Pine Litter Research Articles

A litter-slurry technique elucidates the key role of enzyme production and microbial dynamics in temperature sensitivity of organic matter decomposition

The rate at which organic matter decomposes generally increases with temperature, unless it is physico-chemically protected from enzymatic depolymerization. The temperature sensitivity of decomposition should increase with decreasing reaction rates, corresponding to increasing activation energy of the decomposing compounds. One approach to testing this carbon-quality temperature hypothesis is to study the effect of temperature on leaf litter decomposition, because fresh surface litter is unprotected. However, other factors such as humidity co-vary with temperature, and biological processes such as enzyme production and microbial population growth may also be thermally sensitive. We developed a litter slurry approach to isolate the effect of temperature and litter quality on decomposition. We found that pine litter decomposed faster than oak litter, consistent with a lower C:N and lignin:N ratio. During the first 14 days of decomposition, there was no difference in decomposition rate for litter incubated at 25 °C compared to 35 °C. Lower potential enzyme activity at 35 °C suggested that enzyme production was suppressed at 35 °C compared to 25 °C, resulting in similar in situ enzyme activities at the two temperatures. After 14 days, enzyme pools were similar between the two incubation temperatures, which resulted in faster decomposition at the warmer temperature, consistent with enzyme kinetic theory. At Day 14, the decomposition rate of the high quality pine litter was more temperature sensitive than the decomposition rate of the lower quality oak litter, suggesting that the quality of soluble pool rather than bulk chemistry determined the temperature sensitivity during this stage. After 28 days of incubation, oak litter decomposition was more temperature sensitive than pine litter, consistent with the carbon temperature-quality hypothesis. The litter slurry approach revealed that biological responses to temperature can affect the apparent temperature sensitivity of decomposition, and highlight a need for further research into microbial responses to temperature.

Dynamics of fungal diversity in different phases of Pinus litter degradation revealed through denaturing gradient gel electrophoresis (DGGE) coupled with morphological examination

Fungal diversity in Pinus sylvestris var. mongolica litter was investigated by PCR-DGGE coupled with a traditional cultivation method. Twenty-one fungal strains were isolated by traditional cultivation methodology, most being filamentous fungi. Total DNA was extracted directly from the L, F1, F2 and H litter layers respectively using the bead-beating method. About 460 bp rDNA fragments were obtained by Nested-PCR and analyzed by denaturing gradient gel electrophoresis (DGGE). PCR-DGGE analysis recovered seven operational taxonomic units (OTUs) from the different decomposing litter layers. Six OTUs belonged to Ascomycetes and one to Basidiomycota. Sporobolomyces inositophilus was revealed by both methods, but there was no overlap in other species detected. A major shift of fungal communities on litter occurred during decomposition. The Shannon-Weaver index, which measures diversity in categorical data, was maximal in the F1 layer, then decreased with substratum degradation and reached it lowest value in the H layer. Key words: Fungal diversity, polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE), Traditional culture, Litter.

Long-Term Monitoring of Scots Pine Litter Decomposition Rates Throughout Sweden Indicates Formation of a More Recalcitrant Litter in the South

Decomposition studies were carried out at sites throughout Sweden, including the four Integrated Monitoring sites. Scots pine needle litterbag weight loss measurements over 3 or 5 years were determined at 26 sites and repeated up to 27 times, depending on the site. Humus layer respiration rates were determined for 20 sites in 1987-1989 and repeated in 2007-2008. Partial Least Squares (PLS) regression was used to elucidate the relative importance of climatic and soil factors. Annual needle weight losses decreased only slowly (20-10%) over 3-5 years for all northern (>60°N) sites but decreased sharply from 30 to 10% in the third year in southern (<60°N) sites. Respiration rates of southern sites were less (40% on average) than those of northern sites. Humus layer N was positively correlated to needle weight loss during the first and the second years, but negatively correlated in the third year and to respiration rates. The results indicated that litter formed in southern Sweden became more recalcitrant in later stages of decomposition compared to litter produced in northern Sweden.

