In order to achieve rapid and qualitative detection of soluble heavy metal ions, nitrogen-doped fluorescent carbon quantum dots (N-CQDs) were synthesized using chitin extracted from shrimp and crab shells as the carbon source. The structural, morphological, and optical properties of the synthesized N-CQDs were systematically characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), Raman, X-ray photoelectron spectroscopies (XPS), ultraviolet-visible (UV-Vis) absorption spectroscopy and fluorescence spectroscopy. The resulting N-CQDs exhibited a carbonization yield of 54.46% and a fluorescence quantum yield of 34.33%. Their morphology, structure and optical properties were thoroughly characterized using a range of analytical techniques. The synthesized N-CQDs exhibited excellent fluorescence properties, and remarkable stability. When applied for metal ion detection, the N-CQDs displayed a distinct and selective fluorescence quenching response exclusively toward Fe³⁺ ions. The detection limit for Fe³⁺ at room temperature was 4.04 μmol/L. Furthermore, due to the inherent nitrogen present in the acetyl amino groups of chitin, nitrogen doping was achieved without the need for external dopants during the hydrothermal synthesis process. Owing to their high stability, low cost and low toxicity, the N-CQDs synthesized in this study provide a promising fluorescence sensing platform with excellent selectivity for Fe³⁺ detection, achieved through precise control of surface functional groups.

Soil fungi play vital roles in the forest soil ecosystems through the nutrient cycle and organic substance decomposition, so the distribution of fungi at different altitudes has attracted increasing attention. However, their abundance, diversity, and community structure at different altitudes in temperate deciduous forests have rarely been studied. In this study, the fungal communities around two dominant trees (Quercus aliena var. acutiserrata and Carpinus turczaninowii Hance) in temperate deciduous forests at different altitudes (low altitude, medium altitude, high altitude) in the Taihang Mountains were identified via Illumina high-throughput sequencing according to the UNITE database. The soil chemical properties (soil pH value, soil available potassium, alkaline hydrolyzed nitrogen, soil available phosphorus contents, soil total nitrogen, and carbon contents) were also measured. The results revealed that the dominant genera around the tree species were Russula, Tylopilus, Sebacina, Saitozyma, Mortierella, Amanita, and Descolea. The highest relative abundance of fungi occurred at the lowest altitude. The species richness index and diversity index of fungi around Carpinus turczaninowii at low altitudes were the highest. The soil pH, available potassium content, and alkaline hydrolyzed nitrogen content played a crucial role in the composition and diversity of the fungal communities at different altitudes. Therefore, soil physicochemical properties were the important factors in forming fungi composition and diversity at different altitudes in the temperate forest.

Root pruning affects the ability of roots of Quercus variabilis Blume to absorb water and nutrients. Suillus grevillea can form a mutualistic symbiosis with Quercus variabilis Blume. A pot experiment in three compartments with two inoculation treatments (inoculation with Suillus grevillea and noninoculation control) and four different root pruning treatments (0, 1/4, 1/3, and 1/2 of the main root length pruned) was conducted. The shoot dry weight, root dry weight, shoot and root N, P and K contents, root morphological and physiological parameters of Quercus variabilis Blume seedlings, and soil properties were measured. The results showed that root pruning affected root endogenous hormone levels, root morphology, shoot and root nutrient absorption, and biomass accumulation. Compared with those without inoculation, the shoot dry weight, root dry weights, shoot and root N, and P and K contents of inoculated plants were greater, regardless of the degree of root pruning. The root length, root projection area, root surface area, root average diameter, root density, root volume, and root tip number increased in response to Suillus grevillea. The root auxin (IAA), cytokinin (CTK), gibberellin (GA), zeatin riboside (ZR), and salicylic acid (SA) contents were greater in inoculated Quercus variabilis Blume seedlings than in noninoculated plants. Inoculation with Suillus grevillea improved the soil microenvironment around the seedlings. Suillus grevillea can compensate for the adverse effects of root pruning on nutrient absorption, root morphological and physiological growth and the soil properties of Quercus variabilis Blume seedlings.