Kai Tian

Individuals can adjust allocation strategies based on intrinsic and extrinsic factors. Variation in nutritional status during sexual maturation and resource acquisition during breeding may affect life history functions and trade‐offs. However, it is unclear whether individuals can compensate for poor nutritional status during sexual maturation when resource acquisition becomes favorable during breeding. To investigate this, we simultaneously manipulated male nutritional status during sexual maturation and resource acquisition during breeding in a burying beetle (Nicrophorus vespilloides). We monitored the separate and interactive effects of these two factors on life history functions and trade‐offs (somatic vs. reproductive investment, number vs. size of offspring). We found that poor nutritional status during sexual maturation negatively affects reproductive investment in adulthood, whereas access to abundant resources during breeding buffers against these effects. Poor‐fed males mitigated the initial differences in nutritional status compared to well‐fed males by feeding more from the carcass, and thus masking the long‐term effects of nutritional status on the reproductive performance. They gained more weight but provided less care than well‐fed males when breeding on a small carcass, whereas they gained more weight and provided a similar amount of care as well‐fed males when breeding on a large carcass. In addition, nutritional status during sexual maturation had no significant effects on subsequent reproductive performance (larvae number and average larval mass). However, there were significant trade‐offs between the number and size of offspring, suggesting that poor‐fed males consumed more from the carcass, which in turn reduced the amount of food resources for their offspring. The results obtained for males are independent of female partner's efforts and compensation effects. Our findings demonstrated that although the nutritional environment experienced during sexual maturation may influence allocation strategies in adulthood, individuals can compensate for a poor start if resource acquisition becomes more favorable during subsequent breeding.

Photodegradation—photochemical mineralization of standing litters—often exerts a legacy effect aiding biodegradation in soil (PLE), which is overlooked in deciduous forests containing marcescent leaves. Meanwhile, increasing anthropogenic microplastics have deposited in forests, how they would affect the PLE on subsequent litter bio‐decomposition is currently unknown. Here, we employed an ultraviolet‐accelerated aging chamber to replicate the abiotic photodegradation process of a naturally marcescent tree, Lindera glauca , then manipulated mesocosm bio‐incubations to quantify how decomposers (microbial alone or with soil animals) and microplastic contamination would interactively affect the PLE. We found abiotic photodegradation significantly decreased litter lignin content before and after the bio‐incubation. During an early phase decomposition, lignin lost greatly and displayed a crucial role in determining the ways that soil animal and photodegradation affect the bio‐decomposition. Microbial decomposer alone led to a positive PLE universally. Soil animals depressed microbial biomass and inhibited the microbial‐mediated PLE in unpolluted mesocosms but intensified the PLE in contaminated soils. We conclude that decomposer interactions can attenuate PLE, but microplastics will disrupt the established equilibrium, making contaminated soil more susceptible to photodegradation‐induced litter chemical changes. This promotes integration of radiation and emerging pollution to further our understanding of biogeochemical cycle in forest ecology.

Resource availability should have consequences for life‐history functions and trade‐offs among them because it influences the amounts of resources allocated to different functions. Nutritional status during a key developmental window (sexual maturation) may also have an important impact on life‐history functions and such trade‐offs. However, less is known about whether and how they interact to influence the resource allocation of individuals. Here, we simultaneously manipulated female nutritional status during sexual maturation and resource availability during breeding in a burying beetle Nicrophorus vespilloides. We then monitored the main and interactive effects of these two factors on somatic maintenance and reproductive performance of burying beetle females. We found that variation in nutritional status during sexual maturation affects the resource allocation of burying beetle females only at the pre‐hatching stage. Poor‐fed females compensated for the initial differences in energy reserves by feeding from the carcass or engaged in terminal investment strategy and invested heavily at the post‐hatching stage. Specifically, poor‐fed females allocated more into somatic maintenance (gained more weight) and less into reproduction (provided less pre‐hatching care) than well‐fed females, whereas they provided a similar amount and duration of post‐hatching care. In addition, burying beetles with different nutritional statuses vary in their response to resource availability. Poor‐fed females allocated more into both somatic maintenance (gained more weight) and reproduction (provided more pre‐hatching care) when bred on large versus small carcasses, whereas well‐fed females tend to work near their maximum capacity and thus show no response to resource availability. Finally, our findings suggest that poor‐fed females did not suffer a future cost in offspring performance. Meanwhile, a large carcass allowed females to produce more and heavier offspring. These findings enhance our understanding of how important nutritional status during a key developmental window and resource availability during breeding is for the expression of resource allocation.

