Microbial Biodiversity Maintained

wide sweeping view of a valley of purple heather, with a blue sky and green rolling hills in the backround

Biological Strategy

Heather moorland

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Image: Simon Harrod / Flickr / CC BY - Creative Commons Attribution alone

Cycle Nutrients

In ecosystems, there is no such thing as waste. Instead, one organism’s waste can be considered as another organism’s resource, and the cycling of nutrients may be the most important form of recycling in living systems. But sometimes those nutrients are transformed by one organism into a form that isn’t readily used by other organisms. For example, lignin is a complex organic molecule found in the cell walls of plants. In a forest, it’s one of the hardest molecules to break down in woody vegetation. Therefore, ecosystems include organisms that are particularly well-adapted to break down different types of nutrients. In the case of lignin, some fungi and bacteria release lignin-modifying enzymes that can break down the lignin to form carbohydrates and other life-supporting chemicals.

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Generate Soil/Renew Fertility

An ecosystem can’t survive long without building up its soils and preventing them from being depleted of fertility. Organic matter, minerals, and other nutrients in soil support organisms, from microorganisms to the largest mammals. Raw soil consists of weathered minerals, such as silica. But organisms need more than minerals to survive, and minerals alone are poor at storing water needed by organisms. Therefore, soil has organic matter to support an ecosystem of organisms that, in turn, contribute more organic matter, make nutrients more accessible, and hold water. The dung beetle is an organism that enhances soil fertility. This beetle gathers and transports animal dung, feeds on it, buries it in the soil, and lays eggs on it. The dung provides its young with food when they hatch. At the same time, it adds nutrients and organic matter to the soil, benefitting the ecosystem as a whole.

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Maintain Biodiversity

The greater the amount of genetic and species variation in an ecosystem, the more resilient that ecosystem is to disturbances. Variation in ecosystems across the Earth also contributes to the Earth’s resilience to unpredictable changes. This variation is called biodiversity. Because living systems compete with each other for scarce resources, maintaining biodiversity involves creating conditions for a large variety of species to successfully co-occur and reproduce. For example, within a wetland, there are different vegetation types. This diversity results in a complex mosaic of microenvironments as the vegetation types alter air flows, light regimes, and water temperatures and chemistry. Because organisms vary in their ideal environmental conditions, these micro-environments increase the diversity of plants in the wetland. In turn, having a wetland in an otherwise dry area increases biodiversity at an even larger scale.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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The soil microbial community of heather moorlands is kept in balance by above-ground ecosystem engineers.

“Ecosystem engineering by a single species can have a cascading effect on many ecosystem processes. While the impact of above-ground ecological engineers on soil chemical properties has been studied, few studies have assessed their impact on the soil microbial community, which is largely responsible for many ecosystem functions.” (Mitchell et al. 2010:50)

“Utilizing a long-term experiment where birch was planted on heather moorland 20 years ago, the engineering impact of a single tree species (Betula pubescens) on the soil microbial community was assessed…Changes in the soil microbial community were then related to soil chemical and physical variables and tree performance variables.” (Mitchell et al. 2010:50)

“Under birch, total microbial biomass (total PLFA–[phospholipid fatty acid profiling]) declined, species richness increased and the ratio of fungal : bacterial PLFA declined. The fungal PLFA marker increased with increasing organic matter and depth of the LFH and O soil horizons, characteristics associated with moorland soils. Bacterial PLFAs increased with increasing birch canopy cover. The fungal community of the birch plots was different from that in the heather plots and changes in the fungal community composition were related to the size of the birch trees in the plots.” (Mitchell et al. 2010:50)

“Changes in the soil microbial community were also related to changes in mineralizable N [nitrogen]. Mineralizable N was correlated with both decreasing total soil microbial biomass and decreasing fungal : bacterial ratio.” (Mitchell et al. 2010:50)

“The durability of the engineering effects of birch was studied in a second experiment. Plots were established in first-generation birch woodland that had developed on Calluna-dominated moorland. The plots were cleared of birch and planted with heather. After 20 years, there was no difference in the community composition of the PLFAs. In contrast, there were significant differences in the fungal community composition as judged by DGGE [denaturing gradient gel electrophoresis] analysis, with the fungal community in the felled birch plots being similar to the heather moorland.” (Mitchell et al. 2010:50)

“This work demonstrates that addition of a single tree species to heather moorland results in changes in below-ground soil microbial communities and in nutrient cycling.” (Mitchell et al. 2010:50)

Last Updated August 18, 2016

References

Journal article

The ecological engineering impact of a single tree species on the soil microbial community

Journal of Ecology | 19/11/2009 | Ruth J. Mitchell, Colin D. Campbell, Stephen J. Chapman, Clare M. Cameron

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