Litter Deposition Research Articles

Effect of Thinning Intensity on Litterfall Biomass and Nutrient Deposition in a Naturally Regenerated Pinus Pseudostrobus Lind. Forest in Oaxaca, Mexico

ABSTRACT Litterfall is an important component of forest biomass and nutrient cycling, and can have key impacts on soil fertility through its decomposition. However, theeffect of forest management on litterfall remains unclear. We evaluate the impact of thinning intensity on the biomass and nutrient content (C and N) of litterfall in Pinus pseudostrobus forest in Oaxaca, México, across two thinning intensities in areas with either high or low residual basal area and across seasons. There was significantly higher litter carbon content in the least intensive thinning treatment, but no significant differences in biomass or nitrogen content between treatments. However, there was a significant correlation between residual basal area and litter biomass at the p < .1 level. We found a clear seasonal pattern in litterfall fluxes, with 1.5 times more litter deposition in autumn’s dry season compared to spring. We find that the thinned stand of P. pseudostrobus generated an annual mean litter biomass of 1059.27 ± 346.04 kg ha−1 with mean carbon content of 125.31 ± 46.43 kg ha−1 and mean nitrogen content of 4.76 ± 1.43 kg ha−1. These values present an important contribution for modeling of biomass and nutrient cycling in this ecologically and economically important forest type.

Indirect effects of climate change inhibit N2 fixation associated with the feathermoss Hylocomium splendens in subarctic tundra

Mosses can be responsible for up to 100% of net primary production in arctic and subarctic tundra, and their associations with diazotrophic cyanobacteria have an important role in increasing nitrogen (N) availability in these pristine ecosystems. Predictions about the consequences of climate change in subarctic environments point to increased N mineralization in soil and higher litter deposition due to warming. It is not clear yet how these indirect climate change effects impact moss-cyanobacteria associations and N2 fixation. This work aimed to evaluate the effects of increased N and litter input on biological N2 fixation rates associated with the feathermoss Hylocomium splendens from a tundra heath. H. splendens samples were collected near Abisko, northern Sweden, from a field experiment with annual additions of ammonium chloride and dried birch litter and the combination of both for three years. Samples were analyzed for N2 fixation, cyanobacterial colonization, C and N content and pH. Despite the high N additions, no significant differences in moss N content were found. However, differences between treatments were observed in N2 fixation rates, cyanobacterial colonization and pH, with the combined ammonium+litter treatment causing a significant reduction in the number of branch-colonizing cyanobacteria and N2 fixation, and ammonium additions significantly lowering moss pH. A significant, positive relationship was found between N2 fixation rates, moss colonization by cyanobacteria and pH levels, showing a clear drop in N2 fixation rates at lower pH levels even if larger cyanobacterial populations were present. These results suggest that increased N availability and litter deposition resulting from climate change not only interferes with N2 fixation directly, but also acidifies moss microhabitats and reduces the abundance of associated cyanobacteria, which could eventually impact the N cycle in the Subarctic.

Decline in nutrient inputs from litterfall following forest plantation in subtropical China

The rapid conversion of natural broadleaved forests to plantations (mainly Cunninghamia lanceolata and Pinus massoniana) in subtropical China has resulted in a substantial decline in soil fertility, but the biogeochemical mechanism behind this decline remains not fully understood. Litterfall is an important source of nutrients that are returned to soils through litter deposition and decomposition. We assessed various types of litterfall (leaves, twigs, flowers, fruits and unidentified litter) monthly and their carbon (C), nitrogen (N), phosphorus (P) and potassium (K) inputs to soils in a natural broadleaved forest (Castanopsis carlesii) and in P. massoniana and C. lanceolata plantations over 10 years. The total litterfall was 21–25% lower in plantations than in the C. carlesii forest, resulting in much lower C (−17% and −14%), N (−62% and −52%), P (−24% and −32%) and K (−53% and −40%) inputs from litterfall in the P. massoniana and C. lanceolata plantations. Leaves accounted for 72–76% of the total litterfall, so we compiled available data on the nutrient release from the three foliar litters during the 1st year of decomposition throughout subtropical China. The decomposition rates of P. massoniana and C. lanceolata needle litter were only half that of C. carlesii leaf litter, and the lower initial quality of P. massoniana and C. lanceolata needle litter relative to C. carlesii leaf litter resulted in significantly lower amounts of N (−95% and −76%) and P (−48% and −25%) being released. These results suggest that low nutrient (N, P and K) inputs due to low litter production and slow nutrient release due to slow litter decomposition are two important biogeochemical reasons for the decline in soil fertility in plantations in subtropical China.

