Temporal and spatial patterns in emergence and early survival of perennial plants in the Sonoran Desert

Seedling emergence and survival of 15 perennial species were studied for six years in a 557-m² permanent plot at Tumamoc Hill, Arizona, USA, an ungrazed site in the northern Sonoran Desert. The minimum rain required for germination and emergence ranged from 17.5 to 35.6 mm. Few species emerged in every year of the study. First-year survival averaged across all 15 species was 3.7%; only 0.1% of seedlings lived as long as four years. The odds of survival in the first year improved with increased rain. About three times as many seedlings died from predation as desiccation. In 2-m² subplots, mortality of three woody species in the first 30 days after emergence appeared to be independent of seedling density. Short-, moderate-, and long-lived species displayed distinct survival strategies. Long-lived species compensated for generally poor seedling survival by frequent germination and emergence. Moderate-lived species exhibited highly episodic germination and emergence, a potentially risky behavior that might have been offset to some extent by relatively good long-term survival. Short-lived species had the highest seedling survival. Because these species can bloom in their first year, good early survival meant that some individuals were able to reproduce before they died.     

TREE SEEDLING EMERGENCE ON INTERACTIVE TEMPERATURE AND MOISTURE GRADIENTS AND IN PATCHES OF OLD-FIELD VEGETATION

Seeds of tree species commonly invading old-fields (Fraxinus americana, Gleditsia triacanthos, Morus rubra, Platanus occidentalis, and Prunus serotina) were germinated at eight temperatures from 5 C to 40 C, with six moisture levels (2% to 18% gravimetric moisture content) at each temperature. For most species, total seedling emergence and emergence rate exhibited approximate bivariate Gaussian response surfaces. Emergence of all species, except Gleditsia, was much more sensitive to differences in temperature than to differences in moisture. Species differed considerably in their response breadths across the interactive gradients, with moisture response bearing little relationship to temperature response. Seeds of Acer saccharum, Crataegus mollis, Fraxinus americana, Gleditsia triacanthos, Morus rubra, and Prunus serotina were sown into old-field vegetation patches dominated by eight different plant species, across three different soils. Acer and Morus emergence exhibited no significant differences among vegetation patches. Emergence of other tree species differed among patch types, but identity of the vegetation (often early successional) most conducive to emergence typically varied from year to year. Emergence of most species responded more strongly to vegetation than to soil series. High Fraxinus and Prunus emergence was associated with dampened temperature ranges, while high Crataegus emergence was associated with low amounts of plant litter. Despite great variability, vegetation differences can predict tree seedling emergence better than do year-to-year or soil differences. Extrapolations from the laboratory experiments predicted approximate levels of overall seedling emergence in the field, but prevailing temperatures and moisture differences among plant neighborhoods alone were not sufficient to explain observed differences in seedling emergence among these patches.     

The life histories, trophic relations and production of Stenoperla prasina (Plecoptera) and Deleatidium sp. (Ephemeroptera) in a New Zealand river

The life history, feeding relations and production of the stonefly Stenoperla prasina were studied for 16 months in the Selwyn River, South Island, New Zealand. Larval life is about 1 year with growth occurring in all months. Although emergence of adults was observed only from November to February, egg hatching probably occurred over an extended period as small larvae were present in most months. Larvae were mainly carnivorous except in early instars when most guts contained detritus. Larvae of a mayfly, Deleatidium sp. and a chironomid, Orthocladiinae sp. were the most important prey items. In April of two successive years the guts of most stoneflies examined were filled with diatoms (Gomphonema sp.) and filamentous algae which were abundant in the river only at these times. Algal feeding was not found in other months. Larvae of the main prey species, Deleatidium, were present in all months, being most abundant in summer and declining in numbers during winter. Maximum emergence occurred in March and April. The annual cycle of Deleatidium was diflicuit to interpret as larvae of all sizes were present in all months. Two generations probably occurred in a year, a fast-growing summer generation and a slower-growing and less synchronized winter generation. Mean annual standing biomass, annual production and turnover ratios (P/B) were calculated for both species. The latter were within the range of values given by Waters (1969) but may be subject to error from several sources. Shortcomings in the method used to estimate production are discussed.     

