Current unprecedented species extinction has galvanized studies to clarify how biodiversity affects diseases. However, almost all empirical studies focused on diseases at a certain time point, largely ignoring the temporal stability. Using a removal experiment that manipulates plant diversity, and a fertilization experiment in a Tibetan alpine meadow, we investigated how different plant biodiversity indices and nitrogen fertilization affect the temporal stability of community pathogen load over seven consecutive years. We found that the temporal stability of foliar fungal diseases increased with plant diversity indices, among which phylogenetic diversity was the best predictor. The analyses based on Taylor’s law indicated that host plant species richness changed the scaling between logarithmic mean and variance. We also found positive relationships between phylogenetic diversity and the temporal stability of community pathogen load at species richness levels of 2 and 4. However, nitrogen fertilization weakened the positive effect of plant (phylogenetic) diversity on the temporal stability of pathogen load by increasing both the mean and standard deviation of pathogen load. We concluded that although host diversity regulated the temporal stability of pathogen load, suppressing disease fluctuation over time by increasing host diversity may be challenging in the context of the Anthropocene.

We conducted the experiment 1 and 2 in an alpine meadow, please see our previous paper for more details about experiment design (Liu et al. 2016). Here, we recorded foliar fungal disease severity (V_i; i.e., % leaf area covered by fungal lesions) every August (the peak of the growing season). In short, for each plant species in each plot, we randomly recorded 5 leaves from each of 5 randomly selected individuals, therefore 25 leaves per species per plot. At the same time, we also arranged one 0.5 × 0.5 m subplot in each plot, harvested all the aboveground parts and sorted to species, then recorded plant species richness and abundance for each species. We used the abovementioned methods to conduct sampling of both foliar fungal pathogens and plant communities for seven consecutive years (2014 to 2020).

Reference:

Liu X, Lyu SM, Zhou SR, Bradshaw CJA. 2016 Warming and fertilization alter the dilution effect of host diversity on disease severity. Ecology 97, 1680-1689. (doi:10.1890/15-1784.1)