Litter Dynamics Research Articles

Increased personal protective equipment litter as a result of COVID-19 measures

Use of personal protective equipment (PPE) increased during the COVID-19 pandemic to reduce virus transmission. Here, we quantitatively analyse emergence of PPE and COVID-19-related litter over 14 months for 11 countries using the litter collection application Litterati. The proportion of masks in litter increased by >80-fold as a result of COVID-19 legislation, from <0.01% to >0.8%. Gloves and wipes, more prevalent at ~0.2% of litter before the pandemic, doubled to 0.4%, but this has since fallen. Glove litter increased in the initial stages of the pandemic but fell after the introduction of facemask policies, whereupon there was an increase of facemask litter. National COVID-19 policy responses and international World Health Organization announcements and recommendations are a probable driver of PPE litter dynamics, especially the implementation of facemask policies. Waste management should be incorporated in designing future pandemic policies to avoid negative environmental legacies of mismanaged PPE. The COVID-19 pandemic substantially altered consumption patterns, especially for health supplies such as personal protective equipment, including masks and gloves. This study of 11 countries examines both the rate and types of litter being discarded as a result of changing policies and recommendations during the first 14 months of the pandemic.

Litter behaviour on Mediterranean cobble beaches, SE Spain

Despite the large research effort on reporting quantities of coastal litter, the dynamics of this litter is not yet sufficiently understood. Litter inputs in five cobble beaches located in the Mediterranean (Spain) were studied over three months during winter by biweekly litter tagging. Plastic represented the dominant material that reached the beaches (77%). In remote and narrow beaches, storms constituted the main driver in litter dynamics, favouring the accumulation of floating items such as plastic bottles and wood fragments as well as the largest but contrasting effects, increasing litter inputs and outputs from the beach, respectively. In rural beaches, beach users, mainly fisher people, but also tourists, contributed to a notable input of litter to the beach. Burial and exhumation of litter were reported as common occurring processes. Better management actions are required to improve beach environmental quality.

Mountain streams flushing litter to the sea – Andean rivers as conduits for plastic pollution

Rivers polluted by anthropogenic litter are major transport routes of litter from inland to the coastal zone and the ocean. However, litter studies have primarily focused on marine environments, and the litter dynamics in rivers are still poorly understood. Herein, we explored the abundances, composition and sources of litter at the riversides and in surface waters of mountain rivers from continental Chile in two different years. Additionally, we evaluated whether different temporal, geographic, topographic, hydrologic or anthropogenic factors influence the abundances of litter. Anthropogenic litter was prevalent in Chilean rivers, both at the riversides and in surface waters. Average abundances of riverside litter, floating macrolitter, and small floating plastics were 1.8 items m−2, 10.1 items h−1 and 5.8 items h−1, respectively, and abundances were generally higher in northern Chile. Plastics dominated in all compartments, comprising 29% of riverside litter and more than 70% of small floating litter, but other litter categories were also present at riversides. Sources of litter in Chilean rivers were mostly local, such as recreational visitors, residents, and illegal dumping, and there were no clear effects of the different tested factors on the abundances of litter. Litter densities in surface waters were low compared to those in lowland slow-flowing rivers in other countries, suggesting that retention of litter is limited in the highly dynamic and rapidly flushing mountain rivers, and thus most litter (primarily plastics) is transported directly to the sea. The results suggest that to adequately address this problem in Chile, prevention measures should be aimed at the identified local sources, by means of education, public policies, legislation, and enforcement.

