Andrew G. Birt

Simulating the reciprocal interaction of forest landscape structure and southern pine beetle herbivory using LANDIS

The reciprocal interaction of landscape structure and ecological processes is a cornerstone of modern landscape ecology. We use a simulation model to show how landscape structure and herbivory interact to influence outbreaks of southern pine beetle (Dendroctonus frontalis Zimmermann) in a landscape representative of the southern Appalachian Mountains, USA. We use LANDIS and its biological disturbance agent module to simulate the effects of landscape composition (proportion of landscape in host area) and host aggregation on the size and severity of insect outbreaks and the persistence of the host species, Table Mountain Pine (Pinus pungens Lamb.). We find that landscape composition is less important in the modeled landscapes than host aggregation in structuring the severity of insect outbreaks. Also, simulated southern pine beetle outbreaks over time tend to decrease the aggregation of host species on the landscape by fragmenting large patches into smaller ones, thereby reducing the severity of future outbreaks. Persistence of Table Mountain pine decreases throughout all simulations regardless of landscape structure. The results of this study indicate that when considering alternative restoration strategies for insect-affected landscapes, it is necessary to consider the patterns of hosts on the landscape as well as the landscape composition.

Stage-structured matrix models for organisms with non-geometric development times

Matrix models have been used to model population growth of organisms for many decades. They are popular because of both their conceptual simplicity and their computational efficiency. For some types of organisms they are relatively accurate in predicting population growth; however, for others the matrix approach does not adequately model growth rate. One of the reasons for the lack of accuracy is that most matrix-based models implicitly assume a specific degree of variability in development times for the organism. Because the variability is implicit, the implied variances are often not verified with experimental data. In this paper, we shall present extensions to the stage-classified matrix models so that organisms with arbitrary means and standard deviations of development times can be modeled.

Computer-based synthetic data to assess the tree delineation algorithm from airborne LiDAR survey

Small Footprint LiDAR (Light Detection And Ranging) has been proposed as an effective tool for measuring detailed biophysical characteristics of forests over broad spatial scales. However, by itself LiDAR yields only a sample of the true 3D structure of a forest. In order to extract useful forestry relevant information, this data must be interpreted using mathematical models and computer algorithms that infer or estimate specific forest metrics. For these outputs to be useful, algorithms must be validated and/or calibrated using a sub-sample of ‘known’ metrics measured using more detailed, reliable methods such as field sampling. In this paper we describe a novel method for delineating and deriving metrics of individual trees from LiDAR data based on watershed segmentation. Because of the costs involved with collecting both LiDAR data and field samples for validation, we use synthetic LiDAR data to validate and assess the accuracy of our algorithm. This synthetic LiDAR data is generated using a simple geometric model of Loblolly pine (Pinus taeda) trees and a simulation of LiDAR sampling. Our results suggest that point densities greater than 2 and preferably greater than 4 points per m2 are necessary to obtain accurate forest inventory data from Loblolly pine stands. However the results also demonstrate that the detection errors (i.e. the accuracy and biases of the algorithm) are intrinsically related to the structural characteristics of the forest being measured. We argue that experiments with synthetic data are directly useful to forest managers to guide the design of operational forest inventory studies. In addition, we argue that the development of LiDAR simulation models and experiments with the data they generate represents a fundamental and useful approach to designing, improving and exploring the accuracy and efficiency of LiDAR algorithms.

Short communication: LANDISVIEW: A visualization tool for landscape modelling

A major challenge in landscape and environmental modelling is to effectively visualize large amounts of time-series simulation output, often in various Geographic Information System (GIS) formats. We developed a software tool (LANDISVIEW), to easily visualize and animate time-series of ERDAS *.gis maps. The open source tool can also be used to generate batch files for FRAGSTATS, a widely used spatial analysis program.

Short communication: A simple stochastic weather generator for ecological modeling

Stochastic weather generators are useful tools for exploring the relationship between organisms and their environment. This paper describes a simple weather generator that can be used in ecological modeling projects. We provide a detailed description of methodology, and links to full C++ source code (http://weathergen.sourceforge.net) required to implement or modify the generator. We argue that understanding the principles of weather generation will allow ecologists to tailor a solution for their own requirements. The detailed, repeatable methodology we present demonstrates that weather generation is relatively straightforward for ecologists to implement and modify.

