Flash talks 2

In a comprehensive review of regional case studies, researchers found

Daniel
Kane
Knob
2:05pm
In a comprehensive review of regional case studies, researchers found that increasing surface soil carbon stocks by just 0.4% globally could offset 20-35% of global greenhouse gas emissions. In addition, increased levels of soil carbon are well correlated to higher net primary productivity, greater stability of agricultural yields, and improved soil water retention. Non-profits and government agencies have begun to look for ways to incentivize managers to transition to land management practices that might increase soil carbon, but monitoring progress of such initiatives is difficult given the extremely high cost of traditional laboratory based methods for measuring soil carbon. We have recently developed a measurement protocol that makes use of low-cost field spectrometers and freely available spatial datasets to estimate soil carbon content at individual sample points. First, we sample soil throughout a given site to capture a range of soil carbon contents using traditional, highly accurate lab-based techniques. Those data are then used to build statistical models relating lab-measured soil carbon levels to the spectral data collected with the field spectrometer. These models are further improved by integrating different data types that may be predictive of soil carbon levels from spatially explicit datasets. After the initial site-specific calibration, carbon content can be determined in the field using only the pocket spectrometer and the previously developed model, dramatically reducing sample collection time and cost and allowing managers to sample more frequently in the future and over broader areas. With these reductions in cost, managers can quantify soil carbon at landscape scales and at more frequent intervals, allowing them to inexpensively monitor soil carbon responses as new management practices are adopted.

Resilient, productive soils are considered necessary

Emily
Oldfield
Knob
2:05pm
Resilient, productive soils are considered necessary to sustainably intensify agriculture to reduce yield gaps while minimizing environmental damage. To conserve and develop productive soils, the need to build up and then maintain high levels of organic matter in soils has received considerable attention. Although soil organic matter (SOM) is considered the key arbiter of soil health, its relationship with yield is contested because of local-scale differences in effect sizes. To facilitate the establishment of predictive targets for SOM levels that maximize yields, we present a global analysis of published studies on SOM (measured as soil organic carbon, SOC) and yield for two staple crops, maize and wheat. We find that as SOC levels increase, so do the yields of both crops. Although yield increases level off at approximately 2% SOC, two thirds of the world's cultivated maize and wheat lands currently have SOC contents of less than 2%. Using globally gridded data to extrapolate the SOM-yield relationship, we estimate that building up SOC to 2% in these lands would increase crop yield averages by 14'18% for maize and 28'46% for wheat, which is 30% of the projected yield gap for maize and 64% of the projected yield gap for wheat. Potential nitrogen (N) fertilizer reductions associated with increasing SOC to 2% amount to 7% and 5% of global N fertilizer inputs across maize and wheat fields, respectively. Our analysis provides a global-level quantitative prediction for relating SOC to crop yields, thereby providing a foundation for building a quantitative soil health policy that can help guide soil management for sustainable intensification.

The rapid expansion of unconventional shale oil & gas development

Mario
Soriano
Knob
2:05pm
The rapid expansion of unconventional shale oil & gas development, made possible by advances in hydraulic fracturing (fracking), has triggered concerns over potential risks it poses to water resources and public health. This is particularly evident in areas of active shale gas extraction where local residents rely heavily on shallow aquifers for drinking water. This research aims to develop a quantitative framework to evaluate the vulnerability of drinking water wells to contamination from unconventional oil & gas development activities. The concept of intrinsic well vulnerability is explored through the application of backwards travel time probability modeling to delineate capture zones and quantify various characteristics of contaminant breakthrough curves at the well. The model can be used in conjunction with measurements of well water quality over time, along with public records of shale gas-related activities to characterize risk. The approach is illustrated in a study site within Susquehanna County, Pennsylvania, a region which has experienced a dramatic increase in shale gas extraction in the last few years, and which is projected to continue to be an area of active expansion of the industry. The well vulnerability concept is proposed as a physically based quantitative tool for policy-making regarding the management of the contamination risks of drinking water wells.

