Pine Litter Research Articles

Burn Severity Effects on Sediment and Nutrient Exports from Southeastern Forests Using Simulated Rainfall

Abstract Burn severity, commonly assessed as the amount of fuel consumed during fire, is an indicator of postfire sediment yield and erosion. This study examined the effect of burn severity on sediment and nutrient response in three different fire-adapted forest types of the Southeast. Soil and litter samples were experimentally burned to achieve increasing levels of fuel consumption. Simulated rainfall was applied to burned litter samples collected from pine, hardwood, and mixed hardwood-pine forests in the Clemson Experimental Forest. Runoff and leachate samples were collected and analyzed for sediment yield (kilograms per hectare) and total suspended solids (grams per liter); both runoff and leachate samples were analyzed for ammonium (NH4–), nitrate (NO3–), and orthophosphate (PO43–). Sediment yield and total suspended solids increased at only the highest burn severity treatment in all three forest types, with pine litter samples yielding significantly greater sediment in surface runoff than both mixed and hardwood samples. Burn treatment did not readily affect soluble nutrient concentrations in either runoff or leachate, but the data suggest that high-severity burning increases the availability of PO43– bound to sediment. This study suggests that high-severity burn patches function as sediment sources, but overall sediment and nutrient response to burning was minimal. Study Implications This study suggests that low-to-moderate burn severity, in terms of litter removal, is not an important indicator of sediment and nutrient exports from southeastern forests; precipitation in the immediate aftermath of fire (<48 hours) is not an effective transport mechanism for biologically available macronutrients; and that even at the highest burn severity treatment, sediment yield was relatively low.

Effect of pretreatments on cellulosic composition and morphology of pine needle for possible utilization as substrate for anaerobic digestion

Waste residues from agricultural and forest resources have received much attention as potential source of lignocellulosic biomass (LCB) especially after the “food-versus-fuel” conflict. Therefore, exploring the potential of LCB (especially forest biomass) as a resource for sustainable bioenergy generation is highly promising. The present study reports the structural modification in the cross-linking of lignocellulosic complex in pine needle forest biomass after pretreatments: milling, steam explosion and acid-base-acid treatments. The changes in morphology and composition of the cellulose and lignin in pine needles after pretreatments was evaluated using Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FT-IR) microspectroscopy, Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM). Field Emission Scanning Electron micrographs revealed that pretreatments resulted in changes in orderly arrangement of interwoven fibrils, surface abnormalities in cells surrounding stomatal opening and exposure of vascular bundle. FT-IR of pretreated substrate indicated significant changes in functional moieties of ester bond between lignin and hemicelluloses, phenol hydroxyl moieties and aromatic ring associated with lignin and hydrogen bonding in cellulose. The findings in the present study thus open up avenues for exploring potential of pretreated pine needles for renewable bioenergy generation. Anaerobic digestion (AD) of the pretreated biomass resulted in 21.4% higher methane levels as compared to untreated pine litter. Appearance of lignin droplets and deposition of coalescent materials on pre-treated biomass surface was also observed in the present study. These colloidal lignin particles could serve as potential nanocomposites, for application in biomaterial applications.

Probabilistic Ranking of Microbiomes Plus Taxa Selection to Discover and Validate Microbiome Function Models for Multiple Litter Decomposition Studies

The overwhelming complexity of microbiomes makes it difficult to decipher functional relationships between specific microbes and ecosystem properties. While machine learning analyses have demonstrated an impressive ability to correlate microbial community composition with macroscopic functions, mechanisms that dictate model predictions are often unknown, and predictions often lack an assigned metric of uncertainty. In this study, we apply Bayesian networks to build on prior feature selection analyses and construct easy-to-interpret probabilistic models, which accurately predict levels of dissolved organic carbon (DOC) from the relative abundance of soil bacteria (16S rRNA gene profiles). In addition to standard cross-validation, we show that a Bayesian network model trained using samples from a pine litter decomposition study accurately predicts DOC of samples from an independent oak litter decomposition study, suggesting that mechanisms driving variation in soil carbon storage may be conserved across different types of decomposing plant litter. Furthermore, the structure of the resulting Bayesian network model defines a minimal set of highly informative taxa, whose abundances directly constrain the probability of high or low DOC conditions. Significant accuracy of the Bayesian network model with independent data sets supports the validity of the identified relationships between taxa abundance and DOC.

