Soil nematodes modify interactions between nitrogen-fixing and non-fixing tree seedlings from late, but not early, successional stages dataset

Abstract: Plant community dynamics are influenced by interspecific interactions. Previous studies have shown that soil organisms play a key role in such interactions, but few studies have quantified soil fauna contributions. Methods: We investigated the effects of root lesion (RLN) and bacterial feeding (BFN) nematodes on the interaction between seedlings of nitrogen-(N)-fixing tree species of Acacia and non-fixing Banksia from early and late successional stages of a temperate forest in a pot experiment. Results: Nematodes had consistent, albeit minor, negative effects on both N-fixers and non-fixers in the early successional stage scenario. By contrast, BFNs increased biomass production of both species in late-stage monocultures and in Banksia in mixed cultures. Moreover, RLNs negatively affected late-stage Banksia in monocultures but promoted its biomass production when grown with Acacia. Reduced 15N concentration in Banksia indicates that the switch was driven by transfer of N from Acacia facilitated by RLN. Conclusions: Soil nematodes thus moderate interspecific interactions differently in early and late successional stages.

Plant June 2017 dataset:

Plant measurements

Measurements taken in Acacia and Banksia plants.

bio: plants were left to dry 48 hours at 60�C, and then weighed to obtain dry biomass genus refers to plant genus: acacia and banksia species refers to plant species nematode refers to nematode inoculation: CTL (no nematodes); BFN (bacterial feeding nematodes added); RLN (root feeding nematodes added) grown refers to plant mixture: alone (plant grown with members of the same species) and both (plant grown in mixture) Total: whole plant (root & shoot) dry mass, in grams Above: shoot dry mass, in grams Below: root dry mass, in grams

cn: carbon and nitrogen content of plants, analyzed by an Elementar Vario Micro Cube elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany) interfaced to a PDZ Europa 20-20 isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK,) analyzed at UC Davis isotopic facility (USA). genus refers to plant genus: acacia and banksia stage refers to successional stage: early and late nematode refers to nematode inoculation: control (no nematodes); bacterial (bacterial feeding nematodes added); plant (root feeding nematodes added) grown refers to plant mixture: alone (plant grown with members of the same species) and both (plant grown in mixture) %C: carbon shoot concentration (%) %N: nitrogen shoot concentration (%) Cg: total grams of carbon in shoot Ng total grams of nitrogen in shoot

iso: isotopic signature of plants, analyzed by an Elementar Vario Micro Cube elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany) interfaced to a PDZ Europa 20-20 isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK,) analyzed at UC Davis isotopic facility (USA). genus refers to plant genus: acacia and banksia stage refers to successional stage: early and late nematode refers to nematode inoculation: control (no nematodes); bacterial (bacterial feeding nematodes added); plant (root feeding nematodes added) grown refers to plant mixture: alone (plant grown with members of the same species) and both (plant grown in mixture) d15N: isotopic nitrogen signature in shoot (deltha15N, at%)

nit: nitrogenase activity was estimated in fresh acacia nodules using the acetylene reduction essay (Hardy, Burns, & Holsten, 1973) species refers to plant species nematode refers to nematode inoculation: control (no nematodes); bacterial (bacterial feeding nematodes added); plant (root feeding nematodes added) grown refers to plant mixture: alone (plant grown with members of the same species) and both (plant grown in mixture) ppm_nod: ethylene produced per nodule (ppm)

nod: number of nodules were counted on freshly harvested roots species refers to plant species nematode refers to nematode inoculation: control (no nematodes); bacterial (bacterial feeding nematodes added); plant (root feeding nematodes added) grown refers to plant mixture: alone (plant grown with members of the same species) and both (plant grown in mixture) Nods: number of nodules per plant

Soil June 2017 dataset

Soil measurements

Measurements taken in the soil.

moist: %: moisture in soil (loss by ignition, 104�, 24h, %water content) nematode refers to nematode inoculation: control (no nematodes); bacterial (bacterial feeding nematodes added); plant (root feeding nematodes added) Plant refers to plant mixture: acacia (acacia only); banksia (banksia alone) and both (acacia and banksia) stage refers to successional stage: early and late

mineral nitrogen in soil (ammonium and nitrate) was obtained through mild extracts (2N KCl) analyzed in a Discrete Multi-Chemistry Analyzer AQ2 (by Seal Analytical, Inc. Mequon, WI., analyzed at HIE, NSW, Australia). nematode refers to nematode inoculation: control (no nematodes); bacterial (bacterial feeding nematodes added); plant (root feeding nematodes added) Plant refers to plant mixture: acacia (acacia only); banksia (banksia alone) and both (acacia and banksia) stage refers to successional stage: early and late

nh4: NH4: ammonium content in soil (mg/L)

no3: NO3: nitrate content in soil (mg/L)

nemas: number of nematodes in soil were extracted in modified wet funnels from soil subsamples (50 g wet soil; Viglierchio and Schmitt, 1983). The total number of nematodes extracted per pot was then counted under dissecting microscope (Olympus, SZX10). nematode refers to nematode inoculation: control (no nematodes); bacterial (bacterial feeding nematodes added); plant (root feeding nematodes added) Plant refers to plant mixture: acacia (acacia only); banksia (banksia alone) and both (acacia and banksia) stage refers to successional stage: early and late nemg: number of nematodes per gram of soil