The Vegetative Composition of a Beech-Maple Climax Forest in the Glaciated Plateau of Northeastern Ohio

Author Institution: Department of Biological Sciences, University School, Shaker Heights, OhioSurvey was made of a beech-maple forest by the quarter point method during August, 1968. The forest is located on a mesic, level upland of the glaciated Allegheny Plateau in eastern Cuyahoga County, Ohio, in the Chagrin River drainage basin. Geologically the upland is underlain by Mississippian formations capped by a thin cover of till, in which soils of the Ellsworth soil catenathe Rittman and Wadsworth silt loamsare developed. The dominant plant species in this forest are American beech and sugar maple, which together comprise 68% of the trees recorded and have a total combined importance value of 62%. Red oak, red maple, and cucumbertree are important secondary dominants, but white ash and tuliptree are of little significance in the woodland composition. A greater overall abundance of secondary-associate mixed-mesophytic species than is normally found in such forests occurs. This composition supports the concept of a poly climax beechmaple association and is suggested to be a result of past selective lumbering and a variation in topography and soils. Although there is some evidence of past selective lumbering, the forest appears to be in an essentially undisturbed, virgin state. It has been partially destroyed as the forest is now part of a tract of land developed as a new secondary school campus

Natural and managed soil structure: On the fragile scaffolding for soil functioning

Soil structure in natural systems is a product of complex interactions between biological activity, climate and soil minerals that promote aggregation and accumulation of biopores. In arable lands, the management of soil structure often requires the mechanical fragmentation of hardened soil to improve seedbed, control weeds and bury plant residue. Despite difficulties in defining and quantifying soil structure, its critical role is evidenced by loss of productivity when natural structure is perturbed (e.g. compaction) and the long history of tillage in agriculture. To overcome persistent ambiguities among scientific disciplines regarding definition and function of soil structure, we propose a framework for distinguishing managed and natural soil structure based on their different formation processes and functions. Natural soil structure preserves ecological order and legacy that promotes biopore reuse, stabilizes foodwebs and protects soil organic carbon (SOC). The contribution of net primary productivity of natural lands to soil structure forming processes makes it a useful (surrogate) metric of soil structure. The benefits of managed soil structure for crops are quantified indirectly via comparisons with no-till farming under similar conditions. The levels and trends of SOC are useful metrics for the status of natural and managed soil structure. The systematic consideration of soil structure state in natural and arable lands using suitable metrics is a prerequisite for rational decisions related to land management and ensuring sustainable functioning of a fragile and central resource such as soil

Elevated CO2 increases root exudation from loblolly pine (Pinus taeda L.) seedlings as an N-mediated response

The degree to which forest ecosystems provide a long-term sink for increasing atmospheric CO2 depends upon the capacity of trees to increase the availability of growth-limiting resources. It has been widely speculated that trees exposed to CO2 enrichment may increase the release of root exudates to soil as a mechanism to stimulate microbes to enhance nutrient availability. As a first test to examine how the atmospheric CO2 and nitrogen availability affect the rates of root exudation, we performed two experiments in which the exudates were collected from loblolly pine (Pinus taeda L.) seedlings that were grown in controlled growth chambers under low and high CO2 and at low and high rates of N supply. Despite the differences in experimental design between the two studies, plants grown at high CO2 were larger, and thus whole plant exudation rates were higher under elevated CO2 (P = 0.019), but the magnitude of this response depended on the N level in both studies. Seedlings increased mass-specific exudation rates in response to elevated CO2 in both experiments, but only at low N supply. Moreover, N supply had a greater impact on the exudation rates than did CO2, with mass-specific exudation rates significantly greater (98% and 69% in Experiments 1 and 2, respectively) in the seedlings grown at low N supply relative to high N supply. These results provide preliminary evidence that loblolly pines alter exudation rates in response to both CO2 concentration and N supply, and support the hypothesis that increased C allocation to root exudates may be a mechanism by which trees could delay progressive N limitation in forested ecosystems

Rising CO2, Climate Change, and Public Health: Exploring the Links to Plant Biology

Background: Although the issue of anthropogenic climate forcing and public health is widely recognized, one fundamental aspect has remained underappreciated: the impact of climatic change on plant biology and the well-being of human systems. Objectives: We aimed to critically evaluate the extant and probable links between plant function and human health, drawing on the pertinent literature. Discussion: Here we provide a number of critical examples that range over various health concerns related to plant biology and climate change, including aerobiology, contact dermatitis, pharmacology, toxicology, and pesticide use. Conclusions: There are a number of clear links among climate change, plant biology, and public health that remain underappreciated by both plant scientists and health care providers. We demonstrate the importance of such links in our understanding of climate change impacts and provide a list of key questions that will help to integrate plant biology into the current paradigm regarding climate change and human health

Long-term CO2 enrichment of a forest ecosystem : implications for forest regeneration and succession

