How resilient is Calluna vulgaris to drought during germination and its seedling stage?

The coastal heathlands of North-west Europe are valuable cultural landscapes, created and maintained over millennia by a land-use regime involving burning and grazing. These heathlands are now critically threatened throughout their range by land-use change and, increasingly, climatic changes. The climatic change impacts are complex, as the coastal heathland regions are experiencing increased temperature and precipitation, but also increased frequency and severity of extreme events, such as drought. Previous studies reveal that established heathland vegetation, including Calluna, are vulnerable to drought, but also that these vulnerabilities vary throughout the range, and with successional stage after fire. Recruitment from seed is an important regeneration strategy for Calluna heathland vegetation after burning, and our study is the first to assess how the seed germination and early seedling growth of Calluna respond to drought. We will do this in a lab germination experiment, where we will expose Calluna seeds to five different drought treatments, from -0.25 MPa to -1.7 MPa, and measure germination, and record germination percentage, germination rates, and seedling growth, below-ground allocation, and functional traits (Specific Leaf Area, Specific Root Length). To allow assessment of variation in drought responses due to geographic origin, successional stage, and the maternal plants’ drought exposure, we will conduct this experiment on seeds from 540 Calluna plants sampled from across three drought treatments (control, 50%, and 90% coverage), in three successional stages after fire (pioneer, building, mature), in two regions (60N, 65N), using a factorial design.

Using Dartmoor ponies in conservation grazing to reduce Molinia caerulea dominance and encourage germination of Calluna vulgaris in heathland vegetation on Dartmoor, UK

The increasing dominance of purple moor-grass Molinia caerulea in heathland ecosystems in the UK is of growing concern due to its detrimental impact on plant and animal diversity on sites of nature conservation interest. The use of free-ranging ponies to reduce Molinia dominance was investigated from 2017 to 2019 within a 425 ha site on Dartmoor, UK. Salt blocks were used to attract the ponies to a Molinia-dominated area of heath within the site, away from their previously-preferred grazing areas. The impact of pony grazing was assessed by measurements of vegetation structure and plant species composition. The increased presence of ponies in the vicinity of the salt blocks increased the percentage occurrence of bare ground, reduced sward surface height, reduced percentage occurrence of Molina and increased the germination of heather Calluna vulgaris seedlings. The conclusions of this research are that salt blocks can be used to attract ponies to graze targeted areas of Molinia-dominated heathland. Through their grazing and trampling, ponies can reduce the dominance of Molinia, leading to an increase in the germination and establishment of heather seedlings.

Contemporary Fire Regimes of the Arid Carnarvon Basin Region of Western Australia

This study investigates the fire regime for the arid Carnarvon Basin region of Western Australia using remotely sensed imagery. A fire history database was constructed from satellite images to characterise the general fire regime and determine any effect of vegetation types and pre-fire weather and climate. The study area was divided into two sections (northern and southern) due to their inherently different vegetation and climate. A total of 23.8% (15,646 km2) of the study area was burnt during the 39-year study period. Heathland vegetation (54%) burnt the most extensively in the southern study area, and hummock grasslands (68%) in the northern. A single, unusually large fire in 2012 followed exceptional rains in the previous 12 months and accounted for 55% of the total burnt area. This fire burnt mainly through Acacia shrublands and woodlands rather than hummock grasslands, as normally experienced in the northern study area. Antecedent rainfall and fire weather were found to be the main meteorological factors driving fire size. Both study areas showed a moderate to strong correlation between fire size and increased pre-fire rainfall in the year preceding the fire. Predicted future changes in climate may lead to more frequent and higher intensity fires.

Forage intake, digestibility and performance of cattle, horses, sheep and goats grazing together on an improved heathland

A mixed herd of five cows, five mares, 32 ewes and 32 goats was managed with their offspring during two consecutive years in a paddock (22.3 ha) with 76% of heathlands and 24% of improved pasture area, with the aim of studying their differences in ingestive behaviour and performance. Diet composition, dry matter intake (DMI) and digestibility (DMD) were estimated on three occasions using the alkane technique, and all animals were periodically weighed to calculate bodyweight (BW) changes per livestock unit (LU). Goats selected higher proportions of shrubs than the other herbivore species (P < 0.001). Overall, daily DMI was higher (P < 0.001) in equines (218 g/kg BW0.75) than in ruminants (174, 121 and 80 g/kg BW0.75 for cattle, goats and sheep, respectively), whereas DMD was lower (P < 0.001) in equines (569 g/kg DM) compared with ruminants (733–791 g/kg DM). During the first half of the grazing season (from late April to mid-July), dams’ BW changes per LU did not differ between species. However, during late summer–autumn lower (P < 0.001) BW losses per LU were observed in sheep and goats (–89 g/day) than in cattle (–534 g/day), being intermediate in horses (–254 g/day). For the overall grazing season, ewes and goats showed greater (P = 0.056) BW gains per LU (338 g/day) than cows and mares (178 g/day). Regarding the offspring, BW gains per LU were greater (P < 0.001) in lambs (3612 g/day) than in other species. Calves presented greater gains than kids (2647 vs 1909 g/day.LU), whereas foals showed intermediate gains (2385 g/day.LU). Therefore, under these conditions of partially improved heathlands, sheep was the most productive species. However, looking at the diet selection and digestibility, goats could complement sheep or cattle herds by achieving a more efficient utilisation of heathland vegetation, and increasing overall productivity per hectare. By contrast, horses, having high levels of grass intake, compete with cattle and sheep for pasture utilisation.

Combination of long-chain alcohols and fatty acids with alkanes as faecal markers to estimate feed intake and digestibility in horses and cattle fed on grass-heathland vegetation communities

Application of long-chain alcohols (LCOH) and long-chain fatty acids (LCFA) combined with alkanes as faecal markers to estimate dry matter intake (DMI) and dry matter digestibility (DMD) of equines and cattle was assessed. Six crossbred mares, randomly divided in two groups (H1 and H2), and three nonlactating cows (C) were housed in individual stalls. Groups H1 and C were fed on a diet of ryegrass (Lolium perenne, 0.7) and heather (Erica spp., Calluna vulgaris, 0.3), and H2 received ryegrass (0.4), heather (0.3) and gorse (Ulex gallii, 0.3). Digestibility was estimated using LCOH (C28-OH and C30-OH) and LCFA (C28-FA, C30-FA, and C32-FA) as internal markers. For DMI estimation, animals received daily a paper pellet containing C24, C32, and C36n-alkanes. Intake was estimated from the faecal ratio of naturally occurring LCOH, LCFA, and dosed n-alkanes, and was compared with the known DMI values. In horses, all markers provided accurate estimates of DMD. Similarly, LCOH provided accurate estimates of DMD in cattle, whereas LCFA underestimated it (P < 0.05). Intake estimates were affected (P < 0.05) by the marker pair used in calculations. In general, the C24:C24-FA pair provided the most accurate DMI estimates. Results suggest the usefulness of combining epicuticular compounds as faecal markers to estimate DMI, DMD and diet composition of horses and cattle grazing grass-heathland communities, simultaneously.