Search Results (21)

Headwater streams serve as a crucial link between forest and downstream aquatic ecosystems and also act as crucial agents in carbon (C) and nutrient storage and flux. These aquatic systems play a pivotal role in regulating biogeochemical cycles. Plant litter is an important contributor of nutrients to headwater streams, having significant impacts on downstream ecosystems. However, current research predominantly focuses on the dynamics of plant litter C and nutrients such as nitrogen and phosphorus, and we know little about those of nutrients such as sodium (Na). In this study, we conducted a comprehensive evaluation of the annual dynamics of plant litter Na storage within a subtropical headwater stream. This study took place over a period of one year, from March 2021 to February 2022. Our results showed that (1) the average annual concentration and storage of litter Na was 538.6 mg/kg and 2957.6 mg/m², respectively, and litter Na storage exhibited a declining trend from stream source to mouth, while demonstrating significantly higher values during the rainy season compared to the dry season; (2) plant litter type had significant impacts on Na concentration and storage, with leaf, twig, and fine woody debris accounting for the majority of litter Na storage; and (3) hydrological (precipitation, discharge) and physicochemical (water temperature, flow velocity, pH, dissolved oxygen, alkalinity) factors jointly affected Na storage patterns. Overall, the results of this study clearly reveal the dynamic characteristics of Na storage in plant litter in a subtropical forest headwater stream, which contributes to a more comprehensive understanding of the role of headwater streams in nutrient cycling and the dynamic changes of nutrients along with hydrological processes. This research will enhance our predictive understanding of nutrient cycling at the watershed scale. Full article

Nitrogen deposition can significantly impact soil biogeochemical cycling; however, its effects on the decomposition processes and nutrient release from leaf and twig litter in subtropical plantations remain inadequately understood. In this study, we focused on the Pinus yunnanensis Franch. forest in the central Yunnan Plateau, southwestern China, and explored how nitrogen addition influences litter decomposition nutrient release over two years, under four levels: control (CK, 0 g·m⁻²·a⁻¹), low nitrogen (LN, 10 g·m⁻²·a⁻¹), medium nitrogen (MN, 20 g·m⁻²·a⁻¹), and high nitrogen (HN, 25 g·m⁻²·a⁻¹). The results indicate that after 24 nitrogen application treatments, the rates of remaining mass in both leaf and twig litters followed the pattern: LN < CK = MN < HN. Under all nitrogen application treatments, the rate of remaining mass in leaf litters was significantly lower than that of twig litters (p < 0.05). Under LN, the mass retention in leaf and twig litters decreased by 3.96% and 8.41%, respectively, compared to CK. In contrast, under HN treatments, the rates of remaining mass in leaf and twig litters increased by 8.57% and 5.35%, respectively. This demonstrates that low nitrogen accelerates decomposition, whereas high nitrogen inhibits it. Significant differences in the remaining amounts of lignin and cellulose in both leaf and twig litters were observed when compared to CK (p < 0.05). Additionally, decomposition time and nitrogen deposition had significant effects on the remaining rates of nutrients (C, N, P) and their C/N, C/P, and N/P in litters (p < 0.05). Following nitrogen application, the C/N of the litters significantly reduced, while the N/P increased. The results suggest that nitrogen addition alleviates the nitrogen limitation on the litters while intensifying the phosphorus limitation. Full article

Characterization of fungal spider pathogens lags far behind their insect counterparts. In addition, little to nothing is known concerning the ecological reservoir and/or fungal entomopathogen community surrounding infection sites. Five infected spider cadavers were identified in the neo-tropical climate of north-central Florida, USA, from three of which viable cultures were obtained. Multi-locus molecular phylogenetic and morphological characterization identified one isolate as a new Gibellula species, here named, Gibellula floridensis, and the other isolates highly similar to Parengyodontium album. The fungal entomopathogen community surrounding infected spiders was sampled at different habitats/trophic levels, including soil, leaf litter, leaf, and twig, and analyzed using ITS amplicon sequencing. These data revealed broad but differential distribution of insect-pathogenic fungi between habitats and variation between sites, with members of genera belonging to Metarhizium and Metacordyceps from Clavicipitaceae, Purpureocillium and Polycephalomyces from Ophiocordyceps, and Akanthomyces and Simplicillium from Cordycipitaceae predominating. However, no sequences corresponding to Gibellula or Parengyodontium, even at the genera levels, could be detected. Potential explanations for these findings are discussed. These data highlight novel discovery of fungal spider pathogens and open the broader question regarding the environmental distribution and ecological niches of such host-specific pathogens. Full article

