Woodland System Research Articles

Alteration of a temperate forest invertebrate community by invasive Japanese barberry (Berberis thunbergii) has limited influence on the diet composition of territorial ovenbirds (Seiurus aurocapilla)

Invasive species are widely implicated in the decline of songbird populations, potentially via indirect effects such as the restructuring of ecological communities by non-native plants. We used stable isotope analysis to investigate whether ground-foraging, generalist insectivore ovenbirds ( Seiurus aurocapilla (Linnaeus, 1766)) shifted diets following invasion by a non-native shrub, Japanese barberry ( Berberis thunbergii DC.), in a temperate woodland system in New York, USA where barberry was previously linked to trophic downgrading in the leaf litter arthropod community. Assimilated ovenbird diets were primarily composed of predatory invertebrates followed by sucking herbivores, chewing herbivores, and detritivores. The only notable changes in assimilated ovenbird diets were a modest 14.7% decrease in chewing herbivore contributions and a minor 7.0% increase in sucking herbivore contributions in forest patches with high barberry densities. Our results indicate that the effects of non-native plants on connections between higher trophic levels are context-dependent, and comparisons with other studies suggest that community complexity and time since introduction are key contextual differences that affect the outcome of an invasion. Our results may reflect compensatory shifts in individual foraging effort by ovenbirds, but, in combination with our previous research, provide little evidence that barberry affects ovenbird condition and therefore downstream outcomes.

Evaluating Data Inter-Operability of Multiple UAV–LiDAR Systems for Measuring the 3D Structure of Savanna Woodland

For vegetation monitoring, it is crucial to understand which changes are caused by the measurement setup and which changes are true representations of vegetation dynamics. UAV–LiDAR offers great possibilities to measure vegetation structural parameters; however, UAV–LiDAR sensors are undergoing rapid developments, and the characteristics are expected to keep changing over the years, which will introduce data inter-operability issues. Therefore, it is important to determine whether datasets acquired by different UAV–LiDAR sensors can be interchanged and if changes through time can accurately be derived from UAV–LiDAR time series. With this study, we present insights into the magnitude of differences in derived forest metrics in savanna woodland when three different UAV–LiDAR systems are being used for data acquisition. Our findings show that all three systems can be used to derive plot characteristics such as canopy height, canopy cover, and gap fractions. However, there are clear differences between the metrics derived with different sensors, which are most apparent in the lower parts of the canopy. On an individual tree level, all UAV–LiDAR systems are able to accurately capture the tree height in a savanna woodland system, but significant differences occur when crown parameters are measured with different systems. Less precise systems result in underestimations of crown areas and crown volumes. When comparing UAV–LiDAR data of forest areas through time, it is important to be aware of these differences and ensure that data inter-operability issues do not influence the change analysis. In this paper, we want to stress that it is of utmost importance to realise this and take it into consideration when combining datasets obtained with different sensors.

A comparison of sampling methods and temporal patterns of arthropod abundance and diversity in a mature, temperate, Oak woodland

Arthropods underpin fundamental ecological processes such as herbivory, pollination and nutrient cycling, and are often responsive to subtle changes in environmental conditions. Thus, changes in their abundance and phenology may be crucial indicators of system-wide responses to climate change.The new Birmingham Institute for Forest Research (BIFoR) Free Air Carbon Dioxide Enrichment (FACE) facility provides a unique opportunity assess arthropod diversity and abundance in mature deciduous forest and the effect of sampling method and seasonality. This is an essential first step before attempting to measure the potential impacts of climate change, such as elevated CO2, on arthropod populations. Two fundamental criteria are: i) diverse sampling methods in order to effectively assess diversity and in particular, differences between structural layers of the woodland system, e.g., ground, sub-canopy and canopy layers, ii) a temporal resolution that can identify seasonal patterns of change (phenology). This paper sets out the methodological approaches employed to achieve these objectives.A total of 22,568 invertebrates from 108 families were sampled across 12 months of continuous sampling using a range of techniques from forest floor to canopy. Diptera were the most abundant order sampled and had the greatest number of families represented (45). Phenology patterns generally followed the anticipated seasonal cycle, with increasing abundance and diversity from spring to summer. Temperature was the best environmental predictor of abundance within Malaise and pitfall traps. Precipitation was not correlated with any monthly patterns of trap data. Yellow pan traps collected more arthropods than white or blue traps. Canopy beating yielded a greater diversity than that in the understory samples.These data provide an important baseline from which to assess any future impacts of eCO2 over the 10-year BIFoR FACE experiment, and highlight the importance of employing diverse sampling methods, temporal replication and measuring environmental factors over appropriate timescales.

