Practical and theoretical implications of a browsing cascade in Tasmanian forest and woodland

2015 ◽  
Vol 63 (5) ◽  
pp. 435 ◽  
Author(s):  
Alister Hazeldine ◽  
Jamie B. Kirkpatrick
Keyword(s):  
Fire Hazard ◽  
Environmental Data ◽  
Tree Seedlings ◽  
Associational Resistance ◽  
Apparent Contradiction ◽  
Acacia Dealbata ◽  
Eucalypt Forest ◽  
Browsing Damage ◽  
Associational Susceptibility ◽  
Alternative Sources

Browsing cascades have strong implications for biodiversity conservation and fire management. The associational resistance and associational susceptibility hypotheses suggest different mechanisms. We tested the veracity of these two hypotheses by using small dry eucalypt forest and woodland trees. At 67 sites, we measured the height of the browse line and estimated the proportion of foliage remaining below it for all adult individuals of small trees within a 50 × 50 m area, recorded scat numbers, browsing damage to tree seedlings by species and environmental data. The 110–130-cm browse line, and strong relationships between macropod scat numbers and the remaining foliage below the browse line, suggested that Bennetts wallabies (Macropus rufogriseus Shaw) were the main cause of umbrella-shaped trees. The browsers preferred Exocarpos cupressiformis Labill. and Bursaria spinosa Cav. At the other extreme, adult Acacia dealbata Link suffered no browsing damage. All species were browsed as seedlings. Associational resistance occurred in some species and associational susceptibility in others, with the degree of difference in palatability between alternative sources of browse possibly resolving this apparent contradiction. Low browsing pressure is likely to cause woody thickening, an increase in fire hazard and a decrease in biodiversity. Extremely high browsing pressure had no such effects.

Testing the impact of community composition on the productivity of a cool temperate eucalypt forest: the Australian Forest Evenness Experiment (AFEX)

2020 ◽  
Vol 68 (4) ◽  
pp. 310
Author(s):  
Melissa R. Gerwin ◽  
Rose Brinkhoff ◽  
Travis Britton ◽  
Meagan Porter ◽  
Ruth K. Mallett ◽  
...  
Keyword(s):  
Community Composition ◽  
Field Experiments ◽  
Forest Growth ◽  
Plant Community Composition ◽  
Ecological Processes ◽  
Acacia Dealbata ◽  
Carbon Sequestration Potential ◽  
Eucalypt Forest ◽  
Sequestration Potential ◽  
The Impact

Understanding the factors controlling productivity is crucial for modelling current and predicting future forest growth and carbon sequestration potential. Although abiotic conditions exert a strong influence on productivity, it is becoming increasingly evident that plant community composition can dramatically influence ecosystem processes. However, much of our understanding of these processes in forests comes from correlative studies or field experiments in short-statured, short-lived vegetation. Here, we present the background, design and implementation success of the Australian Forest Evenness Experiment (AFEX), which was designed to investigate the influence of community composition on the processes that contribute to forest productivity. Eighty 25 × 25-m plots, covering 5 ha in a logged, burnt forest coupe in south-eastern Tasmania were sown with four tree species, namely Eucalyptus delegatensis R.T.Baker, E. regnans F.Muell., Acacia dealbata Link and Pomaderris apetala Labill., in varying combinations to provide a range of evenness levels with each of the four species as target dominant. Despite some differences between sown composition and realised composition 1year after sowing, a substantial range of community evenness and local neighbourhood densities and compositions existed in the experiment. Thus, this site provides a unique opportunity to determine the influence of local neighbourhood composition on a range of ecological processes.

scholarly journals Ungulate damage on Scots pines in Mediterranean environments: effects of association with shrubs

