Effects Of Litter Research Articles

Achieving greater policy coherence and harmonisation for marine litter management in the North-East Atlantic and Wider Caribbean Region

The effects of marine litter pose ecological, economic and optional value threats to the countries and territories on the margins of the Atlantic Basin. As the abundance of transboundary marine litter increases, this in turn has triggered the development of marine litter policy action plans and inter-regional collaboration. The OSPAR Commission and Cartagena Convention of North-East Atlantic (NEA) and the Wider Caribbean Region (WCR) respectively, have established a memorandum of understanding to facilitate collaboration for enhanced marine litter management. In light of this development, this paper conducts a scoping review of management measures of marine litter within these regions as well as a coherence analysis between their regional action plans (RAPs). The analysis uses a proactive framework based on a modified categorization by Chen (2015) and Williams and Rangel-Buitrago (2019) for comparatively analyse management measures. The analytical categorizations include legislation and enforcement measures, prevention, removal, monitoring, research, information management and exchange and education and outreach. Although specific approaches differed among the regions depending upon geographical and individual situations, each categorization included detailed management activities except for prevention in NEA and removal in the WCR. The comparative analysis demonstrates that there are opportunities for inter-regional cooperation, knowledge sharing and overall enhanced and informed marine litter management.

Effect of mangrove leaf litter on shrimp (Penaeus monodon, Fabricius, 1798) growth and color

Color, texture and flavor are all important determinants of seafood product quality and value. For shrimp, Penaeus monodon, one of the highest-priced shrimp species of the South-East Asia shrimp industry, dark tiger-striped coloration is a key product quality criterion. We evaluated the effects of leaf litter of the mangrove species Avicennia officinalis (AO), Heritiera fomes (HF), Sonneratia apetala (SA) and S.caseolaris (SC) on length, weight and body color of shrimp (Penaeus monodon) post-larvae (PL). Fifteen-day-old PL (weight: 0.01 g) were reared in 1100-L fiber-reinforced polyethylene tanks. Five treatments having three replications were conducted for four weeks. Four treatments received leaf litter of the four mangrove species and supplemental feeds and one control treatment was provided with supplemental feed only (FO). The pH, biological oxygen demand (BOD5), chemical oxygen demand (COD) and phytoplankton and zooplankton biomass were lower, while total ammonia nitrogen (TAN) concentration were significantly higher in the FO treatment than in treatments including leaf litter. PL survival averaged 89% and only differed significantly between the SA and SC leaf litter treatments (p < 0.05). After 4 weeks of culture, larvae in the FO treatment had significantly shorter body and carapace length, lower body weight and a lower specific growth rate than larvae in the other treatments, while SA-reared larvae attained significantly greater length and weight than in the other leaf litter treatments. Shrimp body coloration and pattern with leaf litter treatments were significantly different from the FO treatment. SA-reared larvae at harvest were significantly darker in body color than larvae reared with other mangrove species. Shrimp value chain stakeholders preferred dark shrimp as an indicator of organic production and higher price. Mangrove leaf litter was found to enhance the production and color quality of black tiger shrimp and this technique can be applied in commercial shrimp aquaculture.

Growth Curves and Body Condition of Young Cats and Their Relation to Maternal Body Condition.

