Ammonia emissions from deciduous forest after leaf fall

The understanding of biochemical feedback mechanisms in the climate system is lacking knowledge in relation to bi-directional ammonia (NH3) exchange between natural ecosystems and the atmosphere. We therefore study the atmospheric NH3 fluxes during a 25-day period during autumn 2010 (21 October to 15 November) for the Danish beech forest Lille Bøgeskov to address the hypothesis that NH3 emissions occur from deciduous forests in relation to leaf fall. This is accomplished by using observations of vegetation status, NH3 fluxes and model calculations. Vegetation status was observed using plant area index (PAI) and leaf area index (LAI). NH3 fluxes were measured using the relaxed eddy accumulation (REA) method. The REA-based NH3 concentrations were compared to NH3 denuder measurements. Model calculations of the atmospheric NH3 concentration were obtained with the Danish Ammonia MOdelling System (DAMOS). The relative contribution from the forest components to the atmospheric NH3 flux was assessed using a simple two-layer bi-directional canopy compensation point model. A total of 57.7% of the fluxes measured showed emission and 19.5% showed deposition. A clear tendency of the flux going from deposition of −0.25 ± 0.30 μg NH3-N m−2 s−1 to emission of up to 0.67 ± 0.28 μg NH3-N m−2 s−1 throughout the measurement period was found. In the leaf fall period (23 October to 8 November), an increase in the atmospheric NH3 concentrations was related to the increasing forest NH3 flux. Following leaf fall, the magnitude and temporal structure of the measured NH3 emission fluxes could be adequately reproduced with the bi-directional resistance model; it suggested the forest ground layer (soil and litter) to be the main contributing component to the NH3 emissions. The modelled concentration from DAMOS fits well the measured concentrations before leaf fall, but during and after leaf fall, the modelled concentrations are too low. The results indicate that the missing contribution to atmospheric NH3 concentration from vegetative surfaces related to leaf fall are of a relatively large magnitude. We therefore conclude that emissions from deciduous forests are important to include in model calculations of atmospheric NH3 for forest ecosystems. Finally, diurnal variations in the measured NH3 concentrations were related to meteorological conditions, forest phenology and the spatial distribution of local anthropogenic NH3 sources. This suggests that an accurate description of ammonia fluxes over forest ecosystems requires a dynamic description of atmospheric and vegetation processes

A comparison of three canopy interception models for a leafless mixed deciduous forest stand in the eastern United States

Canopy interception of incident precipitation is a critical component of the forest water balance during each of the four seasons. Models have been developed to predict precipitation interception from standard meteorological variables because of acknowledged difficulty in extrapolating direct measurements of interception loss from forest to forest. No known study has compared and validated canopy interception models for a leafless deciduous forest stand in the eastern United States. Interception measurements from an experimental plot in a leafless deciduous forest in northeastern Maryland (39°42'N, 75°5'W) for 11 rainstorms in winter and early spring 2004/05 were compared to predictions from three models. The Mulder model maintains a moist canopy between storms. The Gash model requires few input variables and is formulated for a sparse canopy. The WiMo model optimizes the canopy storage capacity for the maximum wind speed during each storm. All models showed marked underestimates and overestimates for individual storms when the measured ratio of interception to gross precipitation was far more or less, respectively, than the specified fraction of canopy cover. The models predicted the percentage of total gross precipitation (PG) intercepted to within the probable standard error (8.1%) of the measured value: the Mulder model overestimated the measured value by 0.1% of PG; the WiMo model underestimated by 0.6% of PG; and the Gash model underestimated by 1.1% of PG. The WiMo model’s advantage over the Gash model indicates that the canopy storage capacity increases logarithmically with the maximum wind speed. This study has demonstrated that dormant-season precipitation interception in a leafless deciduous forest may be satisfactorily predicted by existing canopy interception models

Evaluation of Pit-trap Transects With Varied Trap Spacing in a Northern Michigan Forest

The study compared effects of four distances between traps (range 0.5-4.0 m) on arthropod captures. Twelve traps were aligned in each of four transects, and 20 samples. trap were obtained during summer and fall in a northern Michigan deciduous forest. Catches proved to be unaffected by trap spacing. Rather, they reflected local within-site differences in abundance of dominant species

An Annotated List and New Species Descriptions of Collembola Found in the Project Elf Study Area of Michigan

An annotated list of 80 collembolan species taken from the ELF Project area in Dickinson County. Michigan, is presented. Two new species are described, a new record for the United States is established, and new records for Michigan\u27s Upper Peninsula are reported. Specimens were obtained using pitfall traps and extraction of liner and soil cores taken from deciduous forest.

