Flow Intermittency Affects Leaf Decomposition and Benthic Consumer Communities of Alpine Streams: A Case Study along the Po River

Streams and rivers are becoming increasingly intermittent in Alpine regions due to the global climate change and related increases of local water abstractions, making it fundamental to investigate the occurrence of supraseasonal drying events and their correlated effects. We aimed to investigate leaf litter decomposition, the C:N ratio of the litter, and changes in associated macroinvertebrate communities in three reaches of the Po River: One upstream, consistently perennial, a perennial mid-reach with high hydrological variability, and an intermittent downstream reach. We placed leaf litter bags of two leaf types—chestnut and oak; both showed comparable decomposition rates, but the remaining litter mass was different and was attributed to the C:N ratio and palatability. Furthermore, (1) in perennial reaches, leaf litter decomposed faster than in the intermittent ones; (2) in intermittent reaches, the C:N ratio showed a decreasing trend in both leaf types, indicating that drying affected the nitrogen consumption, therefore the conditioning phase; (3) associated macroinvertebrate communities were richer and more stable in perennial reaches, where a higher richness and abundance of EPT taxa and shredders was observed. Our results suggest that the variations in the hydrology of mountain streams caused by global climate change could significantly impact on functional processes and biodiversity of benthic communities.

Decomposition of rice straw residues and the emission of CO2, CH4 under paddy rice and crop rotation in the Vietnamese Mekong Delta region – A microcosm study

This study investigated the influence of soil undergoing different crop rotations on the CH₄, CO₂ emissions, and decomposition of rice straw. The studied soil undergoing crop rotation systems were rice-rice-rice (SR) and baby corn-rice-mungbean (SB). Two main microcosm set-ups: anaerobic (SR-AN, SB-AN) and aerobic (SR-AE, SB-AE) conditions. Litter bags containing rice stems were inserted into the soil and recollected at different time points for chemical analysing and the gas sampling was collected to measure the CO₂ and CH₄ emissions. The results indicated that the total carbon (TC) decreased around 30%, and the TC removal in anaerobic was significantly higher than in aerobic conditions. The residue cellulose content varied in a range from 68.2% to 78.6%, while the hemicellulose content varied from 57.4% to 69.3% at day 50 after incorporation. There were no significant differences in the total nitrogen removal, cellulose, hemicellulose, and lignin contents among the microcosm set-ups. CO₂ emission increased in all the microcosm set-ups with the treatments without rice straw (CTSR, CTSB) in both aerobic and anaerobic conditions. CH₄ release in the SR-AN treatments did not differ significantly compared with the SB-AN treatments. This study confirmed that the decomposition of rice straw residues is faster in the anaerobic paddy soil condition compared to the aerobic crop rotation condition.

Diversity of fungi in decomposition process the Avicennia marina leaf litter at various level of salinity

Factors affecting the rate of the decomposition are animals and microorganisms such as worms, snails, bacteria, fungi etc. as well as environmental conditions, such as type of soil, pH and salinity of water, etc. This research was conducted at the Deli Belawan River and Forest Cultivation Laboratory, Medan, North Sumatra Sumatera. A study was undertaken to find out the effect of the salinity on : the number of species, the population, the species diversity and the frequency of colonization of the different species of fungi during the process of the composition of the A. marina leaf litter decomposition. The leaf litter of A. marina to be put in a litter bag that is 50 g and it’s 33 litter bags for each level of salinity totally. The level of salinity to be used such as < 10, 10 – 20, 20 – 30 and > 30 ppt. The time series to collect data were 0 (control), 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, and 165 days. The leaf litter of A. marina in a litter bag was taken from each salinity level that was three bags for each time. It was used for isolation and identification of the fungi. There were 21 fungal species isolated from the A. marina leaf litter before being decomposed and from those decomposed at < 10, 10 – 20, 20 – 30 and > 30 ppt. The highest population was found in the leaf litter before being decomposed with an average of 1.6 × 103 cfu/ml. The Species Diversity Indices of the fungi isolated from the leaf litter at < 10, 10 – 20, 20 – 30, and > 30 ppt were 1.96, 1.86, 1.75 and 1,50. The frequency of the fungal colonization ranged from 9.1 to 100 %.