Entrainment regimes and flame characteristics of wildland fires

This paper reports results from a study of the flame characteristics of 22 wind-aided pine litter fires in a laboratory wind tunnel and 32 field fires in southern rough and litter–grass fuels. Flame characteristic and fire behaviour data from these fires, simple theoretical flame models and regression techniques are used to determine whether the data support the derived models. When the data do not support the models, alternative models are developed. The experimental fires are used to evaluate entrainment constants and air/fuel mass ratios in the model equations. Both the models and the experimental data are consistent with recently reported computational fluid dynamics simulations that suggest the existence of buoyancy- and convection-controlled regimes of fire behaviour. The results also suggest these regimes are delimited by a critical value of Byram’s convection number. Flame heights and air/fuel ratios behave similarly in the laboratory and field, but flame tilt angle relationships differ.

Some indices of biological cycle of 137Cs and 39K in forest ecosystems of Bryansk woodland in the remote period after chernobyl fallouts

The features of the biological cycle of 137Cs and 39K in the remote period after Chernobyl fallouts are considered on the example of forest ecosystems of Bryansk woodland. It is demonstrated that the maximum amount of 137Cs in the total phytomass is concentrated in wood, the minimum amount of 137Cs, in the external bark layers; for the annual production, in assimilating organs and the external bark layers, respectively. The distribution of 39K in the total phytomass and the annual production is almost identical to that of 137Cs. The arrival of 137Cs to the soil with litter in pine and birch forests has recently been equal approximately to 50% of the capacity of the biological cycle. It mostly arrives with the assimilating organs (needles and leaves). In pine forests the return of 39K into the soil with litter is closest to that observed for 137Cs.

Reactivity of Litter Leachates from California Oak Woodlands in the Formation of Disinfection By‐Products

Litter materials from forested watersheds can be a significant source of dissolved organic matter (DOM) to surface waters that can contribute to the formation of carcinogenic disinfection by-products (DBPs) during drinking-water chlorination. This study characterized the reactivity of DOM from litter leachates of representative vegetation in oak woodlands, a major plant community in the Foothill Region of California. Leachates from fresh and decomposed litter (duff) from two oak species, pine, and annual grasses were collected for an entire rainy season to evaluate their reactivity to form DBPs on chlorination. Relationships among specific ultraviolet absorbance (SΔUVA), fluorescence index (FI), specific differential ultraviolet absorbance (SΔUVA), specific chlorine demand (SCD), and the dissolved organic carbon:dissolved organic nitrogen (DOC:DON) ratio to the specific DBP formation potential (SDBP-FP) were examined. The DOM derived from litter materials had considerable reactivity in forming trihalomethanes (THMs) (1.80-3.49 mmol mol), haloacetic acid (HAAs) (1.62-2.76 mmol mol(-1)), haloacetonitriles (HANs) (0.12-0.37 mmol mol(-1)), and chloral hydrate (CHD) (0.16-0.28 mmol mol). These values are comparable to other identified watershed sources of DBP precursors reported for the California Delta, such as wetlands and organic soils. Vegetation type and litter decomposition stage (fresh litter versus 1-5 yr-old duff) were key factors that determined characteristics of DOM and their reactivity to form DBPs. Pine litter had significantly lower specific THM formation potential compared with oak and grass, and decomposed duff had a greater DON content, which is a precursor of HANs and other nitrogenous DBPs. The SΔUVA and SDBP-FP were temporally variable and dependent on vegetation type, degree of decomposition, and environmental conditions. Among the optical properties of DOM, SΔUVA was the only parameter that was consistently correlated with SDBP-FP.

Early spring mycobiota of pine litter needles.

Early spring mycobiota of pine litter needles.

