scholarly journals Importance of the Local Environment on Nutrient Cycling and Litter Decomposition in a Tall Eucalypt Forest

Forests ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 340 ◽  
Author(s):  
Jessie C. Buettel ◽  
Elise M. Ringwaldt ◽  
Mark J. Hovenden ◽  
Barry W. Brook
Keyword(s):  
Nitrogen Availability ◽  
Average Distance ◽  
Nitrogen Concentration ◽  
Basal Area ◽  
Field Measurements ◽  
Local Environment ◽  
Forest Litter ◽  
Nitrogen Fixing ◽  
Acacia Dealbata ◽  
Eucalypt Forest

The relative abundance of nitrogen-fixing species has been hypothesised to influence tree biomass, decomposition, and nitrogen availability in eucalypt forests. This prediction has been demonstrated in experimental settings (two-species mixtures) but is yet to be observed in the field with more realistically complex communities. We used a combination of (a) field measurements of tree-community composition, (b) sampling of soil from a subset of these sites (i.e., the local environment), and (c) a decomposition experiment of forest litter to examine whether there is a local-scale effect of the nitrogen-fixing Acacia dealbata Link (presence and abundance) on nitrogen availability, and whether increases in this essential nutrient led to greater biomass of the canopy tree species, Eucalyptus obliqua L’Hér. Average A. dealbata tree size was a significant predictor of forest basal area in 24 plots (12% deviance explained) and, when combined with average distance between trees, explained 29.1% variance in E. obliqua biomass. However, static patterns of local nitrogen concentration were unrelated to the presence or size of A. dealbata, despite our experiments showing that A. dealbata leaf litter controls decomposition rates in the soil (due to three times higher N). Such results are important for forest management in the context of understanding the timing and turnover of shorter-lived species like acacias, where higher N (through either litter or soil) might be better detected early in community establishment (when growth is faster and intraspecific competition more intense) but with that early signal subsequently dissipated.

Nitrogen fixation makes biomass allocation to roots independent of soil nitrogen supply

2007 ◽  
Vol 85 (9) ◽  
pp. 787-793 ◽  
Author(s):  
John H. Markham ◽  
Corinthe Zekveld
Keyword(s):  
Nitrogen Fixation ◽  
Plant Growth ◽  
Biomass Allocation ◽  
Soil Nitrogen ◽  
Nitrogen Availability ◽  
Nitrogen Concentration ◽  
Nitrogen Fixing ◽  
Soil Nitrogen Availability ◽  
Least Squares Fit ◽  
Allocation Patterns

Biomass allocation patterns in plants are known to be affected by soil nitrogen availability. Since nitrogen availability can depress symbiotic nitrogen fixation, and nitrogen fixation can make plant growth independent of soil nitrogen availability but is energetically costly, it is unclear how allocation patterns in nitrogen-fixing species should respond to variation in soil nitrogen availability. We examined the effect of nitrogen source and concentration on the growth and allocation patterns in the nitrogen-fixing shrub Alnus viridis subsp. crispa (Aiton) Turrill. Plants were grown with either NH4+-N or NO3–-N at a range of low N concentrations, from 0 to 2 mmol·L–1, and either inoculated with Frankia or not. Plants without nodules had 25.l% lower biomass and had double the allocation to roots at all but the 2 mmol·L–1 nitrogen concentration. Even though nodulated plants increased growth with nitrogen concentration, allocation to roots as a fraction of total biomass did not vary in these plants, suggesting increased growth resulted from more efficient nitrogen acquisition. Allocation to roots was a significant predictor of plant growth in non-nodulated plants (r2 = 0.318, for linear least squares fit with log mass) but not for nodulated plants (r2 = 0.108). As nitrogen concentrations increased, allocation to nodules, specific nodule numbers, and the proportion of nitrogen fixed by the plants decreased, demonstrating a shift to soil nitrogen use.

