Daniel A. Sarr

A HIERARCHICAL PERSPECTIVE OF PLANT DIVERSITY

Predictive models of plant diversity have typically focused on either a landscape’s capacity for richness (equilibrium models), or on the processes that regulate competitive exclusion, and thus allow species to coexist (nonequilibrium models). Here, we review the concepts and purposes of a hierarchical, multiscale model of the controls of plant diversity that incorporates the equilibrium model of climatic favorability at macroscales, nonequilibrium models of competition at microscales, and a mixed model emphasizing environmental heterogeneity at mesoscales. We evaluate the conceptual model using published data from three spatially nested datasets: (1) a macroscale analysis of ecoregions in the continental and western U.S.; (2) a mesoscale study in California; and (3) a microscale study in the Siskiyou Mountains of Oregon and California. At the macroscale (areas from 3889 km2 to 638,300 km2), climate (actual evaporation) was a strong predictor of tree diversity (R2 = 0.80), as predicted by the conceptual model, but area was a better predictor for vascular plant diversity overall (R2 = 0.38), which suggests different types of plants differ in their sensitivity to climatic controls. At mesoscales (areas from 1111 km2 to 15,833 km2 ), climate was still an important predictor of richness (R2 = 0.52), but, as expected, topographic heterogeneity explained an important share of the variance (R2 = 0.19), showed positive correlations with diversity of trees, shrubs, and annual and perennial herbs, and was the primary predictor of shrub and annual plant species richness. At microscales (0.1 ha plots), spatial patterns of diversity showed a clear unimodal pattern along a climate‐driven productivity gradient and a negative relationship with soil fertility. The strong decline in understory and total diversity at the most productive sites suggests that competitive controls, as predicted, can override climatic controls at this scale. We conclude that this hierarchical, multiscale model provides a sound basis to understand and analyze plant species diversity. Specifically, future research should employ the principles in this paper to explore climatic controls on species richness of different life forms, better quantify environmental heterogeneity in landscapes, and analyze how these large‐scale factors interact with local nonequilibrium dynamics to maintain plant diversity.

Forest management, restoration, and designer ecosystems: Integrating strategies for a crowded planet

Abstract As the global human population increases, the demand to conserve, restore, create, and sustainably manage ecosystems will increase as well. Forested ecosystems are of particular interest because of the biodiversity they support and their diverse values to people. Developments in conservation, restoration forestry, and in the study of designer ecosystems provide a diverse set of tools with which to pursue sustainable forestry goals. Nonetheless, we suggest that sustainable forestry can only be achieved by fully considering ecological, economic, and social needs in landscapes. This will require a clear realization of the trade-offs in site-specific management approaches and a multifaceted, landscape-scale perspective for evaluation of sustainability criteria. We propose collaborative creation of Sustainable Forestry Portfolios as a means to encourage the breadth of thinking required to guide sustainable forest management. We discuss 3 examples of Sustainable Forestry Portfolios with relevance to different settings in the future: 1) the Triad Approach, 2) Forest Landscape Restoration, and 3) Urban Forestry. In all settings, sustainable forestry is not solely a technical problem, but a challenge that must be met through a multidimensional perspective, interdisciplinary collaboration, and with active engagement of the people that live and work in the landscape.

A power analysis for multivariate tests of temporal trend in species composition

Long-term monitoring programs emphasize power analysis as a tool to determine the sampling effort necessary to effectively document ecologically significant changes in ecosystems. Programs that monitor entire multispecies assemblages require a method for determining the power of multivariate statistical models to detect trend. We provide a method to simulate presence-absence species assemblage data that are consistent with increasing or decreasing directional change in species composition within multiple sites. This step is the foundation for using Monte Carlo methods to approximate the power of any multivariate method for detecting temporal trends. We focus on comparing the power of the Mantel test, permutational multivariate analysis of variance, and constrained analysis of principal coordinates. We find that the power of the various methods we investigate is sensitive to the number of species in the community, univariate species patterns, and the number of sites sampled over time. For increasing directional change scenarios, constrained analysis of principal coordinates was as or more powerful than permutational multivariate analysis of variance, the Mantel test was the least powerful. However, in our investigation of decreasing directional change, the Mantel test was typically as or more powerful than the other models.

Bird Communities and Environmental Correlates in Southern Oregon and Northern California, USA

We examined avian community ecology in the Klamath Ecoregion and determined that individual bird species co-exist spatially to form 29 statistically distinguishable bird groups. We identified climate, geography, and vegetation metrics that are correlated with these 29 bird groups at three scales: Klamath Ecoregion, vegetation formation (agriculture, conifer, mixed conifer/hardwood, shrubland), and National Park Service unit. Two climate variables (breeding season mean temperature and temperature range) and one geography variable (elevation) were correlated at all scales, suggesting that for some vegetation formations and park units there is sufficient variation in climate and geography to be an important driver of bird communities, a level of variation we expected only at the broader scale. We found vegetation to be important at all scales, with coarse metrics (environmental site potential and existing vegetation formation) meaningful across all scales and structural vegetation patterns (e.g. succession, disturbance) important only at the scale of vegetation formation or park unit. Additionally, we examined how well six National Park Service units represent bird communities in the broader Klamath Ecoregion. Park units are inclusive of most bird communities with the exception of the oak woodland community; mature conifer forests are well represented, primarily associated with conifer canopy and lacking multi-layered structure. Identifying environmental factors that shape bird communities at three scales within this region is important; such insights can inform local and regional land management decisions necessary to ensure bird conservation in this globally significant region.

Comparing Ecoregional Classifications for Natural Areas Management in the Klamath Region, USA

ABSTRACT: We compared three existing ecoregional classification schemes (Bailey, Omernik, and World Wildlife Fund) with two derived schemes (Omernik Revised and Climate Zones) to explore their effectiveness in explaining species distributions and to better understand natural resource geography in the Klamath Region, USA. We analyzed presence/absence data derived from digital distribution maps for trees, amphibians, large mammals, small mammals, migrant birds, and resident birds using three statistical analyses of classification accuracy (Analysis of Similarity, Canonical Analysis of Principal Coordinates, and Classification Strength). The classifications were roughly comparable in classification accuracy, with Omernik Revised showing the best overall performance. Trees showed the strongest fidelity to the classifications, and large mammals showed the weakest fidelity. We discuss the implications for regional biogeography and describe how intermediate resolution ecoregional classifications may be appropriate for use as natural areas management domains.

Assembly Rules and Restoration Ecology: Bridging the Gap between Theory and Practice

I must admit to being a model-curmudgeon and no aficionado of computers. Useful as computers are, it is tough to convince me that today’s techno-tools are even appropriate for something as human as conflict resolution. Since human nature has those best and worst, blessing-or-curse characteristics that drive how we solve problems and approach conflict, mediation and other types of conflict resolution need intuition and good personal listening skills to dissect interests from emotions. How in the world can we quantify and model the gamut of human personalities and environmental complexities? However, after being assured in the author’s Preface that this was not just about computers, and knowing that mediation practitioners need all the help and available tools we can get, I dug into what I thought would be another tortuous recitation of the glories of computer modeling. I surprised myself by becoming hooked after the introductory chapter and experiencing a change in mind about using models.