Coniferous Leaf Litter Research Articles

Impact of nitrogen addition on single and mixed tree leaf litter decomposition depends on N forms in subtropical China

Increased nitrogen (N) inputs via atmospheric deposition are believed to influence leaf litter decomposition rate in forests. However, whether inorganic and organic N deposition produces a consistent influence on leaf litter decomposition is uncertain in forests, especially leaf litter mixtures. Using a fertilization experiment, we investigated the impact of inorganic (NH4Cl) and organic (urea and glycine) N on decomposition of single leaf litter (Liquidambar formosana, Pinus elliottii, Pinus massoniana, and Schima superba) and mixed broadleaf and coniferous (equal mass ratio) leaf litter using the litterbag method in a subtropical forest in southern China. Both inorganic and organic N addition increased mineral soil β-1,4-glucosidase, cellobiohydrolase, β-1,4-N-acetylglucosaminidase, L-leucine aminopeptidase, and acid phosphatase enzyme activities. During 780-day incubation, single litter decomposition was accelerated by NH4Cl addition but was not affected by either urea or glycine addition. Irrespective of added N forms, N addition shifted litter mixing effects on decomposition from synergistic effects to either additive or antagonistic effects. Accordingly, N addition generally decelerated litter mixture decomposition rates. Compared to coniferous litter, N addition-induced changes in litter mixing effects were often lower for broadleaf litter within the litter mixtures. These findings suggest that the impact of N enrichment on litter decomposition depends upon litter types and N forms, and highlight that N forms should be incorporated into assessing the consequence of atmospheric N deposition on the biogeochemical cycles in subtropical forests.

Distinct leaf litter drive the fungal communities in Panax ginseng-growing soil

Soil fungi communities play a vital role in the plant-soil ecosystem and affect plant growth and health, but the underlying mechanism controlling soil fungi communities in understory wild ginseng soil is still unknown. To study that mechanism, a pot culture experiment adding different leaf litters based on a completely randomized design was carried out. The results indicated that 1990 operational taxonomic units were obtained from eighteen samples. Ascomycota and Basidiomycota, the two dominant phyla, accounted for 84.57% of the total valid reads at the phylum level. The observed species and Chao 1 index in treatment E were significantly lower than those in the other treatments, although no significant differences were found among the Shannon index of all treatments (p > 0.05). Different types of leaf litter significantly changed the fungal community composition; specifically, Ascomycota was higher in broad leaf litter treatments (A, C, D and E) than in the coniferous leaf litter treatment (B), but Basidiomycota showed the opposite trend, indicating that Ascomycota and Basidiomycota could be used to identify the species of coniferous and broad leaves. The active biomarker fungal (Bmf), 36 different phylotypes, were identified by a linear discriminant analysis effect size algorithm in all treatments, and some Bmf may participate in the decomposition of different tree litters. Additionally, the changes in fungal community diversity and composition were closely related to the changes in soil microbial biomass carbon, total nitrogen and available phosphorus in all treatment soils. Overall, our study indicated that leaf litter changed the soil fungal community structure, and some Bmf were directly involved in leaf litter decomposition. Bmf is more indicative and helpful for distinguishing leaf species.

The Effects of Plant Secondary Metabolites from Coniferous Needle Leaf Litter on the Leaf Litter Decomposition of Betula albo-sinensis Burk

In this study, leaf litters of Betula albo-sinensis and 5 coniferous species were used as samples. The B. albo-sinensis leaf litter was buried in soil and termly treated with the water extracts of five types of coniferous leaf litter for a 6-month simulation decomposition experiment. The dynamics of mass loss and nutrients (C, N, P, and K) content of leaf litter and the soil enzymatic activities were measured to investigate the effects of plant secondary metabolites (PSM) from coniferous leaf litters on the decomposition processes of B. albo-sinensis leaf litter. The results indicated that the extracts of Pinus tabuliformis, Platycladus orientalis, P. armandii and Larix principis-rupprechtii leaf litters significantly inhibited the whole decomposition process and overall nutrients release of B. albo-sinensis leaf litter, while the extracts of Picea asperata leaf litter exhibited no significant influence. The general suppression of PSM on the soil sucrase, carboxymethyl cellulase and β-glucosidase activities might be the main reason leading to the inhibitory effects of the extracts of P. tabuliformis, P. orientalis, P. armandii and L. principis-rupprechtii leaf litter. The species causing inhibitory effects, especially L. principis-rupprechtii, was not recommended to be planted mixed with B. albo-sinensis, or their planting density should be lower in the mixed forests.