Seasonal dynamics of a mayfly (Insecta: Ephemeroptera) community in a Laurentian stream

The purpose of our study was to compare on a seasonal basis the emergence, the drift and the benthos on a short and uniform section (18.5 m)of a stream in the Laurentian Hills of Québec. Nineteen species occurred on this stretch, but only six were abundant: Leptophlebia cupida (Say), Habrophlebia vibrans Needham, Baetis pygmaeus (Hagen), Eurylophella verisimilis (McDunnough), Stenonema modestum (Banks), and Stenonema vicarium (Walker). Emergence was monitored for 5 years; densities differed from one trap to the next, as did species dominance, but total densities were similar. These data conform to Illies' rules of constancy and harmony. Nymphal densities were high (mean of 16000 m⁻²). The dominant species were univoltine, except H. vibrans (semivoltine), and B. pygmaeus (polyvoltine). Larger species contributed relatively more to the production of the reach despite their low densities than did the more abundant smaller species, especially those with long life cycles. Drift was low during most of the year, except during spring and species composition varied considerably. A comparison of the three data sets (emergence, drift and benthos) shows a general agreement for the less abundant species, but for three of the dominants, H. vibrans, L. cupida and E. verisimilis , movements of individuals to and from the reach at various times in the life cycle (adult flight, nymphal drift and migration) must be taken into account in order to correlate the data. None of the methods alone gives a satisfactory picture of the community structure, each is to some extent misleading and needs to be used in conjunction with the others; the conflicting results obtained from the data sets often reveal interesting life history traits which otherwise would not have been detected.     

Can Establishment Characteristics Explain the Poor Colonization Success of Late Successional Grassland Species on Ex‐Arable Land?

Abstract Many grassland restoration projects on former arable land face problems because early successional grassland species establish vigorously and persistently but late successional grassland species fail to establish. Differences in establishment characteristics of early and late successional species might provide an explanation for the failure of many late successional species to colonize grasslands on ex‐arable land. I examined whether early and late successional species had different establishment rates in the initial years of a grassland succession, whether a specific establishment stage (seedling emergence, mortality or growth) could be identified as the key process controlling establishment, and what management would enhance the establishment of late successional grassland species. Seeds of three early and three late successional species were sown separately in ex‐arable plots with bare soil, 1‐year‐old vegetation, and 2‐year‐old vegetation. Emergence, mortality, and seedling growth were monitored for 1 year. Early successional species established successfully in the bare soil plots but failed to establish in plots with 1‐ and 2‐year‐old vegetation. Late successional species showed either lower establishment rates in the younger succession stages or decreased establishment with succession that nevertheless resulted in significant establishment in the oldest plots. Seedling emergence proved to be the key factor determining the establishment pattern of early and late successional species. In absolute numbers, emergence of late successional species was, however, similar or higher than that of early successional species, even in the earliest succession stage. The poor establishment of late successional species on former arable land could therefore not be explained solely by differences in establishment characteristics between early and late successional grassland species. Competitive processes between early and late successional species later in the life cycle probably play an important role. The results do point out that establishment of late successional species can be promoted by creating vegetative cover from the start of the restoration effort.     

