Broadleaf Litter Research Articles

Peluang Penggunaan Gel dalam Pengendalian Kebakaran Hutan dan Lahan

The recurring issue of forest and land fires, especially during the dry season, poses a persistent challenge in Indonesia. Conventional firefighting efforts using water as the primary extinguishing agent have not proven entirely effective in preventing and reducing the extent of burned areas. This research aims to explore the potential use of gel as an alternative in combating forest and land fires. The research methodology involves preparation, oven testing, burning experiments, as well as observation and evaluation. Various fuel types, including needle leaf litter, broadleaf litter, and understory litter, were examined along with Gel Pack Extinguishing Agent (GPEA) at varying doses (0g/100ml water, 1g/100ml water, 2g/100ml water, and 3g/100ml water). The results indicate significant differences with the highest efficiency observed at a dose of 1g/100ml water for needle leaf litter, 2g/100ml water for broadleaf litter, and 1g/100ml water for understory litter.
 Keywords: forest and land fires, Gel Pack Extinguishing Agent, extinction

Aquatic hyphomycete assemblages of Abies sachalinensis leaf litter immersed in a stream in Hokkaido, Japan

ABSTRACT Aquatic hyphomycetes are key decomposers of plant-litter in freshwater environments. Previous studies have shown that conifer needles are colonized less frequently by aquatic hyphomycetes than broad-leaf species. Sakhalin fir (Abies sachalinensis) is the most common coniferous tree species planted for timber production in Hokkaido, Japan. Herein, we investigated aquatic hyphomycete assemblages involving Sakhalin fir needle litter and compared them with those of broad-leaf tree species, including Japanese oak (Quercus crispula) and Japanese linden (Tilia japonica), during immersion in a stream. Seventy percent of the total fungal species observed in fir needles were also observed in broad-leaf litter. However, the structure of the aquatic hyphomycete assemblages differed between the fir and two broad-leaf species, especially in the middle to late stages of the immersion period. The increase in species number and conidia number in fir needles was slower than that in oak leaves in the early stages of the immersion period. However, they continued to increase rapidly relative to the broad-leaf tree litter during the middle stages of the immersion period. These results suggest that fir needle litter was not difficult for aquatic hyphomycetes to colonize in the middle to late stages of the immersion period.

Long-term effects on water chemistry and macroinvertebrates of selective thinning along small boreal forest streams

The maintenance of narrow strips of trees (forest buffers) along the shorelines of surface water bodies during logging is a common measure to protect freshwater habitats. The functionality of forest buffers may be improved by actively managing the streamside forest early in the rotation for their eventual function as buffers, including by increasing the proportion of broadleaf trees in spruce-dominated stands. In this study, long-term effects of different selective thinning regimes along two small forest streams were investigated in south-central Sweden. In a young coniferous forest, a c. 10 m-wide band along the streams was selectively thinned in 1998 to create a band with purely broadleaf trees along one of the streams and purely conifers along the other. Forest stand characteristics, water chemistry and benthic macroinvertebrates data were collected during 1996–2003 (before and after selective thinning). The streams were re-investigated 20–22 years after thinning, together with three streams representing operational forest management. The forest adjacent to all five streams was inventoried and litterfall, stream water chemistry, and benthic macroinvertebrates composition were monitored between spring and late autumn during 2018–2020. Twenty years after thinning, the thinned bands beside the streams were still dominated by either broadleaf trees or conifers, depending on the stream. Over the longer term, the differences in water chemistry between the streams with selective thinning were mainly related to lower pH, ANC, Tot-P and Tot-N concentrations in the stream bordered by mainly broadleaf trees. Analysis of benthic macroinvertebrates was based on environmental quality indices (ASPT and EPT), diversity and abundance metrics, and relative abundances of functional feeding groups. Streams with higher broadleaf litter inputs tended to score better on the ASPT and EPT indices than those with lower broadleaf inputs, as well as supporting higher relative abundances of one or more groups of invertebrate detritivores (leaf shredders, collector-gatherers and/or passive filter feeders). This suggests that management of the density of broadleaf trees beside these streams might support higher ecological status and will support a greater proportion of detritivores in benthic food webs.

