School of Ecosystem and Forest Sciences - Research Publications
Now showing items 1-12 of 371
Using local knowledge to identify drivers of historic native vegetation change
(Modelling and Simulation Society of Australia and New Zealand Inc, 2009-07-17)
Research underway with three Catchment Management Authorities in Victoria (Goulburn Broken, North Central and North East) is examining the impacts these bodies have had, and could potentially have, on native vegetation extent and quality (condition) on private land. This paper outlines how local knowledge together with spatial data and ecological information is being used to develop Bayesian Networks (BNs) that show historic changes in native vegetation quality and extent in three regions of northern Victoria since the 1880's. The research is being focused on three case study areas, one located in each partner CMA (Figure 1). Comparison of aerial photography from 1946/7 with contemporary modelled tree canopy cover identified that native vegetation extent has increased or decreased to varying degrees over time and space in each case study areas. Local knowledge elicited from the regional workshops has identified the catalysts of change over time as including episodic events, the viability of the farming industry, demand for 'lifestyle' properties, rabbit control, NRM and Landcare initiatives and policy instruments. Changes in extent and quality of native vegetation varied spatially and temporally across the landscape depending on the presence of remnant native vegetation, land tenure, agronomic potential of the land, historic events (e.g. bushfires), characteristics of the local population and targeted policy instruments. Expansion and intensification of farming between the mid-1950s and the late 1970s was matched by a general decline in the extent of woody native vegetation on private land. A decline in farm profitability from the 1980s to 2006 was associated with declines in farm employment, the number of farmers, population, and businesses and services in small rural towns dependent on agriculture and increases in 'lifestyle' farming around rural towns and regional centres. A general increase in the extent of woody native vegetation on private land was noted over this period by workshop participants. BNs are being used to integrate local knowledge on historic land cover and vegetation change, and its drivers, with analysis of spatial data to capture changes in condition over time (60+ years). The regional workshops have been crucial in developing conceptual understanding of the relationships between external drivers (e.g. climate, market forces), actions (e.g. land clearing, de-stocking, revegetation) and outcomes (e.g. vegetation change). The knowledge and understanding of changes in land use and management and their drivers that was gained from the workshops have been used to refine the influence diagram for the historic vegetation extent and quality BNs, define the details of each variable (e.g. states, key assumptions) and identify key decades to represent in the models.
Misinformation, internet honey trading and beekeepers drive a plant invasion
Biological invasions are a major human induced global change that is threatening global biodiver-sity by homogenizing the world’s fauna and ﬂora. Species spread because humans have movedspecies across geographical boundaries and have changed ecological factors that structure ecosys-tems, such as nitrogen deposition, disturbance, etc. Many biological invasions are caused acciden-tally, as a byproduct of human travel and commerce driven product shipping. However, humansalso have spread many species intentionally because of perceived beneﬁts. Of interest is the role ofthe recent exponential growth in information exchange via internet social media in driving biologi-cal invasions. To date, this has not been examined. Here, we show that for one such invasive spe-cies, goldenrod, social networks spread misleading and incomplete information that is enhancingthe spread of goldenrod invasions into new environments. We show that the notion of goldenrodhoney as a “superfood” with unsupported healing properties is driving a demand that leads bee-keepers to produce goldenrod honey. Social networks provide a forum for such informationexchange and this is leading to further spread of goldenrod in many countries where goldenrod isnot native, such as Poland. However, this informal social information exchange ignores laws thatfocus on preventing the further spread of invasive species and the strong negative effects thatgoldenrod has on native ecosystems, including ﬂoral resources that negatively impact honeybeeperformance. Thus, scientiﬁcally unsupported information on “superfoods” such as goldenrodhoney that is disseminated through social internet networks has real world consequences such asincreased goldenrod invasions into novel geographical regions which decreases native biodiversity.
