Ecology of Eastern White Pine Seed Caches made by Small Forest Mammals
TL;DR: The contribution to forest regeneration of seeds stored by these small forest mammals is probably of minor significance except when bumper seed crops are produced and large numbers of caches are created.
Abstract: Typical seed caches made in the fall of the year by white—footed mice (Peromyscus leucopus) and red—backed voles (Clethrionomys gapperi) contained 20—30 pine seeds, buried beneath the litter of pine needles and in contact with mineral soil. Many caches were revisited by the mice and their contents destroyed before winter. Most caches not decimated in the fall were invaded the following spring. However, some of them escaped complete destruction and their unconsumed seeds germinated and produced seedlings. Although mice make their caches in micro—environments highly favorable to germination, their subsequent feedings on the stored seeds, both before snowfall and before and during the spring germination period, greatly deplete the number of potential germinants. Therefore, the contribution to forest regeneration of seeds stored by these small forest mammals is probably of minor significance except when bumper seed crops are produced and large numbers of caches are created. Under these circumstances, stored seeds may be of sufficient quantity to exceed food requirements of the mice. If pirating by other animals is low, then a surplus of seeds is left to help regenerate the forest.
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TL;DR: It is clear that the pattern of seed predation is highly structured and that it co evolved at, the chemical, spatial, and temporal level and the processes and patterns are ideal candidates for ecological and evolu tionary analyses.
Abstract: Many plants suffer very heavy preand/or post-dispersal seed predation by animals. A few exemplary studies (2,18,38,52,74,87, 106, 110, 111, 124, 140, 161, 162, 171, 181, 187, 196, 197, 203, 205, 207, 217, 220, 227) and a variety of shorter reports scattered through the agricultural, botanical, and zoological literature suggest a large and important, yet unexploited, field of study. It is clear that the pattern of seed predation is highly structured and that it co evolved at, the chemical, spatial, and temporal level. It involves all levels of animal-plant interaction from the internal energy budget of indi viduals to the entire community (203 ) . Owing to parental and sibling com petition, successful development of a seedling may depend on the seed's dis persal (101). Equally important, thc seed must escape from the predators at the seed crop and in the parent plant's habitat before and after dispersal (111 ) . The game is played by mobile predators in search of sessile prey; escape is through a single dispersal move, seed chemistry, parental morphol ogy and behavior, and evolutionary change. The processes and patterns are:ideal candidates for ecological and evolu tionary analyses (83, 111 ) of the typcs traditionally conducted by zoologi cally oriented biologists (37, 51,73, 141, 155,156, 182) or applied to plants in general ( 40,116,208,209,241) . Seed predators and leaf eaters are often lumped together in ecological discussions, but they differ in ways especially important in the coevolution of seed predators and seeds: (a) Like leaves, seeds are highly subdivided and small, but unlike leaves and other vegetative parts, they have very high nutrient values per unit volume. ( b) While obvious in large quantities, they may be extremely inconspicuous once dispersed. ( c) Being comparatively dormant, seeds have low self-repair abilities but can contain high concentra tions of toxic compounds (secondary substances) with less sophisticated ad aptations against self-intoxication than can leaves and meristematic tissues. ( d ) Seed production is not continually required for direct survival of the parent plant; seed timing, quantity, and quality can therefore be manipu lated more freely by natural selection than can these traits of leaves and other vegetative parts. (e ) Seeds are not directly replaced· when killed or germinated; once removed, seeds may be absent far longer than edible vege tative parts and thus a common plant species may be rare in time,toa seed
1,841 citations
TL;DR: An environmental patchwork which exerts powerful influences on the distri butions of organisms, their interactions, and their adaptations is considered.
Abstract: discon tinuities on many scales in time and space. The patterns of these discontinuities produce an environmental patchwork which exerts powerful influences on the distri butions of organisms, their interactions, and their adaptations. Consideration of this environmental patch structure is critical to both the theory and management of populations. Despite the obvious heterogeneity of natural sys te.ms, most of the models that form the theoretical fabric of population biology and ecology (and that are increasingly conditioning our perception of reality) tell mathe matical stories of populations
1,019 citations
TL;DR: The results indicate that fecundity and dispersal can be resolved, even under a closed canopy, and that recruitment of many species is limited by the density and location of source, dispersal patterns, or both.
