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Archive for the ‘Landscapes’ Category
Sunday, November 9th, 2008
The main reason I haven’t blogged much recently is because all my spare time has been taken up working on revisions to a paper submitted to Environmental Modelling and Software. Provisionally entitled ‘Modelling Mediterranean Landscape Succession-Disturbance Dynamics: A Landscape Fire-Succession Model’, the paper describes the biophysical component of the coupled human-natural systems model I started developing during my PhD studies. This biophysical component is a vegetation state-and-transition model combined with a cellular-automata to represent wildfire ignition and spread.
The reviewers of the paper wanted to see some changes to the seed dispersal mechanism in the model. Greene et al. compared three commonly used empirical seed dispersal functions and concluded that the log-normal distribution is generally the most suitable approximation to observed seed dispersal curves. However, dispersal functions using an exponential function have also been used. A good example is the LANDIS forest landscape simulation model that calculates the probability of seed fall (P) in a region between the effective (ED) and maximum (MD) seed distance from the seed source. For distances from the seed source (x) < ED, P = 0.95. For x > MD, P = 0.001. For all other distances P is calculated using the negative exponential distribution function is used as follows:
where b is a shape parameter.
Recently Syphard et al. modified LANDIS for use in the Mediterranean Type Environment of California. The two predominant pine species in our study area in the Mediterran Basin have different seed types: one (Pinus pinaster) has has wings and can fly large distances (~1km), but the other (Pinus pinea) does not. In this case a negative exponential distribution is most appropriate. However, research on the dispersal of acorns (from Quercus ilex) found that the distance distribution of acorns was best modeled by a log-normal distribution. I am currently experimenting with these two alternative seed dispersal distributions and comparing them with spatially random seed dispersal (dependent upon quantity but not locations of seed sources).
The main thing that has kept me occupied the last couple of weeks has been the implementation of these approaches in a manner that is computationally feasible. I need to run and test my model over several hundred (annual) timesteps for a landscape grid of data ~1,000,000 pixels. Keeping computation time down so that model execution does not take hundreds of hours is clearly important if sufficient model executions are to be run to ensure some form of statistical testing is possible. A brute-force iteration method was clearly not the best approach.
One of my co-authors suggested I look into the use of Quadtrees. Quadtrees are a tree data structure that are often used to partition a two dimensional space by recursively subdividing regions into quadrants (nodes). A region Quadtree partitions a region of interest into four equal quadrants. Each of these quadrants is subdivided into four subquadrants, each of which is subdivided and so on to the finest level of spatial resolution required. The University of Maryland have a nice Java applet example that helps illustrate the concept.
For our seed dispersal purposes, a region quadtree with n levels of may be used to represent an landscape of 2n × 2n pixels, where each pixel is assigned a value of 0 or 1 depending upon whether it contains a seed source of the given type or not. The distance of all landscape pixels to a seed source can then be quickly calculated using this data structure – staring at the top level we work our way down the tree querying whether each quadrant contains a pixel(s) that is a seed source. In this way, large areas of the grid can be discounted as not containing a seed source, thereby speeding the distance calculation.
Now that I have my QuadTree structure in place model execution time is much reduced and a reasonable number of model executions should be possible over the next month or so of model testing, calibration and use. My next steps are concerned with pinning down the appropriate values for ED and MD in the seed dispersal functions. This process of parameterization will take into account values previously used by similar models in similar situations (e.g. Syphard et al.) and empirical research and data on species found within our study area (e.g. Pons and Pausas). The key thing to keep in mind with these latter studies is their focus on the distribution of individual seeds from individual trees – the spatial resolution of my model is 30m (i.e. each pixel is 30m square). Some translation of values for individuals versus aggregated representation of individuals (in pixels) will likely be required. Hopefully, you’ll see the results in print early next year.
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Computing, Ecological, Landscapes, Modelling, MyPhD, Wildfire | Comments Off
Wednesday, August 20th, 2008
The provisional conference programme for the Annual Conference of the UK Regional Association of the International Association for Landscape Ecology (IALE-UK) has been published. The conference will take place between 8th – 11th September 2008 at Cambridge University with sessions to include:
- Conservation in Farmed Landscapes
- Dispersal in Fragmented Landscapes
- Culture and Landscapes
- Distribution and Fragmented Landscapes
- Theory Into Practice: Landscape Ecology Being Used to Conserve Habitats and Species
As with all IALE conferences there will be a field trip that attendees can join. This year the IALE-UK trip will visit the Great Fen Project and Wicken Fen, part of the largest wetland restoration in Europe.