Author Posting. © Ecological Society of America, 2007. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 17 (2007): 1198–1212, doi:10.1890/05-1690.The composition and successional status of a forest affect carbon storage and net ecosystem productivity, yet it remains unclear whether elevated atmospheric carbon dioxide (CO2) will impact rates and trajectories of forest succession. We examined how CO2 enrichment (+200 μL CO2/L air differential) affects forest succession through growth and survivorship of tree seedlings, as part of the Duke Forest free-air CO2 enrichment (FACE) experiment in North Carolina, USA. We planted 2352 seedlings of 14 species in the low light forest understory and determined effects of elevated CO2 on individual plant growth, survival, and total sample biomass accumulation, an integrator of plant growth and survivorship over time, for six years. We used a hierarchical Bayes framework to accommodate the uncertainty associated with the availability of light and the variability in growth among individual plants. We found that most species did not exhibit strong responses to CO2. Ulmus alata (+21%), Quercus alba (+9.5%), and nitrogen-fixing Robinia pseudoacacia (+230%) exhibited greater mean annual relative growth rates under elevated CO2 than under ambient conditions. The effects of CO2 were small relative to variability within populations; however, some species grew better under low light conditions when exposed to elevated CO2 than they did under ambient conditions. These species include shade-intolerant Liriodendron tulipifera and Liquidambar styraciflua, intermediate-tolerant Quercus velutina, and shade-tolerant Acer barbatum, A. rubrum, Prunus serotina,Ulmus alata, and Cercis canadensis. Contrary to our expectation, shade-intolerant trees did not survive better with CO2 enrichment, and population-scale responses to CO2 were influenced by survival probabilities in low light. CO2 enrichment did not increase rates of sample biomass accumulation for most species, but it did stimulate biomass growth of shade-tolerant taxa, particularly Acer barbatum and Ulmus alata. Our data suggest a small CO2 fertilization effect on tree productivity, and the possibility of reduced carbon accumulation rates relative to today's forests due to changes in species composition.This research was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-95ER62083, and by Terrestrial Ecosystems and Global Change (TECO) Grant No. DE-F602-97ER62463

Effects of elevated atmospheric carbon dioxide on amino acid and NH 4 + -N cycling in a temperate pine ecosystem

Rising atmospheric carbon dioxide (CO 2 ) is expected to increase forest productivity, resulting in greater carbon (C) storage in forest ecosystems. Because elevated atmospheric CO 2 does not increase nitrogen (N) use efficiency in many forest tree species, additional N inputs will be required to sustain increased net primary productivity (NPP) under elevated atmospheric CO 2 . We investigated the importance of free amino acids (AAs) as a source for forest N uptake at the Duke Forest Free Air CO 2 Enrichment (FACE) site, comparing its importance with that of better-studied inorganic N sources. Potential proteolytic enzyme activity was monitored seasonally, and individual AA concentrations were measured in organic horizon extracts. Potential free AA production in soils ranged from 190 to 690 nmol N g −1  h −1 and was greater than potential rates of soil NH 4 + production. Because of this high potential rate of organic N production, we determined (1) whether intact AA uptake occurs by Pinus taeda L., the dominant tree species at the FACE site, (2) if the rate of cycling of AAs is comparable with that of ammonium (NH 4 + ), and (3) if atmospheric CO 2 concentration alters the aforementioned N cycling processes. A field experiment using universally labeled ammonium ( 15 NH 4 + ) and alanine ( 13 C 3 H 7 15 NO 2 ) demonstrated that 15 N is more readily taken up by plants and heterotrophic microorganisms as NH 4 + . Pine roots and microbes take up on average 2.4 and two times as much NH 4 + 15 N compared with alanine 15 N 1 week after tracer application. N cycling through soil pools was similar for alanine and NH 4 + , with the greatest 15 N tracer recovery in soil organic matter, followed by microbial biomass, dissolved organic N, extractable NH 4 + , and fine roots. Stoichiometric analyses of 13 C and 15 N uptake demonstrated that both plants and soil microorganisms take up alanine directly, with a 13 C :  15 N ratio of 3.3 : 1 in fine roots and 1.5 : 1 in microbial biomass. Our results suggest that intact AA (alanine) uptake contributes substantially to plant N uptake in loblolly pine forests. However, we found no evidence supporting increased recovery of free AAs in fine roots under elevated CO 2 , suggesting plants will need to acquire additional N via other mechanisms, such as increased root exploration or increased N use efficiency.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73167/1/j.1365-2486.2007.01411.x.pd

The Environmental Justice Dimensions of Climate Change

Nations around the world are considering strategies to mitigate the severe impacts of climate change predicted to occur in the twenty-first century. Many countries, however, lack the wealth, technology, and government institutions to effectively cope with climate change. This study investigates the varying degrees to which developing and developed nations will be exposed to changes in three key variables: temperature, precipitation, and runoff. We use Geographic Information Systems (GIS) analysis to compare current and future climate model predictions on a country level. We then compare our calculations of climate change exposure for each nation to several metrics of political and economic well-being. Our results indicate that the impacts of changes in precipitation and runoff are distributed relatively equally between developed and developing nations. In contrast, we confirm research suggesting that developing nations will be affected far more severely by changes in temperature than developed nations. Our results also suggest that this unequal impact will persist throughout the twenty-first century. Our analysis further indicates that the most significant temperature changes will occur in politically unstable countries, creating an additional motivation for developed countries to actively engage with developing nations on climate mitigation strategies