2001 ◽  
Vol 79 (6) ◽  
pp. 739-746 ◽  
Author(s):  
José M Gómez ◽  
José A Hódar ◽  
Regino Zamora ◽  
Jorge Castro ◽  
Daniel García
Keyword(s):  
Spatial Structure ◽  
Pinus Sylvestris ◽  
Plant Communities ◽  
Scots Pine ◽  
The Other ◽  
High Mountain ◽  
Associational Resistance ◽  
Southeastern Spain ◽  
Associational Susceptibility ◽  
Mechanical Barrier

The spatial structure of plant communities as well as the quality and abundance of neighbours can strongly influence the intensity of herbivory suffered by a plant. In this paper, we study the effect of the association with shrubs on the ungulate herbivory suffered by Scots pine (Pinus sylvestris var. nevadensis Christ., Pinaceae) saplings in two isolated, fragmented populations in southeastern Spain. For this, we monitored herbivory on saplings with regard to the microhabitat in which they grew. We distinguished pines growing in open interspaces, on the edge of shrubs and within the canopy of shrubs, and also we distinguished four functional types of shrubs: thorny shrubs, nonthorny shrubs, thorny scrubs, and nonthorny scrubs. Our results show that association with shrubs increases the damage inflicted on Scots pine saplings. In fact, saplings growing in the open patches, far from the shrubs, escaped from herbivory more frequently and incurred less damage than did saplings growing close to shrubs. However, herbivory was also reduced when pine saplings were completely surrounded by shrubs, since then they served as a mechanical barrier. The type of neighbouring shrub did not affect the overall damage suffered by pines, despite the fact that the ungulates damaged the nonthorny scrubs more intensely than the other kinds of shrubs. Consequently, saplings have an advantage when growing within the canopy of shrubs; these constitute key microsites for pine recruitment in these Mediterranean forests.Key words: associational resistance, associational susceptibility, mammalian herbivory, Mediterranean high mountain, neighbouring effects, Pinus sylvestris var. nevadensis.

scholarly journals Associational resistance and associational susceptibility: specialist herbivores show contrasting responses to tree stand diversification

Oecologia ◽  
2011 ◽  
Vol 169 (2) ◽  
pp. 477-487 ◽  
Author(s):  
Mirco Plath ◽  
Silvia Dorn ◽  
Judith Riedel ◽  
Hector Barrios ◽  
Karsten Mody
Keyword(s):  
Associational Resistance ◽  
Tree Stand ◽  
Specialist Herbivores ◽  
Associational Susceptibility

Potential Use of Quadrivalent Selenium as a Systemic Deer-Browsing Repellent: A Cautionary Note

1994 ◽  
Vol 11 (2) ◽  
pp. 63-64
Author(s):  
Robert Jobidon ◽  
Marcel Prévost
Keyword(s):  
Large Scale ◽  
White Spruce ◽  
Tree Seedlings ◽  
Cautionary Note ◽  
Organoselenium Compounds ◽  
Deer Browsing ◽  
Browsing Damage ◽  
Top Soil ◽  
Internal Transport ◽  
Potential Use

Abstract This study evaluates the potential usefulness and toxicity of applying quadrivalent selenium (selenite ion) to the soil to discourage white-tailed deer from browsing conifer seedlings. After absorption by the root system and internal transport, organoselenium compounds are volatilizedby the foliage, and the characteristic garlic odor is hypothesized to protect coniferous tree seedlings from browsing damage. Results indicate that either 5, 17, or 24 months after treatment, selenized white spruce seedlings did not show significantly different deer-browsing damage from controlseedlings when deer numbers were high. Five and seventeen months after treatment, selenium had not leached but had accumulated in the top soil. Large-scale application of selenium may represent a potential environmental risk, hence we do not recommend use of selenite ion to prevent damagefrom deer-browsing of white spruce seedlings. North. J. Appl. For. 11(2):63-64.