Simple SummaryThe aim of this study was to assess the effect of the litter, the individual and the mother on the likelihood that kittens become overweight by 8 months of age. Since efforts to investigate these factors in cats often do not account for variables that increase the likelihood of obesity in adult life (e.g., neutering), data on an intact cat family over 14 years were used. Both males and kittens (regardless of sex) from overweight mothers were more prone to being overweight at 8 months. A greater litter size appeared to protect kittens from becoming overweight, in contrast to a greater birthweight, which seemed to predispose them for it. The growth rate of all kittens differed according to their own (lean vs. overweight and male vs. female) and their mother’s (overweight vs. variable vs. lean) phenotype. In females but not in males, own and maternal phenotype affected the time to reach peak weight as well. Based on the results from this study, birthweight, growth rate and maternal overweight can indicate a predisposition of kittens to become overweight.The aim of the present study was to assess factors like litter, individual and maternal effects on kitten overweight at 8 months of age, defined as body condition score (BCS) ≥ 6, in an intact cat family. To minimize confounding, a homogenized cat population was used. After categorization of the life weight data according to the kittens’ sex, BCS and maternal non-pregnant phenotype (overweight (OM), lean (LM), variable (VM)), analyses including Pearson’s correlation coefficients, two-way ANOVA, linear, linear broken-line regression and repeated measures mixed model analyses were performed. Overweight and OM kittens gained weight most quickly, and females reached their peak weight earlier than males (6.2 ± 0.6 vs. 7.4 ± 0.2 months). In females but not in males the age to reach peak weight differed markedly according to category. Male (5.82 ± 0.09, p < 0.01) and OM kittens’ (5.80 ± 0.11, p = 0.07) BCS at 8 months was higher and they were heavier than their counterparts, from 3 and 5 months onwards, respectively. Litter size negatively correlated with overweight (r = −0.30, p < 0.01) and birthweight showed a positive correlation to live weight (R2 = 0.05, p = 0.05) and monthly weight gain (R2 = 0.18, p < 0.01) over time. This study supports routine monitoring of birthweight, growth rate and maternal phenotype prior to pregnancy to identify kittens at risk for becoming overweight.

Effects of Forest Harvesting Operations on the Recovery of Earthworms and Nematodes in the Hyrcanain Old-Growth Forest: Assessment, Mitigation, and Best Management Practice

The quality and performance of forest soil is closely related to the characteristics of the faunal community in the soil. Focusing on soil organisms can provide good indicators to choose the best soil restoration methods to improve the properties of degraded forest soils. Therefore, the present study aimed to evaluate the effects of the tree litter of different species on the recovery of soil organisms (earthworms and nematodes) from skid trails over a 20-year period after harvest operations. For this purpose, three skid trails with different ages after harvest operations (6, 10, and 20 years), considering three tree litter treatments (beech, beech–hornbeam, and mixed beech) and three traffic intensity classes (low, medium, and high), were identified. The combination of treatments was carried out in the forest with three replications, and a total of 18 sample plots of 0.5 m2 were harvested to measure earthworms and nematodes. The results showed that 20 years after harvest operations, the highest values of earthworm density (5.72 n m−2), earthworm biomass (97.18 mg m−2), and total nematodes (313.65 in 100 g of soil) were obtained in the mixed beech litter treatment compared to other litter treatments. With decreasing traffic intensity from high to low, the activity of soil organisms increased, and the highest values of earthworm density (5.46 n m−2), earthworm biomass (87.21 mg m−2), and soil nematodes (216.33 in 100 g soil) were associated with low traffic intensity. Additionally, in all three litter treatments and traffic intensities, the epigeic ecological species were more abundant than the anecic and endogeic species. Key soil variables including water content, porosity, available nutrients, pH, total organic C, and total N were significantly correlated with earthworm density and biomass and soil nematode population. Litter management and addition to compacted soil can support the functional dynamics and processes of the soil and maintenance of the abundances and activities of the soil fauna.

Stem density induces differential effects of litter on native and invasive plants

AbstractLitter plays an important role in plant invasion. Our previous studies have found that litter had two opposite effects as Spartina alterniflora invading native plant Phragmites australis community. Litter stimulated the growth of S. alterniflora on the edge of the community, while it inhibited the growth in the old community. Accordingly, we hypothesized that litter may play different roles in different stages of plant invasions. We selected three types of communities: P. australis monoculture (PAM), S. alterniflora monoculture (SAM), S. alterniflora–P. australis mixture (SPM) and conducted a comparative study by keeping and removing litter at Chongming Dongtan in the Yangtze River estuary, China. Our results revealed that litter removal significantly increased light intensity in SAM, and enhanced it in SPM, but had no significant influence on it in PAM. The effect of litter on light intensity resulted in a higher chlorophyll content and higher plant height of S. alterniflora monoculture after litter removal, which eventually led to a higher single weight and aboveground biomass for PAM and SAM after litter removal, and to a higher aboveground biomass for S. alterniflora in SPM. Litter removal significantly enhanced the dominance of S. alterniflora relative to P. australis in SPM. We concluded that the effects of invasive plants' litter on the invasion processes depend on the stem density of invasive plants relative to native plants. If an invasive species had a higher plant density, its litter may not have a shelter effect on native species, but could restrict its own growth.

