Historical Perspective On Ecosystem Engineering

Natalie Buchman, Kim Cuddington, and John Lambrinos

2.1 - INTRODUCTION

Ecologists have been aware that animals and plants modify the physical environment for at least 150 years, even though the term ecosystem engineer was not coined until 1994 (Jones et al. 1994). As we have argued elsewhere (Beisner and Cuddington 2005), awareness of the historical development of any ecological topic can lead to deeper understanding and more rapid scientific progress. In this spirit, we outline some of the major areas of research on ecosystem engineering that have been important historically, focusing on early studies in the late 1800s to the more recent contributions of the early 1990s (Figure 2.1).

Before we begin, it is worth noting that there is some controversy about the appropriate use of the term ecosystem engineering. Jones et al. (1994) originally defined an ecosystem engineer as an organism that creates, modifies, or maintains a habitat by altering the availability of resources to other organisms. More recent definitions emphasize the alteration of the physical environment by these species (Jones et al. 1997, Guttierez and Jones 2006). Some authors have argued that these definitions include all organisms, and claim that the term should be restricted to those species that have large impacts on the environment and

Ecosystem Engineers © 2007 Elsevier, Inc.

All rights reserved.

fO 05

Morgan (1868) beavers affect stream ecosystems

Darwin (1881) earthworms on soil processes

Shaler (1892) plants and animals affect soil processes

1860

1880

Clements (1916) plant succession

Jones et al. (1994) defined "ecosystem engineering"

Varga (1928) phytotomata

Taylor (1935) burrowing animals as important agents in soil composition

Dayton (1972) foundation species

1900

1920

1940

1960

1980

n /mor\ ju ..j. Streve (1931) nurse plants and Branner (1986) mound building r plant facilitation insects affect tropical

Lad (1961) coral sediments reefs create habitats

Davison (1891) bioturbation in aquatic sediments

2000

Vitousek (1986, 1990) invasive species modify the environment

T1 M

tn N

x tn

FIGURE 2.1 Timeline of selected important studies related to the ecosystem engineering concept.

associated communities (Reichman and Seabloom 2000a). In this review, we focus on studies of organisms that alter the physical environment without attempting to limit our survey to species that have large effects, however defined. In practice, most published literature will emphasize those species thought to have important effects, and our review will certainly share this bias.

There has been a steady stream of literature on species-specific modification of the physical environment since the late 1800s. For example, Morgan (1868) claimed that beaver impact the hydrology and geomor-phology of stream ecosystems. Soon after, Lyell (1873) noted that organisms could locally and superficially alter geomorphology. Darwin described the actions of earthworms on soil and sediment processes (Darwin 1881), while Shaler (1882) reviewed the effects of many other species on soils. The observation that organisms interact with each other indirectly through physical habitat modification has also played an important, although often implicit, role in the development of key ecological concepts such as succession and facilitation (see Cowles 1911, and Bertness and Callaway 1994).

The number of studies that are encompassed in this topic is, however, vast, and our review should be considered selective rather than exhaustive. Following major divisions in the literature, we have organized these studies into four categories: soil processes, plant succession, microclimate modification, and habitat creation. We note that this topic categorization helped early scientists to draw analogies between seemingly disparate organisms. For example, Elton (1927) suggests that land crabs on coral islands played a similar role to that of earthworms in continental regions. This type of analogy seems to us to be a precursor of the more overarching category of ecosystem engineer.

2.2 - SOIL AND SEDIMENT PROCESSES

The study of soil processes is an area where the impact of ecosystem engineering has been, and continues to be, widely recognized. Lavelle (2002) recently argued ecosystem engineering is more important for the regulation of soil processes than trophic interactions. Historically, many studies in the past 150 years have addressed the large effect of animals and plants on soil and sediment processes at local scales. For example, in 1892, Shaler provided an early overview of the impact of microorganisms, animals, and plants on soil processes. In addition, early ecologists recognized that these soil engineers, by altering the composition and structure of soils, may also affect other organisms that occupy the soils. Moreover, some early workers were also aware of the functional analogies of different organisms in different soil and sediment environments. Most early investigators, however, focused on particular groups of organisms and their effects soil processes. We provide an overview of this area of research using the most commonly studied groups such as earthworms, mound-building insects, burrowing rodents, benthic fauna, and terrestrial plants.

Darwin's (1881) famous book described the enormous effect that earthworms have on physical soil structure through their burrowing, mixing, and casting activities. It has been known for some time that earthworms grind soil particles in their digestive tract and so cause increased aeration of soil (Shaler 1892). In a later work, Hopp (1946) observed that the action of casting aggregates soil particles and allows soil to drain readily, which aids in the prevention of erosion. Since then, many ecologists have found that the addition of earthworms to soil causes increased growth and vitality of vegetation because of improved soil structure and moisture penetration (Hopp and Slater 1948, van Rhee 1965, Stockdill 1966). The mixing and incorporation of organic matter in soils by earthworms also have a long history of study. Early researchers observed earthworms pulling leaves and other organic matter into their burrows, thereby introducing organic matter into lower levels of the soil (Shaler 1892). Later studies found that earthworm casts increase microbial activity (Barley and Jennings 1959, Parle 1963, Jeanson 1960), which causes dead material to be incorporated into the soil surface at a much faster rate (Stockdill 1966). As a result, nitrogen and phosphorus in soils increase with activities of earthworms (Lunt and Jacobson 1944, Barley and Jennings 1959, Aldag and Graff 1975, Sharpley and Syers 1976).

Early ecologists realized that the action of mound-building insects in tropical regions was analogous to the effects of earthworms in temperate climates (Branner 1896). Many species of ants and termites profoundly modify physical soil properties by selecting and redistributing soil particles during the construction of nests, mounds, and foraging galleries. These activities have a direct influence on soil characteristics such as bulk density, turnover rates, profile development, and water infiltration. These physical changes can secondarily influence a number of important soil processes such as redox and nutrient cycling (Lobry de Bruyn and Conacher 1990).

Early studies catalogued some of these effects. Shaler (1892) claimed that in some areas, ants are so numerous that they transfer 1/5 inch of new soil to the surface each year. In early work in the tropics, Branner (1896) observed ant and termite mounds covering large areas and consisting of many tons of soil. He also noted that mound-building ants brought up soil from lower levels to the surface, which causes large soil particles to break up and also promotes the incorporation of organic material. Bell (1883) argued that organic debris such as leaves and dead plant tissue would not be as readily incorporated into soil if it were not for the burrowing action of insects. It was also observed that ants drag their food and leaves of plants into underground channels, which causes increases in organic matter content (Branner 1896). Later studies, in various systems (Baxter and Hole 1967, Wiken et al. 1976, Mandel and Sorenson 1982, Levan and Stone 1983, Carlson and Whitford 1991), found that ant mounds have increased levels of inorganic and organic material, lowered bulk density, and altered soil structure as compared to surrounding nonmound areas. Finally, recent work suggests that the action of mound building, subterranean gallery construction, and redistribution of soil particles by ants also increases the water content, pH (Rogers and Lavigne 1974, Briese 1982, Beattie and Culver 1983), and the rate of colonization by microorganisms because of the increase in decomposable material and access due to the underground tunnels (Czerwinski et al. 1971, Lockaby and Adams 1985).

