Enhancing Existing Experiment

Enhancing Existing Experiments

There are numerous precipitation manipulation experiments currently being carried out by the scientific community, and these have already been subjected to meta-analyses. With Drought-Net, we will take the next step forward by coordinating new standardized measurements across a range of ongoing experiments – essentially envisioning these as a network-scale platform that can be leveraged to advance our understanding of drought well beyond the individual site scale. Thus, a primary goal of EEE is to recruit researchers to participate in new and innovative network-level studies based on this existing experimental platform.

Drought-Net participants, including the PIs of many of these experiments, are challenged to take advantage of existing experiments in a highly coordinated and systematic fashion. This will require Drought-Net participants to 1) determine the kinds of response variables that, if measured comparably in existing experiments, would yield new insight into the mechanistic basis of differential ecosystem sensitivity to drought, 2) agree upon standardized and relatively non-intrusive measurement protocols for these response variables, 3) publicize these research plans and actively advocate for them in order to enlist participants, 4) directly recruit PIs of ongoing experiments to either make these measurements themselves or allow others to do so, and 5) synthesize data resulting from EEE studies to assess mechanisms underlying differential ecosystem sensitivity to drought.

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Enhancing Existing Experiment

Alcornocales Natural Park

The rainfall exclusion experiment of the Alcornocales Natural Park (southern Spain) involves two different sites about 5 km apart: Gamir and Marrufo. Gamir is a closed forest dominated by the Mediterranean oaks Quercus suber and Quercus canariensis, whereas Marrufo is an open woodland dominated by Quercus suber and Olea europaea var. sylvestris. Both forests are invaded by the exotic soil-borne pathogen Phytophthora cinnamomi. 

Enhancing Existing Experiment

Bayreuth_EVENT I

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Bayreuth_EVENT II

Basic hypotheses:

Enhancing Existing Experiment

Bayreuth_SIGNAL

Enhancing Existing Experiment

Bivens Arm invasion x drought

see Alba et al 2017 for details

Enhancing Existing Experiment

DRI-Grass

Active rainfall manipulation involving five treatments in sheltered plots (each with 6 replicates):

Ambient

+50%

-50%

Altered frequency (one rain event every 3 weeks, representing ambient rainfall during that period)

Summer drought (typically Dec-end Feb, each Australian summer)

Enhancing Existing Experiment

Elizabeth Woods

  Present are two shelters and two control sites.  Based on a mycorrhizal associated framework, one treatment and control are dominated by Quercus rubra and Carya ovata; ectomycorrhizal associated trees.  The other treatment and control sites are dominated by Acer saccharum and Liriodendron tulipifera; arbuscular mycorrhizal associated trees.  

Enhancing Existing Experiment

Foxton Fife

 

Enhancing Existing Experiment

France-Puéchabon

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Garraf

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Jornada LTER

The objectives of this long-term study are: (1) to assess the effects of directional and prolonged changes in precipitation amount and variability on population, community and ecosystem processes; (2) to elucidate the mechanisms behind those changes, and finally (3) to predict the future state of drylands functioning under novel climate conditions.

Enhancing Existing Experiment

Jornada LTER

The objectives of this long-term study are: (1) to assess the effects of directional and prolonged changes in precipitation amount and variability on population, community and ecosystem processes; (2) to elucidate the mechanisms behind those changes, and finally (3) to predict the future state of drylands functioning under novel climate conditions.

Enhancing Existing Experiment

Loma Ridge

This experiment is part of the Loma Ridge Global Change Experiment, established by Michael Goulden in 2007. There are two ecosystem types, grassland and shrubland, with more studies completed in the grassland. The plots in the shrubland are 4 times the area and twice the height of the grassland. In 2014, half of the manipulated plots were designated "recovery" plots and the precipitation manipulation was ended. This experiment is also split-plot factorial with nitrogen addition (60 kg/ha/yr).

Enhancing Existing Experiment

Mols

The site is a lowland heathland on sandy moraine co-dominated by the shrub Calluna vulgaris and the grass Deschampsia flexuosa.

It is 57 m a.s.l. and 3 km from the sea. Precipitation at the site is 550 mm (30 yr mean), annual temperature is 7.7 °C (30 yr. mean) (average January 1.7 °C, average July 17.5 °C). 

Nitrogen deposition is in the low end of the range within the INCREASE network with c. 13 kg N/ha/yr (3 yr mean in wet deposition).

Enhancing Existing Experiment

Oldebroek

Drought manipulations as described have been carried out starting 1999 until 2017 (18 years), while 1998 was a pretreatment year. Plans for the next future (starting 2019) are to transform the active manipulation into a passive, drought-net design. This would mean that the "old" manipulation of 3 months no precipitation (an average decrease of 20% on an annual basis), would change to a year long decrease in precipitation of 20% or any other percentage (not yet decided).

Enhancing Existing Experiment

Pfynwald

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Prades

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Purdue Wildlife Area

 

 

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South Coast Research Extension Center

Question: Are hydraulic traits in dominant coastal sage scrub shrub species plastic in response to altered precipitation regimes and does plasticity in these traits change the shrubs risk of drought induced mortality.

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US Sheep Experiment Station

We use the Gherardi et al approach, passive drought shelter, collect water and pump on to irrigated plots.

We record community composition with individual-level mapping, which gives us demographic data, but means our community level data are a little "nonstandard" (some life forms represented as canopy cover, others basal cover, others just density).