Assessment of macro-invertebrates’ colonization in the context of impacts of exotic and native broadleaf litter species in Ethiopia

Assessment of macro-invertebrates’ colonization in the context of impacts of exotic and native broadleaf litter species in Ethiopia

Global pattern and drivers of stable residue size from decomposing leaf litter

Stable residue from decomposing leaf litter is related to humus buildup in the forest floor and thus to the accumulation of carbon in the soil organic layer (OLC). However, the global pattern and controls of stable residue size remains poorly understood. Herein, the spatial pattern of stable residue size and its association with a series of potential drivers were evaluated by synthesizing available data worldwide. The results showed that stable residue size had a significant and positive correlation with the litter initial nitrogen (N) and lignin concentrations, and a negative correlation with the initial manganese concentration. Larger stable residues were found from decomposing broadleaf litter vs. coniferous litter. The decomposition of green leaf litter produces an equal amount of stable residue as that of brown litter. Stable residue size correlated quadratically with mean annual temperature and latitude, and linearly with mean annual precipitation. Methodological factor also matters, because stable residue size decreased as field incubation time increased. The boosted regression tree model indicated that litter initial traits have the most explanative ability for the variance in stable residue size. We highlighted that litter initial traits exert a predominant role over climate in shaping the stable residue size globally. Our findings are beneficial for a more accurate prediction of global-scale OLC accumulation.

Drivers of contrasting boreal understory vegetation in coniferous and broadleaf deciduous alternative states

AbstractAlternative states defined by tree‐canopy dominance result in different ecosystem functioning and shape habitat conditions for the understory vegetation. One example in the boreal forest is the alternation between broadleaf deciduous and coniferous forests. Disturbances related to natural fires and human land uses have produced changes in tree‐canopy dominance in the boreal region where coniferous forests change to broadleaved forests, affecting understory community dynamics and their related ecosystem processes and functions. To analyze the factors driving changes in understory vegetation and the resistance of its vegetation to shifts between alternative states, we compared the effects of changes in the system between two contrasting boreal forest types (black spruce vs. trembling aspen) in adjacent stands with similar topoedaphic conditions. We performed a 5‐year in situ experiment using alternative states as a theoretical framework including two approaches: (1) the ecosystem approach, manipulating environmental conditions of light, litter, and nutrients in each forest type to determine the main mechanisms associated with tree‐canopy dominance that affect the diversity and composition of understory communities; and (2) the community approach, physically exchanging understory communities between alternative states, to determine their resistance under a new tree‐canopy dominance through time, as well as the resilience of the forest understory after a small‐scale disturbance. Results indicate that the understory vegetation of trembling aspen forests were resistant through time both after changes in local conditions in the ecosystem approach and in the new black spruce‐dominated alternative state in the community approach. In contrast, mosses and ericaceous plants that typically dominate the forest floor of black spruce forests were negatively affected by the physical effect of broadleaf litter addition in our ecosystem approach and they were not resistant when transplanted to trembling aspen forests in the community approach, as they decreased in abundance and were invaded by aspen understory community species over time. The understory vegetation is a key forest ecosystem driver that can contribute to maintain the resilience of the boreal system and help to preserve their ecosystem services, which is a key aspect to consider in forest management faced with the effects of climate change.

