Welcome to DRAGNet!

The Disturbance and Recovery Across Global Grasslands Network

The Disturbance and Recovery Across Global Grasslands Network (DRAGNet) is a coordinated distributed experiment that assesses the generality of factors influencing responses to disturbance in herbaceous-dominated ecosystems. This network builds on two decades of highly successful collaborative research within the Nutrient Network (NutNet), but examines a new set of theoretically-motivated questions about the effects and interactions of two pervasive global changes: land disturbance and nutrient supply.

With DRAGNet, we are quantifying plant community assembly and ecosystem recovery following soil disturbance under a wide range of biotic and abiotic conditions, and testing under what conditions assembly or recovery interact with nutrient enrichment.

This experiment is timely and relevant, as physical disturbances are among the most pervasive impacts of humans on Earth (Ellis 2011; Higgins 2017). Habitat loss via land conversion for agriculture is a leading cause of extinction (Pimm et al. 1995), and biodiversity in grassland systems is particularly affected by land use change (Newbold et al. 2016). Even small-scale disturbances can have long-term impacts on grasslands (Cushman et al. 2004). While disturbances are an important driver of community dynamics and assembly alone (Chase 2003; Turner 2010), they now occur concurrently with other human impacts including increased nutrient supply (Steffen et al. 2015).

Primary goals of DRAGNet: 

1. Quantify resistance to, and recovery from, soil disturbance across a wide variety of grasslands under ambient and elevated nutrient supply.
2. Quantify resistance to, and recovery from, nutrient addition.
3. Assess the reproducibility of ecological experiments using data from sites that participate in both NutNet and DRAGNet and started nutrient addition treatments in different years.
4. Determine the relative importance of local and regional processes for community assembly by pairing theoretical models with core data and additional "add-on" seed bank and seed rain data.

DRAGNet Design and Implementation:

The DRAGNet protocol is described in detail here. In brief, each DRAGNet site consists of 3-5 blocks (spatial replicates), each with five plots (each sized 5 x 5 m) receiving one of five treatments: 1) Physical disturbance (annual removal of live and dead vegetation and rhizomes and soil tilling for three years), 3) Physical disturbance plus nutrient addition, 2) Long-term nutrient addition, 4) Short-term nutrient addition (five years of addition followed by “cessation” of treatment), or 5) No treatment (“control”). The core response variables are plant species composition, aboveground biomass, and light intercepted by the plant canopy. DRAGNet also includes a soil chemistry study and an optional seed bank and seed rain study. The design is flexible, to accommodate add-on studies at the site, region, or network level (e.g., trapping insects, measuring plant traits, tracking small mammal granivory, etc.).

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The time and effort to disturb the plots varies among sites, depending on vegetation, soils, etc. Completing the rest of the protocol (e.g., field sampling, plant sorting, and data entry) generally requires 1-3 days of work for 2-3 people. Sites do not need to participate in all parts of the study (e.g., even one set of observational measurements following our sampling protocol can help address a variety of questions and add context to treatment effects). We cannot provide funds for this project, but we have designed it to be inexpensive. For example, maintenance of the nutrient addition plots is only the cost of fertilizer (about $50 per year for a site in the US).

Collaboration in DRAGNet:

The collaborative nature of DRAGNet requires that all scientists are willing to share their core data with others in the network. Please read the guidelines for publication and authorship of DRAGNet manuscripts and datasets.

Benefits of participating in DRAGNet:

DRAGNet participants contribute to the collection of comparable data across continents, have access to analysis-ready datasets, and interact with a collaborative network of creative and thoughtful scientists from a variety of institutions around the world. Participants have many opportunities to help co-author publications that use DRAGNet data. Participants can also use DRAGNet as an experimental platform to answer new research questions via add-on studies at the site, region, or network level.

Contact the Network Coordinator to find out more about DRAGNet and to get involved!

References:

Borer, E.T., Grace, J.B., Harpole, W.S., MacDougall, A.S. & Seabloom, E.W. (2017). A decade of insights into grassland ecosystem responses to global environmental change. Nat. Ecol. Evol., 1, 1–7

Cushman, J., Trisha A. Tierney, & Jean M. Hinds. 2004. Variable Effects of Feral Pig Disturbances on Native and Exotic Plants in a California Grassland. Ecological Applications, 14(6), 1746-1756

Ellis, E.C. (2011). Anthropogenic transformation of the terrestrial biosphere. Philos. Trans. R. Soc. A Math. Phys. Eng. Sci., 369, 1010–1035 Higgins, S.I. (2017). Ecosystem assembly: A mission for terrestrial Earth system science. Ecosystems, 20, 69–77

Newbold, T., Hudson, L.W., Arnell, A.P., Contu, S., De Palma, A., Ferrier, S., et al. (2016). Has land use pushed terrestrial biodiversity beyond the planetary boundary? A global assessment. Science (80-. )., 354, 288–291

Pimm, S.L., Russell, G.J., Gittleman, J.L. & Brooks, T.M. (1995). The future of biodiversity. Science (80-. )., 269, 347–350

Steffen, W., Richardson, K., Rockstrom, J., Cornell, S.E., Fetzer, I., Bennett, E.M., et al. (2015). Planetary boundaries: Guiding human development on a changing planet. Science (80-. )., 347, 737–747

Turner, M.G. (2010). Disturbance and landscape dynamics in a changing world. Ecology, 91, 2833–2849