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Non-native grass invasion has increased fuel loads and fire frequency in areas throughout the tropics, resulting in a non-native grass-wildfire cycle with negative impacts on native biodiversity and ecological processes. Megathyrsus maximus (guinea grass) invades dry and mesic ecosystems throughout the tropics, increasing fuel loads and wildfire intensity. Eradication of M. maximus is difficult, making effective wildfire management critical to the protection of adjacent developed areas and remnant native ecosystems. The use of domestic livestock grazing in non-native grass ecosystems may be effective at decreasing fine fuel loads and potential wildfire behaviour. Our objectives were to: (1) quantify live and dead fine fuel loads and moistures in a M. maximus-dominated ecosystem before and after cattle grazing, and (2) use these data to model potential wildfire behaviour in grazed and ungrazed M. maximus grasslands with the BehavePlus fire modelling system. Fine fuel loads and moistures, climate variables, and predicted wildfire behaviour were quantified at the same site (n=1) over two 5-month periods (March-July 2009, ungrazed; March-July 2010, grazed) in the Wai'anae Kai Forest Reserve on the Island of O'ahu, Hawai'i. Strong to conclusive evidence existed that cattle grazing in this system decreased dead and total fuel loads, but did not alter live fuel loads, or live and dead fuel moistures. Modelled wildfire behaviour under both low and average fuel moisture scenarios revealed that grazing decreased the potential rate of spread by 44-52% and flame length by 36-41%. These results demonstrate that cattle grazing may be an effective approach for reducing fuel loads and potential wildfire behaviour in non-native-dominated grasslands on tropical islands. [ABSTRACT FROM AUTHOR]

Questions How does potential fire behaviour differ in grass-invaded non-native forests vs open grasslands? How has land cover changed from 1950-2011 along two grassland/forest ecotones in Hawaii with repeated fires? Location Non-native forest with invasive grass understory and invasive grassland ( Megathyrsus maximus) ecosystems on Oahu, Hawaii, USA. Methods We quantified fuel load and moisture in non-native forest and grassland ( Megathyrsus maximus) plots ( n = 6) at Makua Military Reservation and Schofield Barracks, and used these field data to model potential fire behaviour using the BehavePlus fire modelling program. Actual rate and extent of land-cover change were quantified for both areas from 1950-2011 with historical aerial imagery. Results Live and dead fuel moisture content and fine fuel loads did not differ between forests and grasslands. However, mean surface fuel height was 31% lower in forests (72 cm) than grasslands (105 cm; P < 0.02), which drove large differences in predicted fire behaviour. Rates of fire spread were 3-5 times higher in grasslands (5.0-36.3 m·min−1) than forests (0-10.5 m·min−1; P < 0.001), and flame lengths were 2-3 times higher in grasslands (2.8-10.0 m) than forests (0-4.3 m; P < 0.01). Between 1950 and 2011, invasive grassland cover increased at both Makua (320 ha) and Schofield (745 ha) at rates of 2.62 and 1.83 ha ·yr−1, respectively, with more rapid rates of conversion before active fire management practices were implemented in the early 1990s. Conclusions These results support accepted paradigms for the tropics, and demonstrate that type conversion associated with non-native grass invasion and subsequent fire has occurred on landscape scales in Hawaii. Once forests are converted to grassland there is a significant increase in fire intensity, which likely provides the positive feedback to continued grassland dominance in the absence of active fire management. [ABSTRACT FROM AUTHOR]

