Aim The purpose of this study was to reconstruct early nineteenth-century vegetation and fire regimes to examine the role of fire, topography, and substrate interactions in shaping landscape and regional vegetation patterns. LocationOur study area was the Current River watershed of the Ozark Highlands in south-central Missouri, USA. MethodsWe combined analysis of early nineteenth-century Public Land Survey (PLS) notes and dendrochronology-based fire histories to reconstruct vegetation and disturbance regimes of pine-oak (Pinus-Quercus) woodlands.Three methods were used to display and analyse PLS data within a Geographic Information System (GIS): (1) simple point distributions for each tree species; (2) section line descriptions of each tree species and other coded features (e.g. 'prairie'); and (3) spatial interpolation of the point-tree data.Vegetation patterns were then related to geological parent material, topography, and mean fire-return intervals from 23 sites using correlation and Canonical Correspondence Analysis (CCA). ResultsThe most striking patterns in the early 1800 s were extensive stands of shortleaf pine (Pinus echinata Mill.) and oak-dominated 'barrens' (savanna) in the frequently burned areas south-west of the Current River, and more mesophytic, fire-sensitive species (red oaks (Quercus rubra L., Q. coccinea Muenchh.), maples (Acer rubrum L., Acer saccharum Marsh), eastern red cedar (Juniperus virginiana L.) in a fire shadow north-east of the river. Several kilometre-wide ecotones of pine-mixed hardwood encompassed the major pineries and barrens.Fire-return intervals and relative dominance of several tree species were strongly correlated at both fine (3-64 km 2 ) and coarse (> 100 km 2 ) spatial scales. At fine scales, relative dominance of shortleaf pine increased with increasing fire frequency during 1701-1820. Relative dominance of black oak (Q. velutina Lam.), and to a lesser extent post oak (Q. stellata Wang.), decreased with increasing fire frequency. Shortleaf pine and these xerophytic oak species occurred on similar bedrock types but were strongly differentiated by fire regimes. Main conclusions Fires exerted strong constraints on vegetation composition and patterns.Historical patterns of Native American occupancy in the region are consistent with the reconstructed vegetation and fire histories and suggest that anthropogenic fire regimes played an overriding role in the development of Ozark vegetation in the 1800s.

On-the-fly calculations of area and performance are a typical part of the computer-aided iterative design process in VLSI, which aims at a satisfactory tradeoff of various conflicting objectives, among which are test-generation time and test-set size. However, determining test sets on-the-fly as one circuit is transformed into another is extremely difficult. Our goal is to add a test dimension to the design optimization process that complements methods concerned with area and performance optimization. We define a set of logic transformations that result in easily computed changes to test sets. Test-set preserving (TSP) transformations preserve a combinational circuit’s test sets, while test-set altering (TSA) transformations introduce a minimum number of tests needed to maintain completeness. We illustrate our approach with a family of adders that share area-efficient tree structures and differ in the amount of carry-lookahead used to accelerate carry computation. Members include the ripple-carry adder, which has no lookahead, and the standard carry-lookahead adder, which exploits lookahead across all inputs. It is straightforward to derive area and performance measures for this class of adders. Given an n-bit adder with lookahead degree k, we determine a sequence of circuit transformations that produce the adder of degree k2 and test sets of minimum size. Optimal test sets of size k(logkn + 1) + 2 result for arbitrary n and k, which improve significantly upon previously reported tests.