Thirty-year effects of liming on soil and foliage chemistry and growth of northern hardwoods in Pennsylvania, USA

The longevity of a single 22.4 Mg ha^-1 application of dolomitic limestone at four northern hardwood stands was evaluated over thirty years (1986-2016) to determine whether changes in soils, foliage, and tree growth were sustained on the unglaciated Allegheny Plateau in northern Pennsylvania, USA. In limed plots, soils, sampled to 45-55 cm depth, and sugar maple (<i>Acer saccharum</i> Marsh.) and black cherry (<i>Prunus serotina</i> Ehrh.) foliage had significantly ( P ≤ 0.05) greater concentrations of calcium (Ca) and magnesium (Mg) through 2016 compared with samples from unlimed plots. Calcium and Mg capitals (g m^-2) in the Oi through A horizon combined were greater on limed plots than unlimed plots, largely due to increases in the thickness and nutrient concentration in the A horizon. Over 30-years, sugar maple basal area increment (cm² yr^-1 BAINC) ) was greater in limed plots, American beech (<i>Fagus grandifolia</i> Ehrh.) BAINC was unaffected, and black cherry BAINC was reduced in limed plots compared with unlimed plots. The sustained effect of this one-time lime treatment shows the strong role of efficient nutrient cycling in forests and suggests that the benefits over a substantial portion of a stand rotation may increase the feasibility of operational liming.

Forest Soil Cation Dynamics and Increases in Carbon on the Allegheny Plateau, PA, USA Following a Period of Strongly Declining Acid Deposition

Reductions in exchangeable calcium and magnesium and increase in exchangeable aluminum concentrations have been shown in soils impacted by acid deposition, including at four sites on the Allegheny Plateau, PA, USA, sampled in 1967 and 1997 during a period of peak deposition. We repeated sampling at these sites in 2017 to evaluate changes in soils during the more recent period when there has been a strong decline in acid deposition. The uppermost horizons, including the Oa and A horizons where humified organic matter transitions to mineral soil, were thicker, had higher concentrations of organic carbon and exchangeable calcium and magnesium, and lower concentrations of exchangeable aluminum in 2017 compared to 1997, approximating values measured in 1967. Below the Oa/A horizons, 2017 soil chemistry was more similar to the 1997 results, with some reduction of Ca in the recent measurements. These results suggest recovery of base cation–aluminum balance in surface horizons and may indicate a reduction of aluminum mobilization and increased efficiency of vegetation recycling of nutrients with decreased acid anion concentrations. These changes are consistent with a partial recovery from acid deposition. However, the increase in humified soil organic matter may also be affected by coincident increases in temperature and soil moisture.

The Forest of Unintended Consequences: Anthropogenic Actions Trigger the Rise and Fall of Black Cherry

The twentieth century confluence of clear-cutting, deer overabundance, and rising nitrogen deposition favored dominance by the shade-intolerant, unpalatable, and nitrogen-demanding black cherry (Prunus serotina) throughout the Allegheny Plateau of the eastern United States. The abundance of this species conferred unique and valuable ecological and economic benefits that shaped regional biodiversity and societies. Sustaining these values is increasingly difficult because black cherry, seemingly inexplicably, has experienced diminished establishment, growth, and survival in the twenty-first century. In the present article, we chronicle the change and assess underlying drivers through a literature review and new analyses. We found negative plant–soil microbial feedback loops and lowered nitrogen deposition are biologically, temporally, and geographically consistent with observed declines. The evidence suggests that black cherry dynamics are the unintended consequence of actions and policies ostensibly unconnected to forests. We suggest that these shifts are a bellwether of impending changes to forests, economies, and ownership patterns regionally and beyond.

Vegetation Changes Associated with the Younger Dryas from the Sediments of Silver Lake, Summit County, Ohio, USA

As the climate was warming during the last deglaciation, a millennium-long return to near-glacial conditions—called the Younger Dryas (YD) stadial—occurred about 12.9 to 11.7 ka ago. Prior studies have characterized the vegetation and climatic impacts of the YD stadial in the US upper Midwest from a network of fossil pollen records. The goal of this study was to locate the pronounced rise in organic matter and Pinus (pine) pollen—associated with the latter part of the YD event—in a sediment core from Silver Lake, a kettle lake in Summit County, Ohio. Based upon radiocarbon dating of the Silver Lake sediment core, an increase in sediment organic matter at 1,070 cm (35.1 ft) core depth dates to 12,130 calibrated years (cal yr) BP within the latter part of the YD stadial. A pollen study spanning the change in organic matter displays a gradual decline in Picea (spruce) pollen as well as a pronounced increase in Pinus pollen, similar to published records of the latter part of the YD event. Thus, the Silver Lake pollen record adds a new site to the network of fossil pollen sites, and further refines the vegetation changes within the Allegheny Plateau of Ohio that occurred during the latter part of the YD event. Furthermore, identifying the pronounced rise in Pinus pollen allows for biostratigraphic correlation between the Silver Lake record and another local dated pollen record. This biocorrelation adds further support to the Silver Lake radiometric age model.

Light Interception and the Growth of Pastures under Ideal and Stressful Growing Conditions on the Allegheny Plateau

Pasture-based livestock production is impacted by management and weather. In pastures, there is conflict between leaf retention for plant growth and leaf harvest for animal nutrition. Defoliated pastures with low light interception (LI) may have a low forage growth rate (FGR), while excessive growth shades leaves, reducing FGR and resulting in an S-shaped regrowth curve. To optimize production, it is best to keep FGR linear. Three studies were conducted to evaluate the impact of management and weather on FGR. Replicated pastures were used to measure FGR when grazed from 25 to 10 cm and allowed to regrow. The impact of alternative defoliation timings and intensities on FGR were studied using clipped treatments at three recovery intervals and two stubble heights. Variability in FGR was studied using a field validated plant growth model. Of the 24 growth periods studied, two displayed exponential, 12 linear and 10 linear-plateau growth. There was no effect of FM on growth curve form. In May and June, LI increased with canopy height, up to 0.93. Stubble height and days of growth impacted FGR with an interaction. There was no treatment impact on root density. Weather caused variation in FGR. A low FGR risk occurs at high elevations; greater risk occurs east of the plateau.