Interactions between fire,mycophagous mammals,and dispersal of ectromycorrhizal fungi in Eucalyptus forests

Several species of marsupials in Eucalyptus forests in Australia feed predominantly on the sporocarps of hypogeous fungi. This feeding is apparently beneficial to the fungi as it results in dispersal of spores. As these fungi are in almost all cases ectomycorrhiza-forming species, mycophagy by mammals may play an important role in the maintenance of mycorrhizal symbiosis in Eucalyptus forests. Fire is frequent and a dominant ecological factor in these forests, and this study tested the hypothesis that fire triggers both increased sporocarp production by some hypogeous ectomycorrhizal fungi associated with eucalypts, and increased mycophagy by mammals. Three experimental burns were set in E. tenuiramus forest in southeastern Tasmania. Digging activity (which reflects feeding on hypogeous fungi) by a mycophagous marsupial, the Tasmanian bettong Bettongia gaimardi, increased up to ten-fold after fire, with a peak about 1 month post-fire. This was associated with a similar pattern of increase in sporocarp production, which was due to species in the family Mesophelliaceae (especially Castoreum tasmanicum and Mesophellia spp.). This family appears to have radiated in association with eucalypts and has an exclusively Australasian distribution, unlike many of the other ectomycorrhizal fungi collected in this study which are cosmopolitan and have broad host ranges. No B. gaimardi were killed by fire, and there was no increase in mortality following fire. Population density increased after fire as a result of immigration of adult males. However, body condition and fecundity of individual B. gaimardi were maintained at pre-fire levels. This suggests that the availability of energy to B. gaimardi increased as a result of fire, and the fact that the contribution of fungus to the diet of B. gaimardi was high on burnt relative to control sites suggests further that this increase in energy availability was provided by hypogeous fungi. Effects of fire on hypogeous fungi and B. gaimardi were short-lived; all measured variables returned to control values about 4 months after fire. The capacity of B. gaimardi to survive fire and to harvest the increased sporocarp production triggered by fire provides a mechanism for the rapid dispersal of spores after fire. This should result in the establishment of ectomycorrhizae very early in post-fire succession. Because only some species of ectomycorrhizal fungi fruited in response to burning, fire probably has a strong influence on community structure among ectomycorrhizal fungi.     

Phylogenetics and the conservation of rare taxa in the Eucalyptus angustissima complex in Western Australia

Effective conservation that preservesevolutionary entities and processes requiresconservation action that is targeted atappropriate taxonomic units. Molecularphylogenetics can contribute to the resolutionof taxonomic uncertainties by defining therelationships between populations and species,and allowing the recognition of taxonomicentities that reflect evolutionary history.Some uncertainty surrounds the status of taxain the Eucalyptus angustissima complex,which includes threatened taxa with restricteddistributions. The phylogenetic relationshipsbetween populations and taxa in the E.angustissima complex were investigated usingnuclear and chloroplast RFLP analysis.Phylogenetic relationships confirmed thegenetic differentiation of two taxa, identifiedspecies level divergence between two taxacurrently recognised at subspecies level, andestablished the identity of a previouslyundetermined population. Phylogeneticrelationships between the taxa were notcongruent with presumed relationships based onmorphological characters alone.     

The influence of habitat disturbance on reptiles in a Box-Ironbark eucalypt forest of south-eastern Australia

