Plant species numbers predicted by a topography-based groundwater flow index

• Published in: Ecosystems (New York) 2005-06, Vol.8 (4), p.430-441
• Main Authors: Zinko, U, Seibert, J, Dynesius, M, Nilsson, C
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Boreal forests; community structure; correlation; environmental factors; Forest soils; Fundamental and applied biological sciences. Psychology; General aspects; Groundwater; Groundwater level; Landscapes; Moisture content; plant communities; Plants; slope; Soil water; Species; species diversity; Synecology; Topographic Wetness Index; Vascular plants; water flow
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-003-0125-0

The lack of a clear understanding of the factors governing the often-great variation of species numbers over entire landscapes confounds attempts to manage biodiversity. We hypothesized that in a topographically variable boreal forest landscape the availability of shallow groundwater is a major determinant of plant species numbers. We then developed a topographically derived hydrologic index based on multidirectional flow algorithms to account for the variation in availability of such groundwater in the landscape. We found a positive correlation between species numbers of vascular plants in plots ranging from 0.01 to 200${\rm m}^{2}$and the hydrologic index. Generally, the landscape was relatively dry and species-poor, but interspersed patches with shallow groundwater had high species numbers and high proportions of regionally uncommon plant species. The index explained 30% of the variation in vascular plant number and correlated quite well$(r_{{\rm s}}=0.50)$with groundwater level, but not as well with a community${\rm H}^{+}$concentration value (instead of community pH,$r_{{\rm s}}=-0.31$), based on species composition. In addition, we found a very strong correlation between species number and the community${\rm H}^{+}$concentration value$(r_{{\rm s}}-0.84)$. The hydrologic index is a useful tool for the identification of spatial of species number patterns across entire landscapes. This is an important step in identifying the areas most in need of protection or restoration, designing survey techniques, and understanding the fundamental processes that control the spatial distribution of species.