Climate Variability

Konza Prairie Biological Station

The Konza Prairie Biological Station (KNZ), which lies in the Flint Hills (39 05' N, 96 35' W), is a 1.6-million-ha region spanning eastern Kansas from the Nebraska border to northeastern Oklahoma (figure 20.1). This region is the largest remaining tract of unbroken tallgrass prairie in North America (Samson and Knopf 1994) and falls in the more mesic eastern portion of the Central Plains grasslands. Konza's climate falls within well-recognized temperature and rainfall parameters for grassland...

A 200Year Perspective of Climate Variability and the Response of White Spruce in Interior Alaska

White Spruce Site Index

Glenn Patrick Juday Valerie Barber Scott Rupp John Zasada Martin Wilmking The two most important life functions that organisms carry out to persist in the environment are reproduction and growth. In this chapter we examine the role of climate and climate variability as controlling factors in the growth of one of the most important and productive of the North American boreal forest tree species, white spruce (Picea glauca Moench Voss). Because the relationship between climate and tree growth is...

Cross Site Analysis

The Pearson product moment correlation coefficients for the period 1957-1990 between the SOI values for a given month and the standardized temperature or precipitation anomalies do not show very high values (tables 6.1 and 6.2) because the data are inherently noisy. However, most of the values shown are statistically significant, partly because of the large number of pairs of observations (397-408) in the analyses. Another reason that the correlation coefficients are low is that all SOI values...

Mcmurdo Dry Valleys Hydrology

Climate and Hydrologic Variations and Implications for Lake and Stream Ecological Response in the McMurdo Dry Valleys, Antarctica Kathleen A. Welch W. Berry Lyons Diane M. McKnight Peter T. Doran Andrew G. Fountain Diana Wall Chris Jaros Thomas Nylen Clive Howard-Williams Because polar regions may amplify what would be considered small to moderate climate changes at lower latitudes, Weller (1998) proposed that the monitoring of high latitude regions should yield early evidence of global climate...

Andrew G Fountain W Berry Lyons

The view of climate change during the Pleistocene and the Holocene was very much different a mere decade ago. With the collection and detailed analyses of ice core records from both Greenland and Antarctica in the early and mid-1990s, respectively, the collective view of climate variability during this time period has changed dramatically. During the Pleistocene, at least as far back as 450,000 years b.p., abrupt and severe temperature fluctuations were a regular occurrence rather than the...

Introduction

Andrews Experimental Forest Map

Andrews (AND) Long-Term Ecological Research (LTER) site represents the temperate coniferous forest of the Pacific Northwest (PNW) of the United States. The general climate of the area is highly dynamic, displaying variability at a variety of timescales ranging from daily to millennial. AND, and its surrounding region, is therefore an ideal site for examining some of the guiding questions of climate variability and ecosystem response addressed by this volume (see chapter 1). A legacy...

Soil Geomorphic Evidence

Aspirin Platelet Aggregation Studies

Department of Agriculture began a study of soil-geomorphic relationships in a 400-square-mile (1024 km2) area surrounding Las Cruces (Gile et al. 1981). This project, termed the Desert Project, includes an area that overlaps the southern portion of the Jornada Experimental Range and Chihuahuan Desert Rangeland Research Center (figure 17.1). A major objective of the Desert Project was to map soils and geomorphic surfaces. In addition to Aridisol, Entisol, and Mollisol soil...

Douglas Schaefer

Variations in temperature and precipitation are both components of climate variability. Based on coral growth rates measured near Puerto Rico, the Caribbean was 2-3 C cooler during the Little Ice Age during the seventeenth century (Winter et al. 2000). At the millennial scale, temperature variations in tropical regions have been inferred to have substantial biological effects (such as speciation and extinction), but not at the multidecadal timescales considered here. My focus is on...

Summary of Climatic Variability and Ecosystem Response at the Jornada LTER Site

Amphioxus Diagram Labeled

Inferred climate variability at the Jornada LTER site, based on several types of evidence, is presented in figure 17.7. This graph is a working hypothesis of the biocli-matic changes during the last 20,000 years. The graph plots aridity, C4 grasslands, C3 woodlands, and C3 shrublands across 9 bioclimatic time intervals. Because vegetation is laterally diverse today, it was probably laterally diverse in the prehistoric past. Basin floor vegetation is commonly different than piedmont slope...