Flammability Characteristics of Surface Fuels in a Longleaf Pine (Pinus palustris Mill.) Woodland

To investigate fuel flammability, we quantified burning characteristics of 21 fuel categories in a longleaf pine (Pinus palustris Mill.) woodland in central Alabama, USA. Litter was burned under controlled laboratory conditions. Flammability characteristics, including resistance to ignition, flaming duration, smoldering duration, maximum flame height, and percent consumption, were measured. The fuels were hierarchically clustered into five groups of similar flammability characteristics that explained 89% of the variance. Percent consumption and maximum flame height values ranged from 7% ± 1 standard errors (SE) and 12 cm ± 1 SE for the low flammability group (bark and charcoal), to 86% ± 1 SE and 62 cm ± 3 SE for the high flammability group (bracken fern (Pteridium latiusculum (Desv.) Hieron. ex R.E.Fr. = {syn: P. aquilinum}), grass, and fire-facilitating oak (Quercus spp.) leaves). Results support observed flammability differences between fuel types such as oak and pine (Pinus spp.) litter, and duff, and provide a previously unquantified comparison of surface fuels comprehensive of a longleaf pine community. Further, clustering analysis indicated that plant species that become abundant post-disturbance may help maintain fire-vegetation feedbacks in the absence of pine litter. Understanding flammability characteristics of surface fuels may further inform prescribed fire application in stands where fuels have been altered.

Carbon Stock in Sandy Soils of Pine Forests in the West of Russia

A comparative assessment of carbon accumulation in the soils of pine forests in western Russia (the Republic of Karelia, the Karelian Isthmus, and Bryansk region) developed on coarse-textured parent materials has been made. The total carbon stock in the litter and upper soil layer (0–50 cm) varied from 47 t/ha in the soils of pine forests of Bryansk region to 116 t/ha in the soils of pine forests of the Karelian Isthmus. It has been shown that the main factors of carbon accumulation in the soils of pine forests in western Russia were the climate, parent materials, vegetation, agricultural activity, and fires. The influence of climatic conditions has been clearly manifested in the levels of carbon accumulation in the litter and in the upper humus-accumulative soil horizons. In the pine litter within the zone of mixed forests (Bryansk region), the level of carbon accumulation was the lowest, whereas the litter layer of pine forests in the northern taiga (Karelia) has the highest stock of carbon. At the same time, the lowest carbon stocks in the upper mineral soil layers has been noted for the soils of northern taiga forests, which had no humus-accumulative mineral horizon. The variability of carbon stocks in the litter layer was largely controlled by the C/N ratio, as well as by the fraction of deciduous undergrowth and grasses producing high-quality litter. The influence of agricultural activity on soil carbon stock in pine forests was especially pronounced on the Karelian Isthmus with the high agricultural activity in the past, as well as in Bryansk region, where pine forests are formed from pine plantations. The effect of fires on soil carbon stock was most pronounced in heather and lingonberry pine forests of the northern taiga of Karelia.

Dynamic forest fire risk evaluation in Poland

Abstract The weather conditions determine the dynamic forest fire risk. In Poland, the dynamic forest fire risk is calculated using a method elaborated at the Forest Research Institute. The forest fire risk degree (4-level scale) is calculated every day at 9:00 am and at 1:00 pm during the fire season (1.03 till 30.09) for 60 prognostic zones selected on the basis of stand and climatic conditions. 97% of all annual forest fires occur during the fire season. Surface fires are a significant part of the fires (90%) and occur in forest stands where pine is the dominant species. The purpose of the research was to prepare a new method of forecasting forest fire risk, which would enable a more precise method of evaluation of the risk of an outbreak of fire in relation to the existing and forecast meteorological conditions in forests. The results obtained during testing of this method indicate a high accuracy in forecasting fire risk and a satisfactory precision of formulae for calculating moisture content of pine litter. The assumptions of the new method included: – possibility of determining the actual risk of fire for the given area, being the average for all measurement points located on the terrain equally those in which the moisture content measurement of litter has not been performed, – possibility of forecasting the risk of forest fire for the afternoon in the morning hours of the given day, – possibility of forecasting fire risk for the following day, – forecasting moisture content of litter for the afternoon and of the given day and for the following day, – drawing up a method enabling limitation of operational costs of fire prevention system.

