The importance of temperate woodland in travelling stock reserves for vertebrate biodiversity conservation

Summary Travelling stock reserves have well recognised and important commercial, cultural and other values in the pastoral and agricultural regions of Australia, but their conservation values remain poorly known. In general, many areas of woodlands within travelling stock reserves have not been subjected to the same high levels of degradation pressure as similar temperate woodlands on private land. In this study, we compared several measures of vertebrate biota in 217 permanent field sites located in travelling stock reserves and woodland remnants located almost exclusively on private land in the Murray Riverina and South West Slopes bioregions in southern New South Wales. We found that in comparison with temperate woodland remnants on private land, temperate woodland in travelling stock reserves tended to support more species of birds, more species of declining birds, and a greater abundance of arboreal marsupials. Temperate woodland in travelling stock reserves was more likely to be occupied by particular individual species of birds of conservation concern. However, such tenure differences were not consistent between bioregions. For example, the Rufous Whistler (Pachycephala rufiventris) and the Red‐capped Robin (Petroica goodenovii ) were significantly more likely to occupy temperate woodland in travelling stock reserves than temperate woodland on private land in the Murray Riverina but such effects were not apparent in the South West Slopes. Similarly, while the Grey‐crowned Babbler (Pomatostomus temporalis) was significantly more likely to occupy temperate woodland in travelling stock reserve sites in the South West Slopes, we found the opposite effect in Murray Riverina. We demonstrated that travelling stock reserves have important conservation values for some taxa and individual species. Because of the paucity of large ecological reserves in the Murray Riverina and South West Slopes bioregions, temperate woodlands located in travelling stock reserves should be considered as an important resource that contributes to a portfolio of vegetation assets in formerly woodland‐dominated, but now extensively cleared, agricultural landscapes.     

Effects of leaf and branch removal on carbon assimilation and stem wood density of Eucalyptus grandis seedlings

The rate of leaf CO₂ assimilation (A _l) and leaf area determine the rate of canopy CO₂ assimilation (A _c) can be thought proportional to assimilate supply for growth and structural requirements of plants. Partitioning of biomass within plants and anatomy of cells within stems can determine how assimilate supply affects both stem growth and wood density. We examined the response of stem growth and wood density to reduced assimilate supply by pruning leaf area. Removing 42% of the leaf area of Eucalyptus grandis Hill ex Maiden seedlings did not stimulate leaf-level photosynthesis (A _l) or stomatal conductance, contrary to some previous studies. Canopy-level photosynthesis (A _c) was reduced by 41% immediately after pruning but due almost solely to continued production of leaves, and was only 21% lower 3 weeks later. Pruning consequently reduced seedling biomass by 24% and stem biomass by 18%. These reductions in biomass were correlated with reduced A _c. Pruning had no effect on stem height or diameter and reduced wood density to 338 kg m⁻³ compared to 366 kg m⁻³ in control seedlings. The lower wood density in pruned seedlings was associated with a 10% reduction in the thickness of fibre cell walls, and as fibre cell diameter was invariant to pruning, this resulted in smaller lumen diameters. These anatomical changes increased the ratio of cross-sectional area of lumen to area cell wall material within the wood. The results suggest changes to wood density following pruning of young eucalypt trees may be independent of tree volume and of longer duration.     

Structure and biomass along an Acacia zanzibarica woodland–savanna gradient in a former ranching area in coastal Tanzania