In addition to these direct effects on soil processes, some researchers concluded that vegetation patterns are influenced by ant (Czerwinski et al. 1971, King 1977, Beattie and Culver 1983) and termite mounds (Glover et al. 1965). Salem and Hole (1968) found that ant activities of depositing subsoil on the surface and excavating chambers caused a reduction in bulk density and an increase in available nutrients to plants. Black seed harvester ants (Messor andrei) create large nest mounds of excavated soil. In California grasslands these mounds support plant assemblages that are distinct from nonmound vegetation. Hobbs (1985) hypothesized that selective seed harvesting by M. andrei caused the unique mound vegetation. Brown and Human (1997), however, used ant exclusions to demonstrate that granivory had little influence on vegetation dynamics. Instead, physical differences between mound and non-mound patches such as soil temperature seem to be driving vegetation patterns. Studies such as this that explicitly test alternative mechanisms have been rare. Most studies examining the influence of ant and termites on vegetation or ecosystem traits have been correlative. In general, however, research into the mechanisms by which soil invertebrates act as ecosystem engineers is more advanced than any other area (see Jouquet et al. 2006 for a recent review).

Burrowing rodents have figured prominently in the recent literature on ecosystem engineering (e.g., Reichman and Seabloom 2002a, 2002b). Early researchers also observed that burrowing rodents, like soil invertebrates, cause a mixing of the soils and the addition of vegetation and other organic compounds into the burrows (Shaler 1891, Green and

Reynold 1932). Taylor and McGinnie (1928) found that the burrowing action of the kangaroo rats, pocket gophers, ground squirrels, and prairie dogs has an enormous impact on soil properties and vegetation growth. Taylor (1935) observed that the sublayers of soil are brought to the surface by this action, which increases the fertility of soils. Early work also illustrated that digging of burrows increases water infiltration and retention (Green and Reynold 1932, Taylor 1935), which could have a positive effect on plant growth or influence community structure (Reynolds 1958), and also affect soil erosion and stability (Arthur et al. 1929, Meadows 1991). Early and more recent analysis of soils worked over by rodents shows an increase in calcium, magnesium, bicarbonate, nitrate, and phosphorus (Green and Reynold 1932) and increased microbial activity (Meadows 1991).

Analogous studies in aquatic systems also have a long history. Davison (1891) was one of the first to investigate the bioturbation of aquatic sediments in a study of a polychaete feeding on tidal flats. Miller (1961) suggested that 2-3 cm of marsh sediment is reworked due to the deposit feeding action of fiddler crabs. Rhoads and Young (1970) found that deposit feeders affect grain size, increase water content at sediment surface, change sediment stability, and affect species diversity in aquatic sediments. Both early and later studies demonstrated that the production of fecal pellets and burrowing action by various aquatic species have large effects on aquatic sediments (Moore 1931; Brinkman 1932; Rhoads 1963, 1967; McMaster 1967; Rhoads and Young 1970; Brenchley 1981; Posey et al. 1991). With few exceptions (e.g., Aller 1982), the burrowing action of macrofauna increases organic matter, solute transport, oxygen content, sulphate and nitrate reduction, and metabolic activity in aquatic sediments (e.g., Anderson and Kristersen 1991). For example, Bertness (1985, 1991) found that in marsh habitats, the burrowing of fiddler crabs caused an increase in soil drainage, soil oxidation-reduction potential, decomposition of below-ground plant debris, and cord grass production. Reichelt (1991) found that the construction of burrows by meio-fauna redistributes sediment, which affects the physical, chemical, and biological properties of the system. Other studies catalogue the effects of various species on sediment composition, such as herbivorous snails (Bertness 1984), atyid shrimp (Brenchley 1981, Pringle et al. 1993), crayfish (Soluk and Craig 1990, Wallace et al. 1981, Pringle and Blake 1994), and fish (Flecker 1996).

Of course, plant species also have dramatic effects on soils and sediments. As early as 1892, Shaler described the profound effect plant roots have on soils. They cause movement of soil, breakup of rocks, addition of organic compounds, and creation of channels from decaying roots. He also noted that the overturning of trees will bring nutrient-rich subsoil to the surface. Other early studies reported that forest soils had increased air, water, and organic matter content compared to bare unforested regions (Ramann 1897, Hoppe 1898, Albert 1912, Engler 1919), and various mechanisms mediated by root growth were invoked to explain such differences. The accumulation of dead leaves as litter also changes the microenvironment of soils by altering surface structure, drainage, and heat and gas exchange (Facelli and Pickett 1991). Various types of vegetation employ similar engineering mechanisms that affect the pattern of soil properties in many different environments (oak tree in heath land: Muller 1887; orange trees in Florida orchards: Jamison 1942; desert shrubs: Fireman and Hayward 1952, Muller and Muller 1956).

This disparate literature describing how organisms affect soil processes at the local scale has historically had only a minor influence on studies examining large-scale geomorphological processes. Lyell's (1873) early observations and Charles Darwin's (1842) theory of coral atoll formation notwithstanding, for most of its early history the discipline of geomorphology focused mainly on understanding how physical processes influence the evolution of landforms (Chorley and Beckinsale 1991). In the last several decades, however, researchers have increasingly recognized the important influence that organisms can have on landform development (Viles 1988, Butler 1988, Stallins 2006). The incorporation of biological feedbacks into physical process models has been especially useful in understanding highly dynamic processes operating over relatively short time scales, such as coastal erosion and desertification (Costanza et al. 1990, von Hardenberg et al. 2001)

2.3 « SUCCESSION

The investigation of successional processes has been tightly related to the studies of organisms' effects on soil processes. Cowles (1911) provided a detailed overview of early succession studies. One of the first observations of this process was made by William King in Philosophical Transactions (1685), in which he described bog formation due to the production of peat. Biberg (1749) initiated the idea that moss and lichen establishment on unoccupied rocks causes the production of soil, and subsequently the establishment of vegetation. Early appreciation of engineering mechanisms is also found in early successional studies conducted in various climates and habitats (islands: Reissek 1856; sand dunes: Warming 1891; Rhone Delta: Flechault and Combry 1894; German hearth: Graebner 1895).

Beginning with von Humboldt's (1805) pioneering work on plant geography, the concept of abiotic determinism had a strong influence on the development of the concept of succession. Steenstrup (1842) was one of the first to argue that vegetation changes preserved in the fossil record reflected changes in European climate since the last glacial period. In early succession models climate was the primary mechanism regulating climax community composition, either as integrated units (Clements 1916) or as individually reacting species (Gleason 1939). These early succession models did implicitly assume that species-environment interactions partly drove successional changes towards the eventual climax community. Empirical studies documented the stabilization of sand dunes by pioneer plants allowing the colonization of other vegetation (Cowles 1889, Olson 1958), and the ultimate impact of microclimate modification (see following text) was noted in the action of nurse plants in providing shade for the colonization and growth of vegetation (Streve 1931, Niering et al. 1963).