Elevated CO2 Impacts on Plant–Pollinator Interactions: A Systematic Review and Free Air Carbon Enrichment Field Study

Simple SummaryClimate change is having a profound impact on pollination systems, yet we still do not know to what extent increasing concentrations of carbon dioxide (CO2) will directly affect the interactions between plants and their pollinators. We review all the existing published literature on the effect of elevated CO2 (eCO2) on flowering time, nectar and pollen production and plant–pollinator interactions. We also conduct a field experiment to test the effect of eCO2 on bluebells and their pollinators. We found that few studies have assessed the impact of eCO2 on pollination, and our field data found that bluebells flowered on average 6 days earlier under eCO2 conditions. Hoverflies and bumble bees were the main visitors to bluebell flowers, but insect activity was low early in the flowing period. Although we did not find a difference in the number of visits made by insects to bluebell flowers under eCO2, or the amount of seeds those flowers produced, the change in the timing of flowering could mean that a mismatch could develop between bluebells and their pollinators in the future, which would affect pollination success.The impact of elevated CO2 (eCO2) on plant–pollinator interactions is poorly understood. This study provides the first systematic review of this topic and identifies important knowledge gaps. In addition, we present field data assessing the impact of eCO2 (150 ppm above ambient) on bluebell (Hyacinthoides non-scripta)–pollinator interactions within a mature, deciduous woodland system. Since 1956, only 71 primary papers have investigated eCO2 effects on flowering time, floral traits and pollination, with a mere 3 studies measuring the impact on pollination interactions. Our field experiment documented flowering phenology, flower visitation and seed production, as well as the abundance and phenology of dominant insect pollinators. We show that first and mid-point flowering occurred 6 days earlier under eCO2, but with no change in flowering duration. Syrphid flies and bumble bees were the dominant flower visitors, with peak activity recorded during mid- and late-flowering periods. Whilst no significant difference was recorded in total visitation or seed set between eCO2 and ambient treatments, there were clear patterns of earlier flowering under eCO2 accompanied by lower pollinator activity during this period. This has implications for potential loss of synchrony in pollination systems under future climate scenarios, with associated long-term impacts on abundance and diversity.

Woody plant richness does not influence invertebrate community reassembly trajectories in a tree diversity experiment.

Understanding the relationship between plant diversity and diversity at higher trophic levels is important from both conservation and restoration perspectives. Although there is strong evidence for bottom-up maintenance of biodiversity, this is based largely on studies of simplified grassland systems. Recently, studies in the TreeDivNet global network of tree diversity experiments have begun to test whether these findings are generalizable to more complex ecosystems, such as woodlands. We monitored invertebrate community reassembly over 5yr of experimental woodland restoration at the TreeDivNet Ridgefield site in southwest Australia, testing the effects of woody plant species richness and herb-layer manipulation on invertebrate community structure and ant species composition. From 2010 to 2014, we sampled ground-dwelling invertebrates using pitfall traps in herbicide vs. no-herbicide subplots nested within each of 10 woody plant treatments varying in richness from zero (bare controls) to eight species, which produced a total of 211, 235 invertebrates, including 98, 979 ants belonging to 74 species. In mixed model analyses, the presence of woody plants was an important driver of faunal community reassembly (relative to bare control plots), but faunal responses to woody plant treatment combinations were idiosyncratic and unrelated to woody plant richness across treatments. We also found that a herbicide-induced reduction in herbaceous plant cover and richness had a positive effect on ant richness and caused more rapid convergence of invertebrate community composition toward the composition of a woodland reference site. These findings show that woody plant richness did not have direct positive effects on the diversity and community reassembly trajectories of higher trophic levels in our woodland system. From a management perspective, this suggests that even low-diversity restoration or carbon sequestration plantings can potentially lead to faunal reassembly outcomes that are comparable to more complex re-planting designs.

Two new non-spiny Solanum (Solanaceae) from the Gran Chaco Americano and a key for the herbaceous glandular-pubescent solanums from the region.