Soil nitrogen concentration and Juglansnigra growth in mixed plots with nitrogen-fixing Alnus, Elaeagnus, Lespedeza, and Robinia species

1984 ◽  
Vol 14 (6) ◽  
pp. 864-868 ◽  
Author(s):  
John M. Friedrich ◽  
Jeffrey O. Dawson
Keyword(s):  
Soil Nitrogen ◽  
Black Locust ◽  
Nitrogen Concentration ◽  
Basal Area ◽  
Nitrogen Fixing ◽  
Autumn Olive ◽  
Total Soil ◽  
Nitrogen Concentrations ◽  
And Control ◽  
Total Soil Nitrogen

Soil samples and black walnut (Juglansnigra L.) measurements were taken in plots of a 14-year-old plantation combining two walnut spacings with four interplanted nitrogen-fixing species and a control, lnterplantings of walnut with black locust (Robiniapseudoacacia L.) and autumn-olive (Elaeagnusumbellata Thunb.) had the highest total soil nitrogen concentrations in the top 30 cm of soil, followed by European alder (Alnusglutinosa L. [Gaertn.]), lespedeza clover (Lespedezastriata [Thunb.] Hook & Arn.), and control plots. Soil nitrogen concentrations were greatest in the surficial 6 cm of soil. At the closer, 3.7- by 4.9-m spacing in autumn-olive plots where walnut growth and competition were greatest, and at both spacings in plots with girdled black locust, nitrogen concentrations in the soil were especially high. This is consistent with speculation that recent stress on autumn-olive from walnut competition and stress on locust from past stem girdling resulted in increased inputs of nitrogen into soil. Walnut size was greatest by far in autumn-olive plots, where the spreading form of the shrub afforded soil shading and weed control. Walnut size was generally greater in mixed plots at the wider 3.7 m by 9.8 m spacing, where walnut competition with itself was least. However, walnut basal area was not strongly correlated with mean total soil nitrogen concentration of the top 30 cm of soil in a plot (r2 = 0.32 at closer walnut spacings), suggesting that the net accretion of nitrogen in soil accounted only in part for measured differences in walnut growth in mixed plantings with nitrogen-fixing plants.

Nitrogen cycling in a Venezuelan tropical seasonally flooded forest: soil nitrogen mineralization and nitrification

1994 ◽  
Vol 10 (3) ◽  
pp. 399-416 ◽  
Author(s):  
Barrios E. ◽  
Herrera R.
Keyword(s):  
Soil Nitrogen ◽  
Nitrogen Availability ◽  
Inorganic Nitrogen ◽  
Nitrogen Concentration ◽  
Ammonium Nitrogen ◽  
Wet Season ◽  
Flooded Forest ◽  
Nitrogen Concentrations ◽  
Minimum Stress ◽  
Seasonally Flooded

ABSTRACTSeasonally flooded forests represent a transition between terrestrial and aquatic ecosystems. The Mapire river, a tributary of the Orinoco river, floods its surrounding forests during the wet season (May–December). The soils are very acid and the total nitrogen concentration (0.1%) is only half that found in nearby soils flooded by Orinoco waters. Ammonium-nitrogen predominates in the soil during the flooded period while nitrate-nitrogen concentrations are higher in the dry period. Wide fluctuations in the inorganic nitrogen fractions did not considerably affect the annual course of soil nitrogen.The predominance of mineralization versus nitrification (56 and 5 μgsoil month−1respectively) and possibly the synchronization of nitrogen availability with plant demand could be considered as nitrogen conserving mechanisms.In synchrony with the hydrologic cycle, the seasonally flooded forest studied shows a nitrogencycle where inputs and accumulation are maximized when the system is under minimum stress (dry season). During flooding, the system enters a period of dormancy making minimal use of nutrient and energy to avoid or tolerate anaerobiosis.

