Does the addition of litter from N-fixing Acacia mearnsii accelerate leaf decomposition of Eucalyptus globulus?

2007 ◽  
Vol 55 (5) ◽  
pp. 576 ◽  
Author(s):  
W. Xiang ◽  
J. Bauhus
Keyword(s):  
Species Interactions ◽  
Eucalyptus Globulus ◽  
N Cycling ◽  
Decomposition Rates ◽  
Mixed Species ◽  
Acacia Mearnsii ◽  
N Loss ◽  
Mixed Stands ◽  
Mixed Litter ◽  
Loss Of Mass

Nutrient cycling in mixed-species plant communities may be enhanced in comparison to what might be expected from the component species. In this study, we investigated (1) whether the admixing of nitrogen-rich litter from Acacia mearnsii can accelerate the decomposition of Eucalyptus globulus leaf litter and (2) whether eucalypt litter originating from mixed stands with acacias decomposes faster than litter from pure eucalypt stands. To address the first question, pure and mixed litter was incubated in the laboratory for 110 days at 25°C in the following proportions: 100%E, 75%E : 25%A, 50%E : 50%A, 25%E : 75%A and 100%A, where %E and %A refers to the proportion of eucalypt and acacia in the microcosms, respectively. Since mass loss and N loss of litter in the 50 : 50 mixture was higher than for pure eucalypt but not higher than for acacia, it appears that acacia litter accelerated decomposition of eucalypt litter but not vice versa. Decomposition rates increased with N concentration in the combined litters up to 1.1% N, above that point it remained constant. To address the second question, eucalypt litter from pure and mixed stands was incubated in microcosms. The loss of mass, N and P after 110 days was not different for eucalypt litter originating from mixed (75E : 25A, 50E : 50A, 25E : 75A) and pure (100E) plantations. Together, these studies suggest that admixture of A. mearnsii to E. globulus has the potential to accelerate decomposition and N cycling, and that the species interactions are most pronounced in the 50 : 50 mixture. Mixing of the two species in plantations has so far had no influence on the decomposability of eucalypt litter.

Nutrient cycling in a mixed-species plantation of Eucalyptus globulus and Acacia mearnsii

2005 ◽  
Vol 35 (12) ◽  
pp. 2942-2950 ◽  
Author(s):  
David I Forrester ◽  
Jürgen Bauhus ◽  
Annette L Cowie
Keyword(s):  
Nutrient Cycling ◽  
Biomass Production ◽  
Aboveground Biomass ◽  
Eucalyptus Globulus ◽  
N Availability ◽  
Species Replacement ◽  
Mixed Species ◽  
Acacia Mearnsii ◽  
Replacement Series ◽  
Silvicultural System

A doubling of aboveground biomass production has been observed in mixtures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman when compared with monocultures after 11 years of growth. This study examined to what extent increased nitrogen (N) availability and accelerated rates of nutrient cycling may contribute to increased growth in mixtures. Monocultures of E. globulus (E) and A. mearnsii (A) and mixtures of these species were planted in a species replacement series: 100% E, 75% E + 25% A, 50% E + 50% A, 25% E + 75% A, and 100% A. Litterfall mass increased with aboveground biomass production and was highest in 50:50 mixtures and lowest in monocultures. Owing to higher N concentrations of A. mearnsii litter, N contents of annual litterfall were at least twice as high in stands containing A. mearnsii (32-49 kg·ha–1·year–1) as in E. globulus monocultures (14 kg·ha–1·year–1). Stands with A. mearnsii also cycled higher quantities of phosphorus (P) in annual litterfall than E. globulus monocultures. This study demonstrated that mixing A. mearnsii with E. globulus increased the quantity and rates of N and P cycled through aboveground litterfall when compared with E. globulus monocultures. Thus, mixed-species plantations appear to be a useful silvicultural system to improve nutrition of eucalypts without fertilization.