Effects of emergence phenology, taxa tolerances and taxonomic resolution on the use of the Chironomid Pupal Exuvial Technique in river biomonitoring

1. We studied chironomid communities of four rivers in south‐eastern Finland, differing in their water quality, during summer 2004 using the Chironomid Pupal Exuvial Technique, CPET. The aims of the study were to (i) test the adequacy of the generic‐level identification in the CPET method, (ii) define the emergence patterns of chironomid taxa classified as intolerant to organic pollution, (iii) assess the tolerance levels of intolerant chironomids and (iv) identify taxa most indicative of good water quality. 2. Procrustean rotation analysis indicated very strong concordance between the ordinations using either species or genus‐level data, suggesting that generic‐level identification of chironomids is adequate for biomonitoring based on CPET. However, when only a few taxa occur in great numbers, it may be advisable to identify these to the species level, especially if these taxa are important indicators of the impact in question. 3. The detection of a particular species may require accurate timing of sampling, whereas a species‐rich genus might be detected throughout a season. Given that the emergence of chironomid species may vary from year‐to‐year and between sampling sites, community differences detected at the species level may be related to between‐site variation in species’ emergence patterns rather than true differences in species composition. 4. Indicator species analysis (IndVal) showed that the distribution and abundance of intolerant chironomid taxa differed strongly among the studied rivers. Some of the intolerant taxa were restricted to unimpacted conditions, whereas others occurred mainly in impacted rivers. Thus, the indicator status of some genera (e.g. Eukiefferiella, Parametriocnemus, Stempellinella and Tvetenia) needs reassessment.     

Reproductive senescence in a cooperatively breeding mammal

1. Senescence (or 'ageing') is a widespread and important process in wild animal populations, but variation in ageing patterns within and between species is poorly understood.
2. In cooperatively breeding species, the costs of reproduction are shared between breeders and one or more helpers. The effects of ageing in breeders may therefore be moderated by the presence of helpers, but there have been very few studies of senescence patterns in natural populations of cooperative breeders.
3. Here, we use 13 years of data from a long-term study population of wild meerkats ( Suricata suricatta ) to investigate age-related changes in several traits known to be key components of reproductive success in females of this species.
4. Four of the six traits studied exhibited significant declines with age, indicating senescence. Litter size, the number of litters produced per year and the number of pups that survived to emergence from the natal burrow per year all increased with female age up to a peak at c. 4 years, and declined steeply thereafter; the mean pup weight at emergence in a given litter declined steadily from age zero.
5. These results provide the first evidence of reproductive senescence in a wild population of a cooperatively breeding vertebrate. Breeding success declined with age despite the sharing of reproductive costs in this species, but further study is needed to investigate whether helping affects other aspects of senescence, including survival.     

Seed Dynamics in Relation to Gaps in a Tropical Montane Rainforest of Hainan Island, South China: (Ⅱ) Seed Bank

Spatial and temporal patterns of seed bank dynamics In relation to gaps in an old growth tropical montane rainforast of Hainan Island, South China, were studied over two consecutive years. From June 2001 to June 2003, soil seed bank sampling blocks were taken near each of the four sides of each seed trap and immediately put into a nursery for observation of seedling emergence dynamics in four seasons (each experiment in each season). The abundances of seedlings that emerged from seed banks showed the trend of vine functional group (VFG) > shrub functional group (SFG) > tree functional group (TFG) > herb functional group (HFG), but the trend in species richness of seedlings that emerged from the soil seed banks was TFG > VFG > SFG > HFG. The abundances of seedlings that emerged from seed banks in the three gap zones showed no significant differences, but significant differences did exist for the species richness. The time of sampling or seasons of experiments had significant influences on both the species richness and seedling abundances. The seedling emergence processes of each experiment all revealed the unimodal patterns. Few emergences occurred 1 year after each experiment. Compared with those under closed canopies, the recruitment rates from seed to seedlings and from seedlings to saplings in gaps were higher, but the mortality rates from saplings to big trees were also higher in the gaps.     