Questions: What factors influence the density, size and growth form of trees in secondary Acacia zanzibarica woodlands on a former humid savanna rangeland? How does tree density relate to variation in tree foliage and spines, and woody and grass biomass? Location: Tropical coastal Tanzania (former Mkwaja Ranch, now in Saadani National Park). Methods: We surveyed 97 circular plots (4‐m radius) representing a gradient from open savanna to dense woodland. Within each plot, we measured all trees and estimated the biomass of spines. Foliage biomass of tree and grass layers was estimated on three occasions, twice during the wet season and once in the dry season. Soil samples were taken from each plot and analysed for texture and nutrient content. Interrelationships among various variables were investigated using linear multiple regression and mixed effects models. Results: Tree densities were highest on more nutrient‐rich, heavy soils. Spinescence was highest on trees in open savanna. Biomass of tree foliage in the wet season was best explained by numbers of ant nests and tree live‐wood ratio. Foliage biomass in the dry season was less than half that in the wet season and best predicted by grass biomass. Variables related to biomass of the grass layer were strongly influenced by fire; living grass biomass also decreased with increasing tree density. Conclusions: A. zanzibarica is a tree with a high water demand, and the association with heavy soils is probably due to greater availability of water on these sites. Establishment of A. zanzibarica woodlands significantly reduced grazing resources at Mkwaja Ranch. Under post‐ranching conditions, however, fires and soil conditions predominate. The woodlands may, therefore, represent a transient state of woody density in a still resilient humid savanna.     

Regional Variations in Biomass Distribution in Brazilian Savanna Woodland

The Cerrado, the savanna biome in central Brazil, mostly comprised of woodland savanna, is experiencing intense and fast land use changes. To understand the changes in Cerrado carbon stocks, we present an overview of biomass distribution in different Cerrado vegetation types (i.e., grasslands, shrublands and forestlands). We surveyed 26 studies including 170 Cerrado sites. The grasslands presented mean total biomass of 24 Mg/ha, with 70 percent allocated in the belowground portion. In shrublands, the mean total biomass was 58 Mg/ha being 58 percent in the belowground portion. Finally, in forestlands the mean total biomass was 98 Mg/ha with 18 percent as belowground biomass. The surveyed studies presented 12 allometric equations for biomass estimate, most involving both diameter and height. Data on wood density for Cerrado shrubs and trees are not abundant and the average value was 0.66 g/cm³, similar to that found in the central portion of the Amazon Forest. We also examined the relationship between total precipitation and dry‐season intensity with biomass variation in the Cerrado shrubland using data from tropical rainfall measurement mission (TRMM) for the period 2000–2010. Dry‐season precipitation amount in cerrado areas in severe drought regions explained 29 percent of the variation in aboveground woody biomass. This finding is important in the face of the predictions of longer and more severe dry seasons in the region due to climate change.     

Wood density predicts plant damage and vegetative recovery rates caused by cyclone disturbance in tropical rainforest tree species of North Queensland,Australia

Abstract The ability to withstand disturbance (resistance) and the ability to recover biomass following disturbance (resilience) were investigated in Australian wet tropical rainforest tree species. These two attributes are expected to be negatively correlated, because investment of biomass in structural support (conferring resistance) results in trees exhibiting high wood densities and slow growth rates, and vice versa. We examined species’ responses to disturbance caused by a severe tropical cyclone to test this hypothesized trade‐off. We assessed cyclone damage in six species in three Mabi rainforest fragments on the Atherton Tablelands. Species differed in the proportion of individuals within four damage categories (minor damage, severe branch damage, snapped, uprooted). Resistance was positively related to wood density. We found a positive correlation between the proportion of trees experiencing minor damage only and wood density, supporting the hypothesized association between resistance and mechanical strength. Among the subset of trees in which stems snapped, rates of resprouting differed between species and were highest in low wood density species and lowest in species with highest wood density. Resilience, characterized as the ability to recover biomass following disturbance and estimated as growth rate standardized for stem diameter at breast height (g day^?1 · mm^?1), was negatively related to wood density. Thus, species with low wood densities were more likely to suffer stem and branch damage owing to cyclonic winds, but also demonstrated highest resprouting and fastest responses in terms of redeveloping biomass in the 8 months following disturbance. This suggests that a species’ position along the resistance–resilience spectrum can be predicted by mean wood density, which may allow managers to predict species’ responses to future cyclones. Our findings also provide mechanistic evidence for the ‘direct regeneration’ model of post‐cyclone succession, where response is characterized by resprouting and species composition is unchanged.     

