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The ingrowth core method for measuring root accumulation has several advantages over sequential soil cores or mini-rhizotrons. However, current ingrowth core designs are not well suited for use with rhizomatous perennial forage species or when defoliation occurs during the measurement period. Our objective was to develop a modified ingrowth core device and to evaluate its use for measuring root-rhizome accumulation of a rhizomatous perennial forage in a hay management context. The modified ingrowth cores were constructed of 4-mm polyester mesh surrounding a 7.5-cm diameter cylinder constructed of cage wire. Field testing of the core design involved placing three ingrowth cores in each of four replicates of six treatments arranged in a randomized complete block design. Treatments consisted of six rhizoma peanut (Arachis glabrata Benth.) entries, and they were evaluated during 2017 and 2018. The ingrowth core design facilitated ease of placement, maintenance of core structural integrity throughout 100-d deployment periods, rapid location of cores using a metal detector at the end of deployment periods, and precision to detect differences among treatments. We conclude that this modified ingrowth core design is well suited for measuring root-rhizome accumulation rate of perennial forage species. [ABSTRACT FROM AUTHOR]

Insects defoliating Bornean endemic dipterocarp seedlings at the Sepilok nursery were investigated. A total of 12 insect species were documented as new records. Two defoliators were adult beetles while 10 were larvae of moths and butterflies. The most frequently encountered insect species was Clethrogyna turbata Butler (Lepidoptera: Lymantriidae), which occurred on four dipterocarp species. Due to its high abundance, the larva caused severe defoliation to Shorea symingtonii, S. waltonii and S. kudatensis seedlings. Defoliation caused by other insects was minor. Some notes on the new records are provided in this paper. The importance and management of insects associated with the dipterocarp seedlings are also discussed. [ABSTRACT FROM AUTHOR]

Water stress is the most important factor limiting early survival and growth of seedlings in arid and semi-arid zones. Many woody species develop adaptive mechanisms in response to water stress. This study assesses survival rate, growth and dry matter distribution in response to water stress in four dryland species (Senegalia dudgeonii , Senegalia gourmaensis , Vachellia nilotica and Vachellia tortilis). A total of 240 seedlings (60 per species) were grown using a completely randomized block design with three replicates in each of three water treatments (control = 100 percent of field capacity; moderate water stress = 50 percent of field capacity; severe water stress = 25 percent of field capacity) with a 7 day watering frequency. Data were collected on seedling survival, height, collar diameter, leaf production and dry matter distribution. Survival rate of the four species was not affected by water stress. However, the morphological responses to water stress were significantly different between species. Water stress resulted in significant reductions in height and collar diameter, higher below-ground biomass and significant increase in shedding of leaves. Under water stress, S. dudgeonii , S. gourmaensis and V. tortilis invested more in root growth. The allocation pattern from above-ground to below-ground parts was found to be the main adaption to drought. In contrast, V. nilotica gave preference to above-ground development, which could be an indication that the seedlings are adapted to grow under severe water stress. The results confirm the interspecific genetic differences in growth and dry matter distribution among species. These variations in water stress response may be used as criteria for species selection for degraded land reforestation. [ABSTRACT FROM AUTHOR]

Many non-native, invasive woody species in mesic forests of North America are both shade tolerant and more productive than their native counterparts, but their ability to tolerate disturbances remains unclear. In particular, complete defoliation associated with herbivory and extreme weather events may have larger impacts on invaders if natives maintain greater resource reserves to support regrowth. On the other hand, invaders may be more resilient to partial defoliation by means of upregulation of photosynthesis or may be better able to take advantage of canopy gaps to support refoliation. Across a light gradient, we measured radial growth, new leaf production, non-structural carbohydrates (NSCs), chlorophyll content and survival in response to varying levels of defoliation in saplings of two native and two invasive species that commonly co-occur in deciduous forests of Eastern North America. Individuals were subjected to one of the four leaf removal treatments: no-defoliation controls, 50% defoliation over three growing seasons, 100% defoliation over one growing season and 100% defoliation over two growing seasons. Contrary to our hypothesis, native and invasive species generally did not differ in defoliation responses, although invasive species experienced more pronounced decreases in leaf chlorophyll following full defoliation and native species' survival was more dependent on light availability. Radial growth progressively decreased with increasing defoliation intensity, and refoliation mass was largely a function of sapling size. Survival rates for half-defoliated saplings did not differ from controls (90% of saplings survived), but survival rates in fully defoliated individuals over one and two growing seasons were reduced to 45 and 15%, respectively. Surviving defoliated saplings generally maintained control NSC concentrations. Under high light, chlorophyll concentrations were higher in half-defoliated saplings compared with controls, which may suggest photosynthetic upregulation. Our results indicate that native and invasive species respond similarly to defoliation, despite the generally faster growth strategy of invaders. [ABSTRACT FROM AUTHOR]