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

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

Leaf litter combustion properties of Central European tree species

AbstractTemperate forests of Central Europe are exposed to increasing fire risk. However, little is known about combustion properties of leaf litter, which plays an important role in the spread of surface fires. We used cone calorimetry to compare combustion properties of leaf litter samples from seven common tree species of Central European forests by reconstructing a litter layer of original depth in sample holders with a size of 10 cm × 10 cm. In addition to mono-specific leaf litter beds, combustion experiments included mixtures of different litter types, mixtures of litter and bryophytes and one mixture of litter and fine woody debris, totalling to 13 different setups (i.e. litter types). Recorded combustion properties included ignitability, flaming duration and heat release. Differences in combustion properties were analysed using analyses of variance followed by pairwise post-hoc tests. Combustion properties mainly differed between different litter types (broadleaf, pine needle, short needle). Highest total and peak heat release were observed for Scots pine (Pinus sylvestris), while peak heat release rates showed only minor differences for litter of the remaining species. Broadleaf litter was characterized by highest ignitability. For short-needle litter, we observed long flaming duration and incomplete combustion, resulting in the lowest total heat release on a sample mass basis. For litter mixtures of pine and broadleaf litter, we observed lower peak heat release rates in comparison to mono-specific pine litter. Mosses reduced peak heat release rates and increased the proportion of unburned biomass. However, the magnitude of this effect differed between bryophyte species included in the mixtures. The addition of fine woody debris strongly increased total heat release, highlighting the importance of fine woody fuels for fire behaviour. The results of this study provide valuable baseline information on combustion behaviour of leaf litter from Central European forests. Due to the limitations of laboratory combustion experiments to reproduce conditions of real forest fires, there is a need for future field studies investigating fire behaviour under natural conditions.

Potential for significant precipitation cycling by forest‐floor litter and deadwood

AbstractThe forest‐floor litter layer can retain substantial volumes of water, thus affecting evaporation and soil‐moisture dynamics. However, litter layer wetting/drying dynamics are often overlooked when estimating forest water budgets. Here, we present field and laboratory experiments characterizing water cycling in the forest‐floor litter layer and outline its implications for subcanopy microclimatic conditions and for estimates of transpiration and recharge. Storage capacities of spruce needle litter and beech broadleaf litter averaged 3.1 and 1.9 mm, respectively, with drainage/evaporation timescales exceeding 2 days. Litter‐removal experiments showed that litter reduced soil water recharge, reduced soil evaporation rates, and insulated against ground heat fluxes that impacted snowmelt. Deadwood stored ~0.7 mm of water, increasing with more advanced states of decomposition, and retained water for >7 days. Observed daily cycles in deadwood weight revealed decreasing water storage during daytime as evaporation progressed and increasing storage at night from condensation or absorption. Water evaporating from the forest‐floor litter layer modulates the subcanopy microclimate by increasing humidity, decreasing temperature, and reducing VPD. Despite the relatively small litter storage capacity (<3.1 mm in comparison to ~102 mm for typical forest soil rooting zones), the litter layer alone retained and cycled 18% of annual precipitation, or 1/3 of annual evapotranspiration. These results suggest that overlooking litter interception may lead to substantial overestimates of recharge and transpiration in many forest ecosystems.

Tree species identity and mixing ratio affected the release of several metallic elements from mixed litter in coniferous-broadleaf plantations in subtropical China

Planting broadleaf trees in coniferous forests has been shown to promote biogeochemical cycling in plantations; however, how species mixing influences litter decomposition and release of metallic elements from mixed coniferous-broadleaf litter remains unclear. An in situ litter decomposition experiment was conducted to examine the effect of 1) a mixture from coniferous litter (Pinus massoniana) with different individual broadleaved litter (Bretschneidera sinensis, Manglietia chingii, Cercidiphyllum japonicum, Michelia maudiae, Camellia oleifera) and 2) their mixing ratio (mass ratios of coniferous and broadleaf litter of 5:5, 6:4 and 7:3) on the release of metallic elements [calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn)] during litter decomposition. We found that the identity of the broadleaf tree species in the mixed litter and the mixing ratio affected the release rates of metallic elements (p < 0.05). After one year of decomposition, K, Mg, Mn and Zn were released, while Na, Ca, Fe and Cu accumulated in the mixed litter. Mixing increased the release of K, Ca, Na, Mg, Fe, Mn, Cu and Zn in more than one-third of the samples, but inhibited the release of K, Fe and Mn in less than 14% of the samples. Increasing the mixing ratio of coniferous to broadleaf litter enhanced the release of Na, Fe, Mn and Zn but decreased the release of Ca and Mg. Overall, these results highlight that mixed litter, particularly tree species identity and mixing ratio, can alter the release and enrichment of metallic elements during litter decomposition, thereby affecting the cycling of metallic elements in plantations with different species compositions.

