Molasses grass on the island of Maui, Hawaii.
Molasses grass is native to Africa [2,34,50,54,55], where it occurs in 2 disjunct populations in tropical areas . The western population occurs in an arc from central Angola to Cameroon, while the eastern population occurs on the lower slopes and adjacent areas of the Ruwenzori Range and Mount Kenya . Molasses grass established in Brazil around 1812, where it thrives on disturbed, abandoned coffee lands of the Paraíba Valley .
Molasses grass was introduced to Hawaii in the early 1900s for cattle forage . It was first collected on Lana`i Island in 1914 . In the 1920s it was introduced to Moloka`i Island . By the 1940s it was present in Hawai`i Volcanoes National Park but was mainly restricted to roadways [45,46], where it was probably controlled by feral goat grazing . Molasses grass spread in Hawai`i Volcanoes National Park began in the 1970s, facilitated by the removal of feral goats .HABITAT TYPES AND PLANT COMMUNITIES:
Hawaii: Molasses grass is common in primarily dry to mesic, disturbed, usually open areas in the Hawaiian Islands. It occurs in coastal areas, in lowland dry shrublands and forests, and in lowland mesic grasslands and forests .
Most coastal areas once dominated by native pili grass (Heteropogon contortus) are now dominated by nonnative shrubs and trees on gently sloping to level lowlands; however, pili grass is still dominant on very steep slopes, cliff ledges, and eroded areas. In many of these areas, however, pili grass appears to have been replaced by nonnative grasses including molasses grass, Natal redtop (Melinis repens), and fountain grass (Pennisetum setaceum) .
Molasses grass occurs in 3 native lowland dry shrubland community types and 2 native lowland dry forest community types described by Wagner and others . On leeward Moloka`i, molasses grass occurs in a nonnative-dominated herb layer with Natal redtop in a rare community dominated by the native shrub `ohai (Sesbania tomentosa); and in open shrublands codominated by the native shrubs ko`oko`olau (Bidens menziesii subsp. menziesii) and `āweoweo (Chenopodium oahuense) where the sparse grass understory also includes pili grass, annual panicgrass (Panicum spp.), and Natal redtop. Nonnative grasses, including molasses grass, may be present but not dominant in native `a`ali`i (Dodonaea viscosa)-dominated shrublands. Molasses grass occurs in native koa (Acacia koa) forest communities and in a unique forest community dominated by olopua (Nestegis sandwicensis) and lama (Diospyros sandwicensis) that is heavily damaged by axis deer and invaded by several nonnative plants, in addition to molasses grass .
In lowland mesic communities, molasses grass occurs in 2 grassland types and 2 forest types described by Wagner and others , and it is included among several nonnative plant species that may be “capable of displacing” some native lowland mesic shrublands. Many occurrences of the kāwelu (Eragrostis variabilis) grassland community type are invaded by nonnative grasses including molasses grass. A molasses grass community type occurs on most of the main islands in the same geographic, climatic, and edaphic settings as mesic shrublands and kāwelu grasslands, on sites formerly dominated by native and other nonnative grasses and released from grazing pressure. Molasses grass also occurs in native `ōhi`a (Metrosideros polymorpha) forest types and in nonnative Brazilian pepper (Schinus terebinthifolius) forest types, which typically occur on abandoned agricultural sites and pasturelands .
Molasses grass stolons.