Soil fungal and bacterial communities are altered by the incorporation of leaf litter containing a fungal endophyte

AbstractLitter decomposition plays a key role in nutrient cycling across ecosystems. The presence of Epichloë endophytes in grass plants affects litter decomposition. The overall effects of leaf litter containing Epichloë endophytes on the chemical and biological properties in non‐rhizosphere soils have not previously been examined. The current study is aimed to understand the effect of direct incorporation of leaf litter from Epichloë endophyte‐infected perennial ryegrass (Lolium perenne) on soil chemical characteristics, and fungal and bacterial biodiversity. Firstly, fresh leaf litter of the endophyte Epichloë festucae var. lolii‐infected (E+) and endophyte‐free (E−) L. perenne were incorporated into the soil, and then samples were collected from E+ and E− litter incorporated soil at T0, T1, T2 and T3 (0, 120, 240 and 360 days) for chemical and sequencing analyses. The Epichloë‐containing leaf litter incorporation changed the soil microbial environment by enhancing the soil organic carbon (SOC), total nitrogen (TN), total phosphorus, NH4+–N and NO3−–N contents, and acidifying soil pH. The endophyte had stronger effects on soil bacteria than soil fungi when the litter was determined with and without the endophyte. Litter containing the Epichloë endophyte significantly increased the absolute abundance of the 16S rRNA gene and relative abundances of the Actinobacteria, Nitrospirae and Gemmatimonadetes, while significantly decreasing the relative abundances of the Planctomycetes and Rokubacteria and the diversity in soil bacteria community. There was no significant effect of endophyte‐containing leaf litter incorporation on the absolute abundance and diversity of the soil fungal community except the increment in the relative abundance of Rozellomycota. Soil pH and the SOC‐to‐TN ratio (C:N) were the main factors influencing the soil bacterial community, and the presence of E. festucae var. lolii was directly and positively related to the soil bacterial diversity. The current study established that Epichloë endophyte‐infection altered the abundance and diversity of the soil bacterial community by affecting leaf litter quality and increasing soil chemical properties after litter incorporation.Highlights Soil microbial habitat was changed by leaf litter with Epichloë endophyte incorporation. Litter containing endophytes increased the absolute abundance of the 16S rRNA gene. Epichloë endophytes altered the diversity of bacteria during litter incorporation. The response of soil bacteria to a litter containing endophytes was greater than that of soil fungi.

Effects of forest litter on dissolved 137Cs concentrations in a highly contaminated mountain river in Fukushima

Study regionThe upper, forested reaches of the Ota River, 24.4 km northwest of the Fukushima Daiichi nuclear power plant, was studied. Study focusThere is concern about the effects of dissolved radiocesium (137Cs) released from forest litter on long-term contamination of aquatic ecosystems caused by the Fukushima nuclear accident. Therefore, hydrology and water quality measurements were performed under base flow and storm flow conditions in a high-dose-rate forest watershed in Fukushima Prefecture, to investigate the involvement of litter in 137Cs release. New hydrological insights for the regionUnder base flow conditions, the dissolved 137Cs activity concentration significantly positively correlated with the dissolved organic carbon and potassium ion concentrations (the main components leached from litter) over the entire study period. Differences in the annual variations in the 137Cs activity concentrations and potassium ion concentrations indicated that litter indirectly increased 137Cs concentrations in river water by releasing potassium ions that caused 137Cs to desorb from river sediment and riparian soil. In each large runoff event, the dissolved 137Cs activity concentration was higher at the time of maximum runoff than at the start of the event. The relationships between the dissolved 137Cs, dissolved organic carbon, and potassium ion concentrations strongly suggested that 137Cs leached from litter in runoff was directly responsible for the increase in the 137Cs activity concentration in river water.

