Plants form belowground associations with mycorrhizal fungi in one of the most common symbioses on Earth. However, few large-scale generalizations exist for the structure and function of mycorrhizal symbioses, as the nature of this relationship varies from mutualistic to parasitic and is largely context-dependent. We announce the public release of MycoDB, a database of 4,010 studies (from 438 unique publications) to aid in multi-factor meta-analyses elucidating the ecological and evolutionary context in which mycorrhizal fungi alter plant productivity. Over 10 years with nearly 80 collaborators, we compiled data on the response of plant biomass to mycorrhizal fungal inoculation, including meta-analysis metrics and 24 additional explanatory variables that describe the biotic and abiotic context of each study. We also include phylogenetic trees for all plants and fungi in the database. To our knowledge, MycoDB is the largest ecological meta-analysis database. We aim to share these data to highlight significant gaps in mycorrhizal research and encourage synthesis to explore the ecological and evolutionary generalities that govern mycorrhizal functioning in ecosystems.

A small but growing number of watershed investment programs in the western United States focus on wildfire risk reduction to municipal water supplies. This paper used return on investment (ROI) analysis to quantify how the amounts and placement of fuel treatment interventions would reduce sediment loading to the Strontia Springs Reservoir in the Upper South Platte River watershed southwest of Denver, Colorado following an extreme fire event. We simulated various extents of fuel mitigation activities under two placement strategies: (a) a strategic treatment prioritization map and (b) accessibility. Potential fire behavior was modeled under each extent and scenario to determine the impact on fire severity, and this was used to estimate expected change in post-fire erosion due to treatments. We found a positive ROI after large storm events when fire mitigation treatments were placed in priority areas with diminishing marginal returns after treating >50-80% of the forested area. While our ROI results should not be used prescriptively they do show that, conditional on severe fire occurrence and precipitation, investments in the Upper South Platte could feasibly lead to positive financial returns based on the reduced costs of dredging sediment from the reservoir. While our analysis showed positive ROI focusing only on post-fire erosion mitigation, it is important to consider multiple benefits in future ROI calculations and increase monitoring and evaluation of these benefits of wildfire fuel reduction investments for different site conditions and climates.

Concerns over wildfire impacts to water supplies have motivated efforts to mitigate risk by reducing forest fuels. Methods to assess fuel treatment effects and prioritise their placement are needed to guide risk mitigation efforts. We present a fuel treatment optimisation model to minimise risk to multiple water supplies based on constraints for treatment feasibility and cost. Risk is quantified as the expected sediment impact costs to water supplies by combining measures of fire likelihood and behaviour, erosion, sediment transport and water supply vulnerability. We demonstrate the model’s utility for prioritising fuel treatments in two large watersheds in Colorado, USA, that are critical for municipal water supply. Our results indicate that wildfire risk to water supplies can be substantially reduced by treating a small portion of the watersheds that have dense, fire-prone forests on steep slopes that drain to water supply infrastructure. Our results also show that the cost of fuel treatments outweighs the expected cost savings from reduced sediment inputs owing to the low probability of fuel treatments encountering wildfire and the high cost of thinning forests. This highlights the need to expand use of more cost-effective treatments, like prescribed fire, and to identify fuel treatment projects that benefit multiple resources.

Stand-replacing natural disturbances in mature forests are traditionally seen as events that cause forests to revert to early stages of succession and maintain species diversity. In some cases, however, such transitions could be an artifact of salvage logging and may increase biotic homogenization. We present initial (two-year) results of a study of the effects of tornado damage and the combined effects of tornado damage and salvage logging on environmental conditions and ground cover plant communities in mixed oak-pine forests in north central Mississippi. Plots were established in salvage-logged areas, adjacent to plots established before the storm in unlogged areas, spanning a gradient of storm damage intensity. Vegetation change directly attributable to tornado damage was driven primarily by a reduction in canopy cover but was not consistent with a transition to an early stage of succession. Although we observed post-storm increases of several disturbance indicators (ruderals), we also observed significant increases in the abundance of a few species indicative of upland forests. Increases in flowering were just as likely to occur in species indicative of forests as in species indicative of open woodlands. Few species declined as a result of the tornado, resulting in a net increase in species richness. Ruderals were very abundant in salvage-logged areas, which contained significantly higher amounts of bare ground and greater variance in soil penetrability than did damaged areas that were not logged. In contrast to unlogged areas severely damaged by the tornado, most upland forest indicators were not abundant in logged areas. Several of the forest and open-woodland indicators that showed increased flowering in damaged areas were absent or sparse in logged areas. Species richness was lower in salvage-logged areas than in adjacent damaged areas but similar to that in undamaged areas. These results suggest that salvage logging prevented positive responses of several forest and open-woodland species to tornado damage. Anthropogenic disturbances such as salvage logging appear to differ fundamentally from stand-level canopy-reducing disturbances in their effects on ground cover vegetation in the forests studied here and are perhaps more appropriately viewed as contributing to biotic homogenization than as events that maintain diversity.

Lemongrass [Cymbopogon flexuosus (Steud.) Wats, (syn. Andropogon nardus var. flexuosus Hack; A. flexuosus Nees)] is one of the most widely grown essential oil plants in the world. Field experiments were conducted at Verona and Poplarville, MS, to evaluate the effects of N (0, 40, 80, and 160 kg N/ha) and S (0, 30, 60, and 90 kg S/ha) on lemongrass biomass productivity, essential oil content, yield, and oil composition. Overall, the essential oil content varied within 0.35 to 0.6% of the dried biomass. The major constituents were geranial (25–53%), neral (20–45%), caryophyllene oxide (1.3–7.2%), and t‐caryophyllene (0.3–2.2%). Biomass yields at Verona ranged from 9486 to 19,375 kg/ha, while oil yields ranged from 30 to 139 kg/ha. Overall, dry weight yields increased with the application of 80 kg N/ha relative to the 0 kg N/ha and with 160 kg of N/ha relative to the 0 and 40 kg N/ha treatments. At Poplarville, biomass yields varied from 8036 to 12,593 kg/ha, while oil yields ranged from 23.5 to 89.5 kg/ha. The application of N at 160 kg/ha at Poplarville increased dry weight yields relative to the N at 0 or 40 kg/ha rates, irrespective of the rate used for S. At Verona, within each S application rate, biomass yields were highest in Harvest 2, lower in Harvest 1, and the lowest in Harvest 3 (regrowth). The combined biomass yields of Harvest 1 and Harvest 3 would be lower, but oil yields would be higher compared to Harvest 2 (single‐harvest system). Lemongrass can be grown as an annual essential oil crop in the southeastern United States, with a potential for dual utilization: essential oil and lignocellulosic material for ethanol production.