Plant diversity. Courtesy photo

BY OWEN HABLUTZEL
For Chama Peak Land Alliance’s
Backyard Biodiversity series

Plant diversity has a very long, widespread history of human use as a strategy for improving agricultural and land management outcomes. Here in New Mexico (and across Meso-America) the “3-sisters” tradition—growing corn, beans and squash together for mutual benefits—is a well-known example. Tewa variations of this add a “4th sister”pollinator species—such as rocky mountain beeplant—further boosting overall productivity.

Modern science has also well documented the agricultural and ecological benefits of
greater plant biodiversity, including:

 Higher productivity  More stable, reliable production
 Better resilience and resistance to stresses
 Improved nutrient cycling
 Better habitat supporting further biodiversity

In recent years, soil science has accumulated many insights about the role of soil microbiology in generating these impacts. Major new findings suggest that these living soil communities are largely the factor responsible for the previously identified benefits of ‘plant diversity.’ In fact, diversity of the plant ‘microbiomes’ (not merely the plants) are the key.

Just as individual humans carry a ‘microbiome’ (a community of microscopic organisms—microbes—supporting our immune system, digestive system and more), plants too host and require their own specific microbe communities. Root systems of healthy plants, for example, are sheathed with a vibrant microbiome, including beneficial bacteria, fungi, protozoa and more.

After gathering energy from sunlight (photosynthesis), plants share a large portion of that energy with this root-microbiome–as sugars, aminos, proteins and other organic molecules. Plants are happy to nourish microbial communities as they receive great benefits from them, including nutrients, and protection from disease, floods, and drought. Microbial activities are also what builds good soils–creating soil structure, making soil minerals available and adding organic matter that increases soil water-holding capacity and fertility.

Soil science has learned that plants function best with a high diversity of microbes living around roots. Each different functional group or ‘family’ of plants (grasses, legumes, brassicas, sunflowers/daisies, buckwheat, pollinator plants) supports a different microbiome (different sets of microbial species). When we grow plants from several different families together the diversity of the whole soil micro-community is greatly increased, and plants in that neighborhood function better for it. When plants of different functional types grow next to each other their root systems are able to ‘mingle,’ until the individual plant microbiomes become connected into a larger system for sharing energy and nutrients. A kind of micro-society or network forms, benefiting all plants involved.

For example, when a plant in this shared network experiences drought stress, microbes from drought tolerant plant species in that neighborhood are recruited and shared with the stressed plant. This plant will then be able–with the assistance of microbes–to thicken cell walls, reduce moisture loss and overall drought stress. An incredible amount of communication happens between plants and the microbiome networks to achieve this, which science is only beginning to grasp the full language of.

Experiments have shown (including the 24 year-long Jena plant-diversity experiment in Germany) that these benefits really take-off when at least four different plant families (functional groups) are grown together. More than four is even better, but four is an important threshold to best tap into the network effects.

When plants from differing families (having different microbiomes) are grown together they recognize their neighbors have something to offer that they don’t already have. Because of this their microbiomes are open to mutual exchanges with neighbors. Alternatively, when growing in a community with only a single plant family (all grass plants, for example), even if there are many species involved, the microbiome exchange modes are shut down. Instead, they go more into competition mode since there is nothing neighboring microbiomes have to offer that they don’t already have themselves.

In light of this recent understanding it seems the ‘4th, 5th or 8th sister’ (from different functional group/family) is well worth considering for your garden or pasture, or anywhere greater productivity, stress resistance and soil building are part of your management goals.

Backyard Biodiversity is a series of educational articles brought to you in partnership with local conservationists, scientists, and biologists and Chama Peak Land Alliance. The series highlights the unique and special nature of our area, in the hope that each of us can and will improve our backyards and communities by ensuring biodiversity.

Submitted by Sage Faulkner, Chama Peak Land Alliance sage@chamapeak.org

Author, Owen Hablutzel consults & offers workshops for regenerative ranch/farm/property planning, design & management (LFMRANCHING.COM). He lives with his wife and 3 children in Ensenada, NM. Email: go2owen@gmail.com