The Gran Chaco Americano is a major savanna woodland system in South America that harbours great plant and animal diversity. Two new herbaceous species of the Morelloid clade of Solanum (largely corresponding to the traditional Solanum section Solanum) are described here from the Bolivian Chaco. Both species are morphologically similar to a group of related species with glandular pubescence and enlarged, foliaceous calyces that includes Solanum atriplicifolium Gillies ex Nees, Solanum nitidibaccatum Bitter, Solanum physalifolium Rusby, Solanum sarrachoides Sendtn. and Solanum tweedianum Hook. Solanum woodii Särkinen & S.Knapp, sp. nov. is unusual in the Morelloid clade in having tapering anthers on short filaments, and is superficially similar to the unrelated Solanum anomalostemon S.Knapp & M.Nee from dry forests in Peru. Solanum michaelis Särkinen & S.Knapp, sp. nov. is distinct in its enlarged calyx with a short tube and long lobes that apparently reflex at fruit maturity. Both new taxa are illustrated, their conservation status assessed, and their distributions mapped. We also provide a key to the glandular-pubescent herbaceous Solanum species of the Chaco vegetation to aid in identification of these taxa.

Insect herbivory in a mature Eucalyptus woodland canopy depends on leaf phenology but not CO2 enrichment.

BackgroundClimate change factors such as elevated atmospheric carbon dioxide concentrations (e[CO2]) and altered rainfall patterns can alter leaf composition and phenology. This may subsequently impact insect herbivory. In sclerophyllous forests insects have developed strategies, such as preferentially feeding on new leaf growth, to overcome physical or foliar nitrogen constraints, and this may shift under climate change. Few studies of insect herbivory at elevated [CO2] have occurred under field conditions and none on mature evergreen trees in a naturally established forest, yet estimates for leaf area loss due to herbivory are required in order to allow accurate predictions of plant productivity in future climates. Here, we assessed herbivory in the upper canopy of mature Eucalyptus tereticornis trees at the nutrient-limited Eucalyptus free-air CO2 enrichment (EucFACE) experiment during the first 19 months of CO2 enrichment. The assessment of herbivory extended over two consecutive spring—summer periods, with a first survey during four months of the [CO2] ramp-up phase after which full [CO2] operation was maintained, followed by a second survey period from months 13 to 19.ResultsThroughout the first 2 years of EucFACE, young, expanding leaves sustained significantly greater damage from insect herbivory (between 25 and 32 % leaf area loss) compared to old or fully expanded leaves (less than 2 % leaf area loss). This preference of insect herbivores for young expanding leaves combined with discontinuous production of new foliage, which occurred in response to rainfall, resulted in monthly variations in leaf herbivory. In contrast to the significant effects of rainfall-driven leaf phenology, elevated [CO2] had no effect on leaf consumption or preference of insect herbivores for different leaf age classes.ConclusionsIn the studied nutrient-limited natural Eucalyptus woodland, herbivory contributes to a significant loss of young foliage. Leaf phenology is a significant factor that determines the level of herbivory experienced in this evergreen sclerophyllous woodland system, and may therefore also influence the population dynamics of insect herbivores. Furthermore, leaf phenology appears more strongly impacted by rainfall patterns than by e[CO2]. e[CO2] responses of herbivores on mature trees may only become apparent after extensive CO2 fumigation periods.Electronic supplementary materialThe online version of this article (doi:10.1186/s12898-016-0102-z) contains supplementary material, which is available to authorized users.

A Temperate Ridge–Cliff–Talus System In An Urban Setting: Rock Rimmon In Manchester, New Hampshire

An unusual temperate ridge–cliff–talus system exists at Rock Rimmon in urban Manchester, New Hampshire. Recent surveys and historical data indicate that five natural communities occur within the system, of which three are critically imperiled in New Hampshire: Appalachian wooded talus, pitch pine–Appalachian oak–heath forest, and pitch pine rocky ridge. The remaining two natural communities are occasional in the state: Appalachian oak–pine rocky ridge and temperate acidic cliff. Seven plant taxa previously or currently recorded at Rock Rimmon are rare (SH, S1, or S2) in New Hampshire; four other taxa are uncommon (S3) in the state. We re-located two previously recorded rare taxa during our 2012 survey. Digitaria filiformis var. laeviglumis, a globally rare crabgrass, is endemic to this biodiversity hotspot, but was not re-located. In addition, four other rare plant taxa were not re-located, and all are likely extirpated as a result of the lengthy history of human-related disturbance at the site. The temperate ridge–cliff–talus system closely corresponds to NatureServe's central Appalachian pine–oak rocky woodland system, which is distributed from Maine to Virginia west to Kentucky and Ohio. Xerophytic oak and pine dominate across the range of this system type, although many canopy species differ along a latitudinal gradient.