Litter production and litter dynamics in different agroforestry systems in the arid western region of India

ABSTRACT Litterfall production, decomposition and nutrient release was investigated for three prominent agroforestry tree species, Prosopis cineraria, Tecomella undulata and Hardwickia binata, grown in the arid western region of India. The highest litterfall was recorded for H. binata (9.44 Mg ha−l y−1) followed by P. cineraria (8.94 Mg ha−l y−1) and T. undulata (3.74 Mg ha−l y−1). It took 15, 12 and 9 months for decomposition of 90% of the litter of H. binata, P. cineraria and T. undulata, respectively. Regression analysis showed that rainfall and air temperature had significant impacts on the decomposition process. Soil moisture and soil microbial biomass carbon showed high correlations (R2 > 0.70, p < 0.01) with litter decay. The rate of release of N (k N = 0.0014, surface (0–15 cm); k N = 0.0015, sub-surface (15–30 cm)) and K (k K = 0.0041, surface; k K = 0.0047, sub-surface) was highest from P. cineraria, whereas release rates of P were statistically equivalent for all species. N release from the decomposing litter increased initially, but then decreased as decomposition progressed. Concentrations of P, K and Mg in the litter decreased throughout the decomposition, with some fluctuations in P and Mg for P. cineraria and H. binata at the later stage. Ca release did not follow any specific trend. P. cineraria, with considerable amounts of litterfall, the highest nutrient inputs to the soil and the most rapid release of nutrients during the decomposition, was concluded to facilitate greater fertility build-up of the soil compared with the other two species.

Linking soil biodiversity and ecosystem function in a Neotropical savanna

Conserving the remaining savanna ecosystems in the Brazilian savanna (Cerrado) — a global biodiversity hotspot that stores carbon and provides water to a large portion of South America — requires understanding the ecological processes maintaining their function. Nutrient cycling supports savanna function via plant litter production and decomposition by soil fauna, releasing nutrients for plant and soil organism uptake. Soil biodiversity and biogeochemistry linkages with litter dynamics in Neotropical savannas under a changing climate are poorly understood. Here, we combined two years of rainfall seasonality, leaf and wood litter production and decomposition with soil epigeic fauna abundance — the number of ground-surface dwelling invertebrates collected through pitfall traps — taxa richness, Shannon's diversity and Pielou's evenness, and 16 soil biogeochemical variables measured in 12 plots of preserved savanna. Rainfall seasonality modulated the mean soil epigeic fauna diversity and evenness across all plots, which were highest in the rainy season, in contrast to litterfall rates, which peaked in the dry season. In the dry season (April to September), the Formicidae family was the most abundant with 50% of all individuals, while in the rainy season (October to March), the Isoptera order was the most abundant with approximately 39% of individuals. Wood litter decomposition grouped with annual Hemiptera abundance, co-varying with soil epigeic fauna diversity and evenness per plot and against soil fertility variables. Leaf litter decomposition co-varied with the total epigeic fauna abundance and soil pH. We speculate that the specific need to decompose wood litter may be associated with a greater need for diversity than an abundance of soil epigeic fauna. Our work highlights the role of rainfall seasonality on soil biodiversity and physicochemistry, which is also tightly linked with litter production and decomposition. This study advances our understanding of the mechanisms governing nutrient cycling in savanna ecosystems on nutrient-impoverished soils, with implications for achieving sustainable conservation and restoration goals.

Soil fauna modulates the effect of experimental drought on litter decomposition in forests invaded by an exotic pathogen

AbstractLitter decomposition is a fundamental process for nutrient cycling and C fluxes between terrestrial ecosystems and the atmosphere. Multiple factors such as environmental conditions, litter quality and decomposer organisms are known to influence this ecological process in direct and indirect ways. However, it remains poorly understood to what extent this entangled bank of complex interactions can be disrupted by several global change drivers such as climate change and invasive species.Here we reported main findings from a litter decomposition experiment conducted in a natural mixed forest invaded byPhytophthora cinnamomi,an exotic oomycete well known for causing tree disease and forest decline. In two Mediterranean forest types (namely woodland and closed forest), we first built a rainfall exclusion infrastructure to reduce natural precipitation by 30%. Then, we followed the spatial variation in C and N leaf litter dynamics as well as the abundance of the exotic oomyceteP.cinnamomifor 18 months under both control and rainfall exclusion conditions using a litter bag methodology with different mesh sizes to further evaluate the indirect role of mesofauna abundance and diversity in litter C and N temporal dynamics.Significant reductions in soil moisture produced by the experimental rainfall exclusion increased C litter loss with time directly, and indirectly via increases in overall mesofauna abundance and changes in the ratio between predators and decomposers. N litter dynamics were in contrast modulated mainly by initial litter quality. Surprisingly,P. cinnamomiabundance did not correlate with variation in initial litter quality as previously suggested, but we found that the exotic oomycete was negatively correlated with both decomposer and predator abundances. These results suggest it might participate indirectly in litter decomposition dynamics through the biotic soil component.Synthesis. Contrary to expected, our results show that a moderate but realistic rainfall reduction can accelerate the litter decomposition process. It also points out to litter fauna as a key component modulating the indirect impacts of global change drivers on litter decomposition.