Effects of forest management on the carbon dioxide emissions of wood energy in integrated production of timber and energy biomass

The aim of this work was to study the sensitivity of carbon dioxide (CO₂) emissions from wood energy to different forest management regimes when aiming at an integrated production of timber and energy biomass. For this purpose, the production of timber and energy biomass in Norway spruce [Picea abies (L.) Karst] and Scots pine (Pinus sylvestris L.) stands was simulated using an ecosystem model (SIMA) on sites of varying fertility under different management regimes, including various thinning and fertilization treatments over a fixed simulation period of 80 years. The simulations included timber (sawlogs, pulp), energy biomass (small‐sized stem wood) and/or logging residues (top part of stem, branches and needles) from first thinning, and logging residues and stumps from final felling for energy production. In this context, a life cycle analysis/emission calculation tool was used to assess the CO₂ emissions per unit of energy (kg CO₂ MWh^?1) which was produced based on the use of wood energy. The energy balance (GJ ha^?1) of the supply chain was also calculated. The evaluation of CO₂ emissions and energy balance of the supply chain considered the whole forest bioenergy production chain, representing all operations needed to grow and harvest biomass and transport it to a power plant for energy production. Fertilization and high precommercial stand density clearly increased stem wood production (i.e. sawlogs, pulp and small‐sized stem wood), but also the amount of logging residues, stump wood and roots for energy use. Similarly, the lowest CO₂ emissions per unit of energy were obtained, regardless of tree species and site fertility, when applying extremely or very dense precommercial stand density, as well as fertilization three times during the rotation. For Norway spruce such management also provided a high energy balance (GJ ha^?1). On the other hand, the highest energy balance for Scots pine was obtained concurrently with extremely dense precommercial stands without fertilization on the medium‐fertility site, while on the low‐fertility site fertilization three times during the rotation was needed to attain this balance. Thus, clear differences existed between species and sites. In general, the forest bioenergy supply chain seemed to be effective; i.e. the fossil fuel energy consumption varied between 2.2% and 2.8% of the energy produced based on the forest biomass. To conclude, the primary energy use and CO₂ emissions related to the forest operations, including the production and application of fertilizer, were small in relation to the increased potential of energy biomass.     

Plant and arthropod communities in young oak stands: are they determined by site history?

Effect of site history on forest plant and insect communities was studied by comparing afforestations on former agricultural land with reafforestations on ancient woodland sites. Vascular plants, mosses, true bugs, lacewings and saproxylic beetles were surveyed at 18 young broadleaved forest sites dominated by oak (Quercus robur), established between 1986 and 1994 in three different growth regions in Bavaria, Germany. Two strata, near ground level and the canopy, were sampled. Compared to woodland reafforestations greater species density and abundance of plants and true bugs were observed in field layer of afforestation sites. Proportion of forest species among plants and true bugs was however significantly lower in afforestations than on ancient woodland sites. In the canopy, zoo-phytophagous true bugs were significantly better represented in afforestations and zoophagous true bugs in reafforestations. Saproxylic beetles, especially inhabitants of old dead wood, were species-poor in afforestations. Results indicate that site history affects both producer and consumer communities in multiple ways, even 20 years after afforestation of former agricultural land. However, afforestations adjacent to existing forest stands can be regarded as valuable to nature conservation in effectively extending forest habitats. Investment in such afforestation therefore represents more than just an agricultural subsidy. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Evaluating a sustainability index for nutrients in a short rotation energy cropping system

