Variable tree establishment in bauxite mine restoration in south-west Australia linked to rainfall distribution, seasonal temperatures and seed rain

Reasons for variable establishment of Jarrah (Eucalyptus marginata D. Don ex Sm.) and Marri (Corymbia calophylla (Lindl). K. D. Hill & L. A. S. Johnson) on restored forest sites after bauxite mining in south‐west Australia are not well understood. To refine restoration outcomes, we compiled tree seedling density establishment data from surveys of 654 previously mined sites restored between 1998 and 2017, and applied generalised linear models to discriminate the effects of 24 climatic and restoration practice variables. Final models explained 50% and 31% of the variation in Jarrah and Marri density, respectively. Broadcast seeding and fertiliser rates were positively related to seedling density. A more even rainfall distribution in the early wet season increased seedling density. However, persistent rain later in the wet season decreased density, possibly as a result of ripline soil saturation or ponding. Higher average daily maximum temperatures in the dry season decreased seedling density probably due to drought stress, but warmer daily temperature minima in both wet and dry seasons increased density. Seed rain from surrounding unmined forest was implicated as a significant, but highly variable, source of additional seed to restored sites. Restoration practices that influence soil moisture relations (tillage, depth and texture of returned soil), shallow burial of applied seed and timing of fertiliser application are likely to be important in refining restoration outcomes

The evolution of grasstree growth phenology: Questioning the fit of an established theory for Australia\u27s Mediterranean vegetation

Plants can be categorised by their growth response to temperature, and several studies have demonstrated that more than one thermal type is represented in Australian Mediterranean environments (e.g. Specht et al. 1981) Specht and colleagues (Specht and Dettmann 1995, Specht and Specht 1999) suggest that the overstorey species in Mediterranean Australia have undergone little change since the warmer early Tertiary and have retained a mesotherm (subtropical) growth rhythm with peak growth in late spring/summer. However, Specht and Dettmann (1995) explain that the understorey stratum has more recently evolved an intricate leaf distribution structure which helps to synchronise the growth of this stratum with the cool winter/spring, season of the Mediterranean climate (a microtherm rhythm). The intricate structure increases the plants boundary layer, impeding heat dissipation and effectively raises the temperature of the growing apices, compensating for the cooler environment. The grasstree Xanthorrhoea preissii Endl., from south-western Australia presents an unusual Mediterranean species that appears to be a poor fit for the theory described above

FREQUENCY UP-CONVERSION IN INTERACTING PHONON BEAMS IN LIQUID 4He

Nous avons étudié l'interaction due à l'intersection de faisceaux de phonons en fonction de la pression en utilisant comme détecteurs des jonctions tunnel supraconductrices A1. Des phonons de haute fréquence créés par l'annihilation de deux phonons de plus basse fréquence sont détectés à des pressions < 13 bars. La fréquence critique pour cette conversion vers le haut est bien définie et est en bon accord avec la valeur trouvée à partir de la désintégration de phonon via le processus à 3 phonons.The interaction between intersecting phonon beams in liquid 4He has been studied as a function of pressure using superconducting A1 tunnel junction detectors. For pressures < 13 bar we detect high frequency phonons which are created by the annihilation of two lower frequency phonons. The critical frequency for this upconversion is well defined and is in good agreement with the value found from phonon decay via the 3 phonon process

A < 0.1 µs RESPONSE TIME CARBON FILM BOLOMETER DETECTION SYSTEM

Nous avons obtenu un temps de réponse global d'environ ~ 50 ns pour un système de détection utilisant un bolomètre à film de carbone, par la modification du facteur de forme rectangulaire usuel et par l'utilisation d'un étage MOSFET à transformation d'impédance opérant à la temperature de l'hélium liquide.An overall response time ~ 50 ns is achieved for a carbon film bolometer detection system through the modification of the usual rectangular form factor and by the use of a MOSFET impedance transforming stage operating at liquid helium temperatures

Grasstree (\u3cem\u3exanthorrhoea preissii\u3c/em\u3e) leaf growth in relation to season and water availability

Water stress usually arrests growth of even the most deep-rooted species during summer drought in Mediterranean-type climates. However, scant evidence suggests that grasstrees may represent an unusual exception. We used weather data and plant water potential to investigate the relationship between leaf growth and season in the grasstree, Xanthorrhoea preissii Endl. (Xanthorrhoeaceae). Leaf production in two contrasting habitats revealed continuous annual growth, oscillating between maximum rates (2.5–3.2 leaves/d) in late-spring to autumn, to a minimum rate of 0.5 leaf/d during winter but never stopping. While the rate of leaf production during the fast-growth season was positively correlated with temperature above 17–18°C, leaf elongation commenced substantially earlier in the year (from 12°C). Leaf water potentials cycled annually, with predawn readings commonly measured as zero during winter–spring and as low as −1.26 MPa during summer, but never indicating stress by exceeding the turgor loss point. Leaf death was synchronized with summer drought. The fast (summer) growth period was characterized by rapidly fluctuating leaf production, particularly in banksia woodland, where plant growth reliably responded quickly to \u3e18 mm of rainfall. Within 24 h of 59 mm of simulated rainfall, grasstrees in banksia woodland showed a marked increase in water potential, and leaf production reached 7.5 times the controls, confirming their capacity to respond to temporary spasmodic summer rains. Rainfall was the best climatic variable for predicting woodland grasstree leaf production during summer, whereas leaf production of forest grasstrees was most closely correlated with daylength. This plastic response of grasstrees between seasonal weather extremes is relatively rare among other mediterranean floras, and has implications for a recently proposed technique for ageing grasstrees