Aboveground description: Molasses grass is a strong-smelling , perennial grass [2,38,50] that may be as short as 20 inches (50cm) but is typically 30 to 60 inches (80-150 cm) tall . It produces long, slender stems that layer on top of one another, forming thick mats [9,31,32,33,34,38,46] that can be from 4 to 5 feet (1.2-1.5 m) deep [11,12]. Molasses grass has a sprawling growth form and can "climb" over shrubs much like a vine. It grows upward and outward, using other species for support. Molasses grass can carpet large areas of ground completely , which can reduce seedling establishment and growth of other plants [9,34,38,50]. Molasses grass leaves range from 1.4 to 9.8 inches (3.5-25 cm) long [2,50], and panicles are 3 to 8 inches (7-20 cm) long and 0.4 to 3.7 inches (1-9.5 cm) wide . Molasses grass spikelets are 1.5 to 2.4 mm long [2,50]. At Hawai`i Volcanoes National Park (on a site with 17% molasses grass cover), molasses grass averaged 375.2 flowering shoots/m² . The fruit of molasses grass is a caryopsis that is often undeveloped  and is from 0.9 to 1.2 mm long and 0.3-0.4 mm wide .
Belowground description: Molasses grass plants usually root at the lower stem nodes . At a site dominated by molasses grass in Hawai`i Volcanoes National Park, molasses grass root biomass ranged from 176.9 to 198.2 g/m² .
RAUNKIAER  LIFE FORM:
Molasses grass may reproduce from seeds [5,11,21,34,46], stolons [5,27,28,33], basal meristems , or rhizomes [13,21,46].
At the time of this writing (2008), there is no information on molasses grass breeding system, pollination, seedling establishment and growth, or seed production.
Seed dispersal: Molasses grass seeds are dispersed by wind .
Seed banking: Molasses grass seeds can occur in the soil seed bank [11,46]; however, seed longevity is unknown. Tunison and others  found that molasses grass seed is "ubiquitous" in the soil of unburned `ōhi`a woodlands in Hawaii. Near Kipuka Nene, Hawai`i Volcanoes National Park, D'Antonio and others  extracted molasses grass seeds from soil samples 3 inches (8 cm) deep and 1.8 inches (4.5 cm) wide in October 1991 and February and June 1992. Following extractions, molasses grass seeds were planted in containers and seedling emergence was measured for 3 months following each of the 3 extraction dates. Seed bank samples were taken from an unburned woodland, a woodland burned in 1970, a woodland burned in 1987, and a site burned both in 1970 and 1987. In general, seedling emergence was significantly greater from seeds extracted from burned sites (P<0.05) .
Mean number of molasses grass seedlings emerging from soil samples in unburned and burned woodlands near Kipuka Nene, Hawai`i Volcanoes National Park 
|October 1991||February 1992||June 1992|
|Burned in 1987||2.60b||15.25a,b||8.10b|
|Burned in 1970||10.00b||25.40b||8.10b|
|Burned in 1970 and 1987||3.25b||17.90b||5.80a,b|
|*Different lowercase letters in the same column indicate a significant difference (P<0.05)|
Germination: Molasses grass seed germination is better with increasing sunlight, is largely unaffected by heat , and is promoted by elevated CO2 . In a controlled outdoor experiment, molasses grass seed germination and growth were significantly better with 49% or more sunlight (P<0.05). At 1%, 3%, and 33% of full sunlight, average (SE) molasses grass seed germination rates were 10.4% (1.8), 12.7% (2.5), and 13.9% (1.8), respectively. At 49% and 100% full sunlight, germination rates were 27.1% (2.6) and 25.5% (3.1), respectively .
The germination rate of heat-treated molasses grass seeds was not significantly different than that of unheated seeds (P<0.80) . The average germination rate of molasses grass seeds heated for 4 minutes at temperatures ranging from 140 °F to 250 °F (60 °C-120 °C) was 18.8% .
Vegetative regeneration: Molasses grass regenerates vegetatively by stolons [5,27,28,33], basal meristems , and rhizomes [13,21,46].SITE CHARACTERISTICS:
Climate: In Hawaii, where the climate is warm-tropical, molasses grass occurs where the mean annual air temperature is 76 °F (23 °C) and annual rainfall ranges from 60 to 80 inches (1,500-2,000 mm). There is a pronounced dry period during the summer .
Elevation: In Hawaii, molasses grass occurs from sea level to 4,900 feet (0-1,500 m) [38,50,52].
