Nitrogen loss is the main reason for land quality degradation and productivity decline and an important factor in groundwater pollution. Extreme rainfall has occurred frequently in Karst areas of southwest China in recent years. It is of great significance to study the response of soil nitrogen loss to extreme rainfall in Karst areas to prevent and treat land quality degradation and non-point source pollution. In this study, field monitoring and indoor artificial rainfall simulation were used to study the loss characteristics of total soil nitrogen (TN), ammonium (NH₄⁺-N) nitrogen, and nitrate-nitrogen (NO₃⁻-N) in Karst bare slope farmland (slope angles of 5° and 10°) under extreme rainfall conditions. The results showed that: (1) Extreme rainfall (90 mm/h) increased the surface runoff, middle soil runoff, and underground runoff by 1.68 times, 1.16 times, and 1.43 times, respectively, compared with moderate rainfall (60 mm/h), so that nitrogen loss increased with runoff. (2) The loss of nitrate-nitrogen in surface, soil, and underground under extreme rainfall conditions was 223.99, 147.93, and 174.02% higher than that under moderate rainfall conditions, respectively; the nitrate losses were 203.78, 160.18, and 195.39% higher, respectively. Total nitrogen losses were 187.33, 115.45, and 138.68% higher, respectively. (3) The influencing factors of total soil nitrogen and nitrate-nitrogen loss in Karst slope farmland were slope > rainfall duration > rainfall intensity, while the influencing factors of ammonium nitrogen loss were rainfall duration > slope > rainfall intensity. Therefore, in controlling nitrogen loss in Karst slope farmland, changing slope degree and increasing farmland coverage may be useful measures to slow the nitrogen loss caused by extreme rainfall.

Background: Lonicera macranthoides (L. macranthoides) is a traditional Chinese medicinal plant, the flower buds of which are rich in bioactive compounds, such as chlorogenic acids (CGAs) and flavonoids, and exhibit diverse pharmacological activities. Methods: Integrated transcriptomic and metabolomic analyses were conducted across three floral developmental stages: flower bud (FB), white flower (WF), and golden flower (GF). Results: Clustering analysis revealed distinct molecular profiles, with the WF and GF stages clustering together and clearly separating from the FB stage. The most significant metabolomic variation was observed between the GF and FB stages. KEGG enrichment analysis consistently highlighted the phenylpropanoid biosynthesis pathway as a key hub. Stage-specific accumulation patterns were identified for critical metabolites: caffeoylquinic acid peaked at the WF stage, while ferulic acid, sinapic acid, cinnamic acid, and p-coumaric acid reached their highest levels at the GF stage. Within this pathway, we identified 11 DEGs encoding the core enzymes, alongside 15 associated DAMs. The expression trends of four PAL genes were fully consistent with the accumulation of related precursors, and F5H expression correlated with its downstream product, sinapic acid. WGCNA identified a key module highly correlated with key phenolic acids, containing 71 transcription factors, including MYB, bHLH, WRKY, and AP2/ERF families, potentially forming a complex regulatory network for phenylpropanoid biosynthesis. Conclusions: This study deciphers the stage-specific regulatory network of CGA biosynthesis, providing critical insights and genetic resources for cultivating high-medicinal-content varieties of L. macranthoides.

Microbial fertilizers may improve phosphorus availability and pH in acidic soils, but field evidence linking these changes with medicinal plant biomass and specialised metabolite accumulation remains limited. Here, a one-season field experiment was conducted in acidic yellow soil in Guizhou Province, China, using four fertilization regimes for Lonicera macranthoides: an organic fertilizer plus compound fertilizer control (CK), a bacterial consortium (T1), a simplified bacterial combination (T2), and a fungal agent (T3). Soil chemical properties, soil aggregate composition, flower-bud biomass, and chlorogenic-acid-related compounds were measured. T1 and T3 increased soil available phosphorus and pH at the pre-flowering stage and increased the proportion of water-stable macroaggregates (>5 mm). Both treatments also increased fresh and dry biomass. T1 showed the highest numerical chlorogenic acid content, whereas T3 was more favourable for the accumulation of isochlorogenic acids A and C. Across plot-level observations, available phosphorus was positively correlated with fresh weight (r = 0.804) and dry weight (r = 0.781), and pH was positively correlated with chlorogenic acid (r = 0.687). Univariate regression and redundancy analysis further indicated that available phosphorus and pH were the soil factors most closely associated with biomass and chlorogenic acid accumulation. These findings provide preliminary field indications that microbial fertilizers may improve yield and medicinal quality in acidic-soil L. macranthoides production. However, the single-season, single-site nature of the experiment warrants cautious interpretation and further validation across broader conditions. The observed associations are consistent with, but do not prove, a mechanistic pathway involving microbe-mediated phosphorus transformation and acidity regulation.