The role of plants in the face of marine litter invasion: A case study in an Italian protected area

Marine litter accumulates in coastal dunes and causes severe damages to these fragile ecosystems. This study analyzed the composition, cover and distribution of marine litter and its relation to vegetation cover in a Mediterranean dune system, located in a protected area facing the Ligurian Sea (Northern Italy). We sampled twenty-two permanent multiscale plots in spring and autumn. Litter was detected in all plots and artificial polymer materials were the dominant type (85%). Litter categories increased from spring to autumn mainly due to seaside tourism. The largest spatial scale (16 m2) explained the variability in waste composition better than the smaller ones (4 m2, 1 m2). Finally, the vegetation cover correlated inversely with the turnover of litter categories, suggesting that plants may act as a barrier to litter transport by trapping it, and that they play a role in the spatio-temporal dynamics of coastal litter.

The influence of roots on mycorrhizal fungi, saprotrophic microbes and carbon dynamics in a low‐phosphorus Eucalyptus forest under elevated CO2

Abstract Elevated atmospheric carbon dioxide (eCO2) can impact soil organic matter (SOM) dynamics by changing the rates of carbon (C) losses and gains. In the rhizosphere, these changes are usually assumed to be the result of root‐mediated eCO2 impacts on saprotrophic microbes via altered below‐ground C allocation. This C allocation can also impact mycorrhizal fungi and their role in SOM dynamics. However, direct field quantifications of the influence of roots on both mycorrhizal fungi and saprotrophs together with SOM dynamics in forests exposed to eCO2 are rare. This is especially true in phosphorus (P)‐limited systems, even though ecosystem responses to eCO2 are known to depend on P availability. We assessed root mediation of eCO2 impacts on saprotrophs, mycorrhizal fungi, and C dynamics of root litter and mineral soil C (SOM‐C) in a mature, P‐limited Eucalyptus woodland exposed to eCO2. We used a novel nested‐mesh‐bag method to manipulate roots access to the substrates in a 1‐year field incubation. We used an isotopic approach to trace C dynamics and performed a comprehensive microbial community analysis, along with nutrients and enzymatic activity measurements. Roots increased microbial biomass, fungal:bacterial ratio, plant‐derived C gains and substrate C losses while decreasing P availability and specific enzymatic activity. eCO2 increased bacterial relative abundance in root litter and protozoa in SOM‐C, but it did not enhance root impacts or mycorrhizal fungi biomass. Our combination of in‐situ approaches allowed us to demonstrate that while roots have multiple impacts on soil microbial communities and C dynamics, they are not the main drivers of responses to eCO2 in this P‐limited forest. Other factors beyond enhanced root‐derived below‐ground C inputs such as seasonality of nutrient and water availability, and shifts in plant communities may be more important in modulating eCO2 impacts on soil dynamics in P‐limited systems. ​A free Plain Language Summary can be found within the Supporting Information of this article.