Early examples of the dynamic interaction between the biotic and abiotic environments greatly influenced the development of the ecosystem concept. In introducing the term, Tansley (1935) argued that plant communities were in dynamic equilibrium with the abiotic environment such that "the biome is determined by climate and soil and in its turn reacts, sometimes and to some extent on climate, always on soil." In contrast to the early conceptual models of succession, later models described successional changes explicitly as the outcome of direct species interactions. These models, however, focused on the ultimate population impacts of the species interactions rather than on the underlying mechanisms (e.g., Horn 1974, Connell and Slatyer 1977). Recently, it has been found that invasive plant species can have a large impact on community change (Vitousek 1986, 1990).

2.4- MICROCLIMATE MODIFICATION, FACILITATION, AND INHIBITION

The influence of plants on the local microclimate was first noted by Jozef Paczoski in the mid 1800s (Maycock 1967). The alteration of local conditions can either facilitate or inhibit the growth of new plants. Various studies have described the positive effects that plants can have on the environment and the colonization of other species. In an early study, Streve (1931) found that there was a greater amount of herbaceous plants, perennials, and seedlings under bushes and desert trees compared to the surrounding barren areas because of the increased shading and moisture. Ellison (1949) observed that seedling establishment and survival in a depleted alpine range are higher under plant canopies due to less extreme temperature and increased soil moisture. Chapin et al. (1979) found that Eriophorum vaginatum dominate the Alaskan tundra because of its tussock growth form, which increases soil temperature and moisture via insulation. More recently, it has been suggested that nurse plants in desert habitats can reduce surface temperatures due to increased shading and enhance the survival and distribution of seedlings (Steenberg and Lowe 1969, Turner et al. 1969, Franco and Nobel 1989). These microhabitats also affect other species in the community. On the forest floor the microenvironment that is created due to shading has profound effects on the microbial community (Williams and Gray 1974).

Plant litter can also affect the microclimate of an area by changing the physical and chemical environment (Facelli and Pickett 1991). McKinney (1929) found that litter aids in the prevention of soil freezing by providing insulation. Litter also intercepts sunlight, reduces thermal amplitude of soils, and can affect the germination and growth of seeds (Bliss and Smith 1985, Fowler and Knauer 1986, Facelli and Pickett 1991). It also can reduce evaporation (Hollard and Coleman 1987, Facelli and Pickett 1991). Similarly, peat also insulates soils, affecting microclimate and increasing soil respiration (Petrone et al. 2001).

Of course, not all habitat modification is beneficial. The inhibition of new vegetation growth by previously established vegetation has long been an area of research and, under some definitions, can be considered ecosystem engineering. Early studies on bogs reported that plant roots give off excretions causing bog water and soil to become toxic to other plant growth (Livingston et al. 1905, Schreiner and Reed 1907, Dachnowski 1908, Tansley 1949). Salisbury (1922) noticed that in woodlands in England the soil was becoming more acidic due to the change in vegetation. The acidification of soils by plants can have a negative impact on the growth of new vegetation (Grubb et al. 1969, Nihlgard 1972). Muller (1953) reported that the toxins produced by desert shrubs significantly impacted the distribution and abundance of other plant species. Several other earlier investigators found salt accumulation (Litwak 1957, Sharma and Tongway 1973) and a change in pH (Fireman and Hayward 1952) in soils beneath plants.

Sometimes such modification occurs in the context of invasion. Exotic species of plants can alter the microclimate to an extent that causes an unfavorable environment for native species. The salt accumulation in an exotic ice plant causes an increase in soil salinity and reduces soil fertility inhibiting the growth of nontolerant plant species allowing it to dominate (Vivrette and Muller 1977, Kloot 1983). The invasion of Myrica faya, an actiorrihozal nitrogen fixer, causes an increase of nitrogen in the area surrounding this plant (D'Antonio and Vitousek 1992). Exotic grasses in semi-arid scrublands have caused the increase in fire because of the increased production of litter (Parsons 1972).

Similarly, a wide variety of other species alter microenvironments through diverse mechanisms. For example, porcupines dig holes that can become filled with water, which then become favorable sites of plant colonization (Yair and Rutin 1981). In aquatic environments, plankton biomass and distribution can affect heat content and thermal structure of lakes due to the light interception and reflection off of these particles (Mazumber et al. 1990).

2.5 - HABITAT CREATION

Both plants and animals create habitats for themselves and other organisms. This creation of habitat can contribute to species diversity and distribution. Early on, Müller (1879) noted that plant physical structures are habitats for animals and plants, and in 1928, Varga coined the term phytotomata to describe the small aquatic habitats created by plants. Möbius (1877) discussed the community of organisms inhabiting oyster beds, "which find everything necessary for their growth and continuance such as suitable soil, sufficient food, the requisite percentage of salt and a temperature favorable to their development." Since these early studies, many species have been identified as habitat creators. Debris dams are created by fallen forest trees, which alter the morphology and stability of streams and so create habitats for various organisms (Heede 1972, Keller and Swanson 1979, Likens and Bilby 1982). Kelp forests (Round 1981) and sea grass prairies (Jones et al. 1994) also support a diverse abundance of plant and animal communities. In more recent literature, it has been noted that leaf shelters serve as homes for other species after they have been abandoned by their arthropod creators (Fukui 2001). Even organisms such as small algae have a large impact on the creation of habitats. Coral reefs are formed dominantly by the action of algae overgrowing and cementing accrual together (Ladd 1961, Womersley and Bailey 1969, Round 1981, Anderson 1992), which provides a habitat for many aquatic organisms. In 1972, Dayton collectively defined these organisms as foundation species that build the structure of the environment.

One of the earliest (Morgan 1868) and most intensely studied species that create habitats are beavers (Naiman 1988, Wright et al. 2002). Early and later studies have determined that beaver dams play an important role on stream ecosystem dynamics by changing hydrology (Gard 1961, Smith et al. 1991), nutrient cycling (Francis et al. 1985, Naiman et al. 1991, Yavitt et al. 1992), decomposition dynamics (Hodgkinson 1975, Naiman et al. 1986), nutrient availability (Wilde et al. 1950, Johnston and Naiman 1990), and biogeochemical cycles (Naiman et al. 1994). The activities of beaver affect wildlife (Bradt 1947, Swank 1949, Grasse and Putnam 1950, Rutherford 1955), stream invertebrates (Hanson and Campbell 1963, McDowell and Naiman 1986), fish (Gard 1961, Hansen and Campbell 1963, Snodgrass and Meffe 1998), and vegetation (Johnston and Naiman 1990, Feldman 1995, Barnes and Dibble 1988, Wright et al. 2002). Such consequences are long lasting (Rudeman and Schoonmaker 1938, Ives 1942, Naimen et al. 1994), spatially extensive, and result in legacy effects after the dam has been abandoned (Neff 1957). In a similar fashion, it has long been noted that alligators also play a very important role as habitat creators in wetland ecosystems. Beard (1938) claimed that wallow digging by alligators had a great impact on organisms in wetland ecosystems. Wallows provide refuge for aquatic and terrestrial vertebrates, invertebrates, and microorganisms (Allen and Neil 1952, Loveless 1959, Finlayson and Moser 1991). The creation of these holes allows the survival of many organisms, and thereby increases local species richness and diversity (Kushlan 1974). Wallows also play a role in shaping plant community structure (Craighead 1968, Palmer and Mazzotti 2004). In addition, alligators also create nest mounds that are used by turtles (Dietz and Jackson 1979) and other reptiles (Kushlan and Kushlan 1980). More recent studies have found that the wallows of crocodiles in Australian swamps are analogous in function to Florida wetland alligator wallows (Magnusson and Taylor 1982).

