Larch Litter Research Articles

The Characteristics of Dissolved Organic Matter and Soil Microbial Communities in the Soils of Larix principis-rupprechtii Mayr. Plantations in the Qinling Mountains, China

Soil microorganisms and dissolved organic matter (DOM) play vital roles in nutrient cycling and maintaining plant diversity. The aim of this study was to clarify the relationship between DOM component characteristics and microbial community structure in the soil of Larix principis-rupprechtii Mayr. plantations. We quantified the responses of the soil microbial and DOM characteristics to stand age in a plantation forest ecosystem using phospholipid fatty acid (PLFA) analyses, ultraviolet-visible spectroscopy, and fluorescence spectroscopy. Three humic-like components and a fulvic-like component were identified from the soil samples, and humic-like substances were the dominant component of the soil DOM of the stands of different ages. The fluorescence index showed that the sources of soil DOM in the stands of different ages throughout the growth stages may be mostly plant residues, with very little contribution from microbial sources. Furthermore, the results demonstrated that stand age and growth season had a significant effect on the contents of the soil PLFA biomarkers of L. principis-rupprechtii Mayr. Additionally, significantly higher contents of different species of soil PLFA biomarkers were observed in the young forest (17a) than in the sapling forest (7a) and half-mature forest (27a), suggesting that stand age differences in the quality and quantity of larch litter and soil physicochemical characteristics affect the microbial community structure. Redundancy analysis (RDA) showed that changes in the soil DOM quality and components that were driven by growth season and stand age were the major drivers of variations in the soil microbial community structure in the study region. Overall, the seasonal variations in DOM quality and components may contribute to the variability of soil microorganisms, and the soil microbial responses to tree age will depend upon the provisioning of these resources.

The amelioration of degraded larch (Larix olgensis) soil depends on the proportion of Aralia elata litter in larch-A. elata agroforestry systems

Research has indicated that introducing Aralia elata into larch plantations forms an agroforestry system which could provide economic benefits for local farmers and improve degraded soils. However, the impact of litter mixtures on soil chemical and microbial properties in this agroforestry system are unclear, which limits efficient management of the agroforestry system. A 365-d incubation experiment examined the effect of litter mixtures of different proportions of larch (L) and A. elata (A) on soil chemical and microbial properties. The results show that levels of mineral N, available P, microbial biomass carbon and nitrogen, cumulative C mineralization, and activities of hydrolases and oxidases increased with an increase of A. elata in the litter mixtures. Concentration of total soil carbon, nitrogen, and phosphorous did not change (except for total nitrogen). Compared with larch litter alone, levels of mineral N, available P, microbial biomass carbon and nitrogen, cumulative C mineralization, and the activities of hydrolases and oxidases increased by 7.6–433.5%. Most chemical and microbial properties were positively correlated with mixed litter proportions and the initial levels of N, P, K, Ca, Mg, Mn, Zn and Cu in the litter, while negatively correlated with the initial concentrations of C, Fe and lignin, C/N and lignin/N ratios. The results indicate that A. elata litter can improve degraded larch soil and the degree depends on the proportion of A. elata litter in the litter mixtures.

Impact of Leaf Litter and Fine Roots in the Pool of Carbon, Nitrogen and Phosphorus Accumulated in Soil in Various Scenarios of Regeneration and Reconstruction of Forest Ecosystems

This study determined the rate of decomposition of fine roots and leaf litter from birch, larch, and pine, and compared the impact of fine root decomposition and leaf litter on carbon, nitrogen, and phosphorus accumulation in various regenerated and reconstructed forest ecosystems. The control plots were located on podzol soils in managed forest non-degraded habitats. Over a one-year experimental season, the decomposition of birch and larch fine roots released less carbon in comparison to leaf litter. The carbon mass-loss rates were 16% for birch roots and 15% for larch roots, while for birch and larch litter, the rates were 36% and 27%, respectively. For nitrogen, mass-loss rates were 48% for birch fine roots and 60% for larch and pine fine roots, whereas for pine and birch litter the rates were 14%, and 33% for larch litter. The results of our study prove the important role of fine root input to the soil’s carbon, nitrogen, and phosphorus pool and additionally their significance for CO2 sequestration within the studied regenerated terrestrial ecosystems.