Soils: In Hawai`i Volcanoes National
Park, molasses grass grows on ash-derived soils over pahoehoe lava .
Parsons  says that molasses grass thrives best on thin soils.
Molasses grass is shade-intolerant  and thrives in open, disturbed areas [4,19,34] such as burned sites [13,29,45]. Molasses grass is not tolerant of heavy grazing [32,49]. Establishment and spread of molasses grass in native plant communities in Hawaii may alter succession in invaded communities .
At Hawai`i Volcanoes National Park, nonnative bush beardgrass (Schizachyrium condensatum) is abundant in unburned, seasonally dry woodlands . Following fire, molasses grass partially replaces bush beardgrass. In the absence of fire, molasses grass establishment in bush beardgrass communities is depressed due to low light levels. In a controlled experiment, molasses grass established in unburned woodlands following the removal of bush beardgrass. Additionally, when molasses grass seedlings established in bush beardgrass communities or when bush beardgrass and molasses grass seedlings emerge on the same site simultaneously, molasses grass came to dominate the site .
Lowland dry shrublands in Hawaii are relatively intolerant of fire and are often replaced by nonnative-dominated communities after fire. See Fire Regimes for more information on the role of molasses grass in these changes. In Venezuela, Baruch and others [3,4] suggest that the spread of molasses grass was likely aided by the burning of savannas in the Coastal Mountains to improve pastures. Molasses grass may alter the successional dynamics of shrublands in Hawaii [1,49]. Molasses grass "appears capable of displacing" many of the native lowland mesic shrublands in Hawaii . On the upper leeward slopes of Moloka`i Island, monospecific molasses grass stands and shrub (pūkiawe (Styphelia tameiameiae) and `a`ali`i) stands with molasses grass had significantly greater soil nitrogen pools than uninvaded shrublands (P<0.05). The increase of nitrogen may promote further establishment of molasses grass and other nonnatives in native Hawaiian shrublands that are normally nutrient-poor . Conversion of Hawaiian woodlands to grasslands via fires appears to increase nitrogen available to plants. In a molasses grass-dominated grassland converted via fire from a `ōhi`a woodland in Hawai`i Volcanoes National Park, net nitrogen mineralization was 3.4 times greater than in an unburned `ōhi`a woodland .
Molasses grass can tolerate low grazing pressure, giving it an advantage over
less tolerant species . However, molasses grass is intolerant of heavy grazing,
and changes in dominance have been observed with changes in grazing pressure.
Beginning in the 1970s in Hawai`i Volcanoes National Park, there has been a shift in the
central coastal lowland grasslands from dominance of annual and short-statured
perennial grasses to dominance of mid-sized, fire-tolerant, perennial grasses
including molasses grass . Following the removal of feral goats from the park
between 1971 and 1975 [31,33], Japanese lovegrass (Eragrostis amibilis),
golden false beardgrass (Chrysopogon aciculatus), Bermudagrass (Cynodon dactylon),
and native pili grass were replaced by nonnative thatching grass (Hyparrhenia spp.)
and molasses grass. In 1970 there were approximately 14,000 goats in the park
and by 1980 there were fewer than 200 . At Pu'u Kaone in Hawai`i
Volcanoes National Park, goat removal led to molasses grass dominance. In a 5-year period,
molasses grass became a dominant species with 25% cover in a formerly closed
golden false beardgrass-Bermudagrass community . Molasses grass grasslands
subjected to heavy grazing by axis deer on Lāna'i are "becoming barren, eroded
In Hawaii, molasses grass flowering occurs in a synchronous burst in late November. Seed set and leaf die back occur simultaneously during January and February. New leaves begin to appear in March and April . Each year, most new molasses grass leaves are produced along the upper end of existing stems or on new short lateral branches of older stems . In Florida, molasses grass flowers in the fall [53,54,55].