Aboveground interactions and productivity in mixed-species plantations of Acacia mearnsii and Eucalyptus globulus

2004 ◽  
Vol 34 (3) ◽  
pp. 686-694 ◽  
Author(s):  
Jürgen Bauhus ◽  
Aaron P van Winden ◽  
Adrienne B Nicotra
Keyword(s):  
Eucalyptus Globulus ◽  
Net Photosynthesis ◽  
Stem Volume ◽  
Niche Separation ◽  
Mixed Species ◽  
Acacia Mearnsii ◽  
Replacement Series ◽  
Crown Volume ◽  
Lower Light ◽  
Productivity Gains

This study compared productivity in mixed-species plantations of Eucalyptus globulus ssp. pseudoglobulus (Naudin ex Maiden) Kirkpatr. and Acacia mearnsii de Wild with pure stands of each species and investigated how this might be explained by canopy stratification between species and changes in leaf characteristics of eucalypts. Investigations were carried out at a trial using the replacement series design, which consisted of the following combinations: 100% eucalypts (100%E), 75% eucalypts + 25% acacia (75%E:25%A), 50% eucalypts + 50% acacia (50%E:50%A), 25% eucalypts + 75% acacia (25%E:75%A), and 100% acacia (100%A). At 9.5 years, stem volume and biomass were highest in 50%E:50%A treatments. Canopy stratification occurred in all mixtures, with acacias in the lower and eucalypts in the upper canopy stratum. This and the increasing canopy light interception with increasing proportion of acacia in the mixture indicated that A. mearnsii is substantially more shade tolerant than E. globulus. Midcanopy foliage of E. globulus in the 50%E:50%A mixture had higher foliage nitrogen (N) but lower phosphorus (P) concentrations and lower light-saturated net photosynthesis rates (Amax) than those in the 100%E treatment. In addition, similar relationships between eucalypt crown volume and stem biomass across treatments indicated that eucalypt crowns were not more efficient in mixture. Our study indicates that the productivity gains in these mixtures may be partially attributable to aboveground niche separation between species.

Growth dynamics in a mixed-species plantation of Eucalyptus globulus and Acacia mearnsii

2004 ◽  
Vol 193 (1-2) ◽  
pp. 81-95 ◽  
Author(s):  
David I Forrester ◽  
Jürgen Bauhus ◽  
Partap K Khanna
Keyword(s):  
Eucalyptus Globulus ◽  
Growth Dynamics ◽  
Mixed Species ◽  
Acacia Mearnsii

Carbon allocation in a mixed-species plantation of Eucalyptus globulus and Acacia mearnsii

2006 ◽  
Vol 233 (2-3) ◽  
pp. 275-284 ◽  
Author(s):  
David I. Forrester ◽  
Jürgen Bauhus ◽  
Annette L. Cowie
Keyword(s):  
Eucalyptus Globulus ◽  
Carbon Allocation ◽  
Mixed Species ◽  
Acacia Mearnsii

scholarly journals ARTIFICIAL NEURAL NETWORKS (ANN) FOR HEIGHT ESTIMATION IN A MIXED-SPECIES PLANTATION OF Eucalyptus globulus LABILL AND Acacia mearnsii DE WILD

2021 ◽  
Vol 45 ◽  
Author(s):  
Gustavo Martins Soares ◽  
Luciana Duque Silva ◽  
Antonio Rioyei Higa ◽  
Augusto Arlindo Simon ◽  
Jackson Freitas Brilhante de São José
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Eucalyptus Globulus ◽  
Growth Patterns ◽  
Mixed Species ◽  
Acacia Mearnsii ◽  
Height Estimation ◽  
R Project ◽  
Artificial Neural ◽  
Stand Attributes