Meta-Analysis of Effects of Forest Litter on Seedling Establishment

Litter plays an important role in seedling establishment (emergence, survival, and early growth). Here, we performed a meta-analysis on 404 datasets from 33 independent studies to analyze the effects of litter cover on seedling emergence, survival, height, and biomass (root, stem, leaf, and total). Each dataset was stratified according to experimental conditions, litter type (broadleaf versus needle litter), litter amount (thickness), and seed size. The results showed that litter cover had an overall negative effect on seedling emergence and survival, a neutral effect on root, leaf, total biomass, and a positive effect on stem biomass and seedling height than the no-litter cover control. Compared to thin (&lt;250 g m−2) and medium (250–500 g m−2) litter layers, thick litter (&gt;500 g m−2) was more detrimental for seedling emergence, survival, and total biomass, which could be an adaptation mechanism to prevent the growth of young seedling among high densities of other plants (trees). Broadleaf litter cover had a stronger negative effect on seedling emergence and total biomass than needle litter. Litter cover had a stronger negative effect on emergence of small seeds than on emergence of larger seeds. Similarly, litter cover had a stronger overall negative effect on seedling emergence than on seedling survival. In field and common garden experiments, litter effects were negative for emergence and positive for total biomass. In glasshouse and germination chamber experiments, litter effects were negative for emergence, survival and total biomass. These findings would contribute to advancements in forest management, improving conservation and restoration efforts.

Effects of Litter and Root Manipulations on Soil Bacterial and Fungal Community Structure and Function in a Schrenk's Spruce (Picea schrenkiana) Forest.

Soil microorganisms are the key driver of the geochemical cycle in forest ecosystem. Changes in litter and roots can affect soil microbial activities and nutrient cycling; however, the impact of this change on soil microbial community composition and function remain unclear. Here, we explored the effects of litter and root manipulations [control (CK), doubled litter input (DL), litter removal (NL), root exclusion (NR), and a combination of litter removal and root exclusion (NI)] on soil bacterial and fungal communities and functional groups during a 2-year field experiment, using illumina HiSeq sequencing coupled with the function prediction platform of PICRUSt and FUNGuild. Our results showed that litter and root removal decreased the diversity of soil bacteria and fungi (AEC, Shannon, and Chao1). The bacterial communities under different treatments were dominated by the phyla Proteobacteria, Acidobacteria, and Actinomycetes, and NL and NR reduced the relative abundance of the first two phyla. For the fungal communities, Basidiomycetes, Ascomycota, and Mortierellomycota were the dominant phyla. DL increased the relative abundance of Basidiomycetes, while NL and NR decreased the relative abundance of Ascomycota. We also found that litter and root manipulations altered the functional groups related to the metabolism of cofactors and vitamins, lipid metabolism, biosynthesis of other secondary metabolites, environmental adaptation, cell growth, and death. The functional groups including ectomycorrhizal, ectomycorrhizal-orchid mycorrhizal root-associated biotrophs and soil saprotrophs in the fungal community were also different among the different treatments. Soil organic carbon (SOC), pH, and soil water content are important factors driving changes in bacterial and fungal communities, respectively. Our results demonstrate that the changes in plant detritus altered the soil microbial community structure and function by affecting soil physicochemical factors, which provides important data for understanding the material cycle of forest ecosystems under global change.

Effects of soil conditioning, root and shoot litter addition interact to determine the intensity of plant–soil feedback

