DOI: 10.5061/dryad.xpnvx0kpk
title: Interacting effects of invasion and soil microbes on Douglas-fir seedling response to drought

description: Global change is affecting native species and communities through multiple
 anthropogenic drivers, which likely interact, complicating our ability to
 predict the net effects of global change. In the Pacific
 Northwest region (USA), *Cytisus scoparius *(L.) Link (Scotch
 broom) invasion has dramatically altered many ecosystems, including
 post-harvest timber lands. Simultaneously, the intensity of summer drought
 conditions associated with climate change is making successful
 reforestation increasingly difficult. We investigated how Douglas-fir
 (Pseudotsuga menziesii (Mirb.) Franco var. menziesii)
 responds to the multiple stressors of drought and *Cytisus *invasion. We
 further evaluated whether the soil microbial community, including
 mycorrhizal fungi, ameliorates or exacerbates Douglas-firs' response
 to drought and Cytisus competition. Drought and the presence of the
 invader both increased stress (measured by chlorophyll fluorescence) and
 decreased survival of Douglas-fir seedlings, and their combined effects on
 stress were more than additive. Douglas-fir grew bigger in live
 than in sterile soil, but this effect was strongly reduced in the presence
 of Cytisus; we also found that mycorrhizal colonization was reduced in the
 presence of the invader. Surprisingly, however, Douglas-fir
 survival in live soil was lower than in sterile soil, especially in the
 presence of Cytisus. Our results suggest that the impact of drought on
 Douglas-fir seedlings is likely to be exacerbated by the invasion of
 Cytisus. Our results further suggest that in a warming climate, the
 presence of impactful invasive species, such as Cytisus, can affect
 whether soil microbes have a net positive or negative effect on native
 plant performance. Our results illustrate the value of studying multiple
 stressors simultaneously to understand their interactions and combined
 impacts on native species.
description: # Interacting effects of invasion and soil microbes on Douglas-fir
 seedling response to drought
 [https://doi.org/10.5061/dryad.xpnvx0kpk](https://doi.org/10.5061/dryad.xpnvx0kpk) # Description of the data and file structure Multiple_Stressors_Data.xlsx contains a separate tab for each response variable. The response variables evaluated in the study were: Douglas-fir survival (tab in Excel file is called "Survival") Douglas-fir biomass (tab in Excel file is called "Biomass") Stress Response measured as FVFM (tab in Excel file is called "FVFM") Proportion of roots colonized by ectomycorrhizal fungi, abbreviated as EMF (tab in Excel file is called "EMF") Below, the data in each tab is described. ## The Survival tab includes the following data: siteId = Soils used in this study were collected from 3 different field sites. The sites are called 1, 2, and 3. soil = Soils in this study were either live or sterilized (autoclaved 2x). Live soils are entered as "L", and sterilized soils are entered as "S". inv = Scotch broom (Cytisus scoparius) invasion was a treatment in this study. Invaded replicates are entered as "Br" and uninvaded replicates are entered as "Un" drought_trt = Drought was a treatment in this experiment. Replicates entered as "drought" received the drought treatment, and replicates entered as "wet" did not receive the drought treatment. block = The greenhouse array contained 10 blocks. For each replicate, the block ID is entered. days_surv = The number of days Douglas-fir survived. Replicates with the value 83 lived to the end of the experiment. censor = censor included in the coxme analysis. A censor value of 1 indicates the plant died, and a value of 0 indicates the plant did not die. death date = the date the replicate was identified as dead ## The FVFM tab includes the following data tagId = the unique identifier for each replicate SiteID = Soils used in this study were collected from 3 different field sites. The sites are called "1", "2", and "3". SoilTrt = Soils in this study were either live or sterilized (autoclaved 2x). Live soils are entered as "L", and sterilized soils are entered as "S". Broom = Scotch broom (Cytisus scoparius) invasion was a treatment in this study. Invaded replicates are entered as "broom," and uninvaded replicates are entered as "uninvaded." DroughtTrt = Drought was a treatment in this experiment. Replicates entered as "drought" received the drought treatment, and