CLAMP (Climate Leaf Analysis Multivariate Program) is a powerful paleoclimate proxy with the ability to yield quantitative data on past temperatures, precipitation, growing season length, and humidity, as well as enthalpy (a property of a parcel of air that is useful in studies of paleoaltimetry). Commonly quoted uncertainties in CLAMP predictions relate to the statistical uncertainty inherent in the combined quality of the modern calibration data sets and the relationship of foliar architecture to the various climate parameters. This minimum uncertainty assumes that the fossil assemblage represents faithfully the foliar physiognomy of the source vegetation.

Taphonomic processes degrade this physiognomic fidelity. Differential selection for size, shape, and species composition during transport and post-depositional processes biases the physiognomic profile of the fossil assemblage. The sensitivity of CLAMP precision to taphonomic filtering was assessed empirically using a modern data set from the Crimean Peninsula as a proxy fossil site. Elimination of leaf margin, apex, base, size, and shape character-state categories, singly and in combination, changed the predictive capability of CLAMP. Loss of margin characters had the greatest effect, particularly on temperature-related variables (mean annual, warm-month mean and cold-month mean temperatures, length of the growing season, and enthalpy). Taphonomic selection against large leaf sizes had little effect even on moisture-related estimates (precipitation during the growing season, mean monthly growing season precipitation, precipitation during the three wettest and driest months, relative humidity). Loss of taphonomically sensitive characters (apex, base, or shape) also had little effect on CLAMP predictions.

Modern biodiversity hotspots are characterized by high species diversity and by biotas facing a substantial threat of extinction, largely due to a high proportion of endemic taxa living in these regions. Theoretically, hotspots of biodiversity are areas of particular interest in the fossil record because of the relatively high quality and quantity of data that they may contribute to a global understanding of vegetational response to changes in climate, tectonic uplift, and ecological disturbance. Current models for climatic reconstruction that depend on leaf physiognomy are based on data sets in which species-rich tropical floras are less well represented, relative to temperate floras. Eight modern Neotropical floras from a range of precipitation regimes were evaluated to determine the influence that high source floral diversity has on reconstruction of mean annual temperature (MAT) and mean annual precipitation (MAP). Floras are drawn from sites in Costa Rica to southern Peru, having species richness from 55 to >400 species per plot. MAT of the sites spans a range of 24 to 28°C, and MAP ranges from ∼1600 mm to 3000 mm. By subsampling the modern floras in rank order of dominance (basal area), the importance of collecting intensity and completeness on subsequent assessments of MAT and MAP is evaluated. Biodiverse floras are good at reconstructing MAT if at least 50% of the species are included. When only 25 species are used for temperature calculations, the accuracy of the parameter is compromised, but a ±3°C error encompasses the majority of the deviation. Application to the early Paleocene Castle Rock fossil flora of Colorado confirms the validity of subsampling in high-diversity fossil applications. However, reconstruction of MAP is fraught with problems that do not appear to be related to biodiversity of the floras. Errors on estimates of MAP currently are so large as to make the values too vague to be useful in most applications. This study has accepted a 20% error as necessary, but the applicability of data with errors > 20% is questionable in situations where rainfall is >1500 mm per year. MAP estimates using leaf area are almost universally underestimates of actual MAP, and frequently are >400 mm in error. Exploration of these data indicates that effort would be well placed in investigating the relative importance of precipitation parameters in altering leaf morphology before choosing one to reconstruct climates of the past.

Taphonomic processes that may bias plant-fossil assemblages are important in explaining many aspects of the Cenozoic plant fossil record. Two tree genera, Eucalyptus and Nothofagus, are especially important for understanding the evolution of Australia's forests, because the former currently dominates the continent, whereas the latter is dominant in Cenozoic microfloras. Nothofagus also is prominent in temperate forests of South America and New Zealand, and in the Cenozoic history of these land-masses and Antarctica. This study measures standing biomass and leaf-litter production in contiguous cool temperate rainforest dominated by nanophyllous Nothofagus cunninghamii and wet sclerophyll forest dominated by macrophyllous Eucalyptus regnans in southeastern Australia. It tests an a priori hypothesis that the under-representation of Eucalyptus in the Australian Cenozoic record may reflect differential organ production by Eucalyptus and Nothofagus, respectively. A taphonomic bias was observed between the standing crop and leaf-litter production among the five canopy species that were examined. Nothofagus cunninghamii has particularly high levels of leaf production relative to standing biomass, while E. regnans has low levels of leaf production relative to its standing biomass. It also was found that when there are large differences in leaf size, leaf counts do not accurately reflect rank-order dominance patterns in the standing vegetation, whereas measurements of leaf area do reflect the general dominance patterns. These data are used to reevaluate the earliest reliable Australian Eucalyptus fossil locality, the Late Oligocene Berwick Quarry Flora, which contained both Nothofagus leaves and pollen. This reevaluation indicates that Nothofagus was present in, but did not dominate, the original vegetation, and Eucalyptus may have been more common than previously considered.