Plant–soil feedback (PSF) is recognized as an important mechanism shaping plant communities and determining plant abundance and coexistence. Under natural conditions, plants affect the outcome of plant–soil interactions simultaneously by conditioning the soil by living roots and by litter inputs into the soil. However, most experimental studies only focus on one of the pathways, which limits our understanding of PSF in the field.Here, we simultaneously explored the effect of soil conditioning by living roots and of root and shoot litter addition on the performance of seven Impatiens species grown in a two‐phase garden experiment.Soil conditioning negatively affected plant performance, which was at least partly explained by nutrient depletion. Root litter addition affected plant performance negatively and the results suggest that biotic effects such as pathogen transmission via the root litter played a role. The effects of root litter addition were more pronounced in control soil which, contrary to the conditioned soil, supposedly did not accumulate pathogens during the conditioning phase. Shoot litter addition increased soil nutrient levels, but had no impact on plant performance. However, presence of shoot litter aggravated the negative effects of root litter, probably due to increased amounts of nutrients available for soil biota and thus their faster growth and intensified effect on the plants.Overall, our study suggests that root and shoot litter have contrasting roles in plant–soil interactions and understanding their separate and interactive effects together with effects of soil conditioning is crucial for assessing the complexity of PSF.

Simulation research on PPP-RTK performance based on BDS GEO satellite

Precise point positioning (PPP) is one of the seven planning public services of the new generation global Beidou Navigation Satellite System (BDS), i.e. BDS-3. Up to now, the PPP service signal has already been broadcast through I channel of PPP-B2b to support decimeter level positioning within 30 min for users over China and the surrounding areas for free. Concerning the potential application of PPP real-time kinematic (PPP-RTK) in the BDS positioning service development, this paper carried out analysis and experiment of the design and evaluation of PPP-RTK through Q channel based on the existing PPP-B2b I channel signal. First, we presented the algorithm of PPP-RTK based on the undifferenced and uncombined model. Then, the format and broadcast strategy of phase delay and atmospheric delay products were discussed in detail. Finally, based on the simulation data, we analyzed the performance of PPP-RTK with different broadcast bandwidths. The results suggested that the positioning accuracy of GPS + BDS + Galileo PPP-RTK under 95% quantile were 2.3 cm and 3.3 cm in horizontal and vertical, respectively. In order to evaluate the BDS PPP-RTK service, we set the convergence thresholds as 6 cm in horizontal and 12 cm in vertical, which is given by Centimeter Level Augmentation Service of Japanese Quasi-Zenith Satellite System, and the time to converge to such thresholds were 0.5 min and 1.0 min in horizontal and vertical, respectively. Finally, the experiment considering ‘correction latency’ suggested that there was only a litter effect on the convergence speed, the positioning accuracy after convergence is roughly the same.

Effects of litter mass on throughfall partitioning in a Pinus tabulaeformis plantation on the Loess Plateau, China

Litter accumulates annually since vegetation is widely planted for afforestation. There is little information about the effects of litter on the reallocation of rainfall processes, although it plays an important role in hydrologic cycling. To examine the ecohydrological functions of litter under field experiments, eight runoff plots of four needle-leaf litter masses (0, 0.6, 1.2 and 1.8 kg/m2) were established in a Pinus tabulaeformis plantation on the Loess Plateau. Evaporation (E), surface runoff (R), infiltration and soil moisture dynamics in the 0–100 cm soil layer were measured throughout the rainy season in 2020. The results show that E decreased by 26.1–53.8% in litter-covered treatments compared with that without litter. Litter hindered heat and water exchange between soil and atmosphere, especially in 0–10 cm soil layer. R was effectively reduced by 71.1–90.5% with an increase in litter mass, and litter was more effective in controlling the R generation at higher rainfall intensities than at lower rainfall intensities. Litter hindered infiltration at the beginning of the rainy season but increased the soil water storage (SWS) with deeper infiltration in the long term. Both proportions of R and E to throughfall (P) decreased with increasing litter mass, and R/P was generally less than 10% in litter-covered treatments. SWS nonlinearly increased with an increase in litter mass, and more than half of the rainfall was stored, even in bare soil. Excessive litter (> 1.33 kg/m2) caused relatively less rainwater to be stored below the 100 cm soil layer or consumed by trees. This study may help to better understand the effects of litter on hydrological processes and can provide theoretical references for the proper management of plantations.