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...

Curtis Monger

Millennial Scale Climate Variability

The Jornada Long-Term Ecological Research (JRN LTER) program consists of studies superimposed on three research entities, the Jornada Experimental Range, the Chihuahuan Desert Rangeland Research Center, and the Desert Soil-Geomorphology project (figure 17.1). The JRN site is in the northern part of the Chihuahuan Desert and represents, for the LTER network, the desert shrubland and desert grassland ecosystems of the southwestern United States. Climate data at the Jornada site and surrounding...

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...

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 ....

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...

The Framework Questions

In planning this volume we decided to focus on a set of questions that emphasize the dynamic nature of climate variability and ecosystem response. An important consideration was the need for generalization. Within the LTER program, modeling is a fertile method for generalization. Whereas the material we deal with does not lend itself to cross-site modeling per se, we decided to ask questions that will lead to a modeling framework. With this in mind, we next discuss the questions that were used...

David Greenland Douglas G Goodin

The timescale structure of this book has served well to keep the attention of investigators focused on specific aspects of climate variability and ecosystem response. Indeed, judging by the responses received by the editors of this volume, when given a choice between focusing on one timescale or several timescales, the LTER community was far more comfortable dealing with just one scale. There are obvious reasons for this, not the least of which is that focusing on a single scale greatly...

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...

Return to Original State of Climate Variable and Ecosystem Response

We have asked, Does the climate event or episode and the ecosystem response return to an original state Many of the issues that fit appropriately in this section have been discussed in the previous section on Completion of Ecological Response concerning whether the ecosystem will return to its original state before the onset of the next climate event. We have not, however, addressed the manner of return. The nature of the return to the original state is important. In some cases, whether the...

Emerging Concepts and Principles of Climate Variability and Ecosystem Response

In this synthesis, the following recurrent principles begin to emerge Issues of time and space scale are pervasive throughout the field of climate variability and ecosystem response. It is not always possible to separate the effects on ecosystems of climate events and episodes of different timescales. At each LTER site climate events and episodes operate at different timescales. Consequently, these scales cannot be viewed in complete isolation. Some timescales, like that on which the ENSO...

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...

Bruce P Hayden Nils R Hayden

Ecological disturbances at Long-Term Ecological Research (LTER) sites are often the result of extreme meteorological events. Among the events of significance are tropical storms, including hurricanes, and extratropical cyclones. Extratropical storms are low-pressure systems of the middle and high latitudes with their attendant cold and warm fronts. These fronts are associated with strong, horizontal thermal gradients in surface temperatures, strong winds, and a vigorous jet stream aloft. These...

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...

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...

Douglas G Goodin Philip A Fay Maurice J McHugh

Climate is a fundamental driver of ecosystem structure and function (Prentice et al. 1992). Historically, North American grassland and forest biomes have fluctuated across the landscape in step with century- to millennial-scale climate variability (Axelrod 1985 Ritchie 1986). Climate variability of at decadal scale, such as the severe drought of the 1930s in the Central Plains of North America, caused major shifts in grassland plant community composition (Weaver 1954, 1968). However, on a...

Observed Temperature and Precipitation Variability at Konza Prairie

To examine how sunspot cycles, ENSO, NAO, and NPI may influence temperature and precipitation variability in a tallgrass prairie, we conducted period-spectrum analyses of a 108-year weather record (1891-1999) from Manhattan, Kansas, approximately 12 km north of Konza Prairie. Annual mean temperature and annual precipitation totals were tabulated and expressed as anomalies. Two spectral analyses were conducted, one filtered to emphasize interdecadal-scale periodicities, the second filtered to...

Overview of Book

Two nonmutually exclusive sets of concepts emerge from our studies. The first set of concepts is that initial and intermediate cascade elements may act as gateways, filters, and or catalysts to the climatic signal. Gateways can be open or closed that is, they can either permit the passage of material, energy, or information or not. Filters may pass a variable amount of material, energy, or information along through the cascade. This amount varies from all to none and includes all the...

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...

