Azorella macquariensis leaf trait database

Full description

Azorella macquariensis leaf traits were assessed across Macquarie Island (lat, longs: N - 54.50534, S: -54.76911, E: 158.9263, W, 158.8009). Leaves were collected between 2 January 2017 to 28 February 2017 and fixed in 70% ethanol on site. Leaves were measured at Monash University 1 June 2018 to 29 June 2018.

The endemic, keystone species Azorella macquariensis (Macquarie cushion) has undergone rapid widespread decline across Macquarie Island in 2008/2009, resulting in its listing as critically endangered in 2010. Initial research suggests that Azorella dieback is likely driven by a decadal reduction in plant available water, as a result of a significantly changed regional climate, which may have facilitated a secondary putative pathogenic infection of weakened plants (Bergstrom et al. 2015, Whinam et al. 2014).

Azorella macquariensis Orchard (Apiaceae, Macquarie cushion) leaf samples were taken from 62 sites across Macquarie Island between January and March 2017. Sites (706.86m2, i.e. 15m radius) were randomly stratified using a terrain class model (TCM) to ensure that all potential microclimates that A. macquariensis might be exposed to were surveyed. Methods for the TCM are described in Dickson et al. in prep. Six samples were taken at each site, one from within each of the six 2mx2m plots, which were located on Azorella with representative condition (dieback) variation. Samples (3-5 5cm rosette lengths) were taken from the healthiest cushion in the plot and fixed immediately in 70% ethanol. Department of Primary Industries, Parks, Water and Environment permit number TFL1676. Samples were returned to Monash University and stored at room temperature.

Leaf samples were measured at Monash University in June 2018. One rosette branchlete was used from each sample (barcode) and the new (green) growth of the 2016/2017 season measured, indicated by the colour variation on the sample. For each sample (representing one individual, six per site) the following was measured, new stem growth (green), number of new leaves (green). Four leaves were measured per sample, some only had 3 new leaves, so only 3 would be measured. L1 was closest at the growing tip and L4 furthest from the tip. L1:L4 were flattened between slides and scanned (tif files), for measurements and then the number of spines per leaf were counted under a dissecting microcscope. Green leaf area (mm2), maximum green leaf width (mm), green leaf length (mm) and sheath width (mm) were measured using standard methods in FIJI (Image J 1.52f) from the scanned images.

Data available:
Excel files containing the location and barcode of samples (372) and individual leaf measurements (1488) for each A. macquariensis sample. Headings include:

Site:
Easting and Northing – location of site, UTM, Zone 57S, GDA94, +/-5m
Date_collected
Barcode
Stem_length - This season's new (green) stem growth (mm) - one measurement per barcode
Leaves_new - Number of new leaves in this season - one measurement per barcode
Sample – Spiny/glabrous
Leaf_sample - Leaf sample number (L1, L2, L3, L4) - taken from the new growth stem. Only new season's leaves measured.
Spines – Number of spines per leaf
Leaflets – number of leaflets per leaf
Area_mm^2 – green area, measured in Image J
Length_mm – maximum green leaf length, measured in Image J
Sheath_width_mm – leaf sheath width, measured in Image J
Leaf_width_mm – maximum green leaf width, measured in Image J
Spine_density_sp/mm^2 – number of spines divided by green leaf area

Lineage

Progress Code: completed

Statement: No problems with data collection or data.

Notes

Purpose
This data was collected as part of the PhD thesis of Catherine Dickson. Leaf data, microclimate and Azorella condition will be used to examine the relationship between A. macquariensis leaf traits and condition (dieback).