Aims Mechanisms of plant drought resistance include both tolerance and avoidance. Xylem vulnerability to embolism and turgor loss point are considered traits that confer tolerance, while leaf abscission and deciduousness characterizes the avoidance strategy. While these mechanisms are thought to trade-off expressing a continuum among species, little is known on how variation in the timing and duration of leaf shedding in response to drought affect the relationship between xylem and leaf tolerance. In the present study, we explored the extent to which drought tolerance differs between two oak (Quercus) species that exhibit different leaf shedding behaviours. Particularly, we predicted that Q. deserticola Trel., which loses leaves at the end of the dry season (late-deciduous) and is thus exposed to a greater risk of cavitation, would be more drought tolerant and more conservative in its water use than Q. laeta Liebm., which loses its leaves for only a short period of time in the middle of the dry season (brevideciduous). Methods The study was conducted in central Mexico in a single population of each of the two oak species, separated from each other by a distance of 1.58 km, and by an altitudinal difference of 191 m. Quercus deserticola (late deciduous) is more frequent down slope, while Q. laeta (brevideciduous) tends to occur at higher elevations along the gradient. We assessed seasonal differences (rainy versus dry season) in native stem hydraulic conductivity, and tested for variation in xylem vulnerability to cavitation, leaf water use and leaf turgor loss point between the two species. Important Findings The two oak species did not differ in traits conferring drought tolerance, including xylem vulnerability to embolism, leaf turgor loss point, or stomatal conductance. However, both species had different performance during the dry season; the brevideciduous species had lower negative impact in the xylem function than the late-deciduous species. Overall, seasonal changes in plant physiological performance between the two oak species were determined by a reduction in the canopy leaf area. [ABSTRACT FROM AUTHOR]

Summary: Catastrophic failure of the water transport pathway in trees is a principal mechanism of mortality during extreme drought. To be able to predict the probability of mortality at an individual and landscape scale we need knowledge of the time for plants to reach critical levels of hydraulic failure.We grew plants of eight species of Eucalyptus originating from contrasting climates before allowing a subset to dehydrate. We tested whether a trait‐based model of time to plant desiccation tcrit, from stomatal closure gs90 to a critical level of hydraulic dysfunction Ψcrit is consistent with observed dry‐down times.Plant desiccation time varied among species, ranging from 96.2 to 332 h at a vapour‐pressure deficit of 1 kPa, and was highly predictable using the tcrit model in conjunction with a leaf shedding function. Plant desiccation time was longest in species with high cavitation resistance, strong vulnerability segmentation, wide stomatal‐hydraulic safety, and a high ratio of total plant water content to leaf area.Knowledge of tcrit in combination with water‐use traits that influence stomatal closure could significantly increase our ability to predict the timing of drought‐induced mortality at tree and forest scales. [ABSTRACT FROM AUTHOR]

Mangrove is a highly resilient ecosystem unique in harboring a diverse group of plants and animals with extreme salt tolerance capacity. In Indian scenario, 4461 km² area is under mangrove cover, amounting to 5% of the world's mangrove area. Coringa mangrove is situated in East Godavari district of Andhra Pradesh state in the east coast of India. Vast floral diversity of this mangrove supports large entomofaunal diversity. Damage of leaf photosynthetic area due to insect feeding is a major problem in this mangrove ecosystem. The present research focused on quantification of the damage of mangrove leaves due to insect feeding and measuring the extent of insect folivory between three species of Avicennia, a major floral component of Coringa mangrove. This study involved the application of a software-based digital image analysis to quantify the magnitude of insect defoliation. Three species of Avicennia, namely, Avicennia officinalis, Avicennia marina, and Avicennia alba were selected as target species due to their abundance in good numbers. The digital image of the collected leaf samples was created using desktop scanner, and the same was subjected to analysis. The result showed an overall range of 0.15-20.42% leaf area damage due to insect folivory in three species of Avicennia in two maturational stages of leaves, namely, young and matured leaves. The analysis showed significant variation in the magnitude of insect folivory in 2009, when compared between three species of Avicennia in the case of both young and matured leaves. However, in 2010, though in the case of young leaf samples, there is no significant variation in leaf area damage between three species; the matured leaves showed clear cut variation in damage extent. [ABSTRACT FROM AUTHOR]