Clusiidae (Diptera) from log emergence traps in the Yambaru, a subtropical forest of Japan

Five species of Clusiidae (Diptera), Craspedochaeta biseta (Hendel), hendeli a plumosa (Sasakawa), Heteromeringia sexramifera Sueyoshi, Phylloclusia yambarensis sp. n., and Sobarocephala uncinata Sueyoshi, were collected from log emergence traps installed in a subtropical forest of Japan from February 2006 to February 2008. Craspedochaeta biseta (Hendel) was newly recorded in Japan. Wood debris was gathered from 1–22 year old secondary stands managed by the improvement cutting of natural forest (ICNF) and unmanaged stands, and categorized by stage of decay and size, and then enveloped in fine net bags (emergence trap). In total, 84 clusiid adults were obtained. Most were reared from wood debris in an advanced stage of decay and from 2 year old or older managed and unmanaged forest stands, although P. yambarensis was reared from wood debris in an early stage of decay and from 1 year old forests after cuttings. Log emergence traps effectively sample clusiids, taking both sexes in approximately equal numbers. Specimens collected by this trap may resolve the difficulty in identifying male and female specimens of several clusiid species that show sexual dimorphism.     

Chironomidae (Diptera) of peatlands in northwestern Ontario, Canada

Eighty-four species of Chironomidae were collected, using emergence traps, from three poor fens located in the Experimental Lakes Area (ELA) of northwestern Ontario. Of these, 37 were considered to be true peatland fauna. The majority (23) of the peatland species are new North American or Canadian records and, of these, 10 are previously undescribed. Numbers m⁻² yr⁻¹ emerging from the fens were similar to neighbouring lakes but biomass (mg) m⁻² yr⁻¹ emerging was much less, indicating the small average size of the fen chironomids. Emergence began in early May and was virtually completed by late July-early August in all three years of the study. Most of the emergence occurred early in the season. Eight species accounted for ≥90% of the emergence. Five of these, Gymnometriocnemus (R.) acigus Saeth., Doithrix villosa Saeth. and Subl., Pseudorthocladius (s.s.) destitutus Saeth. and Subl., P. (s.s.) curtistylus (Goetgh.), and Paramerina nr. smithae (Subl.) had univoltine life cycles and relatively stichronous emergences. Pseudosmittia forcipata (Goetgh.) was bivoltine, and Limnophyes minimus (Meig.) and Smittia nr. nudipennis Geotgh. had protracted emergence periods that made voltinism difficult to determine. Characteristic features of the chironomid fauna of peatlands at ELA are discussed. The general applicability of these features to peatlands, and needs for further research in these neglected but extensive Canadian habitats are considered.     

Entrainment by different environmental stimuli in the frugivorous bats from the Lonar crater

The timings of emergence at dusk and return at dawn of a colony of frugivorous bats Rousettus leschenaulti, roosting in a temple ruin of the Lonar crater (19.97°N, 76.52°E), were investigated at 10-day intervals for one year. The onset of emergence occurred about 18 min after sunset throughout the year irrespective of the prevailing light intensity or temperature but the end of returning activity occurred at a fixed light intensity of about 4 lux irrespective of the time of sunrise or prevailing temperature. Apparently, the evening oscillator controlling the onset of emergence was set by the sunset, i.e. the lights-off stimulus of the natural light - dark cycles, while the morning oscillator controlling the end of activity was set by a certain invariant threshold intensity of the dawn twilight.     

Interannual variation in precipitation and other planting conditions impacts seedling establishment in sown plant communities

Ecological restoration can reverse biodiversity loss worldwide, yet restoration goals and outcomes vary widely, which limits this potential. Divergent restoration outcomes may stem from variation in conditions at the outset of restoration, but empirical evidence is lacking and typically confounded with site differences. Additionally, precipitation is usually cited as the source of this variation, although a wide range of conditions can vary annually. We tested for effects of planting year on seedling establishment by installing identical restorations in three different years. Within those years, we manipulated rainfall with rain‐out shelters to disentangle the effects of precipitation from other annually variable conditions. Additionally, we tested whether increasing seed mix richness buffers against adverse planting conditions. For the first growing season after planting, we followed emergence and survival of sown prairie species and nonsown weed species to determine how planting year conditions influence an establishing plant community, if at all. We found that seedling establishment differed across planting years and precipitation treatments, and that varying emergence patterns by species led to differences in the composition of the first‐year community. We also found significant variation in sown species establishment across years when precipitation was held constant, illustrating the previously overlooked role of nonprecipitation drivers on planting year effects. Higher seed mix richness did not consistently improve establishment of sown species under different planting conditions. This research provides important experimental evidence for effects of interannual variation in planting conditions on first‐year establishment. Future work will examine how these initial changes affect longer‐term assembly dynamics.     