Understanding how habitat disturbance affects the occurrence of fauna is an important issue in the effective management of habitat and conservation of biodiversity. In this study, 11 paired sites were established around the periphery of Rushworth State Forest in central Victoria, south-eastern Australia, to examine the influence of disturbance to structural complexity in the ground strata on the occurrence of reptiles. Study sites were paired on the basis of proximity, physiognomic and vegetational characteristics – each pair was established in the same vegetation 'type' (Ecological Vegetation Class) and was dominated by the overstorey species of Red Ironbark Eucalyptus tricarpa and Grey Box E. microcarpa, or Bull Mallee E. behriana and Grey Box. They were also paired on the basis that they had experienced different degrees of disturbance to the ground strata. Sites within each pair differed substantially in their ground-layer structure (e.g. number of stumps, total number of shrubs, litter depth), but were virtually indistinguishable in their overstorey characteristics (e.g. basal area, canopy cover, cover of tall shrubs). Surveys over two summer seasons using area-constrained active searches yielded ten species of reptiles from five families. Despite the repeated search effort, both the number of reptile species and individuals recorded per site were low (4 species, 17 individuals), suggesting the possibility of historical impoverishment. Reptiles were generally 2.4 times more abundant on 'undisturbed' than 'disturbed' sites. The disparity was also reflected in the number of species per site, which was significantly greater on the 'undisturbed' sites. The greater species richness and abundance of reptiles recorded for 'undisturbed' sites are attributed to the greater structural complexity of the ground strata on these sites. Effective management for reptiles, therefore, should aim to create, retain or increase the structural heterogeneity of a site, particularly in the ground-layers.     

Fluxes of elements in rain passing through forest canopies in south-eastern Australia

The elemental content of rainfall (bulk deposition), throughfall and stemflow was measured inPinus radiata D. Don andEucalyptus forests in Gippsland, Victoria. Accessions in rainfall (mg m^–2 year^–1) averaged: organic-C 551, NO₃ ^–-N 96, NH₄ ⁺-N 62, total-N 303, K⁺ 382, Na⁺ 2250, Ca²⁺ 1170, and Mg²⁺ 678. The mean pH of rainfall was 5.9. Concentrations of all elements were greater in throughfall than in rainfall, and generally greater in stemflow than in throughfall. However, pH of pine throughfall was higher than that of rainfall, and pH of eucalypt throughfall was lower than that of rainfall. There was a net efflux of inorganic-N from pine crowns to rainfall, whilst in eucalypts there was generally net sorption of inorganic-N from rainfall. In both species organic-N was leached from the crowns and the net efflux of total-N from eucalypt crowns (50 mg m^–2 year^–1) averaged one-quarter of that in pines. Increases in the organic-C content of throughfall relative to rainfall in eucalypts were two to four times those in pines. Increases in the content of other elements in throughfall were comparable in pines and eucalypts and within the ranges K⁺ 615–1360, Na⁺ 480–-1840, Ca²⁺ 123–780 and Mg²⁺ 253–993 mg m^–2 year^–1. However, enrichment of Ca²⁺ may have been due to dust trapped in the canopies. Stemflow contributed significantly to the total amounts of elements reaching the forest floor in water.     

Fertilizer and soil nitrogen accumulation by irrigated barley grown on a red-brown earth in south-eastern Australia

¹⁵N labelled (NH₄)₂SO₄ was applied to barley at 5 g N m⁻² (50 kg N ha⁻¹) in microplots at sowing to study the timing of the N losses and the contribution of soil and fertilizer N to the plant. Water treatments included rainfed and irrigation at 45–50 mm deficit beginning in the spring. Recovery of¹⁵N in the plant increased to a maximum of about 20% within 91 days after sowing (DAS 91) and then remained constant. Approximately 16% (0.8 g N m⁻²) of the fertilizer was in the stem and leaves at DAS 91 and this N was subsequently redistributed to the head. At maturity, approximately 75% of the¹⁵N assimilated by the tops was recovered in the grain. Soil N contributed 3.6 g N m⁻² to the head; 2.2 g N m⁻² was remobilized from the stem and leaves, and the balance, approximately 1.4 g N m⁻², was taken up from the soil between DAS 69 to 91. Effects of irrigation treatments on N accumulation were not significant. Residual¹⁵N fertilizer in the soil decreased with time from sowing, and at maturity 40% of the applied N was recovered in the surface 0.15 m.¹⁵N movement to depth was limited and less than 5% of the fertilizer was recovered below 0.15 m. Irrigation had no effect on the¹⁵N recovery at depth. Total recovery of the¹⁵N varied between 60 and 67% and implies that 33–40% was lost from the soil-plant system. The total recovery in the soil and plant was not affected by time or irrigation in the interval DAS 39 to 134. Losses occurred before DAS 39 when crop uptake of N was small and soil mineral N content was high. There was an apparent loss of 1.9 g fertilizer N m⁻² (i.e. 38% of that applied) between DAS 1 and 15. This loss occurred before crop emergence when rainfall provided conditions suitable for denitrification.     