Conclusions

The relationships between climate variability and ecological response proposed here are speculative. The brevity of the available ANPP data precludes any direct comparison between climate variability and ecosystem response at any except the briefest time spans. Nevertheless, the results we present are important for two reasons. First, they provide insight into interpreting current patterns of ANPP. The tallgrass prairies (and grasslands in general), more so than other ecosystems (forest,...

Yearto Year Variability in Lake Heating and Fish Habitat

Subsurface Chlorophyll Maximum Layers

The course of changes in temperature and stratification has been described many times for temperate lakes in the spring. The water temperature immediately beneath the ice is 0 C and warms to 3-4 C in the depths of the lake. When the ice leaves the lake, wind action circulates the entire water column before the surface waters warm and stratification begins again. During the circulation period, the lake 0 200 400 600 800 1000 1200 1400 1600 Cross Section Distance (m) Figure 5.8 Schematic diagrams...

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...

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 )....

Species Specific Mortality

Mortality patterns during severe drought are often species specific (Tainter et al. 1984 Starkey et al. 1989 Clinton et al. 1993 Elliott and Swank 1994). For example, Clinton et al. (1993) found that the species most susceptible to drought-related mortality were members of the red oak group (particularly Quercus coccinea) and Carya spp. This pattern of mortality was observed across the southeastern region during the mid- to late 1980s (Starkey et al. 1989 Stringer et al. 1989 Oak et al. 1991)....

Raymond C Smith Douglas G Goodin

Elias argues (chapter 18, p. 370) that ecosystems are shaped by environmental changes that have occurred over thousands of years so that the century to millennial timescale is of particular significance because it is on these timescales that ecosystems form, break apart, and reform in new configurations. Within this context, the authors for the three chapters in part IV evaluate evidence for climate variability since the Last Glacial Maximum (LGM) to the present. They evaluate the biological...

Relationship to Framework Questions

The results discussed in this section clearly show the presence of climate variability at millennial timescales, although (as pointed out previously) they must be interpreted cautiously to avoid circular reasoning. Monger's results coincide with those of other paleoclimate analyses both in the U.S. Southwest (e.g., Hall and Scurlock 1991) and elsewhere (Gillespie et al. 1983). Elias's temperature reconstruction is consistent with Milankovitch forcing, but it differs in details from some other...

Introductory Overview

Television images of floods, hurricanes, tornadoes, snow and ice storms, and drought conditions are among the most vivid that leap into our minds when we think of short-term climatic events and their often obvious and direct ecosystem responses. The images are so striking that they tend to crowd out thoughts of longer term events. Yet, in many cases, even the longer term climatic events are often represented by the media as some manifestation of an individual severe weather event. The LTER...

Drought Impacts on Tree Growth and Mortality of Southern Appalachian Forests

Clinton James M. Vose Aaron R. Cooper The Coweeta LTER Program represents the eastern deciduous forests of the southern Appalachian Mountains in the United States. Coweeta Hydrologic Laboratory was established in 1934 and hence has a long record of climate measurement and vegetation response to both natural and human disturbance (Swank and Crossley 1988). The general climate of the area is classified as marine humid temperate because of high moisture and mild...

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...

Contributors

Full contact information of LTER members may be obtained from the LTER Network web site personnel directory at http lternet.edu people . Valerie Barber Bonanza Creek LTER University of Alaska Barton D. Clinton Coweeta LTER USDA Forest Service Julio L. Betancourt Sevilleta LTER USGS Tucson Woods Hole Oceanographic Institution Woods Hole Oceanographic Institution Fred Bierlmaier H. J. Andrews LTER USDA Forest Service Emery R. Boose Harvard Forest LTER Harvard University Scott Elias Niwot Ridge...

Coweeta Hydrologic Laboratory Climate

Mean annual precipitation at Coweeta Hydrologic Laboratory (latitude 35 14' N, longitude 83 26' W) varies from 1798 mm at the base climate station (686 m) to 2373 mm at the high-elevation Mooney Gap climate station (1364 m). Mean annual growing season precipitation, defined as May to October, is 782 mm at the 1930 1940 1950 1960 1970 1980 1990 2000 1930 1940 1950 1960 1970 1980 1990 2000 Figure 3.1 Precipitation from 1935 to 2001 (standard gauge 19) and streamflow from 1937 to 2001 (reference...