Waterproofing Topsoil Stockpiles Minimizes Viability Decline in the Soil Seed Bank in an Arid Environment

Topsoil is a valuable resource for revegetation of mine sites as it contains seeds of plant species indigenous to the local environment. As mine site restoration is undertaken after the completion of mining, it is a common practice to stockpile topsoil in preparation for restoration activities. While many studies have found a decrease in seedling emergence with increasing stockpile age in temperate regions around the world, a few examine the effect of stockpile age on topsoil seed bank and seedling recruitment in arid environments. Seed longevity is promoted under dry conditions whereas viability loss is increased under warm and moist conditions. Here in a study in Australia's Great Sandy Desert, the effect of topsoil storage age and method of storing topsoil (under‐cover and exposed) on seedling recruitment was examined for a major gold mining site. There was a trend for lower seedling emergence (68% lower) and species richness (30% lower) from topsoil stored for 2 years than from topsoil direct returned and topsoil stored for 1 year. Seedling emergence from topsoil stockpiled for 2 years was more than 3.5‐fold higher from covered topsoil stockpiles than uncovered topsoil stockpiles. For two ecologically dominant species, after 2 years of storage, seedling emergence of the grass Triodia basedowii was 13% of direct returned topsoil and seedling emergence of the shrub Acacia stellaticeps was 68% of direct returned topsoil. The implication of the decline in seedling emergence from topsoil stockpiling on mine site revegetation in a biodiverse arid region is discussed.     

Delayed post-fire seedling emergence linked to season: a case study with Leucopogon species (Epacridaceae)

In many fire-prone habitats around the world, natural fire regimes have shaped the evolution of the associated flora. Critical life history stages are often linked to fire in species that occur in these fire-prone habitats but many species are unstudied. We investigated seedling emergence patterns over time, after several fires in south-eastern Australia, for three obligate seeders in the Genus Leucopogon (Family Epacridaceae): L. setiger, L. esquamatus and L. exolasius. Fixed quadrats were monitored for 12 to 30 months for newly emerged seedlings, both after fire and in unburnt L. exolasius and L. esquamatus habitats. There was a flush of seedling emergence in the first year after fire for all three Leucopogon species, with smaller pulses recorded in subsequent years. Time elapsed between fire and the onset of emergence differed between fires, but not between Leucopogon species. Whatever the timing of the fire, seedling emergence was restricted to the late autumn and winter periods, coinciding with emergence in unburnt habitat. This contrasts with patterns of emergence previously reported for other taxa, and also in this study, where emergence of the Leucopogon species after fire was delayed compared with co-occurring species in other genera. Our results suggest that seasonal factors are important to the germination ecology of these species and that combinations of fire-related and seasonal factors are necessary to maximise germination. Rainfall has a non-seasonal pattern in the study region and seasonal emergence post-fire has not previously been recorded. The magnitude of delay to emergence of species with seasonal emergence patterns will be determined by the season of fire but not by a seasonal pattern of rainfall in the post-fire year. A shift of the peak fire season could increase this delay, possibly affecting plant population recovery. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mating Behavior of Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae): Potential for Outbreeding in a Predominantly Inbreeding Species

