Predicting plant species diversity in response to disturbance magnitude in grassland remnants of central Alberta

2002 ◽  
Vol 80 (5) ◽  
pp. 504-511 ◽  
Author(s):  
K Vujnovic ◽  
R W Wein ◽  
M R.T Dale
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Exotic Species ◽  
Plant Species ◽  
Intermediate Disturbance Hypothesis ◽  
Plant Species Diversity ◽  
Small Scale ◽  
Intermediate Disturbance ◽  
Total Species Richness ◽  
Disturbance Hypothesis

The Intermediate Disturbance Hypothesis states that the greatest species diversity occurs at intermediate levels of disturbance because species coexistence is maintained at a nonequilibrium state and no strong competitor can dominate completely. On the other hand, diversity of exotic species is expected to increase with the disturbance magnitude. These patterns were tested for in this study. The cover of all vascular plants, mosses, and lichens in 1 × 1 m plots across a range of disturbance levels was sampled in 11 remnant grasslands within the Aspen Parkland Ecoregion of central Alberta, western Canada. The Intermediate Disturbance Hypothesis was supported for small-scale within-patch diversity for total species richness and Simpson's diversity index. Lower species diversity was found in undisturbed and lightly grazed as well as in highly disturbed plots. Intermediate levels of disturbance had reduced dominance of Festuca hallii (Vasey) Piper and increased abundance of most other species; this gave the highest species diversity. The species richness and diversity of exotic plant species showed a significant positive relationship with the magnitude of the disturbance. Understanding relationships between disturbance and plant species diversity, especially exotic plants, can influence management decisions on what disturbance regime is conducive to maintaining natural plant communities.Key words: Intermediate Disturbance Hypothesis, diversity, exotic species, grassland.

SGS Biodiversity Theme: impact of plant biodiversity on the productivity and stability of grazing systems across southern Australia

2003 ◽  
Vol 43 (8) ◽  
pp. 961 ◽  
Author(s):  
D. R. Kemp ◽  
W. McG. King ◽  
A. R. Gilmour ◽  
G. M. Lodge ◽  
S. R. Murphy ◽  
...  
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Plant Species ◽  
Native Species ◽  
Management Practices ◽  
Plant Species Diversity ◽  
Native Plant ◽  
Total Species Richness ◽  
Grazing Systems ◽  
Sustainable Grazing

The relationships between productivity and plant species diversity were assessed using data from the Sustainable Grazing Systems (SGS) 10 national experiment sites. Each site applied up to 7 different management treatments. Sites varied in the amount of data available for analysis. Plant species diversity was assessed in terms of both the total and native species present at each site. More than 200 plant taxa were recorded over the period of the experiment, about one-third of which were native. In the majority of cases, the native species present within a treatment remained there throughout the experiments, even when fertilised and oversown with introduced species. The number of native species increased by 1 or 2 over the 3–4 years of each experiment where grasslands were less intensively used (average herbage mass >2 t DM/ha), but decreased in more heavily grazed treatments. Native grasses made much greater contributions to herbage mass than other native species. Of the more than 70 native plant species found, the most numerous were broadleaf species, which tended to be more variable under management treatments. As total species richness increased, there was a tendency for pasture productivity to be less, for the mean standing herbage mass to be less and for seasonal growth to be less stable. This depended upon experiments and tended to apply at the sites with higher annual pasture growth rates. All treatments had >10 plant species within the small (about 1.5 ha) paddocks used and larger paddocks often had many more. It was apparent from the high plant species richness at each site (about 25–100 species) that many more niches exist in these paddocks than the number of species usually sown in a pasture. Opportunities to redesign pasture mixtures to exploit more of the resources available obviously exist. Understanding of the relationships among management practices, productivity and plant species diversity is limited, but will become important as we seek more sustainable grazing systems. The studies analysed here suggested that where the herbage mass was maintained between 2 and 4 t DM/ha then species were maintained and productivity was optimised.

scholarly journals Diversity–disturbance relationships: frequency and intensity interact

2012 ◽  
Vol 8 (5) ◽  
pp. 768-771 ◽  
Author(s):  
Alex R. Hall ◽  
Adam D. Miller ◽  
Helen C. Leggett ◽  
Stephen H. Roxburgh ◽  
Angus Buckling ◽  
...  
Keyword(s):  
Species Diversity ◽  
Empirical Evidence ◽  
Empirical Studies ◽  
Ecological Theory ◽  
Intermediate Disturbance Hypothesis ◽  
Intermediate Disturbance ◽  
Disturbance Frequency ◽  
Theoretical Predictions ◽  
Experimental Populations ◽  
Disturbance Hypothesis

