Effect of environmental factors on negative plant-soil feedback in a subtropical forest

Background/Question/Methods

Recent studies have provided strong evidence that the density- or distance-dependent mortality plays an important role in the maintenance of plant diversity. The mechanisms have remained speculative and it was thought that a soil-plant feedback system was responsible for this effect. Our recent studies have confirmed that soil fungi are in fact responsible for this negative plant-soil feedback system and that these fungi are host-specific. However, less is known about how environmental factors such as soil temperature and humidity might influence the negative plant-soil feedback caused by soil pathogens in the forest type ecosystems. Here we conducted a greenhouse experiment to determine whether the magnitude of negative feedback was affected by environmental factors and whether the effect differs between intermediate trees and shade-intolerant trees. Two dominant species in a subtropical forest were selected, Cryptocarya concinna is an intermediate tree while Schima superba is a shade-intolerant tree. The negative plant-soil feedback was determined by comparing performance in the sterilized and non-sterilized soils. In order to test the impact of environmental factors and seed density on the negative plant-soil feedback interactions, the experiment was performed at two soil temperatures treatment, two soil humidity and two seed density level alternately.

Results/Conclusions

The impact of soil temperature on negative plant-soil feedback strength occurred mainly in the seed germination and the seedling survival phase, while the impact of soil humidity in the seedling growth phase. Soil respiration and the feedback strength of both species were greater in high temperature than that in low temperature, and the two species had different response to the soil humidity. The intermediate tree Cryptocarya concinna had greater soil respiration and stronger feedback strength in high soil humidity, while the shade-intolerant tree Schima superba had greater soil respiration and stronger feedback strength in low soil humidity. For both species, there was stronger feedback strength in high seed density than that in low seed density. Cryptocarya concinna were vulnerable to pathogens in hot and moist environment of the understory, its seedling mortality was increased in forest understory. Schima superba were easily injured by pathogens in the hot and dry environment of gap, its seedling mortality was high in forest gap. The negative plant-soil feedback limited the seed-to-seedling recruitment and then promoting the species coexistence.