Managing semi-arid woodlands for carbon storage: Grazing and shrub effects on above- and belowground carbon

Shrub cover has increased in semi-arid regions worldwide. This change has generally been viewed as land degradation, due to shrub-induced declines in pastoral productivity. As a consequence, widespread management treatments to reduce shrub density have been applied in many pastoral areas. These treatments, however, often do not have long-term positive benefits for forage production. Alternative uses for shrub-encroached lands have received little consideration, but a recent move towards economic incentives for carbon (C) storage could lead to financially viable alternative land management strategies. We examined changes in above- and belowground C storage following 20 years of factorial land management treatments (grazing/no grazing and shrub removal/no removal) in an Australian semi-arid woodland. Disturbance by shrub removal (root ploughing) and/or livestock grazing significantly reduced the amount of soil organic carbon (SOC). The most disturbed treatment (grazed and ploughed) contained the least SOC (15.30MgCha−1) while protection from grazing and shrub removal led to the greatest SOC (28.49MgCha−1). Declines in SOC in shrub removal treatments (with and without grazing) were compensated, in part, by enhanced aboveground C accumulation, derived mainly from woody plants. Destocking currently grazed shrublands for two decades resulted in a net C accretion, over 20 years, in the order of 6.5Mgha−1, almost entirely through increasing belowground C. At the current price for C in Australia, the economic benefit for C accumulation from removing livestock grazing would be similar to the economic benefit of grazing. The results suggest that C farming in this semi-arid woodland system may offer an economically viable alternative management strategy to grazing, although uncertainties in future climate, C credit value, and assessment protocols present hurdles for implementing alternative management aimed at C farming.

Local habitat characteristics but not landscape urbanization drive pollinator visitation and native plant pollination in forest remnants

Habitat loss from urban development threatens native plant populations in many regions of the world. In addition to direct plant mortality, urban intensification potentially impacts pollinator communities and in turn disrupts the pollination mutualisms that are critical to the viability of native plant populations. We placed standardized flowering plant arrays into woodlands along a gradient of increasing urban land use to simultaneously quantify landscape-scale and local-scale effects on pollinators and on reproduction of two spring ephemeral wildflowers (Claytonia virginica and Polemonium reptans) in woodland fragments in the Mid-Atlantic Region of North America. Greater pollinator abundance and associated diversity significantly reduced the degree of pollen limitation, demonstrating that pollinator populations are critical to successful pollination of these plant populations. However, landscape-scale habitat loss did not reduce pollinator abundance or diversity. Habitat loss at the landscape scale therefore does not appear to drive changes in pollination in this woodland system. Rather, local-scale habitat characteristics were more important, with pollinators being more abundant in brighter woodland patches for one plant species, and in larger patches for the other species. Because we found abundant pollinators and adequate pollination even in isolated, urban woodland fragments, our results are encouraging for the conservation of both plants and pollinators in urban landscapes.