Associational Resistance and Associational Susceptibility: Having Right or Wrong Neighbors

2009 ◽  
Vol 40 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Pedro Barbosa ◽  
Jessica Hines ◽  
Ian Kaplan ◽  
Holly Martinson ◽  
Adrianna Szczepaniec ◽  
...  
Keyword(s):  
Associational Resistance ◽  
Associational Susceptibility

The Eucalypt Forest Grassland/Grassy Woodland Boundary in Central Tasmania

1992 ◽  
Vol 40 (2) ◽  
pp. 123 ◽  
Author(s):  
RJ Fensham ◽  
JB Kirkpatrick
Keyword(s):  
Seedling Establishment ◽  
Suppressive Effect ◽  
Root Competition ◽  
Detectable Effect ◽  
Tree Seedlings ◽  
Herbicide Application ◽  
Eucalypt Forest ◽  
High Elevations ◽  
Planted Tree ◽  
Primary Agent

Downslope boundaries of forest with grassland and grassy woodland occur over a wide altitudinal range in central Tasmania. Three sites were selected for study of the causes of these boundaries at low, medium and high elevations. The open vegetation was generally associated with moister and less rocky soils and more subdued topography than the adjacent forest. Frost incidence and intensity, soil moisture and waterlogging varied markedly among the three open areas. Planted tree seedlings survived 4 years in the open at all sites, and seedlings established in the open both naturally, and after sowing, where grass competition was reduced by herbicide application, digging or root competition from adult eucalypts. Grazing had no detectable effect on seedling establishment. A pot experiment demonstrated a suppressive effect of native grass swards on both seedling establishment and growth, this effect being largely independent of available moisture and nutrients. While frost, waterlogging, fire and drought may play a role in inhibiting eucalypt establishment and increasing eucalypt mortality at some or all of the sites, the dense grass swards found in all the open areas are considered to be the most likely primary agent of tree exclusion.

scholarly journals Importance of the Local Environment on Nutrient Cycling and Litter Decomposition in a Tall Eucalypt Forest

Forests ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 340 ◽  
Author(s):  
Jessie C. Buettel ◽  
Elise M. Ringwaldt ◽  
Mark J. Hovenden ◽  
Barry W. Brook
Keyword(s):  
Nitrogen Availability ◽  
Average Distance ◽  
Nitrogen Concentration ◽  
Basal Area ◽  
Field Measurements ◽  
Local Environment ◽  
Forest Litter ◽  
Nitrogen Fixing ◽  
Acacia Dealbata ◽  
Eucalypt Forest

The relative abundance of nitrogen-fixing species has been hypothesised to influence tree biomass, decomposition, and nitrogen availability in eucalypt forests. This prediction has been demonstrated in experimental settings (two-species mixtures) but is yet to be observed in the field with more realistically complex communities. We used a combination of (a) field measurements of tree-community composition, (b) sampling of soil from a subset of these sites (i.e., the local environment), and (c) a decomposition experiment of forest litter to examine whether there is a local-scale effect of the nitrogen-fixing Acacia dealbata Link (presence and abundance) on nitrogen availability, and whether increases in this essential nutrient led to greater biomass of the canopy tree species, Eucalyptus obliqua L’Hér. Average A. dealbata tree size was a significant predictor of forest basal area in 24 plots (12% deviance explained) and, when combined with average distance between trees, explained 29.1% variance in E. obliqua biomass. However, static patterns of local nitrogen concentration were unrelated to the presence or size of A. dealbata, despite our experiments showing that A. dealbata leaf litter controls decomposition rates in the soil (due to three times higher N). Such results are important for forest management in the context of understanding the timing and turnover of shorter-lived species like acacias, where higher N (through either litter or soil) might be better detected early in community establishment (when growth is faster and intraspecific competition more intense) but with that early signal subsequently dissipated.

scholarly journals Passive adsorption of neighbouring plant volatiles linked to associational susceptibility in a subarctic ecosystem