Fuels: Molasses grass is highly flammable [21,22,30], quick burning , and promotes fire  by increasing vegetation horizontal continuity in invaded communities . Molasses grass leaves are coated with a resinous material and may have a high heat content . Molasses grass stands maintain a high dead:live biomass ratio throughout the year (80-90%) and can carry fire at relative humidities of 85% to 95% and fuel moistures of 20% to 25% . In Hawai`i Volcanoes National Park, molasses grass fuels have been measured as high as 25,370 kg/ha . Another study in Hawai`i Volcanoes National Park compared fuel loads in different vegetation types. Total fuel biomass was greater in an unburned woodland (1,967.4 g/m²) than in woodlands converted to nonnative grasslands (1,427.5 g/m²) on sites burned 24 and 7 years previously. However, fine fuel loads (live + dead) were higher in converted grasslands (996.2 g/m²) than in unburned woodlands (613.0 g/m²) . Where molasses grass is dominant or codominant in Hawaii Volcanoes National Park, fire impacts on native plants are "always greater" than where it is absent .
The fine fuel characteristics of a pure molasses grass stand were measured in 1975 at Kuaokala Forest Reserve near Ka`ena, Hawaii . The median annual rainfall in the reserve for a 28-year period was 32 inches (810 mm). In 1975, total precipitation was 30 inches (750 mm).
Molasses grass fine fuel characteristics at Kuaokala Forest Reserve, Hawaii 
|Depth of fuel (inches)|
|Surface area-to-volume (1/foot)|
|Mean fuel weight for all subplots (lb/ft²)||0.458||3.481||1.721|
In the cerrado of Brazil, where molasses grass is common at the edge of gallery forests, total living and dead leaf area index is 38% greater on sites with molasses grass than on sites without it. Greater fuel loads in sites with molasses grass increase fire intensity . Computer models of the Reserva Ecológica do Roncador, Brazil, suggest that when dead fuel moisture in molasses grass-dominated stands is less than 15%, fires can move rapidly even at low wind speeds. At 16% dead fuel moisture and wind speeds of 6 miles/hour (10 km/hour), flame heights in molasses grass stands were predicted to be 22 feet (6.6 m). Fire temperatures in molasses grass stands in late August were predicted to peak at 1,000 to 1,843 °F (800-1,006 °C). Flame heights and fire intensities in molasses grass stands would likely kill many trees in the Brazilian reserve, a phenomenon that does not naturally occur in vegetation fires there. Even during periods of "low" burning conditions in the reserve, computer models suggest fires in molasses grass stands could spread rapidly. The effect of molasses grass on fire intensity in the reserve could be "devastating". Fuel characteristics on sites dominated by molasses grass and sites dominated by native vegetation without molasses grass are presented below .
Fuel characteristics modeled in the Reserva Ecológica do Roncador, Brazil, in nonnative and native sites 
|Molasses grass-dominated sites||Native vegetation sites (range)|
|Live herbaceous fuel (t/ha)||2.1||0.1-3.0|
|Live herbaceous fuel moisture (%)||107||107-200|
|Fuel depth (m)||0.7||0.3-0.5|
|Surface area:volume of live herbaceous fuel (/cm)||39||39-42|
|Heat content of dead fuel (KJ/kg)||23,300||17,200-19,500|
|Heat content of live fuel (KJ/kg)||18,600||16,300-17,000|
Fire regimes: Research from Hawaii shows [8,14,37,40] and computer models in Brazil  suggest that molasses grass can cause an increase in both fire frequency and size.
