Amount Of Leaf Litter Research Articles

Are litterfall and litter decomposition processes indicators of forest regeneration in the neotropics? Insights from a case study in the Brazilian Amazon

Litterfall plays an important role in nutrient cycling and maintenance of soil fertility in terrestrial ecosystems. We gauged the effects of anthropogenic impacts on the production, decomposition and seasonality of litterfall in primary and secondary forests within a tropical landscape of the Brazilian Amazon. We hypothesized that leaf litter quantity and quality would differ in line with forest disturbance and that these changes would translate into dissimilar decomposition rates. If proved, these processes could be used as surrogates for indentifying the ecological status of forest habitats. The obtained results have shown that, in the study area litterfall is reduced and litter decomposition is braked in disturbed habitats when compared with primary and recovered secondary forests. Also, within similar climatic conditions, the litter production and decomposition rates begin to stabilize in mature secondary forests. Our results represent a useful contribution to understand the dynamics of the litterfall and litter decomposition processes in the neotropics. Both processes were correlated and sensitive to disturbance gradients and should used as forest recovery indicators in ecological monitoring and ecological restoration studies.

Litter conversion into detritivore faeces reshuffles the quality control over C and N dynamics during decomposition

Abstract In many terrestrial ecosystems, detritivorous soil organisms ingest large amounts of leaf litter returning most of it to the soil as faeces. Such conversion of leaf litter into faeces may stimulate decomposition by increasing the surface area available for microbial colonisation. Yet, experimental support for either the outcome or the mechanism of these conversion effects is lacking. Based on the hypothesis that the identity of plant species from which leaf litter is transformed into faeces has a critical role in how faeces decomposition proceeds, we collected faeces of the widely abundant millipede Glomeris marginata fed with leaf litter from seven distinct tree species. We compared the physical and chemical characteristics and the rates of carbon (C) and nitrogen (N) loss between litter and faeces. We found that after 100 days of exposure under controlled conditions, C loss was on average higher in faeces (40.0%) than that in litter (26.6%), with a significant increase for six of the seven species. Concurrently, N dynamics switched from a net immobilisation (7.7%) in litter to a net release (14.6%) in faeces, with a significant increase for five of the seven species. Litter conversion into faeces generally homogenised differences in physical and chemical characteristics among species. Despite such homogenisation, variability in rates of faeces C and N loss among species was similar compared to leaf litter, but correlated with a different set of traits. Specifically, faecal pellet C loss was positively related to compaction (decreased specific area and increased density of faecal pellets), and both C and N loss from faecal pellets were positively related to fragmentation (increased specific area and perimeter of particles within faecal pellets). We conclude that litter fragmentation and compaction into detritivore faecal pellets lead to substantially enhanced decomposition, with a particularly strong impact on N dynamics that changed from immobilisation to net release depending on litter species. Moreover, litter quality control on decomposition is reshuffled by litter conversion into faeces. In ecosystems with high detritivore abundance, this so far largely overlooked pathway of organic matter turnover may strongly affect ecosystem C and N cycling. A plain language summary is available for this article.

Rarity and nutrient acquisition relationships before and after prescribed burning in an Australian box-ironbark forest.

Nutrient cycling is greatly influenced by dominant plants that contribute high amounts of leaf litter to soils; however, less-dominant and rare species can play keystone roles in nutrient cycling if they have unique nutrient acquisition traits and provide high-quality litter. In many parts of the world, wildfire is likely to become more frequent and intense under a changing climate. The effect this will have on plant rarity and on species with unique nutrient acquisition traits, and thus nutrient cycling, remains poorly understood. Working within an Australian box-ironbark forest, we determined if a relationship existed between species rarity and the uniqueness of their leaf nutrient profiles, and if this relationship changed after prescribed burning. We created an index of species rarity from a data set of woody perennial species abundance in areas before and after autumn or spring burns, or left unburnt. We created indices of uniqueness for the leaf nutrient profiles of 42 woody perennial species occurring in the ecosystem, based on amounts of six macronutrients and four micronutrients found in fresh and senesced leaves of each species. Five nutrient acquisition strategies (mycorrhizal, N-fixing, carnivorous, hemiparasitic and proteoid roots) were represented in the data set. There was no community-wide relationship between rarity and uniqueness of leaf nutrient profiles, and this did not change as a result of fire. However, two hemiparasitic species were relatively rare in the ecosystem studied, and differed greatly from other species due to high K and P in senesced leaves. Thus, some of the rarest species, such as hemiparasites, can be functionally unique. Understanding the functional characteristics of rare species is important so that unique functional contributors can be identified and conserved to prevent local extinction.

