Nitrogen increases early-stage and slows late-stage decomposition across diverse grasslands

Allison L. Gill, Peter B. Adler, Elizabeth T. Borer, Christopher R. Buyarski, Elsa E. Cleland, Carla M. D’Antonio, Kendi F. Davies, Daniel S. Gruner, W. Stanley Harpole, Kirsten S. Hofmockel, Andrew S. MacDougall, Rebecca L. McCulley, Brett A. Melbourne, Joslin L. Moore, John W. Morgan, Anita C. Risch, Martin Schütz, Eric W. Seabloom, Justin P. Wright, Louie H. Yang, Sarah E. Hobbie


1. To evaluate how increased anthropogenic nutrient inputs alter carbon cycling in grasslands, we conducted a litter decomposition study across 20 temperate grasslands on three continents within the Nutrient Network, a globally distributed nutrient enrichment experiment

2. We determined the effects of experimental nitrogen (N), phosphorus (P), and potassium plus micronutrient (Kμ) additions on decomposition of a common tree leaf litter in a long-term study (maximum of 7 years; exact deployment period varied across sites). The use of higher-order decomposition models allowed us to distinguish between effects of nutrients on early- versus late-stage decomposition.

3. Across continents, addition of nitrogen (but not other nutrients) accelerated early-stage decomposition and slowed late-stage decomposition, increasing the slowly decomposing fraction by 28% and the overall litter mean residence time by 58%.

4. Synthesis. Using a novel, long-term cross-site experiment, we found widespread evidence that nitrogen enhances the early stages of aboveground plant litter decomposition across diverse and widespread temperate grassland sites, but slows late-stage decomposition. These findings were corroborated by fitting the data to multiple decomposition models and have implications for nitrogen effects on soil organic matter formation. For example, following nitrogen enrichment, increased microbial processing of litter substrates early in decomposition could promote production and transfer of low molecular weight compounds to soils, and potentially enhance stabilization of mineral-associated organic matter. By contrast, by slowing late-stage decomposition, nitrogen enrichment could promote particulate organic matter (POM) accumulation. Such hypotheses deserve further testing.

Journal of Ecology

Biodiversity and infrastructure interact to drive tourism to and within Costa Rica

Alejandra Echeverri, Jeffrey R. Smith, Dylan MacArthur-Waltz, Katherine S. Lauck, Christopher B. Anderson, Rafael Monge Vargas, Irene Alvarado Quesada, Spencer A. Wood, Rebecca Chaplin-Kramer, Gretchen C. Daily


Nature-based tourism has potential to sustain biodiversity and economic development, yet the degree to which biodiversity drives tourism patterns, especially relative to infrastructure, is poorly understood. Here, we examine relationships between different types of biodiversity and different types of tourism in Costa Rica to address three questions. First, what is the contribution of species richness in explaining patterns of tourism in protected areas and country-wide in Costa Rica? Second, how similar are the patterns for birdwatching tourism compared to those of overall tourism? Third, where in the country is biodiversity contributing more than other factors to birdwatching tourism and to overall tourism? We integrated environmental data and species occurrence records to build species distribution models for 66 species of amphibians, reptiles, and mammals, and for 699 bird species. We used built infrastructure variables (hotel density and distance to roads), protected area size, distance to protected areas, and distance to water as covariates to evaluate the relative importance of biodiversity in predicting birdwatching tourism (via eBird checklists) and overall tourism (via Flickr photographs) within Costa Rica. We found that while the role of infrastructure is larger than any other variable, it alone is not sufficient to explain birdwatching and tourism patterns. Including biodiversity adds predictive power and alters spatial patterns of predicted tourism. Our results suggest that investments in infrastructure must be paired with successful biodiversity conservation for tourism to generate the economic revenue that countries like Costa Rica derive from it, now and into the future.