Approximately 20% of tropical forests have experienced some degree of selec

Megan
Sullivan
Knob
2:05pm
Approximately 20% of tropical forests have experienced some degree of selective logging---where individual trees are felled according to pre-defined criteria, rather than the whole forest being clear-felled---between 2000 and 2005. The effects of selective logging can vary widely between forests, logging companies, and across continents. Most research on the effects of selective logging has focused on species diversity: globally, selectively logged forests frequently have lower seedling diversity, higher seedling density, and different seedling composition than old-growth forests. However, what these species do is much less understood. The effects of selective logging on tropical forest structure, function, and processes ultimately determines the ecosystem services that tropical forests provide, including carbon storage, habitat connectivity for animal species, and providing for the livelihoods of local people. Thus, understanding the broader ecological effects of selective logging on tropical forests is crucial to the functional conservation of tropical forests and the human communities that live within and around them. I am developing my dissertation project to study the ecological and socio-economic effects of selective logging in Gabon. Gabon's land is ~85% forested. The forest has remained largely intact due to Gabon's abundant oil reserves, low population density, and lack of transportation infrastructure. However, in the past few decades, the landscape of the forest is rapidly changing. Oil reserves in Gabon are dwindling; and there is an increasing interest in logging, agriculture, and ecotourism. As of 2008, 13 national parks were declared as protected areas, covering ~11% of Gabon's land. As of 2010, ~60% of Gabon's land in is leased to logging companies as logging concessions --- areas of the forest where companies can carry out their logging practices. I am planning my work in the forests near Ebyeng in west-central Gabon. Ebyeng is a cooperatively run village that owns 1,200ha of forest and operates a community forestry program focusing on agroforestry, long-term planning, and working relationships with nearby logging companies.

Traditionally, evolution was thought to operate on protracted scales

A.
Andis
Knob
2:05pm
Traditionally, evolution was thought to operate on protracted scales much longer than the timescales associated with ecological interactions and especially more recent than most anthropogenic effects. However, empirical studies using common garden experiments and reciprocal transplant designs have shown that rapid evolution may be taking place before our eyes. This rapid adaptation would be intriguing enough in an allopatric scenario (in which a physical barrier divides a population), but even more interesting is the finding that rapid adaptive divergence even occurs in sympatric populations on microgeographic scales in the absence of physical barriers. Specifically, it has been shown that wood frog populations inhabiting in Yale Myers Forest may represent two divergent ecotypes, those adapted to warmer ponds with more open canopy and those adapted to colder conditions in closed-canopy ponds. My proposed dissertation work uses population genetics and landscape ecology to understand how these dynamics affect amphibian populations, which is particularly important as human development results in a less forested and warmer future.

Title: A decade and a half of global urban heat islands

Tirthankar
Chakraborty
Knob
2:05pm
Title: A decade and a half of global urban heat islands The urban heat island (UHI) effect refers to the higher temperatures in urban areas, and it is one of the most well known consequences of urbanization on local climate. In the present study, we define a new algorithm to map the daytime and nighttime surface UHIs on a global scale using Google Earth Engine. The diurnal, seasonal, and annual trends in the surface UHIs are characterized using 16 years of satellite data for over 9000 urban clusters. The variability of the surface UHI for different Koppen-Geiger climate zones is determined using a consistent methodology for the first time. We find good agreement between our results and previous studies. The 16-year mean global daytime surface UHI is around 0.71'C (at 1030 LT) and 1'C (at 1330 LT), while the nighttime surface UHI is 0.51'C (at 2230 LT) and 0.42'C (at 0130 LT). Summer surface UHI is larger than winter surface UHI across all climate zones. The annual surface UHI is highest in Continental urban clusters, followed by Tropical, Temperate and Dry. Other than the Dry climate zone, the daytime surface UHI is higher than the nighttime surface UHI. The nighttime and daytime surface UHIs have been increasing from 2012-2015, by around 0.0114'C/decade (at 1330 LT and 0130 LT). When divided by climate zones, the nighttime surface UHI increase is highest in Tropical (0.025'C/decade) and Dry (0.026'C/decade) urban areas.