Predation and cryptic coloration in a managed landscape

Protective forms of animal color, such as crypsis, are thought to reduce the probability of detection by visual predators. However, because crypsis is ostensibly intuitive, the working hypothesis of cryptic coloration is seldom tested. Additionally because crypsis is a background-specific adaptation, events which alter habitat structure and substrate composition are likely to affect rates of predation on cryptic animals; animal colors that are cryptic against one visual background may be conspicuous against different visual backgrounds. Populations of Sceloporus woodi, a cryptic diurnal lizard, occupy clear-cut stands of sand pine scrub and prescribe-burned longleaf pine habitat within the Ocala National Forest. Here, we used a combination of clay models resembling S. woodi, and spectral analysis, to examine the effects of spatial heterogeneity and model-substrate contrast on rates of predation. The rate of attack on clay models differed between substrate types and habitats, and was highest when clay models were conspicuous against the local visual background. The dorsal color of models greatly contrasted open sand and dead wood, but had similar reflectance values to leaf litter, suggesting that models were most cryptic on leaf litter. We conclude that crypsis is adaptive in this species, and that variation in rates of attack between sampling locations is related to changes in substrate composition due to management history. For instance, the data suggest that the rate of attack on clay models would decrease in response to succession in sand pine scrub, because aging in sand pine scrub results in increased amounts of leaf litter and decreased amounts of open sand. Overall, the results of this study support the theory of protective coloration.

Contrasting effects of two Acacia species on understorey growth in a drylands environment: interplay of canopy shading and litter interference

AbstractQuestionsDo tree species with similar canopy structures but distinct litter production volumes affect the understorey growth in dryland environments differently? How does rainfall impact the magnitude and sign of these effects?LocationWoodland savanna, northern Negev drylands, Israel.MethodsWe determined understorey herbaceous productivity beneath the canopy of two N‐fixing tree species (Acacia victoriae and Acacia salicina) with comparable canopy structures (canopy height and area) but distinct litter production volumes. Biomass was measured beneath A. victoriae trees and in the open area between the trees for 7 yrs and beneath A. salicina and the nearby open area for 2 yrs. Light measurements, litter biomass, fine root density and nutrients and gravimetric water content in the top soil were assessed for both species. Annual rainfall and the coefficient of variation in daily rain were used to determine rainfall effects on tree–grass relations.ResultsAcacia victoriae and A. salicina had contrasting positive and negative effects on understorey growth, respectively. Both species had comparable fine root densities, soil moisture and nutrient content beneath their canopies, with a higher soil water content than the open area. The large amount of leaf litter produced by A. salicina appeared to suppress the understorey growth, likely via light interference at the soil surface, which outweighed the positive effect of moisture conditions. Acacia victoriae that produced significantly lesser amounts of litter facilitated the understorey growth via canopy shading (likely through reducing evaporative loss). Both the rainfall amount and its intra‐annual variability reduced the magnitude of the tree effect but did not change its sign.ConclusionsTree leaf litter production may have a contrasting effect on understorey growth, ranging from positive to negative even in the same environment. Changes in rainfall amount and intra‐annual rainfall variability affect the magnitude of the effect but not its sign.

