Population response of reintroduced bighorn sheep after observed commingling with domestic sheep

Bighorn sheep (Ovis canadensis) often die from respiratory disease after commingling with domestic sheep. From 2000 to 2009, we observed commingling between domestic and reintroduced bighorn sheep in 3 populations in UT, USA. We investigated how commingling affected survival of radio-collared female bighorns that were released initially (founder) and those that were subsequently released (augmented). We predicted that the proportion of young surviving to their first winter and population growth would be lower after observed commingling with domestic sheep. We observed groups of bighorns year-round on 2,712 occasions and commingling between domestic sheep and bighorns in 6 instances. On Mount Timpanogos, survival rates were best modeled as constant for females (n?=?57) before and after observed commingling with domestic sheep. Survival rates of female bighorns, however, decreased significantly in Rock Canyon (n?=?21) and on Mount Nebo (n?=?22) for founder, but not augmented bighorns after observed commingling with domestic sheep. Also, the proportion of young surviving to their first winter was almost 3 times lower and population growth was reduced for bighorns after observed commingling with domestic sheep in Rock Canyon and on Mount Nebo. Commingling between domestic and bighorn sheep reduced population parameters in 2 of 3 bighorn populations we studied; however, on Mount Timpanogos, interactions between those 2 species were not fatal for radio-collared female bighorns. Wildlife biologists should manage for spatial separation of these 2 species and consider the location of hobby farms and trailing operations of domestic sheep near release sites for bighorns.     

Patterns of Tamarix water use during a record drought

During a record drought (2006) in southwest Kansas, USA, we assessed groundwater dynamics in a shallow, unconfined aquifer, along with plant water sources and physiological responses of the invasive riparian shrub Tamarix ramosissima. In early May, diel water table fluctuations indicated evapotranspirative consumption of groundwater by vegetation. During the summer drought, the water table elevation dropped past the lowest position previously recorded. Concurrent with this drop, water table fluctuations abruptly diminished at all wells at which they had previously been observed despite increasing evapotranspirative demand. Following reductions in groundwater fluctuations, volumetric water content declined corresponding to the well-specific depths of the capillary fringe in early May, suggesting a switch from primary dependence on groundwater to vadose-zone water. In at least one well, the fluctuations appear to re-intensify in August, suggesting increased groundwater uptake by Tamarix or other non-senesced species from a deeper water table later in the growing season. Our data suggest that Tamarix can rapidly shift water sources in response to declines in the water table. The use of multiple water sources by Tamarix minimized leaf-level water stress during drought periods. This study illustrates the importance of the previous hydrologic conditions experienced by site vegetation for controlling root establishment at depth and demonstrates the utility of data from high-frequency hydrologic monitoring in the interpretation of plant water sources using isotopic methods.     

Influence of climate and disturbance on the growth of Tsuga canadensis at its southern limit in eastern North America

It has long been hypothesized that trees growing at range limits likely also occur near the limit of their ecological amplitude and thus, should be more sensitive to climate variability than individuals growing nearer the range core. We developed a tree-ring chronology using Tsuga canadensis individuals from three disjunct stands at the species’ southern limit to quantify the influence of climate and disturbance on radial growth patterns. The tree-ring record extended 158 years from 1850 to 2007. Significant negative relationships were found between the STANDARD chronology and monthly mean temperature, monthly maximum temperature, and monthly minimum temperature during the previous and current summer, while significant positive relationships were documented between the STANDARD chronology and monthly minimum temperature for September and October of the current year. Also, significant positive relationships were documented between the STANDARD chronology and monthly total precipitation for September of the previous year and May of the current year. Response function analysis showed that monthly climate variables (r ² = 0.22) and prior growth (r ² = 0.40) explained 62% of the variance in the T. canadensis tree-ring chronology. A time series plot for the T. canadensis chronology showed that actual tree growth agreed relatively well with the predicted growth based on significant climate variables. However, positive departures from the predicted growth were noted. Dendroecological analysis revealed these departures were likely related to disturbance events. Our results indicated that T. canadensis individuals at its southernmost extent are sensitive to regional climate, but not more so than trees nearer the range core. We hypothesize that microenvironmental conditions of T. canadensis stands at its southern limit are similar to conditions within the contiguous distribution of the species, which may explain this pattern.     