Litter’s chemical complexity influences carbon (C) cycling during its decomposition. However, the chemical and microbial mechanisms underlying the divergence or convergence of chemical complexity under UV radiation remain poorly understood. Here, we conducted a 397-day field experiment using ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance (¹³C-CPMAS NMR) to investigate the interactions among the initial chemistry, microbial communities, and UV radiation during decomposition. Our study found that the initial concentrations of O-substituted aromatic C, di-O-alkyl C, and O-alkyl C in Deschampsia caespitosa were higher than those in Kobresia tibetica. Litter’s chemical composition exhibited divergent patterns based on the initial chemistry, UV radiation, and decay time. Specifically, D. caespitosa consistently displayed higher concentrations of di-O-alkyl C and O-alkyl C compared to K. tibetica, regardless of the UV exposure and decay time. Additionally, litter’s chemical complexity was positively correlated with changes in the extracellular enzyme activities, particularly those involved in lignin, cellulose, and hemicellulose degradation, which accounted for 9%, 20%, and 4% of the variation in litter’s chemical complexity, respectively. These findings highlighted the role of distinct microbial communities in decomposing different C components through catabolism, leading to chemical divergence in litter. During the early decomposition stages, oligotrophic Planctomycetes and Acidobacteria metabolized O-alkyl C and di-O-alkyl C under UV-blocking conditions. In contrast, copiotrophic Actinobacteria and Chytridiomycota utilized these components under UV radiation exposure, reflecting their ability to thrive under UV stress conditions due to their rapid growth strategies in environments rich in labile C. Our study revealed that the inherent differences in the initial O-alkyl C and di-O-alkyl C contributed to the chemical divergence, while UV radiation further influenced this divergence by shifting the microbial community composition from oligotrophic to copiotrophic species. Thus, differences in the initial litter chemistry, microbial community, and UV radiation affected the quantity and quality of plant-derived C during decomposition.

Coreopsis tinctoria is an annual herb and commonly cultivated in gardens due to its attractive flowers, its capitula also have been used as a traditional medicine in China, Asia, North America and Europe (Shen et al. 2021). In June 2023, severe powdery mildew infection was observed on C. tinctoria in a hillside near headwork of the middle route of the South to North Water Diversion Project (32°40'55''N, 111°41'59''E). Abundant irregular white spots were found on adaxial surface of the leaves and tender stems. Approximately 75% of the observed C. tinctoria plants showed these signs and symptoms. Generative hyphae were thin-walled, smooth or almost so, and 5 to 9 μm wide. Conidiophores were unbranched, straight, 80.5 to 162.5 × 9.3 to 12.9 μm (n=25), and produced one to three immature conidia. Foot-cells of conidiophores were cylindrical, 38.5 to 62.3 μm (n=20) long. Conidia were ellipsoid to ovoid, 25.1 to 31.9 × 15.2 to 19.5 μm (n=30). The morphological characteristics of asexual structures corresponded to Podosphaera sp. (Braun and Cook 2012). For further identification, genomic DNA was extracted directly from the mycelia and conidia using Chelex 100 (Sigma Aldrich, Shanghai, China). The internal transcribed spacer (ITS) regions and 28S large subunit (LSU) of ribosomal DNA from the specimen (CT2302) were amplified using the primers ITS1/ITS4 (expected amplicon size 566 bp) (White et al. 1990) and NL1/NL4 (expected amplicon size 618 bp) (Baten et al. 2014), respectively. The sequences of ITS (GenBank accession no. OR649304) and LSU (GenBank accession no. OR649305) showed 99.63% and 100% identity values to the Podosphaera fusca isolate HMNWAFU-CF2012074 in the NCBI database (KR048109 for ITS and KR048178 for LSU), respectively. Phylogenetic analyses based on the combined ITS and LSU sequences using MEGA 7.0 software indicated that CT2302 formed a monophyletic clade together with isolates of P. fusca. Therefore, this fungus was identified as P. fusca based on the morphological and molecular characteristics. Pathogenicity tests were performed by gently pressing the infected leaves onto 15 young leaves of five healthy plants and three noninoculated plants were used as controls. All plants were maintained in a greenhouse (25℃ and 70% relative humidity). Powdery mildew symptoms similar to those of originally diseased plants were observed on all inoculated leaves after 12 days, whereas no symptoms were observed on the control leaves. Powdery mildew caused by P. fusca (previously Sphaerotheca fusca) on C. tinctoria has been reported in Russia, Poland, Korea, Romania and Ukraine (Cho and Shin 2004; Rusanov and Bulgakow 2008). To our knowledge, this is the first report of P. fusca on C. tinctoria in China. The identification of P. fusca as the causal agent on C. tinctoria is critical to the prevention and control of this disease in the future.

