Estimating Carbon Efficiency of Bioenergy Systems in the Mississippi Alluvial Valley

Due to climate change and energy security concerns, bioenergy products and systems are becoming increasingly important, and Life Cycle Assessment (LCA) can provide a better understanding of their carbon efficiency. In this study, we used a cradle-to-grave LCA to analyze the carbon efficiency of a cottonwood-switchgrass agroforest system grown on agriculturally marginal soils on three sites established in 2009 in the Lower Mississippi Alluvial Valley (LMAV). A complete carbon inventory was done for both the agroforestry bioenergy system and a control cropping system that rotated soybeans and grain sorghum. Three years after establishment, the cottonwood sequestered the highest amount of carbon in dead roots, live roots, and surface residues (3222 kg ha−1) and the switchgrass sequestered the highest amount of carbon in above-ground biomass (4233 kg ha−1). The maximum carbon was emitted (1733 kg ha−1) from the soybean/grain sorghum rotation production system. The carbon emission during production was not statistically different for the bioenergy crops. Carbon emission from both bioenergy crops were significantly different compared to traditional agricultural crops. At the end of the third growing season, cottonwood showed the best performance in the net (6.2) and gross (11.8) ratios of carbon balance. The gross ratio of carbon by switchgrass (11.6) was comparable to cottonwood, but the net ratio was approximately 50% (3.3). The net and gross ratios of carbon balance were positive for the control cropping system as well, 1.2 and 2.2 respectively. Carbon emission from the traditional agricultural production system was at least 234% higher compared to the dedicated bioenergy production system. It was evident that bioenergy crops provide a more environmentally efficient practice in terms of carbon balance than the traditional agricultural practice in the Lower Mississippi alluvial Valley.

Conservation–Protection of Forests for Wildlife in the Mississippi Alluvial Valley

The nearly ubiquitous bottomland hardwood forests that historically dominated the Mississippi Alluvial Valley have been greatly reduced in area. In addition, changes in hydrology and forest management have altered the structure and composition of the remaining forests. To ameliorate the detrimental impact of these changes on silvicolous wildlife, conservation plans have emphasized restoration and reforestation to increase the area of interior (core) forest habitat, while presuming negligible loss of extant forest in this ecoregion. We assessed the conservation–protection status of land within the Mississippi Alluvial Valley because without protection, existing forests are subject to conversion to other uses. We found that only 10% of total land area was currently protected, although 28% of extant forest was in the current conservation estate. For forest patches, we prioritized their need for additional conservation–protection based on benefits to forest bird conservation afforded by forest patch area, geographic location, and hydrologic condition. Based on these criteria, we found that 4712 forest patches warranted conservation–protection, but only 109 of these forest patches met our desired conservation threshold of >2000 ha of core forest that was >250 m from an edge. Overall, 35% of the area of forest patches warranting conservation–protection was protected within the conservation estate. Even so, for those forest patches identified as most in need of conservation–protection, less than 10% of their area was currently protected. The conservation–protection priorities described fill an unmet need for land trusts and other conservation partners pursuing strategic forest protection in support of established bird conservation objectives.

Temporal Trends in Body Condition of Arctic Geese Wintering in the Mississippi Alluvial Valley

Midcontinent populations of arctic nesting geese (hereafter, arctic geese), including greater white-fronted geese Anser albifrons frontalis, lesser snow geese Anser caerulescens caerulescens, and Ross's geese Anser rossii, have increased in abundance and shifted their winter distribution in recent decades. Consequently, the number of arctic geese wintering in the Mississippi Alluvial Valley (MAV) has increased since the 1980s. Stored endogenous nutrients are critically important to the life cycle of arctic geese as the geese use these stored nutrients to complete long-distance migration events, survive harsh winters, and supplement nutrients needed for reproduction. This study tracked temporal changes in body condition of arctic geese during the wintering period. We collected arctic geese from October–February 2015–2016 and 2016–2017 in eastern Arkansas. We used proximate analysis to determine size of lipid and protein stores as an index of body condition. Protein stores were more stable through time than lipids, but we observed a slight increase in all species as winter progressed. Mean lipid stores were dynamic and were highest in November and lowest in February. Greater white-fronted geese arrived earliest to the MAV and experienced an increase in endogenous lipid stores during early winter when high-energy food resources were most abundant. Conversely, snow and Ross's geese arrived to the MAV later and did not appear to increase their lipid stores upon arrival. All three species experienced a decline in stored lipid mass as winter progressed; a combination of factors such as resource depletion, a shift in dietary needs, physiological factors, hunting pressure, and increased energetic demands may have driven the decline. An improved understanding of the role that “nontraditional” wintering grounds exert on the nutrient dynamics of arctic geese may aid in the management of growing and shifting populations.