基于智能体模型的青岛市林地生态格局评价与优化

设计并在GIS平台上开发了基于智能体的生态格局评价模型,以青岛市及周边地区林地为研究对象,分析不同林地空间格局及生态网络保护框架对于物种生存与扩散的影响。结果表明,与现状相比,不同等级的生态网络框架对物种种群数量与物种迁移都有明显提升,且等级越高的生态网络框架提升作用越明显。然而仅仅依靠生态网络框架不足以使研究区域林地系统形成功能上的相互连通,因此,在分析研究区域现状土地利用格局基础上,提出与湿地系统结合,在胶州湾周围及大沽河干流地区增加林地的空间布局。通过模型模拟分析,发现优化后的林地空间格局结合生态网络框架能有效提升林地之间的物种扩散。基于模拟结果,为研究区林地生态格局构建提出如下建议:(1)保证现有的规模较大的林地不被破坏;(2)青岛市中部湿地系统可以作为新增林地的理想区域;(3)生态网络框架可作为青岛市建立城市组团间生态间隔的空间参考。;Urban socio-economic development and urban spatial expansion has led to the loss and fragmentation of habitat. Global climate change adds to the gravity of these effects. The survival of wildlife species is subjected to enormous pressure due to natural environmental changes and human activities. Agent-based models (ABMs) are computer simulation models analyzing and simulating human or animal behavior through the integration of learning, adaptation, evolution and logical analysis. ABMs study the overall system characteristics by analyzing internal elements of the system (such as the interaction among individual agents, and agents with the environment) with a bottom-up approach. The agents in ABMs can complete given objectives, perceive and respond to changes of the external environment through the default logic control, and respond to stimuli from other agents and the external environment through learning and adaptation functions. This paper designed an agent-based evaluation model of an ecological pattern, which was used to analyze the impact of different woodland patterns on species survival and dispersal. The model focused on the logic control of survival and dispersal of agents, and used the dispersal strategy integrating CRW and LW models, which combines the advantages of these two models. The survival of the agent is control by the age-specified U-shaped survival curve and determination function considering their own energy and environmental risks. The model was developed on the GIS platform, realizing the seamless integration of the agent model and GIS, which could then be applied to real geographical environment simulation. Qingdao is a city located in the eastern coastal region of China where the economy is relatively well-developed. The region is also where marine and terrestrial ecosystems meet. Woodland is mainly distributed in the Laoshan Mountains in the east, the Daze Mountains in the north, and the Dazhu, Xiaozhu and Tiejue Mountains in the south. In the study area, the ecological environment is deteriorating, and various wildlife species are being impacted, with some species being endangered or facing extinction. This paper selected the woodlands in the Qingdao district as the study object, analyzing the effect of different spatial patterns on the survival and spread of woodland species. Simulation results showed that, compared with the original state, species populations and migration have improved significantly under different levels of ecological network framework, and the higher the level of ecological network framework, the more obvious the improvement. The distance between patches had a large influence on the dispersal of simulated species because they were not able to arrive at patches that were far away from the original patch. Therefore, this paper makes the suggestion that an approach integrating wetland and woodland systems could strengthen woodland system functional contact in the study area. It is suggested that the region around Jiaozhou Bay and the mainstream of Dagu River be used to increase the spatial distribution of woodland. Based on the simulation results, suggestions for the woodland ecological pattern construction are given below: (1) ensure that the large woodland can not be destroyed; (2) the wetland system district in the middle of Qingdao is an ideal place for a new woodland construction; (3) the ecological network framework can be used as a spatial reference for an ecological barrier to prevent the spread of urban land into woodland.

Blue oak stump sprouting evaluated after firewood harvest in northern Sacramento Valley

Colifornia's hardwood rangelands, an oak-dominated woodland system, cover 10 million acres. More than 80% of these lands are privately owned, with two-thirds grazed by domestic livestock. Public concerns about long-term damage to habitat in areas harvested for firewood — particularly in the northern Sacramento Valley — led to this study of resprouting, to assess long-term trends in oak cover following harvesting and the potential of sprout (coppice) management to sustain woodlands. In field surveys on 103 sample plots at 19 ranches where oak firewood was harvested, we found that 54% of all oak stumps resprouted. Stump diameter, herbicide application, overstory crown cover percentage, and slope and aspect were significant variables in models developed to assess the probability of stump sprouting. Ten-year sprout height and crown growth models were developed, and livestock grazing, residual overstory canopy, herbicide treatment and stump diameter were found to be significant variables. These models can be used to predict stand development following firewood harvest and can be integrated with forage growth, wildlife habitat and residual tree growth models.

