Ecosystems Have Stability and Resiliency

mount kilimanjaro is seen in the background of a savanna landscape in africa during golden hour

Biological Strategy

Savanna ecosystem

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Manage Disturbance in a Community

When environmental conditions change, they can disrupt an ecosystem’s equilibrium. Excessive rain can cause flooding and drought can cause forest fires. An ecosystem must be resilient to such disturbances. Disturbances are unpredictable in location, size, and intensity, so ecosystems must be able to regrow and must have a variety of duplicate forms, processes, or systems that are dispersed in location. For example, a forest ecosystem can recover from fire because diverse organisms play different roles in different ways and in different locations. Many organisms can resprout or grow from seeds triggered by fire, and their dispersed distribution ensures that an entire population isn’t decimated. Though the recovered ecosystem may look totally different from the pre-fire one, the ecosystem as a whole remains healthy.

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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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a mountain with snow is in the background of a landscape with trees and shrubbery

Ecosystems

Eco- ("household"), system ("organized whole")

An ecosystem consists of all the biological and nonbiological elements that make up a defined area. That definition might seem vague, but that means it’s flexible: We can apply the word across different scales and times. Ecosystems can be small, like a single tide pool, or large, like coastal wetlands. Ecosystems can include plants, animals, bacteria, fungi, rocks, temperature, light, soil, and climate—all linked through the flow of energy and cycle of nutrients. Each part of an ecosystem interacts with, and is influenced by, other members of the system. These interactions are dynamic, leading to changes to any ecosystem over time.

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Savannahs have functional stability and resiliency due to unique properties of species and their interaction at system level.

“Knoop and Walker (1985) attributed the remarkable functional stability and resilience (ability to recover from change) of savannahs to unique properties of species and their interaction at system level. Special attributes include seed dormancy through seed bank recovery, vegetative reproduction, the presence of underground reserves and related coppicing ability, phenology of different species in relation to rainfall distribution and adaptations to drought and grazing. Parallel attributes of systems include the slow release of inorganic nitrogen, conservation of nutrients by vegetation, reduction of anaerobic conditions by trees and the trophic complementarity between species in system concerned.” (Van Noordwijk and Ong 1999:148)

“Recent insights into the effects of savannah trees on understorey vegetation and soils should provide valuable clues on how to reduce the negative effects of below-ground competition in agroforestry while retaining the positive effects of trees seen in natural ecosystems. It is this opportunity for agroforests to mimic the interactions between trees and other plants in natural ecosystems that led to the recent redefinition of agroforestry (Leakey, 1996), in which different agroforestry practices are viewed as stages in the development of an agroecological succession akin to the dynamics of natural ecosystems. Over time, the increasing integration of trees into land use systems through agroforestry can be seen as the passage towards a mature agroforest of increasing integrity. Similarly, with increasing scale, the integration of various agroforestry practices into the landscape is like the formation of a complex mosaic of patches in an ecosystem, each of which is composed of many niches. These niches are occupied by different organisms, making the system ecologically stable and biologically diverse (Leakey, 1996). In systems like this, the physiological interactions between the tree and crop components of the agroecosystem are more likely to mimic those of natural ecosystems.” (Ong and Leakey 1999:112)

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Last Updated August 28, 2020

References

Journal article

Interactions of Woody and Herbaceous Vegetation in a Southern African Savanna

The Journal of Ecology | 17/06/2006 | W. T. Knoop, B. H. Walker

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Reference

Journal article

Can the ecosystem mimic hypotheses be applied to farms in African savannahs?

Van Noordwijk M; Ong C

Journal article

Why tree-crop interactions in agroforestry appear at odds with tree-grass interactions in tropical savannahs

Ong, C. K.; Leakey, R. R. B.

Journal article

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