A Compiler Project for Translating a C Subset to SPARC Assembly Language

We present a complete description of a project for a compiler that translates a subset of the C programming language to SPARC assembler language. The project is suitable for a one semester undergraduate course on compilers and interpreters based on the text of Aho, Sethi, and Ullman, and has been used successfully in that context at the University of Pennsylvania. Output that facilitate scoring, and checkpoints for monitoring the students\u27 progress are integral to the project description

Creek habitats as sources for the spread of an invasive herb in a New Zealand mountain landscape

Landscapes typically comprise various habitats that differ in their susceptibility to invasion by exotic species. Highly invasible habitats such as riparian corridors can act as a conduit for rapid movement across the landscape and as a propagule source to facilitate spread into adjacent, less invasible habitats. If this is so, there should be a decline in invader frequency and/or abundance with distance away from the source; the local abundance of invasive species in the source habitat should be positively correlated with local abundance in the adjacent habitat; and, having accounted for variation in local source population size, the slope of the decline in invader abundance with distance away from the source habitat should reflect the ease with which adjacent habitat can be invaded. Here, we test these predictions to assess whether creek habitats function as a source to facilitate the spread of the invasive plant Hieracium lepidulum Stenstr. (Asteraceae) in upland catchments of the South Island, New Zealand, by surveying H. lepidulum abundance in creek margin and adjacent beech forest and subalpine habitat in 17 creek catchments. Our results imply that propagule pressure from populations in creek margins and other disturbed areas is driving catchment-wide H. lepidulum invasion, but forest and subalpine habitats currently differ in the way H. lepidulum spreads from source populations. Our results suggest that H. lepidulum invasion is at an earlier stage in subalpine areas, that there are few barriers to invasion across this habitat, and that subalpine habitats will become more heavily invaded than forests. These findings can be used to underpin monitoring strategies and management prioritisation for this invader

Pronghorn Habitat Suitability in the Texas Panhandle

Habitat quality is an important factor that can greatly affect wildlife populations. Pronghorn (Antilocapra americana) habitat in the Texas Panhandle, USA has been lost through growth of human settlements and agricultural lands. We determined the most pertinent environmental variables affecting habitat selection using multiple methods, including a search of peer-reviewed literature, expert opinion ranking, and habitat suitability modeling. We determined quality and extent of pronghorn habitat in the Texas Panhandle using the MAXENT modeling environment to build a presence-only habitat suitability model based on global positioning system (GPS) locations collected via aerial surveys. Our habitat suitability model indicated that woodlands, agricultural land, and summer precipitation had the greatest contributions to the overall model. Areas with greatest habitat suitability are associated with high pronghorn population densities, particularly in the northwestern corner of the Panhandle. This probabilistic model may serve as a useful tool for pronghorn conservation primarily because it provides insight into what factors are most predictive of their presence, which areas are most suitable for pronghorn, and as a simple, replicable process to identify and evaluate pronghorn habitat

Size-Specific Tree Mortality Varies with Neighbourhood Crowding and Disturbance in a Montane Nothofagus Forest

Tree mortality is a fundamental process governing forest dynamics, but understanding tree mortality patterns is challenging because large, long-term datasets are required. Describing size-specific mortality patterns can be especially difficult, due to few trees in larger size classes. We used permanent plot data from Nothofagus solandri var. cliffortioides (mountain beech) forest on the eastern slopes of the Southern Alps, New Zealand, where the fates of trees on 250 plots of 0.04 ha were followed, to examine: (1) patterns of size-specific mortality over three consecutive periods spanning 30 years, each characterised by different disturbance, and (2) the strength and direction of neighbourhood crowding effects on size-specific mortality rates. We found that the size-specific mortality function was U-shaped over the 30-year period as well as within two shorter periods characterised by small-scale pinhole beetle and windthrow disturbance. During a third period, characterised by earthquake disturbance, tree mortality was less size dependent. Small trees (<20 cm in diameter) were more likely to die, in all three periods, if surrounded by a high basal area of larger neighbours, suggesting that size-asymmetric competition for light was a major cause of mortality. In contrast, large trees (≥20 cm in diameter) were more likely to die in the first period if they had few neighbours, indicating that positive crowding effects were sometimes important for survival of large trees. Overall our results suggest that temporal variability in size-specific mortality patterns, and positive interactions between large trees, may sometimes need to be incorporated into models of forest dynamics