Masson pine (Pinus massoniana) is a major fast-growing timber species planted in southern China, a region of seasonal drought. Using a drought-tolerance genotype of Masson pine, we conducted large-scale transcriptome sequencing using Illumina technology. This work aimed to evaluate the transcriptomic responses of Masson pine to different levels of drought stress. First, 3397, 1695 and 1550 unigenes with differential expression were identified by comparing plants subjected to light, moderate or severe drought with control plants. Second, several gene ontology (GO) categories (oxidation-reduction and metabolism) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways (plant hormone signal transduction and metabolic pathways) were enriched, indicating that the expression levels of some genes in these enriched GO terms and pathways were altered under drought stress. Third, several transcription factors (TFs) associated with circadian rhythms (HY5 and LHY), signal transduction (ERF), and defense responses (WRKY) were identified, and these TFs may play key roles in adapting to drought stress. Drought also caused significant changes in the expression of certain functional genes linked to osmotic adjustment (P5CS), abscisic acid (ABA) responses (NCED, PYL, PP2C and SnRK), and reactive oxygen species (ROS) scavenging (GPX, GST and GSR). These transcriptomic results provide insight into the molecular mechanisms of drought stress adaptation in Masson pine.

The purpose of this study was to explore the inherent links between elemental cycling in Rosa roxburghii Tratt litter and soil, as well as their coupled relationships, within barren soil environments typical of karst rocky desertification regions in Guizhou Province. Ecological stoichiometric methods were used to systematically analyze the nutrient concentrations of C, N, P, and K and their stoichiometry in the litter and soil of Rosa roxburghii, with a focus on the impacts of seasonal variations and rocky desertification regions. High C and K levels and low N and P levels are observed in the litter, whereas the soil has lower concentrations of C, N, P, and K, with nutrient replenishment priorities of N > P > K > C. Strong positive correlations are found among the C/N, C/P, and N/K stoichiometric ratios in both the litter and the soil. Furthermore, nutrient concentrations and stoichiometric ratios vary significantly by season. Seasonal variations influence nutrient concentrations, with notable increases in litter P and K levels and in soil N and P levels in September compared with March. Seasonal variations influence the stoichiometric ratios of C/N, C/P, and N/K in litter and soil, contributing to elemental balance and ecosystem stability. Moreover, significant variations in nutrient contents and stoichiometric ratios are observed across distinct rocky desertification grades. Nonrocky desertified areas present elevated P and K contents in litter, whereas light desertified areas present increased C and N concentrations. Moderately desertified areas presented increased soil P and K concentrations, whereas severely desertified areas presented the highest N levels. These discernible trends in nutrient profiles highlight the synergistic impacts of soil nutrient inadequacy and plant utilization strategies. These findings contribute to a better understanding of element cycling mechanisms in Rosa roxburghii woodland ecosystems, offering valuable information for sustainable forest management practices.

Karst rocky desertification (KRD) is a critical abiotic stressor that compromises Rosa roxburghii Tratt fruit quality, yet its underlying physiological and ecological pathways remain poorly understood. This study aims to bridge this knowledge gap by elucidating how KRD-driven soil C:N:P:K stoichiometric shifts indirectly affect fruit quality (vitamin C and fructose) by disrupting fruit internal elemental balance. We characterized soil nutrient dynamics and evaluated fruit quality along the natural rocky desertification gradient (RDG) in Guizhou, China. Mantel tests and structural equation modeling (SEM) were applied to identify primary predictors and quantify integrated pathways. With increasing desertification, total organic carbon (TOC), total nitrogen (TN), and soil C:P ratio (C:P) increased monotonically, while total phosphorus (TP) remained at a low concentration without significant change. Available phosphorus (AP) and available potassium (AK) followed a U-shaped trend, reaching their minimum under moderate desertification, whereas total potassium (TK) peaked at this stage before declining. Correspondingly, fruit vitamin C (FVC) and fruit fructose (FF) exhibited a non-linear pattern, first increasing under light stress, then decreasing under moderate stress, and finally rebounding under severe desertification, which is consistent with the nonlinear response pattern of fruit C:P ratio (FC:FP) reported for the same desertification stages. The SEM revealed a dual-pathway mechanism: KRD directly enhanced FVC (β = 0.69, p < 0.001), while KRD and soil properties enhanced FF (β = 0.39 and 0.64, respectively, p < 0.01). KRD also indirectly lowered FVC and FF through a sequential nutrient cascade that promoted soil nutrients (Soil, β = 0.81–0.82, p < 0.001), which triggered negative effects particularly via soil stoichiometry (SS, |β| = 0.76–0.91, p < 0.001), with a modest additional contribution from fruit stoichiometry (FS, |β| ≈ 0.27, p < 0.05). This suggests that KRD influences fruit quality via a soil–plant network mediated by soil P-limitation and K-dynamics. Balanced P and K management may, therefore, be critical for maintaining fruit quality and ecological restoration in karst ecosystems.