High‐resolution biogenic and geologic proxies in which one increment or layer is formed per year are crucial to describing natural ranges of environmental variability in Earth's physical and ...biological systems. However, dating controls are necessary to ensure temporal precision and accuracy; simple counts cannot ensure that all layers are placed correctly in time. Originally developed for tree‐ring data, crossdating is the only such procedure that ensures all increments have been assigned the correct calendar year of formation. Here, we use growth‐increment data from two tree species, two marine bivalve species, and a marine fish species to illustrate sensitivity of environmental signals to modest dating error rates. When falsely added or missed increments are induced at one and five percent rates, errors propagate back through time and eliminate high‐frequency variability, climate signals, and evidence of extreme events while incorrectly dating and distorting major disturbances or other low‐frequency processes. Our consecutive Monte Carlo experiments show that inaccuracies begin to accumulate in as little as two decades and can remove all but decadal‐scale processes after as little as two centuries. Real‐world scenarios may have even greater consequence in the absence of crossdating. Given this sensitivity to signal loss, the fundamental tenets of crossdating must be applied to fully resolve environmental signals, a point we underscore as the frontiers of growth‐increment analysis continue to expand into tropical, freshwater, and marine environments.
Urban areas around the world are increasingly investing in networks of urban forests, gardens, and other forms of green infrastructure for their benefits, including enhanced livability, ...sustainability, and climate change mitigation and adaptation. Proactive planning for climate change requires anticipating potential climate change impacts to green infrastructure and adjusting management strategies accordingly. We apply climate change projections for the Midwest US state of Indiana to assess the possible impacts of climate change on common forms of urban green infrastructure and identify management implications. Projected changes in Indiana’s temperature and precipitation could pose numerous management challenges for urban green infrastructure, including water stress, pests, weeds, disease, invasive species, flooding, frost risk, and timing of maintenance. Meeting these challenges will involve managing for key characteristics of resilient systems (e.g., biodiversity, redundancy) as well as more specific strategies addressing particular climate changes (e.g., shifting species compositions, building soil water holding capacity). Climate change also presents opportunities to promote urban green infrastructure. Unlike human built infrastructure, green infrastructure is conducive to grassroots stewardship and governance, relieving climate change-related strains on municipal budgets. Resources for adapting urban green infrastructure to climate change are already being applied to the management of urban green infrastructure, and emerging research will enhance understanding of best management practices.
Global warming and related disturbances, such as drought, water, and heat stress, are causing forest decline resulting in regime shifts. Conventional studies have combined tree-ring width (TRW) and ...the normalized difference vegetation index (NDVI) to reconstruct NDVI values and ignored the influences of mixed land covers. We built an integrated TRW-NDVI model and reconstructed the annual NDVI maps by using 622 Landsat satellite images and tree cores from 15 plots using point-by-point regression. Our model performed well in the study area, as demonstrated by significant reconstructions for 71.14% (p < 0.05) of the area with the exclusion of water and barren areas. The error rate between the reconstructed NDVI using the conventional approach and our approach could reach 10.36%. The 30 m resolution reconstructed NDVI images in the recent 100 years clearly displayed a decrease in vegetation density and detected decades-long regime shifts from 1906 to 2015. Our study site experienced five regime shifts, markedly the 1930s and 1950s, which were megadroughts across North America. With fine resolution maps, regime shifts could be observed annually at the centennial scale. They can also be used to understand how the Yellowstone ecosystem has gradually changed with its ecological legacies in the last century.
The 1988 Yellowstone fire altered the structure of the local forest ecosystem and left large non-recovery areas. This study assessed the pre-fire drivers and post-fire characteristics of the recovery ...and non-recovery areas and examined possible reasons driving non-recovery of the areas post-fire disturbance. Non-recovery and recovery areas were sampled with 44,629 points and 77,501 points, from which attribute values related to topography, climate, and subsequent soil conditions were extracted. We calculated the 1988 Yellowstone fire burn thresholds using the differenced Normalized Burn Ratio (dNBR) and official fire maps. We used a burn severity map from the US Forest Service to calculate the burn severity values. Spatial regressions and Chi-Square tests were applied to determine the statistically significant characteristics of a lack of recovery. The non-recovery areas were found to cover 1005.25 km2. Among 11 variables considered as potential factors driving recovery areas and 13 variables driving non-recovery areas, elevation and maximum temperature were found to have high Variance Inflation Factors (4.73 and 4.72). The results showed that non-recovery areas all experienced severe burns and were located at areas with steeper slopes (13.99°), more precipitation (871.73 mm), higher pre-fire vegetation density (NDVI = 0.38), higher bulk density (750.03 kg/m3), lower soil organic matter (165.61 g/kg), and lower total nitrogen (60.97 mg/L). Chi-square analyses revealed statistically different pre-fire forest species (p < 0.01) and soil order (p < 0.01) in the recovery and non-recovery areas. Although Inceptisols dominated in both recovery and non-recovery areas, however, the composition of Mollisols was higher in the non-recovery areas (14%) compared to the recovery areas (11%). This indicated the ecological memory of the non-recovery site reverting to grassland post-disturbance. Unlike conventional studies only focusing on recovery areas, this study analyzed the non-recovery areas and found the key characteristics that make a landscape not resilient to the 1988 Yellowstone fire. The significant effects of elevation, precipitation, and soil pH on recovery may be significant to the forest management and forest resilience in the post-fire period.