In dryland environments 3–5 year rotations of tree crops and agriculture represent a major potential bioenergy feedstock and a means to restore landscape hydrologic balances and phytoremediate sites, while maintaining food production. In soils with low natural fertility, the long‐term viability of these systems will be critically affected by site nutrient status and subsequent cycling of nutrients. A nutrient assimilation index (NAI) was developed to allow comparison of species and tree component nutrient assimilation and to optimize nutrient management, by quantifying different strategies to manage site nutrients. Biomass, nutrient export and nutrient use efficiency were assessed for three short rotation tree crop species. Nutrient exports following harvest at 3 years of high density (4000 trees ha^?1) were consistently higher in Pinus radiata, with values of 85 kg ha^?1 of N, 11kg ha^?1 of P, and 62 kg ha^?1 of K, than Eucalyptus globulus and Eucalyptus occidentalis. Component NAI was generally in the order of leaf?1 for N in leaves of P. radiata to 4.7 Mg kg^?1 for P in stem‐wood of E. occidentalis, indicating higher sustainability of wood biomass compared with leaf biomass. The leaves for each species contained between 40 and 60% of the total nutrient contents while comprising around 25–30% of the total biomass. These nutrient exports via biomass removal are similar to those that follow 3 years of wheat production in the same region, indicating there is no additional drawdown of nutrient reserves during the tree cropping phase of the rotation.     

Spatial and temporal woodland patterns along the lower Turkwel River, Kenya

Spatial and temporal patterns of riverine woodlands in arid regions of Africa are poorly documented despite their considerable conservation value. We studied 1540 ha of riverine woodland in the lower Turkwel River floodplain, Kenya, between 1990 and 1998. Forty‐one woodland patches were mapped and their soil physical and chemical characteristics, tree species diversity, woody cover, tree density, wood volume and woodland regeneration were determined. The riverine woodland comprised nine vegetation types and a total of 14 woody species. Woodland patch mosaics were associated with microtopographical features and selected soil attributes. The most important woody species were Hyphaene compressa H. Wendl., Acacia tortilis (Forssk.) Hayne and Cadaba rotundifolia Forssk. The exotic Prosopis chilensis (Mol.) St. was invading parts of the riverine woodland. Overall, woody species diversity was low compared to similar riverine woodlands in East Africa. Tree density, wood volume and woody plant regeneration declined over the 8‐year study period, while woody cover was unchanged. Reduced tree density, wood volume and regeneration of woody species might be linked to changes in river flood patterns following the impoundment of the Turkwel Gorge Dam. It is suggested that spatially heterogeneous and temporally stochastic regeneration events, together with occasional tree mortality caused by channel abandonment, create the complex pattern of woodland patches in the lower Turkwel River floodplain. The mapped woodland patches may serve as monitoring units, which in future could reveal the interplay between changes in flooding patterns as a result of dam impoundment, anthropogenic disturbance and the well‐being of the riverine woodlands.     

Population densities and community structure of birds in broadleaved woodland in the lowveld of Swaziland

Population density and community structure of birds was studied at three sites in broadleaved (combretaceous) woodland in the lowveld of Swaziland. Birds were surveyed monthly using a standard point count technique. A total of 94 species of birds was recorded. Species richness at the three sites ranged between 57 and 73 species. Population density was similar at the three sites and ranged from 11.8 to 13.9 birds/ha. Biomass of birds was also similar at the three sites. Resident birds only accounted for 49% of all species, but made up 85% of the individuals and 82% of the biomass. There was a relatively large number of vagrant species, but they only accounted for 10% of the individuals and 14% of the biomass. Species richness of intra-African and Palaearctic migrants was low, and they contributed little to the bird density or biomass. In terms of diet, most birds were insectivorous, with mixed diet and granivorous species contributing approximately equally to biomass. Frugivorous species and raptors contributed little. The avifauna of broadleaved woodland in Swaziland is compared with that of other broadleaved woodlands in southern Africa and with that of Acacia savanna in Swaziland. Broadleaved woodland in Swaziland appears to support an avifauna which is depauperate compared to that of Acacia savanna, but not distinct from it.     

Regeneration of cleared Acacia zanzibarica bushland in Kenya

Abstract. Woody biomass production in natural forests of arid and semi-arid regions is low. The fuelwood demand of settlements often exceeds the sustained yield and regeneration capacity of natural forests, which results in deforestation. Regeneration and woody biomass development was studied in cleared Acacia zanzibarica bushland in Bura, eastern Kenya. The area was cleared in 1982 and studied in 1988. The site had been colonized primarily by Acacia zanzibarica and A. reficiens. Mean density was 1333 trees/ha, mean total woody biomass (dry weight) 1954 kg/ha, equal to 2.53 m³/ha. Mean annual increment was 293 kg/ha, or 0.3 8m³/ha. Expressed as rain use efficiency, the natural dry matter productivity of the woody component equals 0.83 kg ha^-1 yr^-1 mm^-1. The regeneration potential and some management implications are discussed.     