Effects of different leaf litters on the physicochemical properties and bacterial communities in Panax ginseng-growing soil

Leaf litters play a very significant role in determining soil physicochemical properties and shaping soil microbial communities in forest ecosystems, but their impact on understory wild ginseng soil is unknown. In order to study that, different leaf litters from five tree species ((A) Acer mono. Maxim. var. mono; (B) Pinus densiflora Sieb. et Zucc.; (C) Juglans mandshurica Maxim.; (D) Tilia amurensis Rupr.; (E) Quercus mongolica Fisch. ex Ledeb) were added to Panax ginseng-growing soil. Our results indicated that the physicochemical properties of soil were significantly affected by all the leaf litter treatments. Soil total nitrogen, available NPK, and soil microbial biomass (carbon and nitrogen) significantly (P<0.05) increased across all treatments. In addition, we found that the soil bulk density and C/N ratio was lower following all treatments than in the control (no addition of leaf litter). Although the different kinds of added leaf litter had few effects on bacterial diversity and abundance, significant changes in the bacterial community composition could be identified in all soils; specifically, the relative abundance of Proteobacteria was higher in treatments than in the control. In addition, the bacterial communities of Bacteroidetes were fewer in treatments with coniferous leaf litter than those with broad leaf litter (P<0.05). Canonical discriminant analysis (CDA) ascertained that the shift of bacterial community composition and diversity were closely related with the changes in soil microbial biomass carbon and available nitrogen in all treatment soils. Our experiment results suggest that addition of leaf litter has a significant impact on soil bacterial community development, and it can lead to higher soil nutrients and soil microbial biomass, as well as a different bacterial community composition.

The effect of temperature and moisture on trace gas emissions from deciduous and coniferous leaf litter

AbstractThe forest litter layer lies at the boundary between soil and atmosphere and is a major factor in biogeochemical cycles. While there are several studies on how the litter layer controls soil trace gas emissions, litter emissions itself are less well understood, and it is still unclear how important gases respond to changing temperature and moisture. In order to assess leaf litter gas exchange, we conducted laboratory incubation experiments in which the full set of climate relevant gases, i.e., carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and nitric oxide (NO) coming from deciduous and coniferous leaf litter were measured at five temperatures and seven moisture contents. In addition, we compared litter and soil from different origin in terms of temperature/moisture responses of gas fluxes and investigated possible interactions between the two climate factors. Deciduous litter emitted more CO2 (up to 335 mg CO2‐C kg−1 h−1) than coniferous litter, whereas coniferous litter released maximum amounts of NO (207 µg NO‐N kg−1 h−1). N2O was only emitted from litter under very moist and warm conditions (&gt;70% wet weight, &gt;10°C). CH4 emissions were close to zero. Temperature sensitivities of litter emissions were generally lower than for soil emissions. Nevertheless, wet and warm conditions always enhanced litter emissions, suggesting a strong feedback effect of the litter layer to predicted future climate change.