Disentangling chronic regeneration failure in endangered woodland ecosystems
(Ecological Society of America, 2020-01)
Ecological restoration of degraded ecosystems requires the facilitation of natural regeneration by plants, often augmented by large-scale active revegetation. The success of such projects is highly variable. Risk factors may be readily identifiable in a general sense, but it is rarely clear how they play out individually, or in combination. We addressed this problem with a field experiment on the survival of, and browsing damage to, 1275 hand-planted buloke (Allocasuarina luehmannii) seedlings in a nationally endangered, semi-arid woodland community. Buloke seedlings were planted in 17 sites representing four landscape contexts and with three levels of protection from kangaroo and lagomorph browsing. We censused seedlings and measured herbivore activity four times during the first 400 days post-planting, and fitted models of mortality and browse hazard to these data using survival analysis. Increasing lagomorph activity was associated with higher mortality risk, while kangaroo activity was not. Seedling survival was lowest for each treatment within extant buloke woodland, and the highest survival rates for guarded seedlings were in locations favoured by lagomorphs. Damage from browsing was nearly ubiquitous after one year for surviving unguarded seedlings, despite moderate browser activity. On average, unguarded seedlings showed a decline in height, whereas fully guarded seedlings grew 2.3 cm across the survey period. This study demonstrates buloke seedlings should be protected from browsers, even with browsers maintained at moderate to low density, and the location that maximizes survival, and possibly growth rates, is adjacent to dunes. Further work will test this heuristic in an analysis of cost-effective revegetation strategies for this endangered community.
Environmental drivers of femaleness of an inter-Andean monoecious shrub
Hetero‐and conspecific interactions, nutrient availability, climate, habitat heterogeneity, and disturbances can generate variation and spatial patterns of femaleness in plants. We assessed whether year, site, plant size, plant density, and canopy area of conspecific neighbors influenced the expression and spatial aggregation of femaleness in Croton aff. wagneri, a monoecious shrub from dry shrublands of the inter‐Andean valleys in Ecuador. We georeferenced in two sites (1,700 and 1,400 m.a.s.l) in five 10 × 10 m plots, within each site, the position of each Croton reproductive plant during first part of flowering season in two years, and measured their height, length, and width. The femaleness index of each plant was determined by the number of female and male buds and flowers. Plant density was determined for each plot, along with the number of neighbors and the summed canopy area of conspecific neighbors (at 1.0, 2.0, and 2.5 m radius, and the five closest plants) from each focal plant. Croton´s femaleness at the lower elevation site was greater than at the higher elevation site and increased with plant size and with canopy of the closest five neighbors. Soil at the lower elevation site had higher temperatures and lower water content. Aggregate patterns of femaleness were found in more plots at the lower elevation site. Our results indicate that location, plant size, and canopies of conspecific neighbors of Croton can affect femaleness and its aggregation and support the hypothesis that femaleness can be influenced by facilitative interactions.
Beyond the blame game: a restoration pathway reconciles ecologists' and local leaders' divergent models of seasonally dry tropical forest degradation
(RESILIENCE ALLIANCE, 2019-12-01)
An understanding of ecosystem dynamics under different scenarios of degradation is required to reverse ecological degradation and identify restoration priorities. Such knowledge can be the result of scientific investigation, but important insight can also reside in observant local land managers. In seasonally dry tropical forests in southern Ecuador, recent decades have seen important advances in the knowledge of the biodiversity values of these forests, but the available data have not yet been integrated and translated into tools that support managers in deciding restoration measures. One powerful framework to organize and communicate information about ecosystem degradation and recovery dynamics is the state-transition model. We generated such a model by combining ecologist and local knowledge obtained through an adaptation of the Stanford/SRI expert elicitation protocol. Through this information, we identified five forest states with specific attributes of vegetation, human pressures, and restoration needs. Ecologists and locals agreed on the restoration actions but partially disagreed on the causes of degradation. Whereas ecologists considered that grazing management, often introduced with or after logging, was the catalyst for a transition to degraded states, locals attributed those transitions to the effects of logging alone. Importantly, however, both ecologists and locals considered that exclusion of livestock grazing was a necessary action to promote ecological recovery. A forward-looking strategy focusing on objectives for ecosystem recovery and ecosystem management for biodiversity and human well-being might be more successful than strategies that emphasize or seek to attribute responsibility for degradation.
