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  • Eucalyptus Globulus
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  • 1
    Language: English
    In: Forest Ecology and Management, 2006, Vol.233(2), pp.275-284
    Description: Aboveground biomass was twice as high in mixtures of and when compared to monocultures after 11 years. This was attributed to increased nutrient availability and accelerated rates of N and P cycling in mixtures. This study examined whether the increase in aboveground biomass production was associated with an increase in total productivity (both above- and belowground), a change in C partitioning (from below to aboveground) or both. Total annual belowground C allocation (TBCA) was determined during year 11 in a mixed-species trial near Cann River, southeastern Australia. Monocultures of (100%E) and (100%A) and mixtures of these species (50%E:50%A) were planted in a replacement series. Using a conservation of mass approach, TBCA was estimated as soil carbon dioxide (CO ) efflux C minus the C input from aboveground litter plus changes in the C stored in soil, roots and the forest floor litter layer. Aboveground net primary production (ANPP) was also estimated to enable comparison of ratios of above and belowground fluxes between treatments. TBCA ranged from 14.6 to 16.3 Mg C ha year and was not significantly different in 100%E, 50%E:50%A and 100%A. Higher ratios of ANPP:TBCA in the mixtures (0.41) than in either monoculture (100%A:0.28 100%E:0.31) indicated that trees in mixture partitioned a lower proportion of assimilated C belowground than those in monocultures. Since the mixture was as productive as monocultures belowground but more productive aboveground, it appears to be more productive overall and thus have the potential to increase C sequestration above that of monocultures.
    Keywords: Acacia Mearnsii ; Carbon Allocation ; Carbon Sequestration ; Eucalyptus Globulus ; Mixed-Species Plantation ; Soil Respiration ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 2
    Language: English
    In: Forest Ecology and Management, 2005, Vol.209(1), pp.147-155
    Description: Mixed plantations of a species with a nitrogen-fixing tree species can produce significantly higher quantities of aboveground biomass than monocultures. However, if species or sites are not chosen correctly, one species may suppress the growth of the other and mixtures may be less productive than monocultures. Based on a study of and , this paper discusses the species attributes and site factors that should be considered to improve the probability of increasing biomass production using mixed-species plantations. In an 11-year-old mixed-species trial of and in southeastern Australia aboveground biomass production was twice as high in mixtures containing 50% and 50% than in monocultures. There are three main types of interactions that led to this growth outcome: competition, competitive reduction and facilitation. Facilitation occurred as fixed significant quantities of N, both in monoculture and when mixed with . In addition, not only rates of N but also those of P cycling through litterfall were significantly higher in mixed stands than monocultures, pointing to the importance of selecting a nitrogen-fixing species that is capable of N fixation and subsequent fast nutrient cycling through litterfall. Mixed stands developed stratified canopies, such that eventually overtopped after 9 years. This resulted in an increase in light capture at the stand level and a reduction in competition for light for , a relatively shade intolerant species. This illustrates the importance of selecting species based on their height growth dynamics and relative shade tolerances, to ensure that neither species is suppressed by the other and that the less tolerant species is not overtopped by the more shade tolerant species. In addition to species attributes, site factors, such as soil nitrogen, phosphorus and water availability, play an important role in the interactions and processes occurring in mixtures. In a pot trial containing monocultures and mixtures of and , mixtures produced more biomass than monocultures of either species at low levels of N fertiliser. However, at high levels of N fertiliser suppressed and the biomass production of mixtures was not significantly different to that of monocultures. This suggests that mixtures should only be planted on sites where the processes and interactions between species will increase the availability of, or reduce competition for, a major limiting resource for growth at that site. The accurate prediction of successful mixed-species combinations and sites is difficult due to the limited number of studies on mixtures. A mechanistic approach is required to examine the interactions and processes that occur in mixtures and to demonstrate why certain combinations are successful on some sites and not others.