Litter decomposition is a crucial biochemical process regulated by microbial activities in the forest ecosystem. However, the dynamic response of the fungal community during litter decomposition to vegetation changes is not well understood. Here, we investigated the litter decomposition rate, extracellular enzyme activities, fungal community, and nutrient cycling-related genes in leaf and twig litters over a three-year decomposition period in a pure Liquidamabar formosana forest and a mixed L. formosana/Pinus thunbergii forest. The result showed that during the three-year decomposition, twig litter in the mixed forest decomposed faster than that in the pure forest. In both leaf litter and twig litter, β-cellobiosidase and N-acetyl-glucosamidase exhibited higher activities in the mixed forest, whereas phosphatase, β-glucosidase, and β-xylosidase were higher in the pure forest. The fungal α-diversity were higher in both litters in the pure forest compared to the mixed forest, with leaf litter showing higher α-diversity than twig litter. Fungal species richness and α-diversity within leaf litter increased as decomposition progressed. Within leaf litter, Basidiomycota dominated in the mixed forest, while Ascomycota dominated in the pure forest. Funguild analysis revealed that Symbiotroph and ectomycorrhizal fungi were more abundant in the mixed forest compared to the pure forest. In the third-year decomposition, genes related to phosphorus cycling were most abundant in both forests, with the pure forest having a higher abundance of cex and gcd genes. Fungal community structure, predicted functional structure, and gene composition differed between the two forest types and between the two litter types. Notably, the fungal functional community structure during the first-year decomposition was distinct from that in the subsequent two years. These findings suggest that dominant tree species, litter quality, and decomposition time all significantly influence litter decomposition by attracting different fungal communities, thereby affecting the entire decomposition process. Full article

Nitrogen (N) deposition influences litter decomposition and its water-holding capacity in forest ecosystems. Water conservation remains a priority, so understanding these interactions is vital for managing forests, especially in the Yunnan Plateau region. This study aimed to investigate the effects of simulated N deposition on litter decomposition and water-holding capacity in the Evergreen broad-leaf and Quercus aquifolioides forest in the central Yunnan Plateau. Indoor flooding experiments were performed alongside varied nitrogen deposition treatments. Litter decomposition rates under these treatments were evaluated using the Olson model. In the decomposition study, the N treatments in the Evergreen broad-leaved forest increased the remaining mass by 4.75%–17.50% and 2.09%–16.36% compared with the control (20.97 ± 0.44% and 42.43 ± 0.47%), while in the Quercus aquifolioides forest, the remaining mass of leaves and twigs decreased by 5.00% and 0.70% in the LN treatment compared with the control (35.47 ± 0.39% and 44.10 ± 1.18%) and the MN and HN treatments increased by 2.55%–8.13% and 5.61%–11.28%, respectively. Effects of increased N deposition on litter decomposition changed from promoting to inhibiting, as low N sped up decomposition but higher levels inhibited it. Additionally, N boosted the water-holding capacity of litter, especially in leaves. The litter from both forests displayed a notable ability to absorb water. Nitrogen deposition modulates litter decomposition and water retention properties. Specifically, high nitrogen deposition increases litter water-holding capacity by inhibiting the rate of litter decomposition, which in turn alters its mass remaining rate, lignin, and cellulose remaining rates. Efficient management of the studied forests leveraging nitrogen deposition can boost their water conservation potential, aiding in atmospheric precipitation absorption and surface runoff regulation. Full article