Nutrient cycling and nitrogen mineralization in eucalypt forests of south-eastern Australia

Summary Nutrient pools in litter and soil and the major nutrient transfers and additions in rainfall, throughfall and litterfall were measured in eight mature, undisturbed eucalypt forests covering a range of species, climate, productivity and soil type. Litterfall is the major pathway for the return of N, P, Ca and usually Mg, to the soil. The forests covered almost the range of litterfall reported for eucalypt forests and, in conjunction with published data, litterfall was strongly related to climatic variables. Extractable P in the soil and P concentrations in litter and litterfall were significantly higher in two sub-alpine forests (Eucalyptus pauciflora andE. delegatensis) than in all other forests. In general, nutrient turnover, particularly N turnover, was related to the rate of organic matter turnover. Rates of organic matter turnover in these forests and in other studies of eucalypts were correlated with climatic conditions using the simple climatic scalar developed by Vitousek. Nitrogen turnover, especially that proportion cycling via leaf litterfall is primarily a function of organic matter turnover, but litter quality appears also to have an influence.     

Effects of water and nutrient supply on amount and on nutrient concentration of litterfall and forest floor litter in Eucalyptus globulus plantations

A field experiment was initiated in March 1986 in central Portugal to evaluate the influence of water and nutrient supply on the productivity of E. globulus. The treatments applied were, irrigation plus fertiliser, irrigation and the application of fertilisers in rainfed plots. The control received neither fertilisers nor irrigation. The annual pattern litterfall was measured over a period of 5 years and the litter layer was quantified 6 years after planting. The amount of litterfall varied with the treatments. Simultaneous water and nutrient supply increased significantly litterfall, in respect to control. In rainfed conditions the timing of the maximum of litterfall was anticipated relative to the irrigated plots. However, the time of maximum litterfall did not coincide with the dry season but rather with period of maximum growth in each treatment. The N and P concentration was higher in the litterfall of the two fertilised treatments than in the others. The lowest concentrations of N and P in the leaf litter were coincident with the summer period in all treatments. The withdrawal of N and P ranged between 32 and 65% according to treatment and season. The deliverance of nutrients through litterfall was strongly increased by simultaneous water and nutrient supply. The supply of fertilisers in rainfed conditions promoted higher deliverance of nutrients than in the plots irrigated only. The mass of the litter layer was significantly increased by simultaneous water and nutrient supply. Application of fertilisers induced an increase in N and P concentration and a decrease in C/N ratio of the litter layer. Treatments and C/N values did not influence apparently the proportion of carbon, N and P released through mineralization from the litter layer. The non-fertilized treatments showed a more efficient N cycling than the others.     

Effects of N-serve on soybeans and soil nitrogen transformations

Summary Plant dry weight, total N, and total Ca was increased at 0.1 and 1 ppm N-serve. At greater 10 ppm the plants showed visual symptoms of a stunted growth, stem elongation, flowers, and pods failed to form or were aborted, young leaves were curled, and roots were club shaped with many branches. These symptoms were increasingly evident with increasing N-serve application rates. The reason was attributed to an auxin effect. Dry wt and total N in the plant was less than the control at the higher N-serve applications. There was little effect on nitrogenase activity at less than 10 ppm N-serve. Nodulation tended to increase at 0.1 and 1 ppm N-serve.Nitrification was inhibited up to 104 days at 20 ppm N-serve. The soil pH of the high N-serve rates was decreased at 104 days probably due to nitrification. Generally there were little detectable differences among treatments in soil organic N. The average soil organic N from 0 to 104 days decreased by 0.01%. Average increase in total N within each pot at harvest was equivalent to about 138 kg N/ha.     