Koalas use young Eucalyptus plantations in an agricultural landscape on the Liverpool Plains,New South Wales

Summary Revegetation within cleared farming landscapes offers the potential to restore habitat for many woodland‐dependent species that have declined since European settlement. Most species of arboreal marsupials require hollows for breeding and diurnal shelter, a resource that is usually available only in old trees; however, this constraint does not apply to the Koala. In this study, we describe the occupancy and use of young (4‐ to 7‐year old) eucalypt plantations by Koalas in a predominantly cleared landscape used for intensive cropping and grazing. We compare Koala occupancy in 27 eucalypt plantations, 5 paddocks and 11 remnant forest and woodland sites, and we report the relative usage of these three land cover types by two adult male Koalas that were radio‐tracked for 5 and 7 months using GPS transmitters. Koalas were recorded using young eucalypt plantations at 7 sites and remnant forest and woodland at 7 sites. Both radio‐collared Koalas used eucalypt plantations more than expected based on the availability of this land cover type in their home‐ranges. Occupancy of young eucalypt plantations and remnant patches by Koalas was strongly influenced by the proximity of these sites to remnant vegetation.     

Quantifying uncertainty in estimates of C emissions from above-ground biomass due to historic land-use change to cropping in Australia

Quantifying continental scale carbon emissions from the oxidation of above‐ground plant biomass following land‐use change (LUC) is made difficult by the lack of information on how much biomass was present prior to vegetation clearing and on the timing and location of historical LUC. The considerable spatial variability of vegetation and the uncertainty of this variability leads to difficulties in predicting biomass C density (t_C ha^?1) prior to LUC. The issue of quantifying uncertainties in the estimation of land based sources and sinks of CO₂, and the feasibility of reducing these uncertainties by further sampling, is critical information required by governments world‐wide for public policy development on climate change issues. A quantitative statistical approach is required to calculate confidence intervals (the level of certainty) of estimated cleared above‐ground biomass. In this study, a set of high‐quality observations of steady state above‐ground biomass from relatively undisturbed ecological sites across the Australian continent was combined with vegetation, topographic, climatic and edaphic data sets within a Geographical Information System. A statistical model was developed from the data set of observations to predict potential biomass and the standard error of potential biomass for all 0.05° (approximately 5 × 5 km) land grid cells of the continent. In addition, the spatial autocorrelation of observations and residuals from the statistical model was examined. Finally, total C emissions due to historic LUC to cultivation and cropping were estimated by combining the statistical model with a data set of fractional cropland area per land grid cell, f_Ac (Ramankutty & Foley 1998). Total C emissions from loss of above‐ground biomass due to cropping since European colonization of Australia was estimated to be 757 Mt_C. These estimates are an upper limit because the predicted steady state biomass may be less than the above‐ground biomass immediately prior to LUC because of disturbance. The estimated standard error of total C emissions was calculated from the standard error of predicted biomass, the standard error of f_Ac and the spatial autocorrelation of biomass. However, quantitative estimates of the standard error of f_Ac were unavailable. Thus, two scenarios were developed to examine the effect of error in f_Ac on the error in total C emissions. In the first scenario, in which f_Ac was regarded as accurate (i.e. a coefficient of variation, CV, of f_Ac = 0.0), the 95% confidence interval of the continental C emissions was 379–1135 Mt_C. In the second scenario, a 50% error in estimated cropland area was assumed (a CV of f_Ac = 0.50) and the estimated confidence interval increased to between 350 and 1294 Mt_C. The CV of C emissions for these two scenarios was 25% and 29%. Thus, while accurate maps of land‐use change contribute to decreasing uncertainty in C emissions from LUC, the major source of this uncertainty arises from the prediction accuracy of biomass C density. It is argued that, even with large sample numbers, the high cost of sampling biomass carbon may limit the uncertainty of above‐ground biomass to about a CV of 25%.     

