共查询到20条相似文献,搜索用时 15 毫秒
1.
Akira Haraguchi 《Ecological Research》1992,7(3):205-212
A relationship was sought between species distribution and seasonal change in the redox property of peat in a floating mat
in Mizorogaike Pond, central Japan. The mat surface experienced an annual submergence-emergence cycle due to its sinking-rising
movement. Redox potential (Eh) of the surface peat showed little difference between communities in the mat in the submergence
season (January–June) and early emergence season (July–August). However variation in Eh among communities was clear in the
late emergence season (September–December). Among seven communities in the floating mat, theMenyanthes trifoliata-Rhynchospora fauriei, M. trifoliata-Eriocaulon sikokianum-E. bondoense f.pilosum, Sphagnum cuspidatum andM. trifoliata-Carex thunbergii communities had high Eh (400–600 mV) in the late emergence season, while theMenyanthes trifoliata andPhragmites australis-M. trifoliata communities had lower Eh (200–400 mV). TheM. trifoliata-Isachné globosa community was intermediate (300–500 mV). The earlier the emergence of the peat surface began, the higher the Eh became in
the late emergence season. 相似文献
2.
The squid Loligo forbesii is the only cephalopod species currently targeted by fisheries in the northern NE Atlantic. An active predator, it feeds
primarily on fish, crustaceans and cephalopods. During 15 years since the only previous large-scale study of the diet of this
species in Scottish waters, there have been substantial changes in marine fish abundances. The present study evaluates sources
of variation (temporal, ontogenetic) in diet composition and prey size preferences of L. forbesii, including a comparison of contemporary (July 2006–June 2007) and historical (1990–1992) dietary datasets. Results revealed
significant size-related and seasonal variation in diet composition and prey size. Teleost fish of the families Ammodytidae
and Gobiidae were eaten by squid of all sampled sizes, although occurrence of gobies was generally more frequent in smaller
squids, while Gadidae were eaten more frequently by larger squids. Cannibalism was also more frequent in larger squids. Compared
to the 1990–1992 dataset, clupeid fish were less important in the diet of squid in 2006–2007, while the importance of gobies
increased, and the size of gobies eaten also increased. The trend in gadoids differed according to the index used: their frequency
of occurrence was considerably higher in 2006–2007 than in 1990–1992, but their numerical importance was slightly lower. In
general, results provided little evidence that changes in the diet of L. forbesii correspond with changes in fish abundance, at least at the scales at which these are measured. 相似文献
3.
The timing of reproduction is one of the most crucial life history traits, with enormous consequences for the fitness of an
individual. We investigated the effects of season and timing of birth on local survival probability in a small mammalian hibernator,
the common dormouse (Muscardinus avellanarius). Local monthly survival probability was lowest in the early active season (May–August, ϕadult = 0.75–0.88, ϕjuvenile = 0.61–0.68), increased during the late active season (August–October), and highest during hibernation (October–May, ϕadult = 0.96–0.98, ϕjuvenile = 0.81–0.94). Consequently, dormice had an extremely high winter survival probability. We observed two peaks in the timing
of reproduction (June and August/September, respectively), with the majority of juveniles born late in the active season.
Although early investment in reproduction seems the better life history tactic [survival probability until onset of reproduction:
ϕborn early = 0.46, 95% confidence interval (CI) 0.28–0.64; ϕborn late = 0.19, 95% CI = 0.09–0.28], only females with a good body condition (significantly higher body mass) invest in reproduction
early in the year. We suggest the high over-winter survival in dormice allows for a unique life history pattern (i.e., combining
slow and fast life history tactics), which leads to a bimodal seasonal birth pattern: (1) give birth as early as possible
to allow even the young to breed before hibernating, and/or (2) give birth as late as possible (leaving just enough time for
these young to fatten) and enter directly into a period associated with the highest survival rates (hibernation) until maturity. 相似文献
4.
The feeding of tufted puffin and horned puffin nestlings was studied on two islands of Tauyskaya Bay of the Sea of Okhotsk:
at Talan Island in 1999–2004 and 2006 and Umara Island in 1994 and 1996–1997. The composition of the puffin diet during the
breeding season was determined. The main fish species in the diet were determined and the seasonal and annual dynamics of
the occurrence of the items was analyzed. Comparative data on biological characteristics, such as the size, weight and age
of the fish caught by these birds, as well as the size and composition of food samples, were collected. Differences between
the age groups of fish in the diets of the two puffin species were revealed. Conditions for forming of seabird feeding base
in Tauyskaya Bay were described. 相似文献
5.