Effect of Biofertilizers Application on Soil Biodiversity and Litter Degradation in a Commercial Apricot Orchard

The aim of the present experiment was to determine if the supply of biofertilizers could differently stimulate the native microbiota, thus determining different patterns of organic material decomposition processes. The microbial composition of soil and litter was investigated by next generation sequencing using a metabarcoding approach. The chemical structure of the decomposing litterbags was investigated through the TG-DTA analysis and NIR spectroscopy. The study was conducted in an apricot orchard in Italy, and two different type of biofertilizers (AMF and Trichoderma spp.) were compared to unfertilized control over one year. Bacteria and fungi in soil, 162 days from litter deposition, evidenced differentiated clusters for control and both biofertilizers; on the other hand, only fungal composition of litterbags was modified as a consequence of Trichoderma spp. supply; no effect was observed in the bacterial community of litterbags. NIR and TG-DTA analysis evidenced a significant change over time of the chemical composition of litterbags with a faster degradation as a consequence of Trichoderma spp. supply testified by a higher degradation coefficient (1.9) than control (1.6) and AMF (1.7). The supply of biofertilizers partially modified the bacteria community of soil, while Trichoderma spp. Influenced the fungal community of the litter. Moreover, Trichoderma spp. Evidenced a faster and higher degradation of litter than AMF-biofertilizers, laying the foundation for an efficient use in orchard.

Litter mass, deposition rate, and decomposition in nitrogen‐fertilized or grass–legume grazing systems

AbstractPlant litter deposition and decomposition play important roles in grassland nutrient cycling. The objective was to evaluate plant litter responses and estimate the N returns via plant litter in contrasting grazing systems, since legume inclusion is hypothesized to result in similar quantities of N return compared with N‐fertilized grass systems. Systems were (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) during summer with a mixture of N‐fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N); (b) bahiagrass (no N fertilizer) during summer and a rye–oat–clovers (Trifolium spp.) mixture + N in winter (Grass+Clover); and (c) bahiagrass (no N fertilizer in summer) with strip‐planted rhizoma peanut (Arachis glabrata Benth.) during summer with a rye–oat–clovers mixture + N during winter (Grass+CL+RP). Litter mass was greatest for Grass+N during October (4,430 kg organic matter [OM] ha−1) and least for Grass+CL+RP in June (490 kg OM ha−1). Litter N concentrations were greatest in Grass+N (16 g kg−1), with similar N concentration for Grass+Clover and Grass+CL+RP litter (14 g kg−1). Contribution of C3 species to litter mass increased from May to July but decreased thereafter. Overall, there was a net return of 47 kg N ha−1 yr−1 via litter across the three systems, and litter decomposition was similar in the three systems. Inclusion of forage legumes during cool and warm seasons in grazing systems has the potential to return similar amounts of N through plant litter deposition as grasses receiving moderate levels of N fertilizer.

Poultry litter and the environment: Microbial profile of litter during successive flock rotations and after spreading on pastureland.

