Factors affecting apparent 15N fractionation during nitrogen mineralisation in soils with different root litter inputs

Soil Research ◽  
2011 ◽  
Vol 49 (1) ◽  
pp. 34 ◽  
Author(s):  
Jorge Sierra ◽  
Lucienne Desfontaines
Keyword(s):  
Mineral Soil ◽  
Organic N ◽  
Factors Affecting ◽  
Model Simulations ◽  
Incubation Experiments ◽  
Root Litter ◽  
Pool Model ◽  
Ecosystem Studies ◽  
Field Incubation ◽  
N Pool

Nitrogen-15 (15N) fractionation during N mineralisation is frequently invoked to interpret data of N cycling in N-isotope-based ecosystem studies. Because direct measurement of actual fractionation (Dact) is difficult to perform, it is currently estimated from laboratory or field incubation experiments (apparent fractionation, Dapp). However, the procedure of calculation may induce bias in the estimations due to several factors controlled by litter inputs. The objective of this study was to assess the effects of litter inputs and the size and 15N content of organic N fractions on Dapp. Laboratory incubations were performed using soils receiving different amount of root litter from legume trees and grass in an agroforestry plot. The 15N contents of organic N and mineralised N were determined. The results were interpreted with a ‘three-N’ pool model considering two labile organic N pools derived from litter of the tree and the grass, and a recalcitrant organic N pool comprising organic N in mineral soil. The model was used to explore mechanisms that could explain the Dapp obtained in the incubation experiment. Model simulations well duplicated the observed relationships between organic N, mineralised N, their 15N content, and Dapp. Dapp varied from 1.2‰ to 2.4‰. It was negatively correlated with the distance from trees (R2 = 0.91, P < 0.05) and positively correlated with total organic N (R2 = 0.81, P < 0.05). Model simulations indicated that these correlations did not reflect a control of 15N fractionation, but were an artefact induced by the higher decomposition rate of the labile organic N depleted in 15N. This induced an overestimation of 15N fractionation that varied from 10% to 55%. Our results indicated that the procedure currently applied to estimate 15N fractionation during mineralisation may induce large overestimations depending upon the amount of litter input, and the size and 15N content of the organic N pools.

scholarly journals Germination, Establishment, and Mortality of Naturally Seeded Southwestern Ponderosa Pine

2003 ◽  
Vol 18 (2) ◽  
pp. 109-114 ◽  
Author(s):  
Steven J. Stein ◽  
Diana N. Kimberling
Keyword(s):  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Mineral Soil ◽  
Mortality Data ◽  
Mortality Factors ◽  
Seedling Mortality ◽  
Prescribed Burns ◽  
Factors Affecting ◽  
Northern Arizona ◽  
Lepidopteran Larvae

Abstract Information on the mortality factors affecting naturally seeded conifer seedlings is becoming increasingly important to forest managers for both economic and ecological reasons. Mortality factors affecting ponderosa pine (Pinus ponderosa) seedlings immediately following natural germination and through the following year were monitored in Northern Arizona. The four major mortality factors in temporal order included the failure of roots to establish in the soil (27%), herbivory by lepidopteran larvae (28%), desiccation (30%), and winterkill (10%). These mortality factors were compared among seedlings germinating in three different overstory densities and an experimental water treatment. Seedlings that were experimentally watered experienced greater mortality than natural seedlings due to herbivory (40%), nearly as much mortality due to the failure of roots to establish in the soil (20%), less mortality due to winterkill (5%), and no mortality due to desiccation. The seedling mortality data through time were summarized using survivorship curves and life tables. Our results suggest that managers should consider using prescribed burns to decrease the percentage of seedlings that die from failure of their roots to reach mineral soil and from attack by lepidopteran larvae. West. J. Appl. For. 18(2):109–114.

Modification of atrzine desorption during field incubation experiments

1992 ◽  
Vol 123-124 ◽  
pp. 333-344 ◽  
Author(s):  
Enrique Barriuso ◽  
William Koskinen ◽  
Brent Sorenson
Keyword(s):  
Incubation Experiments ◽  
Field Incubation

scholarly journals Dynamic of nitrogen and dissolved organic carbon in an alpine forested catchment: atmospheric deposition and soil solution trends

2019 ◽  
Vol 34 ◽  
pp. 41-66 ◽  
Author(s):  
Raffaella Balestrini ◽  
Carlo Andrea Delconte ◽  
Andrea Buffagni ◽  
Alessio Fumagalli ◽  
Michele Freppaz ◽  
...  
Keyword(s):  
Soil Solution ◽  
Forest Ecosystem ◽  
Forest Floor ◽  
Mineral Soil ◽  
Chemical Species ◽  
Organic N ◽  
Seasonal Temperature ◽  
Inorganic N ◽  
Forest Floor Leachates ◽  
Throughfall Deposition