In situ litter decomposition and nutrient release from forest trees along an elevation gradient in Central Himalaya

Litter plays a central role in the nutrient budgets of forests by supplying inflow to nutrient turnover through decomposition. However, studies of litter decomposition and nutrient dynamics in forest ecosystems are limited, particularly for the central Himalaya forest ecosystems with wide importance for stability and nutrient dynamics under global change. A one-year-long in-situ litter decomposition experiment was conducted with multiple tree species, dominating forests along an elevation gradient from 1300 to 2500 meters above sea level (m.a.s.l.) in central Nepal. The main aim was to examine the litter mass loss, factors affecting the decomposition process and the nutrient dynamics of the studied tree species, based on the litter bag method and physico-chemical analyses of the litter and the soil over time. The results showed that litter mass loss decreased with elevation, being the highest at low elevation (63.65%), followed by middle (46.59%) and high elevation (44.48%). The litter from deciduous tree species decomposed more rapidly than that from evergreen species, with Alnus litter decomposing the fastest (1.42 yr−1) and Pinus litter decomposing the slowest (0.53 yr−1), whereas the other species were in the order of Engelhardia > Castanopsis > Eurya > Lyonia > Quercus > Rhododendron > Schima. The contents of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) in the initial litter (i.e., freshly fallen leaves), as well as weather factors (precipitation and temperature) were the best predictors of litter mass loss. The nutrient release from the litter was not discerned throughout the annual decomposition process, however, the release rate at the end of the study period followed the order of P > K > C > N, indicating that litter is a potential sink of N due to its slow release rate. This study may serve as a baseline for long-term research on nutrient dynamics in forest ecosystems of central and eastern Himalaya, which is imperative for preserving biodiversity and ecosystem stability and for mitigating climate change impacts.

Changes in soil biochemical properties following replacement of Banj oak forest with Chir pine in Central Himalaya, India

IntroductionIn Central Himalaya, anthropogenic activities have led to the widespread replacement of Banj oak (Quercus leucotrichophora) forest by Chir pine (Pinus roxburghii) for decades. This study was conducted to determine how natural Banj oak, Chir pine, and mixed oak-pine forest would differ in soil microbial biomass and soil nutrients. Soil microbial biomass nitrogen (SMBN) and phosphorus (SMBP), soil organic carbon (SOC) total nitrogen (TN), and total phosphorus (TP) in the 0 to 15 cm soil layer were investigated in the Central Himalayan region in the stands of Banj oak, mixed oak-pine, and Chir pine forest.ResultsThe SMBN and SMBP were significantly higher in Banj oak and mixed oak-pine forest as compared to Chir pine forest. The ratios of SMBN to TN (SMBN/TN) and SMBP to TP (SMBP/TP) were significantly higher in the Chir pine forest, indicating that in this forest, the proportion of microbial biomass N and P to total soil N and P was higher as compared to Banj oak forest. A similar pattern of variation was found in relation to season across the forests, all with an apparent peak in the rainy season.ConclusionThese results indicate that low microbial biomass N and P may be one of the reasons to create a nutrient poor site in Chir pine forest. The collection of pine litter by local people also impairs the return of nutrients to the soil and makes it difficult for Banj oak to re-invade areas occupied by Chir pine. This calls for cautions in large-scale conversions of the Banj oak forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.

The Effect of Litter Composition on the Characteristics of Their Water-Soluble Organic Matter

The composition of water-soluble organic matter (WSOM) of coniferous- deciduous, coniferous, and moss litter was studied. Litter type affects the composition of WSOM. Sphagnum litter contains less N and dissolved organic carbon (DOC), but more carbohydrates, the WSOM from this litter is characterized by the lowest extinction coefficients Е254. WSOM from mixed litter with a predominance of birch litter had a maximum content of N and a small amount of soluble phenolic (SP) substances. WSOM from litter of pine needles differ from the rest by having a lower content of carbohydrates, the maximum amount of SP and hydrophobic fractions. All investigated WSOM were characterized by high rates of decomposition: half-decomposition time of their stable fractions was 2–4 months. WSOM from pine litter at pH ~ 6.5 were absorbed by the BF horizon of iron–illuvial podzol, starting from the concentration of DOC of 100 mg/L. Substances from birch–spruce litter were adsorbed insignificantly under similar conditions.