Mollusks are another group whose importance in the creation of habitats was noted early on (e.g. Möbius 1877). The production of mollusk shells in aquatic environments serves many purposes, such as provision of hard substrate, protection from predation and from physical and physiological stress, and modulation of solute and particulate transport (Gutiérrez et al. 2003).

Early studies found that a variety of organisms live in these habitats, including fish (Breder 1942), octopus (Voss 1956), hermit crabs (Reese 1969), and many other organisms. More recent ecologists have found that shell-producing species can have a large impact on aquatic ecosystems because of the abundance (Russell-Hunter 1983), durability

(Kidwell 1985, Powell et al. 1989), and diverse species occupancy (McLean 1983) of the shell structure.

2.6 - CONCLUSION

Far from being newly recognized phenomena, this historical review makes it clear that ecologists have been actively engaged in studying the myriad ways in which species alter their physical environment for the entire history of ecology. Is there any benefit then in grouping these phenomena under a common term of ecosystem engineering (Jones et al. 1994)? One of the principal challenges facing the science of ecology is the immensely complex and contingent nature of its units of study (Strong 1980, Simberloff 2004). One important tool for ordering this complexity has been to identify key functional traits that have important influence on community or ecosystem processes. Early on, authors like Shaler (1881) and Elton (1927) perceived that even very different species often can share similar functional roles within ecosystems.

Yet, there have been two notable problems in the implementation of this realization over the preceding years. First, many definitions of function have been phenomenological and nonmechanistic. Second, there has been a near obsession with the contribution of trophic mechanisms to functional roles (e.g., Paine 1969), to the neglect of nontrophic mechanisms. We suggest that the ecosystem engineering concept helps remedy both of these difficulties. As the studies in this review illustrate, engineering mechanisms are ubiquitous and play diverse functional roles across a range of ecosystems. The ecosystem engineering concept helps unify under common mechanistic functions a diverse array of processes that previously had been treated as idiosyncratic species-environment interactions. Moreover, the overarching grouping of ecosystem engineer may now move us to draw parallels between species whose effects on the physical environment are quite different, and whose ecosystem functions may also seem quite different (e.g., crabs that affect soil processes vs. plants that form phytotomata). This categorization hopefully will help facilitate the integration of these processes into ecological models that historically have focused exclusively on trophic mechanisms. From a more applied point of view, species that provide important engineering-based functions within ecosystems are being targeted for conservation (Crain and Bertness 2006). We are also beginning to appreciate that invasive species exert many of their most pernicious impacts through ecosystem engineering (Crooks 2002), but also that ecosystem engineers can be important tools for the management and restoration of ecosystems (e.g., Byers et al. 2006).

REFERENCES

Albert, R. (1912). Bodenuntersuchungen im Gebiete der Lüneburger Heide. Zeitschrift fuer Forst und Jagdwesen. 44:2-10.

Aldag, R., and Graff, O. (1975). N-Fraktionen in Regenwurmlosung und deren Ursprungsboden. Pedobiologia 15:151-153.

Allen, R., and Neil, W.T. (1952). The American alligator. Florida Wildlife 6:8-9,44.

Aller, R.C. (1982). Carbonate dissolution in nearshore terrigenous muds: The role of physical and biological reworking. Journal of Geology 90:79-95.

Anderson, F.O., and Kristersen, E. (1991). Effects of burrowing macrofauna on organic matter decomposition in coastal marine sediments. Symposium of the Zoological Society of Land 63:69-88.

Anderson, R.A. (1992). Diversity of eukaryotic algae. Biodiversity and Conservation 1:267-292.

Arthur, H., Hype, M., and Redington, P.G. (1929). Report of the Chief of the Bureau of Biological Survey. Washington, D.C.: United States Department of Agriculture Bureau of Biological Survey, pp. 1-54.

Barley, K.P., and Jennings, A.C. (1959). Earthworms and soil fertility III: The influence of earthworms on the availability of nitrogen. Australian Journal of Agricultural Resources 10:364-370.

Barnes, W.J., and Dibble, E. (1988). The effects of beaver in riverbank forest succession. Canadian Journal of Botany 66:40-44.

Baxter, F.P., and Hole, F.D. (1967). Ant (Formicacinerea) pedoturbation in a prairie soil. Soil Science Society of America Proceedings 31:425-428.

Beard, D.B. (1938). Wildlife Reconnaissance. Washington, D.C.: U.S. Department of the Interior, National Park Service, Everglades National Park Project, p. 106.

Beattie, A.J., and Culver, D.C. (1983). The nest chemistry of two, seed-dispersing ant species. Oecologia 56:99-103.

Beisner, B., and Cuddington, K. (2005). Why a history of ecology? An introduction. In Ecological Paradigms Lost: Routes to Theory Change. K. Cuddington and B. Beisner, Eds. Burlington, MA: Elsevier Academic Press, pp. 1-6.

Bell, R. (1883). The causes of fertility of the land in the Canadian north-west territories. Trans. Royal Society of Canada 8:157-162.

Bertness, M.D. (1984). Habitat and community modification by an introduced herbivorous snail. Ecology 65:370-381.

-. (1985). Fibbler crab regulation of Spartina alterniflora production on a New

England salt marsh. Ecology 66:1042-1055.

-. (1991). Zonation of Spartina spp. in a New England salt marsh. Ecology

72:138-148.

Bertness, M.D., and Callaway, R.M. (1994). Positive interactions in communities. Trends in Ecology and Evolution 9:191-193.

Biberg, I.J. (1749). Oeconomia naturae. Amoenitates Academicae 2:1-52.

Bliss, D., and Smith, H. (1985). Penetration of light into soil and its role in the control of seed germination. Plant, Cell and Environment 8:475-483.

Bradt, G.W. (1947). Michigan Beaver Management. Lancing, MI: Michigan Department of Conservation.

Branner, J.C. (1896). Ants as geologic agents in the tropics. Bulletin of the Geological Society of America VII:295-300.

Breder, C.M. (1942). On the reproduction of Gobiosoma robustum. Zoologica 27:61-65.

Brenchley, G.A. (1981). Disturbance and community structure: An experimental study of bioturbation in marine soft-bottom environments. Journal of Marine Research 39:767-790.

Briese, D.T. (1982). Partitioning of resources amongst seed-harvesters in an ant community on semi-arid Australia. Australian Journal of Ecology 7:299-307.