The combined effects of a long‐term experimental drought and an extreme drought on the use of plant‐water sources in a Mediterranean forest

Vegetation in water‐limited ecosystems relies strongly on access to deep water reserves to withstand dry periods. Most of these ecosystems have shallow soils over deep groundwater reserves. Understanding the functioning and functional plasticity of species‐specific root systems and the patterns of or differences in the use of water sources under more frequent or intense droughts is therefore necessary to properly predict the responses of seasonally dry ecosystems to future climate. We used stable isotopes to investigate the seasonal patterns of water uptake by a sclerophyll forest on sloped terrain with shallow soils. We assessed the effect of a long‐term experimental drought (12 years) and the added impact of an extreme natural drought that produced widespread tree mortality and crown defoliation. The dominant species, Quercus ilex, Arbutus unedo and Phillyrea latifolia, all have dimorphic root systems enabling them to access different water sources in space and time. The plants extracted water mainly from the soil in the cold and wet seasons but increased their use of groundwater during the summer drought. Interestingly, the plants subjected to the long‐term experimental drought shifted water uptake toward deeper (10–35 cm) soil layers during the wet season and reduced groundwater uptake in summer, indicating plasticity in the functional distribution of fine roots that dampened the effect of our experimental drought over the long term. An extreme drought in 2011, however, further reduced the contribution of deep soil layers and groundwater to transpiration, which resulted in greater crown defoliation in the drought‐affected plants. This study suggests that extreme droughts aggravate moderate but persistent drier conditions (simulated by our manipulation) and may lead to the depletion of water from groundwater reservoirs and weathered bedrock, threatening the preservation of these Mediterranean ecosystems in their current structures and compositions.     

Ecological life history of Polymnia canadensis,a monocarpic species of the North American Temperate Deciduous Forest: Demography

A demographic investigation was conducted to assess variation in life history of Polymnia canadensis (Asteraceae), a geographically-widespread, herbaceous species of deciduous forests in eastern North America. During 1985-1994, 23,063 seedlings of P. canadensis were monitored at five central Kentucky study sites. Numbers at the end were: biennials, 554; triennials, 142; winter annuals, 16; monocarpic perennials, 2; tricarpic perennials (three years), 3; and dicarpic perennials (some skipped years) that matured in the first year of life, 23; in the second year, 60; and in the third year, 9. Weekly cohorts of P. canadensis generally exhibited Deevey Type III survivorship with highest seedling mortality in summer associated with low soil moisture. Wide spatial variation in life history was displayed by the fact that fall germination cohorts at dry sites generally had greater germination and survivorship than at mesic sites during seedling establishment, while the reverse was true for spring cohorts. This led to more reproductive individuals in fall germination cohorts than spring cohorts at dry sites and generally the opposite case at mesic sites. Forest shade in mesic sites caused slower growth and a greater frequency of longer-lived reproductive individuals than in open, dry sites, but it also resulted in higher survivorship than at dry sites during moderate drought. Annual population growth rate averaged across four years was not significantly different between a dry site and mesic site, indicating that despite forest shade, P. canadensis persisted in the mesic site as well as it did in the dry site. Population structure varied among years, seasons, and study sites; at two study plots, a 2-year flowering cycle of mass seeding and senescence persisted for 4 years. At a smaller scale, there was little difference in survivorship between study plots within sites or between quadrats within study plots, while in a few instances there were large differences in the number of reproductive individuals. Weekly cohorts that germinated early within seasonal cohorts had greater number of reproductive individuals than later weekly cohorts, but not consistently greater survivorship. Several droughts induced temporal variation that was as important as spatial variation. During these droughts, the population size of all cohorts that germinated prior to the droughts declined to zero at all sites, and biennials were the longest lived type of reproductive individuals. During drought, Deevey Type I survivorship was prevalent, and lack of seed rain led to dependence on persistent seed banks for recruitment in some seasonal cohorts.     

Development of polymorphic microsatellite loci for North American river otters (Lontra canadensis) and amplification in related Mustelids

In order to complement ecological research on native and reintroduced populations of the North American river otter (Lontra canadensis), we developed 10 polymorphic microsatellite loci that would permit us to evaluate population genetic structure and conduct fecal DNA analyses. The number of alleles per locus ranged from 3 to 14 and observed heterozygosity ranged from 0.23 to 0.68. Preliminary screening revealed that primers were polymorphic in a subset of other Mustelids.     