Effects of initial microbial biomass abundance on respiration during pine litter decomposition

Microbial biomass is one of the most common microbial parameters used in land carbon (C) cycle models, however, it is notoriously difficult to measure accurately. To understand the consequences of mismeasurement, as well as the broader importance of microbial biomass abundance as a direct driver of ecological phenomena, greater quantitative understanding of the role of microbial biomass abundance in environmental processes is needed. Using microcosms, we manipulated the initial biomass of numerous microbial communities across a 100-fold range and measured effects on CO2 production during plant litter decomposition. We found that the effects of initial biomass abundance on CO2 production was largely attenuated within a week, while the effects of community type remained significant over the course of the experiment. Overall, our results suggest that initial microbial biomass abundance in litter decomposition within an ecosystem is a weak driver of long-term C cycling dynamics.

ЗАПАСИ ОРГАНІЧНОГО КАРБОНУ У БЛОЦІ "ПІДСТИЛКА – ҐРУНТ" СОСНОВОЇ ЕКОСИСТЕМИ ПОЛІСЬКОГО РЕГІОНУ

The results of studies of the content and stocks of organic carbon in the block "litter – soil" of pine ecosystems in Zhytomyr and Chernihiv Polissia are presented. The forest ecosystems are important stabilizers of the carbon cycle as well as stocks of carbon. The components of the forest ecosystem are interconnected by the flows of energy and substances. Binding ÑÎ2 in the block of "plant-soil", followed by the transformation of carbon into insoluble humus compounds is of particular importance. In the research area sod - light-podzolic and sod-medium-podzolic soils on fluvioglacial sands are mostly spread. These soils belong to the category of old arable ones. Present here are also peat – marsh soils. It is shown that the process of humus accumulation is characterized by low intensity, which is caused by a complex of reasons, in particular, the sandy composition of sod-podzolic soils (particle content < 0,01 mm – 7,5 %).The thickness of the profile humus portion is 18 cm. The average content of humus is 0,97 %, and reserves – 28,3 t/ha in a 20-cm layer. Similar indicators of carbon are 0,56 % and 16,4 t/ha, respectively. Organic substance of sod-podzolic soils of pine habitats is resistant to mineralization and for a long time is removed from the cycle of substances of the pine ecosystem. The average carbon content in hydromorphic organogenic soils increases to 18,1 % and its stocks are 168,9 t/ha. The ability for mineralization peat soils is lower than that of sod-podzolic soils. So, they have a high carbon sequestration capacity. Pine litter reserves on the average are 30–33 t/ha, and carbon reserves on the average are – 12,6 t/ha, with its stable content – 40 %.The total carbon reserves in the block "litter – soil" of a typical pine ecosystem of Polissia are on average 29 t/ha, with the bulk of them being concentrated in the soil. Considering that highly productive pine forests are formed on the infertile soils of Polissia, their afforestation will not only stop the intensive degradation of soils of Ukraine, but also will increase the deposition of greenhouse gases, which will help to prevent further climate change at the regional level.

A mismatch between signal transmission efficacy and mating success calls into question the function of complex signals

Variation in transmission characteristics of signalling environments is hypothesized to influence the evolution of signalling behaviour, signal form and sensory systems of animals. However, many animals communicate across multiple signalling environments, raising the possibility that some displays have evolved explicitly to enable communication across heterogeneous signalling environments. In the present paper, we explored multiple potential impacts of the signalling environment on courtship displays in the wolf spider Schizocosa retrorsa. Males of this species court females on a range of substrate types using a combination of vibratory and visual signals. Through a series of experiments, we investigated (1) activity patterns and male microhabitat use, (2) component-specific vibratory signal transmission across natural substrate types and (3) copulation success across substrate types and light levels. We found that, in the laboratory, (1) female and male S. retrorsa are most active during daylight hours, and mature males resided and courted most on leaf litter, as compared to their natural habitat types of pine litter or sand; (2) male vibratory courtship signals transmitted best on leaf litter, yet (3) males obtained the highest copulation success on sand, regardless of light level. Our results demonstrate that copulation in S. retrorsa is more likely to occur in environments with suboptimal vibratory signal transmission, irrespective of visual signal transmission. We suggest that these results point to (1) a minor role of bimodal (vibratory and visual) courtship signalling in S. retrorsa, (2) the importance of an additional signalling modality (most likely air particle movement), (3) a role of other substrate-dependent factors (e.g. predation risk), and/or (4) a reversed female preference for vibratory signalling.

Decelerated carbon cycling by ectomycorrhizal fungi is controlled by substrate quality and community composition.