The mating behavior of the quasi-gregarious egg parasitoid Trissolcus basalis (Wollaston) was investigated under field conditions. Trissolcus basalis has female-biased sex ratios and is a protandrous species, with males emerging 1–2 days before females. Males competed aggressively for control of the egg mass, with one male assuming dominance and control of the egg mass, although changes in dominance occurred at least once on each egg mass observed. Typical mating behavior involved the dominant male mating his sisters immediately upon their emergence from the egg mass. These behaviors are characteristic of an inbreeding species that manifests local mate competition. However, several aspects of the mating behavior of T. basalis are inconsistent with that of an inbreeding species. Over 18% of emerging females were not mated by the dominant male upon emergence, 13% of females were not observed to be mated at all and may have left their natal site as virgins, 25% of females were mated multiple times and sometimes by multiple males, females remained near the natal site for up to several hours after emergence before emigrating, and males dispersed away from the natal site during female emergence. Trissolcus basalis may be a predominantly inbreeding species but its emergence and mating behavior suggest that low-frequency outbreeding is also likely to occur.     

Fire and seedling population dynamics in western Oregon prairies

Abstract. Through an experiment in three prairie vegetation types in western Oregon, USA the effect of prescribed fire on the timing and rates of seedling emergence and mortality was examined. Seeds of common exotic and native prairie species were sown into burned and unburned plots in late September, 1995. Emerged seedlings were censussed the following winter, early spring and late spring. Results indicated that spring population levels could not be forecast by fall seedling flushes, as winter survival was important in seedling establishment. The bulk of emergence for all grass and annual forb species occurred in the fall, followed by low to severe winter mortality. Perennial forbs were more variable in emergence times but, once emerged, perennial forb seedlings were likely to become established. Burning caused a statistically significant increase in seedling accumulation through emergence and survival in 11 of 23 cases. Burning improved seedling winter survival for most grass and short‐lived forb species and increased emergence of perennial forb species. These patterns were most conspicuous on the two sites dominated by exotic species, where burning significantly improved the accumulation of seedlings from most native species tested. Thus, prescribed burning might be a useful restoration tool in these communities. In contrast, two of the three species increased by burning in the native bunchgrass site were exotic pest plants, suggesting that fire should be prescribed with caution.     

Potato virus Y reduction by straw mulch in organic potatoes

Potato virus Y (PVY) is transmitted non-persistently by winged morphs of many aphid species and is a major problem in seed potato production. In order to evaluate the potential of straw mulch applications (4–5 t ha⁻¹) and presprouting on PVY reduction, small scale organically managed field experiments were carried out in Northern Hessen, Germany, over 3 yr. In all years mulching significantly reduced aphid infestation on leaves as well as PVY incidence in tubers. For the effect of presprouting the temporal coincidence of two factors was crucial – crop emergence and aphid flight activity. Presprouting decreased PVY incidence when in the phase of early crop emergence aphid spring flight activity was low, but increased it, although not significantly, when prominent aphid flight peaks occurred in this critical period. Straw mulch was most effective when vector pressure was concentrated early in the year acting as a PVY protectant for young plants. In later growth stages its effect declined gradually with increasing ground coverage of the crop. Combined mulching and presprouting had a synergistic, complementary effect on reduction of PVY incidence. In an on-farm experiment in 2001 scaling up the area mulched stepwise from 100 m² to 900 m² consistently kept aphid infestation at reduced levels.     

Vulnerability of phenological synchrony between plants and pollinators in an alpine ecosystem

The relationship between flowering phenology and abundance of bumble bees (Bombus spp.) was investigated using 2 years of phenological data collected in an alpine region of northern Japan. Abundance of Bombus species was observed along a fixed transect throughout the flowering season. The number of flowering species was closely related to the floral resources for pollinators at the community scale. In the year with typical weather, the first flowering peak corresponded to the emergence time of queen bees from hibernation, while the second flowering peak corresponded to the active period of worker bees. In the year with an unusually warm spring, however, phenological synchrony between plants and bees was disrupted. Estimated emergence of queen bees was 10 days earlier than the first flowering date owing to earlier soil thawing and warming. However, subsequent worker emergence was delayed, indicating slower colony development. The flowering season finished 2 weeks earlier in the warm-spring year in response to earlier snowmelt. A common resident species in the alpine environment, B. hypocrita sapporoensis, flexibly responded to the yearly fluctuation of flowering. In contrast, population dynamics of other Bombus species were out of synchrony with the flowering: their frequencies were highest at the end of the flowering season in the warm-spring year. Therefore, phenological mismatch between flowers and pollinators is evident during warm years, which may become more prevalent in a warmer climate. To understand the mechanism of phenological mismatch in the pollination system of the alpine ecosystem, ground temperature, snowmelt regime, and life cycle of pollinators are key factors.     

