ABSTRACT
Contemporary terrestrial laser scanning (TLS) is being used widely in forest ecology applications to examine ecosystem properties at increasing spatial and temporal scales. Harvard Forest (HF) in Petersham, MA, USA, is a long-term ecological research (LTER) site, a National Ecological Observatory Network (NEON) location and contains a 35 ha plot which is part of Smithsonian Institution's Forest Global Earth Observatory (ForestGEO). The combination of long-term field plots, eddy flux towers and the detailed past historical records has made HF very appealing for a variety of remote sensing studies. Terrestrial laser scanners, including three pioneering research instruments: the Echidna Validation Instrument, the Dual-Wavelength Echidna Lidar and the Compact Biomass Lidar, have already been used both independently and in conjunction with airborne laser scanning data and forest census data to characterize forest dynamics. TLS approaches include three-dimensional reconstructions of a plot over time, establishing the impact of ice storm damage on forest canopy structure, and characterizing eastern hemlock (Tsuga canadensis) canopy health affected by an invasive insect, the hemlock woolly adelgid (Adelges tsugae). Efforts such as those deployed at HF are demonstrating the power of TLS as a tool for monitoring ecological dynamics, identifying emerging forest health issues, measuring forest biomass and capturing ecological data relevant to other disciplines. This paper highlights various aspects of the ForestGEO plot that are important to current TLS work, the potential for exchange between forest ecology and TLS, and emphasizes the strength of combining TLS data with long-term ecological field data to create emerging opportunities for scientific study.
ABSTRACT
The composition, structure and dendroecology of a 320-year-old Pinus rigida rock outcrop community was studied in the Shawangunk Mountains of southeastern New York. This represents one of the oldest known examples of this forest type and it is located on one of the most extreme sites in the northeastern United States. P. rigida represented 88% of all sampled trees, which typically grew on individual soil islands with soil depths of 8-35 cm surrounded by exposed bedrock. The forest was uneven-aged and P. rigida exhibited continuous recruitment into the tree size classes since the late 1600s, suggesting that it represents a physiographic climax for this species. However, a limited amount of Nyssa sylvatica and Quercus prinus recruitment started after 1830. Peak recruitment of P. rigida trees in 1720-1760 and 1860-1890 coincided with parabolic-shaped releases in their radial growth, possibly in response to disturbances. Tree ring growth was typically <0.4 mm/year since the 1850s and <0.3 mm/year during a prolonged and severe drought in the 1960s. However, large increases in precipitation and temperature from 1970 to 1993 were correlated with a dramatic post-drought growth response producing the highest ring width index values throughout the life of 260 to 280-year-old trees. Thus, we attribute certain moderate growth releases (>50%) lasting 10-15 years to climate, rather than disturbance. Tree growth and recruitment at the study site were influenced by a complex interaction of climate, soil and disturbance factors. Coupling of species recruitment, tree ring and climatic data in this study provided an improved technique for understanding forest growth and dynamics.