A study of lignin degradation in leaf and needle litter using 13C-labelled tetramethylammonium hydroxide (TMAH) thermochemolysis: Comparison with CuO oxidation and van Soest methods

We studied the degradation of lignin in leaf and needle litter of ash, beech, maple, pine and spruce using 13C-labelled tetramethylammonium hydroxide ( 13C TMAH) thermochemolysis. Samples were allowed to decompose for 27 months in litter bags at a German spruce forest site, resulting in a range of mass loss from 26% (beech) to 58% (ash). In contrast to conventional unlabelled TMAH thermochemolysis, 13C-labelling allows thermochemolysis products from lignin, demethylated lignin and other polyphenolic litter compounds (e.g. tannins) to be distinguished. Proxies for lignin degradation (phenol yield; acid/aldehyde ratio of products) changed considerably upon correction for the contribution of non-lignin sources to the thermochemolysis products. Using the corrected values, we found increasing acid/aldehyde values as well as decreasing or constant yield of lignin derived phenols normalised to litter carbon, suggesting pronounced lignin degradation by wood-rotting fungi. No indication for build up of demethylated lignin through the action of brown rot fungi on ring methoxyls was found. The results were compared with those of other analytical techniques applied in previous studies. Like 13C-TMAH thermochemolysis, CuO oxidation showed increasing lignin oxidation (acid/aldehyde ratio) and no/little enrichment of lignin derived phenols in the litter. Molecular lignin degradation patterns did not match those from analysis of total acid unhydrolysable residues (AURs). In particular, the long assumed selective preservation of lignin during the first months of litter decomposition, based on AUR analysis, was not supported by results from the CuO and 13C TMAH methods.

Identification of various laccases induced by anthracene and contribution to its degradation in a Mediterranean coastal pine litter

Mediterranean coastal ecosystems are known to be highly subject to natural and anthropic environmental stress. In this study, we examine the effects of anthracene as a common pollutant on the total microbial communities from a Pinus halepensis litter of a typical Mediterranean coastal site (Les Calanques, Marseille). The main objective was to identify the microbial factors leading the resilience of this ecosystem. Two questions were addressed: (i) how lignin-degrading enzymes (Laccase, Lignin–peroxidase and Mn–peroxidase) are affected by the presence of this molecule, (ii) whether the indigenous consortia are involved in its degradation in mesocosms under favorable incubation conditions (25 °C, 60% WHC) and after different time intervals (1 and 3 month(s)). We found a strong increase in laccase production in the presence of anthracene after 3 months, together with anthracene degradation (28% ± 5). Moreover 9,10-anthraquinone is detected as the product of anthracene oxidation after 3 months. However neither lignin–peroxidase activity nor Mn–peroxidase activity is detected. Laccase proteins directly extracted from litter were sequenced via Nano-LC–MS/MS and reveal twelve different peptide sequences induced by the presence of anthracene in the mesocoms. Our study confirms the major detoxification role of this enzymatic system and highlights the high degradation potential of fungal species inhabiting P. halepensis litter, a factor in the resilience of Mediterranean ecosystems.

Relative contribution of foliar and fine root pine litter to the molecular composition of soil organic matter after in situ degradation

The influence of litter quality on soil organic matter (SOM) stabilization rate and pathways remains unclear. We used 13C/ 15N labeled litter addition and Curie-point pyrolysis gas chromatography–mass spectrometry combustion-isotope ratio mass spectrometry (Py–GC–MS–C–IRMS) to explore the transformation of litter with different composition and decay rate (ponderosa pine needle vs. fine root) to SOM during 18 months in a temperate conifer forest mineral (A horizon) soil. Based on 13C Py–GC–MS–C–IRMS the initial litter and bulk soil had ∼1/3 of the total pyrolysis products identified in common. The majority was related either to carbohydrates or was non-specific in origin. In bulk soil, carbohydrates had similar levels of enrichment after needle input and fine root input, while the non-specific products were more enriched after needle input. In the humin SOM fraction (260 yr C turnover time) we found only carbohydrate and alkyl C-derived compounds and greater 13C enrichment in the “carbohydrate” pool after fine root decomposition. 15N Py–GC–MS–C–IRMS of humic substances showed that root litter contributed more than needle litter to the enrichment of specific protein markers during initial decomposition. We found little evidence for the selective preservation of plant compounds considered to be recalcitrant. Our findings suggest an indirect role for decomposing plant material composition, where microbial alteration of fine root litter seems to favor greater initial stabilization of microbially derived C and N in SOM fractions with long mean turnover times, such as humin, compared to needles with a faster decay rate.