Macroplastic Debris Transfer in Rivers: A Travel Distance Approach 

2021 ◽  
Author(s):  
Robert Newbould ◽  
Mark Powell ◽  
Mick Whelan
Keyword(s):  
Average Distance ◽  
Field Measurements ◽  
River System ◽  
Tracer Experiment ◽  
Travel Distance ◽  
Distance Distributions ◽  
Different Types ◽  
Meander Bends ◽  
Distance Approach ◽  
Travel Distances

<p>Plastic accumulation in the marine environment is a major concern given the harmful effects and longevity of plastics at sea. Although rivers significantly contribute to flux of plastic to marine systems, plastic transport in rivers remains poorly understood and estimates of riverine plastic flux derived from field measurements and modelling efforts are highly uncertain. In this study, a new probabilistic model of plastic transport in rivers is presented which describes the main processes controlling displacement to predict the statistical distribution of travel distances for individual items of buoyant macroplastic debris. Macroplastic transport is controlled by retention in temporary stores (or traps) created by vegetation, bank roughness elements and other obstacles. The behaviour of these traps is represented in the model via a series of Bernoulli trials conducted in a Monte Carlo simulation framework. The probability of retention or release from traps is described using physical characteristics such as the type of vegetation, channel width or channel sinuosity index. The model was calibrated using a tracer experiment with six replicates, conducted in a small 1.1 km river reach. For each replicate, 90 closed air-filled plastic bottles were injected at the upstream end of the reach and the location of each bottle was recorded several times over a 24-hour period. Bottles were chosen as ‘model’ macroplastic litter items given their high usage and littering volume. Travel distances were low (the average distance travelled over 24 hours was 231 m and no bottles travelled more than 1.1 km, the length of the study reach) and variable (the coefficient of variation for the replicates ranged between 0.54 and 1.41). The travel distance distributions were controlled by the location and characteristics of discrete traps. The numerical model described the observed travel distance distributions reasonably well (particularly the trapping effect of overhanging trees and flow separation at meander bends), which suggests that modelling plastic transport for longer reaches and even whole catchments using a stochastic travel distance approach is feasible. The approach has the potential to improve estimates of total river plastic flux to the oceans, although significant knowledge gaps remain (e.g. the rate and location of plastic supply to river systems, the transport behaviours of different types of plastic debris in rivers and the effectiveness of different traps in different types of river system).</p>

Chaparral growth-ring analysis as an indicator of stand biomass development

2016 ◽  
Vol 25 (10) ◽  
pp. 1086 ◽  
Author(s):  
Kellie A. Uyeda ◽  
Douglas A. Stow ◽  
John F. O'Leary ◽  
Christina Tague ◽  
Philip J. Riggan
Keyword(s):  
Growth Ring ◽  
Basal Area ◽  
Biomass Accumulation ◽  
Field Measurements ◽  
Solar Irradiation ◽  
Annual Precipitation ◽  
Total Biomass ◽  
Growth Rings ◽  
Close Relationship ◽  
Long Time

Chaparral wildfires typically create even-aged stands of vegetation that grow quickly in the first 2 decades following a fire. Patterns of this growth are important for understanding ecosystem productivity and re-establishment success, but are logistically challenging to measure over long time periods. We tested the utility of a novel method of using shrub growth rings to estimate stand-level biomass accumulation at an annual time scale in southern California chaparral. We examined how temporal variation in precipitation and spatial variation in solar irradiation influence that accumulation. Using field measurements and a relationship between stem basal area and aboveground biomass, we estimated current biomass levels in an 11-year-old chaparral stand, and used growth-ring diameters to estimate growth in each year from age 4 to 11 years. We found that annual growth as measured by shrub growth rings tracked closely with patterns of annual precipitation, but not with time since fire. Solar irradiation was not found to be a significant covariate with total biomass by plot, possibly due to sampling area limitations. The close relationship of annual biomass accumulation with annual precipitation indicates that shrub growth-ring measurements can provide a useful metric of stand-level recovery.

scholarly journals Seasonal effects of wastewater to the water quality of the Caeté river estuary, Brazilian Amazon

2010 ◽  
Vol 82 (2) ◽  
pp. 467-478 ◽  
Author(s):  
Luci C.C. Pereira ◽  
Marcela C. Monteiro ◽  
Danielly O. Guimarães ◽  
Jislene B. Matos ◽  
Rauquírio M. da Costa
Keyword(s):  
Water Quality ◽  
River Estuary ◽  
Field Measurements ◽  
Local Environment ◽  
Local Economy ◽  
Seasonal Effects ◽  
Economic Activities ◽  
Dry Period ◽  
Biological Resources