Effects of field fertilizer practices on labeled ammonium-nitrogen transformations and its utilization by winter wheat

Summary Field experiments with winter wheat (Triticum aestivum L.) were conducted in two years at two locations using¹⁵N-enriched (NH₄)₂SO₄ on Smolan silt loam (Pachic Argiustoll) and Ost loam (Typic Arguistoll) soils. The objective was to relate differences in crop utilization of fertilizer to movement and transformations of the N in a complete factorial experiment having fall and spring applications, banded and broadcast, with and without nitrapyrin. Plant uptake of the 60 kg N/ha applied varied from 31% to 62% with greatest uptake when fertilizer was banded in the spring without nitrapyrin and least uptake from fall and spring broadcast treatments using nitrapyrin. Analysis of single factor effects showed greater crop contents of fertilizer N for spring than fall applications. That was related to immobilization of the applied N. Much more fertilizer N was in inorganic forms during the period of rapid wheat growth with spring applications than with fall. Banding the fertilizer at a depth of 0.05 m resulted in greater plant uptake than broadcasting or banding it on the soil surface. A significant portion of the applied N was immobilized near the point of application. That limited the downward movement of the N placed on the surface, making it less available to plant roots than the N placed 0.05 m deep where soil moisture was more favorable. Use of nitrapyrin resulted in lowered amounts of fertilizer N as NO₃-until mid-May for fall treatments and until harvest with spring treatments. That appeared to be the reason for lowered plant uptake when nitrapyrin was used. Published in memory of Professor R V Olson and over 40 years of contributions and service to agriculture and soil science (1919–1985).     

Maintenance of high pollen dispersal in Eucalyptus wandoo, a dominant tree of the fragmented agricultural region in Western Australia

Pollen dispersal was investigated in five remnant populations of Eucalyptus wandoo, a dominant insect-pollinated tree in the fragmented agricultural region of southern Western Australia. Paternity analysis using six microsatellite loci identified a pollen source for 45% of seedlings, and the remainder were assumed to have arisen from pollen sources outside the stands. Outcrossing was variable, ranging from 52 to 89%, and long distance pollen dispersal was observed in all populations with up to 65% of pollen sourced from outside the populations over distances of at least 1 km. Modelling dispersal functions for pollination events within the two larger populations showed little difference between the four two-parameter models tested and indicated a fat-tailed dispersal curve. Similarity of direct and indirect historical estimates of gene flow indicates maintenance of gene flow at levels experienced prior to fragmentation. The study revealed extensive long distance pollen dispersal in remnant patches of trees within a fragmented agricultural landscape in the southern temperate region and highlighted the role of remnant patches in maintaining genetic connectivity at the landscape scale.     

Effects of forest harvesting nutrient removals on soil nutrient reserves

Summary Intensive harvesting of native eucalypt forests is carried out in the Eden area in the south east coastal region of New South Wales, Australia. Soil nutrient capital and nutrient removals in forest harvesting were estimated together with potential impacts of these removals on the nutrient capital balance. Soils were anlysed from eighty sites for phosphorus fractions, including organic phosphorus fractions, and total and exchangeable cations. Based on typical forest harvesting systems, it was found that 3–4 kg phosphorus would be removed per hectare. Due to equilibrium between the various soil phosphorus components, depletion would not be solely from the more available pools. It is expected that at least four forest rotations (320 years) would be required before any detectable change would occur, within forest communities. A similar depletion estimate was calculated for the potentially most vulnerable cation, calcium. The other nutrient cations, magnesium and potassium had considerably greater reserves.     