Towards open, reliable, and transparent ecology and evolutionary biology
Unreliable research programmes waste funds, time, and even the lives of the organisms we seek to help and understand. Reducing this waste and increasing the value of scientific evidence require changing the actions of both individual researchers and the institutions they depend on for employment and promotion. While ecologists and evolutionary biologists have somewhat improved research transparency over the past decade (e.g. more data sharing), major obstacles remain. In this commentary, we lift our gaze to the horizon to imagine how researchers and institutions can clear the path towards more credible and effective research programmes.
Indigenous plants promote insect biodiversity in urban greenspaces
The contribution of urban greenspaces to support biodiversity and provide benefits for people is increasingly recognized. However, ongoing management practices favor vegetation oversimplification, often limiting greenspaces to lawns and tree canopy rather than multi-layered vegetation that includes under- and midstorey, and the use of nonnative species. These practices hinder the potential of greenspaces to sustain indigenous biodiversity, particularly for taxa like insects that rely on plants for food and habitat. Yet, little is known about which plant species may maximize positive outcomes for taxonomically and functionally diverse insect communities in greenspaces. Additionally, while cities are expected to experience high rates of introductions, quantitative assessments of the relative occupancy of indigenous vs. introduced insect species in greenspace are rare, hindering understanding of how management may promote indigenous biodiversity while limiting the establishment of introduced insects. Using a hierarchically replicated study design across 15 public parks, we recorded occurrence data from 552 insect species on 133 plant species, differing in planting design element (lawn, midstorey, and tree canopy), midstorey growth form (forbs, lilioids, graminoids, and shrubs) and origin (nonnative, native, and indigenous), to assess (1) the relative contributions of indigenous and introduced insect species and (2) which plant species sustained the highest number of indigenous insects. We found that the insect community was overwhelmingly composed of indigenous rather than introduced species. Our findings further highlight the core role of multi-layered vegetation in sustaining high insect biodiversity in urban areas, with indigenous midstorey and canopy representing key elements to maintain rich and functionally diverse indigenous insect communities. Intriguingly, graminoids supported the highest indigenous insect richness across all studied growth forms by plant origin groups. Our work highlights the opportunity presented by indigenous understory and midstorey plants, particularly indigenous graminoids, in our study area to promote indigenous insect biodiversity in urban greenspaces. Our study provides a blueprint and stimulus for architects, engineers, developers, designers, and planners to incorporate into their practice plant species palettes that foster a larger presence of indigenous over regionally native or nonnative plant species, while incorporating a broader mixture of midstorey growth forms.