Preexisting Conditions

Whether a climate event or episode exceeds the threshold to produce an ecosystem response, as well as the degree of buffering to the climate signal the ecosystem may provide, both depend on preexisting conditions in the ecosystem and, sometimes, the climate system. Certainly, we see frequent examples of preexisting conditions themselves acting as gateways, filters, and even catalysts of ecosystem response to a climate driver. Many of the studies presented in this book contain examples of the...

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...

Late Holocene Environments

Late Holocene insect records from the Colorado Front Range show a progression from warmer-than-modern to cooler-than-modern summers, and back to warm again. At 3000 yr b.p., the calibrated TMAX estimate from Lake Isabelle was 1.8 C above the modern value. An assemblage just a few decades younger (and in fact, overlapping in radiocarbon age) from Longs Peak Inn yielded a calibrated TMAX estimate 0.3 C cooler than modern levels. Mean summer temperatures apparently remained near modern levels...

The Climate of the H J Andrews Experimental Forest

Located at latitude 44.2 N and longitude 122.2 W, the Andrews Forest is situated in the western Cascade Range of Oregon in the 6400-ha (15,800-acre) drainage basin of Lookout Creek, a tributary of the Blue River and the McKenzie River (figure 19.1). Elevation ranges from 410 m (1350 feet) to 1630 m (5340 feet). Broadly representative of the rugged mountainous landscape of the Pacific Northwest (PNW), the Andrews Forest contains excellent examples of the region's conifer forests and associated...

Yearto Year Climate Variability and Plant Phenology Physiology and Ecosystem Exchange

The date of the snowmelt near the LTER greenhouse plots varied by 26 days over the last 7 years the earliest date was 13 May in 1995 and the latest was 9 June in 2000 (table 5.2). A longer record from nearby Imnavait Creek had a range of 30 10 days (sd) over the past 17 years (Kane et al. 2000). The timing of snowmelt has a significant effect on soil temperatures and thickness of the active or thawed layer (figure 5.3). On experimental plots where snow was removed two to three weeks before the...

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...

Analysis of Climate Patterns Spatial Organization

Trends and patterns of climate in the NCR were examined and linked to the ecological regions classified by Bailey (1996). Bailey (1996) used a hierarchy of scales to define ecoregions, including (from larger to smaller scales) domain, division, Figure 4.2 Bailey ecoregion classification. The lighter area in each map shows the ecore-gion represented by the KBS LTER. province, and section. The Bailey system of classification was used in this analysis because this hierarchy is primarily based on...

Within Season Variability in Stream Flow and Lake Ecosystems

Recent studies have shown that the mixing and stratification of Toolik Lake may be greatly changed when one or more high-discharge spates in the inlet stream occur during the summer this has important consequences for algal primary productivity. The incoming stream water may be differentiated from the lake water through small differences in temperature and conductivity. One example of the impact of a spate occurred in mid-July 1999. Prior to the spate (figure 5.8A), the subbasins of Toolik Lake...

Douglas G Goodin

Timescale is the organizing framework of this volume. In various sections, we consider the effects of climate variability on ecosystems at timescales ranging from weeks or months to centuries. In part III, we turn our attention to interdecadal-scale events. The timescales we consider are not absolutely defined, but for our purposes we define the interdecadal scale to encompass effects occurring with recurring cycles generally ranging from 10 to 50 years. A recurring theme in many of the...

Late Pleistocene History of the Front Range Region

The Wisconsin Glaciation is called the Pinedale Glaciation in the Rocky Mountain region, after terminal moraines near the town of Pinedale, Wyoming. The Pinedale Glaciation began about 110,000 yr b.p. and included at least two major ice advances and retreats in most regions of the Rocky Mountains. The history of glaciation is not as well worked out for the Colorado Front Range region as it is for regions in the Central and Northern Rockies. For example, geologists have documented three separate...

