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Dirt poor but rich in diversity

Published 20 Mar 2015 

Ecologist Angela Sanders has been working on our Gondwana Link properties in the Fitz-Stirling region of Western Australia for 10 years. Monjebup Reserve is exceptionally rich in plant species and, in a twist of logic, poor soil (that is, low in nutrients, especially nitrogen and phosphorous) is one of the reasons.

Ecologist Angela Sanders (left) with botanist Libby Sandiford. Photo Jessica Wyld PhotographyOur ecologist Angela Sanders (left) with botanist Libby Sandiford. Photo by Jessica Wyld Photography

Over the past two springs flora surveys have been done on Monjebup, and a neighbouring property in the Gondwana Link project – Yarraweyah Falls.

Over 12 field days botanist Libby Sandiford and several volunteers covered around 1,200 hectares and identified 570 native plant species.

When we compared the species richness to the adjacent and well-surveyed Stirling Range and Fitzgerald River National Parks it was obvious we had a gem.

Included in the amazing results were 15 plant species of conservation significance, including a large and healthy population of the rare poison pea Gastrolobium humile and an unnamed she-oak species found across the reserves.

The most common plant family found was the myrtle with 87 species, including 25 melaleuca and 22 eucalypts. The area is also famous for proteaceae and we found an exceptional 47 species including 14 hakea and 13 banksias.

Poison pea (Gastrolobium humile)A large and healthy population of the rare poison pea (Gastrolobium humile) was found on Monjebup in Spring 2014. Photo by Libby Sandiford.

Libby also found that almost 25% of the species identified were at, or beyond, their known range limits.

These properties sit at the junction of two major geological formations (the Yilgarn Block and the Marine Sedimentary Plain) and three biogeographic regions, which means there is a mosaic of soil types that have not been disturbed for millions of years.

Starting from scratch

Our biggest challenge, given this species diversity, has been achieving a similar mix while revegetating cleared areas.

We’ve just completed revegetation work on the first150 hectares of Monjebup North with encouraging results.

Four seed mixes were used, which included seed from 113 species as well as 18,850 seedlings that will eventually result in four different vegetation systems across the 150 hectare area.

Monitoring the success of direct seeding involves crawling on hands and knees counting tiny, newly germinated plants – you need a good eye and a lot of persistence!

Simon Smale (Healthy Landscape Manager) and Jack Mercer (contractor) recently counted plants along transects in the 2014 planting, and we were pleased with a germination rate of 40,000 stems per hectare and most species represented.

Ongoing monitoring of the 2012 restoration is also showing promising results with bird and mammal species slowly returning to take advantage of the productive and vigorous new native vegetation.

Our next steps include mapping the vegetation types on Monjebup and Yarraweyah – not an easy task to say the least! We’ll continue to monitor restored areas of Monjebup North and plan to survey the flora of our recent acquisition, Monjebup Creek, this spring. Can’t wait to see what that will uncover!

Low nutrient soils

The super species diversity of arid shrublands that occur in Western Australia and southern Africa is only equalled by tropical rainforests.

Neither system is particularly easy to live in. In fact, they owe their diversity to critically low levels of soil nutrients. In fertile soils the fastest growing and spreading plants often take over and limit competition.

Generous support for the acquisition of this property was provided by the Australian Government under the Natural Heritage Trust’s National Reserve System Program (Monjebup Reserve) and The Nature Conservancy’s David Thomas Challenge (Monjebup North Reserve).