Litter diversity accelerates labile carbon but slows recalcitrant carbon decomposition

In biodiverse ecosystems, leaf litter of different plant species decomposes in mixtures, for which decomposition rates notoriously deviate from that expected from monospecific treatments. Despite important research efforts in past decades, these litter diversity effects remain difficult to predict. We hypothesized that this is due to a focus on bulk litter decomposition, while different carbon fractions constituting the litter may respond differently to litter diversity, thereby blurring the overall response. To test this hypothesis, we determined how the decomposition of (i) soluble compounds, (ii) cellulose, and (iii) lignin responded to litter mixing in a 3.5-year field experiment in an alpine forest. We found that the decomposition of soluble compounds and cellulose in mixtures was faster than expected from monospecific treatments, while that of lignin was slower. These deviations from expected decomposition rates of each litter carbon fraction were driven by different aspects of the litter functional diversity. This suggests that different mechanisms operating on distinct litter fractions lead to synergistic and antagonistic interactions that simultaneously affect bulk litter decomposition. Furthermore, the magnitude of these fraction-specific deviations from expected decomposition rates consistently decreased throughout decomposition. Considering the response of litter fractions and their temporality, rather than focusing on bulk litter thus seems critical to evaluate the response of decomposition to plant diversity and identify underlying mechanisms.

Shade drives plant community changes of ground‐layer savanna vegetation: Short‐term changes under an experimental approach

AbstractAimWoody‐plant encroachment is a reality in many savannas worldwide, leading savannas to become replaced by forest ecosystems. As tree density and cover increase, increased shade and litter deposition may suppress the savanna's community of low‐lying plants. By using field manipulation, we tested shading and litter effects, alone and in combination, on the savanna's ground‐layer plant community. We investigated how changes in these environmental factors may affect the composition, structure, and above‐ground biomass in the plant community of a species‐rich Neotropical savanna.LocationSavanna patches in the Cerrado, southeastern Brazil.MethodsAnnual surveys of the herbaceous–shrub layer in a three‐year field manipulation experiment examining shading and litter deposition.ResultsShade negatively affected all evaluated parameters, while litter addition had only minor effects. The largest losses of richness, density, and cover occurred in forbs and grasses. Increased shade resulted in a sharp decrease in the above‐ground biomass of monocots.ConclusionsOur results show that light is a strong environmental filter for the ground‐layer community. The reductions in grass cover and biomass under shade treatments likely altered ecosystem functioning. Woody encroachment can thus be considered to represent a process that can alter the structure and functioning of savannas. Management interventions should therefore be taken to prevent woody encroachment or mitigate its harmful effects on savanna biodiversity and ecosystem functioning.

Contribution of legume and non-legume trees to litter dynamics and C-N-P inputs in a secondary seasonally dry tropical forest

Many studies have investigated nutrient cycling in seasonally dry tropical forests, but few have assessed the contribution of different functional groups to these processes. Here, we investigated general litter dynamics patterns and the contribution of legume and non-legume trees to litter dynamics and carbon (C), nitrogen (N), and phosphorus (P) inputs in a fragment of secondary seasonally dry tropical forest after half a century of forest succession in the Atlantic Forest biome in Brazil. Between 2016 and 2017, we quantified litterfall production, canopy cover, forest floor, and soil C and N storage in 11 permanent plots distributed in the fragment. Vegetation identity and structure had been previously assessed. We quantified the seasonal inputs of leaf litter and C, N, and P separately for each functional group (legume and non-legume tree species). We also analyzed the correlations between the variables measured for each functional group with the variables measured at the plot level. Litter dynamics and nutrient input were affected by climate and functional group. Litterfall production during the two driest months was three times higher than during the other periods of the year, suggesting that species synchronicity is likely to minimize drought-related damage on trees. Legume trees had twice the basal area attained by non-legume trees, but while legumes were larger, non-legumes were more abundant and dominant in the smaller diameter class. Legumes deposited twice as much N during the driest period of the year as non-legumes. Although leaf litter, C, and P inputs by legumes were generally higher than those of non-legumes, these differences during the dry season were not statistically significant. We also found that the legume variables correlated better with the plot-level variables, compared to the non-legume functional group. Our results also indicated potential effects of the leaf litter and nutrient inputs by the legume functional group on the decomposition constant and, consequently, on the time of forest floor decomposition. Further studies should assess the role of different functional groups in litter dynamics and nutrient inputs in seasonally dry tropical forests.