Atmospheric nitrogen (N) deposition has rapidly increased due to anthropogenic activities, which can exert a crucial effect on biochemical cycling process such as litter decomposition in the subtropical forests. However, the is still uncertainty about the knowledge of N deposition in regulating nutrient release from the leaf and twig litter. For this study, a 2 yr litterbag decomposition experiment was conducted under three levels of N addition treatments in a subtropical evergreen broad-leaved forest, in southwest China. This study aimed to identify the effects of low (LN: 10 g·N·m⁻²·y⁻¹), medium (MN: 20 g·N·m⁻²·y⁻¹), and high N addition (HN: 25 g·N·m⁻²·y⁻¹) on litter decomposition and nutrient release from leaves and twigs. We observed that there was significantly lower litter decomposition (8.13%–13.86%) and nutrient release (7.24%–36.08%) in the HN treatment compared to the LN treatment. The decay of mass, lignin, and cellulose and the nutrient release were faster in leaf litter than in twig litter after N addition (p < 0.05). The ratios of C/phosphorus (P), C/N, and N/P were also significantly greater in twig litter than in leaf litter. Furthermore, the N addition treatments resulted in higher contents of the mass, lignin, and cellulgapose remaining in leaf and twig litter compared to the control (CK). The amount of C, N, and P remaining in leaf (51.4%–59.1%) and twig (44.1%–64.8%) debris was significantly higher in the N treatment compared to CK treatment (p < 0.05). In addition, the litter C/N and C/P were smaller and the litter N/P was larger for each N treatment compared to CK (p < 0.05). The results suggest that N inputs restrain lignin and cellulose degradation and C and N release, and increase the N/P ratio that limits P release in litter. These effects vary with the level of N treatments. Full article

Litter humification plays a crucial role in organic matter formation and soil carbon sequestration in forest ecosystems. However, how forest gap formation and gap size variation affect the litter humification process remains poorly understood. An eight-year in situ decomposition experiment was conducted to evaluate humus accumulation (humic substances, humic and fulvic acid), humification degrees, humification ratios and optical properties (ΔlogK, E4/E6 and A600/C) of Minjiang fir (Abies faxoniana Rehder & E.H.Wilson) twig litter in four gap size treatments in an alpine primitive forest on the eastern Tibetan Plateau, including (1) closed canopies, (2) small gaps (38–46 m² in size), (3) medium gaps (153–176 m² in size),and (4) large gaps (255–290 m² in size). The results indicated that the accumulation of humic substances and humic acid in the closed canopies was significantly higher than that in the large gaps during the first two years of decomposition. After eight years of decomposition, there were significant differences in the humic substance accumulations and the values of ΔlogK and A₆₀₀/C among the different gap sizes. Furthermore, twig litter was humified in the first 2 years of incubation, and the net accumulation of humic substances was ranged from −23.46% to −44.04% of the initial level at the end of the experiment. The newly accumulated humus was young (mature (type Rp) humus) and transformed to mature (type A) humus after 4–6 years of decomposition. Partial least squares (PLS) suggested that gap-induced variations in twig litter chemistry (i.e., contents of cellulose, lignin, nitrogen (N) and phosphorus (P), and the ratios of C/N N/P) mainly drove the process of twig litter humification. Our results presented here denote that the formation of forest gaps retard twig litter humification process, which might be detrimental to carbon sequestration in the alpine forest ecosystems. Full article

Non-structural carbohydrates (NSCs) are labile components in forest litter that can be released quickly at the early stage of litter decomposition and accelerate the metabolic turnover of soil microorganisms, which is essential for the formation of forest soil organic matter. Therefore, understanding the NSCs response mechanisms to forest litter at different altitudes is critical for understanding nutrient cycling in the forest soil under climate change conditions. In this study, we used the net bag decomposition method to observe the dynamics of NSCs release in Chinese fir topsoil and canopy litter at four altitudes for 360 days based on the climatic zone characteristics distributed vertically along the elevation of Wuyi Mountain. The release of NSCs in Chinese fir litter rise gradually with height increases during the decomposition. The difference of the cumulative release percentage of soluble sugar between different altitudes is more significant than that of starch. The response of the NSC content in different treatment groups at four altitudes are different. The release of NSCs in the leaf canopy litter is higher than that in the leaf topsoil litter. On the contrary, the release of NSCs in the mixture of leaf and twig topsoil litter is higher than that in the mixture of leaf and twig canopy litter. Taken together, this study is of great significance for a comprehensive understanding of the effect of climate change on NSCs during the decomposition of Chinese fir litter. Full article