Litter Decomposition and Nutrient Dynamics in Fire-Affected Larch Forests in the Russian Far East

Russian boreal forests hold a considerable carbon (C) stock and are subjected to frequent surface fires that unbalance C storage and ecosystem function. Although postfire ecological changes aboveground are well understood, biological C flows (e.g., decomposition in the postfire period) remain unclear. We present the results of a long-term field litterbag experiment on needle litter decomposition in typical Larix gmelinii boreal forests in the Russian Far East. For 3 years, we measured mass loss, C and nitrogen (N) concentrations, lignin and manganese dynamics, respiration intensity and enzyme activity in decaying needles, and environmental conditions (temperature and litter moisture). The decomposition rate at 850 days was 0.435 and 0.213 yr−1 in a control forest and in a forest 15 years after a surface fire, respectively. Early stages of needle decay did not differ among sites, whereas decomposition slowed in later stages in burned forest relative to the control (p < 0.01). This was supported by hampered respiration, slow lignin accumulation in decaying needles, and low peroxidase activity in burned forest. We found no direct N release, and decaying litter immobilization was more pronounced in the control forest. In the later stages, we revealed restrained mass loss and associated C release from larch litter in burned forest. Slow and delayed N release may alter organic matter accumulation, the N cycle, and regeneration of the fire-disturbed larch ecosystem. Our investigations highlight hampered C flow from aboveground litter to soil humus even decades after surface fire in a larch ecosystem. Given the climate-induced increase of fire activity, C retained in the litter layer represents a pool that is more vulnerable to the next fire event.

Effects of mixed-species litter on bacterial and fungal lignocellulose degradation functions during litter decomposition

Lignocellulose is the main component of forest litter. Due to the recalcitrance of coniferous litter, nutrient turnover is usually slower in coniferous plantations. Lignocellulose decomposition is reportedly rapid in mixed-species litter, but the underlying microbial metabolic pathways that may explain this rapid rate are not well-studied. We collected litter at 60, 150, 270, and 360 days after leaf fall at three plantation types: larch, sassafras, and larch/sassafras mixed plantations. We investigated the contents of lignocellulose components, enzyme activities, microbial communities, and potential genetic functional pathways related to lignocellulose degradation. Most rates of lignocellulose component degradation and enzyme activities in mixed litter during decomposition were significantly higher than in larch litter. The relative abundances of Betaproteobacteria and Dothideomycetes, which are involved in lignocellulose degradation, were significantly higher in mixed-species litter than in larch litter. Bacterial cellulose and hemicellulose, and fungal lignin degradation genes were significantly influenced by plantation forest type. Mantel tests showed that (i) the content of lignocellulose significantly correlated with bacterial and fungal community composition and enzyme activities, and (ii) fungal decomposers might be the main drivers of lignocellulose degradation in different litter types. Mixing larch and sassafras litter changed the composition of the microbial community and the lignocellulose-degradation gene complement, accelerated the decomposition of lignocelluloses, and restored soil quality.

Microbial groups and their functions control the decomposition of coniferous litter: A comparison with broadleaved tree litters

The conversion of secondary forests to pure coniferous plantations leads to a decrease in soil quality partly because of the slow decomposition rate of coniferous litter. Microbial decomposers directly regulate the decomposition process. However, little is known about how litter type and microbial communities including both bacteria and fungi interact to affect decomposition rates. A field experiment was performed consisting of seven treatments (i.e., four tree litters: Quercus mongolica, Juglans mandshurica, Acer mono, and Larix gmelinii) in which either monospecific litters or mixtures of larch litter with each broadleaved tree litter (mass ratio was 1:1) were placed into litterbags, and the microbial community composition and enzyme activities were measured. The results showed that in monospecific litters, the highest mass loss was observed in Acer litter, followed by Quercus, Juglans, and Larix litters. Furthermore, synergistic non-additive mixture effects were found in the Larix-Acer and Larix-Quercus mixtures. Most of the abundant bacterial taxa and potential functional genes encoding the hydrolytic enzymes were not significantly affected by the litter type. In contrast, each litter type was characterized by a specific fungal community, as well as different patterns of extracellular enzyme activity. The most abundant fungal decomposers in Larix litter during the first 540 days of decomposition, such as Meria, Lambertella, Venturia, and Ochroconis, were negatively correlated with most of the enzymatic activities, which possibly explains the slower decomposition rate of Larix litter. In conclusion, mixing Larix litter with broadleaved litters could change the microbial community composition, and accelerate the decomposition of hemicelluloses and lignin. Introducing broadleaved tree species with fast litter turnover rates by allowing natural regeneration and planting broadleaved tree species in pure larch plantations may be an effective way to restore soil quality in temperate forest regions.

