Influences of micro-geomorphology on the stoichiometry of C, N and P in Chenier Island soils and plants in the Yellow River Delta, China

The nutritional status and root development of silver fir (Abies alba Mill.) seedlings growing on decaying deadwood in temperate forest ecosystem

The study aimed to compare two substrates, soil and deadwood, for the regeneration of silver fir (Abies alba Mill.) seedlings. Three-year-old fir seedlings growing both on deadwood and in the soil were collected. The examination involved determining the physical, chemical, and biochemical properties of soil and deadwood, as well as assessing the morphology of the roots and the nutrition of seedlings growing on the soil and deadwood. The examined substrates differed in physical, chemical and biochemical properties. It was shown that strongly decomposed fir logs are a good substrate for the growth of fir seedlings, mainly due to the high content of exchangeable cations (especially calcium, magnesium and potassium) and high phosphorus and nitrogen content. The type of substrate had a significant impact on the root morphology of fir seedlings. In our study, the most responsive root traits to differences in growing substrates were specific root area (SRA) and specific root length (SRL). Our analyses did not confirm significant differences in the stoichiometry of C, N and P in the roots and needles of seedlings grown on different substrates. The stoichiometry of roots and needles suggests no limitations in the uptake of nutrients by seedlings growing on deadwood. This study validated that heavily decomposed wood can provide favourable microhabitats for the growth of the young generation of fir.

Elemental stoichiometry (C, N, P) of soil in the Yellow River Delta nature reserve: Understanding N and P status of soil in the coastal estuary

The Yellow River Delta Nature Reserve (YNR), which includes two separated regions: part of the old Yellow River Delta (OYD) and part of the current Yellow River Delta (CYD), was established to protect coastal wetlands in the coastal estuary. A total of 120 plots were sampled in the YNR in April 2016, and the spatial patterns of soil C, N and P contents and their stoichiometric ratios (C:N (R_CN), C:P (R_CP) and N:P (R_NP)) were studied and interpolated using the Ordinary Kriging method. Results indicated that the soil elemental contents and stoichiometric ratios showed high spatial heterogeneity and large variations. The mean C:N:P ratio (R_CNP) was ~ 64.7:2.3:1 in OYD, and ~ 64.5:2.0:1 in CYD, respectively, and a well-constrained R_CP ratio ~ 65:1 was found in the 0-50 cm soil depth within the YNR. N showed greater variation than C and P. Furthermore, N contents in the 0-5 cm soil layer of OYD were significantly higher than that of CYD (F = 4.79, p = 0.03); R_CN in 0-5 cm, 5-10 cm layers of OYD was significantly lower than those in the same layers of CYD (F = 4.75, p = 0.03; F = 5.18, p = 0.02, respectively). R_NP in 0-5 cm soil layer of OYD was notably higher than that of CYD (F = 4.88, p = 0.03). These results were due to the combined actions of sedimentation, reclamation and fertilization. Finally, we concluded that a longer reclamation and fertilization history led to decreased R_CN in coastal estuary soils, confirmed that the soil of the YNR exhibits N limitation, and suggested that the soil R_CN and R_NP could be good indicators of the anthropogenic improvement status during soil development in this coastal estuary.

Shellmycin A-D, Novel Bioactive Tetrahydroanthra-γ-Pyrone Antibiotics from Marine Streptomyces sp. Shell-016

Four novel bioactive tetrahydroanthra-γ-pyrone compounds, shellmycin A-D (1-4), were isolated from the marine Streptomyces sp. shell-016 derived from a shell sediment sample collected from Binzhou Shell Dike Island and Wetland National Nature Reserve, China. The structures of these four compounds were established by interpretation of 1D and 2D NMR and HR-MS data, in which the absolute configuration of 1 was confirmed by single crystal X-ray diffraction, and compound 3 and 4 are a pair of stereoisomers. Compound 1-4 exhibited cytotoxic activity against five cancer cell lines with the IC₅₀ value from 0.69 μM to 26.3 μM. Based on their structure-activity relationship, the putative biosynthetic pathways of these four compounds were also discussed.