Productivity and species richness in an arid ecosystem: a long-term perspective

Abstract

There is little consensus on the form of the relationship between biodiversity and productivity, and most of the research examining it has been done in temperate grasslands, with arid ecosystems receiving comparatively little attention. Using 9 years of data collected using standardized sampling methods from five different community types in the Chihuahuan Desert (Jornada Basin Long-Term Ecological Research site, New Mexico, USA), we evaluate the relationship between productivity and species richness at multiple spatial scales. The relationship was consistently unimodal at the largest scale considered; however, community types differed in both the form of the relationship and the degree to which patterns fluctuated over time. Although significant linear and unimodal patterns were evident, these models fit poorly, suggesting that annual primary productivity is a weak predictor of mean species richness in arid communities. We suggest that productivity -diversity relationships are best described by a boundary that places an upper limit on species coexistence across the gradient of productivity for a site. This upper limit often appears to be maximized at intermediate levels of productivity, but it has relatively few points on the downward portion of the boundary. By focusing efforts on characterizing boundaries, approaches should be developed to determine the factors that are reducing species richness compared to what would be expected, given the level of productivity.

Patterns of tree species richness in Jalisco, Mexico: relation to topography, climate and forest structure

“…Pausas and Austin (2001) point out that the main factors determining species richness at the local level are resource availability and response to environmental variables that have a direct impact on plant growth or on available resources. This concept of a resource boundary is similar in concept to the optimal curve theory proposed by Grime (1979), Tilman (1982), Aronson and Shimida (1992), Cox et al (2006) to describe the relationship between species richness and various abiotic factors. An ''extreme quantile curve estimation'' approach was used to approximate the boundary conditions of significant explanatory variables identified in the GLM.…”

“…The next step in the analysis was to establish the resource boundary for the set of responses in species richness to the important explanatory variables a Seasonal precipitation = average precipitation for a 3 month period (winter-December, January and February; Spring-March, April and May; Summer-June, July and August; Fall-September, October and November b Clay, sand and silt = percent particle size distribution in the top 10 cm of the soil identified in the GLM (Cox et al 2006;Bouchard et al 2005;Girard and Jacob 2004). This boundary represents the maximum potential response in species richness to different levels of an explanatory variable, conditioned on the assumption that all other factors are at their optimal.…”

Partitioning Tree Species Diversity and Developmental Changes in Habitat Associations in a Subtropical Evergreen Broadleaf Secondary Forest in Southern China

“…If the vertex of the curve occurs between the minimum and maximum independent variable in the data, the relationship is unimodal or U-shaped. If not, the relationship is nonlinear but monotonic [42].…”

Aboveground production and species richness of annuals in Chihuahuan Desert grassland and shrubland plant communities

“…Much progress has been made towards understanding the structure, primary production, species richness and ecological significance of annual plants in aridland ecosystems during the last decade (Boeken et al, 1998;Cox et al, 2006;Guo et al, 2002;Muldavin et al, 2008;Yin et al, 2005). Although it is well known that rainfall is the main factor controlling germination, growth and productivity of annuals in many desert ecosystems (Beatley, 1974;Bestelmeyer et al, 2003;Gutierrez and Whitford, 1987;Knapp and Smith, 2001;Paruelo et al, 1999;Went, 1949;Yahdjian and Sala, 2006), the relationship between interannual variability in precipitation and temporal variability in annual plant production at a given site is often weak (Bai et al, 2008).…”