Temporal scale and the accumulation of peat in a Sphagnum bog

1996 ◽  
Vol 74 (3) ◽  
pp. 366-377 ◽  
Author(s):  
Lisa R. Belyea ◽  
Barry G. Warner
Keyword(s):  
Mass Loss ◽  
Decay Rate ◽  
Nitrogen Concentration ◽  
Rate Coefficients ◽  
Short Term ◽  
Concentration Data ◽  
Peat Accumulation ◽  
Litter Bag ◽  
Sphagnum Bog

We examined short-term (decadal) and long-term (millenial) processes of peat accumulation, and the links between them, in a Sphagnum bog in continental Canada. A previously published model of bog growth was fitted to age profiles of the oxic acrotelm (surface, < 60 cm thick) and the underlying, anoxic catotelm (210 cm thick). Approximately 5300 years of accumulation were represented in a radiocarbon-dated core that extended to the base of the deepest part of the peat deposit. The model estimated that the overall rate at which material entered long-term storage in the catotelm was 60–66 g∙m−2∙a−1. Although the decay rate coefficient was near zero, the bog stopped accumulating peat within the past 1500 years, resulting from either a decrease in the rate of transfer of material from the acrotelm or an increase in the rate of decay of material at the top of the catotelm. The model of bog growth estimated recent inputs to the acrotelm (90–930 g∙m−2∙a−1) that were twofold higher than published field measurements of aboveground productivity, and decay rate coefficients (0.005–0.040 a−1) that were 10-fold lower than published litter-bag measurements of mass loss. The pattern of mass loss over time, approximated from nitrogen concentration data, deviated from the pattern predicted by exponential models of decay. Calculations of the balance between additions to and losses from the acrotelm suggest that the amount of material transferred to the underlying catotelm differs among microhabitats. Such spatial variability in short-term processes is incompatible with long-term processes determining the position of the acrotelm–catotelm boundary. We discuss the applicability of the model to continental peatlands and suggest ways to improve modelling of short-term autogenic processes. Keywords: peatland, peat accumulation, organic matter, decomposition, age profiles, mathematical models.

Mass loss and nitrogen dynamics of decaying litter of grasslands: the apparent low nitrogen immobilization potential of root detritus

1992 ◽  
Vol 70 (2) ◽  
pp. 384-391 ◽  
Author(s):  
T. R. Seastedt ◽  
W. J. Parton ◽  
D. S. Ojima
Keyword(s):  
Mass Loss ◽  
Nitrogen Availability ◽  
Inorganic Nitrogen ◽  
Nitrogen Concentration ◽  
C:N Ratio ◽  
Nitrogen Dynamics ◽  
Nitrogen Immobilization ◽  
Litter Bag ◽  
Root Litter ◽  
Low Nitrogen

Litter-bag studies and simulation modeling were used to examine the relationship between mass loss and nitrogen content of decaying prairie foliage and root litter. In contrast with forest studies, grassland roots were low in lignin and nitrogen, decayed more rapidly than foliage, and demonstrated very low nitrogen immobilization potentials. Our findings agree with reports indicating that buried substrates with high C:N ratios do not immobilize substantial amounts of nitrogen and that nitrogen-limited environments induce steeper slopes in the mass loss – nitrogen concentration relationship. However, results suggesting rapid nitrogen mineralization contradict our own studies demonstrating reduced inorganic nitrogen availability in soils of frequently burned prairie. Simulation of observed patterns using the CENTURY grassland model indicated that these results could not occur without creating soil organic matter with unrealistically high C:N ratios. Litter-bag studies of buried substrates therefore may provide an incomplete perspective on the mass loss and nitrogen dynamics of buried litter in grassland and agroecosystem soils. Key words: Andropogon gerardii, C:N ratio, decomposition, immobilization, mineralization, nitrogen.

Seasonality of foliar respiration in two dominant plant species from the Arctic tundra: response to long-term warming and short-term temperature variability

2014 ◽  
Vol 41 (3) ◽  
pp. 287 ◽  
Author(s):  
Mary A. Heskel ◽  
Danielle Bitterman ◽  
Owen K. Atkin ◽  
Matthew H. Turnbull ◽  
Kevin L. Griffin
Keyword(s):  
Carbon Cycling ◽  
Leaf Gas Exchange ◽  
Nitrogen Concentration ◽  
Temperature Variability ◽  
The Arctic ◽  
Photosynthetic Parameters ◽  
Carbon Exchange ◽  
Short Term ◽  
Photosynthesis And Respiration

