Stephen Livesley | University of Melbourne (original) (raw)

Papers by Stephen Livesley

Trees play an important role in urban areas by improving air quality, mitigating urban heat islan... more Trees play an important role in urban areas by improving air quality, mitigating urban heat islands, reducing stormwater runoff and providing biodiversity habitat. Accurate and up-to-date estimation of urban tree canopy cover (UTC) is a basic need for the management of green spaces in cities, providing a metric from which variation can be understood, change monitored and areas prioritised. Random point sampling methods, such as i-Tree canopy, provide a cheap and quick estimation of UTC for a large area. Remote sensing methods using airborne Light Detection And Ranging (LiDAR) and multi-spectral images produce accurate UTC maps, although greater processing time and technical skills are required. In this paper, random point sampling and remote sensing methods are used to estimate UTC in Williamstown, a suburb of Melbourne, Australia. High resolution multi-spectral satellite images fused with LiDAR data with pixel-level accuracy are employed to produce the UTC map. The UTC is also estimated by categorising random points (a) automatically using the LiDAR derived UTC map and (b) manually using Google Maps and i-Tree canopy software. There was a minimum 1% difference between UTC estimated from the map derived from remotely sensed data and only 1000 random points automatically categorised by that same map, indicating the level of error associated with a random sampling approach. The difference between UTC estimated by remote sensing and manually categorised random point sampling varied in range of 4.5% using a confidence level of 95%. As monitoring of urban forest canopy becomes an increasing priority, the uncertainties associated with different UTC estimates should be considered when tracking change or comparing different areas using different methods.

Agricultural and Forest Meteorology, 2015

Climate change may have major implications on soil respiration dynamics and the carbon sink stren... more Climate change may have major implications on soil respiration dynamics and the carbon sink strength of forest soils. To assess the effect of climate change on soil respiration (RS), it is crucial to understand individual responses of autotrophic (RA) and heterotrophic (RH) components. We investigated the effect of continuously (20 months) reduced throughfall (TFR, −40%) and the influence of seasonal changes in soil temperature and moisture on RS, RA and RH, partitioned by root exclusion, in a dry temperate broadleaved evergreen eucalypt forest in south-eastern Australia. TFR decreased mean RS from 4.7 ± 0.1 (Control) to 3.8 ± 0.1 (TFR) mol CO 2 m −2 s −1 (−19%). TFR indicated a strong decrease in RA from 2.5 ± 0.1 (Control) to 1.5 ± 0.1 (TFR) mol CO 2 m −2 s −1 (−40%), but had no effect on RH. The mean relative contribution of RH to RS was 47% in the Control and increased to 61% under TFR. RS was the result of distinct seasonal patterns and dependencies of RH and RA on environmental variables. Soil temperature was a good predictor of RH (Control: R 2 = 0.72, TFR: R 2 = 0.75), but not of RA. In contrast, RH was not limited by soil moisture, while RA was partly influenced by soil moisture (Control: R 2 = 0.29, TFR: R 2 = 0.56). The lack of response of RH to changes in soil moisture (seasonal and under TFR) was likely influenced by the high rainfall conditions such that soil moisture did not decrease to a point where it limited soil microbial decomposition processes. Our results show that TFR implied the strongest effect on RA and that changes in soil temperature and moisture alone do not sufficiently explain seasonal changes in RA and RS. This indicates that biotic factors, such as plant internal carbon allocation, may exert a stronger influence on RA and hence, RS. In short-term a reduction in rainfall will lead to a decrease of soil respiration in dry temperate broadleaved evergreen eucalypt forests. The magnitude of this decrease and its persistence under extended drought will be greatly influenced by seasonal and inter-annual climate variability and potential changes in plant carbon allocation.

Urban Forestry & Urban Greening

Drought can lead to mortality in urban tree populations. The City of Melbourne, Victoria, Austral... more Drought can lead to mortality in urban tree populations. The City of Melbourne, Victoria, Australia, manages a large population of trees that provide important ecosystem services and cultural heritage values. Between 1997 and 2009 Melbourne was affected by a serious drought resulting in signi cant tree health decline. Elms and planes in particular, were badly affected. This paper presents data from a survey of tree health status, and of studies of retro tted buried drip line irrigation. A study of soil wetting in autumn of 2009 found that the use of drip irrigation had, in most cases, little or no effect on soil moisture levels and a modeled study of tree water use showed that water delivered by drip irrigation provided only a fraction of the water required by a mature tree. By contrast, drip irrigation in late winter was able to recharge soil moisture levels. Mechanisms responsible for the decline in tree health seen during the drought are discussed. While the drought has temporarily been alleviated, climate change scenarios for southern Australia suggest that increased rainfall variability and drought events will be more common. The experiences gained during the recent drought event provide useful information for urban tree managers planning for the future.

Urban landscapes show high heterogeneity at a variety of scales. Numerous studies have investigat... more Urban landscapes show high heterogeneity at a variety of scales. Numerous studies have investigated the effects of urban landscape composition on ecological processes and services at large scales (city, watershed, neighbourhood). However, soil processes vary greatly at much finer scales. Moreover, current evaluations of hydrological processes in urban landscapes are rarely based on field measurements. Thus, measuring fine-scale variation in soil processes may provide useful information in scaling-up processes and services to larger urban landscapes. This study aims to assess how the fine-scale heterogeneity of urban landscapes impacts upon soil hydrological processes and subsequently the ecosystem services that urban soil provides. In particular we asked: i) does fine-scale heterogeneity of urban landscapes alter soil hydrological processes and services? ii) what are the implications in scaling-up processes and services at larger scales? We selected five anthropogenic urban landscap...