Conflicting effects of microhabitats on Long-toed Salamander (Ambystomamacrodactylum) movement: implications for landscape connectivity

Understanding dispersal requires multiple lines of investigation, from the study of broad patterns of population connectivity to the identification of factors impacting movement at local scales. To determine the potential effects of different microhabitats on dispersal in the Long-toed Salamander (Ambystoma macrodactylum Baird, 1850), we experimentally evaluated mobility, moisture loss, and habitat choice in response to five common substrates (deciduous and coniferous leaf litter, grass, moss, and sand). Specifically, we examined differences in the efficiency with which salamanders moved across substrates when motivated to move. We then quantified moisture loss in each substrate and evaluated habitat preference. Our results point to a trade-off between substrates that are easily traversed and those that offer high protection against desiccation. Habitat choice appeared to balance these two aspects of performance, with salamanders favouring a substrate that offered both low resistance to movement and high protection against desiccation. This result was context-dependent, as preferences shifted towards wetter but less easily traversed substrates when supplemental cover objects were made available. Overall, our study highlights the potential for individuals to respond to a given substrate in ways that can both facilitate and limit dispersal and thus underscores the need to consider different aspects of individual performance and behaviour when studying population connectivity.

Wildfire severity mediates fluxes of plant material and terrestrial invertebrates to mountain streams

Wildfire effects upon riparian plant community structure, composition, and distribution may strongly influence the dynamic relationships between riparian vegetation and stream ecosystems. However, few studies have examined the influence of fire on these processes. To that end, we compared the quantity and composition of allochthonous inputs of plant material and terrestrial invertebrates among stream tributaries characterized by various degrees of burn severity 5years post-fire in the Frank Church Wilderness of central Idaho, USA. The magnitude of inputs of coniferous leaf litter to unburned stream reaches was five times that of inputs to severely burned reaches. Deciduous leaf litter inputs to unburned reaches were 1.5 times, and inputs of terrestrial invertebrates were twice, the magnitude of inputs to severely burned reaches. NMS ordination and MRPP analysis indicated that the taxonomic composition of terrestrial invertebrate inputs to unburned stream reaches was significantly different than the composition of invertebrate inputs to either high-severity or low-severity reaches (A=0.057,p=0.040). Unburned and low-severity stream reaches received greater inputs of large-bodied invertebrates belonging to the orders Hymenoptera, Lepidoptera, Orthoptera, and Diptera. Taken as a whole, our results indicate that fire can significantly alter terrestrial–aquatic connectivity via alterations in riparian-to-stream inputs of leaf material and arthropods. Given these findings, wildfire severity might be expected to be a critical factor in shaping stream–riparian food webs in fire-prone areas.

Methyl bromide emissions to the atmosphere from temperate woodland ecosystems

AbstractThe environmental importance of methyl bromide (CH3Br) arises from its contribution to stratospheric ozone loss processes and, as a consequence, its emissions from anthropogenic sources are subject to the Montreal Protocol. A better understanding of the natural budget of CH3Br is required for assessing the benefit of anthropogenic emission reductions and for understanding any potential effects of environmental change on global CH3Br concentrations. Measurements of CH3Br flux in temperate woodland ecosystems, in particular, are very sparse, yet these cover a large fraction of terrestrial land surface. Results presented here from 18 months of field measurements of CH3Br fluxes in four static flux chambers in a woodland in Scotland and from enclosures of rotting wood and deciduous and coniferous leaf litter suggest net emissions from temperate woodlands. Net CH3Br fluxes in the woodland varied between the chambers, fluctuating between net uptake and net emissions (−73 to 279 ng m−2 h−1 across 161 individual measurements), and with no strong seasonality, but with time‐averaged net emission overall [27±57 (1 SD)] ng m−2 h−1]. This work demonstrates that scale‐up needs to be based on sufficient individual measurements to provide a reasonably constrained estimate of the long‐term mean. Mean (±1 SD) net CH3Br emissions from deciduous and coniferous leaf litter were 43 (±33) ng kg−1 (dry weight) h−1 and 80 (±37) ng kg−1 (dry weight) h−1, respectively, and ∼1–2 ng kg−1 (fresh weight) h−1 from rotting woody litter. Despite the intrinsic variability, data obtained here consistently point to the conclusion that the temperate forest soil/litter ecosystem is a net source of CH3Br to the atmosphere.

