What is planting resilience, plant plasticity & structural diversity?
Added on 24 January 2023
Planting resilience:
Individual species rarely flower throughout the growing season from early spring to late autumn. Depending on the species flowering may be days, weeks, months or perhaps two periods of flowering in a season. By selecting a number of species that flower at different times we hope to ensure the beauty of flower colour as the growing season progresses. Considering wildlife these species should also be selected to provide nectar for a wide range of pollinating insects throughout the year. Here thought should also be given to the resilience or stability of the planting. How well the planting display can respond and can continue to function or recover quickly when experiencing either a disturbance such as temporary flooding or a perturbation (shift or swing) such as evidenced increasingly by climate change with increasing temperatures leading to drought conditions becoming more common and prolonged. Using ecological wording we look a the ability of a planting to be resilient or stable in terms of functional redundancy and response diversity. Although we as gardeners are particularly concerned with plants we must remember on an ecological level these terms apply to other living organisms making up the complex interactions in the planting or habitat; bacteria, nematodes, fungi etc.
Functional redundancy :
In the garden an ecologically based planting scheme will not just provide an visually engaging year round aesthetic service but a service to; for example bees collecting honey, water or nesting materials and in turn pollinating other plants whose seeds and berries will germinate continuing the species or providing food for other wildlife. As mentioned above plant species tend to flower for a short period in the season so the number of species that can extend the flowering and in turn pollinator season will extend that resource to the bees. We are not just looking for one or two plant species to provide a source of nectar, but overlapping bloom times from multiple species (nectar resources) so the flow of nectar is continuous throughout the season from April to October. When considering plant choices for insects we must not just consider flowers for pollinators but also plants favourable to predators such as grasses and shrubs for spiders, ladybirds, beetles etc which also prey on plant pests.
Response diversity:
This is the collective response of the individual plant species in a planting to change. In the case of flowering plants for nectar collection and pollination the resource must be available during periods of flood or drought. This acts as a buffer against possible loss of individual pollinator species. Ideally the planting must not only have the capability to restore itself but have the capacity for transformation should an event such as periodic drought becoming more frequent or lasting longer. Observant human intervention may be necessary to add more suitable species or remove poor performers so pollinators continue to have a source of nectar.
Both these factors must be considered when designing an ecological based planting scheme adaptable to climate change. How quickly can the planting habitat recover or adapt?Most ecologically based schemes focus on generalist pollinators for bees and butterflies assuming that natures adaptive resilience will supply the other elements of biodiversity, especially the decomposers; bacteria, nematodes fungi etc which seems to recover resulting in a stable healthy habitat.
Plant plasticity:
Plasticity refers to how well an individual plant species performs across a range of changing environmental conditions remembering that unlike animals they cannot move themselves to a more favourable situation or evolve in their life time to cope with the environmental change. Their ability to tolerate extremes of temperature or fluctuations in soil moisture from prolonged drought conditions to flooding until conditions return to normal. Other plant plasticity factors that a plant species must cope with are changes in light levels, soil type, flowering times and length, ability to set seed/berry. Salt spray from coastal areas and urban pollution are also factors considered in plant plasticity.
Structural plant diversity
The woody structure of evergreen and deciduous trees, shrubs, climbers and ground cover plants with their added overall form texture and size together with similar attributes of flowering herbaceous perennials and grasses provide an abundance of habitat for shelter, space for nesting, foraging and reproduction for biodiversity. Larger woody plants can provide shade in strong sun, preventing desiccation of otherwise exposed organisms lower as well as a safe elevated refuge for wildlife when ground conditions are waterlogged. Ken Thompson’s scientific research on garden habitat showed that trees and shrubs are a constant garden feature that is positive to wildlife.