replicates entered as "wet" did not receive the drought treatment. block = The greenhouse array contained 10 blocks. Fv/Fm was only measured on replicates in blocks 1-4. For each replicate, the block ID is entered as "1", "2", "3", or "4". Columns G-R are labeled with the number of days after the drought treatment was started that the Fv/Fm measurement was collected. For example, the column labeled "2 days PD" is the measured FvFm value for the replicate 2 days after the drought treatment was applied, "5 days PD" is 5 days after the Drought treatment was applied, and so on. PD is an abbreviation for "post drought". FvFm_summed = the sum of all the Fv/Fm measurements collected for each replicate number_of_times_measured = number of days that FvFm was collected for the replicate FvFm_Score_Initial = The FvFm integrated score is the sum of all Fv/Fm measurement values (i.e., FvFm-summed) of a given replicate, divided by the initial baseline FvFm score (i.e., column labeled 2 days PD) multiplied by the number of times FvFm was measured on the replicate. N/As in the FVFM data indicate missing values. Replicates in block 3 of the day 9 post-drought measurements were not measured. Block 3 was not measured at this time point due to per-dawn time constraints. The other N/As here in the survival data are individual samples that were inadvertently missed at a given time point. ## The Biomass tab includes the following data TagID = the unique identifier for each replicate SiteID = Soils used in this study were collected from 3 different field sites. The sites are called "1", "2", and "3". SoilTrt = Soils in this study were either live or sterilized (autoclaved 2x). Live soils are entered as "live", and sterilized soils are entered as "sterile". Broom_height (cm) Aug 23 2018 = The height of the Scotch broom growing in the replicate on Aug 23 2018 GH_block = The greenhouse array contained 10 blocks. The block the replicate was located in is entered. InvasionTrt = Scotch broom (Cytisus scoparius) invasion was a treatment in this study. Invaded replicates are entered as "broom," and uninvaded replicates are entered as "uninvaded." DroughtTrt = Drought was a treatment in this experiment. Replicates entered as "drought" received the drought treatment, and replicates entered as "wet" did not receive the drought treatment. Below_Biomass = The weight (mg) of the dried root tissue of each Douglas-fir replicate. Below-ground biomass was collected on a subset of plants grown in blocks 5-10. Below-ground biomass was only measured on live plants. Below-ground biomass was not measured on replicates that had received the drought treatment, replicates that were assessed for ectomycorrhizal colonization, or replicates that died during the experiment. Above_Biomass = The weight (mg) of the above-ground plant tissues (stem and needles) of each Douglass-fir replicate. Root/Shoot = The Below_biomass value divided by the Above_Biomass value. Above-ground biomass was only measured on live plants. Above-ground biomass was not measured on replicates that had received the drought treatment. N/As in the biomass data indicate missing values. N/A is included in place of the below-ground biomass values because below-ground biomass was not collected on the same samples that were evaluated for ectomycorrhizal colonization. Similarly, shoot ratios could not be calculated on samples that were assessed for ectomycorrhizal colonization.  ## The EMF tab includes the following columns TagID = the unique identifier for each replicate SiteID = Soils used in this study were collected from 3 different field sites. The sites are identified as "1", "2", and "3". SoilTrt = Soils in this study were either live or sterilized (autoclaved 2x). Live soils are entered as "live", and sterilized soils are entered as "sterile". InvasionTrt = Scotch broom (Cytisus scoparius) invasion was a treatment in this study. Invaded replicates are entered as "broom," and uninvaded replicates are entered as "uninvaded." Broom height (cm) = The height of the Scotch broom growing in the replicate on Aug 23, 2018 DroughtTrt = Drought was a treatment in this experiment. Replicates entered as "drought" received the drought treatment, and replicates entered as "wet" did not receive the drought treatment. EMF was only measured on the replicates that received the "wet" treatment. Block = The greenhouse array contained 10 blocks. Proportion_myco_col = The proportion of roots measured that contained ectomycorrhizal fungi.