Near-natural transformation of Pinus tabuliformis better improve soil nutrients and soil microbial community

Pinus tabulaeformis plantations have been established around northern China to restore degraded land and provide timber or fuelwood. In recent years, widely distributed monoculture P. tabulaeformis forests have been transformed into mixed forests due to various ecological problems. However, the current research on the influence of near-natural transformation of P. tabulaeformis on soil microbial diversity and community composition remains limited. Therefore, we examined the effect of forest conversion from monoculture Pinus tabuliformis (PT) to P. tabuliformis-Armeniaca vulgaris (PTAU), P. tabuliformis - Robinia pseudoacacia (PTRP), P. tabuliformis - Vitex negundo L. var. heterophylla (PTVN) forests on soil microbial community diversity and composition. The results indicated that compared to PT, PTAU, PTVN, and PTRP could enhance the soil pH, TC, TN, AN, and AK in different degrees, the most obvious in PTAU. Near-natural transformation of P. tabuliformis could improve soil bacterial Pielou_e index, and Simpson index, as well as soil fungal Chao1 index. Proteobacteria and Ascomycota were the dominant soil microbial community at the phylum level. What’s more, both soil bacterial and fungal community among PT, PTAU, PTRP and PTVN showed clear different, and PTAU obviously altered the soil microbial community structure. Proteobacteria was the predominant group in PT, while, Gemmatimonadetes enriched in PTVN. Ascomycota was the predominant group in PTAU, while, Basidiomycota was the predominant group in PTRP. Near-natural transformation of P. tabuliformis could change soil microbial community via altering soil characteristics. In brief, our research results revealed the influence of tree composition and soil nutrient availability on soil microbial diversity and composition, and provided management guidance for introduction soil microbial community in forest protection and management.

The Transcriptional Landscape and Hub Genes Associated with Physiological Responses to Drought Stress in Pinus tabuliformis

Drought stress has an extensive impact on regulating various physiological, metabolic, and molecular responses. In the present study, the Pinus tabuliformis transcriptome was studied to evaluate the drought-responsive genes using RNA- Sequencing approache. The results depicted that photosynthetic rate and H2O conductance started to decline under drought but recovered 24 h after re-watering; however, the intercellular CO2 concentration (Ci) increased with the onset of drought. We identified 84 drought-responsive transcription factors, 62 protein kinases, 17 transcriptional regulators, and 10 network hub genes. Additionally, we observed the expression patterns of several important gene families, including 2192 genes positively expressed in all 48 samples, and 40 genes were commonly co-expressed in all drought and recovery stages compared with the control samples. The drought-responsive transcriptome was conserved mainly between P. tabuliformis and A. thaliana, as 70% (6163) genes had a homologous in arabidopsis, out of which 52% homologous (3178 genes corresponding to 2086 genes in Arabidopsis) were also drought response genes in arabidopsis. The collaborative network exhibited 10 core hub genes integrating with ABA-dependent and independent pathways closely conserved with the ABA signaling pathway in the transcription factors module. PtNCED3 from the ABA family genes had shown significantly different expression patterns under control, mild, prolonged drought, and recovery stages. We found the expression pattern was considerably increased with the prolonged drought condition. PtNCED3 highly expressed in all drought-tested samples; more interestingly, expression pattern was higher under mild and prolonged drought. PtNCED3 is reported as one of the important regulating enzymes in ABA synthesis. The continuous accumulation of ABA in leaves increased resistance against drought was due to accumulation of PtNCED3 under drought stress in the pine needles.