Bonanza Creek Long Term Ecological Research

urban watershed, coastal estuary, eastern deciduous forest, tropical rain forest, tallgrass prairie—these are just a few of the ecosystems represented in the 24 sites of the Long-Term Ecological Research (LTER) Network (Franklin et al. 1990). By combining information from the diverse ecosystems represented in the LTER network, participants have a unique opportunity for large-scale investigations of complex phenomena like climate change, biodiversity, soil dynamics, and environmental policy. In 1996, to facilitate data exchange and synthesis from its multiple sites, LTER launched the LTER Network Information System (NIS), based on an independent site and central office organizational infrastructure. Other organizational partnerships provide examples of earlier efforts also focused on communications and data sharing: the Worm Community System, the Flora of North America Project (FNAP), and the Organization of Biological Field Stations (OBFS). The Worm Community System was developed—before Internet connectivity became available—as a collaborative software environment through which its 1400 widely dispersed researchers could share information on the genetics, behavior, and biology of the soil nematode species Caenorhabditis elegans. Insight into the complexity of a network structure was gained through attention to the design and analysis of both the system’s structure and usability (Star and Ruhleder 1996). The FNAP system, in contrast, was developed with Internet technology. The FNAP, with a goal of identifying and cataloging all plant species, uses online technology to create

Abstract We investigated long‐term and seasonal patterns of N imports and exports, as well as patterns following climate perturbations, across biomes using data from 15 watersheds from nine Long‐Term Ecological Research (LTER) sites in North America. Mean dissolved inorganic nitrogen (DIN) import–export budgets (N import via precipitation–N export via stream flow) for common years across all watersheds was highly variable, ranging from a net loss of − 0·17 ± 0·09 kg N ha −1 mo −1 to net retention of 0·68 ± 0·08 kg N ha −1 mo −1 . The net retention of DIN decreased (smaller import–export budget) with increasing precipitation, as well as with increasing variation in precipitation during the winter, spring, and fall. Averaged across all seasons, net DIN retention decreased as the coefficient of variation (CV) in precipitation increased across all sites ( r 2 = 0·48, p = 0·005). This trend was made stronger when the disturbed watersheds were withheld from the analysis ( r 2 = 0·80, p < 0·001, n = 11). Thus, DIN exports were either similar to or exceeded imports in the tropical, boreal, and wet coniferous watersheds, whereas imports exceeded exports in temperate deciduous watersheds. In general, forest harvesting, hurricanes, or floods corresponded with periods of increased DIN exports relative to imports. Periods when water throughput within a watershed was likely to be lower (i.e. low snow pack or El Niño years) corresponded with decreased DIN exports relative to imports. These data provide a basis for ranking diverse sites in terms of their ability to retain DIN in the context of changing precipitation regimes likely to occur in the future. Copyright © 2008 John Wiley & Sons, Ltd.

As part of a long‐term moose browse/fire severity study, we used the Normalized Burn Ratio (NBR) with historic Landsat Thematic Mapper (TM) imagery to estimate fire severity from a 1983 wildfire in interior Alaska. Fire severity was estimated in the field by measuring the depth of the organic soil at 57 sites during the summer of 2006. Sites were selected for field sampling from five fire severity classes based on threshold NBR values. The linear relationship between post‐fire NBR and organic soil depth among sites within the burn was weak (r 2 = 0.26), and improved substantially (r 2 = 0.66) when restricted to non‐wetland black spruce sites. The relationship between NBR and aspen/willow counts was non‐linear. Sites with high densities of aspen stems consistently occurred in the high fire severity classes, and sites with high willow stem densities consistently occurred in the moderate fire severity class. However, NBR varied substantially from sites with low aspen or willow reproduction and therefore predicting aspen or willow regeneration based on post‐fire NBR values would be difficult.