Climate, landscape and microenvironment interact to determine plant composition in naturally discrete gravel beach communities

Abstract

Question: What is the relative importance of national‐, regional‐ and within‐beach‐scale influences on vegetation composition and floristic affinities of New Zealand gravel beaches? Location: Coastal New Zealand. Methods: We sampled vegetation composition at 61 gravel beaches, quantifying site factors and adjacent landscape characteristics. Site, climate and geographic relationships between gravel beaches and related ecosystems were inferred using GIS data layers. To simultaneously investigate influences at different spatial scales, we used ordination and variation partitioning to examine relationships between composition and environment, and hierarchical models to understand floristic affinities with related ecosystems. Results: At a national scale, compositional variation among beaches reflects mean annual temperature and spring vapour pressure deficit; within regions, proximity of native woody vegetation and coastal turfs are important; within‐beach variation is related to substrate stability and particle size distribution. The gravel beach flora is 50% exotic, reflecting the highly modified nearby landscapes; 30% of species are characteristic of coastal sands, 20% of braided riverbeds and 8% of coastal turfs. Affinities with coastal sand communities are unrelated to microsite sandiness or area of sand dunes within 50 km. Affinities with braided riverbeds are related to the bed area of those rivers draining within 200 km and proportion of gravel in the substrate. Affinities with coastal turfs are related to proximity to the nearest turf and the proportion of humus in the substrate. Conclusions: Examining multiple scales of influence in a landscape context is essential to understand composition of naturally discrete ecosystems that span wide geographic ranges and to underpin their conservation management.

Scale‐specific processes shape plant community patterns in subtropical coastal grasslands

“…Other studies have already pointed out the greater influence of soil characteristics for fine‐scale assembly of coastal plant communities (Wiser et al . ) and grassland communities (Anderson et al . ; Auestad et al .…”

Mediterranean coastal dune systems: Which abiotic factors have the most influence on plant communities?

“…Along the sea-inland ecological gradient, a notable shift of the environmental parameters was found, which was connected with the shift of plant communities that go from the annual vegetation of drift lines to shrub communities of backdunes, as shown in other coastal dune systems (Sýkora et al, 2004;Ihm et al, 2007;Forey et al, 2008;Lane et al, 2008;Honrado et al, 2009;Wiser et al, 2010;Isermann, 2011). In particular, the CCA analysis highlighted how the distance to the coastline, the mean grain-size, the organic matter concentration and the shoreline trend constitute the most important parameters able to significantly affect the plant composition of the Tuscany coast.…”

Expanding an existing classification of New Zealand vegetation to include non-forested vegetation

“…nationwide surveys of sand dunes ;Johnson 1992;Partridge 1992) or were collected using a site-specific method (e.g. Cockayne & Calder 1932;Mark 1978;Walker & Lee 2002;Williams & Wiser 2004;Wiser et al 2010).…”