Tracing the Transformation and Allocation of the Newly Applied-P in Calcareous Soil Using an Enriched Oxygen Isotope Labeling Technique.

Different phosphorus (P) fertilizations significantly impact the transformation of the applied-P in soils. However, knowledge about how different P fertilization regimes influence the allocation of the amended-P in soil remains incomplete. Herein, we carried out a pot experiment to explore the fate of applied-P in calcareous soil using an oxygen isotope labeling technique (18O-P18O43-). Treatments included check (CK), single, and repeated applications. The phosphorus mass balance result showed that more than 48.5% of the applied-P was held in labile and moderately labile fractions with the repeated treatment, while approximately 27.4% of the added-P was recovered in nonlabile forms in the single application treatment. The isotopic tracer (18O-P18O43-) result demonstrated that the δ18OP values of NaHCO3-P and NaOH-P in the repeated P application were significantly higher than those in the single P application. Ultimately, better agronomic performances of the crops and higher PUE were achieved in the repeated treatment. Our findings highlighted that repeated P fertilization can improve P availability by reducing P fixation. These results pronounced that the enriched oxygen isotope technique can be considered an effective approach for tracing applied-P in soils.

Nitrapyrin Addition Mitigated CO2 Emission from a Calcareous Soil Was Closely Associated with Its Effect on Decreasing Cellulolytic Fungal Community Diversity.

Application of nitrification inhibitors (NIs) has been widely used to inhibit nitrification and reduce N2O emissions. However, the impacts of NI addition on soil carbon transformation and carbon-degrading microbial communities have not been well explored. Here, a microcosm experiment was carried out, and four treatments were designed: (i) unfertilized control, (ii) urea alone, (iii) urea plus cattle manure, and (iv) urea plus cattle manure with nitrapyrin. The influence of nitrapyrin on soil CO2 emissions, carbon-degrading extracellular enzyme activities, and the abundance and diversity of the cbhI community was investigated. Compared to the treatment of urea plus cattle manure, nitrapyrin significantly decreased cumulative CO2 emissions by 51.8%. Moreover, cbhI community gene copies and their α-diversities (P < 0.05) were also significantly reduced by nitrapyrin application. A partial least squares path model showed that CO2 emission was positively associated with cbhI community α-diversity but negatively associated with nitrapyrin addition. We conclude that the mitigation of soil CO2 emissions by nitrapyrin can be ascribed to its effects on decreasing of cellulose-degrading gene community diversity. Our findings provide new insights into the side-effects of nitrapyrin on abating CO2 emission.

New taxa of Berberis (Berberidaceae) with greenish flowers from a biodiversity hotspot in Sichuan Province, China.

A new species, Berberis viridiflora X. H. Li, and a new variety, Berberis sanguinea Franch. var. viridisepala X. H. Li, L. C. Zhang & W. H. Li are described and illustrated from Baoxing County, a biodiversity hotspot located on the eastern edge of Hengduan Mountains in Sichuan Province, Southwest China. Both new taxa resemble B. sanguinea Franch. var. sanguinea, but B. viridiflora differs by the greenish flowers, and the petals being truncate, obtuse, or undulate at apex; while B. sanguinea var. viridisepala differs by the greenish or yellowish green flowers. Morphological features of the pollen grains of B. sanguinea and the two new taxa are revealed by scanning electron microscope. B. sanguinea var. sanguinea displays obvious similarities with a sympatric congener, Berberis multiovula T. S. Ying in the morphology of flowers, stems and leaves, especially its ovule number varies greatly from 2 to 9, thus, B. multiovula characterized by the 5-ovuled ovary is reduced to a synonymy of B. sanguinea var. sanguinea. On the basis of field surveys and study of herbarium specimens, a total of 16 species and varieties of Berberis are recorded from Baoxing County, and a key is provided. Among the 16 taxa, most phenotypic variations in Chinese Berberis can be displayed, including the habit of plants, most morphological variations of stems, branches and leaves, all types of inflorescences, all color types of flowers, and nearly all types of the shape and color of fruits. Baoxing County and its adjacent Sichuan Giant Panda Sanctuaries possibly constitute an active diversification center of Berberis in eastern Hengduan Mountains of China.