Increased Soil Frost Versus Summer Drought as Drivers of Plant Biomass Responses To Reduced Precipitation: Results from A Globally-Coordinated Field Experiment

Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze-thaw cycles. Therefore, in addition to the effects of reduced precipitation on plants via drought, freezing damage to overwintering plant tissues at or below the soil surface could further affect plant productivity and relative species abundances during the growing season. We examined the effects of both reduced rainfall (via rain-out shelters) and reduced snow cover (via snow removal) at 13 sites globally (primarily grasslands) within the framework of the International Drought Experiment, a coordinated distributed experiment. Plant cover was estimated at the species level and aboveground biomass was quantified at the functional group level. Among sites, we observed a negative correlation between the snow removal effect on minimum soil temperature and plant biomass production the next growing season. Three sites exhibited significant rain-out shelter effects on plant productivity, but there was no correlation among sites between the rain-out shelter effect on minimum soil moisture and plant biomass. There was no interaction between snow removal and rain-out shelters for plant biomass, although these two factors only exhibited significant effects simultaneously for a single site. Overall, our results reveal that reduced snowfall, when it decreases minimum soil temperatures, can be an important component of the total effect of reduced precipitation on plant productivity

Data from: Short-term microbial effects of a large-scale mine-tailing storage facility collapse on the local natural environment

We investigated the impacts of the Mount Polley tailings impoundment failure on chemical, physical, and microbial properties of substrates within the affected watershed, comprised of 70 hectares of riparian wetlands and 40 km of stream and lake shore. We established a biomonitoring network in October of 2014, two months following the disturbance, and evaluated riparian and wetland substrates for microbial community composition and function via 16S and full metagenome sequencing. A total of 234 samples were collected from substrates at 3 depths and 1,650,752 sequences were recorded in a geodatabase framework. These data revealed a wealth of information regarding watershed-scale distribution of microbial community members, as well as community composition, structure, and response to disturbance. Substrates associated with the impact zone were distinct chemically as indicated by elevated pH, nitrate, and sulphate. The microbial community exhibited elevated metabolic capacity for selenate and sulfate reduction and an abundance of chemolithoautotrophs in the Thiobacillus thiophilus/T. denitrificans/T. thioparus clade that may contribute to nitrate attenuation within the affected watershed. The most impacted area (a 6km stream connecting two lakes) exhibited 30% lower microbial diversity relative to the remaining sites. The tailings impoundment failure at Mount Polley Mine has provided a unique opportunity to evaluate functional and compositional diversity soon after a major catastrophic disturbance to assess metabolic potential for ecosystem recovery

Short-term microbial effects of a large-scale mine-tailing storage facility collapse on the local natural environment

<div><p>We investigated the impacts of the Mount Polley tailings impoundment failure on chemical, physical, and microbial properties of substrates within the affected watershed, comprised of 70 hectares of riparian wetlands and 40 km of stream and lake shore. We established a biomonitoring network in October of 2014, two months following the disturbance, and evaluated riparian and wetland substrates for microbial community composition and function via 16S and full metagenome sequencing. A total of 234 samples were collected from substrates at 3 depths and 1,650,752 sequences were recorded in a geodatabase framework. These data revealed a wealth of information regarding watershed-scale distribution of microbial community members, as well as community composition, structure, and response to disturbance. Substrates associated with the impact zone were distinct chemically as indicated by elevated pH, nitrate, and sulphate. The microbial community exhibited elevated metabolic capacity for selenate and sulfate reduction and an abundance of chemolithoautotrophs in the <i>Thiobacillus thiophilus/T</i>. <i>denitrificans/T</i>. <i>thioparus</i> clade that may contribute to nitrate attenuation within the affected watershed. The most impacted area (a 6 km stream connecting two lakes) exhibited 30% lower microbial diversity relative to the remaining sites. The tailings impoundment failure at Mount Polley Mine has provided a unique opportunity to evaluate functional and compositional diversity soon after a major catastrophic disturbance to assess metabolic potential for ecosystem recovery.</p></div

Detrended correspondence analysis depicting Polley Lake community dissimilarity based on reconstructed OTUs for each of the three sample types.

<p>Bubble size varies in proportion to relative abundance of each major taxonomic group (Phylum) listed to the right. Bubble color highlights the three sample types collected (green = surficial, black = deep, and blue = sediment).</p

Samples were collected to represent the types of habitats affected by the spill including.

<p> (A) organic-rich soil supporting a diverse wetland community including living, senesced and decayed vegetation, (B) organic-dominated lakeshore lacking extensive living vegetation, (C) mineral lakeshore including exposed native bedrock, cobbles, clays or sands, (D) native substrates with evidence of tailings deposition (visible accretions of tailings sediments intermingled with native substrate or coating of plant stems/leaves with fine tailings), (E) burial of native substrate in coarse tailings sands, (F) replacement of native substrate with a mixture of fine tailings and sands. The table to the right presents mean surface material estimates (n = 5, 1 m² quadrats) for sample sites with habitat classification (matching colors from figure to the left).</p

Ordination plots comparing.

<p>(A) the microbial population structures of sites in Bootjack Lake (BJL) and Hazeltine Creek (HAZ) (symbol shapes reflect layers from which samples were collected), (B) the surface layer microbial population structures among the lakes and Hazeltine Creek, (C) the deep layer microbial population structures from the different lakes and Hazeltine Creek, and (D) the sediment layer microbial population structures from the lakes and Hazeltine Creek. Sites on Polley Lake (brown symbols) closest to the impoundment are labeled with their site numbers.</p

An indicator species analysis was conducted to further facilitate exploration of the microbial community database.

<p>Bars represent percent contribution to total recovered DNA that was attributable to each of a number of phyla that maximize contrasts amongst the four study systems.</p