Late Pinedale Environments of the Front Range

Paleoclimatic reconstructions for the Rocky Mountain region indicate that the Colorado Front Range received less moisture than ranges to the north (in the Yellow stone region) and the south (the San Juan Mountains). Consequently, the mountain glaciers of the Front Range region were small, and glaciers from most drainages did not coalesce to form larger glaciers or ice sheets. Paleoclimatic reconstructions based on fossil insect assemblages from the Front Range region (Elias 1986, 1996b)...

Short Term Variability in a Long Term Context

Another aspect of short-term climatic variability and ecosystem response, partially and implicitly treated above, is the need to place these items into a longer term perspective. Boose points out the need for paleohurricane record studies as the next step in our understanding of the forest response to such storms. The hurricane study also shows how important preexisting conditions are, especially with regard to the passage of previous hurricanes and to human land-use patterns that may have been...

Physical Features

Coweeta Hydrologic Laboratory is located in the Nantahala Range of the southern Appalachian Mountains approximately 200 km north of Atlanta, Georgia, and 119 km southwest of Asheville, North Carolina. The laboratory comprises two adjacent, east-facing, bowl-shaped basins. The Coweeta Basin encompasses 1626 ha and has been the primary site for watershed experimentation, whereas the 559-ha Dryman Fork Basin has been largely held in reserve for future studies. More than 50 km of streams drain the...

Biological Features

Forests at Coweeta were traditionally classified as belonging to the oak-chestnut association. However, with the loss of chestnut (Castanea dentata) as the dominant canopy species, the area is more appropriately included in the oak-hickory or Appalachian oak association. The plant communities in the Coweeta Basin are distributed in a reasonably predictable mosaic over the highly varied topography in relation to complex moisture and elevational gradients (Bolstad et al. 1998). Generally,...

Effects of Drought on Overstory Tree Species Growth Rates

Coweeta Hydrologic Laboratory

Observed values of species-specific basal area growth rates vary considerably at Coweeta Hydrologic Laboratory (figure 3.2). Because of the wide range in tree diameters, data are expressed on a relativized basis, annual basal area growth (cm2) Figure 3.2 The relative basal area increment (cm2tree growth per cm tree diameter) of two selected species at Coweeta Hydrologic Laboratory near Otto, North Carolina. Each connected line represents a single tree over the measurement period. The deciduous...

Short and longterm responses in the ecosystem

The chapters about hurricanes and droughts in this section demonstrate that short-term climatic events may have short- and long-term responses in the ecosystem. Both the short- and long-term responses are important. The short-term responses have noteworthy economic influences in the agricultural ecosystem. One could argue that the ecosystems containing species with short life spans such as grasslands are able to respond and recover from a short-term climatic disturbance more quickly than those...

Ecological Scaling of Climate Variables

To scale the climate data to ecological regions, each of the ecological categories defined by Bailey (1996) (section, province, division, and domain) was associated with each of the 1055 counties in the NCR. Table 4.2 shows the data points, located at the county centers, in the database of daily weather and annual corn yields in the Bailey ecoregion classification scheme over the 20-year period. This analysis focuses on those ecoregions associated with the LTER in southwest Michigan (Kala-mazoo...

Douglas G Goodin Raymond C Smith

At longer timescales, the interaction among climate, ecosystems, and the abiotic components of the environment become increasingly important. These relationships are apparent in the three chapters in part IV. Fountain and Lyons (chapter 16), examining the McMurdo Dry Valleys (MCM) ecosystem in Antarctic, provide an excellent example of a case where past climatic variations truly dictate current ecosystem status. The relatively large climate variations at MCM have concentrated nutrients that...

Long Term Climate Variability and Lake Water Chemistry

The 25-year record of water chemistry at the Arctic LTER site has documented a doubling of the average alkalinity or acid neutralizing capacity of Toolik Lake (figure 5.14). This change in alkalinity is balanced primarily by changes in calcium and Figure 5.14 The annual July average alkalinity (1 m depth) in Toolik Lake, Alaska. Figure 5.14 The annual July average alkalinity (1 m depth) in Toolik Lake, Alaska. magnesium. There are no corresponding changes in the chemistry or amount of the...

Discussion

Present knowledge of climate variability and ecosystem response at a range of timescales provides a variety of answers to some of the guiding questions of this volume. New questions also emerge. Sometimes, it is difficult to specify the most important timescale at which causes and consequences are operating. For example, is forest fire occurrence at the Andrews LTER site more related to a seasonal scale or to a decadal to century scale What is the interaction, if any, or relative importance...