Degradation-driven changes in fine root carbon stocks, productivity, mortality, and decomposition rates in a palm swamp peat forest of the Peruvian Amazon

Background Amazon palm swamp peatlands are major carbon (C) sinks and reservoirs. In Peru, this ecosystem is widely threatened owing to the recurrent practice of cutting Mauritia flexuosa palms for fruit harvesting. Such degradation could significantly damage peat deposits by altering C fluxes through fine root productivity, mortality, and decomposition rates which contribute to and regulate peat accumulation. Along a same peat formation, we studied an undegraded site (Intact), a moderately degraded site (mDeg) and a heavily degraded site (hDeg) over 11 months. Fine root C stocks and fluxes were monthly sampled by sequential coring. Concomitantly, fine root decomposition was investigated using litter bags. In the experimental design, fine root stocks and dynamics were assessed separately according to vegetation type (M. flexuosa palm and other tree species) and M. flexuosa age class. Furthermore, results obtained from individual palms and trees were site-scaled by using forest composition and structure. Results At the scale of individuals, fine root C biomass in M. flexuosa adults was higher at the mDeg site than at the Intact and hDeg sites, while in trees it was lowest at the hDeg site. Site-scale fine root biomass (Mg C ha−1) was higher at the mDeg site (0.58 ± 0.05) than at the Intact (0.48 ± 0.05) and hDeg sites (0.32 ± 0.03). Site-scale annual fine root mortality rate was not significantly different between sites (3.4 ± 1.3, 2.0 ± 0.8, 1.5 ± 0.7 Mg C ha−1 yr−1 at the Intact, mDeg, and hDeg sites) while productivity (same unit) was lower at the hDeg site (1.5 ± 0.8) than at the Intact site (3.7 ± 1.2), the mDeg site being intermediate (2.3 ± 0.9). Decomposition was slow with 63.5−74.4% of mass remaining after 300 days and it was similar among sites and vegetation types. Conclusions The significant lower fine root C stock and annual productivity rate at the hDeg site than at the Intact site suggests a potential for strong degradation to disrupt peat accretion. These results stress the need for a sustainable management of these forests to maintain their C sink function.

Preliminary Study on Water Bodies’ Effects on the Decomposition Rate of Goldenrod Litter

Leaf-litter input constitutes a major load in natural waters; therefore, to achieve and maintain high water quality, it is important to thoroughly examine and understand the litter decomposition process. The widespread Solidago canadensis exerts a negative effect on the composition of the ecosystem, causes extinction of species, and modifies the function of the system. In Hungary, goldenrod constantly spreads to newer areas, which can also be observed around Lake Balaton and at the bank of the Hévíz canal. In our investigation, we examined the decomposition rate of the leaves and stems of the goldenrod with the commonly applied method of leaf litter bags. As water temperature, ranging from 24.0 °C to 13.7 °C, decreases in Hévíz canal away from Lake Hévíz (−0.32 °C/100 m), we chose three different sampling sites with different water temperatures along the canal to determine how water temperature influences the rate of decomposition. For both leaves and stems, the fastest decomposition rate was observed at the first site, closest to the lake. At further sites with lower water temperatures, leaf litter decomposition rates decreased. Results observed through Hévíz canal demonstrated that higher water temperature accelerated the goldenrod decomposition dynamics, while the drift also impacted its efficiency.

Potential use of Lupinus exaltatus Zucc. (Leguminosae) as green manure in soils of Jalisco, Mexico

The environmental impact generated by agriculture with excessive use of fertilizers has led to the search for alternatives to improve soil fertility. This study aimed to evaluate the potential of Lupinus exaltatus in terms of decomposition and mineralization of nitrogen (N) when incorporated into the soil as green manure (GM) and its effect on the growth of Triticum aestivum L. seedlings. Litter bags were used, with a total of 216 nylon bags (10 × 5 cm), in each bag were placed 5 g dry base of GM in the vegetative stage and flowering. Subsequently, the GM bags were placed separately Vertisol and Regosol soil at a depth of 5 cm; and every three weeks until the end of the incubation, three bags were recovered per treatment. For evaluation of the effect GM on T. aestivum growth experiment was established in pots with soil Regosol, it consisted of incorporating 50 and 34 g dry base of the GM (equivalent to 10 and 15 t.ha-1). The GM in the vegetative stage lost an average of 83,52 % of its initial weight, while in flowering the loss was 76,49 %, the mineralized N was higher in Regosol soil than in Vertisol with 74,02 % and 70,58 % respectively. The wheat seedlings presented 30 % more dry matter and N with GM than the control treatment. L. exaltatus had a rapid decomposition and mineralization of N in the first stages of incubation.

DECOMPOSITION OF LEAF LITTER IN THE BRAZILIAN CERRADO, CERRADÃO AND FOREST ENVIRONMENTS IN THE AMAZON, BRAZIL

The soils of the Amazon region, despite being under one of the densest forests in the world, are mostly characterized by low nutrient availability, with litter being the main nutrient input route. The present work aimed to evaluate the litter decomposition in forest, Cerrado and Cerradão environments in the Amazon. The litter decomposition rate was estimated by mass loss analysis using litter bags. The collections were performed at intervals of 30, 60, 90, 120, 150, 180, 210, 240, 270 and 300 days, with four replications. Once collected, the material contained in each litter bag was placed to dry to obtain the dry mass. And so, the remaining mass percentage, the decomposition rates (k) and the half-life time (t1/2) are estimated. During the studied period, the Cerrado environment presented the lowest constant k (0.0017 g g-1 day-1) and consequently longer half-life (407 days). The monthly deposition in Cerrado input ranged from Mgha-1mother1 (June to September). Among the evaluated environments, the forest presented the highest decomposition speed and Cerrado presented the lowest one. It was evidenced that the decomposition process for all studied environments occurred with greater intensity in the rainy season.