Functional traits, growth patterns, and litter dynamics of invasive alien and co-occurring native shrub species of chir pine forest in the central Himalaya, India

Across the continents, plant invasion is identified as one of the main threats to ecosystem functioning and stability. The main objective of this research was to evaluate the differences in the functional traits between invasive alien (Ageratina adenophora (Spreng.) and Lantana camara L.) and native (Berberis asiatica Roxb. Ex DC., Pyracantha crenulata (D. Don.) M. Roemer and Rubus ellipticus Sm.) shrub species of chir pine (Pinus roxburghii Sarg.) forest in the central Himalaya. Three 0.5 hectare chir pine forest stands were selected and individuals of similar diameter were tagged for comparative studies of leaf traits, growth pattern, and biomass accumulation in structural organs of each invasive alien and native species. Our one-way ANOVA and Tukey’s post hoc test results showed that both the invasive alien species have significantly (p < 0.05) higher SLA, LWC, total chlorophyll content, foliar nutrient (N and P), RGR, LMR, SMR, nutrient uptake, and nutrient use efficiencies than native species. Leaf litter decomposition rate and nutrient release were also significantly (p < 0.05) higher in both the invasive alien species. Native species, R. ellipticus, shared some of the traits, such as leaf area, chlorophyll content, RGR, LAR, LMR, and nutrient uptake efficiency with invasive alien species. The majority of traits differed among invasive alien and native species, implying that the success of invasive alien species is best described by being functionally distinct from native species. These findings indicate that invasive alien species had advanced functional traits which may be playing an important role in a rapid spread in the central Himalaya.

Leaf litter dynamics in Western Black Sea mountainous forest ecosystems

This study aimed to estimate leaf litter decomposition rates in eastern beech (Fagus orientalis Lipsky) and sweet chestnut (Castanea sativa Mill.) mixed stands in Akçakoca in the province of Düzce, located in the Western Black Sea region of Turkey. The sampling areas represent four different elevations and two aspects at each elevation. Amounts of annual beech and chestnut litterfall were estimated at 5.19 and 4.61 Mg·ha−1, respectively. Litter decomposition was examined over five time periods (0.25, 0.50, 1.25, 2.25, and 4.25 years) by using the litterbag method. The mass of remaining beech leaf litter was found to be 1.1, 1.2, 1.2, 1.4, and 1.3 times greater than the mass of chestnut leaf litter, respectively. However, estimated values for the decomposition rate constant (k) of chestnut for all time periods were found to be approximately 1.5 times greater than those of beech leaf litter. Litter in beech stands decomposed more rapidly at higher elevations during the first year but at lower elevations during the second year, likely due to increased temperature and precipitation for the corresponding years. Leaf litter in chestnut stands decomposed more rapidly at lower elevations in the second and fourth years, reflecting higher precipitation for those years.

Understory removal accelerates nucleic phosphorus release but retards residual phosphorus release in decomposing litter of Phyllostachys edulis in subtropical China

AbstractDespite the importance of understory vegetation for ecosystem processes and functions, its contribution to the dynamics of phosphorus (P) fractions in decomposing litter has rarely been studied in subtropical plantations. Herein, by conducting an understory removal (UR) experiment in a moso bamboo (Phyllostachys edulis) plantation of South China, we assessed the effect of understory species on leaf litter mass loss and P fractions (inorganic P, sugar P, nucleic P, and residual P) of moso bamboo over a 12‐month incubation period. We also examined the effect of UR on soil physicochemical properties, as well as fungal and bacterial phospholipid fatty acids (PLFAs). Our results showed that UR reduced litter decomposition rate (6.0–12.4%), but exhibited no effect on total P remaining in decomposing litter. Furthermore, UR produced variable effects on the amounts of P fractions in decomposing litter. Despite no changes were observed in the amount of inorganic and sugar P fractions, UR accelerated nucleic P release (3.0–6.6%), and residual P immobilization (9.2–27.9%) in decomposing litter. Moreover, UR increased fungal PLFAs (8.0–44.9%) but decreased bacterial PLFAs (18.7–36.8%) in the soil, leading to an increase in fungal to bacterial PLFAs ratio (34.5–80.9%). The correlation analysis showed that accelerated litter nucleic P release after UR was mainly attributed to the increases in soil fungal PLFAs, while decelerated litter residual P release was mainly resulted from the increased soil fungal PLFAs and decreased soil bacterial PLFAs. These results indicate that understory vegetation can mediate the dynamics of litter P fractions via its effect on soil microbial composition in subtropical plantations and suggest that understory vegetation is crucial to maintain soil P availability in moso bamboo plantations.