Effects of leaf litter on woody seedlings in xeric successional communities

We investigated the effect of leaf litter on the establishment of Eucalyptus incrassata, a mallee eucalypt. It has been suggested that litter accumulation may hinder seedling establishment, and that the removal of litter may be one of the mechanisms through which fire enhances recruitment. We conducted factorial experiments testing the effects of three kinds of leaf litter on E. incrassata seeds and seedlings at three contiguous sites with different land use histories. One site was an uncleared E. incrassata open mallee woodland (Mallee site), one a cleared area that had been ungrazed for about five years (Pasture site) and the third an area of mallee rolled some 40 years ago and permitted to regenerate (Regrowth site). Litter had no effect on emergence of planted E. incrassata seeds, but emergence differed between sites. Overall, the percentage of seeds that germinated and emerged was substantial (mean 35.2% ± 25.9%). Seedling shoot biomass did not differ between sites or litter treatments. Although seedlings grown in Pasture litter suffered higher mortality rates, overall mortality rates were low (mean 13.2% ± 15.5%), suggesting that leaf litter has little effect on recruitment rates during winter and spring. We conclude that leaf litter does not affect emergence or growth in young E. incrassata seedlings during winter and spring, when most establishment occurs. Our results emphasize the difficulty in predicting litter effects on recruitment.     

Strong “bottom‐up” influences on small mammal populations: State‐space model analyses from long‐term studies

“Bottom‐up” influences, that is, masting, plus population density and climate, commonly influence woodland rodent demography. However, “top‐down” influences (predation) also intervene. Here, we assess the impacts of masting, climate, and density on rodent populations placed in the context of what is known about “top‐down” influences. To explain between‐year variations in bank vole Myodes glareolus and wood mouse Apodemus sylvaticus population demography, we applied a state‐space model to 33 years of catch‐mark‐release live‐trapping, winter temperature, and precise mast‐collection data. Experimental mast additions aided interpretation. Rodent numbers in European ash Fraxinus excelsior woodland were estimated (May/June, November/December). December–March mean minimum daily temperature represented winter severity. Total marked adult mice/voles (and juveniles in May/June) provided density indices validated against a model‐generated population estimate; this allowed estimation of the structure of a time‐series model and the demographic impacts of the climatic/biological variables. During two winters of insignificant fruit‐fall, 6.79 g/m² sterilized ash seed (as fruit) was distributed over an equivalent woodland similarly live‐trapped. September–March fruit‐fall strongly increased bank vole spring reproductive rate and winter and summer population growth rates; colder winters weakly reduced winter population growth. September–March fruit‐fall and warmer winters marginally increased wood mouse spring reproductive rate and September–December fruit‐fall weakly elevated summer population growth. Density dependence significantly reduced both species' population growth. Fruit‐fall impacts on demography still appeared after a year. Experimental ash fruit addition confirmed its positive influence on bank vole winter population growth with probable moderation by colder temperatures. The models show the strong impact of masting as a “bottom‐up” influence on rodent demography, emphasizing independent masting and weather influences; delayed effects of masting; and the importance of density dependence and its interaction with masting. We conclude that these rodents show strong “bottom‐up” and density‐dependent influences on demography moderated by winter temperature. “Top‐down” influences appear weak and need further investigation.     

