Coexistence trend contingent to Mediterranean oaks with different leaf habits.

Arianna Di Paola,Simone Mereu,Antonio Trabucco,Alain Paquette,Francesco Paparella,Riccardo Valentini

doi:10.1002/ece3.2840

Abstract

In a previous work we developed a mathematical model to explain the co‐occurrence of evergreen and deciduous oak groups in the Mediterranean region, regarded as one of the distinctive features of Mediterranean biodiversity. The mathematical analysis showed that a stabilizing mechanism resulting from niche difference (i.e. different water use and water stress tolerance) between groups allows their coexistence at intermediate values of suitable soil water content. A simple formal derivation of the model expresses this hypothesis in a testable form linked uniquely to the actual evapotranspiration of forests community. In the present work we ascertain whether this simplified conclusion possesses some degree of explanatory power by comparing available data on oaks distributions and remotely sensed evapotranspiration (MODIS product) in a large‐scale survey embracing the western Mediterranean area. Our findings confirmed the basic assumptions of model addressed on large scale, but also revealed asymmetric responses to water use and water stress tolerance between evergreen and deciduous oaks that should be taken into account to increase the understating of species interactions and, ultimately, improve the modeling capacity to explain co‐occurrence.

Highlights

The Mediterranean region holds an extraordinary diversity of species because of the multitude of different habitats it contains (Cody, 1986)
Our findings confirmed the basic assumptions of the model at regional scale, and revealed asymmetric responses to water use and water stress tolerance between evergreen and deciduous oak groups that should be taken into account to increase the understating of species interactions and, improve the modeling capacity to explain oaks co-occurrence
The underlying principle of the model is that differences in water use and water stress tolerance between evergreen and deciduous oak groups allow their coexistence at intermediate interval of soil water content, overcoming the principle of competitive exclusion that, by contrast, prevails at the lower and upper end of suitable soil water content range

Summary

| INTRODUCTION

The Mediterranean region holds an extraordinary diversity of species because of the multitude of different habitats it contains (Cody, 1986). We show how a simple formal derivation of the model allows to express the criteria for a stable coexistence in a testable form solely linked to forest actual evapotranspiration (ET): the actual evapotranspiration of a forest composed only by evergreen oaks (ETE) should be lower than that of co-occurrence of both the groups (ETCO), which, in turn, should be lower than that of deciduous oaks community (ETD) To ascertain whether such a simplified description posses some degree of explanatory power, we compared the model derivation with existing data on oaks distributions and remote sensing derived ET (MODIS product) in a large-scale survey embracing the western Mediterranean area. Our findings confirmed the basic assumptions of the model at regional scale, and revealed asymmetric responses to water use and water stress tolerance between evergreen and deciduous oak groups that should be taken into account to increase the understating of species interactions and, improve the modeling capacity to explain oaks co-occurrence

| METHODS

| DISCUSSION

Findings

| CONCLUSION

DATA ACCESSIBILITY