With the increasing demand for broiler meat, a thorough evaluation of the microbial community within the broiler houses and sites where litter is deposited is critical to animal and environmental wellbeing. However not much is known in this arena, so our work evaluates the litter bacterial microbial community within a house over a 2.5 year period through 11 flock rotations, a partial and a total cleanout, and the subsequent deposition of the litter as fertilizer on pastureland. The effects of both time and management practices correlated with alterations of the litter microbial community. The cleanout practices and introduction of new bedding had minimal influence on the house microbial community once it was established, which generally showed a consistent increase in the proportion of Actinobacteria and a decrease in Firmicutes over the 11 flock rotations. Analysis of the bacterial profile at the genus level gave increased resolution, revealing changes during the first and second flock rotation and after the total cleanout. The disturbance of the partial cleanout seemed to be buffered by the supporting conditions within the house while the total cleanout showed a small, but significant influence. The pastureland deposition of litter, however, was affected by time and abiotic factors that changed the litter microbial community structure weekly. The stockpiled litter had an increase in the phyla Actinobacteria and the class Bacilli that commonly have microbes utilizing nitrogen and decaying materials, in comparison to Native soil. Further, the soil beneath where the litter was stored for 20 weeks, lost diversity, indicating a possible effect of the litter stockpiling on environmental quality at that site. How management practices affect the composition of the microbial community within the litter of the broiler house is of interest in terms of bird health and environmentally for future utilization of spent litter.

Nitrogen fertilizer increased litter deposition and litter N in warm-climate grasslands

In warm-climate grasslands, litter deposition and decomposition are one of the main pathway of nutrient cycling. The application of nitrogen (N) fertilizer or the inclusion of a legume in such grasslands modifies litter characteristics and chemical composition. This study evaluated how the N supply of palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster] pastures affect litter characteristics two years after seeding. Treatments were palisadegrass fertilized or not with N (150 or 0 kg N ha???1 year???1) or mixed with the legume forage peanut (Arachis pintoi cv. Amarillo). The experimental period covered two consecutive rainy seasons. Nitrogen fertilization increased by 43 and 62% the existing litter mass (organic matter, OM), and by 32 and 23% the litter deposition rate compared to unfertilized palisadegrass or legume-grass mixtures, respectively. Both variables were affected by grazing cycle (GC), with low litter deposition rate (14 kg ha???1 d???1 OM) and existing litter mass (1390 kg ha???1 OM) in the GC4 due to low rainfall. Nitrogen fertilized palisadegrass had greater litter N concentration (7.9????????0.4 g kg???1 OM???C:N ratio 34????????2) than in monoculture or legume-grass mixtures (C:N ratios 45 and 58????????2, respectively). Our results indicated that N fertilization of palisadegrass increased litter accumulation, however, N fertilization was not a key driver of the litter decomposition rate, even though it increased litter N concentration. After 2 years of establishment, the proportion of forage peanut in the litter was still low, reducing the benefits of legume inclusion to enhance litter nutrient cycling in these pastures.

SEASONALITY IN LITTERFALL PRODUCTION IN A NATIVE FOREST IN THE CENTRAL REGION OF RS, BRAZIL

Studies on litter deposition are considered an important indicator of environmental quality of forest ecosystems. It is the main route of entry of organic matter and nutrients to forests. The objective of this study was to quantify the annual litterfall and seasonality in a fragment of native forest located in São Sepé in the Central Depression of Rio Grande do Sul. The experiment was conducted in a fragment of a Seasonal Semideciduous Forest. Inside this forest, in a place with homogeneous conditions, five plots of 20 m x 15 m length were systematically allocated 30 meters away from each other, where five litterfall traps were distributed in each plot (0,1963 m2 each trap), totaling 25 traps. The collection of all plant material deposited by the trees in the collectors was performed monthly in a four-year period. In the laboratory, the samples were separated into leaves, small twigs (diameter &lt; 0.5 cm) and miscellaneous, and after they were oven dried and weighed on a precision balance. Higher litterfall was observed in the spring, with the highest return peaks mainly in October, indicating a seasonal deposition behavior. The mean litterfall was 6.56 Mg ha-1 year-1; of this total, the leaves were responsible for 67.61%, followed by the miscellaneous with 19.04% and the small twigs with 13.29%. Only a high significant correlation was obtained between the miscellaneous fraction and the temperature.