Interactions between symbiotic ectomycorrhizal (EM) and free-living saprotrophs can result in significant deceleration of leaf litter decomposition. While this phenomenon is widely cited, its generality remains unclear, as both the direction and magnitude of EM fungal effects on leaf litter decomposition have been shown to vary among studies. Here we explicitly examine how contrasting leaf litter types and EM fungal communities may lead to differential effects on carbon (C) and nitrogen (N) cycling. Specifically, we measured the response of soil nutrient cycling, litter decay rates, litter chemistry and fungal community structure to the reduction of EM fungi (via trenching) with a reciprocal litter transplant experiment in adjacent Pinus- or Quercus-dominated sites. We found clear evidence of EM fungal suppression of C and N cycling in the Pinus-dominated site, but no suppression in the Quercus-dominated site. Additionally, in the Pinus-dominated site, only the Pinus litter decay rates were decelerated by EM fungi and were associated with decoupling of litter C and N cycling. Our results support the hypothesis that EM fungi can decelerate C cycling via N competition, but strongly suggest that the 'Gadgil effect' is dependent on both substrate quality and EM fungal community composition. We argue that understanding tree host traits as well as EM fungal functional diversity is critical to a more mechanistic understanding of how EM fungi mediate forest soil biogeochemical cycling.

Isolasi dan Karakterisasi Jamur Pendegradasi Katekin dari Seresah Pinus

Isolation of catechin-degrading fungus from pine litter samples was done using minimal medium that containing catechin as sole carbon and energy source. A total of 53 isolates were chosen to represent different colonial types of catechin degrading-fungus. The isolates were screened for their ability to degrade catechin in three stages. The first stage of screening was based on their ability to grow on solid medium containing 2 mM, and as a result, 28 isolates were selected. The second stage of screening on the same medium but containing 4 mM of catechin resulting in 14 selected isolates. The third stage screening was based on their mean growth rate constant (k), instantaneous growth rate constant (m) and generation time (g) on minimal medium containing 4 mM catechin. The result showed that four isolates (D9, K2, K11, and S11) were the best catechin degradator. Further growth kinetic study (k, m ,and g) of selected isolates indicated that D9, K2, and S11 grew well on the medium containing 40 mM, but K11 was inhibited by concentration of higher than 10 mM. Catechin biodegradation process was determined by following the decrease of catechin concentration on liquid medium. It was found that isolate K2 had higher ability to degrade catechin than the isolate K11. Finally, the four selected isolates from the third stage were characterized in terms of macroscopic, microscopic and phenotypic characters and identified. The result of the study showed that the isolates D9, K2 and S11 were identified as member of Aspergillus niger group. The isolate D9 was very similar to isolate S11, while the isolate K2 was found to be the most similar with Aspergillus niger van Tiegh. IFO 6341. The isolate K11 was assigned to be member of the genus Trichoderma.

Short- and Long-Term Effects of Snow-Depth on Korean Pine and Mongolian Oak Litter Decomposition in Northeastern China

Changes in snow-depth induced by climate change can affect litter decomposition, but it remains unclear whether the effects of snow-depth on litter decomposition vary among seasons. Our aim was to assess the possible short- and long-term effects of snow-depth on foliar litter decomposition for Korean pine (Pinus koraiensis) and Mongolian oak (Quercus mongolica). A snow-depth manipulation experiment that included snow-removal, control and snow-addition treatments was conducted in northeastern China. All the snowfall was intercepted by transparent plexiglass in the snow-removal treatment and then transferred to the snow-addition treatment. Three replicate litterbags per species were buried in each treatment and sampled in the freezing onset, deep freezing and thawing stages and in the early, middle and late snow-free seasons from November 2014 to October 2015. Our results showed that the oak litter decomposed faster than the pine litter, but the magnitude of the effect of snow-depth was greater for the latter because of differences in litter chemical traits. Litter mass loss decreased with decreasing snow-depth in the snow-covered season but increased in the following snow-free season. The short-term effect resulting from the changes in soil environments affected litter decomposition during the snow-covered season, while the long-term effect due to litter chemical traits and the microbial biomass carbon concentration controlled the decomposition in the snow-free season. These results indicated that snow-depth significantly influences the foliar litter decomposition of the two tree species with contrasting initial qualities, but the effects differed between the snow-covered and snow-free seasons. These results deepen our understanding of biogeochemical cycling in cold regions.