The conference programme is now full, but there are still opportunities to submit posters. Registration to attend also remains open. For submissions and registrations, contact Pete Carey, and for more information visit the conference webpage.
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Landscapes | Comments Off
Thursday, August 14th, 2008
Earlier this week I submitted a manuscript to Earth Surface Processes and Landforms with one of my former PhD advisors, John Wainwright. Provisionally entitled Mind, the Gap in Landscape-Evolution Modelling (we’ll see what the reviewers think of that one!), the manuscript argues that agent-based models (ABMs) are a useful tool for overcoming the limitations of existing, highly empirical approaches in geomorphology. This, we suggest, would be useful because despite an increasing recognition that human activity is currently the dominant force modifying landscapes geomorphically, and that this activity has been increasing through time, there has been little integrative work to evaluate human interactions with geomorphic processes.
In the manuscript we present two case studies of models that consider landscape change with the aid of an ABM – SPASIMv1 (developed during my PhD) and CybErosion (a model to simulate the dynamic interaction of prehistoric communities in Mediterranean environments John has developed). We evaluate the advantages and disadvantages of the ABM approach, and consider some of the major challenges to implementation. These challenges include potential process scale mis-matches, differences in perspective between investigators from different disciplines, and issues regarding model evaluation, analysis and interpretation.
I’ll post more here as the review process progresses. Hopefully progress with ESPL will be a little quicker than it has been for the manuscript I submitted to Environmental Modelling and Software detailing the biophysical component of SPASIMv1 (still yet to receive the review after 5 months!)…
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Landscapes, Modelling, Publications | Comments Off
Friday, August 8th, 2008
I like climbing tall things in cities and then looking down to watch the human ants going about their business. Maybe my interest in experimenting with spatial agent-based models is related to this fascination.
The BBC have taken these ideas, of looking down from on high and exploring the dynamic interplay of human activity across space, and produced some incredible movies for a new show. Checkout some of the footage below – looks awesome.
[youtube=http://www.youtube.com/watch?v=LV6l8AvjtqE&color1=11645361&color2=13619151&hl=en&fs=1]
If you’re in the UK, the new series Britain From Above starts at 9pm on Sunday 10th August, BBC One.
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Fun, Landscapes | Comments Off
Thursday, July 31st, 2008
Coupling Humans and Complex Ecological Landscapes is the theme of the 2009 annual conference of US-IALE (U.S. Regional Association, International Association for Landscape Ecology). The conference will be held in Snowbird, Utah, from April 12-16, 2009. Proposals for symposia and workshops are due September 15, 2008; and abstracts are due November 17, 2008.
Several types of financial support for attending and presenting at the conference are available:
(1) the “Sponsored Student Travel Awards Program” of local sponsors (USGS, Utah State University, and Utah Department of Natural Resources),
(2) US-IALE’s ‘Foreign Scholar Travel Award‘ Program,
(3) the ‘NASA-MSU Professional Enhancement Awards Program‘ (supported by NASA and Michigan State University), and
(4) the ‘CHANS Fellows Program’ of the new International Network of Research on Coupled Human and Natural Systems (CHANS-Net, supported by NSF, see background papers in Science and Ambio).
US-IALE conferences are particularly students-friendly, with two popular programs — Lunch with Mentors and NASA-MSU dinner, and a new program — We’ll “Pick Up The Tab!”.
More information about the conference is available from the web site.
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, CHANS, Ecological, Landscapes, Social | Comments Off
Tuesday, July 15th, 2008
In many forest landscapes a desirable management objective is the sustainability of both economic productivity and healthy wildlife populations. Such dual-objective management requires a good understanding of the interactions between the many components and actors at several scales and across large extents. Computer simulation models have been enthusiastically developed by scientists to improve knowledge about the dynamics of forest growth and disturbance (for example by timber harvest or wildfire).
However, Papaik, Sturtevant and Messier write in their recent guest editorial for Ecology and Society that “models are constrained by persistent boundaries between scientific disciplines, and by the scale-specific processes for which they were created”. Consequently, they suggest that:
“A more integrated and flexible modeling framework is required, one that guides the selection of which processes to model, defines the scales at which they are relevant, and carefully integrates them into a cohesive whole”.
This new framework is illustrated by the papers in the Ecology and Society special feature ‘Crossing Scales and Disciplines to Achieve Forest Sustainability: A Framework for Effective Integrated Modeling’.
