The Effects of Density, Spatial Pattern, and Competitive Symmetry on Size Variation in Simulated Plant Populations

Patterns of size inequality in crowded plant populations are often taken to be indicative of the degree of size asymmetry of competition, but recent research suggests that some of the patterns attributed to size‐asymmetric competition could be due to spatial structure. To investigate the theoretical relationships between plant density, spatial pattern, and competitive size asymmetry in determining size variation in crowded plant populations, we developed a spatially explicit, individual‐based plant competition model based on overlapping zones of influence. The zone of influence of each plant is modeled as a circle, growing in two dimensions, and is allometrically related to plant biomass. The area of the circle represents resources potentially available to the plant, and plants compete for resources in areas in which they overlap. The size asymmetry of competition is reflected in the rules for dividing up the overlapping areas. Theoretical plant populations were grown in random and in perfectly uniform spatial patterns at four densities under size‐asymmetric and size‐symmetric competition. Both spatial pattern and size asymmetry contributed to size variation, but their relative importance varied greatly over density and over time. Early in stand development, spatial pattern was more important than the symmetry of competition in determining the degree of size variation within the population, but after plants grew and competition intensified, the size asymmetry of competition became a much more important source of size variation. Size variability was slightly higher at higher densities when competition was symmetric and plants were distributed nonuniformly in space. In a uniform spatial pattern, size variation increased with density only when competition was size asymmetric. Our results suggest that when competition is size asymmetric and intense, it will be more important in generating size variation than is local variation in density. Our results and the available data are consistent with the hypothesis that high levels of size inequality commonly observed within crowded plant populations are largely due to size‐asymmetric competition, not to variation in local density.

Digital Vertical Aerial Camera System for High-resolution Site Inspections in Conservation Easment Monitoring

A three-level satellite to ground monitoring scheme for conservation easement monitoring has been implemented in which high-resolution imagery serves as an intermediate step for inspecting high priority sites. A digital vertical aerial camera system was developed to fulfill the need for an economical source of imagery for this intermediate step. A method for attaching the camera system to small aircraft was designed, and the camera system was calibrated and tested. To ensure that the images obtained were of suitable quality for use in Level 2 inspections, rectified imagery was required to provide positional accuracy of 5 meters or less to be comparable to current commercially available high-resolution satellite imagery. Focal length calibration was performed to discover the infinity focal length at two lens settings (24mm and 35mm) with a precision of O.1mm. Known focal length is required for creation of navigation points representing locations to be photographed (waypoints). Photographing an object of known size at distances on a test range allowed estimates of focal lengths of 25.lmm and 35.4mm for the 24mm and 35mm lens settings, respectively. Constants required for distortion removal procedures were obtained using analytical plumb-line calibration procedures for both lens settings, with mild distortion at the 24mm setting and virtually no distortion found at the 35mm setting. The system was designed to operate in a series of stages: mission planning, mission execution, and post-mission processing. During mission planning, waypoints were created using custom tools in geographic information system (GIs) software. During mission execution, the camera is connected to a laptop computer with a global positioning system (GPS) receiver attached. Customized mobile GIs software accepts position information from the GPS receiver, provides information for navigation, and automatically triggers the camera upon reaching the desired location. Post-mission processing (rectification) of imagery for removal of lens distortion effects, correction of imagery for horizontal displacement due to terrain variations (relief displacement), and relating the images to ground coordinates were performed with no more than a second-order polynomial warping function. Accuracy testing was performed to verify the positional accuracy capabilities of the system in an ideal-case scenario as well as a real-world case. Using many welldistributed and highly accurate control points on flat terrain, the rectified images yielded median positional accuracy of 0.3 meters. Imagery captured over commercial forestland with varying terrain in eastern Maine, rectified to digital orthophoto quadrangles, yielded median positional accuracies of 2.3 meters with accuracies of 3.1 meters or better in 75 percent of measurements made. These accuracies were well within performance requirements. The images from the digital camera system are of high quality, displaying significant detail at common flying heights. At common flying heights the ground resolution of the camera system ranges between 0.07 meters and 0.67 meters per pixel, satisfying the requirement that imagery be of comparable resolution to current highresolution satellite imagery. Due to the high resolution of the imagery, the positional accuracy attainable, and the convenience with which it is operated, the digital aerial camera system developed is a potentially cost-effective solution for use in the intermediate step of a satellite to ground conservation easement monitoring scheme.

Anhang zu Wolfgang Amadeus Mozart's Biographie : nach Originalbriefen, Sammlungen alles über ihn Geschriebenen, mit vielen neuen Beylagen ...

von Georg Nikolaus von Nissen. Nach dessen Tode hrsg. von Constanze, Wittwe von Nissen, früher Wittwe Mozart

Biographie W. A. Mozart's : nach Originalbriefen, Sammlungen alles über ihn Geschriebenen, mit vielen neuen Beylagen ...

von Georg Nikolaus von Nissen. Nach dessen Tode hrsg. von Constanze, Wittwe von Nissen, früher Wittwe von Mozart

Wahre Abcontrafactur deß Processes, Welcher bey der Crönung deß Durchleuchtigsten, Großmächtigen Fürsten vnd Herrn, Herrn Friderichen deß Ersten, Königs in Böheim, Pfaltzgrafen bey Rhein vnd ... : den 4 Novemb. Neuen Calenders ... des 1619 Jahrs zu Prag gehalten worden

Bibliograph. Nachweis: Paas P-438; Sehr ähnliches von E. Kieser in d. Messrelation zur Fastenmesse 1620 (Nachstich od. Vorlage?)

Ms. or. 133 - Theologische Sammelhandschrift

Vorbesitzer: Negus Hezkejas; Eduard Rüppell

Na 1 Nachlass Max Horkheimer, 637 - "Art and Mass Culture" (p. IX 14.1-2)

"Art and Mass Culture" (GS 4, S. 419-438); 1. Aufsatz, veröffentlicht in: SPSS IX, 1941, S. 290-304; 2. Exzerpt aus: Mortimer Adler, "Art and Prudence", Part II und VI. Typoskript mit handschriftlichen Korrekturen. 18 Blatt;

Perlen der heiligen Andacht und der wahren Frömmigkeit : eine Sammlung der vorzüglichsten Gebete und Erbauungen für katholische Christen

von A. Schalk

Ms. lat. qu. 105 Bd. 2 - Les vies des plus sçavans et des plus renommés architectes, peintres, sculpteurs, graveurs et orfevres, de l'antiquité recueillies

Vorbesitzer: Julius H. Jeidels; Bibliothek für Kunst und Technik Frankfurt am Main