Acidic, neutral and alkaline forest ponds as a landscape element affecting the biodiversity of freshwater snails

In recent years, the number of areas remaining under the influence of acidity has increased. At all levels of ecosystems, biodiversity decreases with acidification, due to the elimination of species that are most sensitive to low pH. Forest ponds belong to a specific group that varied in location, a huge amount of leaf litter, and isolation from other aquatic environments. They are crucial in the industrial landscape with well-developed industry and human activity. The aim was to investigate the relative importance of water chemistry in explaining snail assemblage compositions and species richness in forest ponds of contrasting pH. Patterns in gastropod communities were determined from an analysis in 26 forest ponds with multivariate gradient analysis. Ponds ranged in a base mean pH from 3.0 to 9.0. pH has been found to be an important factor influencing gastropod fauna. Neutral ponds support diverse communities, typical of small water bodies. In two acidic pond types, snail fauna was different. Among the species characteristic for acidic ponds (pH < 6) were Anisus spirorbis and Aplexa hypnorum. The greatest distinct characterised alkaline ponds with the numerous appearance of alien Physa acuta. The most diverse gastropod fauna was found in neutral ponds, whereas the lowest degree of diversity was found in ponds with the lowest pH. Current knowledge of pH-associated changes in aquatic ecosystems is still incomplete because anthropogenic acidification is a recent phenomenon. It is extremely important in forest habitats, since they react more intensively to climatic factors and are often used in landscape management and planning.

Experimental nitrogen and phosphorus additions increase rates of stream ecosystem respiration and carbon loss

AbstractNitrogen (N) and phosphorus (P) enrichment reduces organic carbon (C) storage in detritus‐based stream ecosystems, but the relative effects of N and P concentrations and ratios on stream metabolic rates have not previously been tested. We tracked changes in whole‐stream ecosystem respiration (ER) and gross primary productivity (GPP), particulate organic matter (POM) standing stocks, fungal biomass, and POM‐specific respiration rates before and during 2 yr of experimental N and P enrichment in five forest streams. Nutrient additions (∼ 96 μg N L−1 to ∼ 472 μg N L−1 and ∼ 10 μg P L−1 to ∼ 85 μg P L−1) targeted dissolved N : P molar ratios of 2, 8, 16, 32, and 128. Whole‐stream ER was positively related to standing stock of wood, a seasonably stable POM compartment that varied by up to 2× among streams. Nutrient enrichment generally increased ER but had no effect on low‐level GPP. Prior to nutrient enrichment, ER was higher at lower N : P, but during enrichment ER increased with increasing N : P. Respiration rates on leaf litter and wood increased with enrichment but decreased with increasing P, and the quantity of leaf litter generally declined with increasing N. Respiration rates on fine benthic organic matter (FBOM) were higher with increasing N : P, and FBOM standing stocks decreased with increasing N. Fungal biomass did not change with nutrient enrichment. Compared to pre‐enrichment conditions, nutrients increased seasonal variation in leaf litter standing stocks and whole‐stream respiration rates. Our results demonstrate how nutrient‐stimulated loss of C from detritus‐based ecosystems occurs through the maintenance of enhanced respiration rates on detrital resources that are particularly sensitive to N inputs.

English

Mangrove crabs are mostly herbivorous which consume more amount of leaf litter of various mangrove species and also plays most important role in leaf degradation. Several studies reported that crab harbor bacteria from the environment through water and food. Bacterial species of the gut can influence the health and robustness of the host. The present study aims to isolate and enumerate the bacterial count from the gut of crabs collected from different mangrove environments.&nbsp; The results shows that maximum bacterial load was recorded in Sesarma brockii crabs gut collected from Pichavaram mangroves and minimum was observed in Metopograpsus maculatus crabs collected from Uppanar estuarine mangrove. In the same way, maximum bacterial load was observed in both water and sediment samples of Pichavaram. Bacteria belonging to the genera Bacillus, Pseudomonas and Aeromonas were found at higher levels in all the different mangrove regions. In conclusion, crabs in the various mangrove environments carry a particular bacterial flora, which reflects their environment. The Pichavaram mangrove ecosystem is endowed with a high bacterial load due to the continuous shedding of foliage into the water and subsequent decomposition than other mangrove environments. SEM results confirm that crowded populations of bacteria were attached to the gut region of the mangrove crabs. Key words: Mangrove crabs, gut microflora, isolation, characterization, sediments.