Bragança's socioeconomic situation is highly dependent on estuarine and marine biological resources that are influenced by tidal cycles and climatology. Field measurements (hydrological, hydrodynamic and microbiological variables) were taken in the most urbanized zone from Caeté estuary to characterise the quality of the local environment. During the dry period, the estuary was more eutrophic and presented the highest temperature (30.5 °C in Oct./06), salinity (17 psu in Feb./07), pH (8.24 in Feb./07) and fecal coliform (> 1000 MPN/100 ml in Dec./06 and Feb./07) values. The phytoplankton Cyclotella meneghiniana, Coscinodiscus centralis and other r-strategist species were observed. The lack of basic hydric canalization was responsible for the local contamination, especially during the dry period when more concentrated wastewater from the city was emitted into the estuary, showing the human influence on the reduction of local estuarine water quality. In Bragança, the fishery is considered one of the main economic activities so, this contamination is worrisome because a large part of the local economy depends on biological resources and, thus, the contamination could negatively affect the environmental health of this Amazon ecosystem.

A Population Level Temperature-Dependent Model of Seedling Johnsongrass (Sorghum halepense) Flowering

Weed Science ◽  
1989 ◽  
Vol 37 (3) ◽  
pp. 471-477 ◽  
Author(s):  
David C. Bridges ◽  
James M. Chandler
Keyword(s):  
Water Availability ◽  
Nitrogen Availability ◽  
Nitrogen Concentration ◽  
Population Level ◽  
Effect Of Temperature ◽  
Weibull Function ◽  
Data Sets ◽  
Data Set ◽  
Independent Field ◽  
Temperature Dependent Model

A population level, two-compartment, temperaturedependent model that predicts date of seedling johnsongrass flowering was formulated. The model consisted of a fourparameter poikilotherm rate equation to describe development rate as a function of temperature and a temperature-independent Weibull function to distribute flowering times for the population. Experiments were conducted to determine the effect of temperature, nitrogen availability, and water availability on development of seedling johnsongrass. Development was most sensitive to temperature while the effect of nitrogen concentration and water availability was minimum and inconsistent. The model was tested against three independent field data sets and provided accurate prediction of flowering dates for each data set.

The accumulation of terpenoid oils does not incur a growth cost in Eucalyptus polybractea seedlings

2006 ◽  
Vol 33 (5) ◽  
pp. 497 ◽  
Author(s):  
Drew J. King ◽  
Roslyn M. Gleadow ◽  
Ian E. Woodrow
Keyword(s):  
Nitrogen Availability ◽  
Nitrogen Concentration ◽  
Leaf Nitrogen ◽  
Primary Metabolism ◽  
Oil Accumulation ◽  
Oil Concentration ◽  
Net Assimilation ◽  
Positive Correlations ◽  
The Cost ◽  
The Impact

The deployment of secondary metabolites, such as terpenes, as anti-herbivore defences is thought to be costly for plants in terms of primary metabolism. Moreover, it is assumed that the cost of this deployment is modified by resource availability. In this study we examined the impact of terpenoid oil accumulation on the growth of Eucalyptus polybractea R.T.Baker seedlings from four maternal half-sib families, under conditions of sufficient and limiting nitrogen. The foliar oil concentration measured was extremely variable, varying almost 20-fold to a maximum of 13% (w / DW). Oil concentration was higher in plants grown under high nitrogen than in low-nitrogen plants, and it was positively correlated with foliar nitrogen concentration. Oil concentration was related to maternal concentration, although this relationship was weak because of the variation encountered. The composition of oil, dominated by monoterpenes, was also extremely variable, although this variation could not be adequately explained by either nitrogen availability or the seedling parentage. Importantly, we detected no negative correlations between oil concentration and relative growth rate (RGR), net assimilation rate (NAR), or leaf nitrogen productivity (LNP). Rather, under nitrogen limiting conditions, positive correlations were detected between oil concentration and all three indices. We conclude that oil accumulation is associated with factors that promote growth and if there is a cost to oil deployment, it could not be detected using the experimental design employed here.