Changes in phosphorus fractions caused by increased microbial activity in forest soil in a short-term incubation study

The effects of adding larch (Larix kaempferi) leaf litter and nitrogen (N) on microbial activity and phosphorus (P) fractions in forest soil were examined in a short-term (28-d) laboratory incubation study. The soil was analyzed using a modified Hedley sequential extraction procedure and an acid phosphatase assay. The addition of larch litter and N increased the acid phosphatase activity and decreased the labile P (H2O-P + NaHCO3-P) concentration. Compared with addition of larch litter only, addition of both inputs decreased the proportion of inorganic P (Pi) and increased that of organic P (Po) in the NaOH fraction, bound to aluminum and iron oxides. The results of nutrient (carbon, N, or P) addition indicated that acid phosphatase was synthesized to acquire P. This study suggests that, in this forest soil, P in the H2O-P + NaHCO3-P and in the NaOH-Pi fractions was available for soil microorganisms to decompose leaf litter and that increase in microbial activity eventually translated in an increase in the proportion of Po found in the NaOH fraction in this forest soil.

Measuring microbial fitness in a field reciprocal transplant experiment.

Microbial fitness is easy to measure in the laboratory, but difficult to measure in the field. Laboratory fitness assays make use of controlled conditions and genetically modified organisms, neither of which are available in the field. Among other applications, fitness assays can help researchers detect adaptation to different habitats or locations. We designed a competitive fitness assay to detect adaptation of Saccharomyces paradoxus isolates to the habitat they were isolated from (oak or larch leaf litter). The assay accurately measures relative fitness by tracking genotype frequency changes in the field using digital droplet PCR (DDPCR). We expected locally adapted S.paradoxus strains to increase in frequency over time when growing on the leaf litter type from which they were isolated. The DDPCR assay successfully detected fitness differences among S.paradoxus strains, but did not find a tendency for strains to be adapted to the habitat they were isolated from. Instead, we found that the natural alleles of the hexose transport gene we used to distinguish S.paradoxus strains had significant effects on fitness. The origin of a strain also affected its fitness: strains isolated from oak litter were generally fitter than strains from larch litter. Our results suggest that dispersal limitation and genetic drift shape S.paradoxus populations in the forest more than local selection does, although further research is needed to confirm this. Tracking genotype frequency changes using DDPCR is a practical and accurate microbial fitness assay for natural environments.

Hygroscopic properties of the litter of coniferous and deciduous stands in central Siberia

The hygroscopic properties of the litter of coniferous (larch and pine) and deciduous (aspen and birch) stands were studied in terms of isotherms of water-vapor sorption and with use of thermal analysis methods (TG, DSC). It was found that most of the monolayer capacity belongs to subhorizons OL and OF of the larch and pine forest litters. The larch plantation litter has the highest hydrophilicity. DSC results show that the water is most strongly associated with the litter substance in subhorizon OL in coniferous plantations and OH in deciduous ones. The moisture supply in the litter of coniferous stands is greater than in deciduous ones.