Zulima González-Parrado Carmen Reyes Fuertes-Rodríguez Ana M. Vega-Maray Rosa M. Valencia-Barrera F. Javier Rodríguez-Rajo Delia Fernández-González 《Aerobiologia》2006,22(1):47-53
Winter-flowering trees such as the alder (Alnus glutinosa (L.) Gaertner) can survive periods of adverse climatic conditions, entering a period of dormancy in the early fall. The end
of dormancy and the start of the pollen season require a period of low temperatures followed by another of warm temperatures.
These requirements were studied from 1995 to 2002, in order to develop a model to predict the onset of the alder pollen season
in Ponferrada (Spain). Chilling accumulation took place from late October to late December or early January. The best result
was obtained with a threshold temperature of 6.5 °C and an average of 848 chilling hours (CH). Heat requirements were calculated
at maximum temperature, an average 143 growth degree days (GDD) were needed, with a threshold temperature of 0 °C. In order
to validate models, predicted values were compared with real values for 2002–2003, 2003–2004 and 2004–2005, years not used
in developing the models. Predictions for the pollen-season start-date differed only slightly from observed dates: in 2002–2003
predicted and observed dates were the same, in 2003–2004 there was a difference of 7 days and in 2004–2005 a difference of
3 days. 相似文献
6.
Janette Wallis 《International journal of primatology》1995,16(3):435-451
Although wild chimpanzees are not seasonal breeders, there are seasonal effects on several aspects of chimpanzee reproduction.
I examined the seasonal incidence of anogenital swelling in cyclic, pregnant, and acyclic female chimpanzees in Gombe National
Park, May 1975–April 1992, and surveyed important reproductive events to determine whether there is a seasonal effect. I analyzed
data by season (wet vs. dry) and seasonal quarter;early dry season = May–July;late dry = August–October;early wet = November–January;late wet = February–April. When data for the 17 years are combined, the percentage of females in each reproductive state remains
consistent throughout the year. In a given month, 30–35% of subjects were in the cyclic category, 11–15% were pregnant, and
54–61% were acyclic. Cyclic females showed full swelling more often during the late dry season. Pregnant females exhibited
anogenital swelling more often during the late dry and early wet seasons. Acyclic females also exhibited a seasonal effect
with more anogenital swelling during the late dry season. There is no seasonal difference in frequency of live births (dry,
20;wet, 23). However, the timing of conception showed a seasonal effect (dry, 32;wet, 16). Consistent with earlier reports, the onset of postpartum cycles is highly seasonal;30 occurred during dry season, 9 during wet season. The occurrence of first full swellings for young females is also concentrated
in the late dry season. It appears that the dry season is a time of great change for Gombe chimpanzee reproductive physiology.
Previous studies indicated that seasonal changes in food availability play a role in increasing group size during the dry
season and social contact between females can enhance cyclicity. Accordingly, I suggest that seasonal changes in diet may
play a role, either directly (food content) or indirectly (social contact), to alter reproductive physiology. 相似文献
7.
Andreasen V 《Journal of mathematical biology》2003,46(6):504-536
The persistence of Influenza A in the human population relies on continual changes in the viral surface antigens allowing
the virus to reinfect the same hosts every few years. The epidemiology of such a drifting virus is modeled by a discrete season-to-season
map. During the epidemic season only one strain is present and its transmission dynamics follows a standard epidemic model.
After the season, cross-immunity to next year's virus is determined from the proportion of hosts that were infected during
the season. A partial analysis of this map shows the existence of oscillations where epidemics occur at regular or irregular
intervals.
Received: 16 February 2001 / Revised version: 11 June 2002 /
Published online: 28 February 2003
Key words or phrases: Infectious disease – Influenza drift – Cross-immunity – Seasonal epidemics – Iterated map 相似文献
8.
Katherine Renton 《Biotropica》2006,38(2):280-283
Scarlet Macaw diet was determined during the breeding season of February–June 1998. Macaws were primarily granivorous, exhibiting a narrow diet during the dry season, with low variety of food items in adult and nestling diets. Seeds of Cnidoscolus spp. and Schizolobium parahybum, tree species characteristic of floodplain forest, were predominant in nestling diets, and may provide protein‐rich food resources. River floodplains provided important nest sites and food resources for Scarlet Macaws during the breeding season. 相似文献
9.
