Impacts of Wildfire Frequency On Plant Recovery, Soil Properties And Water Storage In Pine Woodlands of North-Central Portugal

PurposeIncreasing wildfire frequency in Mediterranean-basin together with drought periods expansion could affect plant-soil-water dynamics processes. The goal is to assess the effects of wildfire frequency on plant recovery, soil properties, soil moisture content (SMC; %) and effective soil water content (ESWC; %) during the first hydrological year after a 2012 moderate-severity-wildfire.MethodsThis study was conducted in pine woodlands of North-central Portugal affected by 1-, 4-wildfires and unburnt (1975-2012). Soil samples were gathered from plant/bare microsites at top-mid-bottom hillslope positions to determine bulk density, soil texture, soil moisture, soil organic matter content-SOM, pF-curves (available water content-AWC, field capacity-FC, permanent wilting point-PWP) (n=54) during four dry/wet periods. Soil cover, plant recovery and soil water repellency were measured. On the burnt areas 72 sensors daily/seasonal monitored SMC and ESWC at two depths (2.5/7.5 cm) and two microsites (plant/bare). ResultsThe 1 fire hillslopes showed higher plant recovery than the 4 fires hillslopes. SOM was higher in the burnt soils (17-20%) than in the unburnt ones (12-14%). Wildfire frequency: i) increased the water stress for plants and led to both maximum and minimum values of SMC/ESWC, respectively, for the wet-/dry-seasons; ii) reduced the capacity of the soils to retain water (decreased FC/AWC, increased PWP), being more accentuated in bare microsites. ConclusionThe increasing wildfire frequency and the predicted expansion of drought periods promotes lower water availability for plants in the more frequent bare soil patches. The water-stress window of the dry season happened sooner and extended for longer as increasing wildfire frequency.

Plant Recovery after Metal Stress—A Review

Contamination of the environment with metals, their adverse impact on plant performance and transmission to the human food chain through crops and vegetables are important concerns worldwide. Although the literature on metal contamination, toxicity and plant response to this stress factor is quite abundant, there are very limited reports on the phenomenon of plant recovery after metal stress. The present article reviews available literature on the recovery process examined in various plant species, in response to several metals (Al, Cd, Cu, Ni, Pb, Zn), applied at different concentrations and treatment duration. The reviewed studies have been carried out in laboratory conditions. However, it should be highlighted that although metal stress is not as transient as most of other stress factors (e.g., drought, heat, chilling), metal concentration in the soil may still decrease due to, e.g., leaching to lower soil layers or uptake by organisms. Thus, in natural conditions, plants may be subjected to post-metal-stress conditions. The review also discusses the mechanism behind efficient recovery and the impact of post metal stress on future plant performance—possible acquisition of stress memory, adaptation to unfavorable conditions and cross-tolerance towards other stress factors.

Effect of Florpyrauxifen-benzyl Formulation and Rate for Waterhyacinth Control in a Mesocosm Setting

Waterhyacinth (Eichhornia crassipes) has been the focus of national legislation efforts and has been listed as noxious, invasive, potentially invasive, or prohibited by at least seven U.S. states. Auxinic herbicides are one of the most effective control methods labeled for use in aquatic sites. In the U.S., florpyrauxifen-benzyl, a synthetic auxin, was recently (2018) registered for use in aquatic sites, but limited information has been published on efficacy, especially differences between the two formulations. Therefore, the purpose of this work was to evaluate two formulations of florpyrauxifen-benzyl – suspension concentrate (SC) and emulsifiable concentrate (EC) – at three rates each (5.9, 11.8, and 23.6 g a.i. ha-1) for control of waterhyacinth under outdoor and greenhouse conditions. All rates of each florpyrauxifen-benzyl formulation reduced waterhyacinth biomass by 90 to 100% when compared to non-treated plants at five weeks after treatment (WAT). Based on plant recovery in the outdoor trial, there was some evidence that the lowest rate (5.9 g a.i. ha-1) of florpyrauxifen-benzyl SC and EC may not be as efficacious at reducing waterhyacinth biomass as the SC and EC formulations when applied at 11.8 and 23.6 g a.i. ha-1. Future work should evaluate the florpyrauxifen-benzyl rates tested in this research against waterhyacinth in field trials and/or an operational setting to confirm findings.