Scientists and natural resource managers use bioindicators for overcoming the limitations of instrument-based monitoring networks. Low sampling costs make lichen bioindicators an invaluable tool for detecting finer scaled patterns in air quality than can be detected using instruments. Between 1989 and 2012, three Forest Service programs collected more than 8,300 surveys of epiphytic lichen communities, creating one of the largest systematically sampled lichen datasets in the world. More than 90 studies use these data as a baseline for tracking air quality, climate, and other changes on forest land in the United States. The national Forest Inventory and Analysis (FIA) lichen database (beta) unites, for the first time, all lichen surveys into one set of consistent, linkable tables. We include data for a third of the 5,483 surveys conducted by the national forest inventory programs (Forest Health Monitoring and FIA that are not publically available elsewhere). We also include an additional 2,958 regional surveys collected by the Forest Service’s Air Resources Management program in Alaska, Oregon, and Washington. Advances in lichen taxonomy over the 23 years covered by the database led to the description of many new species, name changes, and revisions of species concepts. We provide two reference tables to help users “reconcile” names to maintain continuity within datasets spanning different timespans. We also provide a comprehensive, user-friendly “Atlas” dataset with fully reconciled names according to taxonomic concepts used by the FIA program. We included the most commonly used environmental variables in bioindicator studies, which were gathered across various Forest Service databases and unpublished sources. This user guide documents the content of each database table and provides essential background information for building custom datasets, including linking with external databases that house additional data for lichen survey locations. Although the lichen data are most often used for air quality and climate biomonitoring projects, they are suitable for a wide range of ecological and taxonomic studies.
Drought, ozone (O3), and nitrogen deposition (N) alter foliar pigments and tree crown structure that may be remotely detectable. Remote sensing tools are needed that pre-emptively identify trees susceptible to environmental stresses could inform forest managers in advance of tree mortality risk. Jeffrey pine, a component of the economically important and widespread western yellow pine in North America was investigated in the southern Sierra Nevada. Transpiration of mature trees differed by 20% between microsites with adequate (mesic (M)) vs. limited (xeric (X)) water availability as described in a previous study. In this study, in-the-crown morphological traits (needle chlorosis, branchlet diameter, and frequency of needle defoliators and dwarf mistletoe) were significantly correlated with aerially detected, sub-crown spectral traits (upper crown NDVI, high resolution (R), near-infrared (NIR) Scalar (inverse of NDVI) and THERM Δ, and the difference between upper and mid crown temperature). A classification tree model sorted trees into X and M microsites with THERM Δ alone (20% error), which was partially validated at a second site with only mesic trees (2% error). Random forest separated M and X site trees with additional spectra (17% error). Imagery taken once, from an aerial platform with sub-crown resolution, under the challenge of drought stress, was effective in identifying droughted trees within the context of other environmental stresses.
Although nitrogen deposition and tropospheric ozone have impacted California forests for decades, broad scale studies of these impacts on forest growth and mortality are lacking. Because of the summer-dry climate over most of the state, forest responses to air pollution are expected to differ from more mesic climates. In this study, data from US Forest Service Forest Inventory and Analysis (FIA) permanent (remeasured) plots were combined with modelled atmospheric N and S deposition and an ozone exposure index to evaluate tree growth and mortality responses in California. Seven of 18 species exhibited significantly greater carbon increment (CI) in tree boles as N deposition increased, though the magnitude of the effect was quite small in most California forests. However, increases in CI were substantial in the coastal ecosections of central and northern California where precipitation and fog exposure are greatest. Redwood (Sequoia sempervirens (D. Don) Endl.) trees exhibited the strongest CI response to N deposition. Our model results imply a mean CI increase of 4.2 kg ha−1 yr−1 of C per kg ha−1 yr−1 of N deposition statewide versus 13.6 in the Central and Northern California Coast ecosections, where > 50% of the trees are redwood or tanoak (Lithocarpus densiflorus (Hook. & Arn.) Rehd.). Increased carbon sequestration rates in response to N deposition in these California coastal regions were similar to increases reported for Europe and global estimates. Nitrogen and S deposition significantly increased the odds of top damage and trees with crown damage exhibited higher mortality, although the effect was small. Elevated ozone exposure was associated with significantly larger rates of overall tree growth. However, for ozone-sensitive ponderosa pine at moderate ozone levels (ozone index values of ca. 20–30 ppb) and moderately-elevated N deposition (15–25 kg ha−1 hr−1), CI begins to decline, before increasing at higher pollution levels, presumably because of the fertilizing effect of N deposition; although data are limited for these more polluted conditions. Sulfur deposition in California forests was low, ranging from 0.3 to 3.1 kg ha−1 yr−1, but was associated with positive growth response in seven coniferous species. The combined effect of N and S deposition and ozone exposure statewide is a net increase in bole CI. However, aridity reduces the stimulatory growth effect of N deposition, and alters the threshold, capacity and sometimes the direction (e.g., S deposition) of the CI response to deposition, factors that need to be considered in global change models.