Testing the impact of community composition on the productivity of a cool temperate eucalypt forest: the Australian Forest Evenness Experiment (AFEX)

2020 ◽  
Vol 68 (4) ◽  
pp. 310
Author(s):  
Melissa R. Gerwin ◽  
Rose Brinkhoff ◽  
Travis Britton ◽  
Meagan Porter ◽  
Ruth K. Mallett ◽  
...  
Keyword(s):  
Community Composition ◽  
Field Experiments ◽  
Forest Growth ◽  
Plant Community Composition ◽  
Ecological Processes ◽  
Acacia Dealbata ◽  
Carbon Sequestration Potential ◽  
Eucalypt Forest ◽  
Sequestration Potential ◽  
The Impact

Understanding the factors controlling productivity is crucial for modelling current and predicting future forest growth and carbon sequestration potential. Although abiotic conditions exert a strong influence on productivity, it is becoming increasingly evident that plant community composition can dramatically influence ecosystem processes. However, much of our understanding of these processes in forests comes from correlative studies or field experiments in short-statured, short-lived vegetation. Here, we present the background, design and implementation success of the Australian Forest Evenness Experiment (AFEX), which was designed to investigate the influence of community composition on the processes that contribute to forest productivity. Eighty 25 × 25-m plots, covering 5 ha in a logged, burnt forest coupe in south-eastern Tasmania were sown with four tree species, namely Eucalyptus delegatensis R.T.Baker, E. regnans F.Muell., Acacia dealbata Link and Pomaderris apetala Labill., in varying combinations to provide a range of evenness levels with each of the four species as target dominant. Despite some differences between sown composition and realised composition 1year after sowing, a substantial range of community evenness and local neighbourhood densities and compositions existed in the experiment. Thus, this site provides a unique opportunity to determine the influence of local neighbourhood composition on a range of ecological processes.

The response to moisture and defoliation stresses, and traits for resilience of perennial grasses on the Northern Tablelands of New South Wales, Australia

2003 ◽  
Vol 54 (9) ◽  
pp. 903 ◽  
Author(s):  
S. P. Boschma ◽  
M. J. Hill ◽  
J. M. Scott ◽  
G. G. Rapp
Keyword(s):  
Festuca Arundinacea ◽  
Plant Biomass ◽  
Nitrogen Concentration ◽  
Perennial Grass ◽  
Basal Area ◽  
Perennial Grasses ◽  
Rooting Depth ◽  
Grass Species ◽  
Severe Drought ◽  
Moderate Drought

A field experiment was conducted to study the effects of defoliation and moisture stresses on perennial pasture grasses and to identify traits associated with their resilience. The experiment, conducted near Armidale on the Northern Tablelands of NSW, studied 4 introduced perennial grass species (Phalaris aquatica, Festuca arundinacea, Dactylis glomerata, and Lolium perenne) and 2 native grass species (Microlaena stipoides and Austrodanthonia richardsonii) subjected to 3 moisture regimes (non-stress moisture, moderate drought, and severe drought) and 2 defoliation intensities (severe and moderate). Basal area, herbage mass, phenological growth stage, nitrogen concentration, root mass, and rooting depth were compared over 2 independent 6-month periods: spring–summer (1 September 1994–28 February 1995) and summer–autumn (1 December 1994–31 May 1995). Multiple regression was used to determine which traits were important for determining plant resilience.The differences between species and their respective responses were evident in the traits measured. In general, basal area tended to increase over summer and show little change during autumn. Severe defoliation stimulated plant growth, resulting in higher harvested herbage mass than from those moderately defoliated. Reproductive development was suppressed by severe drought and reduced by moderate drought. Severe defoliation suppressed flowering of Dactylis and Lolium at both drought intensities, compared with moderate defoliation. Phalaris, Festuca, and Austrodanthonia were the deepest rooting species during spring–summer, and Dactylis the shallowest. All species had similar rooting depths during summer–autumn, with those under severe and moderate drought having the deepest and shallowest rooting, respectively.Carbohydrate reserves and basal area were important traits for determining plant resilience during spring–summer. During summer–autumn, maintaining basal area and plant biomass through moderate grazing was important for resilience.

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