Abstract: Recruitment limitation of tree population dynamics is poorly understood, because fecundity and dispersal are difficult to characterize in closed stands. We present an approach that estimates seed production and dispersal under closed canopies and four limitations on recruitment: tree density and location, fecundity, seed dispersal, and estab- lishment. Consistent estimates are obtained for 14 canopy species using 5 yr of census data from 100 seed traps and several thousand mapped trees and seedlings from five southern Appalachian forest stands that span gradients in elevation and moisture. Fecundity (seed production per square centimeter of basal area) ranged over four orders of magnitude, from 10 0 cm 2 basal area/yr (Carya, Cornus, Nyssa, Quercus )t o.10 3 cm 2 /yr (Betula). Mean dispersal distance ranged from , 5m( Cornus, Nyssa )t o.20 m (Acer, Betula, Liriodendron, Tsuga) and was positively correlated with fecundity. Species also differ in the degree of seed clumping at fine (1 m 2 ) spatial scales. Dispersal patterns can be classed in two groups based on dispersal vector: wind-dispersed taxa with high fecundities, long-distance dis- persal, and low clumping vs. animal-dispersal taxa with low fecundities, short-distance dispersal, and a high degree of clumping. ''Colonization'' limitations caused by sizes and locations of parent trees, fecundity, and dispersal were quantified as the fraction of sites receiving seed relative to that expected under null models that assume dispersal is nonlocal (i.e., long-distance) and not clumped (i.e., Poisson). Difference among species in coloni- zation levels ranged from those capable of saturating the forest floor with seed in most stands (Acer, Betula, Liriodendron) to ones that leave much of the forest floor without seed, despite presence of adults (Carya, Cornus, Nyssa, Oxydendrum ). Seedling establish- ment is one of the strongest filters on recruitment in our study area. Taken together, our results indicate (1) that fecundity and dispersal can be resolved, even under a closed canopy, and (2) that recruitment of many species is limited by the density and location of source, dispersal patterns, or both.
558 citations
01 Jan 1998
TL;DR: In this article, the authors present an approach that estimates seed production and dispersal under closed canopies and four limitations on recruitment: tree density and location, fecundity, seed dispersal, and estab- lishment.
Abstract: Recruitment limitation of tree population dynamics is poorly understood, because fecundity and dispersal are difficult to characterize in closed stands. We present an approach that estimates seed production and dispersal under closed canopies and four limitations on recruitment: tree density and location, fecundity, seed dispersal, and estab- lishment. Consistent estimates are obtained for 14 canopy species using 5 yr of census data from 100 seed traps and several thousand mapped trees and seedlings from five southern Appalachian forest stands that span gradients in elevation and moisture. Fecundity (seed production per square centimeter of basal area) ranged over four orders of magnitude, from 10° cm2 basal area/yr (Carya, Cornus, Nyssa, Quercus) to >10 3 cmVyr (Betula). Mean dispersal distance ranged from 20 m (Acer, Betula, Liriodendron, Tsuga) and was positively correlated with fecundity. Species also differ in the degree of seed clumping at fine (1 m2) spatial scales. Dispersal patterns can be classed in two groups based on dispersal vector: wind-dispersed taxa with high fecundities, long-distance dis- persal, and low clumping vs. animal-dispersal taxa with low fecundities, short-distance dispersal, and a high degree of clumping. "Colonization" limitations caused by sizes and locations of parent trees, fecundity, and dispersal were quantified as the fraction of sites receiving seed relative to that expected under null models that assume dispersal is nonlocal (i.e., long-distance) and not clumped (i.e., Poisson). Difference among species in coloni- zation levels ranged from those capable of saturating the forest floor with seed in most stands (Acer, Betula, Liriodendron) to ones that leave much of the forest floor without seed, despite presence of adults (Carya, Cornus, Nyssa, Oxydendrum). Seedling establish- ment is one of the strongest filters on recruitment in our study area. Taken together, our results indicate (1) that fecundity and dispersal can be resolved, even under a closed canopy, and (2) that recruitment of many species is limited by the density and location of source, dispersal patterns, or both.
546 citations
TL;DR: A corollary of provisioning offspring with food is a stable, relatively high metabolic rate, which ensures that parents can maintain a steady flow of food to the relatively few, "expensive" offspring.