Hawaii: The size and frequency of fires have increased in some plant communities in Hawaii following the establishment and spread of molasses grass and other nonnative grasses [1,8,14,37,40]. Fires fueled by broomsedge bluestem (Andropogon virginicus), molasses grass, buffelgrass (Pennisetum ciliare), fountain grass, and bush beardgrass (Schizachyrium condensatum) largely account for the dramatic increase in fire size and frequency in seasonal submontane and eastern coastal lowland zones in the last 25 years [13,26,37,40,45,46]. For example, prior to nonnative grass invasions, `ōhi`a woodlands consisted of open stands of discontinuous fine fuels. Now, nonnative grasses constitute over 30% of the understory biomass and 60% to 80% of the understory cover in Hawai`i Volcanoes National Park's `ōhi`a woodlands, forming a continuous source of fine fuel .
Flammable, fire-dependent, or fire-maintained plant species do not occur in most native, undisturbed plant communities in Hawaii, and therefore fires were assumed to be of little ecological significance . While presettlement fire regimes are difficult to reconstruct in Hawaii , historical fires were probably very small and localized . The first nonnative grass-fueled fire was reported in Hawaii in 1968 . Fire frequency and fire size have increased markedly in Hawai`i Volcanoes National Park since 1968. From 1920 to 1967, 27 fires averaging 10 acres (4 ha) were recorded. From 1968 to approximately 1991, 58 fires burned an average of 507 acres (205 ha) each . Some fires may be related to increased volcanic activity from 1983 to 1992. However, an increase in fine fuels following the removal of feral goats in the 1970s is a more likely cause [16,40,44]. Since the spread of fire-prone grasses in Hawai`i Volcanoes National Park during the 1960s and 1970s, fire frequency has increased 3-fold and fire size over 60-fold .
Most native shrubs in Hawaii are negatively impacted by fire, and their cover and dominance are reduced in the postfire environment while nonnative grass cover tends to increase [38,40]. Nonnative grasses such as molasses grass can lead to a grass/fire cycle in Hawaii [21,26,45,46]. A grass/fire cycle threatens to turn native Hawaiian woodlands and tropical forests into nonnative grass savannas or monotypic grasslands [40,46,48]
Brazil: In the 3,200 acre (1,300 ha) Reserva Ecológica do Roncador, Brazil, molasses grass has increased the potential for fire . Molasses grass increases the intensity of fires at gallery forest edges in the cerrado, where native trees are fire sensitive .
Australia: Near the foothills of Cairns, Australia, molasses grass is a "rapid colonizer" on severely burned sites. Where it grows on steep slopes it can causes "hot, potentially damaging" fires .POSTFIRE REGENERATION STRATEGY :
Increase in postfire cover: In the following studies, all in Hawaii, molasses grass cover increased on all burned sites after fire. Twice-burned molasses grass sites had significantly greater cover than sites burned only once [11,21].
Molasses grass cover in a mesic `ōhi`a woodland near Kipuka Nene, Hawai`i Volcanoes National Park, was significantly greater on burned sites than unburned sites (P>0.05) [11,21]. Further, molasses grass cover was significantly greater on sites burned twice than on sites burned once (P>0.05). Sites studied were an unburned woodland, a woodland burned in 1970, a woodland burned in 1987, and a woodland burned in both 1970 and 1987. Molasses grass cover measurements in 1989 and 1991 were taken in December at peak biomass and during full fruiting, and measurements in 1998 were taken in November during a year of "severe" drought when plants were small and not flowering. The decline in molasses grass cover on the twice-burned site from 1991 to 1998 was attributed to season of measurement and drought conditions. The site, at an elevation of 2,800 feet (850 m), receives 55 to 87 inches (1,400-2,200 mm) of annual precipitation [11,21].
|December 1989||December 1991||November 1998|
|Burned in 1987||49.7b||71.2b||---**|
|Burned in 1970||62.1b||75.5b||---|
|Burned in 1970 and 1987||79.3c||93.4c||78.5b|
|*Different lowercase letters in the same column indicate a significant difference
The researchers found that bush beardgrass was the primary nonnative grass on unburned sites. Bush beardgrass provides fine fuels sufficient to carry fire in `ō`hia woodlands. During postfire establishment, molasses grass cover increases while bush beardgrass cover stays relatively constant. If a second fire occurs, molasses grass cover further increases, coinciding with a decrease in bush beardgrass cover, leading to a molasses grass-dominated grassland. The authors suggest that molasses grass is potentially more damaging to native species than bush beardgrass since it causes greater fire intensity and more rapid spread .