Soil N chemistry in oak forests along a nitrogen deposition gradient

Anthropogenic N deposition may change soil conditions in forest ecosystems as demonstrated in many studies of coniferous forests, whereas results from deciduous forests are relatively scarce. Therefore the influence of N deposition on several variables was studied in situ in 45 oak-dominated deciduous forests along a N deposition gradient in southern Sweden, where the deposition ranged from 10 to 20 kg N ha⁻¹ year⁻¹. Locally estimated NO ₋ ³ deposition, as measured with ion-exchange resins (IER) on the soil surface, and grass N concentration (%) were positively correlated with earlier modelled regional N deposition. Furthermore, the δ¹⁵N values of grass and uppermost soil layers were negatively correlated with earlier modelled N deposition. The data on soil NO ₋ ³ , measured with IER in the soil, and grass N concentration suggest increased soil N availability as a result of N deposition. The δ¹⁵N values of grass and uppermost soil layers indicate increased nitrification rates in high N deposition sites, but no large downward movements of NO ₋ ³ in these soils. Only a few sites had NO ₋ ³ concentrations exceeding 1 mg N l⁻¹ in soil solution at 50 cm depth, which showed that N deposition to these acid oak-dominated forests has not yet resulted in extensive leaching of N. The δ¹⁵N enrichment factor was the variable best correlated with NO ₋ ³ concentrations at 50 cm and is thus a variable that potentially may be used to predict leaching of NO ₋ ³ from forest soils.     

Nitrate deposition in northern hardwood forests and the nitrogen metabolism of Acer saccharum marsh

It is generally assumed that plant assimilation constitutes the major sink for anthropogenic Nitrate NO ₃ ^– deposited in temperate forests because plant growth is usually limited by nitrogen (N) availability. Nevertheless, plants are known to vary widely in their capacity for NO ₃ ^– uptake and assimilation, and few studies have directly measured these parameters for overstory trees. Using a combination of field and greenhouse experiments, we studied the N nutrition of Acer saccharum Marsh. in four northern hardwood forests receiving experimental NO ₃ ^– additions equivalent to 30 kg N ha^–1 year^–1. We measured leaf and fine-root nitrate reductase activity (NRA) of overstory trees using an in vivo assay and used ¹⁵N to determine the kinetic parameters of NO ₃ ^– uptake by excised fine roots. In two greenhouse experiments, we measured leaf and root NRA in A. saccharum seedlings fertilized with 0–3.5 g NO ₃ ^– –N m^–2 and determined the kinetic parameters of NO ₃ ^– and NH ₄ ⁺ uptake in excised roots of seedlings. In both overstory trees and seedlings, rates of leaf and fine root NRA were substantially lower than previously reported rates for most woody plants and showed no response to NO ₃ ^– fertilization (range = non-detectable to 33 nmol NO ₂ ^– g^–1 h^–1). Maximal rates of NO ₃ ^– uptake in overstory trees also were low, ranging from 0.2 to 1.0 mol g^–1 h^–1. In seedlings, the mean V _max for NO ₃ ^– uptake in fine roots (1 mol g^–1 h^–1) was approximately 30 times lower than the V _max for NH ₄ ⁺ uptake (33 mol g^–1 h^–1). Our results suggest that A. saccharum satisfies its N demand through rapid NH ₄ ⁺ uptake and may have a limited capacity to serve as a direct sink for atmospheric additions of NO ₃ ^– .     