Saprotrophy of Conidiobolus and Basidiobolus in leaf litter

This study of the putative saprotrophs of Conidiobolus and Basidiobolus aids the understanding of their ecological roles in litter, and their relationship with the entomogenous fungi of the Entomophthorales. A total of 47 isolates (ten spp.) were screened for their ability to utilise pure compounds, arthropod cadavers, and plant leaf fragments as substrates. Isolates co-occurred in a larch plantation ( Larix sp.) or were from adjacent habitats. Of the 21 isolates (nine spp.) tested on potential prime carbon sources, none could utilise common plant structural polymers. Conidiobolus adiaeretus, C. iuxtagenitus, and B. ranarum from litter and some soil isolates of C. heterosporus, C. pumilus, and C. firmipilleus could use starches and glycogen. In marked contrast, all could utilise animal chitin, gelatine, casein, N-acetyl glucosamine, and trehalose. The lipids tributyrin and sunflower oil also supported growth. Conidia on cadavers usually led to high levels of colonisation as was the case for 30 isolates (ten species). Collembola were more frequently and rapidly colonised than mites. Cadavers of many other arthropods were also internally colonised. The ability to utilise cadavers of diverse arthropods indicates that trophic competition between co-occurring test species may be minimal. Niche differentiation may depend more on non-trophic features of their life history. Negative correlation of performance with the presence of naturally occurring, non-test fungi suggests competition with (or antibiosis from) at least some of the other fungi. In washed or unwashed plant fragments of larch litter (F-layer) only occasional local growth and resting spore formation occurred. Extra nutrients did not facilitate colonisation. Alternative forms of repetitional conidia showed a strong association with plant fragments but not with cadavers.

Trace element fractionation and transport in boreal rivers and soil porewaters of permafrost-dominated basaltic terrain in Central Siberia

The chemical status of ∼40 major and trace elements (TE) and organic carbon (OC) in pristine boreal rivers draining the basaltic plateau of Central Siberia (Putorana) and interstitial solutions of permafrost soils was investigated. Water samples were filtered in the field through progressively decreasing pore size (5 μm → 0.22 μm → 0.025 μm → 10 kDa → 1 kDa) using cascade frontal filtration technique. Most rivers and soil porewaters exhibit 2–5 times higher than the world average concentration of dissolved (i.e., <0.22 μm) iron (0.03–0.4 mg/L), aluminum (0.03–0.4 mg/L), OC (10–20 mg/L) and various trace elements that are usually considered as immobile in weathering processes (Ti, Zr, Ga, Y, REEs). Ultrafiltration revealed strong relationships between concentration of TE and that of colloidal Fe and Al. According to their partition during filtration and association with colloids, two groups of elements can be distinguished: (i) those weakly dependent on ultrafiltration and that are likely to be present as truly dissolved inorganic species (Li, Na, K, Si, Mn, Mo, Rb, Cs, As, Sb) or, partially (20–30%) associated with small size Fe- and Al-colloids (Ca, Mg, Sr, Ba) and to small (<1–10 kDa) organic complexes (Co, Ni, Cu, Zn), and (ii) elements strongly associated with colloidal iron and aluminum in all ultrafiltrates largely present in 1–100 kDa fraction (Ga, Y, REEs, Pb, V, Cr, Ti, Ge, Zr, Th, U). TE concentrations and partition coefficients did not show any detectable variations between different colloidal fractions for soil porewaters, suprapermafrost flow and surface streams. TE concentration measurements in river suspended particles demonstrated significant contribution (i.e., ⩾30%) of conventionally dissolved (<0.22 μm) forms for usually “immobile” elements such as divalent transition metals, Cd, Pb, V, Sn, Y, REEs, Zr, Hf, Th. The Al-normalized accumulation coefficients of TE in vegetation litter compared to basalts achieve 10–100 for B, Mn, Zn, As, Sr, Sn, Sb, and the larch litter degradation is able to provide the major contribution to the annual dissolved flux of most trace elements. It is hypothesized that the decomposition of plant litter in the topsoil horizon leads to Fe(III)-, Al-organic colloids formation and serves as an important source of elements in downward percolating fluids.

Gas Chromatographic Determination of Extractable Compounds Composition and Emission Rate of Volatile Terpenes from Larch Needle Litter

A combination of solid-phase microextraction (SPME) and gas chromatography can be successfully used both for establishing the qualitative composition of volatile organic compounds (VOC) emitted by leaf litter and for determining their emission rates. Taking as an example European larch litter, it is shown that “dead” plant material contains considerable amounts of volatile components as well as non-volatile compounds that can be VOC precursors formed as a result of enzymatic reactions. It is proposed to include the determination of extractable compounds into the methodology of studying litter as a source of atmospheric VOC. Some data on litter mass are reported and it is concluded that this data may be included into special models for emission evaluation. In this work the distribution coefficients of monoterpene hydrocarbons between the gas phase and polydimethylsiloxane fiber coating necessary for quantitative determinations in SPME were estimated.