Levee System Reliability Modeling: The Length Effect and Bayesian Updating
<jats:p>In levee system reliability, the length effect is the term given to the phenomenon that the longer the levee, the higher the probability that it will have a weak spot and fail. Quantitatively, it is the ratio of the segment failure probability to the cross-sectional failure probability. The literature is lacking in methods to calculate the length effect in levees, and often over-simplified methods are used. An efficient (but approximate) method, which we refer to as the modified outcrossing (MO) method, was developed for the system reliability model used in Dutch national flood risk analysis and for the provision of levee assessment tools, but it is poorly documented and its accuracy has not been tested. In this paper, we propose a method to calculate the length effect in levees by sampling the joint spatial distribution of the resistance variables using a copula approach, and represented by a Bayesian Network (BN). We use the BN to verify the MO method, which is also described in detail in this paper. We describe how both methods can be used to update failure probabilities of (long) levees using survival observations (i.e., high water levels and no levee failure), which is important because we have such observations in abundance. We compared the methods via a numerical example, and found that the agreement between the segment failure probability estimates was nearly perfect in the prior case, and very good in the posterior case, for segments ranging from 500 m to 6000 m in length. These results provide a strong verification of both methods, either of which provide an attractive alternative to the more simplified approaches often encountered in the literature and in practice.</jats:p>
Leaf Traits of Drought Tolerance for 37 Shrub Species Originating from a Moisture Gradient
<jats:p>Identifying the drought-tolerance traits of plant species originating from a moisture gradient will increase our understanding of the differences and similarities in plant drought tolerance. However, which traits can be used to evaluate drought tolerance remain an open question. Here, we conducted a common-garden experiment on 37 shrub species originating from desert to humid regions. The correlations between plant traits and the native environmental conditions were studied. Leaf sizes and Huber values were significantly correlated with most climate variables of the shrubs’ origins. The osmotic potentials at full turgor (π100), turgor loss point (ΨTLP), and midday leaf water potential (Ψmid) were significantly correlated with most climate variables of their origins. We proposed using leaf sizes, Huber values, and ΨTLP as predictors of drought tolerance across shrub species and shrub biomes. Statistically significant correlations were found between π100, ΨTLP, and specific leaf area (SLA). However, owing to the weak correlations between SLA and the climate variables of the shrubs origins and between Huber values and leaf size and turgor loss traits, it was difficult to integrate leaf morphological traits with physiological traits to find a simple way to accurately quantify drought-tolerance-related differences among these shrub species.</jats:p>
Clean and Green Urban Water Bodies Benefit Nocturnal Flying Insects and Their Predators, Insectivorous Bats
<jats:p>Nocturnal arthropods form the prey base for many predators and are an integral part of complex food webs. However, there is limited understanding of the mechanisms influencing invertebrates at urban water bodies and the potential flow-on effects to their predators. This study aims to: (i) understand the importance of standing water bodies for nocturnal flying insect orders, including the landscape- and local-scale factors driving these patterns; and (ii) quantify the relationship between insects and insectivorous bats. We investigated nocturnal flying insects and insectivorous bats simultaneously at water bodies (n = 58) and non-water body sites (n = 35) using light traps and acoustic recorders in Melbourne, Australia. At the landscape scale, we found that the presence of water and high levels of surrounding greenness were important predictors for some insect orders. At the water body scale, low levels of sediment pollutants, increased riparian tree cover and water body size supported higher insect order richness and a greater abundance of Coleopterans and Trichopterans, respectively. Most bat species had a positive response to a high abundance of Lepidopterans, confirming the importance of this order in the diet of insectivorous bats. Fostering communities of nocturnal insects in urban environments can provide opportunities for enhancing the prey base of urban nocturnal insectivores.</jats:p>
Urban Green Space Distribution Related to Land Values in Fast-Growing Megacities, Mumbai and Jakarta-Unexploited Opportunities to Increase Access to Greenery for the Poor
<jats:p>Many studies on disparities in the distribution of urban green space (UGS) focus on the quantity and accessibility of designated open spaces. However, when all types of UGS, including unmanaged green areas, are accounted for, claims of green space distributive injustice become more complicated. We conducted a preliminary investigation questioning the common Global North assumption that the poor have less access to the benefits of green space, using the cities of Mumbai and Jakarta as case studies as, in their respective countries, wealth inequality has grown at a higher rate than in other Asian countries. We employed four sets of geospatial data to analyze green space distribution patterns and probe the relationship with UGS inequity in different land value districts. We found that the lower land value districts had more vegetation coverage with a higher vegetation density, mainly due to a large quantity of unmanaged greenery. The relationship between the status of urban development and the land values in a district is not necessarily reflective of the UGS distribution once unmanaged vegetation is considered. We conclude by discussing ways to optimize the use of unmanaged UGS as a socioecological asset for poorer districts, and we point to the practical consequences of incorporating the study’s findings into policy and planning towards the creation of ecologically inclusive cities.</jats:p>