Brinkman, R. (1932). Uver die Schichtung und ihre Bedingungen. Fortschritte der Geologia und Palaentolgie 2:187-219.

Brown, J.F., and Human, K.G. (1997). Effects of harvester ants on plant species distribution and abundance in a serpentine grassland. Oecologia 112:237-243.

Butler, D.R. (1995). Zoogeomorphology: Animals as Geomorphic Agents. New York: Cambridge University Press.

Byers, J. E., Cuddington, K., Jones, C., Talley, T., Hastings, A., Lambrinos, J., Crooks, J., and Wilson, W. (2006). Using ecosystem engineers to restore ecological systems. Trends in Ecology & Evolution 21:493-500.

Carlson, S.R., and Whitford, W.G. (1991). Ant mound influence on vegetation and soils in a semiarid mountain ecosystem. Am. Midl. Nat. 126:125-139.

Chapin, F.S. III., Van Cleve, K., and Chapin, M.C. (1979). Soil temperature and nutrient cycling in the tussock growth form of Eriophorum vaginatum. Journal of Ecology 67:169-189.

Chorley, R.J., and Beckinsale, R.P. (1991). The History of the Study of Landforms or the Development of Geomorphology, Volume 3: Historical and Regional Geomorphology 1890-1950. New York: Routledge.

Clements, F.E. (1916). Plant Succession. Publication 242. Washington, D.C.: Carnegie Institute of Washington.

Connell, J.H., and Slatyer, R.O. (1977). Mechanisms of succession in natural communities and their role in community stability and organization. The American Naturalist 111:1119-1144.

Costanza, R., Sklar, F.R., and White, M.L. (1990). Modeling coastal landscape dynamics Bioscience 40:91-107.

Cowles, H.C. (1889). The ecological relations of the vegetation on the sand dunes in Lake Michigan. Botanical Gazette 27:95-117.

-. (1911). The causes of vegetative cycles. Botanical Gazette 51:161-183.

Craighead, F.C., Sr. (1968). The role of the alligator in shaping plant communities and maintaining wildlife in the southern everglades. The Florida Naturalist 41:69-74.

Crain, C. M., and Bertness, M. D. (2006). Ecosystem engineering across environmental gradients: Implications for conservation and management. Bioscience 56:211-218.

Crooks, J.A. (2002). Characterizing ecosystem-level consequences of biological invasions: The role of ecosystem engineers. Oikos 97:153-166.

Czerwinski, Z., Jakubczyk, H., and Petal, J. (1971). Influence of ant hills on meadow soils. Pedobiologia 11:277-285.

Dachnowski, A. (1908). The toxic property of bog water and bog soil. Botanical Gazette 46:130-143.

D'Antonio, M., and Vitousek, P.M. (1992). Biological invasions by exotic grasses, the grass/fire cycle, and global change. Annual Review of Ecology and Systematics 23:63-87.

Darwin, C. (1842). The Structure and Distribution of Coral Reefs. Being the First Part of the Geology of the Voyage of the 'Beagle.' London: Smith, Elder & Co.

-. (1881). The Formation of Vegetable Mould Through the Action of Worms with

Observations of Their Habits. London: Murray.

Davison, C. (1891). On the amount of sand brought up by Lob worms to the surface. Geology Magazine (Great Britain) 8:489.

Dayton, P.K. (1972). Toward an understanding of community resilience and the potential effects of enrichments to the benthos at McMurdo Sound, Antartica. In Proceedings of the Colloquium on Conservation Problems in Antarctica, B.C. Parker, Ed. Lawrence, KS: Allen Press, pp. 81-96.

Dietz, D.C., and Jackson, D.R. (1979). Use of alligator nests by nesting turtles. Journal of Herpetology 13:510-512.

Ellison, L. (1949). Establishment of vegetation on depleted subalpine range as influence by microenvironment. Ecol. Monograph 19:95-121.

Elton, C. (1927). Animal Ecology. Chicago: University of Chicago Press.

Engler, A. (1919). Untersuchungen über den Einfluss des Waldes auf den Stand der Gewässer. Mitteilungen DerSchweizerschen AnstaltFuer Das Forstilche Versuchswesen 12:1-626.

Facelli, J.M., and Pickett, S.T.A. (1991). Plant litter: Its dynamics and effects on plant community structure. Botanical Review 57:1-32.

Feldman, A.L. (1995). The effects of beaver (Castor canadensis) impoundment on plant diversity and community composition in the coastal plain of South Carolina. Thesis. University of Georgia, Athens.

Finlayson, M., and Moser, M. (Eds.). (1991). Wetlands. Oxford: International Waterfowl and Wetlands Research Bureau.

Fireman, M., and Hayword, H.E. (1952). Indicator significance of some scrubs in the Escalante Desert, Utah. Botanical Gazette 114:143-155.

Flechault, C., and Combry, P. (1894). Surla flore de la Camargue et des alluvions du Rhone. Bulletin of the Society of Botany France 41:37-58.

Flecker, A.S. (1996). Ecosystem engineering by dominant detritivore in a diverse tropical stream. Ecology 77:1845-1854.

Fowler, S.W., and Knauer, G.A. (1986). Role of large particles in the transport of elements and organic compounds through the oceanic water column. Progress in Oceanography 16:147-194.

Francis, M.M., Naiman, R.J., and Melillo, J.M. (1985). Nitrogen fixation in subarctic streams influenced by beaver (Castor canadensis). Hydrobiologia 121:193-203.

Franco, A.C., and Nobel, P.S. (1989). Effect of nurse plants on the microhabitat and growth of cacti. Journal of Ecology 77:870-886.

Fukui, A. (2001). Indirect interactions mediated by leaf shelters in animal-plant communities. Population Ecology 43:31-40.

Gard, R. (1961). Effects of beaver on trout in Sagehen Creek, California. Journal of Wildlife Management 25:221-242.

Gleason, H.A. (1917). The structure and development of plant associations. Bulletin of the Torrey Botanical Club. 43:463-481.

Glover, P.E., Trump, E.C., and Wateridge, L.E.D. (1965). Termitaria and vegetation on the Loita Plains of Kenya. Journal of Ecology 52:367-377.

Graebner, P. (1895). Studien ueber die norddeutsche Heide. Botanische Jahrbücher für Systematik, Pflanzengeschichte, und Pflanzengeographie 20:500-654.

Grasse, J.E., and Putnam, E.F. (1950). Beaver management and ecology in Wyoming. Wyoming Game and Fish Communication Bulletin No. 6, 52 pp.

Green, R.A., and Reynold, C. (1932). The influence of two burrowing rodents, Dipodo-mys spectabilis spectabilis (kangaroo rat) and Neotome albigula albigula (pack rat) on desert soils in Arizona. Ecology 12:73-80.

Grubb, P.J., Green, H.E., and Merrifield, R.C.J. (1969). The ecology of chalk heath: Its relevance to the calcicole-calcifuge and soil acidification problems. Journal of Ecology 57:175-212.

Guttiérez, J., and Jones, C. (2006). Physical ecosystem engineers as agents of biogeo-chemical heterogeneity. Bioscience 56:227-236.