Meta-Analysis of Effects of Forest Litter on Seedling Establishment

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

Description of a new species of Gerhardtia (Lyophyllaceae, Agaricales) from Japan based on morphological and molecular phylogenetic analyses and live culture characteristics.

We describe a new species of Gerhardtia from Japan based on basidiomata morphology, live culture characteristics, and molecular phylogenetic analyses. Gerhardtia venosolamellata is found on broad-leaf litter, and is characterized by tricholomatoid to marasmioid basidiomata, an off-white to pale salmon-pink pileus surface with faint marginal striae, subdistant lamellae with lateral veins, a tomentose to strigose stipe base with hyphal strands generating arthroconidia measuring 4-7 × 2-3 µm, cyanophilic, elongate-ellipsoid to cylindrical, slightly verrucose or undulate basidiospores measuring 4.5-6 × 2.5-3 µm, and cyanophilic basidia measuring 25-35 × 5-6 µm and containing siderophilous granules. Phylogenetic analyses based on the internal transcribed spacer and large subunit regions of the fungal nrDNA indicates that G. venosolamellata is related to G. sinensis and G. highlandensis, but differs from the former with respect to basidiomata color, basidiospore shape, and habitat. An isotype specimen of G. highlandensis exhibited relatively close lamellae without veins, and slightly larger basidiospores (4.5-6.5 × 2.5-3 µm). Cultured mycelia of G. venosolamellata produced arthroconidia measuring 4.5-8.5 × 2.5-3 µm with both schizolytic and rhexolytic secession on MA and PDA media, and chlamydospores occasionally covered with crystals on MA and MYG media.

Nitrogen deposition stimulates decomposition via changes in the structure and function of litter food webs

Nitrogen (N) deposition poses a threat to terrestrial biodiversity and ecosystem functioning globally. However, little is known concerning how the structure and function of litter fauna communities will respond in this context. Here, a gradient of N deposition (0, 20, and 40 kg N ha−1 yr−1) was simulated in a subtropical forest of southwestern China, to assess the potential effects of increased N deposition on the trophic structure and functioning of fauna communities in decomposing leaf litters of three main subtropical plant functional groups covering a total of 18 species: six evergreen broadleaf, six deciduous broadleaf, and six coniferous trees. We found that N addition shifted the trophic structure of fauna communities in decomposing litter, and different fauna feeding guilds showed distinct response patterns. Specifically, N addition increased the abundance of predators, decreased the abundance of omnivores, while detritivores were less affected. Compared to deciduous broadleaf and coniferous litters, evergreen broadleaf litter had less complex structure of fauna communities, but it decomposed slower. Further, structural equation modeling (SEM) showed that N addition increased litter decomposition in part via changing the trophic structure of fauna communities, with a positive correlation between predators and detritivores being associated with higher decomposition. As omnivores often exhibit top-down pressure on all other trophic guilds in (sub-)tropics, our observed shifts in trophic structure and litter decomposition might be partly due to the N addition-induced declines in omnivorous ant population. Future studies should investigate the role of bottom-up and top-down forces between detritivores, predators, and omnivores in driving litter decomposition. Collectively, our findings suggest that (i) N deposition consistently shifts the trophic structure of fauna communities across litter types, and (ii) such a shift further translate into changes in the functioning of subtropical forest ecosystems.