Direct measurements of foliar carbon exchange through the growing season in Arctic species are limited, despite the need for accurate estimates of photosynthesis and respiration to characterise carbon cycling in the tundra. We examined seasonal variation in foliar photosynthesis and respiration (measured at 20°C) in two field-grown tundra species, Betula nana L. and Eriophorum vaginatum L., under ambient and long-term warming (LTW) conditions (+5°C), and the relationship of these fluxes to intraseasonal temperature variability. Species and seasonal timing drove most of the variation in photosynthetic parameters (e.g. gross photosynthesis (Agross)), respiration in the dark (Rdark) and light (Rlight), and foliar nitrogen concentration. LTW did not consistently influence fluxes through the season but reduced respiration in both species. Alongside the flatter respiratory response to measurement temperature in LTW leaves, this provided evidence of thermal acclimation. The inhibition of respiration by light increased by ~40%, with Rlight : Rdark values of ~0.8 at leaf out decreasing to ~0.4 after 8 weeks. Though LTW had no effect on inhibition, the cross-taxa seasonal decline in Rlight : Rdark greatly reduced respiratory carbon loss. Values of Rlight : Agross decreased from ~0.3 in both species to ~0.15 (B. nana) and ~0.05 (E. vaginatum), driven by decreases in respiratory rates, as photosynthetic rates remained stable. The influence of short-term temperature variability did not exhibit predictive trends for leaf gas exchange at a common temperature. These results underscore the influence of temperature on foliar carbon cycling, and the importance of respiration in controlling seasonal carbon exchange.

scholarly journals Small Roots of Parashorea chinensis Wang Hsie Decompose Slower than Twigs

Forests ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 301
Author(s):  
Gbadamassi G. O. Dossa ◽  
Yan-Qiang Jin ◽  
Xiao-Tao Lü ◽  
Jian-Wei Tang ◽  
Rhett D. Harrison
Keyword(s):  
Mass Loss ◽  
Nutrient Dynamics ◽  
Nitrogen Concentration ◽  
Nitrogen Transfer ◽  
Litter Bag ◽  
Carbon And Nitrogen ◽  
Ground Biomass ◽  
Study Results ◽  
Small Roots ◽  
Below Ground

Plants produce above- and below-ground biomass. However, our understanding of both production and decomposition of below-ground biomass is poor, largely because of the difficulties of accessing roots. Below-ground organic matter decomposition studies are scant and especially rare in the tropics. In this study, we used a litter bag experiment to quantify the mass loss and nutrient dynamics of decomposing twigs and small roots from an arbuscular mycorrhizal fungal associated tree, Parashorea chinensis Wang Hsie, in a tropical rain forest in Southwest China. Overall, twig litter decomposed 1.9 times faster than small roots (decay rate (k) twig = 0.255, root = 0.134). The difference in decomposition rates can be explained by a difference in phosphorus (P) concentration, availability, and use by decomposers or carbon quality. Twigs and small roots showed an increase in nitrogen concentration, with final concentrations still higher than initial levels. This suggests nitrogen transfer from the surrounding environment into decomposing twigs and small roots. Both carbon and nitrogen dynamics were significantly predicted by mass loss and showed a negative and positive relationship, respectively. Our study results imply that small roots carbon and nitrogen increase the resident time in the soil. Therefore, a better understanding of the carbon cycle requires a better understanding of the mechanisms governing below-ground biomass decomposition.

Can short-term litter-bag measurements predict long-term decomposition in northern forests?

2017 ◽  
Vol 416 (1-2) ◽  
pp. 419-426 ◽  
Author(s):  
Tim R. Moore ◽  
◽  
J. A. Trofymow ◽  
C. E. Prescott ◽  
B. D. Titus
Keyword(s):  
Short Term ◽  
Litter Bag ◽  
Northern Forests

scholarly journals Does the stress response predict the ability of wild birds to adjust to short-term captivity? A study of the rock pigeon ( Columbia livia )

2016 ◽  
Vol 3 (12) ◽  
pp. 160840 ◽  
Author(s):  
Frédéric Angelier ◽  
Charline Parenteau ◽  
Colette Trouvé ◽  
Nicole Angelier
Keyword(s):  
Stress Response ◽  
Mass Loss ◽  
Body Mass ◽  
Stress Hormones ◽  
Short Term ◽  
Body Mass Loss ◽  
Lower Ability ◽  
Columbia Livia ◽  
Confined Environment

Although the transfer of wild animals to captivity is crucial for conservation purposes, this process is often challenging because some species or individuals do not adjust well to captive conditions. Chronic stress has been identified as a major concern for animals held on long-term captivity. Surprisingly, the first hours or days of captivity have been relatively overlooked. However, they are certainly very stressful, because individuals are being transferred to a totally novel and confined environment. To ensure the success of conservation programmes, it appears crucial to better understand the proximate causes of interspecific and interindividual variability in the sensitivity to these first hours of captivity. In that respect, the study of stress hormones is relevant, because the hormonal stress response may help to assess whether specific individuals or species adjust, or not, to such captive conditions (‘the stress response-adjustment to captivity hypothesis’). We tested this hypothesis in rock pigeons by measuring their corticosterone stress response and their ability to adjust to short-term captivity (body mass loss and circulating corticosterone levels after a day of captivity). We showed that an increased corticosterone stress response is associated with a lower ability to adjust to short-term captivity (i.e. higher body mass loss and circulating corticosterone levels). Our study suggests, therefore, that a low physiological sensitivity to stress may be beneficial for adjusting to captivity. Future studies should now explore whether the stress response can be useful to predict the ability of individuals from different populations or species to not only adjust to short-term but also long-term captivity.