Five lichen species were evaluated as element-content pollution bioindicators for a pilot study in Wisconsin and adjacent U.S. states, using data for 20 elements. Goodquality elemental data for aluminum, cobalt, chromium, copper, iron, nitrogen, and sulfur—mostly from nonspecialist U.S. Forest Service Forest Inventory and Analysis staff collections with extensively documented protocols—clearly indicated a site pollution load in the project area. The percentage of nearby land in forest was the strongest predictor for sample collection at study sites of the two most frequent species; such knowledge facilitates improved broad applications. Improved protocols and three lichen species were recommended for implementation as elemental bioindicators in the north-central United States; species were also recommended for three other Eastern U.S. regions. The three reccomended species are Evernia mesomorpha Nyl.; Flavoparmelia caperata (L.) Hale, and the combined Physcia aipolia (Ehrh. ex Humb.) Fürnr var. aipolia and P. stellaris (L.) Nyl.
Longleaf pine (Pinus palustris P. Mill) survival and growth, net nitrogen mineralization, and soil microbial biomass, were evaluated after four growing seasons in a Florida wet flatwoods site following chemical vegetation control during the first year or second year after planting, or during both years. The four herbicide treatments included sulfometuron methyl at 0.26 ai kg ha-1, hexazinone (0.56 ai kg ha-1), sulfometuron (0.26 ai kg ha-1) plus hexazinone (0.56 ai kg ha-1) mix, and imazapyr at 0.21 ai kg ha-1. Imazapyr was the only treatment to significantly improve growth over the control in a single application. Consecutive annual applications of imazapyr and hexazinone on seedlings also improved growth rates compared to the control. Sulfometuron methyl-treated pine trees had lower survival rates and were smaller than pines growing in the control plots after a single application. The survival and growth rates of imazapyr-treated seedlings were improved when the chemical was applied during the second growing season after planting, instead of the first year. Imazapyr and hexazinone applications increased net nitrogen mineralization rates, but imazapyr was the only treatment to increase ammonification; compared to the control. Microbial and fungal biomass carbon showed no differences between treatments. The results did show that microbial biomass significantly increased with two consecutive years of herbicide applications over a single application. Imazapyr applied during the second growing season proved to be the best treatment for improving pine growth, controlling competitive vegetation, minimizing pine mortality, and to remain effective when soils are saturated.
This paper examines the issue of radionuclide resuspension from wildland fires in areas contaminated by the Chernobyl Nuclear Power Plant explosion in 1986. This work originated from a scientific exchange among scientists from the USDA Forest Service, Ukraine and Belarus that was organized to assess science and technology gaps related to wildfire risk management. A wildfire risk modeling system was developed to predict likely hotspots for large fires and where wildfire ignitions will most likely result in significant radionuclide (Cesium, 137Cs) resuspension. The system was also designed to examine the effect of fuel breaks in terms of reducing both burn probability and resuspension. Results showed substantial spatial variation in fire likelihood, size, intensity, and potential resuspension within the contaminated areas. The potential for a large wildfire and resuspension was highest in the Belorussian Polesie Reserve, but the likelihood of such an event was higher in the Ukrainian Chernobyl Exclusion Zone due to a higher predicted probability of ignition. Fuel breaks were most effective in terms of reducing potential resuspension when located near areas that had both high ignition probability and high levels of 137Cs contamination. Simulation outputs highlighted how human activities shape the fire regime and likelihood of a large fire in the contaminated areas. We discuss how the results can be used to develop a fire management strategy that integrates ignition prevention, detection, effective suppression response, and fuel breaks. Specifically, the modeling system can now be used to explore a wide range of fire management scenarios for the contaminated areas and contribute to a comprehensive fire management strategy that targets specific drivers of fire by leveraging multiple tools including fire prevention and long-term fuel management. Wildfire-caused emissions of radionuclides in Belarus, Ukraine, and Russia are a socio-ecological problem that will require defragmenting existing risk management systems and leveraging multiple short- and long-term mitigation measures.
Atmospheric nitrogen and sulfur pollution increased over much of the United States during the twentieth century from fossil fuel combustion and industrial agriculture. Despite recent declines, nitrogen and sulfur deposition continue to affect many plant communities in the United States, although which species are at risk remains uncertain. We used species composition data from >14,000 survey sites across the contiguous United States to evaluate the association between nitrogen and sulfur deposition and the probability of occurrence for 348 herbaceous species. We found that the probability of occurrence for 70% of species was negatively associated with nitrogen or sulfur deposition somewhere in the contiguous United States (56% for N, 51% for S). Of the species, 15% and 51% potentially decreased at all nitrogen and sulfur deposition rates, respectively, suggesting thresholds below the minimum deposition they receive. Although more species potentially increased than decreased with nitrogen deposition, increasers tended to be introduced and decreasers tended to be higher-value native species. More vulnerable species tended to be shorter with lower tissue nitrogen and magnesium. These relationships constitute predictive equations to estimate critical loads. These results demonstrate that many herbaceous species may be at risk from atmospheric deposition and can inform improvements to air quality policies in the United States and globally.