Optimizing stand structure can enhance plantation forest ecosystem service functions by regulating litterfall patterns; however, the effects of close-to-nature management on litterfall production remain unclear. Here, we selected three cypress (Cupressus funebris) plantations, including one using the practice of strip filling (SF), one using the practice of ecological thinning (ET), and one pure cypress plantation without any artificial interference. The production of total litterfall and its components (leaf, twig, reproductive organ and miscellaneous litterfall) were investigated monthly over one year from September 2019 to August 2020. Compared with that of the pure plantation, the total annual litterfall production of the SF and ET plantations decreased significantly by 10.8% and 36.44%, respectively. The annual production of leaf and reproductive organ litter was similar to that of total litterfall, but that of twig and miscellaneous litter was higher in the SF and ET plantations than in the pure plantation. Moreover, total, leaf and reproductive organ litterfall production displayed unimodal dynamics regardless of plantation, although the peaks of reproductive organ litter production occurred in different months. In contrast, the production of twig litter showed bimodal dynamics in the pure plantation, while unimodal and irregular dynamics were observed in the plantations with ET and SF, respectively. Additionally, insignificant differences in the isometric growth index of leaf litter and total litterfall were observed. The allometric indices of twig litterfall versus total litterfall, reproductive organ litterfall versus total litterfall, and leaf litterfall versus twig litterfall were higher in the plantations with SF and ET than in the pure plantation. Redundancy analysis (RDA) revealed that diameter at breast height and air temperature were the most important factors shaping the annual and monthly production of litterfall, respectively. These results provide efficient data to support the rectification of the material circulation of cypress plantations and their future management. Full article

While surveying the mycobiomes of dead woody litter in Yunnan Province, China, numerous isolates with affinity to Pleosporales (Dothideomycetes, Ascomycota) were recovered. The present work characterizes two species associated with dead woody twigs found in terrestrial habitats in the Kunming area of Yunnan. The novel taxa were recognized based on a polyphasic approach, including morphological examination and multiple gene phylogenetic analyses (non-translated loci and protein-coding regions). Neokalmusia jonahhulmei sp. nov. is introduced in Didymosphaeriaceae (Pleosporales) as a woody-based saprobic ascomycete that possesses multiloculate ascostromata immersed under a black clypeus-like structure, and three-septate, brown, fusiform, guttulate ascospores. Thyridaria jonahhulmei (Thyridariaceae) is introduced with teleomorphic and anamorphic (coelomycetous) characteristics. The teleomorph has the following characteristics: globose to subglobose ascomata with an ostiolum, a pruinose layer of yellow to reddish- or orange-brown material appearing around the top of the ostiolar necks, and brown, ellipsoid to fusoid, two-to-three-septate, euseptate, rough-walled ascospores; the anamorph features pycnidial conidiomata, phialidic, ampulliform to doliiform, conidiogenous cells, and brown, guttulate, ellipsoidal, aseptate conidia. Full article

The oxidative ratio (OR) of organic material integrates the ratio of CO₂ sequestered in biomass vs. O₂ produced over longer timescales, but the temporal and spatial variability within a single ecosystem has received very limited attention. Between October 2017 and October 2019, we repeatedly sampled leaves, twigs, bark, outer stem wood, understorey vegetation and litter in a temperate beech forest close to Leinefelde (Germany) for OR measurements across a seasonal and spatial gradient. Plant component OR ranged from 1.004 ± 0.010 for fine roots to 1.089 ± 0.002 for leaves. Inter- and intra-annual differences for leaf and twig OR exist, but we found no correlation with sampling height within the canopy. Leaf OR had the highest temporal variability (minimum 1.069 ± 0.007, maximum 1.098 ± 0.002). This was expected, since leaf biomass of deciduous trees only represents the signal of the current growing season, while twig, stem and litter layer OR integrate multiple years. The sampling years 2018 and 2019 were unusually hot and dry, with low water availability in the summer, which could especially affect the August leaf OR. Total above-ground OR is dominated by the extremely stable stem OR and shows little variation (1.070 ± 0.02) throughout the two sampling years, even when facing extreme events. Full article