The papers in the special feature provide case studies that reflect two interacting themes:
- interdisciplinary approaches for sustainable forest landscape management, and
- the importance of scaling issues when integrating socioeconomic and ecological processes in the modeling of managed forest ecosystems.
These issues are well related to the project I’m currently working on that is developing an integrated ecological-economic model of a managed forest landscape in Michigan’s Upper Peninsula. One paper that caught my eye was by Sturtevant et al., entitled ‘A Toolkit Modeling Approach for Sustainable Forest Management Planning: Achieving Balance between Science and Local Needs’.
Sturtevant et al. suggest that forest managers are generally faced with a “devil’s choice” between using generic ‘off-the-shelf models’ where information flows primarily from researchers and planners down to local communities versus developing case-specific models designed for a specific purpose or locale and based on information from the local actors. To avoid this choice, which Sturtevant et al. believe will seldom result in a satisfactory management result, they outline their proposal for a hybrid ‘toolkit’ approach. Their alternative approach “builds on existing and readily adaptable modeling ‘tools’ that have been developed and applied to previous research and planning initiatives”.
Their toolkit approach is
- collaborative – including stakeholders and decision-makers
- a ‘meta-modelling’ approach – the model is derived from other models and tools.
They then illustrate their toolkit approach using a case study from Labrador, Canada, highlighting the stages of establishing the issues, developing a conceptual model, implementing the meta-model, and then refining the model iteratively. They conclude:
“A toolkit approach to SFM [Sustainable Forest Management] analytical support is more about perspectives on information flow than on technical details. Certainly expertise and enabling technology are required to allow a team to apply such a framework. However, the essence of this approach is to seek balance between top-down (off the shelf, science-driven) and bottom-up (case-specific, stakeholder-driven) approaches to SFM decision support. We aim to find a pivot point, with adequate information flow from local experts and stakeholders to scientists, while at the same time avoiding “reinventing the wheel” (e.g. Fig. 1) by making full use of the cumulative experience of scientists and tools they have constructed.”
Although this ‘meta-model’ approach may save time on the technical model building side of things, many resources (time, effort and money) will be required to build and maintain relationships and confidence between scientists, managers and local stakeholders. This approach is really a modelling toolkit for management, with very little emphasis on improving scientific understanding. In this case the modelling is the means to the end of integrative/participatory management of the forest landscape.
The authors continue:
“The mixture of local experts and stakeholders who understand how the tools work, scientists who are willing and able to communicate their science to stakeholders, and integrated analytical tools that can simulate complex spatial and temporal problems will provide powerful and efficient decision support for SFM.”
Unfortunately, unless the scientists in question have the explicit remit to offer their services for management purposes, this sort of modelling approach will not be very appealing to them. In a scientific climate of ‘publish or perish’, management outcomes alone are unlikely to be enough to lure the services of scientists. In some cases I’m sure I will be wrong and scientists will happily oblige. But more generally, unless funding bodies become less concerned with tangible outputs at specific points in time, and academic scientists are judged less strictly by their publishing output, this situation may be difficult to overcome.
This situation is one reason the two sides of the “devils’ choice” are more well developed to the expense of the ‘middle-ground’ toolkit approach. ‘Off-the-shelf’ models, such as LANDIS, are appealing to scientists as they allow the investigation of more abstract and basic science questions than asked by forest managers. The development of ‘customized’ models is appealing to scientists because they allow more detailed investigation of underlying processes and provide a framework for the collection of empirical data collection. No doubt the understanding gained from these approaches will eventually help forest managers – but not in the manner of direct decision-support as the toolkit modelling approach proposes.
As a case in point, the ‘customized’ Managed Forest Landscape Model for Michigan I am working on is raising questions about underlying relationships between deer and forest stand structure. I’m off into the field this week to get data collection started for just that purpose.
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Landscapes, MichiganUP, Modelling, Sustainability | Comments Off
Wednesday, May 21st, 2008
    Columbia University Press currently has a sale on. They have savings of up to 80% on more than 1,000 titles from several fields of study. I was particularly interested in their books in the Environmental Studies and Ecology section and purchased several:
Previously on this blog I reviewed another book they have on sale, Useless Arithmetic: Why Environmental Scientists Can’t Predict the Future by Orrin H. Pilkey and Linda Pilkey-Jarvis.
When I get round to reading this new batch I’ll review some of these also (at first glance the Wiens et al. book looks particularly useful for any Landscape Ecologist – student, teacher or researcher). You’ve got up until May 31st to order yours.
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Ecological, Economic, Landscapes, Miscellaneous, Web | Comments Off
Friday, May 16th, 2008
I’ve been back from our study area in Michigan’s Upper Peninsula for over a week so it’s about time I posted something about what we were doing up there.