Predicting flooding tolerance of native tree species to restore flooded forests

AbstractAimFlooded forests are critically important for supplying water‐related ecosystem services, but their restoration has been severely limited by low seedling performance due to flooding stress. We classified the flooding tolerance of 15 native tree species in a nursery‐based method to guide species selection for restoring a flooded forest.LocationAtlantic Forest, São Paulo State, Brazil.MethodsWe first exposed 15 native tree species typical of flooded forests to four flooding conditions (i.e., normoxia and three increasing hypoxia levels): no flooding, up to the middle of the root system, up to the root collar, and 2 cm above the root collar. After nine months, we evaluated seedling survival, growth (height and stem diameter), and the occurrence of hypertrophied lenticels and adventitious roots. Seedling survival and growth data were combined to create a flooding tolerance index. Further, we planted the same species in two degraded swampy areas under three soil preparation methods: planting seedlings in regular planting holes, on mounds, and in between furrows. We assessed seedling survival and stem diameter of these seedlings after one year.ResultsFlooding tolerance index was significantly correlated to the occurrence of hypertrophied lenticels, but not of adventitious roots. Classifying flooding tolerance of tree species was effective in predicting species growth, but not seedling survival, in restoration plantations. Overall, seedling performance in restoration plantations was highly influenced by species identity, but not by soil preparation methods.ConclusionsSpecies selection to improve restoration performance of flooded forests can be guided by simple and fast screenings performed in nurseries before planting. Pioneer trees may facilitate the establishment of species less tolerant to flooding by reducing water saturation of superficial soil layers and enhancing micro‐relief heterogeneity by litter deposition. Only a few native species should initially be used in the restoration of flooded forests with high water tables.

Soil carbon status after vegetation restoration in South West Iceland

Reclamation of degraded land using revegetation is one way of sequestering carbon into the soil. In this study an assessment was done to estimate the status of soil carbon amounts after revegetation with trees and grass in South West Iceland (Hafnarmelar). Natural woodland and eroded plots were part of the assessed plots as controls making four treatments. Soil samples were analysed for bulk density, carbon content and soil texture. Total % carbon (C) was analysed using vario MAX CN analyser (measured % C) and Loss on Ignition (calculated % C). The results showed that natural woodland had higher (9.32%) C than the tree treatment (4.91%), and both had significantly higher C than the grass (1.12%) and the eroded (0.76%) treatments (p < 0.0001). The amount of C in the grass and the eroded treatments were not statistically different (p > 0.0566). Notably, the grass treatment had carbon below the minimum expected level of 1.5% in Icelandic Andosol under vegetation. The natural woodland and the tree treatment had fine soil texture than the grass and eroded plots. Results suggest that where land has been properly restored or kept in natural condition, soil properties improve significantly especially when trees are part of the restored vegetation. The natural woodland had possibly not lost the old carbon-rich soil, as was the case with the tree, grass and eroded plots hence more time for development of various soil properties. Moreover, more litter deposits in natural woodlands and partly in the tree treatments might have contributed to higher carbon than in the grass and eroded treatments. Furthermore clay content variations (natural woodlands and the tree treatments had finer soil texture) might also be responsible for C limitations in the grass and the eroded treatments. Therefore, more restoration efforts are encouraged. The results also showed that LOI is a good method for C estimation but not very accurate estimator of soil organic carbon unless equations are developed with respect to known carbon content of particular soil type.

Understanding the Role of Litter Decomposition in Restoration of Fly Ash Ecosystem.