At mesic sites in Hawai`i Volcanoes National Park, molasses grass cover increased significantly on all burned sites when compared to unburned sites (P<0.05) . At 6 of 10 burn sites, molasses grass was either dominant or codominant with bush beardgrass. All burned sites, excluding Pailiulu Mauka, occur in the seasonal submontane zone, which is the leeward section of the park and occurs from 1,000 to 3,900 feet (400-1,200 m). Pailiulu Mauka is in the eastern coastal lowlands that occur from sea level to 1,000 feet (400 m). Of the 3 common nonnative grasses (bush beardgrass, broomsedge bluestem, and molasses grass), molasses grass had the greatest positive response to fire. After fire, molasses grass was dominant on the low intensity Lucky Eddy site. Molasses grass was codominant with bush beardgrass in the unburned control of Uila but dominated after fire. Molasses grass mean cover of averaged 22% greater on burned than unburned sites. The following table summarizes study results [13,45].
|Site||Cause of fire||
|Month of fire||Area burned (ha)||Fire intensity||Years since fire||Cover (%) on unburned site||Cover (%) on burned site|
|*Cover on burned and unburned sites are significantly different (P<0.05)|
One study in Hawai`i Volcanoes National Park describes the origin of postfire molasses grass plants. At Pepeiau, a site not described in the table above, the researchers counted the number of molasses grass plants establishing vegetatively and by seeds for 20 postfire months on a molasses grass-dominated site. After the low-severity December fire, molasses grass regenerated by sprouts from basal meristems and by seeds. Molasses grass regeneration by sprouting was approximately 4.5 times greater than regeneration from seeds .
A small summer wildfire (8 acres (3 ha)) in the mesic Kawailoa Forest Reserve, Oahu, increased the number of molasses grass plants on only 1 of 4 plots . The prefire vegetation was an open forest of koa (Acacia koa), forest sandalwood (Santalum freycinetianum), strawberry guava (Psidium cattleianum), and guava (P. guajava) with a dense understory of Old World forkedfern (Dicranopteris linearis), lantana (Lantana camara), broomsedge bluestem, and molasses grass. While molasses grass was part of the prefire community, the researchers do not say if it occurred on all 4 burn sites before fire. The fire was described as a "moderately intense" surface fire. Molasses grass was present on only 1 plot 1.5 months after fire. At postfire month 13.5, molasses grass was "abundant". At postfire months 25.5 and 80.0 (the last measurement date), molasses grass was "very abundant". On plot 2, molasses grass occurred in postfire month 25.5 but was absent by postfire month 80. On plot 3, molasses grass was not present until postfire month 80. Molasses grass was not present on plot 4 during any postfire measurement period .
Molasses grass cover increased after a prescribed fire in a mesic, mixed grass-shrub `ōhi`a woodland at Hilina Pali in Hawai`i Volcanoes National Park . Molasses grass cover was 0.5% or less 12 and 6 months before the fire. Six months after the 5 May 1976 fire, molasses grass cover had increased to 2.17%. On the unburned control, molasses grass cover decreased from 1.0% twelve months before the fire to 0.6% six months after the fire .
Decrease in postfire cover: In a study in an xeric section of Hawai`i Volcanoes National Park, molasses grass cover decreased after fire and native cover was either unaffected or increased following fire. The sites where molasses grass cover decreased after fire are considerably drier (20-30 inches (500-750 mm)) than sites in the seasonal submontane zone (60-80 inches (1,500-2,000 mm)) studied by D'Antonio and others  and Tunison and others  and described above, where molasses grass cover increased after fire.