Premise: Two fundamental hypotheses on herbivore resistance and leaf habit are the resource availability hypothesis (RAH) and the carbon–nutrient balance hypothesis (CNBH). The RAH predicts higher constitutive resistance by evergreens, and the CNBH predicts higher induced resistance by deciduous species. Although support for these hypotheses is mixed, they have rarely been examined in congeneric species. Methods: We compared leaf constitutive and induced resistance (as leaf polyphenol and tannin concentrations, and as damage level in non‐choice experiments) and leaf traits associated with herbivory of coexisting Nothofagus species using (1) a defoliation experiment and (2) natural defoliation caused by an outbreak of a common defoliator of Nothofagus species. Results: In the defoliation experiment, polyphenol and tannin concentrations were similar between deciduous and evergreen species; regardless of leaf habit, polyphenols increased in response to defoliation. In the natural defoliation survey, N. pumilio (deciduous) had significantly higher herbivory, lower carbon/nitrogen ratio and leaf mass per area, and higher nitrogen and phosphorus concentrations than N. betuloides (evergreen); N. antarctica (deciduous) had intermediate values. Polyphenol concentrations and herbivore resistance indicated by the non‐choice experiment were lower in N. pumilio than in N. antarctica and N. betuloides, which had similar values. Conclusions: Higher herbivory in N. pumilio was associated with a higher nutritional value and a lower level of leaf carbon‐based defenses compared to both the evergreen and the other deciduous species, indicating that herbivore resistance in Nothofagus species cannot be attributed to only leaf habit as predicted by the RAH or CNBH. [ABSTRACT FROM AUTHOR]

The spruce budworm ( Choristoneura fumiferana) is the most destructive insect defoliator of forests in North America. Climatic influences on this species' life history are considered a major factor in restricting the extent and intensity of outbreaks. We examine the life history traits of the spruce budworm and related Choristoneura populations with respect to forecasting the conifer-feeding responses of these insects in changing environments. Analysis of the evolutionary relationships between Choristoneura entities, including their hybridization, genetic distances, and their degree of sympatry leads us to distinguish 15 possible Choristoneura‘biotypes’. Population trend has been associated with recruitment to the feeding stage, and two indicators of recruitment, egg weights and phenological development, are both ‘biotype’ and climate dependent. Among Abietoid feeding ‘biotypes’ and among spruce budworm populations, those from locations with extreme winters tend to have heavier eggs than those from the more benign environments. In spruce budworm, this genetically based adaptation allows populations to increase their potential recruitment substantially where winters are mild. All biotypes feed on the newly developed shoots of their host trees in spring, and are thus vulnerable to the uncertain timing of budbreak. Genetic control of spring emergence is weak so larvae from a single family typically exit from hibernacula over a prolonged period. This guarantees some synchronization with budburst. However, hybrid populations have high heritabilities. This allows rapid adaptation to new conditions (e.g. mixed host-species stands). Geographic variation in phenological development after establishing feeding sites is largely genetically controlled. The importance of variation in these traits is examined with respect to competing population dynamics theories to evaluate their utility in forecasting future trends in defoliation. We finish with a plea for jointly using alternative approaches in forecasting spatiotemporal patterns of defoliation. [ABSTRACT FROM AUTHOR]

• Key message: Gonipterus platensisis an important insect pest of eucalypt plantations. Despite biological control by the egg parasitoidAnaphes nitens, economic losses remain high in several areas outside its native range where susceptible eucalypt species are grown in commercial plantations. The susceptibility toG. platensisof 17Eucalyptusspecies was evaluated and possible alternatives for reforestation in high pest incidence areas were identified. • Context: Gonipterus platensis is an important pest of Eucalyptus worldwide. Despite biological control, it causes significant losses to Eucalyptus plantations in several areas, requiring alternative management options. • Aims: We analysed host preference of G. platensis towards 17 Eucalyptus species to identify less susceptible plant materials that could be used in areas of high pest incidence. • Methods: Feeding damage was assessed in field trials in three consecutive years. No-choice and choice tests were conducted with Eucalyptus species of contrasting susceptibility. • Results: Within subgenus Symphyomyrtus, all species from section Maidenaria were used by G. platensis for feeding. Within this section, E. globulus was always the preferred species, while E. nitens was the least preferred. Differences in susceptibility were less pronounced at high attack intensity by G. platensis. Eucalyptus saligna (section Latoangulatae) was the least preferred species among Symphyomyrtus. All species from subgenus Eucalyptus had low susceptibility to G. platensis, particularly E. regnans, which was never attacked under field conditions. The results were confirmed by choice and no-choice laboratory and semi-field tests. • Conclusion: Significant differences in susceptibility to G. platensis were found between the 17 Eucalyptus species tested, which could be explored for reforestation with less susceptible plant materials. [ABSTRACT FROM AUTHOR]