An Introduction to Climate Variability and Ecosystem Response

Goodin Raymond C. Smith The regularities of our planet's climate determine a large part of the form and function of Earth's ecosystems. The frequently nonlinear operation of the atmosphere gives rise to a rich complexity of variability superimposed on the fundamental regularities. A traditional definition of climate is the long-term state of the atmosphere encompassing the aggregate effect of weather phenomena the extremes as well as the mean values (Barry and Chorley...

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...

Raymond C Smith

The El Nino-Southern Oscillation (ENSO) is a coupled ocean-atmosphere phenomena that has a worldwide impact on climate. An aperiodic phenomena that reoccurs every 2 to 7 years, the ENSO is second only to seasonal variability in driving worldwide weather patterns. As Greenland notes in chapter 6, the term quasi-quintennial is chosen to recognize that climatic events other than ENSO-related events might occur at this timescale, although it is widely recognized that ENSO contributes the lion's...

Limits of Climate Variability and Ecosystem Response

Few authors in this volume attempted to explicitly address the question of whether the climate event or episode and the ecosystem response had identifiable upper and lower limits. This is because it is important to study climate events that cause severe ecosystem change so the limits of the ecosystem response are clearly bounded. Not all of the subject matter of our chapters meets this criterion. In retrospect, the reason for the lack of consideration of limits is that the subject is partially...

Study Regions New England

The six New England states plus adjoining New York City and Long Island comprise a region of about 175,000 km2. Topographic relief varies from coastal plains to mountains of 1000-m elevation (maximum 1900 m) to the west and north. The climate is temperate, with significant variation (especially in temperature) resulting from differences in elevation, latitude, and distance from the ocean. Major life zones include Northern Hardwoods-Spruce-Fir (northern New England), Transition Hardwoods...

The General Nature of ENSO and Its Climatic Effects

ENSO is the acronym for El Ni o-Southern Oscillation despite the fact that the Southern Oscillation is composed of swings between El Ni o and the almost opposite La Ni a events. El Ni o is a warming of the Pacific Ocean between South America and the international date line, centered on the equator, and typically extending several degrees of latitude to either side of the equator. La Ni a exists when cooler than usual ocean temperatures occur in the same area (Trenberth 1997 Kelly Redmond, pers....

Previous Work at LTER Sites

Within the LTER network, there has been ongoing interest in the ENSO-related phenomena. A workshop, held in 1993, concentrated on the effect of El Ni os and La Ni as at LTER sites (Greenland 1994a). Since the LTER network is spread across the North American and Antarctic continents (figure 1.1), it is natural that ENSO climatic signals should be stronger and more marked for some LTER sites than others. The line of LTER sites, from New Mexico through Colorado to the Pacific Northwest and into...

Century to Millennial Scale

The absence of direct meteorological observations for most time periods and geographic areas at the century to millennial scale forces investigators to use proxy evidence from which to infer information concerning the variability of climate. At this scale, therefore, the ecological response is being used to provide information concerning the climate. We thus admit, in this section, to engaging to a certain degree in circular argument while discussing the inferred climate variability (as a...

Short Term Climate Events

2 Hurricane Impacts in New England and Puerto Rico 25 3 Drought Impacts on Tree Growth and Mortality of Southern Appalachian Forests 43 Brian D. Kloeppel, Barton D. Clinton, James M. Vose, and Aaron R. Cooper 4 Climate Variability in the North Central Region Characterizing Drought Severity Patterns 56 5 Climate Forcing at the Arctic LTER Site 74 John E. Hobbie, Neil Bettez, Linda A. Deegan, James A. Laundre, Sally Maclntyre, Steven Oberbauer, W. John O'Brien, Gaius Shaver, and Karie Slavik...

Mortality Caused by Pathogens

The commonly occurring shoestring root rot fungus (Armillaria mellea) has been associated with oak mortality species (Wargo 1977) and has been implicated as the primary causal agent (D. J. Lodge, pers. comm.) in mortality observed in the southeast during the 1980s. Nonetheless, there is considerable speculation about whether primary or secondary causes of mortality can be assigned to a single vector (Wargo 1977). The effectiveness of the fungus in causing or contributing to mortality is related...