A number of studies have reported decreasing trends of acidifying and N deposition inputs to forest areas throughout Europe and the USA in recent decades. There is a need to assess the responses of the ecosystem to declining atmospheric pollution by monitoring the variations of chemical species in the various compartments of the forest ecosystem on a long temporal scale. In this study, we report on patterns and trends in throughfall deposition concentrations of inorganic N, dissolved organic N (DON) and C (DOC) over a 20-year (1995–2015) period in the LTER site -Val Masino (1190 m a.s.l.), a spruce forest, in the Central Italian Alps. The same chemical species were studied in the litter floor leachates and mineral soil solution, at three different depths (15, 40 and 70 cm), over a 10-year period (2005–2015). Inorganic N concentration was drastically reduced as throughfall and litter floor leachates percolated through the topsoil, where the measured mean values (2 µeq L-1) were much lower than the critical limits established for coniferous stands (14 µeq L-1). The seasonal temperature dependence of throughfall DOC and DON concentration suggests that the microbial community living on the needles was the main source of dissolved organic matter. Most of DOC and DON infiltrating from the litter floor were retained in the mineral soil. The rainfall amount was the only climatic factor exerting a control on DOC and N compounds in throughfall and forest floor leachates over a decadal period. Concentration of SO4 and NO3 declined by 50% and 26% respectively in throughfall deposition. Trends of NO3 and SO4 in forest floor leachates and mineral soil solution mirrored declining depositions. No trends in both DON and DOC concentration and in DOC/DON ratio in soil solutions were observed. These outcomes suggest that the declining NO3 and SO4 atmospheric inputs did not influence the dynamic of DON and DOC in the Val Masino forest. The results of this study are particularly relevant, as they are based on a comprehensive survey of all the main compartments of the forest ecosystem. Moreover, this kind of long-term research has rarely been carried out in the Alpine region.

Empirical relationships between temperature and nitrogen availability across North American forests

1992 ◽  
Vol 22 (5) ◽  
pp. 707-712 ◽  
Author(s):  
Xiwei Yin
Keyword(s):  
N Mineralization ◽  
Regional Scale ◽  
Mineral Soil ◽  
Published Data ◽  
N Availability ◽  
Net N Mineralization ◽  
Soil N ◽  
Litter Fall ◽  
Available N ◽  
N Pool

Published data were analyzed to examine whether nitrogen (N) availability varies along macroclimatic gradients in North America. Extractable N produced during 8-week aerobic laboratory incubation was used as an index of potential net N mineralization. Mean extractable N during the growing season in the forest floor plus top mineral soil was used as an index of the available N pool. Using multiple regression, potential net N mineralization was shown to increase with available N and with litter-fall N (R2 = 0.722). Available N increased with increasing total soil N and with decreasing mean January and July air temperatures (R2 = 0.770). These relationships appeared to hold also for deciduous and coniferous forests separately across regions. Results suggest that net N mineralization output under uniform temperature and moisture conditions can be generally expressed by variations of N input (litter fall) and the available soil N pool, and that the available soil N pool is predictable along a temperature gradient at a regional scale.

scholarly journals Alternate Strip Clearcutting in Upland Black Spruce: II. Factors Affecting Regeneration in First-cut Strips

1987 ◽  
Vol 63 (6) ◽  
pp. 439-445 ◽  
Author(s):  
John K. Jeglum
Keyword(s):  
Natural Regeneration ◽  
Black Spruce ◽  
Mineral Soil ◽  
Strip Width ◽  
Seedling Density ◽  
Factors Affecting ◽  
Topographic Position ◽  
Factors Influencing ◽  
Main Factors ◽  
Upper Slope

In a two-cut, alternate strip clearcutting system in upland black spruce, the main factors influencing black spruce regeneration in the first-cut strips were strip width, natural seeding period, amount of receptive seedbed and topographic position. In the three study areas, 80-m strips yielded over 60% stocking and over 7 500 seedlings per hectare with a 4-year natural seeding period. Narrower strips 40 m and 20 m wide showed increasing levels of reproduction. Four years of natural seeding gave better natural regeneration than two years. Seedling density and frequency in quadrats were correlated with the amount of receptive seedbed. Regeneration was more abundant on drainageways and lower slopes, and less abundant on upper slope and crest sites. For successful regeneration under similar climatic and physiographic conditions, strip widths should be no more than 80 m, and leave times no less than 3 years. It is essential to scarify the upland mineral soil sites, but scarification of lowland sites is not recommended, especially where there is abundant Sphagnum.

scholarly journals Effects of Changing Temperature on Gross N Transformation Rates in Acidic Subtropical Forest Soils

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 894
Author(s):  
Xiaoqian Dan ◽  
Zhaoxiong Chen ◽  
Shenyan Dai ◽  
Xiaoxiang He ◽  
Zucong Cai ◽  
...  
Keyword(s):  
Temperature Change ◽  
N Mineralization ◽  
Organic N ◽  
Mineralization Rate ◽  
Soil N ◽  
Autotrophic Nitrification ◽  
N Transformation ◽  
Gross N Transformation ◽  
Increasing Temperature ◽  
N Pool