    Keywords: Mixed-Species Plantations ; Eucalyptus Globulus ; Acacia Mearnsii ; Competition ; Nutrient Cycling ; Stratification ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 3
    Language: English
    In: Forest Ecology and Management, 2004, Vol.193(1), pp.81-95
    Description: Previous work has shown greater productivity in mixed than in mono-specific stands of Eucalyptus globulus and Acacia mearnsii at age 3 and 6.5 years. To assess how long the synergistic effects of acacias on eucalypts in mixed stands would last, and what future trajectory growth might take, we investigated the growth dynamics of mixed and mono-specific plantations over the first 11 years since establishment. Monocultures of E. globulus (E) and A. mearnsii (A) and mixtures (75E:25A, 50E:50A, 25E:75A) of these species were planted following a species replacement series. At the tree level, eucalypt and acacia heights, diameters, volumes and above-ground biomass were higher in mixtures than in monocultures 3–4 years after planting. Similarly, at the stand level, volumes and above-ground biomass were significantly greater in mixtures than monocultures after 3–4 years. The difference in productivity between mixed plots and mono-specific eucalypt stands increased with time from 3 to 11 years after establishment. Litterfall was higher in the mixed stands than the monocultures, and this led to an increase in N and P cycling through litterfall in stands containing A. mearnsii . The study indicated that above-ground biomass accumulation in E. globulus plantations can be increased by acacia admixture. This can partially be explained by canopy stratification and improved nutrition of eucalypts. Although the biomass production in acacias peaked early, the synergistic effect of the acacias appears to be long lasting as was indicated by the increasing differences between mixed and pure stands.
    Keywords: Acacia Mearnsii ; Competition ; Eucalyptus Globulus ; Mixed-Species Plantations ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 4
    Language: English
    In: Plant and Soil, 2006, Vol.280(1), pp.267-277
    Description: Significant increases in aboveground biomass production have been observed in mixed plantations of Eucalyptus globulus and Acacia mearnsii when compared to monocultures. However, this positive growth response may be enhanced or lost with changes in resource availability. Therefore this study examined the effect of the commonly limiting resources soil N, P and moisture on the growth of E. globulus and A. mearnsii mixtures in a pot trial. Pots containing two E. globulus plants, two A. mearnsii plants or one of each species were treated with high and low levels of N and P fertiliser. After 50 weeks, E. globulus plants grew more aboveground biomass in mixtures than monocultures. A. mearnsii were larger in mixtures only at low N, where both species were similar in size and the combined aboveground biomass of both species in mixture was greater than that of monocultures. At high N and both high and low levels of P fertiliser E. globulus appeared to dominate and suppress A. mearnsii. In these treatments, the faster growth of E. globulus in mixture did not compensate the reduced growth of A. mearnsii , so mixtures were less productive than (or not significantly different from) E. globulus monocultures. The greater competitiveness of E. globulus in these situations may have resulted from its higher N and P use efficiency and greater growth response to N and P fertilisers compared to A. mearnsii. This trial indicates that the complex interactions between species in mixtures, and thus the success of mixed plantations, can be strongly influenced by site factors such as the availability of N and P.
    Keywords: Acacia mearnsii ; competition ; Eucalyptus globulus ; facilitation ; mixed-species
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 5
    Language: English
    In: Canadian Journal of Forest Research, 03/2004, Vol.34(3), pp.686-694
    Description: 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.Cette étude visait à déterminer dans quelle mesure l'augmentation de productivité dans des plantations mixtes d'Eucalyptus globulus ssp. pseudoglobulus (Naudin ex Maiden) Kirkpatr. et d'Acacia mearnsii de Wild, comparativement à des peuplements purs de chaque espèce, peut s'expliquer par la stratification du couvert de ces espèces et les changements dans les caractéristiques foliaires des eucalyptus. Les travaux de recherche ont été réalisés dans un essais où avait été établi un dispositif contenant une série de remplacement composée des combinaisons suivantes : 100% eucalyptus (100%E), 75% eucalyptus + 25% acacia (75%E:25%A), 50% eucalyptus + 50% acacia (50%E:50%A), 25% eucalyptus + 75% acacia (25%E:75%A) et 100% acacia (100%A). À l'âge de 9,5 ans, la biomasse et le volume de la tige étaient les plus élevés dans le traitement 50%E:50%A. La stratification du couvert a été observée dans toutes les combinaisons : les acacia occupant la strate inférieure et les eucalyptus la strate supérieure. Ce fait et l'interception croissante de la lumière par le couvert avec la proportion croissante d'acacia dans le mélange indiquent qu'A. mearnsii est une espèce beaucoup plus tolérante qu'E. globulus. Le feuillage d'E. globulus situé au milieu du couvert dans le mélange 50%E:50%A avait une concentration plus élevée de N mais plus faible de P et un taux de photosynthèse nette à saturation lumineuse (Amax) plus faible que dans le traitement 100%E. De plus, des relations semblables entre le volume de cime et la biomasse de la tige de l'eucalyptus, quel que soit le traitement, indiquent que les cimes d'euca lyp tus ne sont pas plus efficaces en mélange. Cette étude montre que les gains de productivité dans ces mélanges pourraient être partiellement attribuables à la spécificité de la niche épigée de ces deux espèces.[Traduit par la Rédaction]
