Late Successional Taxa Research Articles

New insights into endolithic palaeocommunity development in mobile hard substrate using CT imaging of bioeroded clasts from the Pliocene (Almería, SE Spain).

Bioeroded carbonate clasts from a Pliocene shallow-marine succession of Almería (SE Spain, Betic Cordillera) were analysed with computed tomography (CT). This revealed the detailed 3D architecture of bioerosion structures hidden within and allowed for their ichnotaxonomic identification (14 ichnospecies of 5 ichnogenera) and quantification. Borings are produced by worms, mostly polychaetes and sipunculids dominated, followed by bivalves and lastly by sponges. The crosscutting relationship between the borings and their preservation characteristics points to a complex colonization history of the clasts with repeated bioerosive episodes interrupted by physical disturbances, including overturning and abrasion of the clasts followed by their recolonization. Our findings facilitated paleoenvironmental interpretation and can be compared to analogous modern-day ecological succession. The sharp dominance of worm borings - early successional species - may be related to frequent, periodic, physical disturbance that possibly prevented the cobble-dwelling macroboring community from being overtaken by sponges - late successional taxa. CT, hand sample and petrographic observations detected, aside from borings, other irregularly shaped pores which are interpreted to be generated by diagenetic processes including dolomitization, silicification and dissolution, representing an intraparticle moldic and moldic enlarged porosity. Boring porosity crosscutting the diagenetically altered grains suggests the later occurrence of bioerosion processes. Irregular shapes ranging from roughly spherical, elongate sub-polyhedral to amoeboid resemble morphologies produced by modern sponges. Moldic pores possibly acted as primary domiciles for boring sponges, which infested, altered and enlarged pre-existing pores as they grew (as happens in the modern), providing an example of how biological and non-biological processes interacted and together influenced endolithic palaeocommunity development.

Four Centuries of Change in Northeastern United States Forests

The northeastern United States is a predominately-forested region that, like most of the eastern U.S., has undergone a 400-year history of intense logging, land clearance for agriculture, and natural reforestation. This setting affords the opportunity to address a major ecological question: How similar are today's forests to those existing prior to European colonization? Working throughout a nine-state region spanning Maine to Pennsylvania, we assembled a comprehensive database of archival land-survey records describing the forests at the time of European colonization. We compared these records to modern forest inventory data and described: (1) the magnitude and attributes of forest compositional change, (2) the geography of change, and (3) the relationships between change and environmental factors and historical land use. We found that with few exceptions, notably the American chestnut, the same taxa that made up the pre-colonial forest still comprise the forest today, despite ample opportunities for species invasion and loss. Nonetheless, there have been dramatic shifts in the relative abundance of forest taxa. The magnitude of change is spatially clustered at local scales (<125 km) but exhibits little evidence of regional-scale gradients. Compositional change is most strongly associated with the historical extent of agricultural clearing. Throughout the region, there has been a broad ecological shift away from late successional taxa, such as beech and hemlock, in favor of early- and mid-successional taxa, such as red maple and poplar. Additionally, the modern forest composition is more homogeneous and less coupled to local climatic controls.

Effects of clearance and fragmentation on forest compositional change and recovery after 200 years in western New York

This study investigated the effects of widespread forest clearance and fragmentation on forest compositional change between pre-settlement and the present (ca. 1800-1993) in western New York. Forest compositional turnover metrics were calculated to evaluate whether soil conditions accounted for the forest compositional change, to investigate how forest clearance might have contributed to the change, and to compare with the amount of change noted in other studies that compared the pre-settlement land sur- veys and the current Forest Inventory and Analysis (FIA) surveys. The results suggested weak relations between the forest compositional change and soil conditions. The amount of change at the county level was positively correlated with the amount of forest clearance by the late 1800s and negatively correlated with the amount of remnant forest in the late 1800s. Furthermore, while the geographic distributions of late-successional taxa in the study area exhibited increased patchiness and decreased contagion, those of early-successional taxa exhibited decreased patch- iness and increased contagion. Comparison of taxa's changed abundances with seven life history charac- teristics commonly associated with early- and late- successional status showed that taxa's changed abun- dances were significantly related to maximum life and shade tolerance. Analysis of different-sized trees in different ages in the FIA survey indicated the possibility of the current forests trending back toward their pre-settlement composition.