The artificial fertilization of soils can alter the structure of natural plant communities and exacerbate pathogen emergence and transmission. Although the direct effects of fertilization on disease resistance in plants have received some research attention, its indirect effects of altered community structure on the severity of fungal disease infection remain largely uninvestigated. We designed manipulation experiments in natural assemblages of Tibetan alpine meadow vegetation along a nitrogen-fertilization gradient over 5 years to compare the relative importance of direct and indirect effects of fertilization on foliar fungal infections at the community level. We found that species with lower proneness to pathogens were more likely to be extirpated following fertilization, such that community-level competence of disease, and thus community pathogen load, increased with the intensity of fertilization. The amount of nitrogen added (direct effect) and community disease competence (indirect effect) provided the most parsimonious combination of parameters explaining the variation in disease severity. Our experiment provides a mechanistic explanation for the dilution effect in fertilized, natural assemblages in a highly specific pathogen-host system, and thus insights into the consequences of human ecosystem modifications on the dynamics of infectious diseases.

With increasing attention being paid to the consequences of global biodiversity losses, several recent studies have demonstrated that realistic species losses can have larger impacts than random species losses on community productivity and resilience. However, little is known about the effects of the order in which species are lost on biodiversity–disease relationships. Using a multiyear nitrogen addition and artificial warming experiment in natural assemblages of alpine meadow vegetation on the Qinghai‐Tibetan Plateau, we inferred the sequence of plant species losses under fertilization/warming. Then the sequence of species losses under fertilization/warming was used to simulate the species loss orders (both realistic and random) in an adjacently novel removal experiment manipulating plot‐level plant diversity. We explicitly compared the effect sizes of random versus realistic species losses simulated from fertilization/warming on plant foliar fungal diseases. We found that realistic species losses simulated from fertilization had greater effects than random losses on fungal diseases, and that species identity drove the diversity–disease relationship. Moreover, the plant species most prone to foliar fungal diseases were also the least vulnerable to extinction under fertilization, demonstrating the importance of protecting low competence species (the ability to maintain and transmit fungal infections was low) to impede the spread of infectious disease. In contrast, there was no difference between random and realistic species loss scenarios simulated from experimental warming (or the combination of warming and fertilization) on the diversity–disease relationship, indicating that the functional consequences of species losses may vary under different drivers.

The nickel hydroxides (β-Ni(OH)2) with different shapes such as hexagonal nanosheets, irregular nanosheets, and nanoparticles were synthesized in the absence of SO4 2− ions and in the presence of 0.00−3.00 mmol of the added NaOH using a hydrothermal method. The β-Ni(OH)2 phase with brucite-type structure was confirmed by an energy-dispersive spectrum (EDS), Fourier transform infrared spectra (FTIR), and powder X-ray diffraction (XRD). The effect of the free OH− ions and the SO4 2− ions in the hydrothermal system on morphologies of the Ni(OH)2 products was investigated in detail. In the absence of SO4 2− ions system, when the added NaOH amount is less than 0.02 mmol, the irregular thin nickel hydroxide nanosheets with thickness of about 20−50 nm were obtained; when the added NaOH amount is between 0.35 and 0.55 mmol, the products have the regular hexagonal morphology with a width of 150−500 nm and thickness of 40−80 nm; while when the added NaOH amount is 1.50−3.00 mmol, the nickel hydroxide products became polyhedral nanoparticles with an average diameter of ca. 50−90 nm. The Ni(SO4)0.3(OH)1.4 nanowires or α-Ni(OH)2 nanowires containing the intercalated SO4 2− anions can only be obtained in the presence of SO4 2− ions. They have lengths of several micrometers and widths of 20−30 nm. A possible growth mechanism of the nanosheets, nanoparticles, and nanowires is suggested.