Conservation management implications of substrate choice in recently metamorphosed American toads (Bufo americanus)

We experimentally examined the choice of three substrate types by American toad (Bufo americanus) metamorphs. Metamorphs clearly preferred deciduous leaf litter over coniferous leaf litter and bare soil, and coniferous leaf litter over bare soil. These results emphasize that modification of terrestrial habitats surrounding breeding ponds can impact anuran behavior and populations.

Limnological characteristics of 56 lakes in the Central Canadian Arctic Treeline Region

Measured environmental variables from 56 lakes across the Central Canadian Treeline Region exhibited clear limnological differences among subpolar ecozones, reflecting strong latitudinal changes in biome characteristics (e.g. vegetation, permafrost, climate). Principal Components Analysis (PCA) clearly separated forested sites from tundra sites based on distinct differences in limnological characteristics. Increases in major ions and related variables (e.g. dissolved inorganic carbon, DIC) were higher in boreal forest sites in comparison to arctic tundra sites. The higher values recorded in the boreal forest lakes may be indirectly related to differences in climatic factors in these zones, such as the degree of permafrost development, higher precipitation and runoff, duration of ice-cover on the lakes, and thicker and better soil development. Similar to trends observed in DIC, substantially higher values for dissolved organic carbon (DOC) were measured in boreal forest lakes than in arctic tundra lakes. This was likely due to higher amounts of catchment-derived DOC entering the lakes from coniferous leaf litter sources. Relative to arctic tundra lakes, boreal forest lakes had higher nutrient concentrations, particularly total nitrogen (TN), likely due to warmer conditions, a longer growing season, and higher precipitation, which would enhance nutrient cycling and primary productivity. Results suggest that modern aquatic environments at opposite sides of the central Canadian arctic treeline (i.e. boreal forest and arctic tundra) exhibit distinct differences in water chemistry and physical conditions. These limnological trends may provide important information on possible future changes with additional warming.

Residence time and decomposition rate of Pinus pinaster needles in a forest floor from direct field measurements under a Mediterranean climate

Pinus pinaster (Soland) litter was sampled from a Mediterranean forest floor in order to study decomposition kinetics under natural conditions. Needles were divided into five distinct and successive compartments L, F1a, F1b, F2a, F2b, according to their morphology. The methods of Kendrick (Kendrick, W.B., 1959. The time factor in the decomposition of Coniferous leaf litter. Canadian Journal of Botany 37, 907–912) and Gourbière, (Gourbière, F., 1981. Vie, sénescence et décomposition des aiguilles de sapin ( Abies alba Mill.) Part I: Méthodologie et premiers résultats. Acta oecologica, Oecologica Plantarum 2, 223–232) were used to determine the mass loss of each compartment. On the forest floor, the total needle compartment represented 39% of the total decomposing litter mass and the five distinct compartments had similar mass values of 2.8–3.1 t ha −1 ash-free material. The decomposition rate of each compartment was calculated from the mass compartment, its mass loss and the litter-fall in the site. The remaining mass in relation to calculated time was described by a single first-order decay model with a decomposition rate ( k) of 0.135 year −1 ( R 2=0.86 ) or by an asymptotic model with k=0.180 year −1 and the asymptote at 83.2% R 2=0.87 . The first-year mass loss equalled 13%, and after 5.1 years it reached 50% for both models.

Route Choice by Deer Mice (Peromyscus maniculatus): Reducing the Risk of Auditory Detection by Predators

Abstract The influence of predation risk on microhabitat selection in male adult deer mice (Peromyscus maniculatus) was examined using an enclosure experiment. The relative amount of time spent by the deer mice on coniferous leaf litter, hardwood leaf litter and logs was measured. Mice preferred dry coniferous litter over dry hardwood litter, but had no preference when both litter types were wet. Deer mice traveled more along logs placed on hardwood litter than on coniferous litter. Nocturnal mammalian and avian predators of deer mice often use sound to locate their prey, and mice rustling in hardwood leaf litter should be more easily detected. Therefore, deer mice restrict their movements to routes that reduce the risk of auditory detection by predators.

