Scales of heterogeneity in prairie and forest

Kleb, Heather R.; Wilson, Scott D.

doi:10.1139/cjb-77-3-370

Cited by 14 publications

(17 citation statements)

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“…Since plant communities are intrinsically multivariate, an approach using multivariate dissimilarity is more appropriate. Kleb and Wilson (1999), in Canadian prairie and Populus tremuloides forest, fitted a linear relation of the Jaccard similarity of two sites versus the log of their distance apart, and Mistral et al (2000) in New Zealand forest, mire and road‐centre vegetation used a similar plot. This has the theoretical problem that at very large distances the fit would predict a negative similarity, or a dissimilarity >1.0, and moreover the nugget cannot be calculated because the x‐axis never reaches zero.…”

Section: Discussionmentioning

confidence: 99%

Spatial autocorrelation in plant communities: vegetation texture versus species composition

Lawrence‐Lodge¹,

Anderson²,

Groot³

et al. 2007

Ecography

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Vegetation texture, describing plant communities by the range of characters present in them, can describe functional variation more effectively than using the identities of the species. We ask whether spatial trends, as seen in spatial autocorrelation (SAc), are stronger in vegetation texture. We also ask in what environment SAc is stronger, whether local or over longer distances, and with what measure of distance. Roadside vegetation was sampled across an orographic region of the South Island, New Zealand, from a high‐rainfall zone up to just above treeline (the “Wet” side) and then down into a rain‐shadow area (the “Dry” side). Species composition was recorded in quadrats placed in 30 clusters. Five functional plant characters were measured on all species encountered: characters that have been reported in the literature to correlate with light‐capture, heat budget and nutrient strategy. SAc was calculated using a saturation‐response type of relation in species composition, and also in texture using the five functional characters. There was significant species‐composition SAc in almost all comparisons, but the maximum percentage of variation explained was 25%. The fit was almost always higher using local, short‐distance, comparisons than using comparisons over a whole side (Wet or Dry). On average dissimilarity had reached 90% of its asymptote after ca 250 m. It is concluded that the SAc was mainly due to local factors. SAc relations almost always predicted the presence/absence of species more accurately than their abundance. Distances along the road generally gave a very slightly better fit to species composition than surface distances, suggesting that there might be dispersal limitation. On the Wet side, elevation in overall comparisons gave a still better fit, implying environmental control too. The strength of SAc in texture was strongest on the Dry side, and using overall comparisons, abundance weighting and surface distances, but in other cases texture SAc was weaker than SAc in species composition. It is concluded that the saturation‐response formula used here has theoretical advantages over previous approaches. The SAc in this vegetation seems to be caused by a combination of dispersal limitation, broad environmental trends and especially local environmental effects such as disturbance. SAc in texture may have been weaker overall on the Wet side than on the Dry because the main environmental difference across the former is in frost, and characters correlated with frost resistance have not yet been included in texture analyses.

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Section: Discussionmentioning

confidence: 99%

Spatial autocorrelation in plant communities: vegetation texture versus species composition

Lawrence‐Lodge¹,

Anderson²,

Groot³

et al. 2007

Ecography

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“…Other comparisons of the scale of heterogeneity between grasslands and forest have produced few consistent differences, probably because they considered relatively large distances (up to 16 m in , 2.56 m in Kleb and Wilson 1999). In the present study, we attempted to measure scale at plant‐relevant distances, using contiguous 13.5 mm long samples.…”

Section: Discussionmentioning

confidence: 99%

Root Dynamics and Spatial Pattern in Prairie and Forest

Pärtel

Wilson

2002

Ecology

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The invasion of grasslands by woody plants is related to increased heterogeneity in soil resources. At the northern edge of the Great Plains, the amount of heterogeneity in soils reciprocally transplanted between prairie and aspen forest can change within a single growing season, suggesting that heterogeneity is strongly influenced by vegetation. Here we examine several mechanisms by which fine roots could influence soil resource heterogeneity. We measured the total length, spatial pattern, and turnover of fine roots in both prairie and forest using minirhizotrons installed horizontally 10 cm below the soil surface. The total length of fine roots in forest (0.7 cm/cm2) was significantly less than that in prairie (1.4 cm/cm2), which may contribute to more spatially variable resource uptake in forest. The coefficient of variation of root length was significantly higher in forest (92%) than in prairie (65%). Semivariograms showed that the scale of patchiness of root length was significantly greater in forest (8–12 cm) than in prairie (3–4 cm). Lastly, the rate of fine root turnover was significantly higher in forest (49%) than in prairie (20%). Turnover may contribute to spatial variability because a system with high rates of root turnover would appear to have high spatial variability at any given time. Root mortality was also significantly higher in forest than prairie. In summary, many aspects of root distributions and dynamics were consistent with relatively high heterogeneity in forest soil resources. The greater total root length in prairie may account for the significantly higher intensity of root competition in grasslands than forests and contribute to the exclusion of woody plants from prairies. Trees may be able to overcome this resistance by both causing and benefiting from higher levels and scales of soil resource heterogeneity.

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“…Plant species are differentiated in their competitive ability or other measures of performance along gradients of soil moisture (Silvertown et al 1999), microtopography (Zedler and Zedler 1969, Bratton 1976, Beatty 1984), microsite composition (Harper et al 1965, Silvertown 1981, Zamfir 2000), and soil depth (Belcher et al 1992, Reynolds et al 1997) in herbaceous plant communities. Essential resources for plant growth are spatially heterogeneous at scales <1 m (Bell and Lechowicz 1991, Lechowicz and Bell 1991, Jackson and Caldwell 1993, Ryel et al 1996, Kleb and Wilson 1999, Fitter et al 2000), thus co‐occurring individuals may experience functionally different conditions at very small spatial scales. Since small‐scale variability in environmental factors is common and plants are differentiated in their responses to average or typical levels of these environmental factors, it should be a relatively simple matter to examine correlations between environmental heterogeneity and species richness or other indices of coexistence.…”

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confidence: 99%

Relationships between spatial environmental heterogeneity and plant species diversity on a limestone pavement

Lundholm¹,

Larson²

2003

Ecography

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2003. Relationships between spatial environmental heterogeneity and plant species diversity on a limestone pavement. -Ecography 26: 715-722.No empirical studies have examined the relationship between diversity and spatial heterogeneity across unimodal species richness gradients. We determined the relationships between diversity and environmental factors for 144 0.18 m 2 plots in a limestone pavement alvar in southern Ontario, Canada, including within-plot spatial heterogeneity in soil depth, microtopography and microsite composition. Species richness was unimodally related to mean soil depth and relative elevation. Microsite heterogeneity and soil depth heterogeneity were positively correlated with species richness, and the richness peaks of the unimodal gradients correspond to the maximally spatially heterogeneous plots. The best predictive models of species richness and evenness, however, showed that other factors, such as ramet density and flooding, are the major determinants of diversity in this system. The findings that soil depth heterogeneity had effects on diversity when the effects of mean soil depth were factored out, and that unimodal richness peaks were associated with high spatial heterogeneity in environmental factors represent significant contributions to our understanding of how spatial heterogeneity might contribute to diversity maintenance in plant communities.

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Scales of heterogeneity in prairie and forest

Cited by 14 publications

References 0 publications

Spatial autocorrelation in plant communities: vegetation texture versus species composition

Spatial autocorrelation in plant communities: vegetation texture versus species composition

Root Dynamics and Spatial Pattern in Prairie and Forest

Relationships between spatial environmental heterogeneity and plant species diversity on a limestone pavement

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