Abstract
Higher biodiversity leads to more productive ecosystems which, in turn, supports more biodiversity. Ongoing global changes affect ecosystem productivity and, therefore, are expected to affect productivity-biodiversity relationships. However, the magnitude of these relationships may be affected by baseline biodiversity and its lifeforms. Cork oak (Quercus suber) woodlands are a highly biodiverse Mediterranean ecosystem managed for cork extraction; as a result of this management cork oak woodlands may have both tree and shrub canopies, just tree and just shrub canopies, and just grasslands. Trees, shrubs, and grasses may respond differently to climatic variables and their combination may, therefore, affect measurements of productivity and the resulting productivity-biodiversity relationships. Here, we asked whether the relationship between productivity and climate is affected by the responses of trees, shrubs, and grasses in cork oak woodlands in Southern Portugal. To answer this question, we linked a 15-year time series of Enhanced Vegetation Index (EVI) derived from Landsat satellites to micrometeorological data to assess the relationship between trends in EVI and climate. Between 2000 and 2013 we observed an overall decrease in EVI. However, EVI increased over cork oaks and decreased over shrublands. EVI trends were strongly positively related to changes in relative humidity and negatively related to temperature. The intra-annual EVI cycle of grasslands and sparse cork oak woodland without understorey (savannah-like ecosystem) had higher variation than the other land-cover types. These results suggest that oaks and shrubs have different responses to changes in water availability, which can be either related to oak physiology, to oaks being either more resilient or having lagged responses to changes in climate, or to the fact that shrublands start senesce earlier than oaks. Our results also suggest that in the future EVI could improve because the rate of increase in minimum EVI is greater than the rate of decrease in maximum EVI, and that this is contingent on management of the shrub understorey as it affects the rate of decrease in maximum EVI. This will be the challenge for the persistence of cork oak woodlands, their associated biodiversity and social-ecological system.
Highlights
One of the key ecological paradigms is the relationship between biodiversity and productivity [1,2].Higher biodiversity leads to more productive ecosystems [3,4], and more productive environments support more biodiversity [5,6]
Our results suggest that in the future Enhanced Vegetation Index (EVI) could improve because the rate of increase in minimum EVI is greater than the rate of decrease in maximum EVI, and that this is contingent on management of the shrub understorey as it affects the rate of decrease in maximum EVI
We found different temporal trends in productivity for the tree canopy and the shrub canopy, and these trends in productivity were positively associated with relative humidity and negatively with temperature
Summary
One of the key ecological paradigms is the relationship between biodiversity and productivity [1,2].Higher biodiversity leads to more productive ecosystems [3,4], and more productive environments support more biodiversity [5,6]. One of the key ecological paradigms is the relationship between biodiversity and productivity [1,2]. Resource acquisition can be done by obtaining the necessary resources along a productivity gradient, commonly referred to as niche complementarity [7]. 2016, 8, 486 resource utilization efficiency, which is called niche efficiency [8]. Both mechanisms link plant and animal biodiversity to ecosystem productivity [8,9], though provide only two of the many explanations and shapes of productivity-biodiversity relationships, highlighting the general need for more research linking patterns of primary productivity and functional types of organisms (or life-forms) that use resources in different ways [10]. Ongoing global changes are affecting ecosystem productivity [11,12,13]
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