Douglas W. Wacker Alexander J. Coverdill Carolyn M. Bauer John C. Wingfield 《Journal of Ornithology》2010,151(1):79-86
The Fox Sparrows, Passerella iliaca, include multiple groups and subspecies distributed at several latitudes from the Alaskan arctic to the southwestern United
States. As such, this species represents a potential model for investigating latitudinal variation in androgen secretion and
aggressive territoriality in male passerines. Breeding male Fox Sparrows from two subspecies within two groups, the Sooty
Fox Sparrow, P. i. sinuosa, and the Red Fox Sparrow, P. i. zaboria, were assessed for aggressive territoriality and androgen responsiveness at multiple latitudes in arctic and subarctic Alaska.
Subarctic Sooty Fox Sparrows had higher circulating androgen levels in the early (8.54 ng/ml) versus mid–late breeding season
(2.44 ng/ml). Males in the mid–late breeding season did not up-regulate androgen secretion in response to social challenge,
but were aggressive and spent more time within 5 m of a decoy during a simulated territorial intrusion (STI) than early breeding
males. Male subarctic Red Fox Sparrows had slightly higher circulating androgen levels (2.29 ng/ml) than arctic males (1.10 ng/ml)
in the mid–late breeding season. However, androgen levels were not correlated with blood collection time after a social challenge
in either group, suggesting that neither arctic nor subarctic males up-regulate androgen secretion during the mid–late breeding
period. Arctic males spent more time within 5 m of a decoy and sang less than subarctic males during an STI in the mid–late
breeding season. These findings demonstrate that the Fox Sparrow is a tractable model for investigating the latitudinal regulation
of aggressive territoriality and androgen responsiveness in passerines. 相似文献
10.
Marta Montoro Patrick De Clercq Johannes Overgaard Lene Sigsgaard 《Entomologia Experimentalis et Applicata》2020,168(6-7):492-501
The commercial production of Orius spp. (Hemiptera: Anthocoridae), including Orius majusculus (Reuter), relies on the use of eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) as rearing diet. However, E. kuehniella eggs have become an expensive fodder thus increasing the price of these key biological control agents. The use of artificial diets potentially decreases the production costs. In this regard, establishing a link between dietary composition and fitness could advance the development of an optimum alternative artificial diet for these predatory insects. The aim of the current study was to test the effect of six artificial diets with different macronutrient composition on the development and reproductive fitness of O. majusculus when compared with the effect of E. kuehniella eggs. In general, nymphal survival was not affected by diet, whereas development was slightly delayed on artificial diets. However, female body mass and fecundity were significantly lower on all of the artificial diets compared with the E. kuehniella eggs diet, suggesting that artificial diets were of inferior quality. Within artificial diets, females fed the viable diet with highest content in lipid laid more eggs than those raised on the most protein-rich diets. We found there was some variation in carcass composition between the O. majusculus fed the various diets, but these variations did not match the differences found in the fitness parameters measured. 相似文献
11.
The diet composition of king penguins (Aptenodytes patagonicus) at Heard Island (53°05′S; 73°30′E) was determined from stomach contents of 98 adults captured as they returned to the island
throughout 1992. During the two growth seasons, the diet was dominated by the myctophid fish Krefftichthys anderssoni (94% by number, 48% by mass). The paralepidid fish Magnisudis prionosa contributed <1% by numbers but 17% by mass. Mackerel icefish (Champsocephalus gunnari) accounted for 17% by mass of chick diet in late winter, when chicks were malnourished and prone to starvation, although
its annual contribution to the penguins' diet was only 3%. Squid was consumed only between April and August; Martialia hyadesi was the commonest squid taken, comprising 40–48% of the winter diet. The remainder of the diet consisted of the squid Moroteuthis ingens and fish other than K. anderssoni. The energy content of the diet mix fed to the chicks varied seasonally being highest during the growth seasons (7.83 ± 0.25 kJ g−1) and lowest in winter (6.58 ± 0.19 kJ g−1). From energetic experiments we estimated that an adult penguin consumed 300 kg of food each, of which its chick received
55 kg during the 1992 season. The chicks received large meals at the beginning of winter (1.2 ± 0.3 kg) and during the middle
of the second growth season (1.2 ± 0.3 kg), and their smallest meals in late winter (0.4 ± 0.1 kg). The gross energy required
to rear a king penguin chick was estimated to be 724 MJ. The potential impact of commercial fisheries on the breeding activities
of king penguins is discussed.
