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Abstract Plant phenology is not only manifested in the seasonal timing of vegetative and reproductive processes but also has ontogenetic aspects. The adaptive basis of seasonal phenology has been considered mainly in terms of climatic drivers. However, some biotic factors as likely evolutionary influences on plants’ phenology appear to have been under‐researched. Several specific cases of putative biotic factors driving plant phenology are outlined, involving both herbivores and pathogens. These illustrate the diversity of likely interactions rather than any systematic coverage or review. Emphasis is on woody perennials, in which phenology is often most multifaceted and complicated by the ontogenetic aspect. The complete seasonal leaf fall that characterizes deciduous plants may be a very important defense against some pathogens. Whether biotic influences drive acquisition or long‐term persistence of deciduousness is considered. In one case, of leaf rusts in poplars, countervailing influences of the rusts and climate suggest persistence. Often, however, biotic and environmental influences likely reinforce each other. The timing and duration of shoot flushing may in at least some cases contribute to defenses against herbivores, largely through brief periods of “predator satiation” when plant tissues have highest food value. Wide re‐examination of plant phenology, accommodating the roles of biotic factors and their interplays with environments as additional adaptive drivers, is advocated toward developing and applying hypotheses that are observationally or experimentally testable.

Seasonal phenology is expressed in the annual rhythms of growth and quiescence, which may range from being sharply defined to weakly quantitative. These rhythms, both vegetative and reproductive, are a key aspect of a plant’s survival strategy. They enable the plant to both survive seasonal stresses and take advantage of favourable conditions, while making pollination efficient through synchronised flowering. Maturation in woody perennials causes some ontogenetic modulation of seasonal phenology. Shoot phenology is driven by various environmental cues, notably temperatures and daylength, with shoot extremities often being prime receptors. The phenology of shoot extremities is in turn seen as a strong driver of cambial activity, which itself is an aspect of shoot phenology and the basis of stem diameter growth. The aspects of cambial activity reflecting hoot–tip phenology primarily involve the timing of xylem formation and the anatomical and physical properties of xylem cells. The actual amount of diameter growth, however, is governed much more by other factors, notably the growth potential of the species, the space for the tree to grow in, and how favourable local conditions are for growth. Somehow, all tree species allocate resources to shoot extension and diameter growth to represent viable adaptive strategies, although there is no identified role of phenology per se in such allocation. Among species, Pinus radiata is extremely important commercially, largely through a high growth potential that reflects distinctive phenology. Much research on the species provides a basis for linking its phenology and shoot–tip architecture to seasonal timing of diameter growth and fine details of within-ring variation in xylem cell properties. This provides a baseline for comparison with many other tree species, conifers and hardwoods. Selected examples are considered to illustrate the range of adaptive strategies. Regulation of diameter growth and internal variation in wood properties reflects the response to competitive pressures. Modifying the regulation to optimise wood production and quality poses a great challenge for future domestication.

Plantation forestry is now an imperative to meet wood requirements efficiently on the finite land available for wood production. Three main determinants of profitability are productivity, price per unit of wood harvested, and harvest age (the sooner the better). The first two are largely self-evident, while reducing harvest age lowers the effective cost of growing wood. Among these determinants, however, are strong interplays which include trade-offs. Key trade-offs involve adverse genetic correlations between various wood properties and growth-rate variables, and adverse effects on the wood quality of silvicultural interventions that raise site productivity and/or reduce harvest age. Moreover, the adverse effects of silviculture on wood properties tend to be accompanied by heightened expressions of genetic variation in wood properties. The trade-offs involve both increasing the percentage of corewood (‘juvenile wood’) and some more direct effects on wood quality. The pervasiveness of the trade-offs, and the heightened genetic expression, accentuate the call for genetic selection to defend wood quality. Such selection, however, will entail some costs in the appropriate emphasis on breeding for productivity. In this paper we review these issues, identify gaps in research information and offer guidance for tree breeders and silviculturists. While radiata pine is the special case, the applicability to some other species is briefly discussed.

We investigate the forces and atmosphere-ionosphere coupling that create atmospheric dynamo currents using two rockets launched nearly simultaneously on 4 July 2013 from Wallops Island (USA), during daytime Sq conditions with ΔH of -30 nT. One rocket released a vapor trail observed from an airplane which showed peak velocities of >160 m/s near 108 km and turbulence coincident with strong unstable shear. Electric and magnetic fields and plasma density were measured on a second rocket. The current density peaked near 110 km exhibiting a spiral pattern with altitude that mirrored that of the winds, suggesting the dynamo is driven by tidal forcing. Such stratified currents are obscured in integrated ground measurements. Large electric fields produced a current opposite to that driven by the wind, believed created to minimize the current divergence. Using the observations, we solve the dynamo equation versus altitude, providing a new perspective on the complex nature of the atmospheric dynamo.