Abstract: We limit our discussion of food storage, or caching, to the movement of potential food items from one location to another for eating at some later time. This activity occurs exclusively in those animals that bring food to their offspring, and not in those that bring their offspring to food (i.e. that lay their eggs near food in a favorable microhabitat). Provisioning offspring is limited taxonomically to mammals, most birds, and some Hymenoptera. Moving food to a favorable microhabitat was apparently the first transitional step in the evolution of more complex systems of provisioning offspring in hymenopterans (72). Although all species that cache food provision their offspring, the converse is not true. Relatively few of the animals that provision their young with food also cache food, and caching food has no obvious connection to the glandular secretion of milk, which probably initiated offspring provisioning in the evolutionary history of mammals. Repeated traveling from a foraging area to dependent young seems to precondition animals for caching food. One of the goals of our review will be to determine what other conditions among species of birds and mammals and their food favor the evolution of caching. We limit our discussion to birds and nonhuman mammals because of our own backgrounds and because experimental studies have recently been done on these vertebrates (4, 14, 20, 48a, 62, 10la, 103-105, 116, 117, 128), although earlier investigations started with wasps (121). A corollary of provisioning offspring with food is a stable, relatively high metabolic rate (even in the Hymenoptera), which ensures that parents can maintain a steady flow of food to the relatively few, "expensive" offspring
401 citations
References
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TL;DR: For example, Dowdeswell, Fisher and Ford as discussed by the authors used trellis diagrams to estimate the number of moths in North America, and then used a regression model to obtain the true density of tsetse flies.
Abstract: The estimation of the total size of plant or animal populations is of great importance in a variety of biological problems, which may relate to population growth, ecological adaptation, genetic constitution, natural selection and evolution, and so on. Obvious practical consequences are the maintenance of human food supplies and the control of insect pests. For human communities and populations of sessile organisms procedures employing fixed sampling units are available, but for mobile populations other methods must be used. The basic technique, which seems to have been first used by Lincoln (1930) to estimate the total number of duck in North America, and is sometimes referred to as the 'Lincoln Index', is as follows. One catches, marks and releases a certain number of animals taken at random from the population. A further random sample is caught and the proportion of marked animals noted. Then the total number of marked animals released divided by the proportion of marked animals in the sample captured can clearly be used as an estimate of the total population size. The same method was adopted independently by Jackson (1933), who used it for estimating the true density of tsetse flies. Jackson (1937, 1939) subsequently extended his treatment to allow for both birthand death-rates, advocating his 'negative' and ' positive' methods. Further work by Jackson (1940) took into account the effects of migration. Recapture methods have also been successfully applied to populations of Lepidoptera. Dowdeswell, Fisher & Ford (1940) caught, marked and released moths on several different days. On each day the marked insects were classified according to the day on which they had previously been released. Analysis of the data, which could be exhibited in a triangular array, or 'trellis' diagram, gave estimates of the size of the moth population for each day. The interpretation of trellis diagrams was further developed by Fisher & Ford (1947). They estimated daily numbers, taking into account a death-rate which was obtained from the average time interval between marking and recapture. A more detailed application of this procedure was made by D~owdeswell et al. (1949). Although in the various papers cited above effective use has been made of estimates of population size and of birthand death-rates, there has been little discussion for the most part of the precision of the results obtained. Jackson (1937, 1939) obtained both the population estimate and its variance for the 'negative' and 'Positive' methods by fitting a curve
375 citations
TL;DR: Tevis et al. as discussed by the authors analyzed the stomach contents of 509 chipmuns of four species (Eutamias amoenus, speciosus, townsendi, and quadrimaculatus) and 273 mantled squirrels (Citellus lateralis) during one year.