Grasstree (\u3cem\u3exanthorrhoea preissii\u3c/em\u3e) recovery after fire in two seasons and habitats

To distinguish fire-stimulated growth from the underlying growth patterns imposed by season, we measured leaf production of Xanthorrhoea preissii Endl. (Xanthorrhoeaceae). We compared unburnt with spring- and autumn-burnt sites in forest and woodland habitats. Following fire, X. preissii responded with accelerated leaf production, regardless of season. Rapid leaf production during the initial flush of growth was partly at the expense of starch reserves in the stem, at least after autumn fire. Although this initial flush was relatively short-lived after fire in both seasons (12–32 weeks), the effect of fire on leaf production was sustained for up to 20 months, accompanied by a significant reduction in leaf longevity. Mean maximum leaf production rate was higher for spring-burnt grasstrees (up to 6.1 leaves day–1) than those burnt in autumn (up to 4.5 leaves day–1), associated with seasonally optimal growing conditions in late spring–early summer. Similarly, the timing of autumn burns in relation to declining temperature with the approach of winter appeared to dictate how rapidly grasstrees recovered. The consequences of fire season could have implications for the reproductive success of X. preissii

Re-establishing the cycad \u27macrozamia riedlei\u27 following mining

Alcoa of Australia has mined bauxite for the production of aluminium since 1963 in Western Australia\u27s northern Jarrah (\u27Eucalyptus marginata\u27) forest. While the company has made significant advances in its rehabilitation methods some plant species still pose a challenge in restoring native Jarrah forest vegetation (Koch 2007). The cycad \u27Macrozamia riedlei\u27 (Zamia), is a key species in the Jarrah forest, but is under-represented on rehabilitated sites (around 50/ha) compared with densities in adjacent unmined forest (around 1000/ha)

Gondwanan origin of the Dipterocarpaceae-Cistaceae-Bixaceae is supported by fossils, areocladograms, ecomorphological traits and tectonic-plate dynamics

There is disparity between the estimated time of origin of the ‘superclade’ Dipterocarpaceae sensu lato, that includes Sarcolaenaceae, Cistaceae, Pakaraimaea, Bixaceae, Cochlospermaceae and Sphaerosepalaceae, as determined by recent molecular phylogenies (100−85 million years ago, Ma) and its strongly tropical, South American-African-Madagascan-SE Asian distribution that indicates an older Gondwanan origin (&gt;110 Ma). We used several paleobiogeographic approaches, including recently reported fossil records, to explore the hypothesis that Dipterocarpaceae sl has a Gondwanan/early-Cretaceous origin.We created molecular phylogenies for this group, assigned each genus/family to the tectonic plate on which it is extant, and subjected the cladogram to areogram analysis. We also assessed ecological, mycotrophic and morphological traits, and global circulation patterns, as these might affect this group’s distribution.The initial analysis (omitting fossil evidence) showed that the crown of Dipterocarpaceae sl occurred concurrently on the South American and Madagascan plates. Including fossils from Africa and India changed this to a South American-African origin. Collectively, these origins represent NorthWest Gondwana with South America, Africa and Madagascar remaining conjoined until ≥105–115 Ma, setting the minimum age for this superclade with some evidence that it may be much older. We also show that the immediate ancestors of the three daughter lineages [Dipterocarpaceae- Sarcolaenaceae (in Africa/Madagascar, ≥115 Ma), Cistaceae- Pakaraimaea (South America/Africa/Eurasia, ≥105 Ma) and Bixaceae-Cochlospermum-Sphaerosepalaceae (South America/ Africa, ≥105 Ma)] also arose in NorthWest Gondwana.The immediate ancestors or basal species in Sarcolaenaceae, Sphaerosepalaceae, Dipterocarpaceae (both its subfamilies) and Bixaceae migrated from (South America)/Africa to Madagascar and we propose that the Dipterocarpoideae proceeded from Africa to India while still linked to Madagascar. In addition, much subsequent diversification of this superclade has occurred on the Eurasian, Indian, SE Asian (Sunda) and North American plates post-Gondwanan breakup.This long vicariant history is supported by fossil, ecological, mycotrophic and morphological traits, and global circulation patterns that show negligible propensity for transoceanic dispersal to explain this clade’s wide intercontinental distribution.We conclude that all these areocladogram/plate-breakup/ ecomorphological/circulation features are consistent with a Gondwanan/early-Cretaceous (&gt;115 Ma) origin for the Dipterocarpaceae-Cistaceae-Bixaceae superclade plus its three daughter clades. Future analyses at the species level, exploring alternative diversification dates from both fossils and plate-tectonic dynamics, are needed to refine these findings