Seasonal variation in CO2 production of leaf litter from different deciduous forests at the early decomposition stage

We collected leaf litter from a deciduous broadleaf forest and a larch forest in Hokkaido, Japan naturally without using litter traps or litter bags. The litter collection was conducted every month from October 2001 through October 2002 except in the snowy season. We measured the CO2 production rate of the litter samples through microbial respiration using the chamber method in a laboratory under different temperature and moisture conditions to investigate the seasonal pattern and temperature and moisture responses of CO2 production at the early stage of litter decomposition. Seasonal variation was found in the CO2 production rate per unit of litter dry weight (Pdw), or the litter decomposition rate, for both broadleaf and larch litters. Although seasonal patterns differed somewhat according to temperatures and species, Pdw reached the minimum in June. The moisture sensitivity of Pdw decreased with time and reached the minimum in summer for both broadleaf and larch litters, whereas the seasonal pattern of the temperature sensitivity (Q10) was not clear. The seasonal pattern of Pdw was explained by its C:N ratio for broadleaf litter. For larch litter, however, the relationship between Pdw and the C:N ratio was complicated because of fresh litterfall supplied gradually before defoliation. The temperature and moisture sensitivities of Pdw changed in parallel with the C:N ratio for both broadleaf and larch litters, respectively. These facts suggest the importance of litter chemical quality in the early decomposition process of fresh litter and the validity of the C:N ratio as an index of litter quality.

Description of Allothrombium triticium adult (Acari: Trombidiidae) from Iran

Two known species of the oribatid mite genus Epilohmannia, E. cylindrica (Berlese) and E. spathulata Aoki, are redescribed. E. cylindrica is recorded for the first time from Mongolia. Two new species, Epilohmannia spathuloides sp. nov. and Epilohmannia shtanchaevae sp. nov. are described from larch litter in YamanashiPrefecture (Mt. Yatsugatake), Central Japan and from deep soil in the mountain-steppe landscape of Central Mongolia, respectively. A key to the Japanese and Mongolian species of Epilohmanniidae is given.

The degradation of soil fertility in pure larch plantations in the northeastern part of China

Soil degradation was found in first generation of Dahurian larch ( Larix gmelinii (Rupr) Rupr.) plantations in northern China and also in plantations of other larch species such as Larix olgensis and Larix leptolepis in the same area. Soil degradation in pure larch plantations may be exacerbated in the second rotation under continuous cropping and was accompanied by obvious concomitant decrease in tree growth. A study on nutrient cycling revealed that poor quality of larch litter, which decomposed very slowly, was a key factor leading to soil degradation and decline in tree growth in pure larch plantations. The accumulation of forest floor litter in ∼20-year-old pure larch stands was 23–28 ton ha −1 and this was higher than 9–16 ton ha −1 in virgin mixed Korean pine/ broad-leaf forests. Larch litter took 4.4 years to mineralise, whereas angiosperm litter (ash, birch and poplar) in a pure larch stand took only 0.9–2.4 years. The progressive accumulation of litter on the forest floor acted as a heat-isolating layer which inhibited thermal conduction and decreased soil temperature and limited soil microbial activities. Consequently, degradation of soil fertility occurred and this was exacerbated after two or more rotations under continuous cropping. The role of the understorey vegetation was significant in nutrient recycling and maintaining sustainable soil fertility in larch plantations. A low-cost, effective way to prevent soil degradation in pure larch plantations is to develop mixed stands formed either by creating a mixture with broad-leaved trees or by introducing understorey vegetation (herbs and shrubs). Large areas of man-made, pure larch stands should be replaced by many small patches of different, uneven-age stands and crop rotation with different tree species should be adopted instead of continuous larch cropping.

