Controls on soil carbon sequestration and dynamics: lessons from land-use change

Includes bibliographical references (pages 82-83).Soil carbon (C) dynamics and sequestration are controlled by interactions of chemical, physical and biological factors. These factors include biomass quantity and quality, physical environment and the biota. Management can alter these factors in ways that alter C dynamics. We have focused on a range of managed sites with documented land use change from agriculture or grassland to forest. Our results suggest that interactions of soil type, plant and environment impact soil C sequestration. Above and below ground C storage varied widely across sites. Results were related to plant type and calcium on sandy soils in our Northern sites. Predictors of sequestration were more difficult to detect over the temperature range of 12.4°C in the present study. Accrual of litter under pines in the moist Mississippi site limited C storage in a similar manner to our dry Nebraska site. Pre-planting heterogeneity of agricultural fields such as found in Illinois influences C contents. Manipulation of controls on C sequestration such as species planted or amelioration of soil quality before planting within managed sites could increase soil C to provide gains in terrestrial C storage. Cost effective management would also improve soil C pools positively affecting soil fertility and site productivity.Publisher version: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3380508

Soil organic carbon pool changes following land-use conversions

Includes bibliographical references (pages 1131-1132).Carbon (C) can be sequestered in the mineral soil after the conversion of intensively cropped agricultural fields to more extensive land uses such as afforested and natural succession ecosystems. Three land-use treatments from the long-term ecological research site at Kellogg biological station in Michigan were compared with a nearby deciduous forest. Treatments included a conventionally tilled cropland, a former cropland afforested with poplar for 10 years and an old field (10 years) succession. We used soil aggregate and soil organic matter fractionation techniques to isolate C pools that (1) have a high potential for C storage and (2) accumulate C at a fast rate during afforestation or succession. These fractions could serve as sensitive indicators for the total change in C content due to land-use changes. At the mineral soil surface (0–7 cm), afforesting significantly increased soil aggregation to levels similar to native forest. However, surface soil (0–7 cm) C did not follow this trend: soil C of the native forest site (22.9 t C ha-1) was still significantly greater than the afforested (12.6 t C ha-1) and succession (15.4 t C ha-1) treatments. However, when the 0–50 cm soil layer was considered, no differences in total soil C were observed between the cropland and the poplar afforested system, while the successional system increased total soil C (0–50 cm) at a rate of 0.786 t C ha-1 yr-1. Afforested soils sequestered C mainly in the fine intra-aggregate particulate organic matter (POM) (53–250 μm), whereas the successional soils sequestered C preferentially in the mineral-associated organic matter and fine intra-aggregate POM C pools

The role of soil characteristics on temperature sensitivity of soil organic matter

The uncertainty associated with how projected climate change will affect global C cycling could have a large impact on predictions of soil C stocks. The purpose of our study was to determine how various soil decomposition and chemistry characteristics relate to soil organic matter (SOM) temperature sensitivity. We accomplished this objective using long-term soil incubations at three temperatures (15, 25, and 35°C) and pyrolysis molecular beam mass spectrometry (py-MBMS) on 12 soils from 6 sites along a mean annual temperature (MAT) gradient (2–25.6°C). The Q10 values calculated from the CO2 respired during a long-term incubation using the Q10-q method showed decomposition of the more resistant fraction to be more temperature sensitive with a Q10-q of 1.95 ± 0.08 for the labile fraction and a Q10-q of 3.33 ± 0.04 for the more resistant fraction. We compared the fit of soil respiration data using a two-pool model (active and slow) with first-order kinetics with a three-pool model and found that the two and three-pool models statistically fit the data equally well. The three-pool model changed the size and rate constant for the more resistant pool. The size of the active pool in these soils, calculated using the two-pool model, increased with incubation temperature and ranged from 0.1 to 14.0% of initial soil organic C. Sites with an intermediate MAT and lowest C/N ratio had the largest active pool. Pyrolysis molecular beam mass spectrometry showed declines in carbohydrates with conversion from grassland to wheat cultivation and a greater amount of protected carbohydrates in allophanic soils which may have lead to differences found between the total amount of CO2 respired, the size of the active pool, and the Q10-q values of the soils

