The first chapter Dina Liebowitz's dissertation work is now available online in Freshwater Biology.  This paper examines the relationships among environmental conditions (especially dissolved oxygen concentrations), the abundance of grazing snails, and the presence of benthic algae in Florida springs. By comparing data from field surveys both within and across springs, Dina showed that the abundance of snails (especially the genus Elimia) is the primary determinant of the abundance of algae in Florida springs.   In addition, we found that algal abundance is generally either very high or very low, a pattern that is consistent with alternative stable states.  Finally, our field survey also shows that oxygen concentrations, among other environmental controls, influences the abundance of snails.  Putting these findings together, we suggest that even temporary declines in oxygen concentrations, which occur commonly in springs, could suppress snail populations and activity and allow algae to escape grazer control.   

Most of the management attention in springs has emphasized nutrient concentrations as the major driver of algal mats, a hypothesis which we have challenged pretty strongly in an earlier paper that first articulated the oxygen-grazer-algae cascade. Dina's other chapters examine these processes experimentally, and lead to similar conclusions.  Very exciting to have this work out, and congratulations Dina!

Our paper on the landscape pattern of cypress dome wetlands in Big Cypress National Preserve, led by Adam Watts, is available online at Earth Surface Processes and Landforms.  Using a variety of lines of evidence, we show that cypress domes are regularly distributed, and that this pattern is more strongly reflected in the bedrock and vegetation than in soil elevations. We also expand on and refine our conceptual model of how this pattern arises. In brief, we propose that cypress domes are drilling into the limestone bedrock via the acidity of organic matter and CO2 production by vegetation. This local positive feedback expands wetland basins vertically and laterally. As wetlands expand, they essentially come into competition for runoff from the adjacent uplands, which ultimately limits the size and density of wetlands on the landscape.  Patterns of soil phosphorus suggest that P mobilization by this dissolution may amplify this biogeomorphic feedback. This paper lays the foundation for our new NSF grant, which will support more mechanistic study of the processes that create these wetland basins and control their distribution on the landscape. 

Our Urban Homogenization group has a new paper out in the Proceedings of the National Academy of Sciences.  Led by Colin Polsky at Clark University, the paper shows that lawn care practices vary both among cities and among different life stages, development densities, and socio-economic groups within cities.  The major conceptual contributions of the paper are to introduce the idea of scale to our previous work on homogenization, and to demonstrate that lawn care practices may be very heterogeneous, even if the biophysical structure of residential landscapes is homogenized by urbanization.

Nutrient limitation happens when nutrient supply is insufficient to meet demand by biota, but most assessments of nutrient limitation are based only on concentration.  In streams, where metabolism is highly variable and streamflow continuously replenishes nutrient supply, concentration has been a poor predictor of nutrient limitation and autotroph biomass. We have a paper out in Freshwater Science that explores new predictors of nutrient limitation, based on nutrient spiraling theory and empirical measurements of metabolism and nutrient flux. The paper was led by Sean King, who finished his PhD at the University of Florida a few years ago, and is now at the Southwest Florida Water Management District (SWFWMD).  Congratulations Sean!

We have two new papers that just came out as part of a special issue of Frontiers in Ecology and the Environment on continental scale ecology.  

The first paper (Heffernan et al. 2014; Macrosystems Ecology: Understanding Ecological Pattern and Processes at Continental Scales) proposes a framework for incorporating a systems perspective more completely into the study of broad-scale ecological phenomena.  This means thinking about processes like feedbacks between vegetation and climate, long-distance connections between ecosystems, and ways in which broad- and fine-scale phenomena influence one another.  We think that this broad scale systems perspective ('Macrosystems Ecology') is going to be essential for predicting the effects of many different anthropogenic changes that have causes and consequences at the scale of whole regions and continents.  One challenge in writing this paper is that ecologists and others have been thinking about regions and continents for a long time, in sub-disciplines like biogeography and related fields like climate science.  We argue that two things are changing - 1) across these fields, we are incorporating more and more process into that understanding (which is made easier through data sets that have a fine resolution but cover broad extents); and 2) that we are able to make more and more connections across different types of phenomena (e.g., linking climate change, population genetics, and habitat loss; or understanding the diverse ecological consequences of bark beetle outbreaks).  We also deal with the question of 'What is distinct about macrosystems?'  Again, part of the challenge is that many ecological theories are supposed to apply to all scales, so lots of characteristics of macrosystems are likely to fit within such theory.  One the other hand, some may not; one way (the only way?) to figure out whether macrosystems are distinct is to study regions and continents as systems through the lens of such theory.  There is already some neat work that tries to do this, and hopefully lots more on the way!