Gutiérrez, J.L., Jones, C.G., Strayer, D.L., and Iribarne, O.O. (2003). Mollusks as ecosystem engineers: The role of shell production in aquatic habitats. Oikos 101:79-90.

Hanson, W. D., and Campbell, R.S. (1963). The effects of pool size and beaver activity on distribution and abundance of warm-water fishes in a north Missouri stream. American Midland Naturalist 69:136-149.

Heede, B.H. (1972). Influences of a forest on the hydraulic geometry of two mountain streams. Water Resource Bulletin 8:523-530.

Hobbs, R.J. (1985). Harvester ant foraging and plant species distribution in annual grassland. Oecologia 67:519-523.

Hodgkinson, I.D. (1975). Energy flow and organic matter decomposition in an abandoned beaver pond ecosystem. Oecologia (Berlin) 21:131-139.

Hollard, E.A., and Coleman, D.C. (1987). Litter placement effects on microbial and organic matter dynamics in an agroecosystem. Ecology 68:425-433.

Hopp, H. (1946). Soil conservation: Earthworms fight erosion too. Soil Conservation 11:252-254.

Hopp, H., and Slater, C.S. (1948). Influence of earthworms on soil productivity. U.S. Department of Agriculture Bulletin, pp. 421-428.

Hoppe, E. (1898). Uber Veränderung des Waldbodens durch Abholzung. Centralblatt Fuer Das Gesamte Forstwesen 24:51-64.

Horn, H.S. (1974). The ecology of secondary succession. Annual Review of Ecol. Systems 5:25-37.

Ives, R.L. (1942). The beaver-meadow complex. Journal of Geomorphology 5:191-203.

Jamison, V.C. (1942). The slow reversible drying of sandy soils beneath citrus trees in central Florida. Proceedings of the Soil Science Society of America 7:36-41.

Jeanson, C. (1960). Evolution de la matier organique du sol sous l'action de Lumbricus herculeus. Comptes Rendus Academie des Sciences 250:3041-3043.

Johnston, C.A., and Naiman, R.J. (1990). The use of geographical information systems to analyze long-term landscape alteration by beaver. Landscape Ecology 1:41-57.

Jones, C.G., Lawton, J.H., and Shachak, M. (1994). Organisms as ecosystem engineers. Oikos 69:373-386.

-. (1997). Positive and negative effects of organisms as ecosystem engineers.

Ecology 78:1946-1957.

Jouquet, P., Dauber, J., Lagerlof, J., Lavelle, P., and Lepage, M. (2006). Soil invertebrates as ecosystem engineers: Intended and accidental effects on soil and feedback loops. Applied Soil Ecology 32:153-164.

Keller, E.A., and Swanson, F.J. (1979). Effects of large organic material on channel form and fluvial processes. Earth Surface Processes 4:361-380.

Kidwell, S.M. (1985). Palaeobiological and sedimentological implications of fossil concentrations. Nature 318:457-460.

King, W. (1685). Of the bogs and loughs of Ireland. Philosophical Transactions of the Royal Society of London 15:948-960.

King, T.J. (1977). The plant ecology of ant-hills in calcareous grasslands. I. Patterns of species in relation to ant-hills in southern England. Journal of Ecology 65:235-256.

Kloot, P.M. (1983). The role common iceplant (Mesembryanthemum crystallinum) in the deterioration of medic pastures. Australia Journal of Ecology 8:301-306.

Kushlan, J.A. (1974). Observations on the role of the American alligator (Alligator mississippiensis) in the southern Florida wetlands. Copiea 31:993-996.

Kushlan, J.A., and Kushlan, M.S. (1980). Everglades alligator nests: Nesting sites for marsh reptiles. Copeia 1980:930-932.

Ladd, H.S. (1961). Reef building. Science 134:703-715.

Lavelle, P. (2002). Functional domains in soils. Ecological Research 17:441-450.

Levan, M.A., and Stone, E.L. (1983). Soil modification by colonies of black meadow ants in a New York old field. Soil Science Society of America Journal 47: 1192-1195.

Likens, G.E., and Bilby, R.E. (1982). Development, maintenance, and role of organic debris dams in New England streams. In Sediment Budgets and Routing in Forest Drainage Basins, F.J. Swanson, R.J. Janda, T. Dunne, and D.N. Swanston, Eds., USDA Forest Service General Technical Report PNW141. USDA Forest Service, Pacific Northwest Forest, and Range Experimental Station, pp. 122-128.

Litwak, M. (1957). The influence of Tamarix aphylla on soil composition in the northern Negev of Israel. Bull. Res. Coun. Israel, Section D, 6:39-45.

Livingston, B.E., Britton, J.C., and Reid, F.R. (1905). Studies on the properties of an unproductive soil. U.S. Department of Agriculture Bulletin on Bur. Soils, 28.

Lobry de Bruyn, L.A., and Conacher, A.J. (1990). The role of termites and ants in soil modification: A review. Australian Journal of Soil Research 28:55-93.

Lockaby, B.G., and Adams, J.C. (1985). Pedoturbation of a forest by fire ants. Journal of the Soil Science Society of America 99:220-223.

Loveless, C.M. (1959). A study of the vegetation in the Florida Everglades. Ecology 40:1-9.

Lunt, H.A., and Jacobson, G.M. (1944). The chemical composition of earthworm casts. Soil Science 58:367-375.

Lyell, C. (1873). Principles of Geology. New York: D. Appleton Company.

Magnusson, W.E., and Taylor, J.A. (1982). Wallows of Crocodylus porosus as dry season refuges in swamps. Copeia 2:470-480.

Mandel, R.D., and Sorenson, C.J. (1982). The role of the western harvester ant (Pogonomyrmex occidentalis) in soil formation. Soil Science Society of America Journal 46:785-788.

Maycock, P.F. (1967). Jozef Paczoski: Founder of the science of phytosociology. Ecology 48:1031-1034.

Mazumber, A., Taylor, W.D., McQueen, D.J., and Lean, D.R.S. (1990). Effects of fish and plankton on lake temperature and mixing depth. Science 247:312-315.

McDowell, D., and Naiman, R.J. (1986). Structure and function of a benthic invertebrate stream community as influenced by beaver (Castor canadensis). Oecologia (Berlin) 68:481-489.

McKinney, A.L. (1929). Effect of forest litter on soil temperature and soil freezing in autumn and winter. Ecology 10:312-321.

McLean, R. (1983). Gastropod shells: A dynamic resource that helps shape benthic community structure. Journal of Experimental Marine Biology and Ecology 69:151-174.

McMaster, R.L. (1967). Compactness variability of estuarine sediments: An in situ study. In Estuaries, G.H. Lauff, Ed. Washington, D.C.: American Association for the Advancement of Science, 83:261-267.

Meadows, A. (1991). Burrows and burrowing animals: An overview. Symposium of the Zoological Society of London 63:1-13.

Meadows, P.S., and Meadows, A. (Eds.). (1991). The environmental impact of burrowing animals and animal burrows. Oxford: Clarendon Press.

