Increasing botanical biodiversity in old crop fields

Case Study: Sean Altern – Consultant: Biodiversity Conservation Services
26 June 2019

Setting up of experimental plots – Paul Cluver Wines

Attempts to increase botanical bounties: How biomimicry management interventions can be used as vegetation drivers to increase botanical biodiversity in old crop fields.

Background

Renosterveld is a type of vegetation comprising certain indigenous plant species that grow on a particular soil type which has a more favourable nutrient makeup than typical fynbos. Consequently many of these areas have since been transformed into the crop fields that produce the food items that we find in the shops and that fill our stomachs. From time to time these fields become worn out or are no longer farmed thus being left to naturally recover. Unfortunately the activities of farming on these areas have limited the ability of these areas to recover fully on their own as evidenced by very limited natural species diversity. These areas thus require outside interventions to enable the process’ or ‘vegetation drivers’ to restore these sections of land. Paul Cluver Wines, based in the Elgin basin, is passionate about conserving the environment, not just in terms of quantity but quality, and has invested in multiple projects to rehabilitate and restore portions of the De Rust Estate. NCC Environmental Services was contracted to implement a project to improve the limited biodiversity on an old renosterveld field that forms an important biodiversity corridor across the Estate, stretching into the Groenlandberg Conservancy.

Renosterveld corridor on De Rust Estate.

Designing a customised solution

It is not always necessary to re-invent the wheel, rather, the correct wheel simply needs to be found and fitted so to speak. Many formal studies have been conducted on techniques for restoration of renosterveld; please refer to the reference section below for some of these great reports. Along with reviewing what we already know about restoration techniques, a good understanding of what creates or ‘drives’ the vegetation type and an analysis of the site itself, is imperative in guiding what process’ need to be restored to assist the recovery of the vegetation. Along with this, much consideration was also given to practicality, affordability and whether the ideas are realistic. Many well intentioned plans fail because they are either over-elaborate, too large or driven by impractical perfectionism rather than being thoughtfully simple and feasible.

With these considerations in mind, knowledge of the site and vegetation drivers, NCC selected three methods to further trial in small sections within the old field. The objective of these trials, was to discover which of the methods will produce the greatest increase in species numbers on site. Once the best method was identified, this technique would be used for the remainder of the site. A proposal was drafted and with the review and support of CapeNature, the following techniques were tested:

Fire – Fire is an integral driver in renosterveld. It replenishes the soil with ash nutrients, limits competition and allows increased light and moisture to penetrate the soil. With an ecological burn being impractical, and research suggesting that brush cutting could replicate many of the effects of a fire(e.g. an increased light penetration), this method was adopted.

Bird Perches – Many frugivorous birds, those which eat and later drop seeds in a process known as endozoochory, are responsible for dispersing the edible seeds of large berry bushes. Generally a bird will find a taller bush to sit on, dropping the seeds which then germinate forming taller bush clump areas. The naturally recovering fields generally do not have any of these taller species present to function as perching areas and as such the artificial addition of such perches, allows this vegetation driver to reoccur within the field.

Seeds – Seed dispersal is a fascinating subject and can take place in many ways. Some seeds are wind dispersed (anemochory), others have hooks to catch onto passing animals to be discarded elsewhere (epizoochory) whilst others may have nutritious elements covering the seed and are thus carried away and buried by insects such as ants (myrmechory). With the myriad of fields and fences found in rural landscapes resulting in habitat fragmentation, wind dispersal and animal movement is often limited and unable to be effective as areas are simply too far away or cut off. As such seed may need to be physically brought in from appropriate areas, in essence, mimicking the natural transportation.

Gathering indigenous seed.

Implementation

In order to get an idea of what the vegetation should comprise, a reference or ‘baseline’ renosterveld plot was found that displayed many of the same characteristics of the old field; topography, soil type, elevation etc but had never been ploughed thus being in a residual state. Species counts were then conducted in selected quadrants within this reference site and the experimental sites on the old field. On average the reference sites had double the number of indigenous species as that of the old field sites.

Work then began by implementing the various methodologies in different combinations in the experiential plots. Invasive alien vegetation tree trunks were cut and made into bird perches whilst brush cutting mowed sections down to soil level. Seed, sourced from both plucked foliage and soil stored locations in the form of raked mulch, was sustainably gathered from appropriate mirror sites and hand spread on the experiential sites. Each experiential site has been marked, photographed and will be annually analysed to discover what species have established as a result. It is envisaged that these plots can then slowly spread laterally and thus infiltrate the old field with generations of new plants and fresh seed.

Lessons learned

Once again restoration projects highlight how interconnect nature is and how something as simple as a fence can have far reaching impacts such as restricting not only animals but seed movement thus the vegetation diversity. Conservation management cannot simply leave areas to persist on their own where vital ecosystem drivers are missing or absent. As humans interventions have removed and altered eco-systems, both directly and indirectly, so to should management practises include the need to assist in recreating these processes for areas to survive and thrive as ‘naturally’ as possible.

Achieving real growth

NCC would like to applaud the team at De Rust and Paul Cluver Wines for going the extra mile, above and beyond what many people would deem ‘good enough’. De Rust and Paul Cluver Wines are always striving for the highest quality in everything they do, from fruit farming and wine making to the quality of their conservation areas. The results of experimentation could be the forerunner of how isolated areas should be conserved going forward. We hope publish some follow-up blog posts in due course to show the results over time – please keep following us.

Installing bird perches.

NCC Environmental Services Project Team

  • Sean Altern – Project Lead
  • Jonathan James Andrew Bell – GIS and Assistant Implementer

With thanks to:

  • Dr.Paul Cluver and the team at Paul Cluver Wines and De Rust Estate
  • Andrie Brink from CapeNature

References

  • Cowell,C.R. 2013. Investigating the most favourable seed establishment methods for restoring sand plain fynbos on old fields, Faculty of Applied Sciences at the Cape Peninsula University of Technology.
  • Esler,K.J., Pierce,S.M. & De Villiers,C. 2014. FYNBOS – Ecology and Management, Briza, Pretoria.
  • Ruwanza, S. 2017. Towards an integrated ecological restoration approach for abandoned agricultural fields in renosterveld, South Africa. S Afr J Sci. 2017
  • Walton, B.A. 2006. Vegetation Patterns and Dynamics of Renosterveld and Agter- Groeneberg Conservancy, Western Cape, South Africa. Thesis presented in partial fulfilment of the requirements for the degree of Master of Science at the Stellenbosch University.
  • www.overbergrenosterveld.org.za

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