Salamander loss alters litter decomposition dynamics.

Biodiversity loss affects ecosystem functioning. Top down effects of amphibian declines on the trophic food web of the forest floor are poorly understood. Here we quantify and explain the effects of disease-driven loss of salamanders on the dynamics of forest leaf litter. Using paired mesocosms, within a Belgian forest, we tested the effect of fire salamander (Salamandra salamandra) presence on the trophic cascade that results in the decomposition rate of good quality (maple - Acer pseudoplatanus) and poorer quality (oak - Quercus robur) leaf litter, over an 18month period. The presence of salamanders reduced decomposition rate of Quercus litter up to 20%. This was associated with a significantly higher predation rate on detritivores, which altered the functional composition of the invertebrate community. Functional composition analysis of the litter microbiome showed less bacteria associated with leaf litter degradation on the Quercus litter in the presence of salamanders. Salamanders thus influence ecosystem functions through trophic cascades and promote the retention of the leaf litter fraction in poorer quality litter.

Integrating Rangeland Health and Stream Stability in Assessments of Rangeland Watersheds

Watersheds are distinct hydrologic units that comprise a range of terrestrial upland and riparian complex ecological sites. Since the hydrologic function of the entirety of the watershed is linked, other ecological functions and processes are also likely linked. No single assessment tool is available to describe the ecological status of both terrestrial upland sites and riparian complexes in a single watershed. We investigated the relationship by integrating two assessment tools, Interpreting Indicators of Rangeland Health protocol (IIRH) and stream geomorphic surveys in prairie ecosystems. The qualitative values from the IIRH protocol were different among upland sites associated with 35 intermittent stream reaches in North Dakota in the United States. Riparian complex sites were separated using three metrics of stream stability: stream channel type, bank-height ratio, and Bank Erosion Hazard Index. Stream channel type had the strongest relationship with two attributes of rangeland health, Soil & Site Stability and Hydrologic Function, while bank-height ratio had the strongest relationship with the Biotic Integrity attribute. The influences of individual indicators were identified using a principal components analysis, which revealed unstable streams were typified by departures from the reference state in compaction, soil loss, bare ground, litter dynamics, infiltration, and invasive species. These findings suggest that changes in these IIRH indicators should be monitored and managed by land managers to ensure that riparian function and ecosystem services are not compromised. Future research must continue to investigate the link between upland and riparian functions within a watershed, with special emphasis on vegetation dynamics. In the meantime, integrating these two assessments can provide land managers with vital information about maintaining ecological function throughout the watershed.

