Image by Pexels from Pixabay.

Plants and soils are intricate partners of well being for each other. Plants absorb water and nutrients from the soil, while the soil is home to thousands of microbes.

As plants grow, they alter soil biology, interfere with the chemistry of soil microbial communities, which in turn affects plant health, phenology. This complex network of interactions between plants and soil leads to the foundations of a feedback system called plant-soil feedback.

Plant-soil feedbacks vary from positive to negative mechanisms. These mechanisms are dependent on soil natural communities (consist of beneficial microbes to pathogenic) and plant behavior (made up of litter production and the nutrients that are released by plants into the soil).

Availability of nutrients and accumulation of microbes (ranging from symbiotic, mutualistic to aggressive pathogenic) determines the nature of the feedback system: positive or negative.

When plants can grow healthily in soil with strong litter (dead plant leaves or parts), production on their latter growth stages is characterized as positive plant-soil feedback (PSF), while negative feedback occurred when plants are less able to grow in soil.

A representation of plant-soil feedback (PSF) mechanisms by Putten et al.

The image below is for the understanding of “how the feedbacks between plants and soils work and control plant’s performance?” The red and blue colored arrows represent the negative and positive feedback mechanisms, while the thickness of the black colored arrows indicates the strength of mechanisms.

The dashed arrows are representations of plant-plant interactions.

Credit: https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.12054

Many factors influence the mechanisms of plant-soil feedbacks. These factors include the availability of nutrients, soil microbial communities, for example, symbionts, mutualists (arbuscular mycorhizal fungi), or invasive pathogens ( Fusarium spp.).

Primary factors that influence plant-soil feedback

Nutrients or plant food determine the process of plant-soil feedbacks. The depletion of nutrients causes negative plant-soil feedback by restricting plant growth. The reductions in plant growth influence the litter quality, which reduces nutrient inputs into the soil.

Soil microbial communities have a significant influence on the plant-soil feedback system. Soil symbionts (arbuscular mycorrhizas) contribute to positive plant-soil feedback through the accumulation of beneficial microbes around the plant roots.

These microorganisms ameliorate the plant’s rhizosphere by the decomposition of organic matter and, thereby, enhancing the plant's performance.

Pathogens or plant enemies cause negative plant-soil feedback by reducing plant growth and development because they feed on plant roots like nematodes.

How Climate Change Affects the Plant-Soil Feedback (PSF) or Soil Microbe-Microbe and Plant-Microbe Interactions.

Climate factors (temperature, moisture, precipitation, drought) play a crucial role in the PSF that determines the health of both plants and soils. Soil hosts a wide range of microbial organisms that interact with each other and also with plant species.

These intra and interspecies interactions maintain a finite ecosystem. Climatic factors may influence such interactions, both directly and indirectly because many metabolic processes of soil biota are temperature-dependent.

Climate change affects the physiology, temperature sensitivity of soil communities and their abundance in a particular area. For instance, rainfall timing is a critical factor in soil biota diversity.

Temperature fluctuations and drought affect the relative abundance of certain soil bacterial and fungi. The sensitivity of these communities to temperature influence plant performance.

Temperature also plays a critical role in the composition of rhizosphere microbial communities. Rhizobia and mycorrhizas cause positive PSF by improving plant performance.

However, climate change causes restrictions in their activity or a sometimes complete shift in their physiology (from beneficial to harmful) due to drought and elevated temperatures.

Litter quality is another important factor in PSF and determines the functioning capability of soil decomposers. A positive plant-soil feedback system favors plant performance, which in turn produces high-quality litter.

This ultimately attracts more beneficial decomposers that breakdown the litter and add resources into the soil by conserving its moisture contents. Climate factors such as rainfall and drought are two critical components for high-quality litter production.

Rhizodeposits (release of resources from plant roots into the soil): a rich source of organic matter for soil health is also affected by climate change. Under high temperatures, the accumulation of pathogens in plant root zones encourages negative plant-soil feedbacks and risking both plant and soil health.

Climate factors play a critical role in the physiology and community composition of soil biota. Soil biota is not only vital for the plant’s health but also for soil health.

Changes in climatic factors have the potential to turn beneficial microbes into harmful ones. These modifications risk plant growth and reproduction, litter production, and soil organic matter. Litter is also critical for soil health because it covers the soil surface and prevents moisture, and adds nutrients into the soil.

Temperature fluctuations cause the shifting of microbial communities, thus, limiting their diversity.

A complete understanding of these interactions and their sensitivity towards climate change may help in the preservation of soil communities and of plants.