Poultry Litter and Inorganic Fertilization: Effects on Biomass Yield, Metal and Nutrient Concentration of Three Mixed-Season Perennial Forages

Poultry litter and fertilizers are normally added as soil amendments. The effects of poultry litter and inorganic fertilizers on three mixed-season perennial forages were studied for two years in the field to understand growth dynamics, metals, and nutrient uptake. The primary objective was to investigate the heavy metal and nutrient concentrations, biomass yield and forage potential of a cool-season forage, stinging nettle (Urtica dioica L.), relative to warm-season forages, bermudagrass (Cynodon dactylon (L.) Pers.) and switchgrass (Panicum virgatum L.). Forage cuttings and soil samples were analyzed for heavy metals and nutrients using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Total biomass yield was higher by 66% and 50% in switchgrass and bermudagrass, respectively, compared with stinging nettle for the first year. While the warm-season forages yielded more biomass over the cool-season forage, metal concentrations were significantly higher for all elements in the cool-season forage. Stinging nettle showed greater macro-nutrient uptake with 103.20 kg ha−1, 0.87 kg ha−1, 27.49 kg ha−1 and 32.08 kg ha−1 for Ca, Fe, Mg, and P, except for K with 223.51 kg ha−1 compared with 267.29 kg ha−1 and 283.96 kg ha−1 for switchgrass and bermudagrass, respectively. Heavy metals were also higher in stinging nettle but were within the allowable limits for forages, indicating its potential as a resource for forages and nutrient cycling, particularly when double-cropped with warm-season forages.

Modelling the effects of above and belowground biomass pools on erosion dynamics

Despite the scientific consensus that vegetation modifies erosion/deposition processes, traditional erosion and landform evolution models often include a simplified representation of vegetation dynamics, which does not consider the influence of the various biomass pools on erosion mechanisms. In this paper, we present a new modelling framework that couples dynamic modules of hydrology, vegetation, biomass pools and landform evolution/erosion processes. We analyse the effect of above and belowground biomass pools (leaves, roots, litter and soil carbon) changes in erosion rates by considering: (1) the effect of root biomass on soil erodibility, (2) the effect of leaf cover on soil diffusivity, (3) the effect of litter on flow resistance, and (4) the effect of soil carbon on soil water retention. We implement the model using daily data for an open-forest vegetation and ran different idealized experiments for a period of 100 years. The objectives of the experiments are to understand the combined effects of biomass pool dynamics and climatic seasonality on erosion patterns, and to compare results including the effects of various biomass pools on erosion versus those obtained using simplified formulations (i.e., bare soil, constant vegetation). Our results indicate that the erosion protection effects of the individual biomass pools are not simultaneous, with different biomass pools providing protection at different times of the year. We also find that simplified vegetation formulations (e.g. constant vegetation) can significantly under/overestimate erosion when compared with the fully dynamic biomass pools formulation. These findings highlight the importance of including a detailed representation of dynamic vegetation and biomass pools in models, to capture the feedbacks between erosion and vegetation processes and better understand and predict erosion/deposition processes.

Undecomposed litter mixed in the soil can increase interrill erosion on hillslopes: A laboratory study