Earthworms modulate carbon and nitrogen cycling in terrestrial ecosystems, but their effect may be compromised by the deposition of pollutants from industrial emissions. However, studies investigating how deposited compounds affect the role of earthworms in carbon cycling such as litter decomposition are lacking, although the interactions of earthworms and deposited compounds are important for understanding the impact of pollutants on ecosystems and the potential of earthworms in bioremediation. We performed a 365‐day in situ litterbag decomposition experiment in a deciduous (Quercus variabilis) and coniferous (Pinus massoniana) forest in southeast China. We manipulated nitrogen (N), sodium (Na), and polycyclic aromatic hydrocarbons (PAHs) as model compounds during litter decomposition with and without earthworms (Eisenia fetida). After one year, N, Na, and PAH all slowed down litter mass loss, with the effects of Na being the strongest. By contrast, E. fetida generally increased litter mass loss, and the positive effects were uniformly maintained irrespective of the type of compounds added. However, the pathways to how earthworms increased litter mass loss varied among the compounds added and the two forests studied. As indicated by structural equation modeling, earthworms mitigated the negative effects of deposited compounds by directly increasing litter mass loss and indirectly increasing soil pH and microbial biomass. Overall, the results indicate that the acceleration of litter mass loss by earthworms is little affected by deposited compounds, and that earthworms have the potential to mitigate negative impacts of pollutants on litter decomposition and ecosystem processes.

Solar radiation has been regarded as a driver of litter decomposition in arid and semiarid ecosystems. Photodegradation of litter organic carbon (C) depends on chemical composition and water availability. However, the chemical changes in organic C that respond to solar radiation interacting with water pulses remain unknown. To explain changes in the chemical components of litter organic C exposed to UV-B, UV-A, and photosynthetically active radiation (PAR) mediated by water pulses, we measured the chemistry of marcescent Lindera glauca leaf litter by solid-state ¹³C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) over 494 days of litter decomposition with a microcosm experiment. Abiotic and biotic factors regulated litter decomposition via three pathways: first, photochemical mineralization of lignin methoxyl C rather than aromatic C exposed to UV radiation; second, the biological oxidation and leaching of cellulose O-alkyl C exposed to PAR and UV radiation interacts with water pulses; and third, the photopriming effect of UV radiation on lignin aromatic C rather than cellulose O-alkyl C under the interaction between radiation and water pulses. The robust decomposition index that explained the changes in the mass loss was the ratio of aromatic C to O-alkyl C (AR/OA) under radiation, but the ratio of hydrophobic to hydrophilic C (hydrophobicity), the carbohydrate C to methoxyl C ratio (CC/MC), and the alkyl C to O-alkyl C ratio (A/OA) under radiation were mediated by water pulses. Moreover, the photopriming effect and water availability promoted the potential activities of peroxidase and phenol oxidase associated with lignin degradation secreted by fungi. Our results suggest that direct photodegradation of lignin methoxyl C increases microbial accessibility to lignin aromatic C. Photo-oxidized compounds might be an additional C pool to regulate the stability of the soil C pool derived from plant litter by degrading lignin methoxyl and aromatic C.