Miller, D.C. (1961). The feeding mechanism of fiddler crabs, with ecological considerations of feeding adaptations. Zoologica 46:89-101.

Möbius, K. (1877). Reprinted from Die Auster und die Autserwirthschaft. Berlin, Wieg-nundt, Hempel and Parey. In Report of the U.S. Commission of Fisheries, translated by H.J. Rice, 1880, pp. 683-751.

Moore, H.B. (1931). The muds of the Clyde Sea Area. III. Chemical and physical conditions, rate of sedimentation and fauna. Journal of the Marine Biology Association U.K. 17:325-358.

Morgan, L.H. (1868). The American Beaver and His Works. Philadelphia: J.B. Lippincott.

Muller, C.H. (1953). The association of desert annuals with shrubs. American Journal of Bot. 40:53-60.

Müller, F. (1879). Notes on the cases of some south Brazilian Trichoptera. Transactions of the Entomological Society of London 1879:131-144.

Muller, P.E. (1887). Studien über die natürlichen Humusformen and deren Einwirkungen auf Vegetation und Boden. Berlin: Julius Springer, p. 324.

Muller, W.H., and Muller, C.H. (1956). Association patterns involving desert plants that contain toxic products. American Journal of Botany 43:354-355.

Naiman, R.J. (1988). Animal influences on ecosystem dynamics. Bioscience 38:750-752.

Naiman, R.J., Manning, T., and Johnston, C.A. (1991). Beaver population fluctuations and tropospheric methane emission in boreal wetlands. Biogeochemistry 12:1-15.

Naiman, R.J., Melillo, J.M., and Hobbie, J.E. (1986). Ecosystem alteration of boreal forest streams by beaver (Castor canadensis). Ecology 67:1254-1269.

Naiman, R.J., Pinay, G., Johnston, C.A., and Pastor, J. (1994). Beaver influences on the long-term biogeochemical characteristics of boreal forest drainage networks. Ecology 75:905-921.

Neff, D.J. (1957). Ecological effects of beaver habitat abandonment in the Colorado Rockies. Journal of Wildlife Management 21:80-84.

Niering, W.A., Whittaker, R.H., and Lowe, C.H. (1963). The saguaro: A population in relation to environment. Science 142:15-23.

Nihlgard, B. (1972). Plant biomass, primary production and distribution of chemical elements in a beech and planted spruce forest in south Sweden. Oikos 23:69-81.

Olson, J.S. (1958). Rates of succession and soil changes on southern Lake Michigan sand dunes. Botanical Gazette 119:125-170.

Paine, R.T. (1969). A note on trophic complexity and community stability. American Naturalist 103:91-93.

Palmer, M.L., and Mazzotti, F.J. (2004). Structure of Everglades alligator holes. Wetlands 24:115-122.

Parle, J.N. (1963). A microbial study of earthworm casts. Journal of General Microbiology 31:13-22.

Parsons, J.J. (1972). Spread of African pasture grasses to the American tropics. Journal of Range Management 25:12-17.

Petrone, R.M., Waddington, J.M., and Price, J.S. (2001). Ecosystem scale evapotranspiration and CO2 exchange from a restored peatland. Hydrological Processes 15:283-284.

Pollock, M.M., Naiman, R.J., and Hanley, T.A. (1998). Plant species richness in riparian wetlands—A test of biodiversity theory. Ecology 79:94-105.

Posey, M.H., Bumbauld, B.R., and Armstrong, D.A. (1991). Effects of a burrowing mud shrimp, Upogebia pugettensis (Dana), on the abundances of macro-infauna. Journal of Experimental Marine Biology and Ecology 148:283-294.

Powell, E.N., Staff, G.M., Davies, D.J., and Callender, W.R. (1989). Macrobenthic death assemblages in modern marine environments: Formation, interpretation, and application. Critical Review of Aquatic Science 1:555-589.

Pringle, C.M., and Blake, G.A. (1994). Quantitative effects of atyid shrimp (Decapoda: Atyidae) on the depositional environment in a tropical stream: Use of electricity for experimental exclusion. Canadian Journal of Fishing and Aquatic Science 51:1443-1450.

Pringle, C.M., Blake, G.A., Covich, A.P., Buzby, K.M., and Finley, A. (1993). Effects of omnivorous shrimp in a montane tropical stream: Sediment removal disturbance of sessile invertebrates and enhancement of understory algal biomass. Oecologia 93:1-11.

Ramann, E. (1897). Uver Lochkahlschlä. Zeitschrift fuer Forst und Jagdwesen 29:697.

Reese, E. (1969). Behavioral adaptations of intertidal hermit crabs. American Zool. 9:343-355.

Reichelt, A.C. (1991). Environmental effects of meiofaunal burrowing. Symposium of the Zoological Society of London 63:33-52.

Reichman, O., and Seabloom, E.W. (2002a). Ecosystem engineering: A trivialized concept? Trends in Ecology and Evolution 17:308.

-. (2002b). The role of pocket gophers as subterranean ecosystem engineers.

Trends in Ecology and Evolution 17:44-49.

Reissek, S. (1856). Ueber die Bildungsgeschichte der Donauinseln im mittleren Laufe dieses Stromes. Flora 39:622-624.

Reynolds, H.G. (1958). The ecology of the Merriam kangaroo rat (Dipodomys merriami Mearns) on grazing land of southern Arizona. Ecology Monograph 28:111-127.

Rhoads, D.C. (1963). Rates of sediment reworking by Yoldia limatulain Buzzards Bay, Massachusetts, and Long Island Sound. Journal of Sedimentary Petrology 33:723-727.

-. (1967). Biogenic reworking of inter and subtidal sediments in Barnstable Harbor and Buzzards Bay, Massachusetts. Journal of Geology 75:61-76.

Rhoads, D.C., and Young, D. (1970). The influence of deposit feeding organisms on sediment stability and community trophic structure. Journal of Marine Research 28:150-178.

Rogers, L.E., and Lavigne, R.J. (1974). Environmental effects of Western harvester ants on the shortgrass plains ecosystem. Environ. Ent. 3:994-997.

Round, F.E. (1981). The Ecology of Algae. New York: Cambridge University Press.

Rudeman, R., and Schoonmaker, W.J. (1938). Beaver dams as geologic agents. Science 8:523-525.

Russell-Hunter, W.D. (1983). Overview: Planetary distribution and ecological constraints upon the mollusca. In The Mollusca, W.D. Russell-Hunter, Ed., Vol. 6 ecology. Orlando: Academic Press, pp. 1-27.

Rutherford, W.H. (1955). Wildlife and environmental relationships of beavers in Colorado forests. Journal of Forestry 53:803-806.

Salem, M.Z., and Hole, F.D. (1968). Ant pedoturbation in a forest soil. Proceedings of Soil Science Society of America 32:563-567.

Salisbury, E.J. (1922). Stratification and hydrogen-ion concentration of soil in relation to leaching and plant succession with special reference to woodlands. Journal of Ecology 4:220-240.

Schreiner, O., and Reed, H.S. (1907). Some factors influencing soil fertility. U.S. Department of Agriculture Bulletin on Bureau of Soils 28.