Soil-litter mixing has been found to affect soil erosion. However, previous studies did not distinguish the effects of litter exposed on the soil surface and that buried in the soil resulting from soil-litter mixing processes. This causes an unclear understanding of the effect of soil-litter mixing on soil erosion. In this research, we hypothesized that after mixing, the exposed litter would decrease soil erosion, while the litter buried in the soil would increase soil erosion. To test this hypothesis, soil boxes were filled with three treatments: soil-litter mixing with surface-exposed litter (CS), soil-litter mixing without surface-exposed litter (S), and soil surface cover (C) at four litter rates (0, 0.10, 0.20, and 0.35 kg m−2). Laboratory rainfall experiments were performed under a soil box slope of 10° and at a rainfall intensity of 80 mm h−1. The results of this study showed that the CS and C treatments reduced runoff velocity, and their velocities changed similarly depending on the surface cover of litter. However, in the S treatment, the litter rate increasedid not change runoff velocity significantly, indicating that runoff velocity was mostly controlled by the litter on the soil surface. Under the same surface cover, the C treatment reduced sediment yield by up to 39%; while the S treatment was found to increase sediment yield by up to 43% compared with the bare soil. The sediment yield of the CS treatment showed a decreasing trend as the litter rate increased. When the litter increased to 0.35 kg m−2, the sediment in CS treatment was 19% lower than in the bare soil. These results demonstrate a counteracting effect of surface litter and buried litter. The promoting effect of the buried litter on sediment yield was explained by the undecomposed litter creating an oversaturated condition and introducing a deforming force that decreased soil resistance to erosion. This study suggests that it is necessary to isolate the effect of exposed litter and buried litter on soil erosion, particularly in the early period after soil-litter mixing when litter is undecomposed.

Changes in soil faunal density and microbial community under altered litter input in forests and grasslands

Root and foliar litter inputs are the primary sources of carbon and nutrients for soil fauna and microorganisms, yet we still lack a quantitative assessment to evaluate the effects of root and foliar litter on various groups of soil organisms across terrestrial ecosystems. Here, we compiled 978 paired observations from 68 experimental sites to assess the directions and magnitudes of adding and removing foliar and root litter on the soil faunal density and microbial biomass that was evaluated by phospholipid fatty acids (PLFAs) across forests and grasslands worldwide. We found that litter addition had only a marginal effect on soil faunal density but significantly increased the soil total microbial-, fungal- and bacterial-PLFAs by 13%, 14%, and 10%, respectively, across ecosystems, suggesting that the soil microbial community is more sensitive to carbon source addition than soil fauna, particularly in soils with low carbon to nitrogen ratios. In contrast, removing litter significantly decreased the soil faunal density by 17% but had few effects on soil microorganisms. Compared with foliar litter, root litter input had a more positive effect on the development of soil fungal taxa. The effect of both litter addition and removal on soil faunal density and microbial biomass did not differ between humid and arid regions, but a greater influence was observed in grasslands than in forests for soil microbial community. Our results highlight that the increasing litter production under a global greening scenario would stimulate microbial activity in grasslands more than in forests, and this stimulation would be greater for soil microbes than soil fauna.

Allelopathic effect of parthenium weed (Parthenium hysterophorus L.) leaf litter on the seedling emergence and growth of wheat (Triticum aestivum L.)

Parthenium weed (Parthenium hysterophorus L) is a pantropical weed from Central America that has invaded more than 40 countries in the world. The invasiveness and competitive advantage of this weed are attributed to its ability to produce large number of seeds, tolerance to environmental stresses, climate change adaptability, and allelopathic properties. Phenolics and sesquiterpene lactones are two major classes of allelopathic compound produced by parthenium weed and these chemicals are known to have significant negative effect on germination, seedling emergence and growth of various plants species. The allelopathic properties of parthenium weed had been investigated in various past studies, however, most of the studies conducted the experiment under laboratory conditions with the allelopathic effect being tested by applying the aqueous extract of the weed directly on the test plants. This study aimed to examine the allelopathic effect of the leaf litter of parthenium weed under more natural conditions. Fresh leaves were oven dried and crushed to crude powder, hereafter referred to as leaf litter. The leaf litter were incorporated into the upper layer of the media of Greenfingers compost bark in pots. In to this were sown the seeds of the test plans then set to germinate. Another treatment without leaf litter was set up as a series of control. The treatments were arranged in simple randomized design in the glasshouse. After one week, any seedling produced were counted and thinned to five seedlings per pot. The plants produced from these seedlings were harvested after further 40 days of growth and the growth parameter including root length, shoot length, and dry weight were measured. The measurable growth reduction increased as the amount of parthenium weed leaf litter increased but variability between results existed. The uncontrollable factors and seasonal conditions may cause this variability, in addition to the seed quality. The chemicals contained within the parthenium weed leaf litter has been shown to affect crop growth presumably through allelopathic activity under natural field conditions.