Ecosystem Response

Results from field studies of Hurricane Hugo at various sites across the LUQ are summarized in this section. (For more details, see Walker et al. 1991, 1996.) Damage patterns. Across the LUQ, wind damage was greatest on exposed northern slopes and in eastern sections closer to the hurricane track (Scatena and Larsen 1991). At El Verde, more than half of the trees were severely defoliated (56 ), whereas some trees were snapped (11 ) or uprooted (9 ), though overall mortality was low (7 ) (Walker...

Drought as a Disturbance Regime

Severe drought has been implicated as a contributing factor to recent accelerated rates of tree mortality in the southeastern United States (Tainter et al. 1984 Starkey Table 3.2 Comparison of rainfall between two sampling periods at Coweeta Hydrologic Laboratory near Otto, North Carolina, USA Mean annual precipitation (mm) 1431 2010 Relative to long-term mean ( ) -20 +12 Mean growing season precipitation (mm) 634 913 Relative to long-term mean ( ) -14 +17 Number of consecutive growing season...

David Greenland

When temporally smoothed data are used for the period 1925 to 1985 there is a close inverse statistical relationship acting at an inter-decadal timescale between the Pacific Northwest (PNW) air temperatures and Coho salmon catch off the coast of Washington and Oregon. This relationship is now well known, although not fully explained, but at the time of its discovery in 1994 it was part of advances being made by several research groups on interdecadal-scale climate ecological changes in the PNW...

Drivers of Climate Variability

The energy that drives the earth's climate originates with the sun. Variability in the output of solar energy occurs at a variety of timescales from interannual to millennial. At the timescales investigated here, sunspots are the major mechanism of variation in solar irradiance (Landscheit 1983). During active sun periods (i.e., periods of increased sunspots), solar irradiance increases. Systematic human observations of sunspot cycles have been made for over 300 years, and they indicate an...

Completion of Ecological Response

Our framework question asks, Is the ecosystem effect or response completed by the time of the start of the next climate event or episode This question can be asked in different ways such as in the three questions posed by Boose (chapter 2) in his hurricane study. The question can also be posed implicitly in different contexts. For example, Parmesan et al. (2000, p. 446) have stated the initial resistance, trajectory of response, and extent to which a system returns to original conditions...

Douglas G Martinson Sharon E Stammerjohn

The El Nino-Southern Oscillation (ENSO) is one of the most important contributors to interannual variability on Earth (Diaz and Markgraf 2000). It is an aperiodic phenomenon that tends to reoccur within the range of 2 to 7 years, and it is manifest by the alternation of extreme warm (El Ni o) and cold (La Ni a) events. There is also evidence (Allen 2000) that the aperiodic ENSO phenomenon must be considered in conjunction with climate fluctuations at decadal to multidecadal time frames that may...

Variability of Climate and Related Physical Factors

The 11-year climate record for the Toolik Lake site (table 5.1) indicates a mean daily air temperature of -8.8 C and a total annual precipitation of 315 mm. Monthly means are above freezing for 3 months, and most of the precipitation occurs from June through September. In figure 5.2, the year-to-year variability for two biologically important indices, the annual degree-days above 0 C and the summer rainfall, illustrate the nearly twofold difference from year to year. Solar radiation is a very...

Future Research

From this discussion it is clear that the LTER program provides a platform from which a huge amount of information emerges on the topic of climate variability and ecosystem response. Based on the information in this book, many avenues of research on this topic will be important in the future. 1. We must continue to obtain more information at each LTER site on climate as a disturbance factor of ecosystems. Each new piece of information on this topic alters our perspective of the principles that...

Douglas G Goodin Maurice J McHugh

The five chapters of part III provide a broad overview of decadal-scale climate processes and their ecological effect in a variety of ecosystems. Written by authors with disciplinary backgrounds that encompass climatology, biometeorology, and ecology, the chapters range from cross-site climate analysis with little direct attention to ecosystem effects (e.g., McHugh and Goodin, chapter 11 Hayden and Hayden, chapter 14) to more intensive studies of direct climate ecological interaction at single...

Regulation of ANPP in Tallgrass Prairie

Climate variability is one of several important biotic and abiotic factors regulating ANPP in tallgrass prairie. Multiple factors, including fire, nutrients, grazing by large ungulates, and topography, are involved in the regulation of ANPP in tall-grass prairie. For example, a synthesis of a 20-year record of ANPP at Konza Prairie showed that, in general, early growing-season fire and moderate-intensity grazing increased ANPP (Knapp et al. 1998). Herbivores and fire in some ways have similar...