Heavy Metals and Polycyclic Aromatic Hydrocarbons in Urban Leaf Litter Designated for Combustion

Vast amounts of leaf litter have to be disposed of by city administrations. This biomass has the potential for energy conversion, but contamination with pollutants can adversely affect this usage. We investigated leaf litter samples from the city of Kassel by analyzing their heavy metal and polycyclic aromatic hydrocarbon (PAH) concentrations. Leaf samples were indeed contaminated with heavy metals and PAHs and contamination was influenced by provenience and collection technique. A simple cleaning system of washing and subsequent mechanical dewatering significantly reduced heavy metal concentration. Regression models were developed for contamination with heavy metals which showed that contamination could be successfully estimated using the total ash content of the sample as a predictor, with an R2 of up to 0.77. It can be concluded that leaf litter from cities is a possible feedstock for energetic conversion, provided a cleaning step is applied.

Nutrient uptake and growth of spinach as affected by cow manure co-composted with poplar leaf litter

PurposeWastes were composted and applied as the soils amendment to improve soil fertility and crop productivity. The study aimed at assessing the nutrient uptake and growth of spinach (Spinacia oleracea L.) grown in soils amended with cow manure after a co-composting process.MethodsSandy loam and silt loam soils were amended with cow manure after co-composting with poplar leaf litter at 1:0, 1:1, 1:2 and 1:3. The compost was applied to soil at the rate of 20 t ha−1. Spinach was grown for 8 weeks and then harvested to measure plant shoot biomass. Spinach shoot samples were digested and nutrient contents in the shoots were determined.ResultsCo-composted manure significantly improved the growth and nutrients availability to the spinach. Dry biomass, P and K contents in spinach shoot varied among manure: leaf litter ratios: 1:0 < 1:1 < 1:2 < 1:3. Conversely, N, Zn, Fe, Cu and Cd contents in spinach shoot reduced with the manure amendment with increasing amount of leaf litter. Water extractable micro-elements in the post-harvest soils were found in the order of Zn > Fe > Cu > Cd. Co-compost amendments increased the P and K availability except N, NO3 and NH4 in the post-harvest soils. Trace elements in the post-harvest soils reduced with leaf additives in the compost.ConclusionsCo-composted cow manure with leaf litter proved to be superior in terms of bioavailability of plant nutrients over the composted manure without leaf litter. This may also assist in mitigating the environmental contamination of heavy metals in the farm lands.

Densidad del estrato herbáceo y su relación con luminosidad, pH y cantidad de hojarasca en la Reserva Biológica Alberto Manuel Brenes, San Ramón, Costa Rica

La composición biótica de muchos ecosistemas está haciendo alterada rápidamente, por lo que hay una necesidad creciente de entender los procesos ecológicos y mantener su biodiversidad. Se midió la densidad del estrato herbáceo de 30 cuadrículas (50 cm2) establecidas en tres transeptos (25m x 2m), en la Reserva Biológica Alberto Manuel Brenes, San Ramón, Costa Rica. Encontramos que los factores significativos en la densidad herbácea son el pH y la cantidad de hojarasca.

Chemical constituents of Cinnamomum septentrionale leaf litter and its allelopathic activity on the growth of maize (Zea mays)

A pot experiment was conducted to study the effect of decomposing Cinnamomum septentrionale leaf litter on the growth of maize. In this study, the morphological traits of maize were significantly inhibited when the leaf litter amount reached or exceeded 40 g per pot; Furthermore, during the early growth stage or with a large amount of litter addition, the pigment contents were inhibited by C. septentrionale leaf litter. Gas chromatography–mass spectrometry was used to determine the volatile substances of leaf litter and 34 compounds were identified, several of which were reported to be phytotoxic. In conclusion, the leaf litter of C. septentrionale showed a strong allelopathic effect on the growth of maize. Thus, it is better to avoid the growing of maize under or near the C. septentrionale plantation unless the leaf litter could be eliminated in time or other effective leaf litter processing methods could be implemented.