Carbon fluxes in a mature deciduous forest under elevated CO₂

This PhD thesis addressed several major aspects of the carbon (C) cycle in a c. 100-year-old, mixed deciduous forest under elevated CO₂ with an emphasis on below-ground processes. The aim was to assess the responses of tree fine roots and soil respiration to canopy CO₂ enrichment (? 550 ppm) in this tallest forest studied to date. Furthermore, leaf gas-exchange of the five study species was examined to ascertain the long-term response of photosynthetic carbon uptake to elevated atmospheric CO₂. Investigations at the Swiss Canopy Crane (SCC) experimental site were guided by the following key questions: (1) Does below-ground C allocation to fine root production increase in response to CO₂ enrichment in order to acquire more nutrients to match the enhanced C supply in the forest canopy? (2) Is below-ground metabolism enhanced and therefore forest soil respiration stimulated by canopy CO₂ enrichment? (3) Is leaf-level photosynthesis persistently stimulated by elevated CO₂ in this stand or had these mature broad-leaved trees reduced their carbon up- take by photosynthetic down-regulation under long-term CO₂ enrichment? Findings from earlier studies at the SCC site, including 13C isotope tracing, all point towards an in- creased flux of C through CO₂-enriched trees to the soil but neither fine root biomass nor soil respiration were stimulated by elevated CO₂. Surprisingly, fine root biomass in bulk soil and ingrowth cores showed strong reductions by ? 30% in year five and six but were unaffected in the following seventh year of CO₂ enrichment. Given the absence of a positive biomass response of fine roots, we assumed that the extra C assimilated in the CO₂-enriched forest canopy was largely respired back to the atmosphere via increases in fine root and rhizosphere respiration and the metabolization of increased root derived exudates by soil microbes. Indeed, 52% higher soil air CO₂ concentration during the growing season and 14% greater soil microbial biomass both in- dicated enhanced below-ground metabolism in soil under CO₂-enriched trees. However, this did not translate into a persistent stimulation of soil respiration. At times of high or continuous precipitation soil water savings under CO₂-exposed trees (resulting from reduced sapflow) led to excessive soil moisture (> 45 vol.-%) impeding soil gas-exchange and thus soil respiration. Depending on the interplay between soil temperature and the consistently high soil water content in this stand, instantaneous rates of soil respiration were periodically reduced or increased under elevated CO₂ but on a diel scale and integrated over the growing season soil CO₂ emissions were similar under CO₂-enriched and control trees. Soil respiration could therefore not explain the fate of the extra C. The lacking sink capacity for additional assimilates led us to assume downward adjustment of photosynthetic capacity in CO₂-enriched trees thereby reducing carbon uptake in the forest canopy. Photosynthetic acclimation cannot completely eliminate the CO₂-driven stimulation in carbon uptake, but a reduction could hamper the detection of a CO₂ effect considering the low statistical power inevitably involved with such large-scale experiments. However, after eight years of CO₂ enrichment we found sustained stimulation in leaf photosynthesis (42-49%) indicating a lack of closure in the carbon budget for this stand under elevated atmospheric CO₂

Comparative Study of Photosynthesis Rates between Native Red Maple and Invasive Norway Maple in the Eastern Deciduous Forest

Invasive species, such as the Norway Maple, are often able to outcompete native species, such as the Red Maple by performing more efficiently in the environment compared to the native species. In this study, we examined if the Norway maple was able to outcompete the Red Maple in the Eastern Deciduous Forest because the Norway Maple had a higher rate of photosynthesis. The study found that the Norway Maple leaves had a slightly higher rate of carbon dioxide consumption than Red Maple leaves and that the Red Maple leaves had a higher rate of oxygen production compared to the Norway Maples. Since these differences were not statistically significant, the data suggested that the differences in the rate of photosynthesis between the two tree species is most likely very small. This suggests that the rate of photosynthesis is most likely not the advantage Norway Maples have over Red Maples that allows this invader to better compete for space in a forest

A review of the status of the fauna of selected protected areas in the major vegetation zones of Ghana

The fauna in four major vegetation types, namely, rainforest, semi-deciduous forest, inland savanna and coastal scrub and grassland, was examined with the main objective of providing a general description of the fauna and highlighting the species that are threatened or of special conservation concern, nationally and globally. The fauna examined weremammals (large and small), birds and reptiles. The sources of information include the Internet, books, journals and faunal survey reports on various forest reserves and protected areas in Ghana. The threat to fauna appears to be highest in the rainforest and the semi-deciduous forest. For mammals, 41.8 and 28 per cent are threatened in the rainforest and semi-deciduous forest, respectively. The comparable figures for birds are 4.5 and 3.1 per cent. The most endangered (critically endangered) mammal species in Ghana is the Miss Waldron’s red colobus monkey(Procolobus badius); current thinking is that it has gone extinct. Six species of mammals are endangered (IUCN) in the semi-deciduous forest, two in the rainforest and four in the inland savanna; no endangered species has been recorded in the coastal scrub and grassland. The main causes of threat to fauna in forest reserves are habitat degradation andfragmentation, to which mining activities have been contributing in recent times