Does Mixing Tree Species Affect Water Storage Capacity of the Forest Floor? Laboratory Test of Pine-Oak and Fir-Beech Litter Layers

During the last decade, tree species mixing has been widely supported as a silvicultural approach to reduce drought stress. However, little is known on the influence of tree species mixing on physical properties and the water storage capacity of forest soils (including the forest floor). Thus, the study aimed to analyze the effect of mixing pine needles and oak leaves and mixing fir needles and beech leaves on hydro-physical properties of the litter layer during laboratory tests. We used fir-beech and pine-oak litter containing various shares of conifer needles (i.e., 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%) to determine the influence of the needle admixture on bulk density, total porosity, macroporosity, water storage capacity, the amount of water stored in pores between organic debris and the degree of saturation of mixed litter compared to broadleaf litter (oak or beech). We found that the admixture of fir needles increased the bulk density of litter from 7.9% with a 5% share of needles to 55.5% with a 50% share (compared to pure beech litter), while the share of pine needles &lt; 40% caused a decrease in bulk density by an average of 3.0–11.0% (compared to pure oak litter). Pine needles decreased the water storage capacity of litter by about 13–14% with the share of needles up to 10% and on average by 28% with the 40 and 50% shares of pine needles in the litter layer. Both conifer admixtures reduced the amount of water stored in the pores between organic debris (pine needles more than fir needles).

Effects of weeding the shrub layer during thinning on surface soil erosion in a hinoki plantation

Unmanaged dense hinoki (Chamaecyparis obtusa) plantations in Japan tend to suffer from severe surface soil erosion. Thinning plays an important role in soil conservation through development of understory vegetation. To examine the possibility that the weeding conducted during thinning enhances surface soil erosion, we investigated splash detachment, pedestal height, forest floor cover and throughfall for four different experimental treatments, testing thinning and weeding and the combination of thinning and weeding in a hinoki plantation. High splash detachment was observed for weeding treatments. Generalized linear mixed modeling results suggest that weeding increases splash detachment. This increase in splash detachment is caused by clearing shrubs that have a low enough height to decrease the impact of rainfall. For the same treatment type, low forest floor cover was also observed in the first year after weeding due to the decline of litter cover. Broadleaf litter fall was decreased by weeding, although forest floor vegetation cover was similarly low for all treatments in the first year. These results suggest that weeding conducted during thinning promotes splash erosion in hinoki plantations.

Hardwood mixture enhances soil water infiltration in a conifer plantation

Soil hydraulic properties affect soil infiltration capacity. Limited information is available about how hardwood mixture influences water infiltration in conifer plantations through its effects on soil hydraulic properties. We evaluated how, and to what extent, infiltration rates were affected by abiotic and biotic conditions along gradients of abundance and diversity of hardwoods and abundance of understory plants in nine stands representing three replicates of three different thinning intensities (unthinned [Control], 33% thinning [Weak], and 67% thinning [Intensive]) in a Cryptomeria japonica (Thunb. ex L. f.) D. Don plantation. Correlation analyses and a structural equation model (SEM) indicated that infiltration rates were enhanced by hardwood mixture (i.e., abundance and species richness of hardwoods) and abundance of understory plants, via increases in the fine root density and accumulation of broadleaf litter, because the fine root density decreased soil bulk density and accumulation of litter increased the porosity and both of which greatly improved the soil hydraulic conditions. In the Intensive treatment, complementarity effects stemming from vertical partitioning of resource acquiring organs (i.e., leaves) among species might have increased accumulation of broadleaf litter. If increased volumes of broadleaf litter promote increased earthworm abundance, earthworms may in turn cause higher porosity, because the burrowing activity of earthworms increases the number of macropores. Consequently, hardwood mixture with abundant understory plants promotes increased infiltration rates. Our results demonstrate that intensively thinned stands with an abundance and diversity of hardwoods, including broadleaf understory plants, can absorb and store more water compared to lightly thinned stands with only understory plants, owing to increased soil infiltration capacity. Our results point to the importance of hardwood mixture in enhancing ecosystem functioning in conifer plantations.

