Action: Cut trees and apply herbicide
- One controlled study in the UK found that cutting trees and applying herbicide increased the abundance of heather seedlings. However, one replicated, controlled study in the UK found that cutting silver birch trees and applying herbicide did not alter cover of common heather when compared to cutting alone.
- Two controlled studies (one of which was a before-and-after study) in South Africa found that cutting of trees and applying herbicide did not increase shrub cover.
- Two controlled studies in South Africa found that cutting trees and applying herbicide increased the total number of plant species and plant diversity.
- One replicated, controlled study in the UK found that cutting and applying herbicide reduced cover of silver birch trees.
Some tree species can survive cutting by resprouting. Cutting combined with application of herbicide aims to kill trees that might otherwise resprout after cutting.
Supporting evidence from individual studies
A controlled study in 1979–1981 in a heathland in Cambridgeshire, UK (Marrs 1984) found that cutting birch Betula pendula saplings and spraying with herbicide sometimes increased the abundance of heather Calluna vulgaris seedlings. After two years and in one of three cases, there were more heather seedlings in areas where silver birch saplings had been cut and sprayed with herbicide (64 seedlings/m2) than in plots where silver birch saplings had not been cut or sprayed (4 seedlings/m2). Areas where trees had been cut and herbicide had been applied had fewer silver birch saplings (2-4 saplings/m2) than those where herbicide had not been used (20 saplings/m2). However, the opposite was true in two of three cases for silver birch seedlings (cut and herbicide: 24-54 seedlings/m2; uncut and no herbicide: 7 seedlings/m2). The herbicides fosamine ammonium, 2,4,5-T, and triclopyr were each applied in four 4 m2 plots in 1979 followed by cutting in 1980, and in four plots no herbicide or cutting was applied. Additionally, each herbicide was applied in four 4 m2 plots in 1980 following cutting in 1979, and in another four plots no herbicide or cutting was applied. Abundance of silver birch and heather plants was estimated annually in 1980-1981 in all plots.
A replicated, controlled, before-and-after, paired study in 1980–1985 in a heathland in the UK (Marrs 1987) found that cutting silver birch trees Betula pendula and applying herbicide reduced their abundance when compared to cutting alone, and increased cover of wavy-hair grass Deschampsia flexuosa, but did not alter cover of common heather Calluna vulgaris. In four of four years, areas where silver birch had been cut and herbicide applied had lower number of silver birch (0–3 trees/200 m2) than areas where cutting alone was used (7–10 trees/200 m2). Cutting silver birch trees and applying herbicide did not alter cover of common heather relative to cutting alone (no data presented). After five years cover of wavy-hair grass was higher in plots where silver birch was cut and herbicide used (26–37%) than in plots where cutting along was carried out (8%). In January 1980 sixteen 10 x 20 m plots were established. All silver birch trees in the plots were cut at a height of 10 cm and removed from the site. Following this, in four plots all stumps were painted with the herbicide 2,4,5-T, in four plots the herbicide fosamine was sprayed, in four plots both fosamine and 2,4,5-T were used, and in four plots no herbicide was applied. In July 1980, 1981, 1982, and 1985 the number of silver birch trees in plots were counted. Vegetation cover was estimated in plots by eye.
A replicated, controlled study in 2008–2014 in two fynbos sites in Eastern Cape, South Africa (Kerr & Ruwanza 2016) found that cutting and applying herbicide to invasive rose gum Eucalyptus grandis trees increased the total number of plant species, did not alter the number of shrub or tree species and increased the number of grass species. The number of plant species was higher in areas that were cut and treated with herbicide (10 species) than in areas that were not (4 species), and the number of plant species was not significantly different from uninvaded fynbos (12 species). The number of tree and shrub species in areas that were cut and treated with herbicide was not significantly different from that in areas which were not cut or treated with herbicide or uninvaded fynbos (cut and herbicide: 4 species, not cut with no herbicide: 3 species, uninvaded fynbos: 7 species). However, the number of grass species in areas that were cut and treated with herbicide (2 species) was higher than in areas that were not cut or treated with herbicide (0 species) or uninvaded fynbos (1 species). In 2008 rose gum trees were cut and herbicide applied in part of two fynbos areas. In 2014 three 100 m2 plots were placed in each of the areas where trees had been cut and herbicide applied, areas where trees had not been cut, and uninvaded fynbos at each site. Vegetation cover and number of species were estimated in each plot. Herbicide name and concentration is not given.
A controlled, before-and-after trial between 2013 and 2014 in a fynbos site in Cape Town, South Africa (Krupek et al. 2016) found that cutting of invasive orange wattle Acacia saligna trees, followed by herbicide treatment, increased plant diversity, but not shrub cover. Plant species diversity was higher in areas that had been cut and had herbicide applied than areas where no cutting or herbicide application had been carried out (data as model results). However, shrub cover in areas that had been cut and had herbicide applied (4%) was not significantly different from areas that had not been cut or had herbicide applied (5%). In April 2013 in ten 25 m2 plots the orange wattle saplings were cut and herbicide (active ingredients Triclopyr 120 g/l and Aminopyralid 12 g/l) was applied to their cut stems, while another ten plots were left uncut. The cover of plant species was assessed using 1 m2 quadrats placed inside each plot.
- Marrs R.H. (1984) Birch control on lowland heaths: mechanical control and the application of selective herbicides by foliar spray. Journal of Applied Ecology, 21, 703-716
- Marrs R.H. (1987) Studies on the conservation of lowland Calluna heaths. I. Control of birch and bracken and its effect on heath vegetation. Journal of Applied Ecology, 24, 163-175
- Kerr T.F. & Ruwanza S. (2016) Does Eucalyptus grandis invasion and removal affect soils and vegetation in the Eastern Cape Province, South Africa? Austral Ecology, 41, 328-338
- Krupek A, Gaertner M., Holmes P.M. & Elser K.J. (2016) Assessment of post-burn removal methods for Acacia saligna in Cape Flats Sand Fynbos, with consideration of indigenous plant recovery. South African Journal of Botany, 105, 211-217