Nitrogen availability affects saprotrophic basidiomycetes decomposing pine needles in a long term laboratory study

Fungi, especially basidiomycetous litter decomposers, are pivotal to the turnover of soil organic matter in forest soils. Many litter decomposing fungi have a well-developed capacity to translocate resources in their mycelia, a feature that may significantly affect carbon (C) and nitrogen (N) dynamics in decomposing litter. In an eight-month long laboratory study we investigated how the external availability of N affected the decomposition of Scots pine needles, fungal biomass production, N retention and N-mineralization by two litter decomposing fungi – Marasmius androsaceus and Mycena epipterygia. Glycine additions had a general, positive effect on fungal biomass production and increased accumulated needle mass loss after 8 months, suggesting that low N availability may limit fungal growth and activity in decomposing pine litter. Changes in the needle N pool reflected the dynamics of the fungal mycelium. During late decomposition stages, redistribution of mycelium and N out from the decomposed needles was observed for M. epipterygia, suggesting autophagous self degradation.

Fire Behavior of Mediterranean Pine Forest Litter Assessed in a Specifically Designed Experimental Rig

Measurement results on fire behavior characteristics for the ignition and spreading of a line source fire in the pine litter of Pinus halepensis, and Pinus pinaster, needles have been reported in the current paper. Their subsequent data processing and conclusions for the conducted experimental burns have been also presented. Experiments were carried out in laboratory conditions using a specifically designed testing rig. Basic controlled independent variables in the course of the experiment were the slope angle of the work plane, the airflow velocity, and the fuel moisture content. To provide a quantitative assessment for the effects of various parameters on fire spread and flame angle during experiments, statistical processing of experimental results has been employed based on the regression analysis. The developed model equations describe the slope of terrain and the wind velocity as determining factors for the examined characteristics. The information acquired in the present experimental study is useful for establishing quantitative relationships between important fire behavior descriptors and its environment for the formulation of a physical model predicting spreading of fires into low-rise pine fuel beds.

No UV enhancement of litter decomposition observed on dry samples under controlled laboratory conditions

Abstract In field studies, various workers have observed a stimulation of organic matter breakdown by visible light and UV radiation. We aimed to confirm the involvement of UV radiation under controlled laboratory conditions and quantify the magnitude of any stimulation. Grass and pine foliage samples were oven-dried and continuously exposed to UV radiation at room temperature for up to 60 days. A range of UV flux densities was established using shading to different levels. After UV exposure under air-dry conditions, samples were rewetted and incubated in the dark with microbial inoculums to investigate whether UV exposure had rendered samples more susceptible to subsequent microbial decomposition. However, we found no weight loss associated with different UV flux densities. The same finding held true for grass and pine litter samples. Similarly, microbial decomposition of either grass or pine litter was not enhanced by prior UV exposure. These findings suggest that UV-induced photooxidation of dry materials cannot be responsible for the observed apparent enhancement of weight loss of litter samples under UV exposure in the field.

Nitrogen cycling following mountain pine beetle disturbance in lodgepole pine forests of Greater Yellowstone

Widespread bark beetle outbreaks are currently affecting multiple conifer forest types throughout western North America, yet many ecosystem-level consequences of this disturbance are poorly understood. We quantified the effect of mountain pine beetle ( Dendroctonus ponderosae) outbreak on nitrogen (N) cycling through litter, soil, and vegetation in lodgepole pine ( Pinus contorta var. latifolia) forests of the Greater Yellowstone Ecosystem (WY, USA) across a 0–30 year chronosequence of time-since-beetle disturbance. Recent (1–4 years) bark beetle disturbance increased total litter depth and N concentration in needle litter relative to undisturbed stands, and soils in recently disturbed stands were cooler with greater rates of net N mineralization and nitrification than undisturbed sites. Thirty years after beetle outbreak, needle litter N concentration remained elevated; however total litter N concentration, total litter mass, and soil N pools and fluxes were not different from undisturbed stands. Canopy N pool size declined 58% in recent outbreaks, and remained 48% lower than undisturbed in 30-year old outbreaks. Foliar N concentrations in unattacked lodgepole pine trees and an understory sedge were positively correlated with net N mineralization in soils across the chronosequence. Bark beetle disturbance altered N cycling through the litter, soil, and vegetation of lodgepole pine forests, but changes in soil N cycling were less severe than those observed following stand replacing fire. Several lines of evidence suggest the potential for N leaching is low following bark beetle disturbance in lodgepole pine.