Plant species possess a huge potential in restoration of fly ash ecosystem. Litter deposition and its decomposition in the ash deposited sites are two important processes of the fly ash ecosystem. In order to identify the biological potential of a plant species to aid restoration of fly ash deposited sites, it is needed to assess leaf litter decomposition as well as nutrient release pattern. In the present investigation, we studied the leaf litter decomposition of the plant species (Leucaena leucocephala, Pithecellobium dolce and Prosopis juliflora) and mix plantation in the fly ash ecosystem. The litter bag experiment was conducted in the area of plantation on the fly ash deposited site during a period of 365days. Percentage of C and N was higher in L. leucocephala > P. dolce >Mix Plantation > P. juliflora while C/N ratio was higher in P. juliflora >Mix Plantation > L. leucocephala > P. dolce. L. leucocephala and P. dolce showed relatively fast decomposition rates (k = 1.27, 1.17), respectively while mix plantation (k = 0.82) and P. juliflora (k = 0.73) exhibited relatively slower decomposition rates. Thus, we noted that the decomposition rate of L. leucocephala was greater than the other selected species. This shows that the species having faster decomposition rate and nutrient release could be a factual choice for rehabilitation of fly ash deposited sites.

Bark decomposition in white oak soil outperforms eastern hemlock soil, while bark type leads to consistent changes in soil microbial composition

Bark decomposition is an underexamined component of soil carbon cycling and soil community assembly. Numerous studies have shown faster decomposition of leaf litter in “home” environments (i.e. within soil adjacent to the plant that produced the leaves), suggesting potential legacy effects from previous deposition of similar litter. This is expected to occur through, in part, accumulation of microorganisms that metabolize substrates the litter provides. Whether a similar “home-field advantage” (HFA) exists for bark decomposition is unknown, but this dynamic may differ because annual bark deposits to soil are minimal relative to leaf deposits. We hypothesized that (1) as with leaf litter, bark will be better decomposed near to the tree from which it was collected, and (2) that decomposing bark can initiate change in soil microbial composition. To test these hypotheses, we used a full factorial design that included two bark types (collected from eastern hemlock, Tsuga canadensis, and white oak, Quercus alba) and two soil types (‘home’ and ‘away’) within a temperate mixed hardwood forest at the Shale Hills Catchment in central Pennsylvania, USA. Bark was excised from 25 replicates of each tree type, buried in either home or away soil, and incubated belowground from July 2017 to June 2018. Decomposition was assessed through proportionate mass loss over time, while microbial composition in the bark and adjacent soil was assessed through high-throughput sequencing of 16S rRNA gene and fungal ITS fragments. Overall, bark degraded faster in white oak soils, and there was also an effect of bark type on decomposition. Although white oak bark decomposed more quickly in its home environment, this could be due to either soil conditioning or inherent differences in the soils in which each species grows. Soil microbial assemblages also sorted according to bark type rather than soil type, suggesting that bark strongly influences the composition of nearby microorganisms during decomposition. Our results suggest that both bark type and soil type are important factors during bark decomposition, but our findings suggest no clear evidence for HFA.

Chinese privet (Ligustrum sinense Lour.) alters the timing of litterfall and nutrient quality of leaf litter inputs in invaded riparian forests

The invasive non-native shrub Chinese privet occupies riparian forests throughout the southeastern US however little is known regarding its ability to impact ecosystem processes. This study aimed to characterize phenological patterns of privet litterfall, litter chemistry, and changes in availability of mobile soil nutrients within riparian zones invaded by privet. Comparisons of native and invaded sites showed that privet invasion alters the timing but not quantity of litter deposition. In contrast to native species, total privet litterfall displayed little seasonal variation however invaded sites had similar total litter mass compared to native sites. Within invaded sites privet litter was 26% of total litterfall in spring. Privet leaf litter was seasonally enriched in nitrogen during winter as compared to fall and spring. Compared to native sites, invaded sites had significantly increased soil nitrate availability and decreased soil carbon:nitrogen ratios. In contrast, dissolved organic matter and dissolved nitrogen in soil solution was lower in invaded compared to native sites. Results suggest that privet enhances litter and inorganic nitrogen availability in ways that have potential to impact decomposer and detritovore communities in the riparian zone and adjacent aquatic systems.