Leaf Litter Consumption by Macroarthropods and Burial of their Faeces Enhance Decomposition in a Mediterranean Ecosystem

In many terrestrial ecosystems, large amounts of leaf litter are consumed by macroarthropods. Most of it is deposited as faeces that are easily transferred into deeper soil layers. However, the decomposition of this large pool of organic matter remains poorly studied. We addressed the question of how leaf litter transformation into macroarthropod faeces, and their burial in the soil, affect organic matter decomposition in a Mediterranean dry shrubland. We compared mass loss of intact leaf litter of two dominant shrub species (Quercus coccifera, Cistus albidus) with that of leaf litter-specific faeces from the abundant millipede Ommatoiulus sabulosus. Leaf litter and faeces were exposed in the field for 1 year, either on the soil surface or buried at 5 cm soil depth. Chemical and physical quality of faeces differed strongly from that of leaf litter, but distinctively between the two shrub species. On the soil surface, faeces decomposed faster than intact leaf litter in Quercus, but at similar rates in Cistus. When buried in the soil, faeces and leaf litter decomposed at similar rates in either species, but significantly faster compared to the soil surface, most likely because of higher moisture within the soil enhancing microbial activity. The combined effects of leaf litter transformation into faeces and their subsequent burial in the topsoil led to a 1.5-fold increase in the annual mass loss. These direct and indirect macroarthropod effects on ecosystem-scale decomposition are likely more widespread than currently acknowledged, and may play a particularly important role in drought-influenced ecosystems.

Leaf Litter Translocation and Consumption in Mangrove Ecosystems: the Key Role Played by the Sesarmid Crab &lt;i&gt;Neosarmatium malabaricum&lt;/i&gt;

Nutrient cycling in mangrove forests is strongly linked to detrital processing of leaf litter, as compared to direct herbivorous consumption. Sesarmid crabs play a key role in detrital pathways in mangrove forests by processing a large amount of leaf litter produced in the ecosystem. We studied the rate of leaf litter translocation and consumption by a sesarmid crab, Neosarmatium malabaricum , through an ex situ experiment simulating field conditions. We supplied weighed senescent leaves of Aegiceras corniculatum, Avicennia officinalis , Excoecaria agallocha and Rhizophora mucronata to the crab. When provided separately, the crab translocated leaf litter of E. agallocha the maximum, and that of Rhizophora mucronata the minimum to the burrows. When litter mixed together was provided, the rate of translocation was the highest. The crabs consumed up to 80.24% of the litter that they translocated. We found this species capable of translocating 4.39 ±1.68 g of leaf litter m -2 per day and that its population had the potential to translocate 1.81 times more leaf litter than the ecosystem produced, based on comparisons of translocation rate, density of N. malabaricum and leaf litter production in the study area. Our experiments emphasize the key role played by this crab in detrital pathways of mangrove ecosystem.

Removal of invasive shrubs alters light but not leaf litter inputs in a deciduous forest understory

The establishment and spread of non‐native, invasive shrubs in forests poses an important obstacle to natural resource conservation and management. This study assesses the impacts of the physical removal of a complex of woody invasive shrub species on deciduous forest understory resources. We compared leaf litter quantity and quality and understory light transmittance in five pairs of invaded and removal plots in an oak‐dominated suburban mature forest. Removal plots were cleared of all non‐native invasive shrubs. The invasive shrubs were abundant (143,456 stems/ha) and diverse, dominated by species in the genera Ligustrum, Viburnum, Lonicera, and Euonymus. Annual leaf litter biomass and carbon inputs of invaded plots were not different from removal plots due to low leaf litter biomass of invasive shrubs. Invasive shrub litter had higher nitrogen (N) concentrations than native species; however, low biomass of invasive litter led to low N inputs by litter of invasive species compared to native. Light transmittance at the forest floor and at 2 m was lower in invaded plots than in removal plots. We conclude that the removal of the abundant invasive shrubs from a native deciduous forest understory did not alter litter quantity or N inputs, one measure of litter quality, and increased forest understory light availability. More light in the forest understory could facilitate the restoration of forest understory dynamics.

