Theoretical models explore only the logical consequence of assumptions-the difficulty in testing both the assumptions and outcomes (dashed line) is the weak link. The pragmatic approach (B) offers a middle approach.

The two extremes are theoretical models (A) and collections of data (C).

The bad news is that far too few of these models are appreciated.

Conclusions The good news is that managers faced with protecting or restoring landscapes already have this arsenal of tools at their disposal.

The following models are reviewed: (1) species–area: larger areas usually contain more species (2) species–biomass: plant diversity is maximized at intermediate levels of biomass (3) centrifugal organization: multiple intersecting environmental gradients maintain regional landscape biodiversity (4) species–frequency: a few species are frequent while most are infrequent (5) competitive hierarchies: in the absence of constraints, large canopy-forming species dominate patches of landscape, reducing biological diversity and (6) intermediate disturbance: perturbations such as water level fluctuations, fire and grazing are essential for maintaining plant diversity. My own work may seem rather prominent, but the application and refinement of these models has been a theme for me and my many students over decades.

Six Pragmatic Models For each model, key citations and an array of examples are provided, with particular emphasis on wetlands, since ‘wet and wild’ was my assigned theme for the Botanical Society of America in 2003.

Although theoretical models continue to receive far more space and headlines in scientific journals, more managers need to understand that pragmatic, rather than theoretical, models have the most promise for yielding results that can be applied immediately to plant communities.

As a guide to assist managers in maintaining plant diversity, six pragmatic models are introduced that are already available.

With perhaps one-third of the world's flora facing extinction, scientists and conservation managers will need to work rapidly and collaboratively, recognizing each other's strengths and limitations. Activities must be guided by sound scientific principles, practical conservation tools, and clear priorities.

Background There is a compelling need to protect natural plant communities and restore them in degraded landscapes.

Terrestrial plant ecology barbour pdf