Anthropogenic and climatic stressors have affected the forests of northern Pakistan in recent decades. Several studies have been conducted to understand forest growth and its relation to the changing ...climate in this region, but more work needs to be done to understand this complex environment. In this study, we have collected tree core samples of three conifer species (Pinus wallichiana, Picea smithiana, and Abies pindrow) from three different sites in northern Pakistan to understand their radial growth pattern with the goal of finding a relationship between ring-width and climatic parameters (temperature, precipitation, and drought). A 610-year (AD 1406–2015), a 538-year (AD 1478–2015), and a 306-year (AD 1710–2015) long tree-ring width chronology of Pinus wallichiana, Picea smithiana, and Abies pindrow were developed, respectively, using living trees. The ring-width chronologies of these three species showed a strong positive link with the self-calibrated Palmer Drought Severity Index (scPDSI) rather than precipitation or temperature alone, indicating that soil moisture is the primary limiting climatic factor for the growth of these species in the sampling locations. The chronologies of Pinus wallichiana and Picea smithiana exhibited growth suppressions during AD 1570–1610 and the second half of 17th century while their growth was heightened from AD 1540–1560. We have found the lowest growth in Abies pindrow and Picea smithiana from AD 1900–1920, suggesting dry conditions. All three chronologies have exhibited the most rapid increase in growth during the recent decades, suggesting that this region is experiencing climate change with a strong trend towards wetter conditions.
Fire is a disturbance that serves to maintain the diverse mosaic of vegetation in the Eastern Deciduous Forest. However, our ability to reconstruct fire occurrence from hardwood tree scars still lags ...far behind our expertise in reconstructing fire history from conifers in the western United States. This study examines the fidelity of fire scaring in multiple tree species in the Big Oaks National Wildlife Refuge in Indiana, which is located in the central hardwood region of the Eastern Deciduous Forest. All 15 species, except for red oak, showed evidence of past fires, and most samples recorded multiple fire events. No fire scars were recorded in the latewood of the samples. Most of the fires scars occurred in the earlywood (May) suggesting the dormant season fires are likely associated with fires in March to April before the growing season begins. No synchronous fires were recorded across all sites, but fires occurred in 1981, 1982, 1984, 1985, and 1988 across multiple sites. This suggests that these were larger spreading fires. Establishment pulses were documented in association with fire events in 1981, 1984, and 1995, suggesting that fire may benefit the establishment or root sprouting of some hardwood species. Fourteen of the fifteen species that we sampled preserved fire scars, suggesting that the diverse suite of species in the Eastern Deciduous Forest is a viable sampling pool for examining fire history across this forest type.
Environmental literacy can empower students to make positive changes in their environment. Understanding the rates of environmental literacy in college students of color is particularly important ...because African American, Asian, and indigenous peoples (BIPOC) are most likely to be disproportionately impacted by environmental degradation. We administered a survey with questions regarding environmental literacy to undergraduate students at a comprehensive midwestern university in the fall of 2019 resulting in 2560 participants (about 25% of the student population). An ANOVA comparing environmental literacy summary scores demonstrated that Caucasian respondents had a statistically higher environmental literacy than African American and Native American students but were not statistically different from Asian, native Hawaiian, and mixed-race students, although all scores were low with Caucasian students scoring 39% and African American students scoring 31%. We also found that Caucasian and BIPOC women had a greater concern for the environment (F = 20.675, p < 0.001) and felt that their actions can make a difference following two separate tests (F = 18.916, p < 0.001; F = 19.003, p < 0.001) than men or gender-nonconforming students. Caucasian students have a slightly higher environmental literacy, but the scores overall are low. Women consistently report more concern for the environment and also greater empowerment to make a difference.
Questions
Global climate change is predicted to cause widespread shifts in the distribution and composition of forests, particularly in mountain environments where climate exerts strong controls on ...tree community arrangement. The upslope movement of vegetation has been observed in association with warming temperatures and is especially evident in ecotones—the transition zones between vegetation types. We explored the role of drought and tree mortality on recent changes in high‐elevation forests.
Location
Greater Yellowstone Ecosystem, USA.
Methods
We established 19 forest demography plots along an elevational gradient spanning dominant high‐elevation vegetation types.