Life-cycles of some invertebrate taxa in a small pond together with changes in their numbers over a period of three years

1. Monthly quantitative samples of the invertebrate fauna (except Protozoa) in a small pond were taken over a period of three years. During one year, insect emergence traps were in operation. Water temperatures were recorded during the investigation.
2. The most abundant organisms in the pond were Phaenocora typhlops, Limnodrilus hoffmeisteri and Chaoborus crystallinus. Certain species of Micro-Crustacea and Chironomidae were also abundant but these groups have been dealt with elsewhere (see p. 66). Dendrocoelum lacteum, Polycelis nigra, Helobdella stagnalis, Lumbriculus aariegatus, Tubifex tubifex, Planorbis complanatus, and Asellus meridianus also occurred in considerable though lower numbers; other species occurred in low numbers.
3. The life-cycles and changes in numbers of the more numerous species are considered. The life-histories of D. lacteum, P. nigra, H. stagnalis, P. complanatus, A. meridianus are in agreement with published information. P. typhlops is seasonal in occurrence, being active from May to Sept. inclusive. Times of emergence of adults of various insect species agree with information available in the literature.
4. The life-cycle of L. hoffmeisteri in the pond is as follows: young worms hatch in spring/summer and form the bulk of the population from April to July/Aug; they mature from Aug. onwards and breeding starts in earnest from Feb./March. The life-cycle of T. tubifex is as follows: breeding starts in Feb., recruitment of young takes place from April till June, and these start to mature in Nov./Dec. It is not certain if some animals which breed in the spring/early summer survive to breed the following year.
5. The life-cycle of C. crystallinus appears to be as follows: first instars present from May to Oct., second instars from May to Dec., third instars from June till following Jan., fourth instars all the year round, pupae from May till Aug., and eggs from May to Sept. Adult emergence takes place from late April till mid-Sept.
6. A six-week drought in Oct/beginning Nov. in the second year of the investigation caused considerable mortality in most species, but most survived with only a few exceptions.

     

First‐year seedlings and climate change: species‐specific responses of 15 North American tree species

Species will respond individually to climate change and this poses a challenge for modeling climate–vegetation dynamics using broader taxonomic or biogeographical classifications. Additionally, responses to climate and environmental conditions may shift with ontogeny, further complicating efforts to understand the likely rates and directions of vegetation change. We measured emergence, leaf‐out rate, growth, and survival of first‐year seedlings in response to warming, precipitation regime shifts, and seedbed condition (leaf litter presence/absence). We grouped species into three levels of organization (species‐specific, biome‐level and broad taxonomic group) and hypothesized that most metrics of seedling performance would be best described by species‐specific models, as even similar species may respond in vastly different ways to global change. Results showed that the species‐specific model was the best fit for emergence and development rates, whereas growth and survival could be captured through broader groupings, with the broadleaf temperate group exhibiting the greatest growth and conifers the shortest survival times. The sign and magnitude of response to climate and seedbed condition varied with treatment combinations and metric of performance. For example, seedlings grew more in response to warming, but conditions too dry or too wet limited this positive response. Also, warmer temperatures generally increased emergence, development, and growth, but decreased survival, whereas leaf litter presence decreased emergence and slowed development, but increased survival. The results presented here are for first‐year seedlings and in many cases the responses are different from other studies using older plants. Future research and climate vegetation modeling needs to assess performance at multiple development stages and determine where key bottleneck phases for population growth occur for individual species.