The Effects of Late Spring Frost on Forest and Landscape Health and Recovery of the Black Rock Forest, New York

Projected changes in climate are expected to increase the frequency of late spring frost events in the Northeast US. Such events can be harmful to trees because freezing temperatures that occur after leaf-out can damage or kill young leaves. The resultant defoliation typically forces a second flush of leaves, but delays canopy development, which in turn delays the onset of canopy carbon uptake and alters canopy thermal properties. In this study, we analyzed a recent freeze event that occurred on 8-9 May 2020 (DOY 129-130) at Black Rock Forest (BRF), which is in the Hudson Highlands of southeastern New York State. We compared satellite images collected during the 2019 (no frost year) and 2020 growing season

Elevated growth and biomass along temperate forest edges

Fragmentation transforms the environment along forest edges. The prevailing narrative, driven by research in tropical systems, suggests that edge environments increase tree mortality and structural degradation resulting in net decreases in ecosystem productivity. We show that, in contrast to tropical systems, temperate forest edges exhibit increased forest growth and biomass with no change in total mortality relative to the forest interior. We analyze \u3e 48,000 forest inventory plots across the north-eastern US using a quasi- experimental matching design. At forest edges adjacent to anthropogenic land covers, we report increases of 36.3% and 24.1% in forest growth and biomass, respectively. Inclusion of edge impacts increases estimates of forest productivity by up to 23% in agriculture- dominated areas, 15% in the metropolitan coast, and + 2% in the least-fragmented regions. We also quantify forest fragmentation globally, at 30-m resolution, showing that temperate forests contain 52% more edge forest area than tropical forests. Our analyses upend the conventional wisdom of forest edges as less productive than intact forest and call for a reassessment of the conservation value of forest fragments

Effects of Harvesting on Nutrient Cycling, Red Spruce Radial Growth, and Dendrochemistry 30 Years after Harvesting in Northern Maine, USA

The objective of this retrospective study was to quantify the long-term effects of tree harvesting intensity on red spruce-flats in northern Maine. Six stands harvested approximately 30 years ago with volume removals of 30, 50, and 80 percent and two unharvested reference sites were selected. All of the stands were originally harvested during the winter with in-woods delimbing. Soil physical and chemical properties, stand basal area, species composition, and forest floor cover type were evaluated. Increment cores were extracted to look at growth and chemical indicators of tree response to harvesting and associated changes in soil solution chemistry. Dendrochemistry has not been used in this context before. Ion exchange resin membranes (IERMs) were employed to characterize relative differences among sites in current pools of plantavailable nutrients in soil solution. Though total BA does not currently differ among stands, the 80% removal stands have the most balsam fir and the least red spruce. The proportion of the forest l-loor covered with bryophytes declined with decreasing proportions of overstory red spruce, which was in turn related to harvest intensity. O horizon mass and thickness were lowest in the 80% removal, while thickness was greatest in reference stands and mass was greatest in the 50% removal. Harvesting resulted in significant differences in soil chemistry that were pervasive in the Oea horizons, but nearly absent in the mineral soil. Exchangeable Ca, K, Ca and base saturation, Ca:Al ratios, pH, and CEC, were highest in the 50% removal. Percent organic matter and C:N ratios were significantly lower in the 80% removal than the reference, suggesting that harvesting decreases these variables. Observed changes in soil chemistry were attributed to harvest-induced changes in O horizon decomposition dynamics and the presence of slash after the harvest, although there were possible pre-treatment differences important to our interpretation. There was no evidence of a stand-level increase in radial growth in response to harvesting, though a post-1960 regional decline in red spruce growth rates may have masked a growth response. Presumed changes in post-harvest soil solution chemistry were not detected in sample tree cores. Additionally, sample trees were codominants at the time of harvesting, and light may not have been limiting. A high frequency of cores exhibiting a Ca enrichment in the 1970s may be indicative of an increase in Ca availability in the 1990s. Current labile pools of plant available nutrients, as measured by IERMs, do not appear to have been significantly altered by harvesting. However, Ca as a proportion of the base cations Ca, K, Mg is higher in the more heavily harvested stands, suggesting that Ca has increased disproportionately to K and Mg. This study used methods for field implementation of IERMs that were adapted from other studies for use in coniferous forests. We found that DI water that is typically used for transport can potentially desorb measurable amounts of ions, particularly K, from the IERMs. This needs to be further investigated to improve interpretation of data obtained from IERMs

Tree Productivity Enhanced with Conversion from Forest to Urban Land Covers.

Urban areas are expanding, changing the structure and productivity of landscapes. While some urban areas have been shown to hold substantial biomass, the productivity of these systems is largely unknown. We assessed how conversion from forest to urban land uses affected both biomass structure and productivity across eastern Massachusetts. We found that urban land uses held less than half the biomass of adjacent forest expanses with a plot level mean biomass density of 33.5 ± 8.0 Mg C ha(-1). As the intensity of urban development increased, the canopy cover, stem density, and biomass decreased. Analysis of Quercus rubra tree cores showed that tree-level basal area increment nearly doubled following development, increasing from 17.1 ± 3.0 to 35.8 ± 4.7 cm(2) yr(-1). Scaling the observed stem densities and growth rates within developed areas suggests an aboveground biomass growth rate of 1.8 ± 0.4 Mg C ha(-1) yr(-1), a growth rate comparable to nearby, intact forests. The contrasting high growth rates and lower biomass pools within urban areas suggest a highly dynamic ecosystem with rapid turnover. As global urban extent continues to grow, cities consider climate mitigation options, and as the verification of net greenhouse gas emissions emerges as critical for policy, quantifying the role of urban vegetation in regional-to-global carbon budgets will become ever more important

Ecosystem structure.

<p>Aboveground biomass (AGB) and diameter at breast height (DBH) for all low density residential (LDR), medium density residential (MDR), and other (OTH) 2013 land cover change field plots. The area weighted urban estimate was based on the areal extents from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136237#pone.0136237.t001" target="_blank">Table 1</a>. Error bars are 95% confidence intervals.</p

Basal area increment before and after land cover change.

<p>Mean basal area increment before and after conversion from forest to urban land cover for each tree. The 95% confidence intervals reflect both inherent variability in growth rates and changes in the number of rings before and after land conversion. Individual cores are color coded to denote the difference in before vs. after basal area increment and are categorized as a “Negative/No Response”, “Typical Positive”, and “Strong Positive.” Trees which exhibited a “strong” response were those that had a ≥ 200% increase in growth rates following land use change.</p

Ecosystem characteristics and land conversion rates.

<p>Ecosystem structure characteristics of all plots, parsed by forest conversion pathway. Land area within the eastern Massachusetts study area includes all five counties in which we had study plots and is approximately 8,800 km². Stem density and canopy cover estimates across all development types are area weighted based on the current areal extent of each development category. Land conversion rates were based on the difference in areal extent within each category between 1971 and 1999. Current values were generated from 2013 field and FIA data.</p

Basal area increment as a function of DBH class.

<p>Basal area increment as a function of diameter at breast height (DBH) class before and after conversion to urban land covers. DBH classes represent binned DBH values spaced at 5cm intervals. The solid lines represent the medians for each category.</p