Population dynamics of the threatened Oregon spotted frog before and after drought mitigation

Amphibians are among the most sensitive taxa to climate change, and species inhabiting arid and semiarid landscapes at the extremes of their range are especially vulnerable to drought. The Jack Creek, Oregon, USA, population of Oregon spotted frogs (Rana pretiosa) faces unique challenges because it occupies the highest elevation site in the species' extant range and one that has been transformed by loss of American beavers (Castor canadensis), which historically maintained open water. We evaluated the effects of drought mitigation (addition of excavated ponds) on relationships between local and regional water availability, inactive legacy beaver dams, and Oregon spotted frog population dynamics in the Jack Creek system. We conducted egg mass surveys and capture-mark-recapture sampling at a treatment reach with excavated ponds and 3 reference reaches over 13 years; surveys spanned a period before and after pond excavation at the treatment and 1 primary comparison reference reach. We analyzed data using a combination of robust design capture-mark-recapture estimators and generalized linear mixed models to characterize population dynamics. Adult Oregon spotted frog survival was approximately 19.5% higher at the treatment reach than the primary reference reach during the study period. Annual survival was most strongly associated with late summer vegetation greenness, a proxy for water availability, and males had higher survival than females. Among the 4 study reaches, the treatment reach consistently had higher late summer vegetation greenness, and the hydrology functioned more independently of regional precipitation patterns relative to the reference reaches; however, these dynamics were not linked to pond excavation. Breeding was concentrated in 2 legacy beaver ponds that were deepened by excavation during the study compared to an unexcavated beaver pond, 2 excavated ponds without legacy beaver dams, and 9 reference ponds. These results point to the benefit of enhancing existing beaver structures and indicate that management actions aimed at maintaining surface water for breeding in spring and saturated soils and ponded water for adults in late summer would benefit this unique population of Oregon spotted frogs in the face of drought.     

Water conservation in<Emphasis Type="Italic"> Artemisia tridentata</Emphasis> through redistribution of precipitation

Water conservation is important for plants that maintain physiologically active foliage during prolonged periods of drought. A variety of mechanisms for water conservation exist including stomatal regulation, foliage loss, above- and below-ground allocation patterns, size of xylem vessels and leaf pubescence. Using the results of a field and simulation study with Artemisia tridentata in the Great Basin, USA, we propose an additional mechanism of water conservation that can be used by plants in arid and semi-arid environments following pulses of water availability. Precipitation redistributed more uniformly in the soil column by roots (hydraulic redistribution of water downward) slows the rate at which this water can subsequently be taken up by plants, thus prolonging water availability during periods of drought. By spreading out water more uniformly in the soil column at lower water potentials following precipitation events, water use is reduced due to lower soil conductivity. The greater remaining soil water and more uniform distribution result in higher plant predawn water potentials and transpiration rates later in the drought period. Simulation results indicate that plants can benefit during drought periods from water storage following both summer rain events (small summer pulses) and overwinter recharge (large spring pulse). This mechanism of water conservation may aid in sustaining active foliage, maintaining root-soil hydraulic connectivity, and increasing survival probability of plants which remain physiologically active during periods of drought.     

Space Use,Survival, Movements,and Reproduction of Reintroduced Louisiana Black Bears

ABSTRACT Studies of reintroduced animals are beneficial to evaluate the success of reintroduction programs and to understand factors influencing fitness of reintroduced individuals. The geographic distribution of the federally threatened Louisiana black bear (Ursus americanus luteolus) has been reduced to 3 isolated populations due to habitat loss and excessive harvest. We reintroduced 23 adult female Louisiana black bears and their cubs to east-central Louisiana, USA, and documented postrelease space use, survival, movements, and reproduction. Individual females used larger home ranges after reintroduction than they had in the source population (P = 0.037). Spring ranges of reintroduced females were smaller than summer, autumn, and annual ranges (all P < 0.09), which did not differ from each other (all P > 0.60). Survival of reintroduced females did not differ between their first (S = 0.933) and second (S = 1.00) year after release or from annual survival of females in the source population (S = 0.964–1.00). Mean straight-line distance traveled by females from their release sites to the center of established home ranges or last recorded locations was 22.7 km. Six females reproduced after reintroduction and produced 15 cubs. Mean postrelease litter size of parturient reintroduced females (2.5) was similar to reported mean litter size of females in the source population (2.4). Our results suggest that the Louisiana reintroduction program is proceeding favorably; however, future studies should continue to monitor survival and reproduction of reintroduced females in Louisiana. Additional demographic parameters (i.e., cub survival) should be estimated to allow for population viability analysis to determine if the new population is self-sustaining.     