Local population success in heterogeneous habitats: reciprocal transplant experiments completed on a desert spider

Reciprocal transplant experiments were completed to test for selection against the mixing of behavioural phenotypes in a desert spider. Most Agelenopsis aperta populations experience low prey abundances and competition for web‐sites that provide shelter from thermal extremes. These conditions favour aggressiveness towards both prey and conspecifics (an ‘arid‐land behavioural phenotype’). The spider also occupies narrow stretches of riparian habitat bordering spring‐fed streams and rivers. Here it is released from competition for prey and foraging sites, but is subject to predation by birds. A less aggressive/more fearful behaviour is selected for in these riparian habitats (a ‘riparian behavioural phenotype’). Previous work with this spider indicates that there is genetic differentiation between arid‐land and riparian populations. However, the degree to which genetic differentiation is achieved may be limited by gene flow. Reciprocal sets of enclosures were established in: (1) a dry evergreen woodland site (arid‐land phenotype) and (2) a neighbouring riparian site (riparian phenotype) in south‐eastern Arizona. Equal numbers of field collected, early instar A. aperta were introduced into native and transplant enclosures in each habitat. After 6 months of site‐imposed selection, survivorship was determined and growth estimates and behavioural trials completed on spiders remaining in the different enclosures. The same behavioural test was subsequently applied to lab‐reared offspring of the spiders surviving the respective selection regimes. Riparian transplants showed both poor survival and retarded growth in the dry woodland habitat when compared with both arid‐land and riparian natives. Arid‐land transplants that survived, however, grew equally well in riparian habitat as did dry woodland and riparian natives. Behavioural assays conducted on test subjects after selection and on their offspring reared in a controlled laboratory environment indicate that phenotypes that were inappropriate to the respective habitats were selected against in the transplant experiments. The frequency distribution of transplant spider behaviour on a continuum from fearful to aggressive was intermediate between that exhibited by respective native riparian and dry woodland spiders. It is concluded that while arid‐land and riparian behavioural ecotypes do exist, directional gene flow of arid‐land phenotypes into riparian habitat limits population subdivision.     

Recovery after African Olive invasion: can a ‘bottom‐up’ approach to ecological restoration work?

African Olive (Olea europaea ssp. cuspidata) is a densely crowned evergreen small tree, native to eastern Africa that is highly invasive in areas where it has been introduced, including Hawaii and Australia. Invasion by African Olive threatens Cumberland Plain Woodland, a critically endangered grassy eucalypt woodland from western Sydney, Australia, through the formation of a dense mid‐canopy excluding the regeneration of native species. We established a 3‐year field experiment to determine the effectiveness of direct seeding and fire, as techniques for early stage restoration of a 2 ha historically cleared and degraded Cumberland Plain Woodland site after the removal of African Olive. Direct seeding was able to re‐establish a native perennial grass cover which was resistant to subsequent weed invasion and could be managed as an important first stage in woodland restoration with fire and selective herbicide. Fire was able to stimulate some germination of colonising native species from the soil seed bank after 15 years of African Olive invasion; however, germination and establishment of native shrubs from the applied seed mix was poor. We propose a ‘bottom‐up’ model of ecological restoration in such highly degraded sites that uses a combination of direct seeding and stimulation of the soil seed bank by fire, which could be applicable to other degraded grassy woodland sites and plant communities.     

Understanding the changing value of natural resources: an integrated palaeoecological–historical investigation into grazing–woodland interactions by Loch Awe, Western Highlands of Scotland

Aim We aim to compare fine resolution pollen data from a former seasonal pasture with historical evidence for grazing and woodland use. We discuss the complexities and benefits of integrating qualitative and quantitative information, and the implications for studies of past wood–grazing interactions and their relevance to current conservation management. Location Corries is an abandoned farm township in Scotland's Western Highlands. Methods Two sources were used: (1) pollen evidence from a former seasonal pasture, analysed at c. 20‐year intervals and dated using ¹⁴C and ²¹⁰Pb, provides a c. 1100‐year local vegetation and land‐use history; (2) written sources document resource regulation and changing socio‐economic circumstances at local to national scales over the last c. 400 years. Results Each source records woodland and livestock management at different spatial and temporal scales: written evidence provides a clearer understanding of general (estate) rather than farm‐scale changes, while small pollen basins record localized woodland–grazing dynamics, which can be difficult to extrapolate to the landscape scale. Both sources indicate a dynamic wood–grazing balance and together provide clearer evidence for incentives and drivers controlling this relationship. The first palynological phase of woodland incursion (ad c. 1210–1490) pre‐dates the surviving written records, but a second (ad c. 1680–1760) occurs during a period of increasing market value for cattle, when farmers may have increased grazing despite regulations to protect woods. The site is not representative of grazing intensification associated with the introduction of extensive sheep farming because the farmer protected the woods (ad c. 1760–1880) until they were cleared (ad c. 1880–1920) for quarrying (ad 1885–1904), which accounts for the limited palynological evidence for grazing. Main conclusions Written evidence for past stocking levels is too fragmentary and ambiguous to allow long‐term quantitative analysis, but a local historical context is important for interpreting local pollen records. Management decisions that determined grazing–woodland interactions were shaped by changing values, markets, agricultural practices and regulatory structures, which can result in nonlinear relationships between stocking levels and woodland continuity. Many woods were managed for multiple purposes in the past and promoting natural processes or pursuing pre‐anthropogenic baselines will result in the erosion of cultural features that have shaped present landscape values.     