Litter input in cerrado, cerradão and forest environments in Amazon, Brazil

Production and decomposition of litter is one of the most important entry sources of nutrients into the soil layers, especially in Amazonian environments, where the soils with low natural fertility are. The study aimed to quantify the litter-forming material intake in cerrado, cerradao and forest environments in the Amazon. Ten conical collectors were set up in each study environment. Collections were monthly held for one year. After each collection, the fractions of leaves, branches, reproductive material and barks were all screened. The total litter production was of 4.24; 11.48 and 12.58 Mg ha-1 year-1 in the cerrado, cerradao and forest areas, respectively. The monthly deposition in the cerrado ranged from 0.13 Mg ha-1 to 0.75 Mg ha-1, while in the cerradao the values were 0.52 and 2.18 Mg ha-1 and in the forest, they were between 0.70 Mg ha-1 and 1.97 Mg ha-1. The analysis and interpretation of the results allowed concluding that the litter deposition, for both the forest and cerradao areas, is higher than the one for the cerrado area, having a greater deposition in a period of water scarcity observed for all areas of this study, with the leaves fraction having contributed with the highest percentage.

Root Activities of Re-Vegetated Plant Species Regulate Soil Nutrients and Bacterial Diversity in the Riparian Zone of the Three Gorges Reservoir

Plants modify the soil microenvironment through root exudation. It is important to study the dynamic changes of soil ecosystem from the perspective of root-soil-microbe interactions after vegetation restoration in the riparian zone of the Three Gorges Reservoir (TGR). The rhizosphere and bulk soils of Cynodon dactylon, Hemarthria altissima, Taxodium distichum, and Salix matsudana were collected from the vegetation restoration demonstration base of Ruxi River to explore the differences in nutrient contents and enzyme activities between the rhizosphere and bulk soils. At the same time, the diversity of the bacterial community in the rhizosphere and bulk soils was also investigated using the high throughput sequencing method, with the aim to clarify the growth adaptabilities and nutritional utilization strategies within a more precise rhizosphere range. The results showed that ① Suitable plants enhanced the transformation efficiency of rhizosphere nutrients in different ways to improve their adaptability to the soil environment in the TGR. Compared with bulk soil, root activities had significant effects on nutrient contents in the rhizosphere. Among them, SOC, AN, TN, and AP were enriched significantly to a certain degree, while the changes of potassium were not consistent in different plant species. ② In the process of vegetation restoration, the deposition of litter and root secretion indirectly regulated soil enzyme activity. Invertase, urease, and acid phosphatase, all exhibited positive rhizosphere effects (R/S>1) in these four suitable plant species. However, considering the differences in root structure and physiological characteristics between herbaceous and woody plants, the rhizosphere effect of these three enzymes in four plants was different. ③ The results of high-throughput sequencing showed that there was no significant difference in bacterial community diversity between the rhizosphere and bulk soil of four suitable plant species in the TGR. In addition, Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, Bacteroidetes, Planctomycetes, Cyanobacteria, Firmicutes, Nitrospirae, Gemmatimonadetes, WS3, and Crenarchaeota were the twelve most abundant bacterial phyla in the rhizosphere and bulk soils, serving the ecological functions of nutrition absorption and disease suppression. Their colonization was found to be beneficial to the stress resistance of plants growing in harsh riparian ecosystems in the TGR.

Exotic Prosopis juliflora suppresses understory diversity and promotes agricultural weeds more than a native congener