Frequent wildfires in tropical landscapes dominated by non-native invasive grasses threaten surrounding ecosystems and developed areas. To better manage fire, accurate estimates of the spatial and temporal variability in fuels are urgently needed. We quantified the spatial variability in live and dead fine fuel loads and moistures at four guinea grass (Megathyrsus maximus) dominated sites. To assess temporal variability, we sampled these four sites each summer for 3 years (2008-2010) and also sampled fuel loads, moistures and weather variables biweekly at three sites for 1 year. Live and dead fine fuel loads ranged spatially from 0.85 to 8.66 and 1.50 to 25.74 Mg ha[sup -1] respectively, and did not vary by site or year. Biweekly live and dead fuel moistures varied by 250 and 54% respectively, and were closely correlated (P < 0.05) with soil moisture, relative humidity, air temperature and precipitation. Overall, fine fuels and moistures exhibited tremendous variability, highlighting the importance of real-time, site-specific data for fire prevention and management. However, tight correlations with commonly quantified weather variables demonstrates the capacity to accurately predict fuel variables across large landscapes to better inform management and research on fire potential in guinea grass ecosystems in Hawaii and throughout the tropics. The spatial and temporal variability in fuel loads and moistures were quantified in non-native invasive guinea grass ecosystems in Hawaii. Fuel loads and fuel moisture, the primary drivers of fire occurrence and behaviour, varied tremendously spatially and temporally, and were strongly influenced by 7-day antecedent weather. This information can inform management and research on fire potential and behaviour in non-native tropical grassland ecosystems. [ABSTRACT FROM AUTHOR]

Questions How does a highly degraded Hawaiian tropical dry lowland ecosystem dominated by the non-native invasive Megathyrsus maximus (guinea grass) respond to different restoration treatments (three native species outplanting treatments; four native broadcast seed treatments)? What effect do restoration treatments have on invasive and native species groundcover, biomass and physiological activity, and volumetric soil water content? Location Waianae Kai Forest Reserve, Island of Oahu, Hawaii, USA. Methods The invasive grass M. maximus was suppressed by initial mowing and pre- and post-planting herbicide applications. Native species were added in three outplant and four broadcast seed treatments in a complete randomized block design. Native species and M. maximus growth and ecophysiology, and volumetric soil water content were quantified for 8 mo following treatment establishment. Results Native species outplant survival ranged from 38% to 67%. Cover of M. maximus was significantly reduced in all outplant treatments compared with control and treated control (mowing and herbicide without native species additions), but did not differ across outplant treatments. Of the native species, Dodonaea viscosa biomass was higher than Cordia subcordata, while other native species did not differ. Maximum photosynthetic rates ( Amax) did not differ across species in July. However, in August (drier period), M. maximus exhibited lower Amax than all native species except T. populnea, indicating adaptive dormancy during drought. Broadcast seeding with native species was not an effective restoration treatment, as field germination ranged from 0.5% to 2.3%. Conclusions Ecological restoration of highly invaded Hawaiian tropical dry lowland ecosystems can be mediated through aggressive invasive species suppression and native species outplanting. Recommendations for restoration include initial removal of invasive grasses, adaptive suppression of grasses post-outplanting, and utilization of diverse native species assemblages that are ecophysiologically adapted to local conditions and competitive with M. maximus. [ABSTRACT FROM AUTHOR]

Abstract: A 15-week treatability study was conducted in a greenhouse to evaluate the potential effects of molasses on the bioremediation and phytoremediation potential of Guinea Grass (Panicum maximum) for treating energetic contaminated soil from the open burn/open detonation area of the Makua Military Reservation, Oahu, HI (USA). The energetics in the soil were royal demolition explosive (RDX) and high-melting explosive (HMX). Among the 6 treatments employed in this study, enhanced removal of RDX was observed from treatments that received molasses and went to completion. The RDX degradation rates in treatments with molasses diluted 1:20 and 1:40 were comparable suggesting that the lower dose worked as well as the higher dose. Treatments without molasses degraded RDX slowly and residuals remained after 15 weeks. The bacterial densities in molasses-treated units were much greater than those without molasses. Phytoremediation alone seems to have little effect on RDX disappearance. For HMX, neither bioremediation nor phytoremediation was found to be useful in reducing the concentration within the experimental period. The concentrations of nitrogen and phosphorous in the soil did not change significantly during the experiment, however, a slight increase in soil pH was observed in all treatments. The study showed that irrigating with diluted molasses is effective at enhancing RDX degradation mainly in the root zone and just below it. The long term sustainability of active training ranges can be enhanced by bioremediation using molasses treatments to prevent RDX deposited by on-going operations from migrating through the soil to groundwater and off-site. [Copyright &y& Elsevier]