Landmark Territoriality in the Neotropical Paper Wasps Polistes canadensis (L.) and P. carnifex (F.) (Hymenoptera: Vespidae)

Male Polistes canadensis and P. carnifex aggregate along crests of prominent ridges in Santa Rosa National Park, Costa Rica. At these sites males of both species defend territories (trees and shrubs) by chasing conspecific rivals. Territories do not contain nests or resources that are collected by females. Chasing by territorial males reduces the amount of time spent by intruders in a territory. I describe and contrast male territorial behavior of both species. Some male P. canadensis are territorial while others in the same area exhibit patrolling behavior, flying from one occupied territory to another. Males of P. carnifex exhibit territoriality only. Patrolling in P. canadensis is an outcome of relatively high male density along the ridge, rendering territories in short supply, as shown by the observation that experimentally vacated territories are seized rapidly by formerly patrolling males. Due to a high intraspecific intrusion rate, territorial male P. canadensis spend less time perching and more time flying and chasing intruders from their territories than do male P. carnifex. Males of these two species also differ in the placement of their territories along the ridgeline; P. canadensis occupy territories in saddles while P. carnifex occupy those at peaktops. I show that this divergent spatial pattern is not maintained by competitive exclusion of either species by the other, and I discuss alternative explanations for their separate spatial distributions. Comparative data suggest that males are territorial because females restrict matings to within territories, and I discuss alternative hypotheses to explain this bias in female behavior.     

Structural characteristics and canopy dynamics of Tsuga canadensis in forests of the southern Appalachian Mountains, USA

Tsuga canadensis (L.) Carr. forests of the southern Appalachian Mountains are currently facing imminent decline induced by a nonnative insect pest, the hemlock woolly adelgid (Adelges tsugae Annand). To effectively manage these forest systems now and in the future, land managers need baseline data on forest structure and dynamics prior to large-scale Tsuga canadensis mortality. Most of our knowledge concerning the dynamics of Tsuga canadensis forests comes from more northern locations such as the Great Lakes region and New England and, therefore, may not pertain to the ecological systems found within the southern Appalachian Mountains. We examined the structure and canopy dynamics of four Tsuga canadensis forest stands within the Cataloochee watershed, in the far eastern part of Great Smoky Mountains National Park (GSMNP). We characterized the environmental settings and vertical forest layers, as well as the diameter and age-structures of each Tsuga canadensis forest stand. These environmental and structural data showed that there were indeed differences between forest stands with and without successful Tsuga canadensis regeneration. The two forest stands exhibiting successful Tsuga canadensis regeneration were located above 1,000 m in elevation on well-drained, moderately steep slopes and had the greatest canopy openness. Structural data from these two forest stands indicated a history of more continuous Tsuga canadensis regeneration. We also constructed disturbance chronologies detailing the history of canopy response to disturbance events and related these to Tsuga canadensis regeneration within each forest stand. Student t-tests adjusted for unequal variances indicated significant differences in the number of release events per tree between forest stands with and without successful Tsuga canadensis regeneration. While forest stands with successful Tsuga canadensis regeneration were more frequently disturbed by minor to major canopy disturbances, events of moderate intensity were found to be most significant in terms of regeneration. These data will be of value to land managers maintaining stands of Tsuga canadensis where treatment for hemlock woolly adelgid infestation has been successful. In areas where treatment is impractical or unsuccessful, land managers will be able to use these data to restore Tsuga canadensis forests after the wave of hemlock woolly adelgid induced mortality has passed. As of August 2008, Joshua A. Kincaid will be a member of the Environmental Studies program at Shenandoah University in Winchester, Virginia, USA     

Polyploidization-driven differentiation of freezing tolerance in Solidago canadensis

Solidago canadensis, originating from the temperate region of North America, has expanded southward to subtropical regions through polyploidization. Here we investigated whether freezing tolerance of S. canadensis was weakened during expansion. Measurement of the temperature causing 50% ruptured cells (LT₅₀) in 35 S. canadensis populations revealed ploidy-related differentiation in freezing tolerance. Freezing tolerance was found to decrease with increasing ploidy. The polyploid populations of S. canadensis had lower ScICE1 gene expression levels but more ScICE1 gene copies than the diploids. Furthermore, more DNA methylation sites in the ScICE1 gene promoter were detected in the polyploids than in the diploids. The results suggest that promoter methylation represses the expression of multi-copy ScICE1 genes, leading to weaker freezing tolerance in polyploid S. canadensis compared to the diploids. The study provides empirical evidence that DNA methylation regulates expression of the gene copies and supports polyploidization-driven adaptation to new environments.     

