Effects of Soil Nutrient Heterogeneity on the Growth and Invasion Success of Alien Plants: A Multi-Species Study

Spatial heterogeneity in soil nutrient availability can influence performance of invasive plant species under competition-free environments. However, little was known about whether invasive plants perform better under heterogeneous than under homogeneous soil nutrient conditions in competition with native plant communities. We conducted a multi-species greenhouse experiment to test the effect of soil nutrient heterogeneity on the growth and invasion success of alien plants in a native plant community. We grew ten alien invasive plant species that are common in China under a homogeneous or heterogeneous environment alone or together with a community consisting of six native plant species from China. Compared with the homogeneous soil condition, the heterogeneous soil condition significantly increased aboveground biomass of the invasive plants. However, soil nutrient heterogeneity did not affect the relative abundance of the invasive species, as measured by the ratio of aboveground biomass of the invasive species to total aboveground biomass of the whole community. There were no significant interactive effects of soil nutrient heterogeneity and competition from the native community on aboveground biomass of the invasive plants and also no significant effects of soil nutrient heterogeneity on its relative abundance. Our results indicate that soil nutrient heterogeneity has a positive effect on the growth of invasive plants in general, but do not support the idea that soil nutrient heterogeneity favors the invasion success of exotic plant species in native plant communities.

Heterogeneity of soil nutrients in ecosystems: a review of methodology, variability and impact factors

Soil nutrient heterogeneity highly correlates to plant growth and development of environmental quality. In order to better understand nutrient cycling, heterogeneity of soil nutrients and their driving mechanism in different land use types were summarized from 1945 to 2016. By grouping keywords indexed in the titles of articles from the data base of Web of Science, two hundred and thirty one publications related to our topics were used for analysis. Soil sampling and statistical method were compared, and spatial dependence and the impact factors for soil organic matter (SOM), Nitrogen (N), Phosphorus (P) and Potassium (K). The results showed that soil nutrient heterogeneity was influenced by different factors at different scales. The spatial dependence of SOM, N and P were mainly at the moderate level (48.9-59.0%) and strong level (33.3-42.2%), while for K was at strong level (63.6-84.6%) and moderate level (15.4-36.4%). This was mainly influenced by topography, soil loss, weather condition, parent material, soil type, soil texture, land use, human activities, soil moisture, mineral element, soil structure, animal and plant. These impact factors were summarized separately, and the influence of factors at different spatiotemporal scales was discussed. At the end of the review, the ideas for further research were postulated.

Termites mitigate the effects of drought in tropical rainforest

Termites perform key ecological functions in tropical ecosystems, are strongly affected by variation in rainfall, and respond negatively to habitat disturbance. However, it is not known how the projected increase in frequency and severity of droughts in tropical rainforests will alter termite communities and the maintenance of ecosystem processes. Using a large-scale termite suppression experiment, we found that termite activity and abundance increased during drought in a Bornean forest. This increase resulted in accelerated litter decomposition, elevated soil moisture, greater soil nutrient heterogeneity, and higher seedling survival rates during the extreme El Niño drought of 2015–2016. Our work shows how an invertebrate group enhances ecosystem resistance to drought, providing evidence that the dual stressors of climate change and anthropogenic shifts in biotic communities will have various negative consequences for the maintenance of rainforest ecosystems.