Exotic invasive plant species alter ecosystems and locally extirpate native plant species, and by doing so alter community structure. Changes in community structure may be particularly important if invaders promote species with certain traits. For example, the positive effects of most invaders on soil fertility may promote species with weedy traits, whether native or not. We examined the effects of two co-occurring Prosopis congeners, the native P. cineraria and the exotic invader P. juliflora, on species identified as “agricultural weeds” and species that were not agricultural weeds in the United Arab Emirates. When compared to plots in the open, P. cineraria canopies were associated with lower richness and density of non-weeds while having no impact on agricultural weed species. In contrast, there was lower richness and densities of non-weeds under canopies of P. juliflora, but higher densities of agricultural weeds than in the open surrounding the canopies. These patterns associated with Prosopis congeners and understory plant community composition might be due to the much higher litter deposition, if litter is inhibitory, and shallow root biomass under P. juliflora, or the different soil properties that corresponded with the two Prosopis canopies. In general, soils contained more nitrogen under P. juliflora than P. cineraria, and both understories were more fertile than soil in the open. Our results suggest that evolutionary history may play a role in how exotic invasive species may select for some traits over others in plant communities, with an exotic invader potentially creating reservoirs of agricultural weeds.

What Happens to a Mediterranean Microtidal Wave-dominated Beach During Significant Storm Events? The Morphological Response of a Natural Sardinian Beach (Western Mediterranean)

Trogu, D.; Buosi, C.; Ruju, A.; Porta, M.; Ibba, A., and De Muro, S., 2020. What happens to a Mediterranean microtidal wave-dominated beach during significant storm events? The morphological response of a natural Sardinian beach (western Mediterranean). In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 695-700. Coconut Creek (Florida), ISSN 0749-0208.The short-term effects of storm events on the coastline morphology of natural, microtidal, wave dominated beaches located in the western Mediterranean are still poorly documented. Since one of the most visible consequences of a warming climate is an increase in the intensity and frequency of extreme weather conditions, it appears important to know the response of natural and urban beaches to these storm events.The spatial shoreline variability of a natural Sardinian beach was assessed in our study, based on video camera monitoring data from August 2013 to August 2015 along a 0.3 km stretch of sandy beach. This methodology has been applied in the SW coastal sector of Sardinia where severe storm events mainly related to southwesterly winds (about 50 km/h on average) can induce important morphological changes. These include shoreline retreat/progradation, erosion, beach rotation, reconfiguration of nearshore bars and the deposition of significant seagrass beach-cast litters. Our study showed an erosion and a consequent accretion of the studied beach of about 20 m in two days after the event (SW wind and waves) as a result of the deposition of the Posidonia oceanica beach-cast litter. This morphological response induced by storm events is crucial for coastal managers to plan beach management (for example beach cleaning practice), to prevent coastal risk and to understand the importance of seagrass berm deposition in the formation of natural Mediterranean beaches.

Gas Emission and Soil Chemical Properties Associated with Underground Coal Fires, Wuda Coalfield, Inner Mongolia, China

The coal fire area in the Wuda coalfield is divided into four parts based on the degree of burning and on surface characteristics: sub-area B is characterized by degraded vegetation, sub-area A has spontaneous combustion but no obvious features, sub-area O has vents and cracks, and sub-area C is characterized by red pyro-metamorphic rocks. Emitted gas contents and temperature at the surface were measured and analyzed. In addition, soil samples were collected for analysis of chemical soil properties. The compositions and concentrations of emitted gases vary from one sub-area to another. The nearly the same correlations among gas contents in sub-area A and in sub-area O indicate that their generation mechanism is the same. SO2, H2S, C2H6, C2H4, and C2H2 can only be detected near the cracks and vents in sub-area O. CO and H2 can still be detected in sub-area C, although the CO2 and CH4 contents in sub-area B are higher. Sub-areas A and B exhibit high organic matter contents due to plant nutrient accumulation and deposition of plant litter, whereas organic matter contents decrease at the vents and cracks in sub-area O and in sub-area C because of pyrolysis, leaching, and erosion. Soil near the vents and cracks in sub-area O show strong acidity, and soil pH is correlated with total salt contents of soil, which are composed mainly of Al-, K-, Mg-, or Fe-bearing sulfates. Sub-area A showed weak soil acidity, which was the result of acidification of pore water in soil due to their long-term exposure to CO2 and SO2. Total salt contents in soil in the coal fire area show no significant difference compared to those in the background area except near the vents and cracks in sub-area O. The findings of this study suggest that gas emission and soil chemical properties are reliably related to the underground coal fires.