Effects of ethylene and cytokinins on vase life of cut Eucalyptus parvifolia Cambage branches

The role of ethylene and cytokinins was investigated during postharvestsenescence of cut Eucalyptus parvifolia Cambage branches.The effect of endogenous and exogenous ethylene on the vase life of the cutbranches was studied using 2 mM 1-aminocyclopropane-1-carboxylicacid (ACC) as a continuous treatment or pulse treatment for 48h with 20, 40 and 80 l l^–1ethylene. Both endogenous and exogenous ethylene reduced the vase life of thebranches; however, the effect of the endogenous hormone was stronger than theexogenous applications. Ethylene biosynthesis was inhibited by pulse treatmentfor 24 h using 1 mM AOA or 2 mMCoCl₂. The latter treatment significantly extended the vase life ofthe branches by delaying senescence. The effect of cytokinins was evaluated onthe vase life of cut E. parvifolia branches by pulsetreatment for 24 h with 10, 50 and 100 mM thidiazuron(TDZ) or 85, 130 and 260 mM N6-benzyladenine (BA). The resultsobtained showed that no response was observed following pulse treatment with BAwhile, although TDZ had little effect on vase life, it was a good inhibitor ofchlorophyll degradation.     

Eucalyptus microsatellites mined in silico: survey and evaluation

Eucalyptus is an important short rotation pulpy woody plant, grown widely in the tropics. Recently, many genomic programmes are underway leading to the accumulation of voluminous genomic and expressed sequence tag sequences in public databases. These sequences can be utilized for analysis of simple sequence repeats (SSRs) and single nucleotide polymorphism (SNPs) available in the transcribed genes. In this study, in silico analysis of 15,285 sequences representing partial and full-length mRNA from Eucalyptus species for their use in developing SSRs or microsatellites were carried out. A total of 875 EST-SSRs were identified from 772 SSR containing ESTs. Motif size of 6 for dinucleotide and 5 for trinucleotide, tetranucleotide, and pentanucleotides were considered in locating the microsatellites. The average frequency of identified SSRs was 12.9%. The dinucleotide repeats were the most abundant among the dinucleotide, trinucleotide and tetranucleotide motifs and accounted for 50.9% of the Eucalyptus genome. Primer designing analysis showed that 571 sequences with SSRs had sufficient flanking regions for polymerase chain reaction (PCR) primer synthesis. Evaluation of the usefulness of the SSRs showed that EST-derived SSRs can generate polymorphic markers as all the primers showed allelic diversity among the 16 provenances of E. tereticornis.     

Reduction of generation time in Eucalyptus globulus

The plant growth retardant paclobutrazol was applied by foliar spray to seedlings of Eucalyptus globulus (Labill.) to determine its effects on reproductive activity. It was shown to induce flowering in vegetatively juvenile seedlings and increase reproductive activity in vegetatively adult material. The former case represented a 50% (three year) reduction in generation time for commercial seedlings. Paclobutrazol treatment did not appear to have a negative effect on any aspect of reproductive development, germination of new seed, or early seedling growth, while having a distinct positive effect on reproductive output. This suggests that paclobutrazol may be an effective tool enabling tree breeders to reduce generation time and increase reproductive output in E. globulus. Foliar spraying during autumn was shown to be an effective means and timing of paclobutrazol application, with results evident in the following flowering season. Considerable persistence of paclobutrazol effects was noted in the second season after application. Pot size and growth temperatures also play roles in determining the extent of new reproductive activity each season in E. globulus seedlings.     