Received: 20 October 1997 / Accepted: 27 April 1998 相似文献
12.
Eva Rossmanith Kerstin H?ntsch Niels Blaum Florian Jeltsch 《Journal of Ornithology》2007,148(3):323-332
Populations of Lesser Spotted Woodpecker (Picoides minor) are decreasing in size, necessitating management strategies. However, data on the reproductive biology of this species are
scarce. The aim of this study was to investigate the influence of timing of breeding and nestling diet on the reproductive
success of the Lesser Spotted Woodpecker and thereby contribute to an understanding of the determinants influencing its reproductive
success. During 6 study years between 1996–2003, we investigated various variables of reproductive success in a Lesser Spotted
Woodpecker population in the Taunus low mountain range, Germany. We observed nestling feeding at breeding holes to assess
the composition of nestling diet and how it changes during the season. Clutch size, number of fledglings as well as body mass
of the nestlings declined with the start of egg laying. Pairs composed of individuals that had breed together in previous
years started egg laying earlier than newly established pairs. Nestling diet consisted mainly of aphids, caterpillars, craneflies
and wood-living larvae. The composition changed considerably within the breeding season in both early and late broods. However,
early broods were provided with caterpillars more frequently, whereas late broods received wood-dwelling larvae more often.
Our results suggest that Lesser Spotted Woodpeckers time their breeding so as to coincide with the early nestling stage with
the highest availability of caterpillars, since this is the time of highest energy demand. Moreover, food availability declines
during the breeding season, and the decline in reproductive performance seems to be an effect of this development. 相似文献
13.
Much of the research into herbivore ecology and evolution has focused on patterns and mechanisms of niche partitioning in
the diets of specialized grazers and browsers, but the significance of the balance of grazing and browsing within intermediate
feeders present unique questions that have received less attention. We explored the nutritional effects of varying the balance
of grass and browse in the winter diets of elk (Cervus elaphus). We compiled published data from three similar studies that monitored the mass dynamics of captive elk fed diets of pure
grass, pure browse or 1 of 14 mixed diets in winter feeding trials. Elk lost mass (up to 22% of initial body weight) in 29
of 33 feeding trials, similar to wild elk in winter. We used regression models of mass dynamics, considering the linear, quadratic
or logarithmic effects of the proportion of the diet that was grass (≈1 − proportion of the diet that was browse) and the
additive and interactive effects of nitrogen intake. Diet composition had strong effects on mass dynamics, and all models
explained ≥73% of the variation (adjusted r
2) in mass dynamics. Nitrogen intake had uniformly positive effects on mass balance, and increasing grass intake caused improved
maintenance of body mass up to a point, but further increases in the proportion of grass in the diet had neutral or negative
effects on body mass. Overall, the data suggest that elk are adapted to consuming mixed diets. Nonetheless, data on the foraging
behavior and diet selection of wild elk in many populations show that elk often consume grass-dominated diets and sometimes
consume browse-dominated diets, but rarely consume mixed diets. Physiological adaptations to mixed diets may place unique
spatio-temporal constraints on diet selection in intermediate feeders and impose large penalties for a sub-optimal balance
of grazing and browsing. 相似文献
14.
J. A. Rehg 《International journal of primatology》2006,27(5):1399-1428
Polyspecific associations (PSA) occur when 2 or more species maintain proximity or coordinate activities. PSA may provide ecological benefits similar to those of monospecific groups, i.e., protection against predation and improved foraging efficiency, but may also impart costs, such as feeding competition. I studied 3 New World Callitrichidae—Callimico goeldii, Saguinus fuscicollis, and S. labiatus—in northwestern Brazil over 18 mo between April 1999 and August 2003, during which single primary study groups of C. goeldii, S. labiatus, and S. fuscicollis consistently associated with one another. I compared patterns of PSA participation to variation in plant diets during wet and dry seasons. All 3 species associated an average 61% of observation time, but with significant seasonal variation in PSA. During the dry season, April–September, PSA occurred significantly less frequently than during the wet season, October–March (37% vs. 88%). The variation in PSA corresponded with seasonal shifts in plant food diets, resulting in less dietary overlap among all 3 species during the dry season, particularly between Callimico goeldii and Saguinus labiatus. Dietary richness, diversity, and evenness were also lower in the dry compared to the wet season for each species. The results suggest a link between PSA participation and diet among the taxa; foraging-related costs or feeding competition may constrain PSA during the dry season. 相似文献
15.