Energy stock seasonal dynamics in the pine forest beddings of Holosiivsky National Nature Park

The article presents the results of research of the energy stock in the components of pine forest bedding of National nature park Holosiivsky. The study was aimed on measurement and comparison of the carbon accumulation in the components of forest litter in natural and artificial forest ecosystems. The results of this study can be used to predict the stability of forest phytocoenoses. It is established that the energy supply of forest litter is an important element of the energy flows of the forest ecosystem and provides support for its stability. The study of seasonal dynamics of carbon accumulation was conducted on two monitoring plots of 50 m×50 m size. The first plot (D1) is represented by the association Dicrano-Pinetum Preising and Knapp 1942 ( Dicrano-Pinion Union (Libbert 1933) and located in a pine forest formed by Pinus sylvestris artificial plantations. The second plot (D2) is natural forest represented by the association Serratulo-Pinetum (W. Mat. 1981) with Pinus sylvestris aged 100–120 years in the first tier. The energy stock of artificial litter in artificial pine phytocoenoses exceeded the energy supply of natural pine litter. The average energy potential of artificial pine forest litter was 50857.75 kJ/m2, and it was 23910.00 kJ/m2 in natural pine phytocoenoses. The seasonal dynamics of the organic matter of the forest litter of the natural pine forest was smoother with the presence of one peak in the month of May, and for artificial pine characterized by periodic changes during the vegetation period with peaks in June, September and November. Insignificant fluctuations during the year of the energy potential of the forest litter of the natural pine forest showed a greater stability compared to artificial ones. Overall, the study confirmed the importance of monitoring the accumulation of carbon in various components of forest ecosystems.

Soil fauna affects the optical properties in alkaline solutions extracted (humic acid-like) from forest litters during different phenological periods

The formation of soil organic matter via humification of plant litter is important for long-term carbon sequestration in forests; however, whether soil fauna affects litter humification is unclear. In this study, we quantified the effects of soil fauna on the optical properties (i.e., ΔlogK and E4/E6) of the alkaline-extracted humic acid-like solutions of four foliar litters by removing soil fauna via litterbags with different mesh sizes in two subtropical evergreen broad-leaved forests. Litterbags were collected at the leaf falling, budding, expanding, maturation, and senescence stages from November 2013 to October 2015 to assess whether the effects of soil fauna on litter humification vary in different plant phenology periods. The results showed that soil fauna significantly reduced the ΔlogK and E4/E6 values in the leaf expanding stage of oak litter and in the leaf falling stage of camphor and fir litters. The richness index of soil fauna explained 21%, 55%, 19%, and 45% of the variations in the E4/E6 values for oak, fir, camphor, and pine litters, respectively. The effects of litter water content on these optical properties were greater than that of temperature. These results indicated that soil fauna plays a key role in litter humification in the leaf expanding and falling stages and are potentially involved in soil carbon sequestration in these subtropical forests.

Pyrolysis kinetics of live and dead wildland vegetation from the Southern United States

The fundamental combustion behavior of live wildland vegetation is not fully understood. Since the combustion process during wildland fire starts with pyrolysis, there is a need for better understanding of pyrolysis to develop improved wildland fire models. The kinetics of pyrolysis of live and dead wildland vegetation has not been explored in detail. In this study, the pyrolysis kinetics were determined for 14 different plant species (live and dead) which are all native to the forests in the southern United States. Pyrolysis experiments were carried out in a Thermogravimetric analyzer (TGA) under inert conditions at 5 different heating rates ranged from 10 to 30 °C min−1. The iso-conversional and model-free method of KAS was used to calculate the activation energies and pre-exponential factors. The rates of pyrolysis as a function of conversion were calculated using the KAS method for all plant species (live and dead), and the results showed that during the sample decomposition, the highest rates were observed at the lower conversions. The dependence of activation energy on conversion fraction, type of plant species, and plant condition (live and dead) was investigated. For some plant species, an increase in activation energy with conversion was observed in the major pyrolysis zone for live samples. The effect of aging on apparent activation energy was studied by comparing the pyrolysis rates of live and dead longleaf pine foliage with longleaf pine litter (pine straw). The results showed that length of time since living increased the activation energy in the major pyrolysis zone. The average activation energy based on the KAS method for pyrolysis of abscised pine foliage (pine straw) was 183.4 kJ mol−1, while the activation energies were lower for live and dead longleaf pine foliage (167.3 and 167.4 kJ mol−1, respectively). Finally, the activation energies obtained in this study were compared with literature and the results showed that the average activation energies obtained in this study for palmetto, grass, broadleaf, and needle types are very close to the average activation energies obtained for different kinds of straw reported in the literature.