2016 ◽  
Author(s):  
Adedayo Mofikoya ◽  
Kazumi Miura ◽  
Toini Holopainen ◽  
Jarmo K. Holopainen
Keyword(s):  
Plant Volatiles ◽  
Field Experiments ◽  
Mountain Birch ◽  
Forest Site ◽  
Natural Ecosystem ◽  
Associational Resistance ◽  
Plant Volatile ◽  
Passive Adsorption ◽  
Associational Susceptibility ◽  
Neighbouring Plant

Abstract. Neighbouring plants may affect volatile compound emissions of a focal plant and confer associational resistance or susceptibility. Associational resistance has been reported as a result of adsorption of neighbouring plant volatile and semivolatile compounds on focal plant foliage in field experiments. However, these associational effects in a natural ecosystem remain largely unknown. The effects of the presence and density of Rhododendron tomentosum (Rt) understorey on the volatile profile and herbivore density of mountain birch, Betula pubescens ssp. czerepanovii (MB) was investigated in a subarctic forest site. The monoterpene β-myrcene, sesquiterpene aromadendrene and sesquiterpene alcohols, palustrol and ledol were recovered from the foliage of MB trees that had Rt growing in the understorey. The number of Rt shoots growing directly under the MB trees correlated positively with the rate of recovery of adhered compounds and negatively with total MB emissions. Palustrol and β-myrcene recovery from MB leaves showed the highest positive correlation with Rt density. Recovery of adhered compounds was higher at lower sampling temperatures. Herbivory was at very low levels both in control and Rt plots. The proportion of foliage infected by a gall mites (Acalitus spp.) was positively correlated with the recovery of the adhered ledol and palustrol from MB foliage. These results indicate that understorey plant volatiles, both sesquiterpene and highly volatile monoterpenes, may adhere onto and be subsequently re-released from MB foliage at low temperatures during the subarctic growing season. The Rt density also plays an important role in the adherence and re-release rates of neighboring plant volatiles and may induce a response in MB volatile emission. Presence of Rt volatiles on MB foliage may make them more susceptible to gall mite infestation suggesting that high Rt density in the subarctic ecosystem may confer associational susceptibility to herbivores on MB.

Evaluation of some factors involved in reducing browsing damage to eucalypt trees by sheep

1994 ◽  
Vol 34 (5) ◽  
pp. 601 ◽  
Author(s):  
PJ Haines ◽  
AB Bell ◽  
LP Thatcher
Keyword(s):  
Eucalyptus Camaldulensis ◽  
Agroforestry Systems ◽  
Tree Seedlings ◽  
Sheep Grazing ◽  
Short Term ◽  
Management Options ◽  
Factors Affecting ◽  
Browsing Damage ◽  
One Year ◽  
Stocking Rates

These experiments evaluated in northeastern Victoria the factors affecting the severity of browsing damage to eucalypts by sheep. We aimed to develop management options for integrating sheep grazing in agroforestry systems. One-year-old tree seedlings were planted into annual pasture and grazed at high stocking rates (44 sheep/ha) for up to 1 week when the pasture was abundant. In experiments 1 and 2, crossbred weaners almost totally defoliated Eucalyptus camaldulensis (river red gum) seedlings after 96 h grazing; damage from older Merino wethers was minimal. Of the 4 eucalypt species tested for relative acceptability or palatability to crossbred weaners, E. camaldulensis was the most heavily browsed and E. globulus spp. bicostata (southern blue gum), least. The height of the pasture immediately surrounding the seedlings, and therefore visibility of the seedling to the sheep, did not affect browsing extent. In experiment 3, potential repellents were applied either on the ground around E. camaldulensis seedlings or sprinkled on the foliage. Six repellants provided short-term protection from crossbred weaner sheep; Replex 1 and 3, and egg and paint were the most effective. After 4 days grazing, seedlings treated with Replex 3 had sustained 24% mean browsing damage compared with 90% for the control.

Sign in / Sign up

Export Citation Format

Share Document