Nakagawa N 《Primates; journal of primatology》2003,44(1):3-11
Phytochemical or nutrient analyses of primate diets have revealed clues to their food selection in a single species. On the
other hand, few interspecific comparisons of phytochemical or nutrient composition of primate diets have been made, although
diets are considered to differ in phytochemical or nutrient content from primate species to species, since different species
have different body weights and different morphological and physiological characteristics. I compared the nutrient content
of diet between patas monkeys (Erythrocebus patas) and tantalus monkeys (Cercopithecus aethiops tantalus) living sympatrically in Cameroon. Patas subsisted on a smaller number of food items, most of which were also tantalus food
items. Then, I compared the protein–fiber ratio and the available energy content of the food items eaten by patas (patas foods)
with those items eaten only by tantalus (tantalus foods). Both variables were higher in patas than tantalus foods, although
there was no significant difference in available energy of plant foods. Next, when I performed discriminant analysis for patas
foods and tantalus foods, employing the above two variables, a discriminant function with positive coefficients for both variables
was obtained. The mean discriminant-function score of patas foods was higher than that of tantalus foods. Despite being somewhat
larger in weight, patas selectively fed on a smaller number of foods of higher quality than did tantalus. I discuss why the
results are inconsistent with a well known body weight–diet relationship (Jarman–Bell principle). Energy-efficient locomotion
enables patas to exploit not only small dispersed food items of high quality but also areas where high-quality foods are distributed
in clumps.
Electronic Publication 相似文献
16.
Reproductive cycles ofSebastes taczanowskii,compared with those of other rockfishes of the genusSebastes 总被引:1,自引:1,他引:0
Hiroya Takahashi Kazunori Takano Akihiro Takemura 《Environmental Biology of Fishes》1991,30(1-2):23-30
Synopsis Seasonal reproductive cycles were examined in both sexes ofSebastes taczanowskii, captured in southern Hokkaido, Japan. The reproductive cycle in females was divided into four periods: recovery (July–August),
vitellogenesis (September–March), gestation (April–May) and parturition (June). Spermatozoa were first observed in November
in the ovarian cavity, where no structural specialization was present for sperm storage. Fertilization of oocytes appeared
to occur in April, when the oocytes underwent a rapid process of final maturation. Embryos developed in the ovary quite synchronously
and were released in June; empty ovaries indicated the rockfish has a single parturition. The reproductive cycle in males
comprised five periods: resting (December–July), early maturation (February–May), mid-maturation (June–August), late maturation
(September–October) and functional maturation (November). In November when active spermatogenesis had been completed, a large
amount of spermatozoa was preserved in the sperm duct, and the males were therefore ready for mating. A comparison was made
of the reproductive cycles of four species of the genusSebastes inhabiting southern and northern waters of Japan. It suggests that the northern species tend to prolong gametogenesis in
both sexes while the southern species have the opposite tendency. Sperm storage in the ovary also tends to be longer in the
northern than in the southern species. 相似文献
17.
In the temperate climate zone in Europe the composition of the diet of predatory vertebrates shows evident variability between
the warm and cold season. However, the recently observed climate warming can mitigate the effect of snow cover and low temperatures
on the winter foraging ecology of raptors, thus affecting trophic webs in ecosystems. We analysed diet variability in the
tawny owl Strix aluco, between the warm and cold seasons of four unusually warm years (as compared to reference years of 1950–2000) in two habitats
(forest vs. farmland) in Central Poland. The most important prey group in the tawny owl’s diet were mammals, constituting
over 80% of prey items. There were distinct diet differences between the two seasons: insectivorous mammals, birds and amphibians
were caught more often during the warm season, and Muridae and Arvicolidae during the cold season. The proportion of insectivorous
mammals, voles and amphibians was significantly higher in forest than in farmland. Diet diversity, analysed with rarefaction
methods and expressed as the expected cumulative mammal species number for a given number of randomly sampled preyed mammals,
was independent of season and higher in forest than in the agricultural habitat. We conclude that even during unusually warm
years tawny owls change significantly their feeding habits between the warm and cold season. The effect of season, habitat
and weather factors on diet variability in raptors are discussed. 相似文献
18.