Site Type Effect on Litter Decomposition Rates: A Three-Year Comparison of Decomposition Process between Spoil Heap and Forest Sites

Research Highlights: Direct comparison of leaf litter decomposition rates between harsh soil conditions of degraded lands and adjacent “closer to natural” forest areas has not been done before. Background and Objectives: We aimed to fill this knowledge gap by determining the differences in amounts of carbon and nitrogen released by species-specific litter depending on decomposition rates in various stand and habitat conditions, which enables selection of the most ecologically and economically appropriate (for fast soil organic layer development) tree species for afforestation of reclaimed lands. Materials and Methods: The study was conducted on the external spoil heap of the “Bełchatów” lignite mine (Central Poland) and adjacent forests. In December 2013, we established a litterbag experiment beneath the canopies of birch and pine stands. We used litter of Alnus glutinosa (Gaertn.), Betula pendula (Roth), Pinus sylvestris (L.), and Quercus robur (L.) collected ex situ, which we installed (after oven-drying) beneath the canopies of eight stands. The experiment lasted for three years (with sampling of three-month intervals). Results: Harsh soil conditions of degraded lands are unfavorable for litter mineralization. It was found that 23%–74% of decomposed materials were mineralized in spoil heap stands, whereas in forest stands these amounts ranged from 35%–83%. Litter of Q. robur in birch stands on the spoil heap is predicted to take 12 years longer for total decomposition than in forest stands of the same species. This hinders organic carbon turnover and could result in elongation of the time for full biological and economic reclamation of degraded lands. On the other hand, decomposition of relatively fast decomposable litter (A. glutinosa and B. pendula) in pine stands on the spoil heap was faster than in pine stands in forest sites (17% and 13% faster, respectively). We did not observe this trend for decomposition of more recalcitrant litter types of P. sylvestris and Q. robur. Conclusions: The results show the value of selective choice of tree species for afforestation of post-mining areas to accelerate the development of technogenic soil substrates. We recommend introducing all tree species studied in the cluster form of admixtures as all of them could bring some profits in ecological and economical reclamation.

Establishment of mixed plantations of Pinus sylvestris var. mongolica and Populus × xiaozhuanica may not be appropriate: evidence from litter decomposition

Abstract Aims Mongolian pine (Pinus sylvestris var. mongolica) and Xiaozhuan poplar (Populus × xiaozhuanica) are two predominant afforestation tree species in the semi-arid sandy lands of northeast China, which are characterized by poor soil nutrients. Plant litter decomposition plays a critical role in regulating nutrient cycling in terrestrial ecosystems. Admixture of broadleaf litter to conifer litter is expected to improve litter decomposition and soil fertility, and thus productivity. However, the effects on the decomposition of litter mixture of the above two tree species are not well understood. Therefore, it is essential to assess the decomposition performance of litter mixture with the aim of improving forest nutrient management and the establishment of mixed plantation. Appropriate forest management practice is critical for the sustainability of site productivity in plantation forests. Methods We conducted a field litterbag decomposition transplant experiment for single pine litter, single poplar litter and their mixture in a pine stand, a poplar stand and an adjacent grassland for 16 months in the Keerqin Sandy Lands, northeast China. Important Findings After 16 months of incubation, there remained significantly more litter mass of pine (73.8%) than of poplar (67.2%). The mass remaining was positively correlated with litter carbon (C):nitrogen (N), C:phosphorus (P) and lignin:N ratios, and negatively with litter N and P concentrations, which suggests that initial litter chemical properties were an important factor affecting litter decay. Generally, net N and P immobilizations were observed during decomposition. This indicates that litter decomposition in this area was N-limited as N was progressively immobilized, and then tended to induce P limitation. Thus, we strongly recommend prohibiting litter harvesting by local residents to maintain soil fertility in this nutrient-poor area. Our results do not support the home-field advantage hypothesis, as illustrated by the fact that, in most cases, mass loss of litter from native habitat was comparable to that in transplanted habitats during decomposition. Furthermore, a dominant additive effect was detected, indicating that the establishment of mixed plantation may not be appropriate for these two species.