中度火干扰对兴安落叶松林土壤呼吸的影响

通过测定中度火干扰后塔河地区兴安落叶松(Larix gmelinii)林生长季土壤呼吸(R_s),并进一步探究火干扰后影响土壤呼吸变化的主要环境因子。选择在塔河林业局火烧4年后兴安落叶松林中度火烧迹地设置样地,选择临近未过火区域设置对照样地。土壤呼吸通量用LI-8100进行测量,土壤异养呼吸(R_h)采用壕沟法进行测量。火烧迹地与未火烧对照样地生长季土壤呼吸速率平均值分别为(3.67±1.03)μmol CO_2m~(-2)s~(-1),(4.21±1.25)μmol CO_2m~(-2)s~(-1)。火烧迹地土壤呼吸速率显著降低(P0.05)。生长季土壤呼吸组分的动态变化表明,土壤呼吸速率的降低是因为土壤自养呼吸(R_a)显著降低导致的(P0.05)。温度是控制这一地区生长季土壤呼吸变化的主要环境因子。与对照样地相比,火烧迹地土壤呼吸的变化与土壤温度具有更强的相关性。塔河地区兴安落叶松林火烧迹地和未火烧对照样地Q_(10)分别为5.85±1.06,4.25±1.19,火干扰后Q_(10)显著增加(P0.05)。研究结果表明:在全球气候变化的背景下火干扰后中国塔河地区兴安落叶松林生态系统对温度的变化更为敏感。本研究结果将为研究中国塔河地区火干扰后碳循环变化提供数据支持。     

澳大利亚森林火灾的管理与火生态的研究

澳大利亚是火灾频发的地区．每年因森林火灾的危害都要造成相当的社会、经济损失及生态环境的破坏,故火生态的研究及火的管理在澳大利亚的生态学研究中一直占有重要地位．本文主要讨论了澳洲森林大火起燃的物理过程和机制、可燃物的特征、林火的特点、习性及对生态环境的影响和如何控制和减少火灾的危害性,达到对火进行利用、控制和管理的目的．     

Effects of fire on the vegetation of a lowland heathland in North-western Italy

This study focuses on the effect of fire on lowland heathlands at the extreme southern edge of their European distribution (Vauda Nature Reserve, NW Italy). Forty-nine plots (50 m radius) were surveyed between 1999 and 2006. Each year, fire occurrences were recorded and per cent cover of four vegetation types (grassland, heath, low shrubland, and tall shrubland) was estimated in each plot. Vascular plant species richness was also recorded in 255, 1 m² quadrats. After a fire, grassland vegetation expanded, but then declined rapidly as heath and shrubland recovered: 7 years after a fire, tall shrubland encroached on to more than 40% of the plots, and grassland declined from 50% to 20% cover. Between 1999 and 2006, Betula pendula shrubland greatly expanded, while grassland decreased over most of the Reserve, even where fire frequency was high. Tall shrubland had low plant diversity and was dominated by widespread species of lower conservation value. By contrast, early successional vegetation (grassland and low shrubland) had higher richness and more narrowly distributed species, indication that the development of tall shrubland causes significant species loss in the heathland. Italian lowland heathlands are characterized by high rates of shrubland encroachment that threatens both habitat and species diversity. Burning frequencies of once in 3–6 years seem appropriate in this habitat, but burning alone might not suffice without actions to increase herbivore grazing.     

Gas exchange and photosynthesis of Eucalyptus camaldulensis seedlings inoculated with different ectomycorrhizal symbionts

Eucalyptus camaldulensis Dehnh. seedlings inoculated with Pisolithus tinctorius (Pers.) Coker & Couch and Thelephora terrestris Ehrl. per Fr. were grown in well watered soil (_s –0.03 MPa) or subjected to a long-term soil water stress of up to –1.0 MPa over 13-week period in a glasshouse. After 13 weeks, all seedling containers were watered to field capacity and then water was withheld from the E. camaldulensis seedlings to induce a short-term drought. Diurnal measurements of seedling photosynthesis rate (A), leaf stomatal conductance (g) and leaf water potential (_p) were completed before, during, and after the short term drought. Although they were growing in an equal soil volume, photosynthesis rate (A), leaf stomatal conductance and leaf water potential (_p) of larger seedlings with P. tinctorius ectomycorrhizae were similar to those of smaller seedlings colonized with T. terrestris during the short-term drought period. Seedlings inoculated with Pisolithus tinctorius maintained higher photosynthesis rates over the course of the short-term drought. Thus, P. tinctorius ectomycorrhizae appear to be more efficient than those of T. terrestris in assisting seedlings to maintain gas exchange and photosynthesis under limited soil moisture conditions.