Treesearch

Peatlands store one-third of Earth's soil carbon, the stability of which is uncertain due to climate change-driven shifts in hydrology and vegetation, and consequent impacts on microbial communities that mediate decomposition. Peatland carbon cycling varies over steep physicochemical gradients characterizing vertical peat profiles. However, it is unclear how drought-mediated changes in plant functional groups (PFGs) and water table (WT) levels affect microbial communities at different depths. We combined a multiyear mesocosm experiment with community sequencing across a 70-cm depth...

Exotic plant invasions alter ecosystem properties and threaten ecosystem functions globally. Interannual climate variability (ICV) influences both plant community composition (PCC) and soil properties, and interactions between ICV and PCC may influence nitrogen (N) and carbon (C) pools. We asked how ICV and non-native annual grass invasion covary to influence soil and plant N and C in a semiarid shrubland undergoing widespread ecosystem transformation due to invasions and altered fire regimes. We sampled four progressive stages of annual grass invasion at 20 sites across a large (25,000...

Reductions in acidic deposition rates through legislative actions in North America and Europe have stemmed further environmental degradation and shifted the focus to potential recovery. In the early 2000s, it had become clear that recovery of surface waters was being slowed by the long-term effects of acidic deposition on soils, which were only then becoming well documented. As a result, recovery of soils from acidic deposition has drawn considerable attention with respect to both aquatic and terrestrial ecosystems, particularly in the most recent decade. Recovery of surface waters is...

Dissolved organic matter (DOM) can serve as an indicator of watershed carbon cycling, and links terrestrial to aquatic ecosystems. The extent DOM is microbially processed before it enters aquatic ecosystems is expected to change with soil depth and landscape position, and as some research suggests, in response to recovery from chronic acidification. Here we examined DOM within freely flowing soil pore water and stream water collected from reference and calcium silicate-treated watersheds at the Hubbard Brook Experimental Forest, New Hampshire, USA. Dissolved organic carbon (DOC) and...

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...

Specific electrical conductivity (SC) is a basic, effective indicator of water quality. The recent increase in SC data collected with high-frequency sensors has created a strong need for algorithms that can aid interpretation of these data. This study presents an algorithm that finds and quantifies SC temporal patterns and applies that algorithm to a dataset from a 7.5 km2 forested catchment in central New Hampshire. During and after rain events, we show three patterns that emerge in SC time series: A solute flush, resulting in an initial increase in SC, followed by a dilution, followed by...

Exposure to ozone pollution has serious health risks. Damage to lungs and impairment of cardiovascular health are of particular concern for vulnerable populations, including children, the elderly, and individuals from “disadvantaged” communities whose health may already be compromised. This report describes three successive studies that led to the development of techniques for directly monitoring human exposure to ozone. Experiment 1 was a proof of concept and exploration of potential systematic errors. Experiment 2 was a more extensive use of personal monitoring to evaluate differences in...

The structural and functional attributes of urban and peri-urban forests are the basis for the provision of a suite of ecosystem services that directly and indirectly benefit residents across scales, tenures and land uses. As such, many local governments promote municipal urban forest initiatives such as maintenance and management plans, ordinances, and tree-giveaway programs (e.g. Orlando, USA and Sydney, Australia). However, the effectiveness and distributional fairness of these activities often overlooks residents’ values and preferences for certain tree functional traits, sizes,...

To determine the effect of nursery lifting dates on field performance of containerized Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings, we lifted and stored seedlings from 2 seed lots on 9 dates from late October 2019 to early March 2020. We planted the seedlings in a field test and in large pots in April 2020. All seedlings broke bud and grew vigorously. No mortality occurred in the pots, and less than 6 percent mortality occurred in the field test. Bud burst was slightly faster for seedlings lifted after mid-January than for those lifted on earlier dates. We found consistent...

Long-term observations inform relationships among changes in vegetation, climate, and land use. For the eastern United States, I compared the timing of tree change, comprised of density and diversity increases, with the timing of climate change, as measured by change point detection of the Palmer Modified Drought Index (PMDI) that accounts for water balance, in two prairie ecological provinces, four grassland landscapes, and four forest landscapes. Historical evidence supplied documentation of tree density increases between approximately 1860 and 1890 in the two prairie provinces of...