Effect of bryophytes on survival of conifer seedlings in subalpine forests of central Japan

AbstractBryophytes form the major seedbed for coniferous trees in the subalpine forests of central Japan. Field experiments were conducted on the floor of a closed stand dominated by Tsuga on Mt Fuji to examine the seedling survival of Abies veitchii and Tsuga diversifolia in seven substrate types in relation to the morphological characteristics of the seeds and seedlings. Neither Abies nor Tsuga seedlings could survive on dwarf‐bamboo litter beyond 2 years after the seed rain. Abies seedlings survived not only in all types of bryophyte communities but also in larch litter. In contrast, the survival of Tsuga seedlings was restricted to communities of smaller‐statured bryophytes found on logs. The seeds and 1st year seedlings of A. veitchii were larger than those of T. diversifolia. Abies seedlings produced hypocotyls taller than any bryophyte community and radicles which were long enough to penetrate into the moist humus layer, whereas Tsuga seedling radicles presumably penetrate into humus only in bryophyte communities forming a thin mat on logs. The effect of bryophytes on survival of tree seedlings therefore depends on the relationships between the morphology of seeds and seedlings and the structure of bryophyte communities.

The effect of tree leaf litter on sward botanical composition and growth

Freshly fallen leaf litter of sycamore and hybrid larch was applied in November to a variety of different swards including perennial ryegrass-white clover swards and white clover monocultures. Sycamore litter reduced ryegrass in the mixed sward and clover in the monoculture the following February. Although clover had returned to control levels by March, ryegrass remained suppressed. Herbage weight in the mixed sward was reduced as was clover stolon length in the monocultures. The effect appeared to be due to a smothering of the sward. In contrast larch litter had much less effect on the sward with only temporary reductions in grass and clover. In addition there was a general increase in herbage weight and clover stolon length in larch treatments. This apparent stimulation of the sward by larch litter does not appear to be a result of nutrients leaching from the decomposing litter. Larch litter made net gains in N, P and K whilst sycamore litter exhibited a net loss of P and K. It is suggested that differences seen between the two litter treatments are as a result of different leaf form: larch needles by settling at ground level did not smother the sward to the same extent as the broadleaved sycamore and so may have afforded some insulatory protection for the overwintering stolons.

Quantitative survey of Conidiobolus and Basidiobolus in soils and litter

For 22 months, habitats (hayfield, wheatfield, larch plantation) were sampled at intervals of several weeks for Conidiobolus and Basidiobolus by canopying samples over 2% malt agar. Some four hundred and thirty isolates were obtained which grouped into sixteen species. Frequency of occurrence in samples (based on proportion of total isolates) showed an overall preponderance' of Basidiobolus ( ca 44%). C. firmipilleus (20%), C. coronatus (12%) and a presumptive new species ‘alpha-new’ were the most frequent Conidiobolus . Each of the other twelve species accounts for < 5% of isolates. Marked differences in levels of mean SDU's per sample were found according to species and habitat. Basidiobolus spp., C. firmipilleus and alpha-new clearly predominated in the hayfield, wheatfield and larch litter respectively. The preliminary seasonal records were examined in relation to climatological data, farming operations and gross habitat features.

Larch litter and nitrogen availability in mixed larch–spruce stands. II. A comparison of larch and spruce litters as a nitrogen source for Sitka spruce seedlings

On deep peat sites where available N levels are low, the growth and N status of Sitka spruce are improved when the species is grown in mixed larch–spruce (75/25%) stands. It has been suggested that larch litter mineralizes more readily than other coniferous litters, thereby increasing N availability in mixed stands. However, while larch litter was demonstrated to release N more readily than spruce litter, the amount of N contained in larch litter fall seems too low to be of quantitative importance.

Larch litter and nitrogen availability in mixed larch–spruce stands. I. Nutrient withdrawal, redistribution, and leaching loss from larch foliage at senescence

The growth and N status of Sitka spruce on deep peat sites low in available N is improved in the presence of larch. It has been suggested that larch stimulates N mineralization because of high N concentrations in its litter and the large N input resulting from its annual litter fall. However, while larch foliar N concentrations were shown to be high, marked withdrawal and storage in other tree components resulted in a relative and absolute impoverishment of the litter. P and K could be leached from senescing foliage in relatively large amounts, but the potential loss of N was low. Field measurements of throughfall substantiated this finding. Larch seemed extremely conservative in its use of N, suggesting that larch litter does not directly enhance N availability in mixed stands.