Molasses grass cover generally decreased over a 2- to 5-year postfire period after naturally caused fires (lightning and lava flows) in the mid-1980s in arid coastal lowland sites of Hawai`i Volcanoes National Park . At 3 sites burned by high-and low-severity fire, molasses grass cover was slightly less on burned (0.2%-1.2%) than unburned (0.2%-5.0%) plots. At a fourth site, a molasses grass-Natal redtop transitional grassland, molasses grass occurred as a codominant species (52.7% cover) in the preburn community. Molasses grass cover decreased to 40.3% two years after a September 1987 lightning-caused, high-severity fire. At this site the native subshrub `uhaloa (Waltheria indica) increased substantially following fire, possibly accounting for the postfire decrease in cover of molasses grass .
Postfire seedling emergence: Molasses grass seedling emergence from the seed bank occurred following a low-severity prescribed fire but not following a high-severity prescribed fire at Hawai`i Volcanoes National Park . Five months after fire, 232 molasses grass seedlings/m² emerged on the low-severity burn site, but no seedlings emerged on the high-severity burn site, despite "adequate" rainfall .FIRE MANAGEMENT CONSIDERATIONS:
Potential for postfire establishment and spread: The high potential for postfire establishment and spread of molasses grass should be noted. If fire occurs in or near a community where molasses grass occurs, establishment and spread of molasses grass are probable. Tunison and others  suggest that fire suppression and prevention should be emphasized in the submontane seasonal zone of Hawai`i Volcanoes National Park to reduce negative effects on native vegetation and the continued spread of nonnative grasses. Further, sites severely degraded by fire should be revegetated with native, fire-tolerant plant species in an effort to reduce nonnative grasses .
Palatability/nutritional value: No information is available on this topic.
Cover value: At the time of this writing (2008), there was no information on the cover value of molasses grass. However, molasses grass grows in dense stands and can reach heights from 30 to 60 inches (80-150 cm) , so it likely provides cover for some animals.OTHER USES:
IMPACTS AND CONTROL:
Impacts: Molasses grass negatively impacts native plant species and fire regimes where it occurs in Hawaii and South America. It is considered one of the 3 most invasive grasses in the Hawaiian seasonal submontane zone  and one of the 10 most invasive species in Hawaii .
Impacts on native Hawaiian plants: In Hawaii, molasses grass forms dense mats that can interfere with establishment of many native species [19,38,49]. Molasses grass has a sprawling growth form and can "climb" over shrubs much like a vine. It grows upward and outward, using other species for support. Molasses grass can carpet large areas of ground completely , which can "snuff" out other plants [9,34,38]. Molasses grass has become abundant in Hawai`i Volcanoes National Park since the early 1970s [29,38]. It was first introduced on the lower leeward slopes of Moloka`i Island in the 1920s, and, as of 1996, occurred in large monospecific stands that extended beyond the initial pastures. It has also spread into upper elevation (2,600 to 3,300 feet (800-1,000 m)), moist shrublands, forming many large monospecific stands and mixed grass-shrub mosaics ranging in size from 0.2 to 200 acres (0.1-100 ha) . In coastal areas, molasses grass is replacing native pili grass on some sites .
Molasses grass is considered a major threat to 10 taxa on 4 Hawaiian Islands. In the Waianae Mountains of Oahu, 3 populations of Hawaii lady's nightcap (Bonamia menziesii), 2 populations of sprawling schiedea (Schiedea hookeri), and 1 population each of Kāmanomano (Cenchrus agrimonioides), Kauai spurge (Euphorbia haeleeleana), and ale (Plantago princeps var. princeps) are immediately threatened by molasses grass. On Moloka`i, at least 1 population each of erect island spleenwort (Diellia erecta), ale (P. princeps var. laxifolia), and woodland ma`oloa (Neraudia sericea), and all populations of Oahu cowpea (Vigna o-wahuensis) are negatively affected by molasses grass. Molasses grass is quickly spreading throughout the dry regions of West Maui, threatening 2 populations of erect island spleenwort. On Hawaii Island, a rare population of `ohai in Hawai`i Volcanoes National Park is located in an area invaded by molasses grass .