Decomposition of oat straw and release of macronutrients in different managements

The present work was aimed in order to evaluate the decomposition process of remaining straw from oat cultivars submitted to different handling during the cultivation of corn for silage intercropped with Urochloa brizantha cv. MG13 Braúna. We considered nine oat cultivars named as follows: "IAPAR 61 IBIPORÃ" oat hay (61F), "IAPAR 61 IBIPORÃ" pasture (61P), "IAPAR 61 IBIPORÃ" cover crop (61SM), "Embrapa 139 (Fog)" oat hay (139F),"Embrapa 139 (Fog)" pasture (139P)," Embrapa 139 (Fog)" cover crop (139SM), "Emerald IPR 126" oat hay (EF), "Emerald IPR 126" grazed (EP) and "Emerald IPR 126" cover crop (ESM) from which we evaluated the decomposition of the remaining straw using the method of litter bags. The evaluations were carried out at 0, 15, 30, 60, 90 and 108 days after sowing corn for silage intercropped with Brizantha brachiaria cv. MG13 Braúna (Urochloa brizantha). Every oat cultivar had three repetitions arranged in a split-plot design. We took into account the quantity of straw, organic matter, carbon, nitrogen, carbon / nitrogen ratio, phosphorus and potassium. The results we got clarify that oat decomposition rate varied with the meteorological factors and initial mass, so that the greater the initial mass is, the longer the straw permanency and mulch effectiveness on the soil. The time the residual oat straw took to be decomposed depended on meteorological factors both during the cover crop developmental stage and the decomposition period itself. The higher the initial mass, the greater the time and effectiveness of mulching.

SOIL FAUNA AND LEAF LITTER DECOMPOSITION IN DIFFERENT SUCCESSIONAL STAGES OF A SUBMOUNTAINOUS SEASONAL SEMIDECIDUOUS FOREST

In tropical forests, the stage of ecological succession influences the nutrient cycling. This study aimed to analyze soil fauna community structure, composition, and leaf litter decomposition in fragments of intermediate-successional and late-successional Submountainous Seasonal Semideciduous Forest (ISF and LSF, respectively). We used a square metal frame to collect 10 samples of the leaf litter layer and surface soil (0.00-0.05 m depth) from each area in the wet and dry seasons. Soil fauna individuals were then extracted using a modified Berlese-Tüllgren funnel. For analysis of leaf litter decomposition, 15 litter bags containing 30 g of senescent leaves were randomly placed on the forest floor of each area in the dry season, and three bags were collected after 60, 90, 120, 150, and 180 days. LSF presented higher value of richness and was more associated with Diptera and Formicidae. There was no clear pattern in evenness and diversity with successional stage. The dissimilarity between ISF and LSF in terms of soil fauna community was greater in the dry season. Litter decomposition was almost identical in both areas.

Species Diversity Induces Idiosyncratic Effects on Litter Decomposition in a Degraded Meadow Steppe

Litter decomposition is a fundamental path for nutrient cycling in a natural ecosystem. However, it remains unclear how species diversity, including richness and evenness, affects the decomposition dynamics in the context of grassland degradation. Using a litter bag technique, we investigated the litter-mixing effects of two coexisting dominant species (Leymus chinensis Lc and Phragmites australis Pa), as monocultures and mixtures with evenness (Lc:Pa) from M1 (30:70%), M2 (50:50%), and M3 (70:30%), on decomposition processes over time (60 and 365 days). The litter bags were placed on the soil surface along a degradation gradient [near pristine (NP), lightly degraded (LD), and highly degraded (HD)]. We found that 1) mass loss in mixture compositions was significantly and positively correlated with initial nitrogen (N) and cellulose contents; 2) litter mixing (richness and evenness) influenced decomposition dynamics individually and in interaction with the incubation days and the degradation gradients; 3) in a general linear model (GLM), nonadditive antagonistic effects were more prominent than additive or neutral effects in final litter and nutrients except for carbon (C); and 4) in nutrients (C, N, lignin) and C/N ratio, additive effects shifted to nonadditive with incubation time. We speculated that the occurrence of nonadditive positive or negative effects varied with litter and nutrients mass remaining in each degraded gradient under the mechanism of initial litter quality of monoculture species, soil properties of experimental sites, and incubation time. Our study has important implications for grassland improvement and protection by considering species biodiversity richness, as well as species evenness.