Interactions of airborne methyl jasmonate with vegetative storage protein gene and protein accumulation and biomass partitioning in Populus plants

2000 ◽  
Vol 30 (7) ◽  
pp. 1106-1113 ◽  
Author(s):  
T Beardmore ◽  
S Wetzel ◽  
M Kalous
Keyword(s):  
Methyl Jasmonate ◽  
Storage Protein ◽  
Storage Proteins ◽  
Nitrogen Concentration ◽  
Protein Accumulation ◽  
Vegetative Storage Protein ◽  
Short Term ◽  
Specific Expression ◽  
Vegetative Storage Proteins

In young poplar (Populus nigra Muench × Populus maximowiczii A. Henry) plants, vegetative storage proteins (VSPs), the bark storage protein (BSP), and (or) wound-inducible 4 protein (WIN4) mRNAs were present in the apical and basal leaves and in the basal leaves, respectively. VSPs accumulated in the apical leaves and to a lesser extent in the stem. The response of the plants to 20 µM airborne methyl jasmonate (MJ) was examined in four parts ( apical and basal leaves, stem, and roots) in both short-term (within 72 h) and long-term (1, 2, 3, and 4 weeks) experiments. In the short-term, MJ-treated plants either induced or increased the part-specific expression of win4 and bsp, and accumulation of BSP and (or) WIN4. In the long-term, MJ treatment resulted in part-specific alterations in protein and nitrogen concentration and further altered BSP and WIN4 accumulation. The MJ-treated plants increased both the biomass allocation to the stem, without a change in the relative growth rate, and the tolerance low temperature (-2°C). Together, these results suggest the BSP and WIN4 are both involved in short-term N cycling and that exogenous MJ treatment promotes changes in nitrogen metabolism in poplar.

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Comparison of Auditory, Language, Memory, and Attention Abilities in Children With and Without Listening Difficulties

2020 ◽  
Vol 29 (4) ◽  
pp. 710-727
Author(s):  
Beula M. Magimairaj ◽  
Naveen K. Nagaraj ◽  
Alexander V. Sergeev ◽  
Natalie J. Benafield
Keyword(s):  
Auditory Processing ◽  
Short Term Memory ◽  
Group Differences ◽  
Long Term Memory ◽  
Short Term ◽  
Significant Group ◽  
Term Memory ◽  
Memory And Attention ◽  
Speed And Accuracy

Objectives School-age children with and without parent-reported listening difficulties (LiD) were compared on auditory processing, language, memory, and attention abilities. The objective was to extend what is known so far in the literature about children with LiD by using multiple measures and selective novel measures across the above areas. Design Twenty-six children who were reported by their parents as having LiD and 26 age-matched typically developing children completed clinical tests of auditory processing and multiple measures of language, attention, and memory. All children had normal-range pure-tone hearing thresholds bilaterally. Group differences were examined. Results In addition to significantly poorer speech-perception-in-noise scores, children with LiD had reduced speed and accuracy of word retrieval from long-term memory, poorer short-term memory, sentence recall, and inferencing ability. Statistically significant group differences were of moderate effect size; however, standard test scores of children with LiD were not clinically poor. No statistically significant group differences were observed in attention, working memory capacity, vocabulary, and nonverbal IQ. Conclusions Mild signal-to-noise ratio loss, as reflected by the group mean of children with LiD, supported the children's functional listening problems. In addition, children's relative weakness in select areas of language performance, short-term memory, and long-term memory lexical retrieval speed and accuracy added to previous research on evidence-based areas that need to be evaluated in children with LiD who almost always have heterogenous profiles. Importantly, the functional difficulties faced by children with LiD in relation to their test results indicated, to some extent, that commonly used assessments may not be adequately capturing the children's listening challenges. Supplemental Material https://doi.org/10.23641/asha.12808607

Contactless Semi-Implantable Electromagnetic Middle Ear Device for the Treatment of Sensorineural Hearing Loss: Short-Term and Long-Term Animal Experiments

1995 ◽  
Vol 28 (1) ◽  
pp. 121-140 ◽  
Author(s):  
Anthony J. Maniglia ◽  
Wen H. Ko ◽  
Mary Rosenbaum ◽  
Ted Falk ◽  
Wei-Lin Zhu ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Sensorineural Hearing Loss ◽  
Middle Ear ◽  
Animal Experiments ◽  
Sensorineural Hearing ◽  
Short Term
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