Quantifying variance components in ecological models based on expert opinion

1. Expert opinion is often relied on to build ecological models when empirical data are absent. Despite widespread use, expert models often ignore uncertainty though it may affect predictions. We assess the importance of such uncertainty for modelling forest restoration. 2. Of an initial 19 experts found using a literature search and peer recommendations, five parameterized models predicting ecological responses to proposed restoration actions for a degraded dry woodland system in Victoria, Australia. We incorporated uncertainty from three sources: disagreement (between-expert uncertainty), self-assessed imprecision (within-expert uncertainty) and modelled system stochasticity. These sources of uncertainty were quantified as variance components in hierarchical models. 3. The between-expert variance component contributed more to overall model uncertainty than both within-expert variance and modelled system stochasticity. The estimate of between-expert variance also had the greatest parameter uncertainty of the three components. 4. Synthesis and applications. We present a method to decompose variance in model predictions. We suggest that modelling strategies relying on a single expert opinion, consensus between experts, or that only incorporate uncertainty due to system stochasticity could produce biased models and over-confident predictions. Management decisions based on biased and over-confident predictions lead to inefficient conservation investments and poor outcomes. Our research highlights the importance of seeking multiple expert opinions to fully characterize uncertainty and make robust decisions.

Method for evaluation of coarse cork oak root system by means of digital imaging

Digital imaging is becoming a powerful tool for data storage and information retrieval. Image comparison and similarity evaluation has become part of the information market and it is today a common part of, for example, web search engines. The cork oak tree (Quercus suber L.), the dominant species of the ‘montado’ woodland system is, due to its cultural and socio-economic value, protected by law that prevents extensive destructive studies on an essential part of the tree—the root. Especially in the Mediterranean zone, where the water is the limiting growth factor, the root development studies are of significant interest. In this work we present a method of using digital images for cork oak coarse root systems-evaluation by means of digital imaging. Acquired images of structural roots are processed automatically to prevent subjective decisions by the human observer. The performance of the method, its potential for semantic retrieval and similarity assessment is demonstrated, having as example eight young cork oak root systems, and critical issues for evaluation and conclusion-making, are discussed.

Tree decline and the future of Australian farmland biodiversity

Farmland biodiversity is greatly enhanced by the presence of trees. However, farmland trees are declining worldwide, including in North America, Central America, and parts of southern Europe. We show that tree decline and its likely consequences are particularly severe in Australia's temperate agricultural zone, which is a threatened ecoregion. Using field data on trees, remotely sensed imagery, and a demographic model for trees, we predict that by 2100, the number of trees on an average farm will contract to two-thirds of its present level. Statistical habitat models suggest that this tree decline will negatively affect many currently common animal species, with predicted declines in birds and bats of up to 50% by 2100. Declines were predicted for 24 of 32 bird species modeled and for all of six bat species modeled. Widespread declines in trees, birds, and bats may lead to a reduction in economically important ecosystem services such as shade provision for livestock and pest control. Moreover, many other species for which we have no empirical data also depend on trees, suggesting that fundamental changes in ecosystem functioning are likely. We conclude that Australia's temperate agricultural zone has crossed a threshold and no longer functions as a self-sustaining woodland ecosystem. A regime shift is occurring, with a woodland system deteriorating into a treeless pasture system. Management options exist to reverse tree decline, but new policy settings are required to encourage their widespread adoption.

Collapse of an avifauna: climate change appears to exacerbate habitat loss and degradation

AbstractAim We characterized changes in reporting rates and abundances of bird species over a period of severe rainfall deficiency and increasing average temperatures. We also measured flowering in eucalypts, which support large numbers of nectarivores characteristic of the region.Location A 30,000‐km2 region of northern Victoria, Australia, consisting of limited amounts of remnant native woodlands embedded in largely agricultural landscapes.Methods There were three sets of monitoring studies, pitched at regional (survey programmes in 1995–97, 2004–05 and 2006–08), landscape (2002–03 and 2006–07) and site (1997–2008 continuously) scales. Bird survey techniques used a standard 2‐ha, 20‐min count method. We used Bayesian analyses of reporting rates to document statistically changes in the avifauna through time at each spatial scale.Results Bird populations in the largest remnants of native vegetation (up to 40,000 ha), some of which have been declared as national parks in the past decade, experienced similar declines to those in heavily cleared landscapes. All categories of birds (guilds based on foraging substrate, diet, nest site; relative mobility; geographical distributions) were affected similarly. We detected virtually no bird breeding in the latest survey periods. Eucalypt flowering has declined significantly over the past 12 years of drought.Main conclusions Declines in the largest woodland remnants commensurate with those in cleared landscapes suggest that reserve systems may not be relied upon to sustain species under climate change. We attribute population declines to low breeding success due to reduced food. Resilience of bird populations in this woodland system might be increased by active management to enhance habitat quality in existing vegetation and restoration of woodland in the more fertile parts of landscapes.