Surveys were conducted to identify the weeds bordering Hawaiian pineapple plantings that could serve as hosts for the pink pineapple mealybug, Dysmicoccus brevipes (Cockerell). Collected mealybugs were held to determine parasitization by the encyrtid Anagyrus ananatis Gahan. Greater than 15 species of weeds were found around pineapple plantings in both disturbed (e.g., mowed, herbicide treated, manual weed removal) and undisturbed areas. Weed diversity was low in the undisturbed areas with guinea grass, Panicum maximum, being the dominant species and free of pink pineapple mealybug. Weed species composition was more diverse in the disturbed areas adjacent to plantings, with routinely mowed areas being more diverse. Although pink pineapple mealybug is a polyphagous mealybug, it was only found in moderate densities on rhodesgrass, Chloris gayana, and wire grass, Eleusine indica, both of which were found in mowed and unmowed weedy areas with the former species being more common. All phenological stages of rhodesgrass were infested with pink pineapple mealybugs, but only mature wire grass plants were infested. None of the pink pineapple mealybugs collected from the weeds produced parasitoids, which suggests that the most common weeds found during these studies did not serve as reservoirs for A. ananatis. Because some common weed species harbored Dysmicoccus mealybugs, weed management could play a significant role in reducing pink pineapple mealybug movement into pineapple plantings. [ABSTRACT FROM AUTHOR]

Cows and calves are fed by 100% grazing on pastures in Hawaii islands, which are characterized by plentiful sunshine and rainfall with average monthly temperature of 25 to 30°C and average monthly precipitation of 46 mm to 121 mm. To evaluate the suitability of Angus Plus cattle for Hawaii subtropical climates, we collected the data of the growth performances of 149 Angus Plus calves in the past three years (2003-2005). Angus Plus calves were produced by maintaining the purebred lines of Angus or Brangus between 65% and 96% black Angus and a minimum of 4% Brahman. The Angus Plus cattle herd have been selected for preweaning gain, daily gain on pasture grass after weaning, fertility and mothering ability. All the animals were raised on 100% improved pastures of Pangola (Digitaria decumbens, Stent), Rhodes (Chloris gayana) and Guinea (Panicum maximum Jacq.) throughout the year. Data for birth weight (BWT), pre-weaning average daily gain adjusted to 205 days (PWADG) were obtained. Average birth weight of calves was 37.1 ± 1.24, 34.7 ± 0.51 and 34.2 ± 0.51 kg in 2003, 2004 and 2005, respectively, and hip height at birth was 73.4 ± 0.46 cm in 2003, 72.4 ± 0.23 cm in 2004 and 71.9 ± 0.20 cm in 2005. The mean of 205 d-adjusted weight was 252.8 ± 6.63 kg in 2003, 265.4 ± 8.69 kg in 2004, and 247.4 ± 3.41 kg in 2005. Average preweaning daily gain based on the adjusted 205 day is 1.05 ± 0.03, 1.10 ± 0.13, and 1.04 ± 0.15 kg/d for year 2003, 2004 and 2005, respectively. Interestingly, the birth weight is significantly correlated with hip height at birth (r=0.730, P < 0.001), preweaning daily gain (r =0.527, P < 0.001) and adjusted 205 d weight (r =0.510, P < 0.001) based on three-year pooled data. However, the hip height at birth is not significantly correlated to the hip height at weaning (P > 0.05). These results demonstrated great performances of Angus Plus calves raised on 100% pasture in Hawaii subtropical climates. The combination of Angus with Brangus to produce Angus Plus cattle have the potential to contribute to the growing demand of forage-based production of high-quality natural and organic beef for the local and international markets. [ABSTRACT FROM AUTHOR]