One of the main issues we will study with our integrated ecological-economic landscape model is the impact of whitetail deer (Odocoileus virginianus) herbivory on tree regeneration following cutting. Last November we spent a week planting 2 year-old seedlings in Northern Hardwood forest gaps created by selective timber harvest (like the one in the photo below).
Our plan was to return this spring to examine the impacts of deer browse on these seedlings. In particular, we wanted to examine how herbivory varies across space due to changes in deer population densities (in turn driven by factors such as snow depth).
To this end we selected almost 40 forest sites that would hopefully capture some spatial variation in snowfall and that had recently been selectively harvested. At each site we selected 10 gaps produced by timber harvest in which to plant our seedlings.
In each gap we planted six trees of each of three species: White Spruce (Picea glauca), White Pine (Pinus strobus) and Eastern Hemlock (Tsuga canadensis). We chose these coniferous species as these are examples of the mesic confer species the Michigan DNR are trying to restore across our study area, and because we expected a range of herbivory across these species.
At each site we would also undertake deer pellet counts in the spring to estimate the number of deer in the vicinity of the site during the winter (during which time the browse we were measuring would have occurred).
On returning to the study sites a couple of weeks ago we set about looking for the trees we had planted to measure herbivory and count deer pellets. In some cases, finding the trees we planted was easier said than done. We tried to get our field crews to plant the trees in straight lines with equal spacing between each tree. In general, this was done well but on occasion the line could only be described as crooked at best. Micro-topography, fallen tree trunks and limbs, and slash from previous cutting all contributed to hamper the planned planting system. However, we did pretty well and found well over 90% of the trees.
We haven’t begun analyzing our data as yet, but some anecdotal observations stand out. First, the deer preferentially browsed Hemlock over the other species, often removing virtually all non-woody biomass as shown by the ‘before and after’ examples below (NB – these photographs are not of the same tree and this is not a true before/after comparison).


In some cases, the deer not only removed all non-woody biomass but also pulled the tree out of the ground (as shown below).
In contrast, White Pine was browsed to a much lesser extent and White Spruce was virtually untouched (as shown below).
Having a species that was unaffected by deer (i.e. spruce) often made our job of finding the other trees much easier. Finding heavily browsed Hemlock that no longer had any green vegetation was often tricky against a background of forest floor litter.
The next step now is to start looking at this variation in browse through a more quantitative lens. Then we can start examining how browse and deer densities vary across space and how these variables are related to one another and other factors (such as snow depth and distance to conifer stands).
All-in-all the two weeks of work went pretty well. There were some issues with water-logged roads (due to snow melt) meaning we couldn’t get to one or two of the sites we planted at, but generally the weather was pretty good (it only rained heavily one day). I’ll write more once we have done more analysis and stop here with a shot I took at sunrise as I left for home.
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Ecological, Environmental, Geographic, Landscapes, MichiganUP, Photography | Comments Off
Sunday, April 20th, 2008
 A brief and belated summary of the 23rd annual US-IALE symposium in Madison, Wisconsin.
The theme of the meeting was the understanding of patterns, causes, and consequences of spatial heterogeneity for ecosystem function. The three keynote lectures were given by Gary Lovett, Kimberly With and John Foley. I found John Foley’s lecture the most interesting and enjoyable of the three – he’s a great speaker and spoke on a broader topic than the the others; Agriculture, Land Use and the Changing Biosphere. Real wide-ranging, global sustainability stuff. He highlighted the difficulties of studying agricultural landscapes because of the human cultural and institutional factors, but also stressed the importance of tackling these tricky issues because ‘agriculture is the largest disturbance the biosphere has ever seen’ and because of its large contribution to greenhouse gas emissions.
Presentations I was particularly interested in were mainly in the ‘Landscape Patterns and Ecosystem Processes: The Role of Human Societies’, ‘Challenges in Modeling Forest Landscapes under Climate Change’ and ‘Cross-boundary Challenges to the Creation of Multifunctional Agricultural Landscapes’ sessions.
In the ‘human societies’ session, Richard Aspinall discussed the importance of considering human decision-making at a range of scales and Dan Brown again highlighted the importance of human agency in spatial landscape process models. In particular, with regards modelling these systems using agent-based approaches he discussed the difficulty of model calibration at the agent level and stressed that work is still needed on the justification and evaluation phases of agent-based modelling.
