Diversity

The coleopteran Eutrichillus comus (Bates) (Cerambycidae: Lamiinae) was recently detected boring into the branches and trunks of Mexican lemon (Citrus aurantiifolia Swingle), Persian lemon (Citrus latifolia Tanaka), and grapefruit (Citrus paradisi Macfad) in the Apatzingán Valley, Michoacán, Mexico. This study characterized the larval development of two E. comus populations by determining the number of instars and estimating their corresponding growth ratios, using larvae collected from Persian lemon and Mexican lemon trees. Morphometric analyses were based on two variables measured: head capsule width and pronotum width. Frequency distributions of each variable analyzed separately did not allow clear delimitation of larval instars in either population. However, frequency distributions based on a proportion factor derived from the product of the two measured variables and the following discriminant analysis clearly indicated that both E. comus populations undergo three distinct instars. The mean growth ratios were 1.50 and 1.36 for the Persian lemon and Mexican lemon populations, respectively. These estimated ratios were not consistent with the growth constant predicted by Dyar’s rule. These findings provide baseline biological information that may contribute to developing preventive management approaches to minimize the risk of this species becoming an economically significant pest.

Crop straw return is widely used to maintain soil fertility in intensive rice systems. How soil microbial communities respond to nitrogen rate under full straw return, and whether these responses differ between soil layers, remains poorly resolved. In this study, a field experiment with five nitrogen application rates (0 [RF0], 53 [RF1], 93 [RF2], 133 [RF3], and 173 [RF4] kg N ha⁻¹) under uniform full rice straw return (7500 kg straw ha⁻¹) was conducted in a cold-region paddy ecosystem. Soil physicochemical properties, bacterial community structure and functional potential (metagenomics) were systematically analyzed in surface (0–10 cm) and subsurface (10–20 cm) layers. Results showed that moderate nitrogen application (133 kg N ha⁻¹) optimally enhanced total nitrogen, total organic carbon, labile carbon fractions, and available phosphorus and potassium in both soil layers. However, excessive nitrogen application (173 kg N ha⁻¹) provided no further benefits and significantly decreased available phosphorus and potassium relative to their peak values observed under optimal nitrogen inputs. A combined PCoA of both soil layers showed no separation by depth or by nitrogen rate. PERMANOVA detected a weak but significant overall model (R² = 0.241, p = 0.0002) without a significant depth × nitrogen interaction (R²= 0.065, p = 0.328). Bacterial taxonomic composition exhibited strong resistance to nitrogen disturbance, with a large core microbiome (dominated by Proteobacteria, Chloroflexi, and Acidobacteria) remaining stable across treatments and depths. In contrast, functional genes and metabolic pathways involved in carbon, nitrogen, and sulfur cycling displayed high plasticity. Moderate nitrogen activated complex carbohydrate degradation and dark carbon fixation in deeper soil, while high nitrogen shifted surface communities from autotrophic carbon fixation (Calvin-Benson-Bassham cycle) toward heterotrophic fermentation and strongly stimulated denitrification pathways, increasing potential gaseous nitrogen loss. Overall, this study reveals a clear taxonomic-functional decoupling and demonstrates that 133 kg N ha⁻¹ represents the optimal threshold for balancing soil nutrient accumulation, microbial functional activity, and environmental risk under full rice straw return. These findings provide a theoretical basis for precision nitrogen management in straw-return systems.

Vallisneria spinulosa Yan (V. spinulosa Yan), as a submerged macrophyte and herbal plant, simultaneously exhibits ecological restoration functions in water bodies and medicinal value. However, it cannot be efficiently planted and cultivated in turbid water bodies. Enclosure cultivation technology can solve this issue in real ecological engineering, and enclosure area is an important parameter. The impact of enclosure area on growth characteristics, water purification, and microbial communities of the V. spinulosa Yan growth system in the enclosure cultivation process was studied, with planting density (50 plants·m⁻²) and soil volume per pot kept constant. The results showed that enclosure area primarily shifted biomass allocation: aboveground biomass decreased, and belowground biomass increased with increasing enclosure area, with the root-to-shoot ratio rising from 0.449 (A1, 1 × 1 m enclosure area) to 1.013 (A16, 4 × 4 m enclosure area). Total biomass, leaf number, soluble protein, and soluble sugar did not differ significantly among treatments. Leaf length was significantly greatest in A1. Notably, chlorophyll a, chlorophyll b, and total chlorophyll were significantly lowest in the A4 (2 × 2 m enclosure area) treatment, while SOD (superoxide dismutase) activity was highest in A1 and POD (peroxidase) activity was lowest in A1, all surviving global multiple-comparison correction. Nutrient removal loads (TN, nitrate nitrogen, TP, and PO₄³⁻-P) were significantly higher in planted treatments than in the unplanted control, but pairwise comparisons among planted treatments showed no significant differences. Furthermore, A1 exhibited significantly higher TP (total phosphorus) and PO₄³⁻-P (phosphate) removal loads than the other planted treatments, and its TN (total nitrogen) removal load was significantly higher than that of A9 (3 × 3 m enclosure area). Overall, enclosure area primarily shifted biomass allocation and induced complex physiological responses, without uniformly improving growth or water purification performance. This study can provide valuable references for efficient cultivation of submerged macrophytes and enhancing water purification effects in real ecological engineering.