Impacts of elevated CO2 concentration on the productivity and surface energy budget of the soybean and maize agroecosystem in the Midwest USA

The physiological response of vegetation to increasing atmospheric carbon dioxide concentration ([CO2]) modifies productivity and surface energy and water fluxes. Quantifying this response is required for assessments of future climate change. Many global climate models account for this response; however, significant uncertainty remains in model simulations of this vegetation response and its impacts. Data from in situ field experiments provide evidence that previous modeling studies may have overestimated the increase in productivity at elevated [CO2], and the impact on large-scale water cycling is largely unknown. We parameterized the Agro-IBIS dynamic global vegetation model with observations from the SoyFACE experiment to simulate the response of soybean and maize to an increase in [CO2] from 375 ppm to 550 ppm. The two key model parameters that were found to vary with [CO2] were the maximum carboxylation rate of photosynthesis and specific leaf area. Tests of the model that used SoyFACE parameter values showed a good fit to site-level data for all variables except latent heat flux over soybean and sensible heat flux over both crops. Simulations driven with historic climate data over the central USA showed that increased [CO2] resulted in decreased latent heat flux and increased sensible heat flux from both crops when averaged over 30 years. Thirty-year average soybean yield increased everywhere (ca. 10%); however, there was no increase in maize yield except during dry years. Without accounting for CO2effects on the maximum carboxylation rate of photosynthesis and specific leaf area, soybean simulations at 550 ppm overestimated leaf area and yield. Our results highlight important model parameter values that, if not modified in other models, could result in biases when projecting future crop–climate–water relationships

Evaluation of carbon accrual in afforested agricultural soils

Includes bibliographical references (pages 1154-1156).Afforestation of agricultural lands can provide economically and environmentally realistic C storage to mitigate for elevated CO2 until other actions such as reduced fossil fuel use can be taken. Soil carbon sequestration following afforestation of agricultural land ranges from losses to substantial annual gains. The present understanding of the controlling factors is inadequate for understanding ecosystem dynamics, modeling global change and for policy decision-makers. Our study found that planting agricultural soils to deciduous forests resulted in ecosystem C accumulations of 2.4 Mg C ha-1 yr-1 and soil accumulations of 0.35 Mg C ha-1 yr-1. Planting to conifers showed an average ecosystem sequestration of 2.5 and 0.26 Mg C ha-1 yr-1 in the soils but showed greater field to field variability than when planted to deciduous forest. Path analysis showed that Ca was positively related to soil C accumulations for both conifers and deciduous afforested sites and played a significant role in soil C accumulations in these sites. Soil N increases were closely related to C accumulation and were two times greater than could be explained by system N inputs from atmospheric deposition and natural sources. Our results suggest that the addition of Ca to afforested sites, especially conifers, may be an economical means to enhance soil C sequestration even if it does not result in increasing C in aboveground pools. The mechanism of N accumulation in these aggrading stands needs further investigation

Psychological literacy and applied psychology in undergraduate education

Psychological literacy for the 21st century posits both real and virtual resource options for "applied" psychology at the interface of psychology education and graduate attribute-targeted student learning outcomes (SLOs). Psychological literacy encapsulates the common graduate attributes or capabilities that students should acquire while undertaking a major in psychology, as exemplified by guidelines and lists of SLOs delineated by many national psychology organizations. Application involves purposefully applying the basic capabilities to new problems or in new situations, usually in an experiential and active manner. In this chapter, we briefly consider the background to the issue of"applied" psychology in undergraduate (UG) education, and then give some concrete examples of how "applied" psychology learning and teaching (L&T) strategies can be implemented to support the development of psychological literacy in our students

Resiliency in the Age of COVID-19: A Policy Toolkit

Twenty-nine LBJ School authors have come together to craft interdisciplinary and resilience-based policy solutions in one toolkit called Resiliency in the Age of COVID-19. In 18 articles that span public management, climate change, economic development, national security and more, LBJ School policy authors provide a forward-thinking lens on what went wrong and what leadership, public policies and initiatives it will take to fix the system flaws exposed by the pandemic. Published during the LBJ School’s 50th anniversary year, the toolkit also provides a snapshot of the school’s depth and breadth of policy and research engagement at this moment in time.Public Affair