Ivan Norscia Valentina Carrai Silvana M. Borgognini-Tarli 《International journal of primatology》2006,27(4):1001-1022
According to optimal foraging theory, herbivores can base food choice mainly on the quality or the quantity of food, or both. Among herbivorous primates, folivorous lemurs living in the highly seasonal environment of Madagascar have to cope with the shortage of high-quality food during the dry season, at least in deciduous forests. We studied (Verreaux's sifaka) in Kirindy, western Madagascar, to understand the influence of dry season and food quality and quantity on behavioral patterns and feeding strategy (qualitative vs. quantitative dietary choice) of a folivorous lemur in a deciduous forest. We followed 7 groups (4 groups/period; 3 individuals/group/month) during 4 periods of the year (wet season: February–March; early/middle/late dry season: May–June; July–September; October–November). We collected samples of plants eaten and examined behavioral and feeding patterns, considering food quality (macronutrients, proteins/fibers ratio, and tannins) and abundance. We found 1) a significant reduction of home range, core area, and daily path length from the wet to the dry season, possibly related to dietary change and 2) a daily period of inactivity in the dry season for energy conservation. Regarding the feeding strategy, Kirindy sifakas showed 1) high variation and selection in choosing food items and 2) a dietary choice based mainly on quality: Kirindy sifakas fed on plant species/families independently from their abundance and tannins represented a feeding deterrent during the dry season. Overall, behavioral and dietary adaptations allow Kirindy sifakas to overcome the shortage of high-quality food in the lean period. 相似文献
19.
The abundance, food and feeding biology of Clarias albopunctatus was studied over a period of 17 months in the lower River
Anambra, Nigeria. The catfish was more abundant in late dry season (January–March) and early rainy season (April–June) than
in other periods of the year in the small-sized Akwu pond than in other habitats. Feeding intensity was higher at night and
at dawn (20.00–05.00 h) than during the day (08.00–17.00 h) in the 151–200 mm TL size class and during the rainy season (April–September).
There was no sex-dependent variation in feeding intensity. Insects were the predominant food, followed by crustaceans. Of
primary importance were Chironomidae (mainly Chironomus spp. and Tanypus sp.), Odonata nymphs, Dytiscus sp., mosquito larvae
and pupae, Gyrinus sp., Daphnia sp., Ostracoda and Tilapia fry. Qualitative food composition and food richness were size,
but not sex – or season-dependent. Diet breadth increased with catfish size and during the rainy season. The feeding behaviour
of the catfish include foraging, shovelling and surface feeding. Abundant food and ability to switch to more available items
enable C. albopunctatus to maintain its abundance in the River Anambra.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Semiarid areas in the US have realized extensive and persistent exotic plant invasions. Exotics may succeed in arid regions by extracting soil water at different times or from different depths than native plants, but little data is available to test this hypothesis. Using estimates of root mass, gravimetric soil water, soil-water potential, and stable isotope ratios in soil and plant tissues, we determined water-use patterns of exotic and native plant species in exotic- and native-dominated communities in Washington State, USA. Exotic and native communities both extracted 12 ± 2 cm of water from the top 120 cm of soil during the growing season. Exotic communities, however, shifted the timing of water use by extracting surface (0–15 cm) soil water early in the growing season (i.e., April to May) before native plants were active, and by extracting deep (0–120 cm) soil water late in the growing season (i.e., June to July) after natives had undergone seasonal senescence. We found that δ
18O values of water in exotic annuals (e.g., −11.8 ± 0.4 ‰ for Bromus tectorum L.) were similar to δ
18O values of surface soil water (e.g., −13.3 ± 1.4 ‰ at −15 cm) suggesting that transpiration by these species explained early season, surface water use in exotic communities. We also found that δ
18O values of water in taprooted exotics (e.g., −17.4 ± 0.3 ‰ for Centaurea diffusa Lam.) were similar to δ
18O values of deep soil water (e.g., −18.4 ± 0.1 ‰ at −120 cm) suggesting that transpiration by these species explained late season, deep water use. The combination of early-season, shallow water-use by exotic winter-actives and late-season, deep water-use by taprooted perennials potentially explains how exotic communities resist establishment of native species that largely extracted soil water only in the middle of the growing season (i.e., May to June). Early season irrigation or the planting of natives with established root systems may allow native plant restoration. 相似文献