Highlights of the 2021-2022 MIREN survey in Kosciuszko National Park, Australia

In the summer of 2021-2022, RCAAE members Keith McDougall and Neville Walsh led the fourth survey of roadside weeds in Kosciuszko as part of the global MIREN-initiative. In Victoria, a similar resurvey of roadsides was undertaken by RCAAE members John Morgan, James Shannon, Zac Walker and Alex Blackburn-Smith.

The following text written by Keith McDougall discusses the highlights from the Kosciuszko surveys. More information on the MIREN surveys can be found at https://www.mountaininvasions.org/

Genevieve Wright, Neville Walsh and I set out in early December to commence the resurvey of MIREN road transects. This was the fourth survey of the permanently marked plots, the first being in 2006 – 07, four years after the largest wildfire in living memory in the park. The potential perils of the survey were many – for instance, the park is home to four of the 10 deadliest snakes in the world. However, apart from the effects of increasing age in the steep terrain (the mean age of the surveyors was 61), our biggest fear was anaphylaxis, for Neville from a genus of native daisies called Cassinia and for me from the ferocious Jack Jumper Ant, which in the four surveys has stung me twice, both at site AT7. We survived.

You would think that after three surveys of the same transects over 10 years, there would be nothing left to discover in subsequent surveys, but that was not the case, and our discoveries again highlight the value of this sort of work. Kosciuszko National Park was certainly different this time and so botanical surprises were not entirely unexpected. Firstly, a decade long drought had broken in February 2020. Plants that had gone to ground (as seed) during the dry years may have had an opportunity to flourish, as might species that like disturbance from fire. A wildfire since our last survey, mostly on New Year’s Day 2020, may not have burnt as much of the park as the one in January 2003 but it burnt with a speed and ferocity never seen before. Some direct effects of the fire were immediately evident. Part of one road plot had been submerged in a landslide (the result of a subsequent deluge of rain on the fire scarred soils) and part of one plot in natural vegetation had been washed away, leaving a ditch half a metre deep.

The dead stems of 2 m tall Conyza sumatrensis (an annual non-native daisy) were a feature of many burnt natural vegetation plots – it was rarely recorded in previous surveys but its seeds were clearly present and ready to take advantage of disturbance. We recorded Trachymene composita in our plots for the first time. It is a curious biannual native herb, which appears after fire and can grow to 2.5 m tall. After a couple of years, it disappears again until the next fire, which may not be for many decades. We were especially concerned for the MIREN mascot plant, Poa mireniana, a species discovered in the 2011 – 12 survey. All of its populations were burnt and it had grown in areas with the most severe fire. However, it was great to see that it had recovered well and increased in cover.

New discoveries were also made on transects that were not burnt in 2020. Two highly invasive non-native grasses, Nassella trichotoma and Eragrostis curvula were recorded in road plots of Kosciuszko Road for the first time. The single plant of Nassella was removed and park staff will try to remove the Eragrostis, which was sadly too abundant for us to tackle. Both of those species were already known in the park (from lower elevations) but we also recorded two non-native species that had not been recorded in or near the park before: Plantago coronopus and Xanthium spinosum. The populations we found appear to be the highest recorded in Australia (with the Plantago usually found near the coast). We pulled out all of the Xanthium plants (carefully – it is a vicious species). It was an excellent example of how non-native plants can jump to a mountain site rather than move slowly along the road. The roadside verge where it was growing had recently been reshaped with imported gravel, clearly from a lowland area containing Xanthium seed.

Juvenile Xanthium spinosum plant growing in imported gravel on a road verge in Kosciuszko National Park

Our most important find was in an unburnt native vegetation plot, where we located a small population of the critically endangered orchid, Pterostylis oreophila. This was the first new record in almost 20 years and brings the number of extant populations in New South Wales to three.

A flower of the critically endangered orchid Pterostylis oreophila