Shading and litter mediate the effects of soil fertility on the performance of an understorey herb

Abstract

Background and Aims Soil fertility and topographic microclimate are common determinants of plant species distributions. However, biotic conditions also vary along these abiotic gradients, and may mediate their effects on plants. In this study, we investigated whether soils and topographic microclimate acted directly on the performance of a focal understorey plant, or indirectly via changing biotic conditions.Methods We examined direct and indirect relationships between abiotic variables (soil fertility and topographic microclimate) and biotic factors (overstorey and understorey cover, litter depth and mycorrhizal colonization) and the occurrence, density and flowering of a common understorey herb, Trientalis latifolia, in the Klamath-Siskiyou Mountains, Oregon, USA.Results We found that the positive effects of soil fertility on Trientalis occurrence were mediated by greater overstorey shading and deeper litter. However, we did not find any effects of topographic microclimate on Trientalis distribution that were mediated by the biotic variables we measured. The predictive success of Trientalis species distribution models with soils and topographic microclimate increased by 12 % with the addition of the biotic variables.Conclusions Our results reinforce the idea that species distributions are the outcome of interrelated abiotic gradients and biotic interactions, and suggest that biotic conditions, such as overstorey density, should be included in species distribution models if data are available.

How does spatial micro‐environmental heterogeneity influence seedling recruitment in ironstone outcrops?

“…For instance, a legume shrub affects species composition and abundance in calcareous soils by increasing nitrogen availability, but these effects may disappear in unusually dry years (Michalet et al, 2015). A process with the reverse mechanism is also possible: soil fertility promotes the occurrence of an understorey herb on serpentine soils by causing positive effects on overstorey cover, leading to more shading and increased litter depth (Copeland & Harrison, 2016).…”

Effects of vegetation, terrain and soil layer depth on eight soil chemical properties and soil fertility based on hybrid methods at urban forest scale in a typical loess hilly region of China

“…The eight soil chemical properties (SCPs), comprising total nitrogen (TN), total potassium (TK), total potassium (TP), available nitrogen (AN), available phosphorus (AP), available potassium (AK) and organic matter (OM) are important chemical components of soil fertility. Hence, spatially continuous mapping of these soil chemical properties and soil fertility is required to facilitate the sustainable management of land resources in precision agriculture and forestry [ 3 – 5 ], while it is also helpful to understand the belowground food webs [ 6 ], plant species distributions [ 7 ], and other factors. However, abundant observations of soil properties cannot always be obtained easily across a large landscape because of cost and time constraints on soil sampling and analysis [ 8 ].…”