We invite you to join a new global research network – the Disturbance and Resources Across Global Grasslands (DRAGNet) – aimed at assessing the generality and site-specificity of factors influencing disturbance recovery and community assembly in herbaceous dominated ecosystems.
This network builds from a decade of highly successful collaborative research by Nutrient Network, but examines a new set of theoretically-motivated questions about the effects and interactions between two pervasive global changes, land disturbance and elemental nutrient influx.
AIM & BACKGROUND
DRAGNet will quantify community assembly dynamics and trajectories of herbaceous plant community and ecosystem recovery under a wide range of biotic and abiotic conditions, and test whether assembly, recovery rate, or trajectory in herbaceous-dominated plant communities interacts with environmental nutrient enrichment.
We believe that this experiment is timely and widely relevant because 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 by feral pigs can have long-term impacts on grasslands (Cushman et al. 2004). Although disturbances are an important driver of community dynamics and assembly (Chase 2003; Turner 2010), they now occur concurrent with other human impacts including climate change and nutrient deposition (Steffen et al. 2015).
The four primary goals of DRAGNet are to:
(1) Quantify community assembly, vegetation recovery rates, and trajectories of change after disturbance across a wide variety of herbaceous-dominated sites under ambient and elevated nutrient supply.
(2) Determine the relative importance of local and regional processes for community assembly by pairing theoretical models with core and additional “add-on” seed bank/seed rain data.
(3) Quantify community resistance to, and resilience after, short-term nutrient addition.
(4) Gain insights into the reproducibility of ecological experiments by leveraging plot-level data from sites already participating in NutNet and replicating the same treatments (control and nutrients) in different starting years.
DESIGN & IMPLEMENTATION
Our detailed protocols are described on our website. The DRAGNet experiment will consist of a set of 3-5 completely randomized blocks (within-site spatial replicates), each with five, 5 x 5 m plots receiving either: long-term nutrient addition; a physical disturbance (annual removal of standing vegetation, litter, rhizomes and tilling of the soil); nutrient addition combined disturbance; short-term nutrient addition; or no treatments (controls). The core response variables will be plant species composition, aboveground standing crop, light intercepted by the plant canopy, and soil chemistry. These are identical to the NutNet experiment, but will also include sampling for an optional (but highly recommended) seed-bank and seed-rain study. The design has built-in flexibility for site-level or regional studies such as trapping insects, measuring plant traits, tracking small mammal granivory, etc. Because of the relatively low replication at each site, the power of DRAGNet resides in replication across sites.
The time and effort to disturb the plots (described in the detailed protocol) will vary among sites, depending on vegetation, soils, etc. However, post-disturbance field sampling, plant sorting, and data entry generally requires about 1-3 days for 2-3 people. The design also is modular; a one-time pre-treatment sampling (“observational dataset”) has proven extremely valuable for addressing a wide variety of questions, as well. We cannot provide funds for this project, but we have designed it to be inexpensive. For example, maintenance of the nutrient treatment plots is only the cost of fertilizer (~$50 for US participants).
Sites may join at any time, but to be eligible for the first round of “opt-out” papers (papers that include all participants by default), sites must establish their plots and collect baseline data no later than December 2022. We hope that sites will maintain their experiment for at least ten years, but we have designed the experiment to provide opportunities for meaningful experimental contributions on shorter timelines.
Our guidelines for network participation are the same as NutNet. The collaborative nature of DRAGNet requires that all scientists must be willing to share their core data with others in the network. We request that collaborators send us their site’s core data within 3 months of collection. All network members can access the network data thereafter, following network guidelines. Our goal is for project data to go into the public domain three years after collection or upon first publication.
One of the greatest advantages of contributing to DRAGNet, besides the collection of data comparable across continents, will be interactions by yourself and your lab with a collaborative network. In addition to many opportunities for coauthorhsip on DRAGNet publications, participants will be welcome to collaborate on research that uses over a decade of NutNet data from more than 100 sites around the world. DRAGNet also provides an experimental platform with capacity to answer research questions not yet envisioned, either via “add-on” studies that require new measurements, or with analyses of core data.
There are two primary ways that you can get involved in DRAGNet, either 1) by establishing the experiment in your herbaceous-dominated study system and committing to being involved in the network for the next five or more years (“experimental dataset”), or, if the first option requires too great a commitment, 2) by participating in the preliminary cross-site survey by collecting data on environmental factors, diversity, and productivity from your study system (“observational dataset”).
We hope you will agree with us that participation represents an unprecedented opportunity to conduct highly relevant, cross-site collaborative research that will allow us to ask a wide variety of questions about the role of disturbance and elemental resources in herbaceous plant communities, questions that would be impossible to address as comprehensively without this type of collaboration. If you want to contribute to DRAGNet, please fill out our online interest form (link below) by 31 August 2019. We hope you will join this new research initiative!
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 terrestiral 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
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Turner, M.G. (2010). Disturbance and landscape dynamics in a changng world. Ecology, 91, 2833–2849