Radiocesium leaching from litter during rainstorms in the Fukushima broadleaf forest

Forests are important sources of dissolved radiocesium (137Cs) discharge downstream. To improve understanding of dissolved 137Cs discharge processes during rainstorms, we investigated the relationship between rainfall-runoff hydrological processes and the discharge of 137Cs leached from litter. Leaching tests were conducted with broadleaf litter collected in the area where saturated overland flow was generated during rainstorms in a broadleaf-tree-dominated forest. According to the leaching test results, the 137Cs leaching rate was higher in the early stage of the test and decreased afterward. There was no significant difference in the overall results between the agitation and non-agitation cases. The 137Cs leaching rate from litter after the 24-h test was up to 33.7%. A large proportion of the original 137Cs activity was present even after the tests, as leaching from litter during rainstorms in the headwater area could be an additional source of dissolved 137Cs in the stream water. If mixing of 137Cs originating from groundwater, soil water, and rainfall with the hydrological processes is assumed, differences between the observed and estimated 137Cs in the surface runoff water became larger under high flow conditions. This analysis indicates additional 137Cs loading on surface runoff water during rainstorms, where saturated surface area can expand as the surface runoff rate increases. Contact area between surface runoff and litter accumulated on the forest floor should increase and accelerate 137Cs leaching from the litter. Therefore, 137Cs leaching in the saturated surface area that is temporarily formed during rainstorms can play a principal role in dissolved 137Cs discharge during rainfall-runoff events. Contaminated litter in the temporally saturated region of forested headwaters is an important factor contributing to elevated levels of dissolved 137Cs during rainstorms in the Fukushima area.

Nitrogen addition and plant functional type independently modify soil mesofauna effects on litter decomposition

Soil fauna plays a crucial role in plant litter decomposition. However, if and how increasing nitrogen (N) deposition and plant functional type jointly affect the contribution of soil mesofauna to litter decomposition remains poorly understood. A litterbag experiment with two meshed sizes (0.1 and 2 mm) was conducted to examine the effects of soil mesofauna on litter decomposition of three coexisting functional types of trees (evergreen broadleaf, deciduous broadleaf and coniferous) differing in litter identity (6 tree litter species for each plant functional type). Litterbags were exposed to three N addition levels (0, 20 and 40 kg N ha−1 yr−1) in a subtropical forest of southwest China. Overall, soil mesofauna significantly increased litter mass loss with the most profound effect in evergreen broadleaf litter. Further, the high N addition treatment stimulated the effects of soil mesofauna on litter decomposition, particularly in deciduous broadleaf litter. Soil mesofauna effects were positively correlated with initial leaf litter chemical characteristics, such as carbon and cellulose concentration and C/P ratio. The N effect was greater in low N than high N treatments in the 0.1 mm litterbags, but was similar in the two N addition levels in the 2 mm litterbags. Our results indicate that soil mesofauna effects on litter decomposition at low N addition are higher in evergreen broadleaf than in deciduous broadleaf and coniferous litter, and generally increase with N addition levels, particularly in deciduous litter species. The findings underscore the importance of soil mesofauna and plant functional types for litter decomposition in subtropical forests where N deposition is substantially increasing.

Responses of Soil Organic Carbon Mineralization and Microbial Communities to Leaf Litter Addition under Different Soil Layers

The mechanism of how soil carbon pools change when coniferous forests are converted into conifer-broadleaf mixed forests is poorly understood. In this study, the impact of additional carbon inputs on soil organic carbon mineralization and microbial communities was evaluated. In a microcosm incubation experiment, three types of 13C-labeled litter (Pinustabulaeformis (PT), Robiniapseudoacacia (RP), and a mixture of PT and RP (1:1, PR)) were added in to top (0–20 cm) and deep (60–80 cm) soil collected from a Chinese pine plantation. The priming effect (PE) and specific microbial groups involved in PE were studied. PT and RP addition to topsoil induced a negative PE. In deep soil, the decomposition rates of soil organic matter (SOM) after adding PT and mixture increased by 16.6% and 34.6% compared to those without litter. The addition of RP with a lower C:N ratio had a stronger negative PE than adding PT or mixture. Moreover, the PE in deep soil was more intense after all litter additions. In topsoil, the litter-derived carbon was mainly incorporated into 16:0, 18:1ω9c, and 18:1ω7c fatty acids. In conclusion, the addition of broadleaf litter into coniferous plantations might be beneficial for enhancing deep soil carbon stocks.