Stem diameter growth rates in a fire‐prone savanna correlate with photosynthetic rate and branch‐scale biomass allocation,but not specific leaf area

Plant growth rates strongly determine ecosystem productivity and are a central element of plant ecological strategies. For laboratory and glasshouse‐grown seedlings, specific leaf area (SLA; ratio of leaf area to mass) is a key driver of interspecific variation in growth rate (GR). Consequently, SLA is often assumed to drive GR variation in field‐grown adult plants. However, there is an increasing evidence that this is not the general case. This suggests that GR – SLA relationships (and perhaps those for other traits) may vary depending on the age or size of the plants being studied. Here we investigated GR – trait relationships and their size dependence among 17 woody species from an open‐canopy, fire‐prone savanna in northern Australia. We tested the predictions that SLA and stem diameter growth rate would be positively correlated in saplings but unrelated in adults while, in both age classes, faster‐GR species would have higher light‐saturated photosynthetic rate (A_sat), higher leaf nutrient concentrations, higher branch‐scale biomass allocation to leaf versus stem tissues and lower wood density (WD). SLA showed no relationship to stem diameter GR, even in saplings, and the same was true of leaf N and P concentrations, and WD. However, branch‐scale leaf:stem allocation was strongly related to GR in both age groups, as was A_sat. Together, these two traits accounted for up to 80% of interspecific variation in adult GR, and 41% of sapling GR. A_sat is rarely measured in field‐based GR studies, and this is the first report of branch‐scale leaf:stem allocation (analogous to a benefit:cost ratio) in relation to plant growth rate. Our results suggest that we may yet find general trait‐drivers of field growth rates, but SLA will not be one.     

Effect of prey availability on the abundance of White‐breasted Wood‐Wrens,insectivorous birds of tropical lowland forests

Some understory insectivorous birds manage to persist in tropical forest fragments despite significant habitat loss and forest fragmentation. Their persistence has been related to arthropod biomass. In addition, forest structure has been used as a proxy to estimate prey availability for understory birds and for calculating prey abundance. We used arthropod biomass and forest structural variables (leaf area index [LAI] and aerial leaf litter biomass) to explain the abundance of White‐breasted Wood‐Wrens (Henicorhina leucosticta), tropical understory insectivorous birds, in six forests in the Caribbean lowlands of Costa Rica. To estimate bird abundance, we performed point counts (100‐m radius) in two old‐growth forests, two second‐growth forests, and two selectively logged forests. Arthropod abundance was the best predictor of wood‐wren abundance (wi = 0.75). Wood‐wren abundance increased as the number of arthropods increased, and the estimated range of bird abundance obtained from the model varied from 0.51 (0.28 – 0.93 [95%CI]) to 3.70 (1.68 – 5.20 [95%CI]) within sites. LAI was positively correlated to prey abundance (P = 0.01), and explained part of the variation in wood‐wren abundance. In forests with high LAI, arthropods have more aerial leaf litter as potential habitat so more potential prey are available for wood‐wrens. Forests with a greater abundance of aerial leaf litter arthropods were more likely to sustain higher densities of wood‐wrens in a fragmented tropical landscape.