Spatial Scaling Add-On Study

Goals: Our aim is to understand the spatial scaling of communities and community re-assembly and how the DRAGNet treatments affect the spatial scaling of plant diversity (species-area relationships). These additional data, using simple and quick methods, will also help inform our understanding of the local spatial processes underlying relationships among plant diversity, turnover, and productivity.  

Why?:  We think this is an important topic that DRAGNet is positioned to address. 

* Species assembly and species diversity are multivariate, scale-dependent phenomena. Measurements (e.g., richness taken at a single scale may not be comparable across sites: effect size differences at one scale may differ in magnitude or sign at a different scale, and spatial processes may operate at different scales at different sites. Furthermore, treatments such as nutrient addition may change the scaling relationships for reassembling communities in different and informative ways. 

* Parameters of the resulting species-area functions that we can build from this multi-scale sampling will inform estimates of species pool size, spatial pattern differences and "probabilities of new species encounter” (see: Chase, J. M., & T. M. Knight. 2013).

* Finally, this will lead to awesome manuscripts: we will be generating one of the best ecological datasets to date to address diversity-scaling relationships, not just across sites but also across treatments (see list of questions below). 

The protocol for this add-on study is based on a well-established method of estimating species-area relationships (Peet et al. 1998, Fridley et al. 2005, Seabloom et al 2020). Exactly these same data have been collected in NutNet, leading to papers such as Seabloom et al 2020 – and a dataset that continues to be used for additional analyses. It’s simple and fast and will be familiar to anyone who has constructed a species-area curve before. (Some of us also find it fun – we finally get to count and include all the other species we see just outside our usual sampling quadrats! – and it gives fascinating insights into the spatial diversity patterns within a site and across treatments!)  

How?: In brief, we record species presence (not cover) in successively larger quadrats from 0.01-m2 “mini-quadrat” (a.k.a., “cutie-quadrat”) areas to the entire 25-m2 plot. This protocol is complementary to the % Cover core sampling protocol we do each year (see attached “Protocol” slides for details), and it takes approximately 2-3 additional person-hours per site (4-6 person-minutes per plot) to complete. Sites with high plant density/species density or those limited in time may opt to do the protocol in only Control, NPK+, tilled, and tilled x NPK+ plots.

This simple procedure can potentially address many exciting questions, including:

1. Do diversity-productivity relationships change with the spatial scale at which we measure plant diversity?

2. What is the spatial dependence of communities reassembling following disturbance – and do nutrients change this?

3. Do nutrients or tilling act (alone or together) at different spatial scales in regulating species diversity (homogenizing vs. increasing heterogeneity)?

Finally, by repeating the study for 3 or more successive years, we can explore

4. How do spatial and temporal turnover interact to regulate species diversity, and how do disturbance and nutrients impact trajectories of spatial and temporal turnover? (See Hillebrand et al. 2016)

I’m in! What do I do to contribute to this add-on?:

To participate in this ‘add-on’ study, site leads should ideally complete the protocol within one year (by 15 June 2025) at the time of peak biomass (while you do your species cover assessments at your site). This first year of data will be used to address the first three questions outlined above, each of which we think could become an opt-in paper.

If you can do this for 3 years, at the end of this more extended data collection (2028) we will assess the fourth topic, potentially at a DRAGNet workshop.

If you are unable to begin this year, but want to contribute, let us know! We’ll figure something out.

Please contact the DRAGNet coordinators if you plan to participate.

Contact us with questions.