Abstract: A study of feeding habits is important to an understanding of the rodent factor in forest ecology. But a mere list of foods does not indicate the complexity of interrelations between animals and food supplies, which differ markedly in kind and amount from place to place and vary enormously between seasons and from one year to another. Interpretation of the data is necessary. This paper attempts an interpretation of stomach analyses of 509 chipmunks of four species (Eutamias amoenus, speciosus, townsendi, and quadrimaculatus) and 273 mantled squirrels (Citellus lateralis), which are important kinds of diurnal rodents of the commercial timber belt of northeastern California. The area studied lies within a thirty mile radius of Quincy, Plumas County, California, where the granitic Sierra Nevada meets the Great Volcanic Plateau to the north and the arid Great Basin to the east. The merging of these vast geographic regions creates a complicated and congested biota, for many species come together which are widely separated elsewhere. Some habitats are occupied by all four kinds of chipmunks as well as the mantled squirrel. The forest is composed of ponderosa, Jeffrey, and sugar pines, Douglas fir, ,white fir, and incense cedar. It has been subjected to every degree of logging, and is broken by brushfields that are the heritage of disastrous fires. The chief shrubs of Volcanic and Sierran brushfields are manzanita (Arctostaphylos patula) and whitethorn (Ceanothus cordulatus). The technique of stomach analysis was described in an earlier paper (Tevis, 1952). The main point to be noted here is that the food was classified into types. An attempt was made to learn which foods maintained high numbers of rodents, to determine seasonal trends in feeding habits, and to compare the diets of different species. The work was done as part of an investigation of the influence of rodents on reforestation conducted by the Department of Zoology, University of California at Davis in cooperation with the California Forest and Range Experiment Station of the United States Forest Service. I am grateful to Dr. Tracy I. Storer for advice and assistance. Specimens were collected in 1951 from mid-March, when hiberators appeared, until the third week of the following September. This paper, then, is an account of feeding habits during one year. No two years are alike, and a sulmmary of the main features of 1951 follows. In spring-when occasional rain hastened the melting of patches of snowsurface fungi (Gyromitra, Peziza, and Morchella) were locally abundant; forbs and grasses greened the forest floor; one of the earliest of the herbs, a figwort, set quantities of seeds; manzanita yielded the heaviest flower crop in years; winged termites emerged from rotten logs on sultry afternoons; and ants and spiders were numerous.
77 citations
TL;DR: Unrecovered caches of Pinus ponderosa and Purshia tridentata seed made by small rodents frequently result in establishment of seedling clusters, and studies in montane forests of central Oregon indicate that about 90% of thePurshia seedlings that germinate develop in clusters.
Abstract: Unrecovered caches of Pinus ponderosa and Purshia tridentata seed made by small rodents frequently result in establishment of seedling clusters. Studies in montane forests of central Oregon indicate that about 90% of the Purshia seedlings that germinate develop in clusters. At least 15% of the pine seedlings result from rodent caches.
68 citations
TL;DR: In the fall of 1928, the life history of the western fox squirrel was studied, a major objective being to determine, if possible, the effect of this species on forest reproduction.
Abstract: Caching of seeds by rodents for future food supplies is recognized by wildlife managers, foresters, nurserymen, and others to be important in plant reproduction. If the entire crop is consumed, reproduction is prevented but if the crop is stored though not all used by the rodent harvesters, plant reproduction may be encouraged by the seed being protected through the winter from normal exposure to severe climatic conditions (Shaw, 1936). Olmsted (1937) has pointed out that, in Connecticut, "black oak (Quercus velutina) invades many communities through burial of its acorns by squirrels." More knowledge is needed of the caching habit and its effect on forest and other vegetation. Of the many forest-dwelling rodents, probably none is of greater significance to their environment than the larger tree squirrels. Red squirrels and most small ground-dwelling rodents gather many seeds into relatively few hoards, but the larger squirrels make many caches, each of one or a few nuts. This wide scattering and planting, if in suitable seed-beds, may at times be a desirable factor in perpetuating the forest. These squirrels, however, need large quantities of food to sustain them, especially as they do not hibernate through the long winters. They depend heavily on the fruit of commercially important hardwood species such as oaks, hickories, walnuts, beech and formerly, the American chestnut. The rapidity with which these nut crops are cleaned up from the forest floor is almost phenome'nal. Hahn (1908) describes the "disappearance" of a very large acorn crop on the Farm of the University of Indiana in the autumn of 1906, when gray squirrels were also very abundant. He "estimated that each of the large white oaks produced from two to eight thousand acorns during that season. Eighty acres [were] heavily wooded with white oaks and nearly a hundred acres more [had] a considerable growth of these trees. Before November 1, the immense crop of acorns had been so completely garnered by the squirrels that none were in sight on top of the leaves and only an occasional one could be found bythe most careful search." In the long run, the fate of the seed crops controls that of the forest. In the fall of 1928 I studied the life history of the western fox squirrel (Sciurus niger rufiventer), a major objective being to determine, if possible, the effect of this species on forest reproduction. This investigation was a part of the program of a junior instructorship which continued through the following spring under the School of Forestry and Conservation, University of Michigan. I am grateful to Dean S. T. Dana and Alvin G. Whitney for arranging the financial assistance that made possible this year of study and field work and to Professors Whitney, H. M. Wight and L. R. Dice for advice and suggestions on this project. Two studies on caching and recovery of nuts to determine the percentage and method of removal from hiding places, were made in Forest Hills Cemetery in Ann Arbor. The squirrels were accus-
62 citations
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