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...

Patterns of Drought During the Growing Season May August

To examine the annual patterns of HPR during the 20-year period of record, the average HPR was computed for May, June, July, and August, based on all 1055 locations in the climate database. These months were selected because they encompass months when plant stress will have a significant impact on plant productivity, particularly in agricultural crops. The monthly patterns of HPR, computed for May-August in the North Central Region, are provided in figure 4.5. In May, relatively high HPR values...

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...

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...

Interactions with Insects and Disease

The dogwood example raises an interesting question Is an individual tree's susceptibility to drought-related mortality determined, at least in part, by the local conditions under which the individual developed (Waring 1987) Gram and Sork (2001) have shown that under sufficient selection pressure, even within a localized area, some species can develop distinct genotypes that are associated with fine-scale mi-crotopographic variation or with a specific set of resource availabilities. For example,...

Spatial Characteristics of Drought

To characterize the spatial distribution of drought throughout the North Central Region, the HPR was associated with the geographic center of each county. ArcView GIS software (ESRI 1999) was used to interpolate a surface of HPR based on the spatial association between points using the inverse distance weighting (IDW) algorithm and a spatial moving average by associating 12 nearest neighbors to interpolate values of HPR between the 1055 points. Surface grid maps of HPR were developed based on...

Regional Crop Production Patterns

When drought begins, the agricultural sector is usually the first to be affected because of its dependence on stored soil water, which is rapidly depleted during extended dry periods. Corn is particularly sensitive to summer droughts because of its high physiological requirements for moisture during the growing phase. In the North Central Region, planting generally occurs when the land is dry enough to support planting machinery and when the soil warms to about 10 C, which is usually during...

Timing of Short Term Climatic Events

The chapters in this section support the hypothesis that the timing of short-term events is important in partially determining the kind and degree of ecosystem re sponse that might occur. At the Arctic LTER site, early snow melt is an issue. Hob-bie et al. report that every few years soil warming, caused by early snow melt or by warm summers, results in both a synchronous flowering of arctic cotton and an increase in leaf area that occurs across the entire area of northern Alaska. The corn...

Climate Variability and Ecosystem Response Synthesis

Goodin Raymond C. Smith Frederick J. Swanson At the outset we identified the theme of this book as how ecosystems respond to climate variability. We have examined this theme at a variety of LTER sites and at a variety of timescales. The subject matter of the book was also to be focused on a series of framework questions. We noted that the theme of climate variability and ecosystem response is inherently deterministic and implicitly carries with it the notion of...

Future Climate Variability and Ecosystem Response

There continues to be concern about the possible effects on global climate change related to increased greenhouse gases in the atmosphere. If such climate change does occur, it is difficult to conceive of a potentially more important example of climate variability and ecosystem response. Future climate change will have complex, cascading, and, in some cases, detrimental effects on the ecosystems of the PNW. Global General Circulation Models (GCMs) of the atmosphere and ocean are being used to...

Multidecadal Timescale

Multidecadal changes for the Pacific Northwest (PNW) are related to the PDO. Taylor and Southards (1997) noted a cool, wet period from 1896 to 1914, a warm and dry period from 1915 to 1946, a cool and wet period from 1947 to 1975, and a warm and dry period from 1976 to 1994. Mantua et al. (1997) have shown these periods to be related to changes in the synoptic-scale climate indices that have reversal times during the period 1900-1996 in 1925, 1947, and 1977. The climate regime shifts related to...

Mid Holocene Environments

From 7800 to 3000 yr b.p., insect fossil assemblages from La Poudre Pass and Lake Isabelle show a gradual summer cooling trend. The 7800 yr b.p. assemblage from Lake Isabelle yielded a calibrated MCR estimate of mean July temperature 2.1 C warmer than modern temperatures. The 5250 yr b.p. assemblage from Sky Pond yielded a mean July temperature estimate 0.4 C warmer than modern levels. This is the oldest Holocene assemblage that yielded a TMAX range that dipped near the Calibrated estimates...

