Treesearch

Mercury (Hg) in the environment has been receiving considerable attention in recent years, but little is known about Hg accumulation in trees. We analyzed Hg in tree rings from four tree species at the Hubbard Brook Experimental Forest in New Hampshire to determine whether Hg concentrations are more influenced by soil Hg concentrations, which have been stable or increasing due to the cumulative retention of historical atmospheric Hg deposition, or by atmospheric Hg deposition, which has declined in recent decades. Declining concentrations from the top to the bottom of the bole (p < 0.001)...

The 2019 National Silviculture Workshop brought together nearly 300 forestry practitioners and researchers from across the United States and Canada. The theme of this year’s biennial Workshop was Forest Management-Research Partnerships.

Recent mountain pine beetle (Dendroctonus ponderosae; MPB) outbreaks have caused one of the most widespread and dramatic changes in forest condition in North American forests in more than a century and highlighted challenges facing resource managers. To address uncertainty regarding the consequences of post-harvest woody residue management on soil productivity and tree regeneration following MPB outbreaks in lodgepole pine-dominated forests we compared three treatment prescriptions (bole-only harvest, whole-tree harvest, and whole-tree harvest with scarification) and uncut stands. The...

A higher frequency of increasingly severe droughts highlights the need for short-term measures to adapt existing forests to climate change. The maintenance of reduced stand densities has been proposed as a promising silvicultural tool for mitigating drought stress. However, the relationship between stand density and tree drought susceptibility remains poorly understood, especially across ecological gradients. Here, we analysed the effect of reduced stand density on tree growth and growth sensitivity, as well as on short-term drought responses (resistance, recovery, and resilience) of Scots...

The Aspen-FACE (Free-Air Carbon Enrichment) experiment was an 11-yr study of the effect of elevated CO2 and ozone (alone and in combination) on the growth productivity of model aspen communities (pure aspen, aspen-birch, and aspen-maple) in the field in northern Wisconsin, USA. Uncertainty remains about how these short-term plot-level responses might play out at landscape scales where climate change, competition, succession, and disturbances interact with tree-level responses. In this study, we used a recent physiology-based approach (PnET-Succession v3.1) within the forest landscape model...

In 1973, as part of research addressing the timing, volume, and source of streamflows, a 22.34 ha watershed on the Fernow Experimental Forest was planted with Norway spruce (Picea abies). This publication describes the growth and productivity of this unusual Norway spruce plantation over the intervening 45 years, including information on stand density, incursion of native hardwoods, and reaction to a major disturbance, Superstorm Sandy in 2012.

Despite growing understanding of how rising temperatures affect carbon cycling, the impact of long-term and whole forest warming on the suite of essential and potentially limiting nutrients remains understudied, particularly for elements other than N and P. Whole ecosystem warming experiments are limited, environmental gradients are often confounded by variation in factors other than temperature, and few studies have been conducted in the tropics. We examined litterfall, live foliar nutrient content, foliar nutrient resorption efficiency (NRE), nutrient return, and foliar nutrient use...

Long-term streamflow datasets inevitably include gaps, which must be filled to allow estimates of runoff and ultimately catchment water budgets. Uncertainty introduced by filling gaps in discharge records is rarely, if ever, reported. We characterized the uncertainty due to streamflow gaps in a reference watershed at the Hubbard Brook Experimental Forest (HBEF) from 1996 to 2009 by simulating artificial gaps of varying duration and flow rate, with the objective of quantifying their contribution to uncertainty in annual streamflow. Gaps were filled using an ensemble of regressions relating...

Mastication is becoming a popular wildland fuel treatment in the United States but little is known about how masticated fuels dry over time, especially as these atypical fuelbeds age. This report summarises measured drying rates of different-aged masticated fuelbeds built from material collected from sites that were treated using one of four mastication techniques. We recreated three replicates of masticated fuelbeds in wire mesh cages using material collected from 13 sites sampled throughout the US Rocky Mountains. These caged fuelbeds were saturated and then their moisture contents were...

This study evaluated the bleachability of wood fibers from acid hydrotropic fractionation (AHF) of birch using ptoluenesulfonic acid (p-TsOH) at low temperatures below 90 °C. The wood fibers had varying amounts of lignin after AHF under different conditions using both batch and flow-through configurations. The extent of lignin reprecipitation in batch mode was evaluated by extended washing with p-TsOH. 2D 13C−1H nuclear magnetic resonance (NMR) spectroscopy indicated that residual lignin on fibers from batch reaction was significantly more condensed than that from flow-through under...