亚热带森林凋落叶分解过程土壤节肢动物群落的变化特征

土壤动物群落结构和多样性可能随凋落物分解进程和基质质量的变化不断改变。为了解亚热带森林凋落叶分解过程中土壤节肢动物群落变化特征，以四川盆地亚热带森林麻栎（Quercus acutissima）和柳杉（Cryptomeria fortunei）凋落叶为对象，于2011-2015年采用分解袋法研究了2种凋落叶分解过程中土壤节肢动物组成、结构和多样性动态变化。整个研究期间，柳杉和麻栎凋落叶分解袋中共捕获土壤节肢动物3855只，分属于16目51科，且均以等节跳科和棘跳科为优势类群；麻栎凋落叶中土壤节肢动物的个体密度随分解进程呈现增加趋势，在分解的1079天达最高值后降低，而柳杉凋落叶则在分解的156天急剧增加后快速降低，2种凋落叶中土壤节肢动物类群数量具有相似的动态变化过程；2种凋落叶中土壤节肢动物总体以菌食性数量比例最高，腐食性最低，且随凋落叶分解进程，植食性土壤节肢动物占比明显下降，菌食性则上升；非度量多维尺度（NMDS）分析显示，2种凋落叶中土壤节肢动物群落组成具有显著差异，聚类分析表明，2种凋落叶土壤节肢动物群落结构相似性随分解进程不断降低。亚热带森林凋落叶分解过程中土壤节肢动物群落组成、结构和多样性受凋落叶类型影响。;Soil fauna are crucial decomposers in terrestrial ecosystem. The structure and diversity of soil fauna may vary with changes in decompsition stages and litter quality during litter decomposition, but how the compositon and structure of soil arthropod vary during litter decompostion in subtropical forests remain poorly understood. In this study, we conducted a four-year litter decomposition experiment (2011-2015) to explore the compositon, structure and diversity of soil arthropod during litter decomposition. Two dominant tree species with contrasting leaf traits (coniferous vs. broadleaf) were used for field incubation in a subtropical forest of Sichuan Basin, southwestern China. Fresh senesced litter was collected using 1m×1 m litter traps in our study site between September and October 2011. The litter contained a coniferous species (Cryptomeria fortunei) and a broadleaf species (Quercus acutissima). The litter samples were air-dried for 2 weeks at 25℃ and 10±0.05 g was placed in 20 cm×20 cm nylon litterbags. A total of 130 litterbags (11 sampling times×5 plots×2 tree speices+20 spare litterbags) were carefully placed on the forest floor in late November 2011. A total of 11 sampling events were performed during our four-year litter decomposition study. Throughout the four years of decomposition, 3855 individuals and 51 families of soil arthropod were extracted from the litterbags. According to the individual proportion and composition of the taxa, Isotomidae and Onychiuriclae were the two numerically dominant taxa regardless of tree species during the decompositon. The individual density of the soil arthropod in the broadleaf litter showed an increasing trend with the decomposiotn proceeded and reached the maximum level at 1079 days of decomposition, and that in the coniferous litter increased to the maximum level at 156 days of decomposition and then rapidly decreased. The family richness of the soil arthropod in both the broadleaf and coniferous litter had a similar dynamic during litter decompostion. The fungivorous and saprophyte soil arthropod were the highest and least proportion of funcational groups of soil arthropod during the decompostion, respectively. As the decompsition proceeded, the proportion of the phytophaga soil arthropod decreased and that of the fungivorous soil arthropod increased. The NMDS analysis showed that the composition of soil arthropod community had sigificant difference between the broadleaf and coniferous litter. The cluster analysis indicated that the similarityof soil arthropod community structure between the broadleaf and coniferous litter continued decrease during the study. The results suggest that the composition, structure and diversity of soil arthropd are affected by litter type during litter decomposition in subtropical forests.