Helocrenic springs as sources of nutrient rich fine particulate organic matter in small foothill watershed.

Despite the large number of studies devoted to organic matter dynamics in fluvial ecosystems, the detrital pathways of spring headwater systems remain neglected. In particular, spring wetlands (helocrenes or seepages) might have considerable influence on downstream headwater stream systems due to the alteration of the nutrient and organic matter content of the water. In this study, we examined fine particulate organic matter (FPOM) drained from helocrenic springs to describe its downstream transport. We studied the quantity, nutrient content and physical components of FPOM gathered from the outflowing water using continuous sediment samplers. The nutrient content of local leaf litter deposits, residence time of water in the springs and concentration of dissolved nutrients in spring sources and outflows were also measured to characterize the inputs and outputs of the studied system. The results show that headwater spring wetlands represent a significant source of high-quality FPOM for downstream river networks. The estimated concentration of FPOM (<1000 μm) in the 11 investigated springs was 3.1 ± 2.5 mg.L-1. In general, the FPOM was relatively nutrient-rich (N = 19.25 ± 4.73 mg.L-1; P = 2.04 ± 0.78 mg.L-1; Ca = 9.65 ± 2.63 mg.L-1; S = 4.07 ± 1.16 mg.L-1; C = 278.68 ± 80.81 mg.L-1). The C:N and C:P ratios in the local leaf litter deposits were higher than in FPOM (41.04 ± 14.32 vs. 14.70 ± 2.46 and 591.7 ± 168.83 vs. 154,77 ± 64,73, respectively), indicating that suspended FPOM is more nutritious for consumers. A significant trend in terms of size fractions of FPOM was identified: with decreasing C:N and C:P ratios particle size decreases as well. Overall, the data suggest that the relatively small helocrenes can serve as an organic matter transformers, receiving primary particles and dissolved organic matter, transforming them and favouring their transport downstream. These biotopes may represent a substantial discontinuity of the river continuum at its origin, important for nutrient dynamics and food supply of associated biotic communities.

Soil and Nutrient Cycling Responses in Riparian Forests to the Loss of Ash (Fraxinus spp. L) from Emerald Ash Borer (Agrilus planipennis, Fairmaire)

Emerald ash borer (EAB) is an alien invasive species that is spreading across Canada and the United States killing ash trees. In riparian forests where ash may be abundant; loss of ash can induce significant structural changes; including the creation of canopy gaps; changes in light penetration; expansion of ground vegetation; and alteration of soil nitrogen and carbon cycling. In 2014 and 2015, we examined the effects of EAB-caused gaps in riparian forests on soil nutrient dynamics. Two sites with different infestation timelines, a “new” site (mortality in past 2–3 years) and an “old” site (infested 10 years previous) were selected to determine temporal differences in effects of canopy gaps created by ash loss on litterfall, herbaceous ground vegetation, and soil nutrient cycling. Within both sites, plots with clustered dead ash (canopy gap plots—CG) were paired with nearby plots of full canopy and no ash (canopy closed plots—CC), and differences between paired plots determined. Total litterfall was observed at all sites but was only significant at the new infestation site. Reductions in leaf litter deposition in CG plots resulted in reduced N and C flux to the forest floor but soil C and N concentrations, and nitrogen mineralization rates, were not significantly different between CG and CC plots. Nitrate concentration in soil solution was significantly greater in CG plots compared to CC plots at the new infestation sites but showed the opposite trend at the old infestation sites. Herbaceous ground vegetation biomass was significantly greater (up to 10×) in CG plots than in CC plots. Overall, despite changes to riparian forest canopy structure and litterfall, there was no significant difference in soil nutrient cycling between EAB-induced canopy gaps and closed canopy plots after 10 years, suggesting a high resilience of riparian forest soils to EAB infestation