Drought affects the coordination of belowground and aboveground resource‐related traits in Solidago canadensis in China

Quantifying patterns of variation and coordination of plant functional traits can help to understand the mechanisms underlying both invasiveness and adaptation of plants. Little is known about the coordinated variations of performance and functional traits of different organs in invasive plants, especially in response to their adaptation to environmental stressors. To identify the responses of the invasive species Solidago canadensis to drought, 180 individuals were randomly collected from 15 populations and 212 ramets were replanted in a greenhouse to investigate both the response and coordination between root and leaf functional traits. Drought significantly decreased plant growth and most of the root and leaf functional traits, that is, root length, surface area, volume and leaf size, number, and mass fraction, except for the root length ratio and root mass fraction. Phenotypic plasticity was higher in root traits than in leaf traits in response to drought, and populations did not differ significantly. The plasticity of most root functional traits, that is, root length (RL), root surface area (RSA), root volume (RV), and root mass fraction (RMF), were significantly positively correlated with biomass between control and drought. However, the opposite was found for leaf functional traits, that is, specific leaf area (SLA), leaf area ratio (LAR), and leaf mass fraction (LMF). Drought enhanced the relationship between root and leaf, that is, 26 pairwise root–leaf traits were significantly correlated under drought, while only 15 pairwise root–leaf traits were significantly correlated under control conditions. Significant correlations were found between biomass and all measured functional traits except for leaf size. RV, root length ratio, RMF, total area of leaves, and LMF responded differently to water availability. These responses enable S. canadensis to cope with drought conditions and may help to explain the reason of the vast ecological amplitude of this species.     

River otter and mink occupancy dynamics in riparian systems

Semi-aquatic mammals are dependent upon streams and riparian areas, which are a product of the landscapes they drain. Both local stream morphology and surrounding land use are likely to have important influences on current occupancy of semi-aquatic mammals and potentially affect future geographic distributions. We identified aspects of the riparian system and stream structure at multiple scales that relate to the presence of river otter (Lontra canadensis) and mink (Neovison vison) to better understand how changing landscapes affect occupancy dynamics of these semi-aquatic mammals and to facilitate future monitoring and management. We estimated multi-season occupancy using 103 sites sampled over 6 seasonal sampling periods in southern Illinois, USA (44,526 km²) during 2012–2014. We hypothesized river otter and mink occupancy were related to multiple aspects of landscape and local habitat attributes including land cover, water availability, human disturbance, and stream characteristics. Occupancy of river otter was predicted by large stream size, less developed area near the stream site, and proximity to areas with reintroduced or remnant populations of river otter. Mink were more likely to occupy sites with small streams and decreased water availability near the site. However, top models for both species had low weights and high uncertainty for multiple variables. Habitat-based models may not be the best predictors of occupancy for these carnivores because they are more likely to respond to prey diversity or availability, but landscape changes that decrease natural water availability and increase human disturbance to the stream at the local scale are likely to negatively affect river otter. © 2019 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Spread of Elodea canadensis in Lake Baikal

In Lake Baikal Elodea canadensis Michx. was first observed at the end of the 1970's.Suggestions have been made as to the bringing of E. canadensis to Baikal by aquarists or by transport vehicles and transport together with fishes taken from lakes of the Urals where mass development of the plant was observed at the beginning of the present century. The spread of E. canadensis along Lake Baikal must be due to navigation, but natural factors also affect its spread.The quantitative biomass development of E. canadensis in various areas of the lake is reviewed, and discussed in relation to historical aspects of spread and regulation by environmental factors.The fast spread of E. canadensis, its high competitive quality and metabolic capacities for purifying sewage waters deserve attention.Expansion of E. canadensis may be referred to as a catastrophic phenomenon. Its effect has now covered practically the whole perimeter of Lake Baikal.     