ABSTRACT The objective of this study is to evaluate the fit of Artificial Neural Networks (ANN) for height estimation and evaluation of the effects of consortium in a mixed-species plantation of Eucalyptus globulus (E) and Acacia mearnsii (A). The experiment was installed in 2005, on two farms in the municipality of Piratini - RS, where was planted the species Eucalyptus globulus (E) and Acacia mearnsii (A), in monoculture and mixed in simple lines (50%E:50%A - SL), and double lines (50%E:50%A - DL). The training and evaluation of the networks were made in R-project with the package neuralnet. All ANNs, from the simplest to the most complex, showed high values for Rŷy and low for Syx, BIAS and RMSE, with superior results in ANN 3, 4, and 6, which demonstrates that the information of DBHmin, DBHmean, and DBHmax were important stand attributes. Furthermore, the ANNs were able to capture the different growth patterns shown by the species in the different forms of consortiums, therefore is indicated for the height estimation in monocultures and mixed plantations of Eucalyptus globulus and Acacia mearnsii, and only one ANN would be necessary to represent the entire population.

scholarly journals European beech stem diameter grows better in mixed than in mono-specific stands at the edge of its distribution in mountain forests

2020 ◽  
Author(s):  
Hans Pretzsch ◽  
Torben Hilmers ◽  
Enno Uhl ◽  
Kamil Bielak ◽  
Michal Bosela ◽  
...  
Keyword(s):  
Species Interactions ◽  
European Beech ◽  
Growth Patterns ◽  
Silver Fir ◽  
Mountain Forests ◽  
Mixed Species ◽  
Mixed Stands ◽  
European Mountain ◽  
Vegetation Belt ◽  
Old Trees

Abstract Recent studies show that several tree species are spreading to higher latitudes and elevations due to climate change. European beech, presently dominating from the colline to the subalpine vegetation belt, is already present in upper montane subalpine forests and has a high potential to further advance to higher elevations in European mountain forests, where the temperature is predicted to further increase in the near future. Although essential for adaptive silviculture, it remains unknown whether the upward shift of beech could be assisted when it is mixed with Norway spruce or silver fir compared with mono-specific stands, as the species interactions under such conditions are hardly known. In this study, we posed the general hypotheses that the growth depending on age of European beech in mountain forests was similar in mono-specific and mixed-species stands and remained stable over time and space in the last two centuries. The scrutiny of these hypotheses was based on increment coring of 1240 dominant beech trees in 45 plots in mono-specific stands of beech and in 46 mixed mountain forests. We found that (i) on average, mean tree diameter increased linearly with age. The age trend was linear in both forest types, but the slope of the age–growth relationship was higher in mono-specific than in mixed mountain forests. (ii) Beech growth in mono-specific stands was stronger reduced with increasing elevation than that in mixed-species stands. (iii) Beech growth in mono-specific stands was on average higher than beech growth in mixed stands. However, at elevations > 1200 m, growth of beech in mixed stands was higher than that in mono-specific stands. Differences in the growth patterns among elevation zones are less pronounced now than in the past, in both mono-specific and mixed stands. As the higher and longer persisting growth rates extend the flexibility of suitable ages or size for tree harvest and removal, the longer-lasting growth may be of special relevance for multi-aged silviculture concepts. On top of their function for structure and habitat improvement, the remaining old trees may grow more in mass and value than assumed so far.

scholarly journals Occurrence of benthic microbial nitrogen fixation coupled to sulfate reduction in the seasonally hypoxic Eckernförde Bay, Baltic Sea

2012 ◽  
Vol 9 (6) ◽  
pp. 6489-6533 ◽  
Author(s):  
V. J. Bertics ◽  
C. R. Löscher ◽  
I. Salonen ◽  
A. W. Dale ◽  
R. A. Schmitz ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sulfate Reduction ◽  
N2 Fixation ◽  
Bottom Water ◽  
N Cycling ◽  
Microbial Processes ◽  
Desulfovibrio Vulgaris ◽  
N Loss ◽  
Column Temperature ◽  
Oxygen Concentrations

