the most important processes in ecosystem carbon (C) and nutrient cycles and is a major factor controlling ecosystem functions. The functioning of Afromontane ecosystems and their ability to provide ecosystem services are particularly threatened by climate and land‐use change. Our objectives were to assess the effects of climatic conditions (elevation and seasonality) and land‐use intensity on litter decomposition and C stabilization in 10 ecosystems along the unique 3,000‐m elevation gradient of Mt. Kilimanjaro. Tea Bag Index parameters (decomposition‐rate‐constant k and stabilization‐factor S) were used to quantify decomposition of standardized litter substrate. Nine pairs of tea bags (green and rooibos tea) were exposed in each ecosystem during the short‐wet, warm‐dry, long‐wet and cold‐dry season. Decomposition rate increased from k = 0.007 in savanna (SAV; 950‐m elevation), up to a maximum of k = 0.022 in montane cloud forest (2,100 m). This was followed by a 50% decrease in (sub‐)alpine ecosystems (>4,000 m). SAV experienced the strongest seasonal variation, with 23‐times higher S values in dry season compared with wet season. The conversion of SAV to maize monocultures (~1,000 m) and traditional agroforestry to large‐scale coffee plantations (~1,300 m) increased mean k values, and stabilization factors were about one‐third lower. Forests between 1,900 and 2,100 m represent the zone of sufficient moisture and optimal temperature conditions. Seasonal moisture (lower slope) and temperature limitation (alpine zone) decreases litter decomposition. Mt. Kilimanjaro ecosystems are highly sensitive to land‐use change, which accelerates ecosystem cycles and decreases C stabilization. [ABSTRACT FROM AUTHOR]

Mountainous areas exhibit highly variable decomposition rates as a result of strong local differences in climate and vegetation type. This paper describes the effect of these factors on two major determinants of the local carbon cycle: litter decomposition and carbon stabilization. In order to adequately reflect local heterogeneity, we have sampled 12 typical plant communities of the Russian Caucasus. In order to minimize confounding effects and encourage comparative studies, we have adapted the widely used tea bag index (TBI) that is typically used in areas with low decomposition. By incubating standardized tea litter for a year, we investigated whether (1) initial litter decomposition rate (k) is negatively correlated with litter stabilization (S) and (2) whether k or S exhibit correlations with altitude and other environmental conditions. Our results show that S and k are not correlated. Altitude, pH, and water content significantly influenced the stabilization factor S, while soil-freezing had no influence. In contrast, none of these factors predicted the decomposition rate k. Based on our data, we argue that collection of decomposition rates alone, as is now common practice, is not sufficient to understand carbon input to soils and can potentially lead to misleading results. Our data on community-specific decomposition and stabilization rates further constrain estimates of litter accumulation in subalpine communities and the potential effects of climate change. [ABSTRACT FROM AUTHOR]

The above-ground net primary production (ANPP) and the precipitation-use efficiency (PUE) regulate the carbon and water cycles in grassland ecosystems, but the relationships among the ANPP, PUE and precipitation are still controversial. We selected 717 grassland sites with ANPP and mean annual precipitation (MAP) data from 40 publications to characterize the relationships ANPP-MAP and PUE-MAP across different grassland types. The MAP and ANPP showed large variations across all grassland types, ranging from 69 to 2335 mm and 4.3 to 1706 g m−2, respectively. The global maximum PUE ranged from 0.19 to 1.49 g m−2 mm−1 with a unimodal pattern. Analysis using the sigmoid function explained the ANPP-MAP relationship best at the global scale. The gradient of the ANPP-MAP graph was small for arid and semi-arid sites (MAP <400 mm). This study improves our understanding of the relationship between ANPP and MAP across dry grassland ecosystems. It provides new perspectives on the prediction and modeling of variations in the ANPP for different grassland types along precipitation gradients. [ABSTRACT FROM AUTHOR]

• Tea bag method can track the contrasting carbon accumulation processes in wetlands. • Lowering the water table increases soil nitrogen, phosphorus, and potassium. • High water table and air temperature speed up carbonate accumulation. • Low water table and high soil phosphorus accelerates rooibos decomposition. Calcareous spring fens accumulate carbon-rich deposits through carbonate precipitation and slow organic-matter decomposition, which can be affected by a lowering water table. Ongoing climate change is altering the carbon balance and threatening the biota of these vulnerable ecosystems. Rising air temperatures intensify carbonate precipitation and may accelerate decomposition, which is also influenced by soil nutrients and soil temperature. These relationships complicate predictions of carbon storage in calcareous fens. Here, we measured summer mass loss and carbonate accumulation at 57 spots in 19 calcareous spring fens in the Western Carpathians using commercial green tea and rooibos, i.e., the tea bag method. Decomposition rates were determined by mass losses corrected for leaching. Structural equation modelling was used to test the causal relationships between air and soil temperature, water table, soil nutrient concentrations, and mass loss or carbonate accumulation. The results demonstrate that a lowering water table increases soil nitrogen, phosphorus, and potassium concentrations. Water table and air temperature positively affected carbonate accumulation for both types of tea bags. Rooibos decomposition rate decreased with increasing water table and decreasing soil phosphorus concentration. Overall, the role of hydrology appeared crucial for global change predictions. If increased precipitation or groundwater recharge keeps the water table high, as predicted for some areas, the rising temperature will intensify carbonate precipitation and shift the ecosystem from peat to tufa-forming. While this scenario is more conducive to maintaining biodiversity and sustainability of existing carbon sinks than an alternative scenario predicting decreasing discharge due to decreasing precipitation and increasing evapotranspiration, it depends on preserving and maintaining fens and natural landscape hydrology. This study demonstrates the utility of the tea bag method to test drivers of contrasting carbon accumulation processes in groundwater-dependent wetlands. [ABSTRACT FROM AUTHOR]

To test the effects of invasion by strawberry guava trees ( Psidium cattleianum) on the forest soil ecosystem, we compared soil properties between pairs of adjacent native and P. cattleianum stands. We set up six study sites that had developed under different mean annual precipitation levels in the Ko'olau Mountains on the island of O'ahu, Hawai'i. Accumulated litter mass and soil pH decreased with precipitation in the native stands. Invasion by P. cattleianum increased the amount of litter and reduced the differences in soil water content and pH among the sites. We compared the decomposition process using the Tea Bag Index, which is determined by the difference in dry mass of commercially available green and rooibos teas in nylon mesh bags before and after 90 days of burial. Psidium cattleianum increased the initial litter decomposition rate irrespective of precipitation and other soil properties. On the other hand, P. cattleianum increased the long-term litter stabilization factor of the Tea Bag Index in wetter sites. The accumulation of litter was likely caused by indirect effects of P. cattleianum through the alteration of soil moisture properties. In summary, this study shows that invasion by P. cattleianum could alter the soil properties in both wet and mesic sites, suggesting the possibility of change in composition and/or function of decomposers. [ABSTRACT FROM AUTHOR]