Soil carbon and nitrogen stocks in forests along an altitudinal gradient in the eastern Himalayas and a meta-analysis of global data.

High-altitude soils potentially store a large pool of carbon (C) and nitrogen (N). The assessment of total C and N stocks in soils is vital to understanding the C and N dynamics in terrestrial ecosystems. In this study, we examined effects of altitude and forest composition on soil C and N along a transect from 317 to 3300ma.s.l. in the eastern Himalayas. We used meta-analysis to establish the context for our results on the effects of altitude on soil C, including variation with depth. Total C and N contents of soils significantly increased with altitude, but decreased with soil depth. Carbon and N were similarly correlated with altitude and temperature, and temperature was seemingly the main driver of soil C along the altitudinal gradient. Altitude accounted for 73% of the variation in C and 47% of the variation in N stocks. Soil pH and cation exchange capacity were correlated with both soil C and N stocks. Increases in soil C and N stocks were related to forest composition, forest basal area as well as quantity of leaf litter that were in turn influenced by altitude and temperature. Concentrations of C in foliage increased by 2.1% for every 1000m rise in altitude, while that in leaf litter increased by 2.3%.

Dieback of riparian alder caused by thePhytophthora alnicomplex: projected consequences for stream ecosystems

SummaryAlder trees (Alnusspp.) are key nitrogen‐fixing riparian species in the northern hemisphere. Inputs of nitrogen‐rich leaf litter from alder into stream food webs can contribute significantly to nitrogen dynamics at local and landscape scales. Alder trees also provide habitats for terrestrial and aquatic organisms, and help stabilize river banks.Recently, substantial declines in alder stands have occurred along streams in Europe, with damages observed in some parts of North America also. A major driver has been the invasive oomycete pathogenPhytophthora alnispecies complex,which can spread rapidly along stream networks.This review synthesises information on the pathogen, processes of spread and infection, and its impacts on alder. We further address the potential ecosystem‐level and management consequences of the decline of alder, and highlight research needs.The alder dieback caused byP. alniis associated with reductions in shade and quality and quantity of leaf litter. A decline in the structural integrity of branches and roots further threatens bank stability. Stream banks dominated by other tree species or no trees at all will result in ecosystem‐level changes both above and below the waterline.TheP. alnitaxonomic complex includes different species with varying phenotypes. An improved understanding of their environmental tolerances, virulence and evolution, along with the processes regulating the spread and impacts of the pathogen, would assist in identification of the riparian and stream systems most vulnerable not only to invasion but also to the heaviest disease outbreaks and ecosystem‐level impacts.Within theP. alnicomplex, the highly pathogenic hybrid speciesP. x alniis favoured by mild winters and warm, but not excessively hot summer temperatures suggesting possible changes in distribution and level of impact under future global climate change.

Less fuel for the fire: malleefowl (Leipoa ocellata) nesting activity affects fuel loads and fire behaviour