Abstract. Despite the worldwide occurrence of marine hypoxic regions, benthic nitrogen (N) cycling within these areas is poorly understood and it is generally assumed that these areas represent zones of intense fixed N loss from the marine system. Sulfate reduction can be an important process for organic matter degradation in sediments beneath hypoxic waters and many sulfate-reducing bacteria (SRB) have the genetic potential to fix molecular N (N2). Therefore, SRB may supply fixed N to these systems, countering some of the N lost via microbial processes such as denitrification and anaerobic ammonium oxidation. The objective of this study was to evaluate if N2-fixation, possibly by SRB, plays a role in N cycling within the seasonally hypoxic sediments from Eckernförde Bay, Baltic Sea. Monthly samplings were performed over the course of one year to measure N2-fixation and sulfate reduction rates, to determine the seasonal variations in bioturbation (bioirrigation) activity and important benthic geochemical profiles, such as sulfur and N compounds, and to monitor changes in water column temperature and oxygen concentrations. Additionally, at several time points, rates of benthic denitrification were also measured and the active N-fixing community was examined via molecular tools. Integrated rates of N2-fixation and sulfate reduction showed a similar seasonality pattern, with highest rates occurring in August (approx. 22 and 880 nmol cm−3 d−1 of N and SO42−, respectively) and October (approx. 22 and 1300 nmol cm−3 d−1 of N and SO42−, respectively), and lowest rates occurring in February (approx. 8 and 32 nmol cm−3 d−1 of N and SO42−, respectively). These rate changes were positively correlated with bottom water temperatures and previous reported plankton bloom activities, and negatively correlated with bottom water oxygen concentrations. Other variables that also appeared to play a role in rate determination were bioturbation, bubble irrigation and winter storm events. Molecular analysis demonstrated the presence of nifH sequences related to two known N2-fixing SRB, namely Desulfovibrio vulgaris and Desulfonema limicola, supporting the hypothesis that some of the nitrogenase activity detected may be attributed to SRB. Denitrification appeared to follow a similar trend as the other microbial processes and the ratio of denitrification to N2-fixation ranged from 6.8 in August to 1.1 in February, indicating that in February, the two processes are close to being in balance in terms of N loss and N gain. Overall, our data show that Eckernförde Bay represents a complex ecosystem where numerous environmental variables combine to influence benthic microbial activities involving N and sulfur cycling.

scholarly journals Microbial ecosystem dynamics drive fluctuating nitrogen loss in marine anoxic zones

2019 ◽  
Vol 116 (15) ◽  
pp. 7220-7225 ◽  
Author(s):  
Justin L. Penn ◽  
Thomas Weber ◽  
Bonnie X. Chang ◽  
Curtis Deutsch
Keyword(s):  
Competitive Advantage ◽  
Ocean Circulation ◽  
Species Interactions ◽  
Nitrogen Loss ◽  
Regional Scale ◽  
Climate Impacts ◽  
Ecosystem Dynamics ◽  
N Loss ◽  
Microbial Ecosystem ◽  
Anoxic Zones

The dynamics of nitrogen (N) loss in the ocean’s oxygen-deficient zones (ODZs) are thought to be driven by climate impacts on ocean circulation and biological productivity. Here we analyze a data-constrained model of the microbial ecosystem in an ODZ and find that species interactions drive fluctuations in local- and regional-scale rates of N loss, even in the absence of climate variability. By consuming O2to nanomolar levels, aerobic nitrifying microbes cede their competitive advantage for scarce forms of N to anaerobic denitrifying bacteria. Because anaerobes cannot sustain their own low-O2niche, the physical O2supply restores competitive advantage to aerobic populations, resetting the cycle. The resulting ecosystem oscillations induce a unique geochemical signature within the ODZ—short-lived spikes of ammonium that are found in measured profiles. The microbial ecosystem dynamics also give rise to variable ratios of anammox to heterotrophic denitrification, providing a mechanism for the unexplained variability of these pathways observed in the ocean.

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