Plasma escape from the high‐latitude ionosphere (ion outflow) serves as a significant source of heavy plasma to the magnetospheric plasma sheet and ring current regions. Outflows alter mass density and reconnection rates, hence global responses of the magnetosphere. A new fully kinetic and semi‐kinetic model, KAOS (Kinetic model of Auroral ion OutflowS), is constructed from first principles which traces large numbers of individual O+ ion macro‐particles along curved magnetic field lines, using a guiding‐center approximation, in order to facilitate calculation of ion distribution functions and moments. Particle forces include mirror and parallel electric field forces, a self‐consistent ambipolar electric field, and a parameterized source of ion cyclotron resonance wave heating, thought to be central to the transverse energization of ions. The model is initiated with a steady‐state ion density altitude profile and Maxwellian velocity distribution and particle trajectories are advanced via a direct simulation Monte Carlo scheme. This outlines the implementation of the kinetic outflow model, demonstrates the model's ability to achieve near‐hydrostatic equilibrium necessary for simulation spin‐up, and investigates L‐shell dependent wave heating and pressure cookers scenarios. This paper illustrates the model initialization process and numerical investigations of L‐shell dependent outflows and pressure cooker environments and serves to advance our understanding of the drivers and particle dynamics in the auroral ionosphere. Key Points: A new model, KAOS (Kinetic model of Auroral ion OutflowS), is introduced for studying ionospheric outflows from first principlesWe quantify dependence of upflowing/outflowing ion distributions on parameters pertaining to the characterization of pressure cookersMagnetospheric potential structures may transport highly transversely energized ion distributions to ionospheric altitudes [ABSTRACT FROM AUTHOR]

Agrarian change affects the supply and demand of ecosystem services (ES) by reducing the extent of natural ecosystems. Agricultural intensification can lead to changes in land covers and livelihood opportunities and it remains unclear how such changes align or misalign with the desires of local communities. Using participatry mapping, we assessed ES uses and desires of Indigenous people and local communities provided by different land cover types along a gradient of agricultural intensification (forest subsistence, agroforestry mosaic, and monoculture and market-dependence) in West Kalimantan, Indonesia. We found that mapped ES use diversity was highest in the forest-dependent zone and lowest near monoculture agricultural systems. The expressed ES uses and desires varied greatly among land cover types amidst loss of old-growth forest and greater reliance on secondary forest and shrub land. The spatial analysis showed that high priority areas of ES use was related to access in the landscape, demonstrating the importance of attending to place-based social values in ES assessments. From this study, we call for a people-centric spatial modelling approach to address the divergence of social and cultural ES values associated with land covers under different intensification contexts. Participatory mapping clarifies the ES desires of local communities, which state policy often fails to address. We recommend a place specific management strategy to reduce ES trade-offs of specific land use practices, which are currently apparent with agrarian change in Indonesia and relevant for other tropical developing countries. [ABSTRACT FROM AUTHOR]

The first comprehensive survey of gibbons (Hylobates spp.) across Indonesian Borneo was carried out over 3 years to (1) determine whether densities of gibbon species are correlated with vegetation characteristics, and if so, whether the same characteristics are correlated with density across all forest types; and (2) determine population densities in the survey areas and identify threats to the areas. To achieve this, a total of 8 forest blocks were surveyed, involving 53 independent survey locations and repeat surveys in 3 forest blocks. Our data show that gibbons are ubiquitous where there is forest; however, the quality of forest affects population density, forest block size affects longevity of populations, and populations are susceptible to the ëcompression effectí, i.e. populations occupy smaller fragments at unsustainably high densities. We show the effects of forest disturbance (logging, fire, fragmentation) on gibbon distribution and density and highlight issues for long-term conservation. We discuss the use of minimum cross-sectional area, habitat variables and presence of top foods to determine population density and to identify a threshold below which gibbons cannot persist. We discuss the conservation issues facing all Bornean gibbons, including natural hybrids (H. muelleri ◊ H. albibarbis). The answers to these research questions will help mitigate threats to gibbons and their habitat, as well as identify key habitat for gibbon populations within and outside the protected area network.

The physical analysis of a uniformly accelerating point charge provides a rich problem to explore in advanced courses in electrodynamics and relativity since it brings together fundamental concepts in relation to electromagnetic radiation, Einstein's equivalence principle and the inertial mass of field energy in ways that reveal subtleties in each of these concepts. By first exploring the heuristic value of Maxwell's and Faraday's idea that the electromagnetic field is "like" a stressed material medium, it is shown in this paper that the problem also provides an interesting application of the electromagnetic stress-energy-momentum tensor and that an analysis using this tensor provides clear physical insight into this highly subtle and contentious problem and the so-called "4/3 problem" of classical electromagnetic theory. In particular, it is shown that the stress force on a uniformly accelerating, uniformly charged spherical shell due to its own field is simply the (relativistic) inertial mass of the charge's electrostatic field times the acceleration. Since the inertial mass of the electromagnetic field forms part of the observed rest mass of a charged particle, it is argued that the results are therefore consistent with the Lorentz-Abraham-Dirac equation of motion for an accelerating point charge, which implies that for uniform acceleration, the work done by the force acting on the charge only goes into increasing the kinetic energy of the charge, none goes into the creation of radiation. (Contains 4 figures.)