Chemical partitioning of Cu, Pb and Zn in the soil profile of a semi arid dry woodland

The chemical partitioning of Cu, Pb and Zn was examined in the soil profile of the woodland system in Keoladeo National Park, India using a five-step sequential extraction procedure (SEP). Metal partitioning was assessed in the soil up to a depth of 100cm with 25-cm intervals. The amount of metals obtained from the SEP exceeded pseudototal metal levels obtained from aqua regia digestion. The SEP results showed high preferential attachment of metals with Fe—Mn hydroxides. All the three metals showed least preferences to the exchangeable pool. The attachment of metals to the OM-S phase was also less, may be because of the low organic matter in the soil. In the case of Cu, the order of the fractions in terms of metal concentrations was Fe—Mn>RES>OM-S>CA>EXC and in the case of Pb the order was Fe—Mn>OM-S>RES>CA>EXC. Zn was different from Cu and Pb in showing higher affinity towards RES phase and the order of its concentration was RES>Fe—Mn>OM-S>EXC>CA. This suggests hydrous oxides of Fe—Mn as an important binding site for Cu and Pb, whereas silicate mineral matrix (RES phase) for Zn.

Do Exotic Vertebrates Structure the Biota of Australia? An Experimental Test in New South Wales

From 1993 to 2001, we conducted a series of experiments in a mixed grassland–woodland system in central New South Wales (NSW) to quantify the interactions between red foxes and their prey and competitors. Foxes were removed from two areas around the perimeter of Lake Burrendong, and data were collected from these areas and a nearby untreated area before, during, and after the period of fox control. The arrival of rabbit hemorrhagic disease (RHD) in 1996 provided an opportunity to examine the interactive effects of controlling foxes and rabbits. In this landscape, typical of central NSW, (a) the fox population was not affected by a large reduction in the abundance of rabbits, or vice versa; (b) the cat population declined in areas where foxes were removed after the large RHD-induced reduction in rabbit numbers, but there was no consistent response to the removal of foxes; (c) the abundance of some macropod species increased in response only to the combined removal of rabbits and foxes; (d) there were no consistent changes in the abundances of bird species in response to the removal of either foxes or rabbits, but there were clear habitat differences in bird species richness; and (e) there was likely to be an increase in woody plant species after the large reduction in rabbit populations by RHD. We conclude that (a) long-term field experiments (more than 3 years) are required to quantify the indirect consequences of controlling foxes and rabbits, and (b) single manipulations, such as fox control or rabbit control, are not necessarily sufficient for the conservation of remnant woodland communities in southeastern Australia.

The behaviour of the species mingling index M sp in relation to species dominance and dispersion

Ecosystem conservation plays an increasingly important role in forest management. The value for such conservation has been directly linked to high diversity of species and structure within systems. In the past, forestry inventory practices have concentrated on aspects that were primarily required for timber management. Now, however, much interest has arisen in measures that will indicate higher or lower diversity. The interspersion of trees of different species reflects diversity at a local level and may serve as an important indicator for the simplification of a forest or woodland system. This article shows that the mingling index M sp is robust in describing the spatial dispersion of plants; some guidelines for interpreting M sp are provided.

Natural ecosystems: Pattern and process in relation to local and landscape diversity in southwestern Australian woodlands

Natural woodland ecosystems in southwestern Australia are examined in terms of their spatial structure at three different scales. Fine-scale structure of the vegetation and soil surface has a strong influence on water capture and retention, resulting in mostly localised infiltration and use. Stand-scale structure results from the patchy distribution of canopy trees, regeneration patches and a diversity of understorey shrubs which provides a diverse above- and below-ground structure. At the landscape scale, broad vegetation patterns are related to soil and landform changes along catenas, but there are also finer-scale mosaics resulting from disturbance history, individualistic species distributions and more subtle physical/chemical changes. Complex patterns at all these scales confer resilience to the woodland system. Most of this complexity has been lost in the current agricultural system, and it can be hypothesised that many current degradation problems can be related to this. The challenge for the future is to develop complexity and resilience in agricultural systems while maintaining an acceptable level of production.