In cranberry production systems, stands are covered by 1–5 cm of sand every 2–5 years to stimulate plant growth, resulting in alternate layers of sand and litter in soil upper layers. However, almost intact twigs and leaves remain in subsurface layers, indicating a slow decomposition rate. The Tea Bag Index (TBI) provides an internationally standardized methodology to compare litter decomposition rates (k) and stabilization (S) among terrestrial ecosystems. However, TBI parameters may be altered by time-dependent changes in the contact between litter and their immediate environment. The aims of this study were to determine the TBI of cranberry agroecosystems and compare it to the TBI of other terrestrial ecosystems. Litters were standardized green tea, standardized rooibos tea, and cranberry residues collected on the plantation floor. Litter decomposition was monitored during two consecutive years. Added N did not affect TBI parameters (k and S) due to possible N leaching and strong acidic soil condition. Decomposition rates (k) averaged (mean ± SD) 9.7 × 10⁻³ day⁻¹ ± 1.6 × 10⁻³ for green tea, 3.3 × 10⁻³ day⁻¹ ± 0.8 × 10⁻⁵ for rooibos tea, and 0.4 × 10⁻³ day⁻¹ ± 0.86 × 10⁻³ for cranberry residues due to large differences in biochemical composition and tissue structure. The TBI decomposition rate (k) was 0.006 day⁻¹ ± 0.002 in the low range among terrestrial ecosystems, and the stabilization factor (S) was 0.28 ± 0.08, indicating high potential for carbon accumulation in cranberry agroecosystems. Decomposition rates of tea litters were reduced by fractal coefficients of 0.6 for green tea and 0.4 for rooibos tea, indicating protection mechanisms building up with time in the tea bags. While the computation of the TBI stabilization factor may be biased because the green tea was not fully decomposed, fractal kinetics could be used as additional index to compare agroecosystems. Full article

Extensive areas of inland dunes are commonly overplanted with Scots pine (Pinus sylvestris). However, thus far the pine litterfall has not been investigated in detail in Scots pine stands overgrowing the landforms. Therefore, the aim of this study was to analyse the mass and chemical composition of litterfall in a dune Scots pine forest, paying special attention to the differences in the properties of the particular categories of litterfall (needles, twigs, bark, cones, residue) occurring in different seasons. The secondary goal of the research was to investigate the possible effect of contrasting slope aspect on litterfall properties. Litterfall was examined for three years on a north- and south-facing dune slope using the litter trap method. The mass and chemical composition (C, N, P, K, Mg, Mn, Ca, Fe, Al) of each litterfall category was analysed. Average annual mass of litterfall ranged from 322.0 ± 2.6 (slope N) to 361.9 ± 34.2 (slope S) g m⁻² year⁻¹. Fluctuations in the annual concentrations of N, P, K and Mg were determined, which was the result of their gradual withdrawal from needles before they were dropped in autumn. Immobile or poorly mobile elements (i.e., Mn, Ca, Fe and Al) were found to be steadily accumulated during the year in fallen tissues. The studied elements can be set in the following order as regards the annual pools which return to a topsoil with litterfall: C > N > Ca > K > Mg > Mn > Al > P > Fe on slope N and C > Ca > N > K > Mg > Al > P > Mn > Fe on slope S. Despite the fact that the residue (seeds etc.) constitutes a much smaller part of the total litterfall mass than the needles, comparable amounts of N, P, K, Al and Fe return to a topsoil with both these categories. The only element for which we determined differences in concentrations regarding slope aspect was Mn: the concentrations were significantly higher for needles, twigs, bark and cones on the N than the S slope. Full article

Phosphorus (P) is a key limiting nutrient in subtropical forests and mixed forests with broadleaved species have been expected to stimulate P cycling, compared to pure conifer plantations. However, the mixture effect of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and broadleaved species on rhizosphere soil and coniferous tree P dynamics is unclear. In our study, eight plots of a single species of a Chinese fir plantation (pure plantation, PP) and eight mixed plantations (mixed plantation, MP) with broadleaved tree species (Michelia macclurei Dandy in Hunan Province or Schima superba Gardn. et Champ. in Fujian Province) were selected in subtropical China. Six P fractions in the rhizosphere and bulk soils were analyzed by a modified Hedley P fractionation method. Phosphorus fractions and nitrogen (N) concentrations in different root orders, different age fresh needles and twigs, and needle and twig litter of Chinese fir were measured. Our results showed that available P, slowly released P, occluded P, and the total extractable P in rhizosphere soil were significantly higher in MP than PP (p < 0.05). In contrast, P and N concentrations in the transportive roots and two-year old needles were generally higher in PP than MP. Meanwhile, the slowly released P, occluded P, total extractable P, and residual P in rhizosphere soil were negatively correlated with P concentrations in young (absorptive and transportive roots, one- and two-year old needles) but not old tissues (storative roots, three-year old needles and litters). In conclusion, mixture may increase soil P availability through the rhizosphere effect, but can decrease P and N concentration of Chinese fir tissues by competition between Chinese fir and broadleaved species. Clearly, the mixture effect may differ in soil and plant nutrients, and this issue needs be taken into consideration when converting a pure conifer plantation into a mixed-species forest. Full article