Restoration of Southern Pine Forests After the Southern Pine Beetle

The southern pine beetle (Dendroctonus frontalis Zimmermann) is the most destructive insect pest of pine (Pinus spp.) forests in the southern United States. Restoring and managing pine stands infested by southern pine beetle are critically important for forest health and sustainability in the region. The successful restoration of damaged pine forests requires the integration of information of beetle biology and behavior, pine ecology, and landscape restoration. Certain social, economic, and political issues also need to be considered concomitantly. The knowledge for effective restoration and management of southern pine forests has increased greatly in the past decade. In this chapter, we provide a synthesis of new and existing knowledge to address the goals, framework, implementation, social and political impacts on the restoration of the southern pine forests in the context of southern pine beetle. We also provide information on common restoration methods and cost estimates. More effective use and further development of such knowledge could substantially reduce the economic, ecological, and social impact of southern pine beetle within the southern United States and adjacent areas.

Harnessing Information Technology (IT) for Use in Production Agriculture

Internet based, Information Technology (IT) offers opportunities to agricultural scientists to share information important to production agriculture. We offer an objective view for how IT can be used to manipulate data, information, and knowledge. The application of these technologies in other domains serves as a lesson to how they might be used to benefit production agriculture. We discuss three related technologies that have the potential to improve information flow among agricultural stakeholders and identify a number of trends (increased robustness, standardization of data formats, and reduced cost of implementation) that make them impor- tant tools for production agriculture.

Viewing Woody-Plant Encroachment through a Social–Ecological Lens

Grasslands and savannas worldwide have been dramatically altered by woody-plant encroachment (WPE). Maintaining remnant grasslands and restoring degraded grasslands for the people and animals that depend on them will require a new paradigm for WPE, one that views WPE as a complex social–ecological system. Here, we examine WPE in this light, using a conceptual framework designed to bridge the biophysical and social domains. On the basis of this press–pulse WPE framework, we develop a set of integrative hypotheses and identify key knowledge gaps using the Southern Great Plains as a case study. An alternative—and potentially complementary—approach to the press–pulse WPE framework is that of classical dynamic systems modeling, which has been widely adopted in ecology and economics. The explicit coupling of the press–pulse WPE framework with dynamic systems modeling has the potential to yield new insights for understanding the localto regional-scale processes that drive and constrain changes in grass–woody plant abundances and for predicting the socioeconomic and ecological consequences of these changes.

Forest landscape management in response to change: the practicality

In this chapter, we examined forest landscape management from a pragmatic (practical as opposed to idealistic) perspective. The discussion was framed in the context of the landscape: a spatially explicit geographic area consisting of recognizable and characteristic component ecosystems. This perspective provided two opportunities for management: the individual component ecosystems and the mosaic of ecosystems that form the landscape per se. A point of emphasis was that forest management is not a generic concept and requires specification of the purpose of management, the spatial unit(s) being managed, the type of forest being managed, and the projected desired outcome of management. Given these constraints, we considered how the principal drivers of landscape change (disturbances, climate, and domestication) influence forest management practices. We concluded with an examination of the concept of designed forest landscapes to provide human-valued goods and services and identified constraints to achieving this end.

An integrated approach to mapping forest conditions in the Southern Appalachians (North Carolina)

©2008 by the Board of Regents of the University of Wisconsin System. An Integrated Approach to Mapping Forest Conditions in the Southern Appalachians (North Carolina) Weimin Xi (Knowledge Engineering lab, texas a&M University, college station, tX 77843, xi@tamu.edu), lei Wang (Dept of geography and anthropology, louisiana state University, Baton Rouge, la 70803), andrew g. Birt (Knowledge Engineering lab), Maria D. tchakerian (Knowledge Engineering lab), Robert n. coulson (Knowledge Engineering lab), Kier D. Klepzig (U.s. Forest service southern Research station, 2500 shreveport Hwy, Pineville, la 71360)