Shaler, N. (1892). Effect of Animals and Plants on Soils. In Origin and Nature of Soils. 12th Annual Report, Director U.S. Geol. Survey, Part J. Geology Annual Report, Sector of the Interior. Washington, D.C.: Government Printing Office.

Sharma, M.L., and Tongway, D.J. (1973). Plant induced soil salinity in two brush (Atriplex spp.) communities. Journal of Range Management 26:121-124.

Sharpley, A.N., and Syers, J.K. (1976). Potential role of earthworm casts for the phosphorus enrichment of run-off waters. Soil Biology Biochemistry, 8:341-346.

Simberloff, D. (2004). Community ecology: Is it time to move on? The American Naturalist 163:787-799.

Smith, J.N., and Schafer, C.T. (1984). Bioturbation processes in continental slope and rise sediments delineated by Pb-210 microfossil and textural indicators. Journal of Marine Research 42:1117-1145.

Smith, M.E., Driscoll, C.T., Wyskowski, B.J., Brooks, C.M., and Cosentini, C.C. (1991). Modification of stream ecosystem structure and function by beaver in the Adirondak Mountains, New York. Canadian Journal of Zoology 69:55-61.

Snodgrass, J.W., and Meffe, G.K. (1998). Influence of beavers on stream fish assemblages: Effects of pond age and watershed position. Ecology 79:928-942.

Soluk, D.A., and Craig, D.A. (1990). Digging with a vortex: Flow manipulation facilitates prey capture by a predatory stream mayfly. Limnology and Oceanography 35:1201-1206.

Stallins, J.A. (2006). Geomorphology and ecology: Unifying themes for complex systems in biogeomorphology. Geomorphology 77:207-216.

Steenberg, W.F., and Lowe, C.H. (1969). Critical factors during the first year of life of saguaro (Cereus giganteus) at Saguaro National Monument. Ecology 50:825-834.

Steenstrup, J.J.S. (1842). Geognostik-geolgisk Undersogelse of Skovmoserne Vidnesdam og Liffemose I det nordlige Sjaelland, ledsaget af sammen-lignednde Bemaerkninger, hentede fra Danmarks Skov-, Kjaer- og Lyngmoser I Almindelighed. Det Kongelige Danske Videnskabernes Selskabs Naturvidenskabe lige ogMathematishev Afhandlingher 9:17-120.

Stockdill, S.M.J. (1966). The effects of earthworms of pastures. Proceedings of the New Zealand Ecol. Society 13:68-75.

Streve, F. (1931). Physical conditions in sun and shade. Ecology 12:96-104.

Strong, D.R. (1980). Null hypotheses in ecology. Synthese 43:271-285.

Swank, W.G. (1949). Beaver Ecology and Management in West Virginia. Conservation Commission of West Virginia, Division of Game Management, Bulletin No. 1.

Tansley, A.G. (1935). The use and abuse of vegetation concepts and terms. Ecology 16:284-307.

-. (1949). Britain's Green Mantle. London: George Allen and Unwin.

Taylor, W.P. (1935). Some animal relations to soils. Ecology 16:127-136.

Taylor, W.P., and McGinnie, W.G. (1928). The bio-ecology of forest and range. The Scientific Monthly 27:177-182.

Turner, R.M., Alcorn, S.M., and Olin, G. (1969). Mortality of transplanted saguaro seedlings. Ecology 5:835-844.

van Rhee, J.A. (1965). Earthworms activity and plant growth in artificial cultures. Plant Soil 22:45-48.

Varga, L. (1928). Ein interessanter Biotop der Bioconöse von Wasserorganismen. Biologisches Zentralblatt 48:143-162.

Viles, H. (1988). Biogeomorphology. Oxford: Blackwell.

Vitousek, P.M. (1986). Biological invasions and ecosystem properties. In Biological Invasions of North America and Hawaii, H.A. Mooney and J. Drake, Eds. New York: Springer, pp. 163-176.

Vitousek, P.M. (1990). Biological invasions and ecosystem processes: Toward an integration of population biology and ecosystem studies. Oikos 57:7-13.

Vivrette, N.J., and Muller, C.H. (1977). Mechanism of invasion and dominance of coastal grassland by Mesembrythemum crystallinum. Ecological Monographs 47:301-318.

Von Hardenberg, J., Meron, E., Shachak, M., and Zarmil, Y. (2001). Diversity of vegetation patterns and desertification. Physical Review Letters 87(198101):1-4.

von Humboldt, A. 1807 (1805). Essal sur la géographie dea plantes. Paris: Schoell et Tubingue Cotta.

Voss, G.L. (1956). A review of the cephalopods of the Gulf of Mexico. Bulletin of Marine Science 6:85-178.

Wallace, G.T., Jr., Mahoney, O.M., Dulmage, F., Storti, F., and Dudek, N. (1981) Firstorder removal of particulate aluminum in oceanic surface water. Nature 293:729-731.

Warming, E., (1891). De psammophile Formationer I Danmark. Videnskabelige Meddelelser fra den Natuurhistorisch Forening i Kobenhavn (Copenhagen), pp. 153-202.

Wiken, E.B., Broersma, K., LavKulich, L.M., Farstad, L. (1976). Biosynthetic alternation in British Columbia soil by ants (Formica fusca Linné). Journal of Soil Science Society of America 40:422-426.

Wilde, S.A., Youngberg, C.T., and Hovind, J.H. (1950). Changes in composition of ground water, soil fertility, and forest growth produced by the construction and removal of beaver dams. Journal of Wildlife Management 14:123-128.

Williams, S.T., and Gray, T.R.G. (1974). Decomposition of litter on the soil surface. In Biology of Plant Litter Decomposition, Vol. 2, C.H. Dickinson and G.J.F. Pugh, Eds. New York: Academic Press, pp. 611-632.

Womersley, H.B.S., and Bailey, A. (1969). The marine algae of Solomon Islands and their place in biotic reefs. Philosophical Transactions of the Royal Society of London 255:433-442.

Wright, J.P., Jones, C.G., and Flecker, A.S. (2002). An ecosystem engineer, the beaver, increases species richness at the landscape scale. Oecologia 132:96-101.

Yair, A., and Rutin, J. (1981). Some aspects of the regional variation in the amount of available sediments produced by isopods and porcupines, northern Negev, Israel. Earth Surface Processes and Landforms 6:221-234.

Yavitt, J.B., Angell, L.L., Fakey, T.J., Cirma, C.P., and Driscoll, C.T. (1992). Methane fluxes, concentrations and production in two Adirondack beaver impoundments. Limnology and Oceanography 37:1057-1066.

Oplan Termites

Oplan Termites

You Might Start Missing Your Termites After Kickin'em Out. After All, They Have Been Your Roommates For Quite A While. Enraged With How The Termites Have Eaten Up Your Antique Furniture? Can't Wait To Have Them Exterminated Completely From The Face Of The Earth? Fret Not. We Will Tell You How To Get Rid Of Them From Your House At Least. If Not From The Face The Earth.

Get My Free Ebook


Post a comment