RhizoNet currently spans more than 10 sites and will include direct observations of belowground dynamics in over 70 species.  These observations are primarily based in monospecific plots but also includes multi-species competition trials and additional observations will be collected for a subset of species across multiple sites characterized by different climate and soil characteristics.  Coupled with long-term repeated belowground observations will be a set of complementary aboveground observations as well as intensive biomass assessments 

Many of the questions that underpin the creation of RhizoNet are centered on belowground dynamics and linkages between aboveground and belowground processes.
  • How do  lifespan, turnover, and phenology of fine roots and soil fungi vary across species and environments?  How does this variation impact plant function and ecosystem productivity?
  • What suites of belowground and whole-plant traits are coordinated or independent?  Where do fundamental tradeoffs exist?  
  • What direct and indirect interactions exist between fine root biomass, root demography, and soil microbial communities?  How can these complex relationships be better quantified?
In addition to these and other empirically focused questions, RhizoNet is also well-positioned to make significant contributions to ecosystem and global vegetation models.  Poor empirical quantification and parameterization of belowground processes in most models is increasingly recognized as a fundamental constraint limiting the ability of models to predict terrestrial responses to global environmental change.  By unifying what are often disparate data streams under a single research umbrella, RhizoNet can provide the most complete, robust, and detailed data sets available to modelers.  As such, additional questions addressed by RhizoNet will include:
  • What root and belowground processes express relatively small and relatively large variation across species and across environmental gradients?  Where large variation exists, can broad, predictable patterns be identified to simplify modeling efforts?
  • What information might be required to develop a complete and mechanistic model of fine root and rhizosphere functioning?  How might this complete model be simplified in such a way that still captures the majority of variability in rhizosphere activity with minimal computational effort?
Key to the success of RhizoNet is the development of a standardized set of methodologies and protocols to ensure that a common suite of above- and belowground pools and processes are measured across all sites and that data collected are complementary and directly comparable.  While detailed research plans are tailored to meet the needs and opportunities available at each site, there will also be a core set of data collected to immediately facilitate the development of a larger and more powerful data network.  Below are brief descriptions of the core data that forms the initial foundation of RhizoNet.  For more complete descriptions of the methods employed in RhizoNet please contact us.  

Targeted Observations        

Belowground

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Long-term measurements belowground include observations from minirhizotron cameras, root windows, and rhizotrons allowing for determination of lifespan, turnover, and phenology of fine roots and soil fungal structures (mycorrhizal tips, rhizomorphs, and hyphae).  Long-term measurements of soil moisture and temperature, nutrient mineralization rates, and enzyme activity will also be collected.  

Coupled with repeated, long-term observations will be a suite of measurements made once or only a few times during the coarse of the study.  These include assessments of root, fungal, and bacterial biomass, determination of soil chemical and physical properties, and basic measures of fine root anatomy, morphology, and chemistry. 

Aboveground

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To complement observations of belowground dynamics, repeated measures of leaf phenology and leaf area index, basic site climate indices, aboveground litterfall, and annual incremental DBH increase will be made.  At a few sites where preexisting instrumentation allows, comparisons will also be made between these relatively simple assessments of site productivity and more rigorous measures from eddy flux tower-based assessments.  Measures of whole-plant water status and sap flow may also be employed for a subset of sites and species.

Following identification of each site and plot, vegetation surveys will be conducted to determine stand densities (and species compositions in mixed plots) and to produce estimates of total aboveground biomass.  These estimates may then be updated annually based on measured changes in DBH within each plot.