Soil temperature change caused by global warming could affect microbial-mediated soil nitrogen (N) transformations. Gross N transformation rates can provide process-based information about abiotic–biotic relationships, but most previous studies have focused on net rates. This study aimed to investigate the responses of gross rates of soil N transformation to temperature change in a subtropical acidic coniferous forest soil. A 15N tracing experiment with a temperature gradient was carried out. The results showed that gross mineralization rate of the labile organic N pool significantly increased with increasing temperature from 5 °C to 45 °C, yet the mineralization rate of the recalcitrant organic N pool showed a smaller response. An exponential response function described well the relationship between the gross rates of total N mineralization and temperature. Compared with N mineralization, the functional relationship between gross NH4+ immobilization and temperature was not so distinct, resulting in an overall significant increase in net N mineralization at higher temperatures. Heterotrophic nitrification rates increased from 5 °C to 25 °C but declined at higher temperatures. By contrast, the rate of autotrophic nitrification was very low, responding only slightly to the range of temperature change in the most temperature treatments, except for that at 35 °C to 45 °C, when autotrophic nitrification rates were found to be significantly increased. Higher rates of NO3− immobilization than gross nitrification rates resulted in negative net nitrification rates that decreased with increasing temperature. Our results suggested that, with higher temperature, the availability of soil N produced from N mineralization would significantly increase, potentially promoting plant growth and stimulating microbial activity, and that the increased NO3− retention capacity may reduce the risk of leaching and denitrification losses in this studied subtropical acidic forest.

scholarly journals Technical Note: Reactivity of C1 and C2 organohalogens formation – from plant litter to bacteria

2012 ◽  
Vol 9 (10) ◽  
pp. 3721-3727 ◽  
Author(s):  
J. J. Wang ◽  
T. W. Ng ◽  
Q. Zhang ◽  
X. B. Yang ◽  
R. A. Dahlgren ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chloral Hydrate ◽  
Ecological Impact ◽  
Terrestrial Ecosystems ◽  
Plant Litter ◽  
Technical Note ◽  
Organic N ◽  
C Stocks ◽  
Wide Range ◽  
N Pool

Abstract. C1/C2 organohalogens (organohalogens with one or two carbon atoms) can have significant environmental toxicity and ecological impact, such as carcinogenesis, ozone depletion and global warming. Natural halogenation processes have been identified for a wide range of natural organic matter, including soils, plant and animal debris, algae, and fungi. Yet, few have considered these organohalogens generated from the ubiquitous bacteria, one of the largest biomass pools on earth. Here, we report and confirm the formation of chloroform (CHCl3) dichloro-acetonitrile (CHCl2CN), chloral hydrate (CCl3CH(OH)2) and their brominated analogues by direct halogenation of seven strains of common bacteria and nine cellular monomers. Comparing different major C stocks during litter decomposition stages in terrestrial ecosystems, from plant litter, decomposed litter, to bacteria, we found increasing reactivity for nitrogenous organohalogen yield with decreasing C/N ratio. Our results raise the possibility that natural halogenation of bacteria represents a significant and overlooked contribution to global organohalogen burdens. As bacteria are decomposers that alter the C quality by transforming organic matter pools from high to low C/N ratio and constitute a large organic N pool, the bacterial activity is expected to affect the C, N, and halogen cycling through natural halogenation reactions.

scholarly journals Soil disturbance by cut-to-length machinery on mid-grained soils

Silva Fennica ◽  
2019 ◽  
Vol 53 (2) ◽  
Author(s):  
Matti Sirén ◽  
Jari Ala-Ilomäki ◽  
Harri Lindeman ◽  
Jori Uusitalo ◽  
Kalle Kiilo ◽  
...  
Keyword(s):  
Water Content ◽  
Mineral Soil ◽  
Penetration Resistance ◽  
Soil Disturbance ◽  
Volumetric Water Content ◽  
Organic Layer ◽  
Measurement Point ◽  
Factors Affecting ◽  
Cumulative Mass ◽  
Best Fit

Factors affecting soil disturbance caused by harvester and forwarder were studied on mid-grained soils in Finland. Sample plots were harvested using a one-grip harvester. The harvester operator processed the trees outside the strip roads, and the remaining residues were removed to exclude the covering effect of residues. Thereafter, a loaded forwarder made up to 5 passes over the sample plots. The average rut depth after four machine passes was positively correlated to the volumetric water content at a depth of 0–10 cm in mineral soil, as well as the thickness of the organic layer and the harvester rut depth, and negatively correlated with penetration resistance at depths of both 0–20 cm and 5–40 cm. We present 5 models to predict forwarder rut depth. Four include the cumulative mass driven over a measurement point and combinations of penetration resistance, water content and the depth of organic layer. The fifth model includes harvester rut depth and the cumulative overpassed mass and provided the best fit. Changes in the penetration resistance (PR) were highest at depths of 20–40 cm. Increase in BD and VWC decreased PR, which increased with total overdriven mass. After four to five machine passes PR values started to stabilize.

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