Within-stand variation in understorey vegetation affects fire behaviour in longleaf pine xeric sandhills

The frequent fires typical of the longleaf pine ecosystem in the south-eastern USA are carried by live understorey vegetation and pine litter. Mature longleaf pine stands in the xeric sandhills region have a variable understorey vegetation layer, creating several fuel complexes at the within-stand scale (20 m2). We identified three fuel complexes found in frequently burned stands on the Carolina Sandhills National Wildlife Refuge, and used prescribed fire to test whether distinct sets of fire conditions were associated with each fuel complex. Study plots were dominated by either turkey oak or wiregrass in the understorey, or lacked understorey vegetation and contained only longleaf pine litter. Turkey oak-dominated plots had the highest fuel loads, and during burns they had higher total net heat flux than wiregrass- or longleaf pine litter-dominated plots, and longer burn durations than wiregrass-dominated plots. Across all plots, the quantity of litter fragments had the greatest effect on fire temperature and duration of burn. These results show that the patchy understorey vegetation within longleaf pine stands will create heterogeneous fires, and areas dominated by turkey oak may have increased fire intensity and soil heating compared with the other two fuel complexes.

Litter Decomposition and Soluble Carbon, Nitrogen, and Phosphorus Release in a Forest Ecosystem

Litter is an important source of easily mineralizable C, N, and P for microbial metabolism in forest ecosystems; however, its decomposition is dependent upon a variety of biotic and abiotic factors, including litter chemical composition and plant specie, soil properties, and climate. We investigated C, N, and P mineralization patterns of pine litter, oak and a mixture of various species commonly found in wetland landscape position. Litter species were incubated (alone and with soils) under laboratory conditions in the dark for 120 days. Samples were leached weekly and the leachates were analyzed for pH, E4:E6 ratio, dissolved organic carbon (DOC), total N, NO3, NH4, soluble reactive P, and total P. CO2 effluxes during the 120-d incubation period were measure using NaOH traps. Carbon loss was calculated as the sum of DOC and CO2 effluxes. Results indicated that patterns of C and N release varied with litter species and soil type. Mix species treatment resulted in larger DOC and N pulses compared to pine and oak treatments. The majority of the DOC, N, and P leached was retained by the soils. When litters were added to the soils, a greater proportion of the C was lost as CO2, while litter incubated alone lost more C as DOC. This result demonstrated the importance of the soil microbial community affecting the patterns of litter mineralization. Total N concentration and C:N ratio of the litter species were significantly correlated to C loss.

Interactions Between Testate Amoebae and Saprotrophic Microfungi in a Scots Pine Litter Microcosm

In all terrestrial ecosystems, testate amoebae (TA) encounter fungi. There are strong indications that both groups engage in multiple interactions, including mycophagy and decomposition of TA shells, processes which might be fundamental in nutrient cycling in certain ecosystems. Here, we present the results of an experiment focusing on interactions between TA and saprotrophic microfungi colonizing Scots pine (Pinus sylvestris L.) litter needles. The needles were collected from a temperate pine forest and cultivated in damp chambers. Over a few weeks, melanized mycelium of Anavirga laxa Sutton started to grow out of some needles; simultaneously, the common forest-soil TA Phryganella acropodia (Hertwig and Lesser) Hopkinson reproduced and spread around the mycelium. We investigated whether a potential relationship between TA and saprotrophic microfungi exists by comparing the composition of TA communities on and around the needles and testing the spatial relationship between the A. laxa mycelium and P. acropodia shells in the experimental microcosm. Additionally, we asked whether P. acropodia utilized the A. laxa mycelium as a nutrient source and screened whether P. acropodia shells were colonized by the microfungi inhabiting the experimental microcosm. Our results indicate that saprotrophic microfungi may affect the composition of TA communities and their mycelium may affect distribution of TA individuals in pine litter. Our observations suggest that P. acropodia did not graze directly on A. laxa mycelium, but rather fed on its exudates or bacteria associated with the exudates. The fungus Pochonia bulbillosa (Gams & Malla) Zare & Gams was often found parasitising encysted shells or decomposing already dead individuals of P. acropodia. TA and pine litter microfungi engage in various direct and indirect interactions which are still poorly understood and deserve further investigation. Their elucidation will improve our knowledge on fundamental processes influencing coexistence of soil microflora and microfauna.

