Plant-soil feedback across spatiotemporal scales from immediate effects to legacy

Plants and soil biota are important ecosystem engineers interacting via plant-soil feedback on large gradient of temporal scales from immediate interactions to long term legacy, which also operate on various spatial scales. Here I emphasize three major pathways of plant-soil feedbacks: i) the biota pathway, when plants affect soil biota, such as plant symbionts or antagonists, which affect plants, ii) the soil pathway, when plants affect soil environment, which then feedbacks to plants and finally iii) the biota-soil pathway, when plants affect soil biota, which then affect soil environment, which then effect plants. Living plant roots are major driver for biota pathway, which is more important for immediate effect, while litter largely supports the biota-soil pathway important for legacy effects. Many processes that have immediate effects, produce also small but more persistent changes in soil. Legacy is produced by accumulation of this small changes over time. This is supported by soil ability to preserve and accumulate, these small changes. Legacy also alternate outcome of immediate interactions between plants, soil and soil biota. The soil property changes, caused by legacy, happen either as slow gradual changes, or relatively fast, abrupt shifting between two steady states. In both cases, soil changes can reach tipping points, altering functioning of whole plant soil system. Apart from plants, also soil conditions or soil biota can be manipulated either intentionally (e.g. by land uses change, various agriculture, forestry or ecosystem restoration practices), or non-intentionally (e.g. biological invasion), which trigger changes in plant – soil - soil biota interactions as described above and cause immediate and legacy effects. Examples, presented in this review, suggest that legacy effect is particularly important in soils in early stages of pedogenesis or during response to or recovery after disturbance. Review highlight necessity studying plant soil feedback on all relevant spatiotemporal scales.