Effects of SO 2 and O 3 on the chemistry and fda activity of coniferous leaf litter in an open air fumigation experiment

An open-air fumigation facility, developed for continuous fumigation of young conifers by SO 2 and O 3, was used for experimental exposure of decomposing coniferous leaf material. There were no treatment effects on the rates of mass loss from litter for exposure periods from 6 wk to 44 months. Sulphur dioxide treatment consistently increased the rate of removal of base cations from the litter, with the order of sensitivity of cations to SO 2-induced leaching being Mg > Ca > K > Na. The pH of naturally fallen Scots pine needles was reduced by 0.5 units in the high SO 2 treatments. Fluorescein diacetate (FDA) activity and rates of mass loss of naturally-fallen needles were lower in SO 2 fumigated plots than ambient controls. Transplantation experiments showed that the depression in decomposer activity was caused by exposure of needles to SO 2 while still green. Ozone fumigation exerted no effects on the chemical composition of litter, and an O 3-related increase in FDA activity in one season was attributed to enhanced nitrogen input due to N 2O 5 contamination.

Allelopathic Potential of Coniferous Species to Old-Field Weeds in Eastern Quebec

Abstract Phytotoxicity of Abies balsamea (L.) Mill., Picea mariana (Mill.) BSP., Pinus resinosa Ait., Pinus divaricata (Ait.) Dumont, and Thuya occidentalis L. fresh leaf and leaf litter leachates were evaluated on the germination and growth of four weed species: Phleum pratense L., Poa pratensis L., Agropyron repens (L.) Beauv., and Epilobium angustifolium L. Three dilutions of leachates were used for the germination tests. Germination of all weed species was inhibited in proportion to the dilutions used. Fresh leaf leachates of A. balsamea and P. resinosa were most inhibitory to germination. P. pratense was usually less affected by the treatments than were the other three species. Germination or E. angustifolium and P. pratensis was delayed by the different solutions; germination of P. pratense was delayed only by fresh leaf leachates of A. balsamea and P. divaricata. Height growth and root elongation of A. repens, P. pratensis and P. pratense were inhibited by most extracts. P. mariana leaf leachates were the most inhibitory to height growth and root elongation. All seedlings treated with P. mariana leaf leachates exhibited severe root necroses which affected normal root development. Laboratory experiments suggested that allelopathic weed control, using coniferous leaf litter or fresh leaves, could aid in reforestation of abandoned fields by reducing undesirable competition. Forest Sci. 32:112-118.

Temperature and moisture dependence of decomposition rates of hardwood and coniferous leaf litter

Samples of fresh (autumn) and of year-old (late summer) deciduous forest-leaf litter and humus, and of Douglas fir fine litter and humus, were wetted to known moisture content, nominally between 200 and 40% water (dry basis), and maintained at constant temperatures between 10° and 40°C. Rates of CO 2 production were measured by KOH absorption and titration. Decomposition rate was found to be a linear function of log — (water potential), and to approach a maximum near 40°C. The temperature-dependence was consistent with models based on irreversible heat inactivation of a rate-controlling enzyme, also with Eyring's “absolute reaction rate” theory for reactions controlled by a reversibly inactivated enzyme. Activation energies were 66.8–67.3 kJ mol −1 for litter, and 61.4–67.5 kJ mol −1 for humus decomposition; for enzyme inactivation energies were 150–154 kJ mol −1.

Ecology of nematophagous fungi: distribution and habitat

SUMMARYA survey of 161 samples of soil and plant material collected from sites throughout Ireland has shown that nematophagous fungi exist in a wide range of habitats. 205 isolations were made consisting of 11 endoparasitic and 20 predatory species. The commonest endoparasites and their frequency of occurrence were Myzocytium spp. (9·3%), Acrostalagmus obovatus (6·8%) and Harposporium anguillulae (6·2%). Predators were equally abundant, the commonest being Dactylella bembicodes (8·7%), D. mammillata (6·8%) and D. ellipsospora (6·2%). Arthrobotrys oligospora and A. musiformis both had a highly restricted distribution. Adhesive knobs and constricting rings were significantly more abundant than the other trapping mechanisms.All the samples were classified into one of 10 broad habitat types. Of these temporary agricultural pasture, coastal vegetation and coniferous leaf litter had the greatest percentage of sites from which nematophagous fungi were isolated. A number of species showed distinct habitat associations, in particular Arthrobotrys robusta, A. musiformis and Dactylella cionopaga.