The simplification of the structure of urban ecosystems compared to natural systems is a common t... more The simplification of the structure of urban ecosystems compared to natural systems is a common trait worldwide. Like the homogenization of urban ecosystems, the simplification of urban ecosystems is likely to be driven by socio-economical factors and management practices. While many studies have investigated how the simplification of urban ecosystems impacts above-ground biodiversity and processes, few have investigated below-ground effects. This study aims to understand the effect that simplifying urban ecosystems structure has upon soil biogeochemical processes, namely leaf litter decomposition and soil carbon sequestration, and soil organisms potentially involved in these processes. We posed the following research questions: i) is the simplification of the structure of urban ecosystems affecting soil processes? ii) how does the simplification of the structure affect the microclimate of the surface decomposition environment? and iii) does the variation in soil biogeochemical proc...

Climate change and fire influence the methane uptake capacity in Australian eucalypt forest soils... more Climate change and fire influence the methane uptake capacity in Australian eucalypt forest soils Soil methane (CH4) oxidation in forest ecosystems comprise the largest soil sink for this potent greenhouse gas and climate change as well as fire can have significant impacts on this important process. We present data from a number of long-term greenhouse gas studies that investigated the potential impacts of reduced rainfall and altered fire regimes on CH4 flux in Australian eucalypt forest systems. Long term CH4 flux measurements with high temporal resolution in a dry-sclerophyll and wet-sclerophyll eucalypt forests contrasting in annual precipitation (870 and 1700mm year-1) showed that 90% of soil CH4 uptake variability is explained by soil moisture. The application of throughfall reduction shelters that intercepted 40% of throughfall caused an average reduction of 14.6% in soil volumetric water content but an increase in soil CH4 uptake of 38%. Consequently, the predicted climate c...

Urban ecosystems are frequently characterized by simplified structures compared to the surroundin... more Urban ecosystems are frequently characterized by simplified structures compared to the surrounding natural ecosystems, which in turn control microclimate, habitat and resources for soil organisms and consequently soil processes depending upon them. While various studies have investigated leaf litter decomposition processes in forest remnants along urban-rural gradients and pollution gradients, few have investigated these in simplified urban ecosystems such as urban parks and gardens. We investigated the effects of contrasting urban ecosystem structural complexities on litter decomposition and assessed to what extent the differential contribution of decomposers groups (macro/meso/micro) and the microclimate explained the observed patterns. Research plots (n=30) were established on the Melbourne’s sandbelt, and low-complexity parks (LCPs), high-complexity parks (HCPs) and high-complexity remnants (HCRs) were selected. After a year in-situ decomposition experiment, the combined activit...

Global change biology, Jan 18, 2015

Disturbance associated with severe wildfires and wildfire simulating harvest operations can poten... more Disturbance associated with severe wildfires and wildfire simulating harvest operations can potentially alter soil methane (CH4 ) oxidation in well aerated forest soils due to the effect on soil properties linked to diffusivity, methanotrophic activity or changes in methanotrophic bacterial community structure. However, changes in soil CH4 flux related to such disturbances are still rarely studied even though wildfire frequency is predicted to increase as a consequence of global climate change. We measured in situ soil atmosphere CH4 exchange along a wet sclerophyll eucalypt forest regeneration chronosequence in Tasmania, Australia, where the time since the last severe fire or harvesting disturbance ranged from 9 to >200 years. On all sampling occasions mean CH4 uptake increased from most recently disturbed sites (9 year) to sites at stand 'maturity' (44 and 76 years). In stands >76 years since disturbance we observed a decrease in soil CH4 uptake. A similar age depend...

Tree physiology, 2015

Seasonally dry ecosystems present a challenge to plants to maintain water relations. While native... more Seasonally dry ecosystems present a challenge to plants to maintain water relations. While native vegetation in seasonally dry ecosystems have evolved specific adaptations to the long dry season, there are risks to introduced exotic species. African mahogany, Khaya senegalensis Desr. (A. Juss.), is an exotic plantation species that has been introduced widely in Asia and northern Australia, but it is unknown if it has the physiological or phenotypic plasticity to cope with the strongly seasonal patterns of water availability in the tropical savanna climate of northern Australia. We investigated the gas exchange and water relations traits and adjustments to seasonal drought in K. senegalensis and native eucalypts (Eucalyptus tetrodonta F. Muell. and Corymbia latifolia F. Muell.) in a savanna ecosystem in northern Australia. The native eucalypts did not exhibit any signs of drought stress after 3 months of no rainfall and probably had access to deeper soil moisture late into the dry se...

Theoretical and Applied Climatology, 2015

Urban street trees provide

Journal of environmental management, Jan 15, 2015

Biosolids produced by wastewater treatment plants are often stored in stockpiles and can be a sig... more Biosolids produced by wastewater treatment plants are often stored in stockpiles and can be a significant source of greenhouse gases (GHG). Growing trees in shallow stockpiled biosolids may remove nutrients, keep the biosolids drier and offset GHG emissions through C sequestration. We directly measured methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) flux from a large biosolid stockpile and two shallow stockpiles, one planted with Salix reichardtii (willow) trees, from December 2009 to January 2011. All stockpiles emitted large annual amounts of GHG ranging from 38 kg CO2-e Mg(-1) dry biosolid for the large stockpile, to 65 kg CO2-e Mg(-1) for the unplanted shallow stockpile, probably due to the greater surface area to volume ratio. GHG emissions were dominated by N2O and CO2 whilst CH4 emissions were negligible (<2%) from the large stockpile and the shallow stockpiles were actually a CH4 sink. Annual willow tree growth was 12 Mg dry biomass ha(-1), but this only offse...