Abstract
The impact of productivity on species diversity is often studied at small spatial scales and without taking additional environmental factors into account. Focusing on small spatial scales removes important regional scale effects, such as the role of land cover heterogeneity. Here, we use a regional spatial scale (10 km square) to establish the relationship between productivity and vascular plant species richness across the island of Ireland that takes into account variation in land cover. We used generalized additive mixed effects models to relate species richness, estimated from biological records, to plant productivity. Productivity was quantified by the satellite-derived enhanced vegetation index. The productivity-diversity relationship was fitted for three land cover types: pasture-dominated, heterogeneous, and non-pasture-dominated landscapes. We find that species richness decreases with increasing productivity, especially at higher productivity levels. This decreasing relationship appears to be driven by pasture-dominated areas. The relationship between species richness and heterogeneity in productivity (both spatial and temporal) varies with land cover. Our results suggest that the impact of pasture on species richness extends beyond field level. The effect of human modified landscapes, therefore, is important to consider when investigating classical ecological relationships, particularly at the wider landscape scale.
Highlights
Understanding how biodiversity varies with environmental predictors such as energy availability is crucial to improving spatial predictions of how biodiversity will change under scenarios of global change (Mateo, Mokany & Guisan, 2017)
There was a non-linear relationship between mean enhanced vegetation index (EVI) and species richness showing a decrease at higher levels of mean EVI (F = 14.983, d.f. = 4.087, P < 0.001) whilst species richness increased with the spatial standard deviation of EVI (F = 8.768, d.f. = 2.961, P < 0.001)
EVI and land cover relationships Incorporating land cover variables into the productivity-diversity model reduced the Akaike Information Criterion from 6,843.558 to 6,817.637, indicating including land cover improves the predictive performance of the model
Summary
Understanding how biodiversity varies with environmental predictors such as energy availability is crucial to improving spatial predictions of how biodiversity will change under scenarios of global change (Mateo, Mokany & Guisan, 2017). Land cover drives large scale productivity-diversity relationships in Irish vascular plants. The unimodal form is widely accepted in plant ecology, at the regional scale (Pärtel, Laanisto & Zobel, 2007), whilst at larger scales, an increasing monotonic relationship is often observed (Evans, Warren & Gaston, 2005; Gillman & Wright, 2006), Fraser et al (2015) demonstrate a unimodal form for plants at both global and regional extents
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