Spatial heterogeneity in the determinants of woody plant invasion of lowland heath

• Published in: Applied vegetation science Vol. 10; no. 1; pp. 65 - 72
• Main Authors: Manning, Peter, Putwain, Philip D., Webb, Nigel R.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.04.2007; Wiley Subscription Services, Inc
• Subjects: Anon.; Betula; Conservation management; Ecosystem state shift; Heathland; Herbivores; Invasions; Keywords; Kriging; Phosphorus; Safe-site limitation; Seed limitation; Variogram
• ISSN: 1402-2001; 1654-109X
• DOI: 10.1111/j.1654-109X.2007.tb00504.x

Questions: 1. What is the scale and extent of spatial variability in factors affecting Betula invasion of heaths? 2. How much effect does each factor have on within‐patch patterns of invasion? 3. How can this understanding aid in managing Betula invasions? Location: Lowland heath of southern England. Methods: Determinants of Betula (both B. pubescens and B. pendula) invasion: biomass density, necromass density, mean vegetation height, P‐availability, soil water content and total Betula seed bank density, were measured at two sites on a 5‐ha sampling grid. Spatial pattern was assessed using geostatistics. Contributions of each determinant to within‐site heterogeneity in predicted Betula seedling densities were estimated by varying variables over their full and interquartile ranges in a statistical model derived from experimental data. Results: Salient spatial trends were revealed: strong autocorrelation over distances of < 50 m for soil factors and more extensive autocorrelation (0 to > 150 m) in vegetation variables and Betula seed bank densities. The latter resulted in single across‐site gradients, the former small, distinct patches. All patterns were overlain with variance that was present at distances of < 17.6 m. Variables displaying spatial pattern also accounted for within‐site heterogeneity in predicted Betula seedling densities but their relative contribution to this varied between sites. Conclusions: Identifiable spatial autocorrelation in factors controlling patch‐scale invasion patterns allows managers to target invasion prone patches, potentially reducing management intensities. Furthermore, management effort may be optimised by spatially de‐coupling Betula seed from safe‐sites. This plan may adaptable to the management of other weeds and open‐land ecosystems.