Postfire impacts on native Hawaiian plants: Molasses grass and other nonnative grasses have fueled large, frequent fires in Hawaii over the past 25 to 30 years [1,8,14,26,37,40]. Molasses grass-fueled fires can lead to the decline or extirpation of native species [11,13,21]. The negative impact of molasses grass-fueled fires on native species in Hawai`i Volcanoes National Park is likely due to one or more of the following: 1) high prefire biomass, 2) vigorous postfire regeneration, 3) postfire morphology that inhibits native species, 4) altered fire characteristics associated with leaf chemistry or molasses grass fuel characteristics .
Nonnative grasses have extensively invaded areas of Hawai`i Volcanoes National Park. Following fires, native shrub cover is reduced and the reduction can last for at least 20 years or more, even in the absence of additional fire [11,16]. On the southwest flank of Kilauea Volcano, Hughes and Vitousek  studied the effect that postfire establishment of bush beardgrass and molasses grass has on the native shrubs pukiawe, `a`ali`i, `ūlei (Osteomeles anthyllidifolia), and Hawaii false ohelo (Wikstroemia phillyreifolia). The researchers found that densities of native shrubs following fires were significantly lower in burned sites than unburned sites (P<0.05). Only `a`ali`i is able to establish via seed immediately after fire. The rapid establishment and persistence of nonnative grasses following fire negatively impacts the persistence of native shrubs .
At Hawai`i Volcanoes National Park, fires in 1970 and 1987 led to dominance by molasses grass and the introduced bush beardgrass. Prior to fires, the overstory was dominated by the native tree `ōhi`a and the understory by the shrubs pukiawe, `a`ali`i, and Hawaii hawthorn . In burned areas of Hawai1i Volcanoes National Park, molasses grass and bush beardgrass are the dominant species. With the exception of `a`ali`i, native shrubs are largely lacking. Molasses grass cover increased from 7.2% in unburned Hawaiian woodlands to 79.3% in twice-burned sites, with biomass increase from less than 10 g/m² to greater than 700 g/m² .
South America: In the Cerrado of Brazil, molasses grass is known to cause "large" reductions in the establishment of the gallery forest pioneer cecropia (Cecropia pachystachya) tree and other trees and shrubs . In the Reserva Ecológica do Roncador, Brazil, molasses grass may reduce plant biodiversity . Molasses grass is invading grasslands of the Venezuelan savannas and displacing native grasses [3,4]. Molasses grass is able to displace the native grass crinkle-awn (Trachypogon plumosus) in areas with "favorable" water and soil nutrient supplies, but crinkle-awn resists invasion by molasses grass in drier, infertile sites .
At the time of this writing (2008), there was no information on control of
molasses grass. In a 1998 publication, it is stated that molasses grass has
never been targeted for biological control .
OTHER MANAGEMENT CONSIDERATIONS:
Global climate change: Elevated CO2 levels cause molasses grass to grow at a greater rate than the native South American savanna grass crinkle-awn . In a controlled study, elevated CO2 caused molasses grass to produce significantly (P<0.05) more total biomass and leaf area than crinkle awn, and to be significantly (P=0.02) taller and grow twice as fast as the native grass .
|Fire regime information on the Florida vegetation community in which molasses grass is known to occur. This information is taken from the LANDFIRE Rapid Assessment Vegetation Models , which were developed by local experts using available literature and expert opinion. This table summarizes fire regime characteristics for each plant community listed. The PDF file linked from each plant community name describes the model and synthesizes the knowledge available on vegetation composition, structure, and dynamics in that community. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Surface or low||99%||3||1||5|
Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [18,24].
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