The ‘modeling forest landscapes’ session was focused largely around use of the LANDIS and HARVEST models that were developed in and around Wisconsin. In fact, I don’t think I saw any mention of the USFS FVS at the meeting whilst I was there, largely because (I think) FVS has large data demands and is not inherently spatial. LANDIS and HARVEST work at more coarse levels of forest representation (grid cell compared to FVS’ individual tree) allowing them to be spatially explicit and to run over large time and space extents. We’re confident we’ll be able to use FVS in a spatially explicit manner for our study area though, capitalising on the ability of FVS to directly simulate specific timber harvest and economic scenarios.
The ‘multifunctional agricultural landscapes’ session had an interesting talk by Joan Nassauer on stakeholder science and the challenges it presents. Specific issues she highlighted were: 1. the need for a precise, operational definition of ‘stakeholder’ 2. ambiguous goals for the use of stakeholders 3. the lack of a canon of replicable methods 4. ambivalence toward the quantification of stakeholder results
Other interesting presentations were given by Richards Hobbs and Carys Swanwick. Richard spoke about the difficulties of ‘integrated research’ and the importance of science and policy in natural resource management. He suggested that policy-makers ‘don’t get’ systems thinking or modelling, and that some of this may be down to the psychological profiles of the types of people that go into policy making. Such a conclusion suggests scientists need to work harder to bridge the gap to policy makers and do a better job of explaining the emergent properties of the complex systems they study. Carys Swanwick talked about the landscape character assessment, which was interesting for me having moved from the UK to the US about a year ago. Whilst ‘wilderness’ is an almost alien concept in the UK (and Europe as a whole), landscape character is something that is distinctly absent in the new world agricultural landscapes. Carys talked about the use of landscape character as a tool for conservation and management (in Europe) and the European Landscape Convention. It was a refreshing change from many of the other presentations about agricultural landscape (possibly just because I enjoyed seeing a few pictures of Blighty!).
Unfortunately the weather during the conference was wet which meant that I didn’t get out to see as much of Madison as I would have liked. Despite the rain we did go on the Biking Fieldtrip. And yes, we did get soaked. It was also pretty miserable weather for the other fieldtrip to and International Crane Foundation center and the Aldo Leopold Foundation (more on that in a future blog), but interesting nevertheless.
Other highlights of the conference for me were meeting the former members of CSIS and eating dinner one night with Monica Turner. I also got to meet up with Don McKenzie and some of the other ‘fire guys’, and a couple of people from the Great Basin Landscape Ecology lab where I visited previously. And now I’m already looking forward to the meeting next year in Snowbird, Utah (where I enjoyed the snow this winter).
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Ecological, Economic, Environmental, Geographic, Landscapes, MichiganUP, Modelling, Political, Social | Comments Off
Wednesday, March 19th, 2008
Today I started thinking in earnest about the 2008 US-IALE Symposium to be held in Madison, Wisconsin early next month.
I’ll be presenting a poster on our early model development work on the USDA deer/timber regeneration project at CSIS. I will also be chairing the Landscape Change session which has presentations discussing change within and across a diverse range of landscapes including, the Great Plains of the US, the Bolivian Andes and Ukrainian Carpathian mountain ranges, Boreal and Tropical forests, and the Congo Basin.
Whilst in Madison I also plan on attending sessions, symposia, workshops and field-trips devoted to Landscape Patterns and Ecosystem Processes, Modeling Forest Landscapes under Climate Change, Multifunctional Agricultural Landscapes, Forest Landscapes, and Fire. At this last session I’m particularly looking forward to the presentation entitled “Ecological complexity produces simple structure: Power laws in low-severity fire regimes” by Don McKenzie, co-convener of the wildfires session at EGU 2008 the following week (but which I will not be attending).
There will be plenty of other activity by members of CSIS. Jack Liu, president-elect of US-IALE, and CSIS PhD student Vanessa Hull are co-organising the H. Ronald Pulliam Symposium: Sources, Sinks, and Sustainability. Mao-Ning Tuanmu (PhD student) will be making a presentation entitled “Detecting understory vegetation using MODIS data: Implications for giant panda habitat evaluations” in the Remote Sensing session, and Wei Liu (also CSIS PhD student) will present “Conservation success leads to human-wildlife conflicts: Spatial patterns of crop damages and livestock depredation in Wolong Nature Reserve for Giant Pandas, China” in the Social Issues session.
And there’s loads more going on so it promises to be an interesting and busy week! If I get online during a spare 5 minutes I’ll see if I can blog an update on how it’s all going…
 This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Landscapes, MichiganUP | Comments Off
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