Long Term Effects of Drought on Ecosystems

Several studies characterize the ecological effect of the drought of 1988. Tilman and Downing (1994) provided documentation of drought effects on plant communities other than those in agriculture. They characterized the influence of the 1988 drought on plants at the Cedar Creek LTER in Minnesota, and they measured the effects of drought and the dynamics of recovery from drought against a known baseline. Indeed, it was not until 1993, the fifth year after the 1988 drought and the twelfth year of...

The LTER Program

The LTER program conducts and facilitates ecological research at 24 sites in the United States and the Antarctic. More sites are likely to be added to the LTER network in the future. There is also an important and growing International LTER (ILTER) program (LTER Network Office 1998). The U.S. LTER research sites operate as a network with a network office located at the University of New Mexico at Albuquerque. The network is a collaborative effort involving more than 1100 scientists and...

System Cascades

Of all the guiding questions for this book, research on cascades in systems has been the most fruitful. This is because it strikes to the heart of explaining how the systems operate. Indeed, the cascades are the ecosystem responses of our title. The more we know about system operation, the more we will understand the true nature of the system. The complexity and extent of cascades in ecosystems caused by climate impact is due especially to process connections between the living components of...

The LTER Program and Climate

Both ecologists and climatologists recognize climate research as having a key role in long-term ecological research. Climate is one of the largest driving forces of ecological and hydrological processes at all of the LTER sites. Each LTER site is required to organize its 6-year research program around a central fundamental working hypothesis. A majority of the sites have climate as a central component of their research hypothesis. For example, one of the central questions of the H. J. Andrews...

Mortality Caused by Southern Pine Beetle

In the southern Appalachians, most pine species can be considered hosts for the southern pine beetle (SPB Dendroctonus frontalis), although historically the SPB has been associated primarily with yellow pine species (subgenus Diploxylon). Yellow pine species native to the southern Appalachians include pitch pine (Pinus rigida), shortleaf pine (P. echinata), Virginia pine (P. virginiana), and table mountain pine (P. pungens), as well as small populations of planted and naturalized loblolly pine...

Patterns of Maize Yield in the Corn Belt

Corn (Zea mays) is a crop central to the region's economy. Crop production in the NCR is an important resource as a national supply of food and by-products as well as a component of the nation's export marketing strategy. The role of weather as a cause of the variability of crop production at local, regional, and national scales is a subject of considerable concern. Variability in the annual yield of crops such as corn is a useful indicator of regional climate patterns because plant growth and...

Maurice J McHugh Douglas G Goodin

Interdecadal-scale climate variability must be considered when interpreting climatic trends at local, regional, or global scales. Significant amounts of variance are found at interdecadal timescales in many climate parameters of both direct data (e.g., precipitation and sea surface temperatures at specific locations) and indirect data through which the climate system operates (e.g., circulation indices such as the Pacific North American index PNA or the North Atlantic Oscillation index NAO )....

Reconstructing Historical Hurricanes

The frequency of hurricanes and the life span of trees are such that the long-term impacts of hurricanes on forests can be understood only at a scale of centuries. For much of the North Atlantic basin, the historical record provides evidence of past hurricanes over the last 300 to 500 years since European settlement. At the Harvard Forest we developed a method for interpreting this historical record using a combination of wind damage assessment and meteorological modeling. This...

Raymond C Smith William R Fraser Sharon E Stammerjohn

The Antarctic Peninsula, a relatively long, narrow extension of the Antarctic continent, defines a strong climatic gradient between the cold, dry continental regime to its south and the warm, moist maritime regime to its north. The potential for these contrasting climate regimes to shift in dominance from season to season and year to year creates a highly variable environment that is sensitive to climate perturbation. Consequently, long-term studies in the western Antarctic Peninsula WAP...

Multidecadal Drought Cycles in South Central New Mexico Patterns and Consequences

Moore Julio L. Betancourt James A. Parks Thomas W. Swetnam Robert R. Parmenter William T. Pockman Extreme, regional droughts are the most common form of disturbance in semiarid ecosystems typified by relatively slow recovery rates. Drought-driven impacts can include regionally synchronized insect outbreaks, wildfires, and tree mortality Swetnam and Betancourt 1990 , as well as disastrous failures of agriculture, silviculture, and livestock production Mainguet 1994 ....