A signal-substrate match in the substrate-borne component of a multimodal courtship display

Abstract The environment can impose strong limitations on the efficacy of signal transmission. In particular, for vibratory communication, the signaling environment is often extremely heterogeneous at small scales. Nevertheless, natural selection is expected to select for signals well-suited for effective transmission. Here, we test for substrate-dependent signal efficacy in the wolf spider Schizocosa stridulans Stratton 1991. We first explore the transmission characteristics of this important signaling modality by playing recorded substrate-borne signals through three different substrates (leaf litter, pine litter, and red clay) and measuring the propagated signal. We found that the substrate-borne signal of S. stridulans attenuates the least on leaf litter, the substrate upon which the species is naturally found. Next, by assessing mating success with artificially muted and non-muted males across different signaling substrates (leaf litter, pine litter, and sand), we explored the relationship between substrate-borne signaling and signaling substrate for mating success. We found that muted males were unsuccessful in obtaining copulations regardless of substrate, while mating success was dependent on the signaling substrate for non-muted males. For non-muted males, more males copulated on leaf litter than any other substrate. Taken together, these results confirm the importance of substrate- borne signaling in S. stridulans and suggest a match between signal properties and signal efficacy – leaf litter transmits the signal most effectively and males are most successful in obtaining copulations on leaf litter.

Revision of “Septonema ochraceum” revealed three new species of Venturiaceae and Herpotrichiellaceae

Survey of seven strains determined as Septonema ochraceum (Dothideomycetes, inc. sed.) isolated from pine litter or obtained from public collections revealed three new species, Fusicladium cordae, F. sicilianum (Venturiaceae), Cladophialophora matsushimae (Herpotrichiellaceae) and a cryptic species morphologically identical to Devriesia americana (Teratosphaeriaceae), but phylogenetically distinct. Morphological survey and phylogenetic analysis using nucleotide sequence data from the nuclear ribosomal subunit genes indicate a close relationship within three species colonising pine litter needles, F. cordae, F. pini and F. ramoconidii. F. sicilianum is most related to F. rhodense. C. matsushimae represents a species belonging to one of the lineages of the polyphyletic genus Cladophialophora. None of the strains observed can be classified morphologically as S. ochraceum, of which the type material does not exist.

Pine Litter from Afforestations Hinders the Establishment of Endemic Plants in Semiarid Scrubby Habitats of Natura 2000 Network

A sowing experiment was carried out using three endemic secondary successional species that commonly co-occur with Pinus halepensis in afforestations in southeast Spain. The experiment simulated the natural arrangement of needle litter over soil to test the litter’s effect on seedling emergence and early growth of dwarf-shrubs and annual species, the main components of some European Habitats of Community Interest in Spain. Three sowing treatments were compared in a growth chamber: (1) soil without litter taken from clearings in a pine plantation (BARE); (2) intact soil and litter forming two distinct layers as in the field (PINE); and (3) soil and pine litter mixed in the laboratory (PINEMX). Seedling emergence of Diplotaxis harra and Thymus zygis were seven and two times higher, respectively, on BARE than on the pine litter treatments. Pine litter significantly decreased seedling biomass, length, and number of leaves of D. harra and T. zygis. Thymus capitatum was weakly affected by the presence of pine litter. We suggest that plant recruitment in the understory of P. halepensis is partially controlled by interference of pine litter, which might affect dynamics of the studied species. We propose that management practices counteract this negative effect by manipulating the pine litter layer to achieve successful ecological restoration and conservation of endemic-rich secondary communities in Natura 2000 sites in semiarid western Mediterranean areas.