Early Holocene Environments

During the Holocene, the Colorado Front Range experienced a series of climatic fluctuations. Insect assemblages from several sites are indicative of warmer-than-present summer temperatures and colder-than-present winter temperatures. The earliest Holocene records in the insect fossil study transect come from Sky Pond and La Poudre Pass. Sky Pond is an alpine pond in Rocky Mountain National Park. A fossil beetle assemblage from 10,000 yr b.p. yielded a calibrated MCR estimate of mean July...

Paleotemperature Estimates from the MCR Study

The earliest indications of climatic amelioration were found at the Mary Jane site, where peat layers were deposited after the retreat of late Pinedale ice. Short and Elias (1987) reported on pollen and insect remains from peat layers ranging in age from 13,740 to 12,350 yr b.p. Fossil evidence from layers dated 13,740-12,700 yr b.p. suggest open ground environments with flora and insect fauna associated with alpine tundra habitats. Elias (1996b) performed an MCR reconstruction of mean July and...

The MCR Technique

The MCR technique is based on the assumption that the present climatic tolerance range of a species can be applied to its Quaternary fossil record, so that fossil occurrences of a given species imply a paleoclimate that was within the same tolerance range. MCR studies focus on predators and scavengers, because these groups are assumed to show the most rapid response to climate change. The predators are nearly all generalists that prey on a wide variety of small arthropods. Plant-feeding groups...

Yearto Year Climate Variability and Plant Flowering

Shaver has counted the average number of flowers of the cotton grass (Eriophorum vaginatum) at 38 sites along the highway from Fairbanks to Prudhoe Bay (Shaver 1986b) (figure 5.10). The variability from year to year was amazing the average ranged from 1 to 46 (figure 5.11). Even more remarkable was the synchrony of flowering along the entire transect that covered 650 km. This is evident in figure 5.12, where the mean inflorescence for a year is compared, for each...

Yearto Year Climate Variability and Grayling Growth

As seen in figure 5.6, there is a large amount of annual variability in streamflow and temperature in the Kuparuk River as a direct result of summer precipitation and air temperatures. The growth of the arctic grayling, the only species of fish in this river and in a nearby smaller stream called Oksrukuyik Creek, is strongly affected by the flow rate and by the temperature as a result of its life cycle. The arctic grayling (Thymallus arcticus) is found in North America from Minnesota north to...

Dayto Day Variability in Solar Radiation and Photosynthesis

The most important short-term control of photosynthesis of tundra plants at Toolik Lake is the amount of solar radiation. This is illustrated in figure 5.7 by the process-based model of net ecosystem production (NEP) developed by Williams et al. (2000). The model, the solid line in the top panel of this figure, is driven by the hourly amount of photosynthetically active radiation (PAR), by hourly air temper Figure 5.7 The top panel is the net ecosystem production (NEP) for acidic tundra at...

Historical Hurricanes

A total of 143 hurricanes over the period 1508-1997 were investigated, including all hurricanes since 1851 that passed within 500 km of Puerto Rico according to HURDAT and all earlier hurricanes that impacted the island according to Salivia (1950), Millas (1968), and other scholars. Of these, a total of 85 hurricanes for which we found historical evidence of wind damage (F0+) in Puerto Rico were selected for detailed analysis. A wide range of Puerto Rican newspapers have provided direct...

Field Studies of Ecosystem Response

Ecosystem response to individual hurricanes can be measured directly through field studies of actual or simulated wind damage. Research at the Harvard Forest has focused on two areas (1) long-term studies of forest recovery in central New England after the 1938 hurricane, and (2) intensive studies of a simulated hurricane blowdown created at the Harvard Forest in October 1990. The 1938 hurricane, a category 3 storm at landfall, caused widespread F2 damage across much of central New England....

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...

The Theme of the Book

Millennial-scale (1000-year) climate variability has driven large changes of vegetation and fauna at almost all of the Long-Term Ecological Research (LTER) sites. Decadal climate variability at some sites has seen dramatic changes in fish catches and has altered tree species composition. During the first two decades of study, LTER sites have been affected by two super El Ni o events and several more normal El Ni os and La Ni as. Major droughts have affected species diversity and killed some...