中亚热带次生林和人工林凋落枝水溶性碳氮磷动态特征

凋落枝是森林地上部分凋落物的重要组分，揭示其水溶性碳氮磷的动态规律对于认识森林物质循环过程具有重要意义，但目前研究集中于凋落叶，而对凋落枝缺乏必要关注。因此，以中亚热带典型马尾松（Pinus massoniana）人工林、杉木（Cunninghamia lanceolata）人工林和米槠（Castanopsis carlesii）次生林为研究对象，在一个自然年内调查了凋落枝水溶性碳、氮、磷含量及其芳香化指数以及化学计量比的动态变化过程。结果显示：（1）米槠次生林凋落枝水溶性碳、氮、磷含量及芳香化指数明显大于马尾松和杉木人工林；（2）水溶性碳和磷、水溶性碳比磷、水溶性氮比磷和芳香化指数有明显的季节变化；（3）水溶性碳、水溶性磷、水溶性氮比磷和芳香化指数在不同林分和季节间有交互作用。（4）马尾松和杉木人工林、米槠次生林凋落枝水溶性物质含量的季节变化多数与气温和降水呈显著负相关。这些结果表明亚热带次生林可能相对于人工林具有更为高效的以凋落枝为载体的物质循环过程，在未来气候变暖背景下亚热带森林由凋落枝归还给土壤的养分浓度可能降低。;Twig litter is an important component of forest litter. It is of great significance to reveal the dynamics of water soluble carbon, nitrogen and phosphorus for understanding the forest material cycle. However, the previous researches paid more attention to leaf litter than twig litter. In this regard, we investigated water soluble carbon, nitrogen, phosphorus, and aromatization index as well as stoichiometric ratio dynamics of twig litter in a year round in Pinus massoniana plantation, Cunninghamia lanceolata plantation and Castanopsis carlesii secondary forest. Our results showed that:(1) water soluble carbon, nitrogen and phosphorus as well as aromatization index of twig litter in Castanopsis carlesii secondary forest were significantly higher than those of Pinus massoniana and Cunninghamia lanceolata plantations; (2) water soluble carbon and phosphorus, water soluble carbon- phosphorus ratio and nitrogen-phosphorus ratio, as well as aromatization index of twig litter varied significantly in different seasons; (3) there were significant interactions between forest types and sampling seasons in affecting water soluble carbon and nitrogen, water soluble nitrogen-phosphorus ratio, and aromatization index. (4) the seasonal variation of water soluble substance of twig litter in Pinus massoniana, Cunninghamia lanceolata plantation and Castanopsis carlesii secondary forest were negatively correlated with air temperature and precipitation. These results suggest that subtropical secondary forests may have a more efficient nutrients cycling process based on twig litter than plantations, and the concentrations of nutrients cycling back to soil via twig litter will decrease in subtropical forests under future warming scenarios.

Litter dynamics of mango trees grown in different shrink-swell soil series of Maharashtra

An experiment was conducted at central campus of Mahatma Phule Krishi Vidyapeeth, Rahuri to study the dynamics of monthly litter fall biomass and its chemical composition and nutrient return to soil were study under of mango trees under different soil series of Maharashtra. The result showed that higher quantity of liter biomass was produced in mango plantation under medium deep soil (Sawargaon soil series) over different soil series. Among mango plantation under different soil series, highest content of nutrients i.e. NPK and carbon was recorded in Sawargaon soil series as compare to other soil series. Maximum amount of nutrient return to soil through soil was recorded in mango plantation under medium deep soil over shallow and deep soil. On another hand carbon and nitrogen are most important of many element required for microbial decomposition of organic matter. The result revealed that numerically optimum C:N ratio (31.68) was recorded in litter leaf fall of mango plant under Sawargaon soil series as compare to other series.

The generation of marine litter in Mediterranean island beaches as an effect of tourism and its mitigation

The Mediterranean Sea and its coastal systems are threatened by intense anthropogenic pressures including rapid accumulation of marine litter by diverse human activities. The region, which is the world’s leading touristic destination, has to face a seasonal increase of waste generation due to the seasonal influx of visitors. The beaches, extremely crowded during the summer, are particularly vulnerable since they are proven to be concentrated accumulation zones and one of the main gateways of litter to enter the marine system. We found that the accumulation rates of marine litter on Mediterranean island beaches follow a seasonal pattern, increasing up to 4.7 times during the high season, representing a daily load of (40.6 ± 11.5) 106 items/day extrapolated to all the islands of the region. We developed an accumulation index to assess the dynamics of marine litter and support efficient mitigation strategies by local authorities. To limit marine litter production attributable to recreational activities, a series of pilot actions implemented during the high touristic season, demonstrated a substantial reduction (up to 52.5%). The implementation towards an efficient and sustainable tourism business model is urgently required.

Effects of elevated temperature on microbial breakdown of seagrass leaf and tea litter biomass

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.