An influential ecological theory, the intermediate disturbance hypothesis (IDH), predicts that intermediate levels of disturbance will maximize species diversity. Empirical studies, however, have described a wide variety of diversity–disturbance relationships (DDRs). Using experimental populations of microbes, we show that the form of the DDR depends on an interaction between disturbance frequency and intensity. We find that diversity shows a monotonically increasing, unimodal or flat relationship with disturbance, depending on the values of the disturbance aspects considered. These results confirm recent theoretical predictions, and potentially reconcile the conflicting body of empirical evidence on DDRs.

Modelling wave-induced disturbance in highly biodiverse marine macroalgal communities: support for the intermediate disturbance hypothesis

2008 ◽  
Vol 59 (6) ◽  
pp. 515 ◽  
Author(s):  
Phillip R. England ◽  
Julia Phillips ◽  
Jason R. Waring ◽  
Graham Symonds ◽  
Russell Babcock
Keyword(s):  
Species Diversity ◽  
Wave Model ◽  
Intermediate Disturbance Hypothesis ◽  
Curvilinear Relationship ◽  
Total System ◽  
Physical Disturbance ◽  
Stochastic Disturbance ◽  
Intermediate Disturbance ◽  
Wave Induced ◽  
Disturbance Hypothesis

As biodiversity declines globally, it is becoming increasingly important to understand the processes that create and maintain biodiverse communities. We examined whether the extraordinarily high species diversity of macroalgal communities in shallow coastal waters off south-west Western Australia is related to wave-induced physical disturbance. We used the numerical wave model SWAN to estimate the hydrodynamic forces generated by waves in bathymetrically complex coastal reefs. Oscillatory water motion at the seabed during extreme wave events was used as an index of physical disturbance in macroalgal communities. There was a significant curvilinear relationship between species diversity and disturbance index, consistent with the intermediate disturbance hypothesis (IDH). Diversity was lower at exposed offshore sites where disturbance is likely to be highest and at very sheltered sites with the least disturbance. Our results match those from some other highly diverse habitats, including rainforests, grasslands and coral reefs in which patchy, stochastic disturbance regimes have been hypothesised to prevent the development of homogeneous climax communities, promoting spatiotemporal heterogeneity and increasing total system diversity. Our results represent important evidence in support of a role for the IDH in driving diversity in marine plant communities.

scholarly journals A six-year grazing exclusion changed plant species diversity of a Stipa breviflora desert steppe community, northern China

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4359 ◽  
Author(s):  
Xing Wang ◽  
Xinguo Yang ◽  
Lei Wang ◽  
Lin Chen ◽  
Naiping Song ◽  
...  
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Environmental Factors ◽  
Plant Species ◽  
Northern China ◽  
Plant Species Diversity ◽  
Desert Steppe ◽  
Diversity Patterns ◽  
Shannon Diversity ◽  
Steppe Community

Excluding grazers is one of most efficient ways to restore degraded grasslands in desert-steppe communities, but may negatively affect the recovery of plant species diversity. However, diversity differences between grazed and fenced grasslands in desert-steppe are poorly known. In a Stipa breviflora desert steppe community in Northern China, we established six plots to examine spatial patterns of plant species diversity under grazed and fenced conditions, respectively. We addressed three aspects of species diversity: (1) The logistic, exponential and power models were used to describe the species-area curve (SAR). Species richness, abundance and Shannon diversity values change differently with increasing sampling areas inside and outside of the fence. The best fitted model for SAR was the logistic model. Excluding grazers had a significant impact on the shape of SAR. (2) Variograms was applied to examine the spatial characteristics of plant species diversity. We found strong spatial autocorrelations in the diversity variables both inside and outside the fence. After grazing exclusion, the spatial heterogeneity decreased in species richness, increased in abundance and did not change in Shannon diversity. (3) We used variance partitioning to determine the relative contributions of spatial and environmental factors to plant species diversity patterns. Environmental factors explained the largest proportion of variation in species diversity, while spatial factors contributed little. Our results suggest that grazing enclosures decreased species diversity patterns and the spatial pattern of the S. breviflora desert steppe community was predictable.

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