Enzymatic Activities in Coniferous Leaf Litter

AbstractAssays for measuring the activities of cellulase, xylanase, mannase, amylase, β‐glucosidase, invertase, and protease employing buffered suspensions of ground coniferous and deciduous leaf litter exhibited zero‐order kinetics. Only a small percentage of the whole‐litter activities of invertase (3%), β‐glucosidase (3%), and protease (1%) were extractable into 0.05M potassium acetate, pH 5.0; however, extractable activities of cellulase and xylanase represented from 39 to 174% of the whole‐litter activities indicating their soluble exocellular nature. Extractable protease and amylase activities were best correlated (r=0.65 and 0.65, respectively) with the average daily rates of CO2 evolution in a group of 90 leaf litter samples equally representing 18 coniferous species. Enzymatic activities were readily detectable in extracts of all samples but classification of the samples by species provided little differentiation in the distribution of either enzymatic activities or rates of CO2 evolution. Mannase, cellulase, and xylanase activities were well‐correlated with each other (r=0.88) in all samples. Assays at‐tempting to measure a pool of readily‐metabolizable substances in litter by extractable reducing substances, ninhydrin‐positive substances, glucose, and phenolics failed to show correlation coefficients &gt; 0.41 with rates of CO2 evolution. Addition of D‐(+)‐catechin to litter extracts, up to levels equivalent to those observed in the group of samples, did not inhibit any carbohydrase thus suggesting the lack of inhibition of litter‐decomposing enzymes by the concentrations of phenolics present in these coniferous leaf litters.

Detergent and ethanol extraction as an index of decomposition of coniferous leaf litter

Detergent and ethanol extraction as an index of decomposition of coniferous leaf litter

Enzymatic Activities Related to the Decomposition of Coniferous Leaf Litter

AbstractThe rate of CO2 evolution at 23°C and 75% moisture content for a diverse group of coniferous leaf litter samples from Oregon was measured. Significant correlations (1% level) were observed between the rate of CO2 evolution and the activity of amylase, cellulase, and xylanase (r = 0.71, 0.58, and 0.44, respectively) in 0.05M potassium acetate, pH 5.0 extracts of the litter. The amounts of extractable hexose, phenolics, and reducing substances were also correlated with the rate of CO2 evolution (r = 0.74, 0.53, and 0.73 respectively). Peroxidase and invertase activities were not correlated with the rate of CO2 evolution. Litter extracts showed zero‐order kinetics for the hydrolysis of carboxymethylcellulose, xylan, starch, and sucrose. All carbohydrase activities were destroyed by a 15 min exposure to a boiling water bath.

Untersuchungen über das Vorkommen und die Wirkung von biogenen Wachstumsregulatoren in wäßrigen Nadelstreuauszügen

Leachates from coniferous leaf litter prepared under laboratory conditions contained basic and acidic ethyl acetate-soluble growth regulating factors, including growth inhibitors and compounds showing gibberellin-like activity. The dynamic of the release of leachates from needle litter when percolated with tap water and the effect of substances leached on test plants were studied. By means of PC combined with the lettuce biotest the active substances could be distinguished. The substances showing gibberellin-like activity appeared on the paper chromatogramms run with isopropanol, ammonia, water (IAW 10 :1 :1 v/v/v) at Rf to and to depending on the needle litter concerned. According to other investigators it could be shown that polyhydroxyphenols are present in the leachates of coniferous leaf litter. These are the agents implicated in an inhibitory role.