Litter removal through fire – A key process for wetland vegetation and ecosystem dynamics

Fire is a major driver of global vegetation patterns. It strongly reduces litter and thus alters physical and chemical properties of the environment. Studies investigating the interplay of fire and litter are scarce, and wetland ecosystems are strongly under-represented in research focusing on litter dynamics. We present data on short-term effects of fires in floodplain wetlands along the Amur River in the Russian Far East, an area with a high fire recurrence rate. We analysed vegetation and plant growth patterns as well as soil temperature and nutrient concentrations on recently burnt and unburnt control plots.Directly after fire, litter was reduced by more than 50% on burnt plots. This effect was no longer visible 15 months after fire, probably due to the high productivity of the floodplain ecosystem. Litter was found to act as a key determinant in the net of direct and indirect fire effects, by influencing early plant growth patterns of herbs and grasses. Furthermore, litter removal through fire significantly increased plant species diversity and soil temperature. Contrary, N and P concentrations in living plant biomass of grasses and herbs decreased with decreasing litter cover. Combustion during burning seems to be responsible for the negative direct fire impacts on nutrient concentrations, which were found for N and Mg.Litter removal through fire can strongly affect diversity patterns, dominance structures, and nutrient cycling in wetlands. With increasing fire frequency in the course of global change, significant structural and compositional changes in herbaceous wetland vegetation must be anticipated and the studied ecosystem may shift to reinforced N-limitation.

Assessing the fine-scale effects of bamboo dominance on litter dynamics in an Amazonian forest

Bamboo dominance drives changes in vegetation structure and plant biodiversity in many tropical forests worldwide. However, the effects of bamboos on ecosystem functions have received less attention or have been investigated in degraded forests. Here, we assessed the effects of the dominance of the native bamboo Guadua weberbaueri on litterfall, litter layer and decay of leaf litter in an Amazonian forest free from major disturbances. We aimed to understand whether bamboo dominance changes the litter dynamics on a fine spatial scale. Specifically, we tested the hypothesis that bamboo-dominated (BD) forest areas have (i) less litterfall, (ii) greater litter layer thickness and (iii) less decay of leaf litter necromass compared to adjacent bamboo-free (BF) forest areas. Over a year, the BD forest area produced less litterfall and accumulated a thicker litter layer compared to the adjacent BF forest area; however, the decay of leaf litter necromass did not differ between the BD and BF environments. Our results suggest that the bamboo dominance in Neotropical forests decreases litterfall and increases the litter layer thickness, which should deplete the nutritional return in these systems over time. Furthermore, we show that these effects also occur in forests that are not subject to major disturbances and that they can be seen even at small spatial scales.

Molecular dynamics of foliar litter and dissolved organic matter during the decomposition process

Decomposing foliar litter organic matter (LOM) in forested watersheds is an essential terrestrial source of dissolved organic matter (DOM) to aquatic ecosystems. To evaluate the relationship of chemical composition between LOM and DOM, we collected freshly fallen leaves of white oak (Quercus alba) and conducted an 80-week field decomposition experiment along a small elevation gradient in a floodplain within the Congaree National Park, South Carolina. Foliar litters were collected for water extraction and instrumental analyses using pyrolysis GC/MS, UV/VIS and fluorescence spectrophotometry. Factor analyses of pyrolysates showed that fresh LOM was mainly composed of lignin compounds (LgC), phenolic compounds (PhC), and carbohydrate (Carb), and the change in composition was relatively small throughout the decomposition process. In contrast, there were two distinct chemical compositions of DOM in early (between 0–8 weeks) and late phases (between 16–80 weeks). The early phase had a higher percentage of PhC, but the late phase contained higher percentages of Carb, unsaturated hydrocarbon (UnSaH), aromatic hydrocarbon (ArH), and nitrogen-containing compounds (Ntg). The fluorescence emission-excitation matrix showed there was an increasing trend in humic and fulvic-like fractions in DOM over time, matching well with increases of UnSaH and ArH fractions from the results of pyrolysis GC/MS. Our study illustrated that the changes of chemical components in LOM and water extractable DOM were not parallel during the decomposition process and the degradation of lignin and phenolic compounds was one of the controlling factors on the production of DOM.