Context Fire is an important driver of species distributions globally. At the same time, biota also influence fire regimes. Animal activities that modify fuel characteristics may influence fire regimes and hence ecosystem function. However, apart from herbivory, animal effects on fuels and fire behaviour have rarely been studied. Aims We examined the effect of nest building by malleefowl (Leipoa ocellata) on litter fuel loads and fire behaviour in the fire-prone, semiarid mallee ecosystem of south-eastern Australia. Malleefowl nests consist of mounds constructed by raking large amounts of leaf litter from the surrounding area. Mound-building activity is likely to affect fuel loads and potentially affect fire behaviour in this environment. Methods Litter cover and mass were compared between paired mound and non-mound sites. Fire behaviour modelling was used to determine whether differences in fuel load were likely to translate into differences in fire behaviour. Additionally, in an area recently burnt by wildfire, the minimum diameter of burnt stems was compared between mound and non-mound sites to determine the effects of malleefowl activity on fire intensity. Key results Malleefowl nesting activity reduced litter fuel loads around mounds. Fire behaviour modelling and post-fire minimum stem diameter measurements showed this led to reduced fire intensity around mounds, even under extreme fire weather conditions. Conclusions The likelihood and intensity of fire is reduced around active malleefowl mounds. Malleefowl nesting contributes to more heterogeneous burn patterns in mallee vegetation. This in turn may contribute to the formation of fire refuges. Implications Few studies have examined the effects of animal activities on fire. This study demonstrates that non-trophic interactions of fauna with fuels may influence fire regimes. Species that reduce or disrupt the continuity or connectivity of fuels could have similar effects to malleefowl in fire-prone regions. Further examination of the interactions of animals and fire regimes will contribute to a better understanding and conservation management of fire-prone ecosystems.

El Niño southern oscillation and seasonal drought drive riparian input dynamics in a Mediterranean stream

Inland waters substantially contribute to global carbon fluxes, and within them, low-order forested streams are important processors of allochthonous organic matter (OM) inputs. Leaf litter quantity and quality are expected to change in response to global change (e.g., climate change, land use change) but few long-term studies exist to better understand these shifts. The goal of this study was to assess the quantity and quality of OM sources to determine which global and local environmental factors control the dynamics of OM at the reach scale. The study was performed on a Mediterranean stream edged by a deciduous riparian forest over a 10-yr-time period. Riparian inputs, benthic and transported OM, and its carbon and nitrogen content were determined. The quantity of riparian inputs (912 ± 56 g dry mass m−2 yr−1) was comparable to temperate regions with deciduous riparian forests, but the Mediterranean climate determined the different dynamics of these inputs. El Niño Southern Oscillation was strongly related to the interannual variability in riparian inputs through changes in precipitation. The annual amount of inputs depended on previous cumulated nonflow periods, with successive nonflow periods causing a progressive decrease in riparian inputs. The distribution of inputs throughout the year followed either a unimodal or bimodal pattern according to the absence or presence of a nonflow period in summer. In addition, drought caused lower quality (higher carbon : nitrogen molar ratio) riparian inputs. Changes in the quantity and quality of OM were explained by both present and past local and global factors.

Effect of mangrove restoration on crab burrow density in Luoyangjiang Estuary, China

Abstract Background Mangrove restoration seeks to restore or rebuild degraded mangrove systems. The methods of mangrove restoration include ecological projects and restoration-oriented technologies, the latter of which are designed to restore the structure, processes as well as related physical, chemical and biological characteristics of wetlands and to ensure the provision of ecosystem services. As important components of mangrove ecosystem, benthic organisms and crabs play a key role in nutrient cycling. In addition, mangrove restoration, such as vegetation restoration measures, can lead to changes in the benthic faunal communities. This study investigates whether the presence of different mangrove species, age and canopy cover of mangrove communities affect the density of crab burrows. Methods The Luoyangjiang Estuary, in the southeast of Fujian Province, was selected as our research area. A survey, covering 14 sites, was conducted to investigate the impacts of mangrove restoration on the density of crab burrows in four rehabilitated forests with different stand ages and canopy. Results It was found that differences in vegetation types had a large impact on crab density and that the density of crab burrows was lower on exposed beaches (non-mangrove) than under mature Kandelia candel, Aegiceras corniculatum and Avicennia marina communities. In general, the amount of leaf litter and debris on mangrove mudflats was greater than on the beaches as food sources for crabs. Two-factor analysis of variance (ANOVA) shows that changes in mangrove species and age since restoration had different effects on crab burrow density. The effect of canopy cover was highly significant on crab burrow density. Conclusions The results suggest that in the process of mangrove restoration the combined effects of mangrove stand age, canopy cover and other factors should be taken into account. This study further supports the findings of the future scientific research and practice on mangrove restoration and management measures.