Abstract. The form of the relationship between local species richness and the number of species in the surrounding region can be used as a test between competing theories of community structure. For 32 canopy gaps in New Zealand Nothofagzts forest, we examined the relationship between the number of vascular plant species in 0.2-m2 quadrats within the gap and the species richness of the whole gap. We found no evidence that competition for a limited number of niches placed an upper limit on the number of locally CO-occurring species. Rather, the mean number of species in quadrats within canopy gaps increased in direct proportion to gap species richness. This relationship held after we controlled for potentially confounding factors, including variation in forest floor substrate, and gap size, age, shape and orientation. Our results suggest that even over relatively small spatial scales, local species richness can be constrained by the size of the species pool in the immediately surrounding region.
Question: Does canopy tree regeneration response to different large disturbances vary with soil drainage? Location: Old-growth conifer (Dacrydium and Dacrycarpus), angiosperm (Nothofagus and Weinmannia) rain forest, Mount Harata, South Island, New Zealand. Methods: Trees were aged (1056 cores) to reconstruct stand history in 20 (0.12 -0.2 ha) plots with different underlying drainage. Spatial analyses of an additional 805 tree ages collected from two (0.3 -0.7 ha) plots were conducted to detect patchiness for five canopy tree species. Microsite preferences for trees and saplings were determined. Results: There were clear differences in species regeneration patterns on soils with different drainage. Conifer recruitment occurred infrequently in even-aged patches (> 1000 m 2 ) and only on poorly drained soils. Periodic Nothofagus fusca and N. menziesii recruitment occurred more frequently in different sized canopy openings on all soils. Weinmannia recruitment was more continuous on all soils reflecting their greater relative shade-tolerance. Distinct periods of recruitment that occurred in the last 400 years matched known large disturbances in the region. These events affected species differently as soil drainage varied. Following earthquakes, both conifers and N. menziesii regenerated on poorly drained soils, while Nothofagus species and Weinmannia regenerated on well-drained soils. However, Dacrydium failed to regenerate after patchy storm damage in the wetter forest interior; instead faster-growing N. fusca captured elevated microsites caused by uprooting. Conclusions: Underlying drainage influenced species composition, while variation in the impacts of large disturbance regulated relative species abundances on different soils.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.