Results
Tree establishment dates indicated the upslope movement of Pinus albicaulis (whitebark pine) treeline and ecotone shift from meadow to forest starting in the 1950s. An expansion of the growing season likely contributed to the upward expansion of the treeline. Comparisons between overstory and understory tree composition suggested ongoing succession in the absence of fire at lower elevations, namely the replacement of Pinus contorta (lodgepole pine) by Abies lasiocarpa (subalpine fir). P. contorta seedlings were distributed at higher elevations than overstory trees of the same species, suggesting some potential for upslope movement with warming conditions; P. albicaulis seedlings, conversely, were distributed throughout all elevations of the transect. Significant tree mortality occurred in Pinus spp. and disproportionately affected P. albicaulis, as a result of a regional Dendroctonus ponderosae (mountain pine beetle) outbreak (2008–2012). Mortality events were strongly associated with drier than average conditions 2–3 years prior to tree death.
Conclusion
Rising sensitivity to arid conditions in the mid‐20th century amid already dense, aging forests appears to have increased susceptibility to beetle‐induced mortality during the most recent drought. Tree species in the study area responded individually to global change stressors, which acted on these forests in complex ways and led to both ecotone shifts and stability. This work highlights the interplay between succession, forest disturbances and climate‐related growth responses in driving forest compositional change in subalpine and treeline environments.
We investigated tree species compositional change in subalpine forests of the Greater Yellowstone Ecosystem. Using forest demography and tree‐ring data sampled along an elevational gradient, we show the upslope movement of the Pinus albicaulis (whitebark pine) treeline starting in the 1950s and disproportionate mortality of P. albicaulis relative to Pinus contorta (lodgepole pine). Observed compositional changes were mediated by climate‐related stressors, bark beetle outbreak, and successional processes.
Background
The increase in the frequency and intensity of droughts is pointed out as one of the main factors altering biogeochemical cycles in the Amazon basin. An eco-nutritional approach using ...X-ray fluorescence micro-analysis (µXRF) is proposed to verify the long- and short-term effects of droughts on the growth and xylem nutrient concentrations of
Cedrela fissilis
Vell.
Methods
Fourteen radii were selected from a tree-ring width chronology and X-rayed by Itrax Multiscanner. Profiles of ring width, wood density, and concentrations of aluminum (Al), phosphorus (P), sulfur (S), calcium (Ca), potassium (K), manganese (Mn), iron (Fe) and strontium (Sr) together with Al/Ca, Ca/Mn, K/Ca, Sr/Ca and Mn/S ratios were constructed and correlated with precipitation, temperature, the difference between precipitation and potential evapotranspiration (P-PET) and standardized precipitation–evapotranspiration index (SPEI).
Results
During dry years,
C. fissilis
showed narrower, less dense rings, lower Al, P, S and Ca, and higher K and Fe concentrations (the opposite was found in wet years). Ring width decreased (together with Al, P, S, K, Ca, Mn, Fe, Sr, Al/Ca, K/Ca and Sr/Ca) and wood density increased (together with Ca/Mn and Mn/S), which was associated with an increase in evapotranspiration and temperature over time, mainly since 1990.
Cedrela fissilis
showed a tendency to increase its capacity for resistance, and a recovery and resilience in growth over time associated with responses in Al, Ca, P and S. However, it showed a risk in the capacity for recovery of the pre-drought density values, associated with unsatisfactory responses in Al, Ca, K, Fe and P.
Conclusions
This study is the first attempt to analyze tree-ring nutritional evidences of
C. fissilis
trees to climate sensitivity and resilience to drought, based on long-term data from seasonal moist tropical forests of the Amazon. Our data suggested that
C. fissilis
is undergoing alterations in the concentration, use and redistribution of nutrients associated with increasing wood density and decreasing growth over time, due to the increase of drought frequency in the southern Amazon.
Surface roughness parameters, such as roughness length and displacement height, impact the estimation of surface moisture, and the frontal areas of buildings and trees are two components that ...contribute to surface roughness in urban areas. Research on tree frontal area has not been conducted in urban areas before, and we hope to fill that gap in the literature with this study by using Terrestrial Light Detection and Ranging (LiDAR) data to estimate tree frontal areas in Warren Township, Indianapolis, IN, USA. We first estimated the frontal areas of individual trees based on their morphology, then calibrated a regression model to estimate the tree frontal area in 30 m pixels using parameters derived from LiDAR data and tree inventory data. The parameters included tree crown base area, height, width, conditions, defects, maintenances, genera, and land use. The validation shows that R2 yielded values ranging from 0.84 to 0.88, and RMSEs varied with tree category. The tree categories were identified based on the height and broadness of the canopy, which indicated the degree of resistance to air flow. This type of model can be used to empirically determine local roughness values at the tree-level for any city with a complete tree inventory. With the strong correlation between trees' frontal area and crown base area, this model may also be used to determine local roughness value at 30 m resolution with NLCD (National Land Cover Database) tree canopy cover data as a component. A proper tree categorization according to the vertical air resistance, e.g., height and canopy density, was effective to reduce the RMSE in tree frontal area estimation. Geometric parameters, such as height, crown base height, and crown base area extracted from Airborne LiDAR, which demand less storage and computation capacity, may also be sufficient for tree frontal area estimation in the areas where Terrestrial LiDAR is not available.
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