    Keywords: ModÈ ; Le;
    ISSN: 0045-5067
    E-ISSN: 1208-6037
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  • 6
    Language: English
    In: Canadian Journal of Forest Research, 12/2005, Vol.35(12), pp.2942-2950
    Description: 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 super(- 1)·year super(-1)) as in E. globulus monocultures (14 kg·ha super(-1)·year super(-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.Original Abstract: Apres 11 annees de croissance, la production de biomasse aerienne a double avec des melanges d'Eucalyptus globulus Labill. et d'Acacia mearnsii de Wildeman comparativement a des monocultures. Cette etude a examine dans quelle mesure la disponibilite accrue d'azote (N) et l'acceleration du taux de recyclage des nutriments ont pu contribuer a l'augmenta tion de la croissance en peuplements melanges. Des monocultures d'E. globulus (E) et d'A. mearnsii (A) et des melanges de ces deux especes ont ete plantes dans une serie de remplacement de ces especes : 100 % E, 75 % E : 25 % A, 50 % E : 50 % A, 25 % E : 75 % A et 100 % A. la masse de chute de litiere a augmente avec la production de biomasse aerienne et etait la plus elevee dans le melange 50:50 et la plus faible dans les monocultures. A cause de la concentration en N plus elevee de la litiere d'A. mearnsii, le contenu en N de la chute annuelle de litiere etait au moins deux fois plus eleve dans les peuplements qui contenaient A. mearnsii (32 a 49 kg.ha super(-1).an super(-1)) que dans les monocultures d'E. globulus (14 kg.ha super(-1).an super(-1)). Les peuplements qui contenaient A. mearnsii recyclaient aussi une plus grande quantite de phosphore (P) dans la chute annuelle de litiere que les monocultures d'E. globulus. Cette etude a demontre que le fait de melanger A. mearnsii avec E. globulus augmente la quantite et le taux de N et P recycles via la chute de litiere aerienne comparativement aux monocultures d'E. globulus. Par consequent, la plantation d'especes melangees semble etre un systeme sylvicole utile pour ameliorer la nutrition de l'eucalyptus sans avoir recours a la fertilisation.[Traduit par la Redaction]
    Keywords: Forest Management ; Fertilization ; Phosphorus ; Nutrients ; Biomass ; Nutrition ; Plantations ; Nitrogen ; Acacia Mearnsii ; Eucalyptus Globulus ; Management ; Bluegum Eucalyptus;
    ISSN: 0045-5067
    E-ISSN: 1208-6037
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  • 7
    Language: English
    In: Tree physiology, September 2007, Vol.27(9), pp.1319-28
    Description: Mixtures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman are twice as productive as E. globulus monocultures growing on the same site in East Gippsland, Victoria, Australia, possibly because of increased nitrogen (N) availability owing to N(2) fixation by A. mearnsii. To investigate whether N(2) fixation by A. mearnsii could account for the mixed-species growth responses, we assessed N(2) fixation by the accretion method and the (15)N natural abundance method. Nitrogen gained by E. globulus and A. mearnsii mixtures and monocultures was calculated by the accretion method with plant and soil samples collected 10 years after plantation establishment. Nitrogen in biomass and soil confirmed that A. mearnsii influenced N dynamics. Assuming that the differences in soil, forest floor litter and biomass N of plots containing A. mearnsii compared with E. globulus monocultures were due to N(2) fixation, the 10-year annual mean rates of N(2) fixation were 38 and 86 kg ha(-1) year(-1) in 1:1 mixtures and A. mearnsii monocultures, respectively. Nitrogen fixation by A. mearnsii could not be quantified on the basis of the natural abundance of (15)N because such factors as mycorrhization type and fractionation of N isotopes during N cycling within the plant confounded the effect of the N source on the N isotopic signature of plants. This study shows that A. mearnsii fixed significant quantities of N(2) when mixed with E. globulus. A decline in delta(15)N values of E. globulus and A. mearnsii with time, from 2 to 10 years, is further evidence that N(2) was fixed and cycled through the stands. The increased aboveground biomass production of E. globulus trees in mixtures when compared with monocultures can be attributed to increases in N availability.
    Keywords: Acacia -- Metabolism ; Eucalyptus -- Metabolism ; Nitrogen -- Metabolism ; Nitrogen Fixation -- Physiology ; Soil -- Analysis
    ISSN: 0829-318X
    E-ISSN: 17584469
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