Habitat fragmentation influences genetic diversity and differentiation: Fine‐scale population structure of Cercis canadensis (eastern redbud)

Forest fragmentation may negatively affect plants through reduced genetic diversity and increased population structure due to habitat isolation, decreased population size, and disturbance of pollen‐seed dispersal mechanisms. However, in the case of tree species, effective pollen‐seed dispersal, mating system, and ecological dynamics may help the species overcome the negative effect of forest fragmentation. A fine‐scale population genetics study can shed light on the postfragmentation genetic diversity and structure of a species. Here, we present the genetic diversity and population structure of Cercis canadensis L. (eastern redbud) wild populations on a fine scale within fragmented areas centered around the borders of Georgia–Tennessee, USA. We hypothesized high genetic diversity among the collections of C. canadensis distributed across smaller geographical ranges. Fifteen microsatellite loci were used to genotype 172 individuals from 18 unmanaged and naturally occurring collection sites. Our results indicated presence of population structure, overall high genetic diversity (H_E = 0.63, H_O = 0.34), and moderate genetic differentiation (F_ST = 0.14) among the collection sites. Two major genetic clusters within the smaller geographical distribution were revealed by STRUCTURE. Our data suggest that native C. canadensis populations in the fragmented area around the Georgia–Tennessee border were able to maintain high levels of genetic diversity, despite the presence of considerable spatial genetic structure. As habitat isolation may negatively affect gene flow of outcrossing species across time, consequences of habitat fragmentation should be regularly monitored for this and other forest species. This study also has important implications for habitat management efforts and future breeding programs.     

Teratological pollen of Circaea canadensis ssp. canadensis (Onagraceae: Circaeeae)

Pollen morphology of Circaea canadensis (L.) Hill ssp. canadensis collected from sites in Oklahoma differs from that described in earlier reports on this taxon. The samples we observed had poorly developed viscin threads, many with slender connecting points. In the equatorial zones between apertures there were randomly dispersed and elevated tectal components. These features may be due to arrested development since they are present in early stages of development in related taxa.     

Introduced Swedish Canada geese (Branta canadensis) have low levels of genetic variation as revealed by DNA fingerprinting

The Swedish, Finnish and Norwegian population of Canada geese (Branta canadensis), now amounting to some 30–50 000 birds, was founded by only five individuals. We used DNA fingerprinting to assess the level of genetic variability in minisatellite loci of Swedish Canada geese from two northern areas. For comparison, we estimated the minisatellite variability in lesser white-fronted geese (Anser erythropus), barnacle geese (Branta leucopsis) and a reintroduced stock of Canadian giant Canada geese (Branta canadensis maxima). The mean similarity between Swedish Canada geese was 0.76 ± 0.15, which is higher than recorded for any other natural bird population. The high similarity implies that a fourfold increase of homozygosity has taken place in this population. The probable cause for the loss of variation is the low number of birds originally introduced and a history of repeated translocations, leading to a sequence of founder events. As a consequence of the high similarity, it has not been possible to use DNA fingerprinting for determination of parenthood in the population studied.     

Tissue water relations of three chaparral shrub species after wildfire

Summary We compared the tissue water relations among resprouts and seedlings of three chaparral species during the first summer drought after wildfire. Two of the species, Rhus laurina and Ceanothus spinosus recover after fire by a combination of resprouting and seedling establishment (facultative resprouters), whereas a third species, Ceanothus megacarpus recovers by seedling establishment alone (obligate seeder). Our objectives were to document any differences in tissue water characteristics that might arise between resprouts and seedlings and to test the hypothesis that seedlings of obligate seeders develop more drought tolerant characteristics of their tissues than seedlings of facultative resprouters. We found that resprouts had much higher predawn values of water potential, osmotic potential, and turgor potentials than seedlings. Predawn turgor potentials of resprouts were 1.5 MPa through July and August when turgor potentials for seedlings remained near 0 MPa. During summer months, midday water potentials were 2 to 3 MPa higher for resprouts than seedlings and midday conductances of resprouts were two to five fold greater than those of seedlings. Even though resprouts did not experience severe water stress like seedlings, their tissue water characteristics, as determined by pressure-volume curve analyses, were similar by the peak of the drought in August. Further-more, the tissue water characteristics of seedlings from the obligate seeder, C. megacarpus, were similar to those of facultative resprouters — R. laurina, and C. spinosus. We attribute the observed differences in plant water status between resprouts and seedlings to differences in rooting depths and access to soil moisture reserves during summer drought. We conclude that the higher growth rates, photosynthetic performance, and survivorship of postfire resprouts are primarily a result of higher water availability to resprouting tissues during summer months. It appears that the greater seedling survivorship during summer drought observed for the obligate seeder, C. megacarpus, is not associated with more favorable tissue water characteristics.