The second paper (Groffman et al. 2014; Ecological homogenization of urban USA) is an overview of our 'Urban Homogenization' project, and presents some of the preliminary data that led us to this work in the first place. This is the project that includes Meredith Steele's work on surface water features in cities. 

Meredith Steele's paper (with a long list of co-authors) on the surface water characteristics of US cities has been accepted at Ecosystems!  Congratulations Meredith!

Abstract: Earth’s surface is rapidly urbanizing, resulting in dramatic changes in the abundance, distribution and character of surface water features in urban landscapes. However, the scope and consequences of surface water redistribution at broad spatial scales are not well understood. We hypothesized that urbanization will lead to convergent surface water abundance and distribution: in other words, cities will gain or lose water such that they become more similar to each other than are their surrounding natural landscapes. Using a database of more than 1 million water bodies and 1 million km of streams, we compared the surface water of 100 US cities with their surrounding undeveloped land. We evaluated differences in areal (AWB) and numeric densities (NWB) of water bodies (lakes, wetlands, etc.), the morphological characteristics of water bodies (size), and the density (DC ) of surface flow channels (i.e. streams and rivers). The variance of urban AWB, NWB, and DC across the 100 MSAs decreased, by 89%, 25%, and 71% respectively, compared to undeveloped land. These data show that many cities are surface-water poor relative to undeveloped land; however, in drier landscapes urbanization increases the occurrence of surface water. This convergence pattern strengthened with development intensity, such that high intensity urban development had an areal water body density 98% less than undeveloped lands. Urbanization appears to drive the convergence of hydrological features across the US, such that surface water distributions of cities are more similar to each other than to their surrounding landscapes.

Megan Fork's paper on DOC and denitrification, published in Ecosystems, is now available online.  This work, which comes from Megan's MS thesis, uses a natural gradient in dissolved organic matter (DOC) concentration to understand how terrestrially-derived DOC influences aquatic denitrification.  We found that this DOC does not directly stimulate or inhibit denitrification, but that denitrification becomes more limited by DOC as DOC concentrations increase.  The explanation for this counter-intuitive finding is that DOC reduces light, and therefore the release of labile DOC by macrophytes and algae.  This paper provides additional evidence for the importance of in-stream primary production for denitrification in larger rivers, and has implications for how aquatic ecosystems may respond to future changes in DOC.  Read the whole thing here, and congratulations Megan! 

New paper on hydrologic feedbacks in the Everglades has been published in PLoS One.  In this study, we develop a mathematical model of interactions between peat accumulation, vegetation productivity, soil elevation, and water flow.  We show that the resulting feedbacks can cause spontaneous divergence of ridges and sloughs, and that these feedbacks act differentially with direction.  The model provides a range of predictions that we are hoping to test with data from our Everglades monitoring project.  You can download the paper here.

Our paper on ecohydrologic feedbacks and pattern formation has just been accepted for publication in PLoS One.  This paper uses a simple quasi-spatial model to show that the need to route water through the Everglades landscape, in conjunction with local positive feedbacks on peat accretion, can produce directional feedbacks that generate flow-perpendicular pattern.  The model also makes a number of predictions about relationships between water flow and microtopographic variation that we hope to test with our large-scale Everglades field sampling.  Will post a link to the paper as soon as it is in press.

Ecosphere has just published a new concept paper, led by Ryan Sponseller, with myself and our graduate advisor Stuart Fisher.  The paper is titled 'On the multiple ecological roles of water in river networks.' It addresses how the diverse effects of water (as a resource, habitat, vector for material transport, and agent of disturbance) shape downstream change in drainage networks, and how the interactions among those roles vary within catchments and across biomes.  We contrast patterns in Sycamore Creek, AZ with prevailing models of how streams change as they get bigger, and argue that the interactions among drying, flooding, and changing connectivity are needed to explain how systems change. Part of the rationale for this is that many streams are likely to see increased drying stress as climate, land use, and water management change.  This paper emerged from the synthetic chapter of Ryan's dissertation, and we have been working on it off and on for the last six(!) years. So it's great to finally have it out.