Large, well-preserved carpofloras from Miocene and Pliocene lignite-bearing sequences of the Lower Rhine Basin in Germany occur in a variety of fluvial and lacustrine facies, including channel, point-bar, cut-off channel (oxbow-lake), crevasse-splay, channel-bar (sand-gravel flat), and lake-delta deposits. Despite their occurrence in a wide spectrum of depositional facies, the accumulations share a suite of distinctive characteristics. They appear as a jumble of woody material dominated by abraded pieces of wood, including conifer cones, woody fruits, seeds, small branches, and charcoal in an unconsolidated matrix of medium- or coarse-grained sand. The key characteristic of the fossil plant remains is woodiness. Close association between the lignified material and these grain sizes indicates that these woody fruits are hydrodynamically equivalent to medium- to coarse-sized sand, and were transported as bedload during flood events. Transport by bedload also is evidenced by the high degree of roundness in associated wood clasts, by abrasion in some diaspores, and by the lack of non-resistant plant parts (e.g., leaves, flowers, fleshy or delicate tissues) in the accumulations. Thus, the lignified plant remains behave as sedimentary clasts in the water column, but only after they have been fully saturated with water. Mass carpological accumulations in very coarse-grained sand on active point bars in the Sieg River near Bonn and their formation during events of extreme discharge serve as a modern analog for the fossil carpofloras. New terminology and concepts pertaining to these mass carpological deposits, or “bedload carpodeposits,” also include the terms “bedload carpobiofacies,” and “bedload carpolithofacies.” A basic depositional model for the genesis of bedload carpodeposits is presented.

The terrestrial crisis that reportedly parallels the P/Tr marine mass extinction is based mainly on Northern Hemisphere microfloral assemblages and Southern Hemisphere Gondwanan macrofloral collections. It is well established that taphonomic filters control the ultimate collectable fossil assemblage in any depositional regime. Recognition and comparison of isotaphonomic assemblages are critical before conclusions can be drawn about evolutionary trends over time. Such an approach has been taken in the investigation of pre-boundary, trans-boundary, and post-boundary plant-fossil assemblages in the Karoo Basin, South Africa.

Fourteen stratigraphic sections were evaluated in the Balfour and Normandien formations (Lower Beaufort Group), Katberg Formation, and overlying Burgersdorp Formation (Upper Beaufort Group). These include previously published (e.g., Bulwer, Bethulie, Carlton Heights, Wapadsberg, Commando Drift) as well as newly discovered (e.g., Clouston Farm) localities, and span the Late Permian to Middle Triassic. Fossiliferous intervals were characterized with respect to their sedimentology and plant taphonomy, and bulk collections were made at several stratigraphic levels for future evaluation of floristic and plant-insect associational trends.

The depositional regimes and plant taphonomic character of assemblages change through time. Much of the Lower Beaufort Group is characterized by parautochthonous assemblages within oxbow-lake channel fills. Below the P/Tr boundary, these are replaced by allochthonous assemblages, poorly preserved in lateral-accretion deposits and barforms of relatively shallow fluvial nature. Allochthonous assemblages within the same fluvial context continue across the boundary into the earliest Triassic (Palingkloof Member and Katberg Formation, and typify the Middle Triassic where scour-and-fill structures preserve plant debris. Based on the literature, parautochthonous assemblages reappear in the Upper Triassic Molteno Formation. Hence, the change in taphonomic regime to poorly preserved allochthonous assemblages (dispersed, fragmentary adpressions) at the critical interval on either side of the P/Tr extinction event, but not coincident with, requires extreme caution when interpreting global patterns from these data. Additionally, the presence of plant fossils in the Early Triassic provides evidence for a vegetated landscape during a time when sedimentation patterns are interpreted to be the result of a land-plant die-off.

Leaf margin analysis (LMA), which is based on a correlation between the proportion of woody dicot species with non-toothed leaf margins and mean annual temperature, has been promoted as a tool for estimating mean annual temperature (MAT) from fossil-leaf assemblages. The original LMA calibration was based on East Asian mesic vegetation, and substantially the same relationship has been shown for other geographical regions, including Australian mesic vegetation. In this report, taphonomic effects are assessed using autochthonous samples from extant Australian forests for sites ranging from tropical lowland rainforest and monsoonal deciduous woodland to temperate rainforest with and without emergent Eucalyptus, and for parautochthonous and allochthonous (i.e., streambed) leaf accumulations. MAT was estimated within the binomial sampling error of the estimate for 27 of 30 (90%) of the test sites, and was found to underestimate MAT systematically when applied to streambed leaf assemblages. This result may reflect the streamside bias detected in recent studies of tropical forests in South America. Sites where MAT was overestimated are of low species richness (<10 spp.).