| | |
 |
|
| 
| ||
 |
|
|
|
 |
|
Wildlife, Animals, and Plants |
|
|||
|
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
GENERAL BOTANICAL CHARACTERISTICS:Honey mesquite is a deciduous, thorny shrub or small tree exhibiting a high degree of variation in growth form. The three most common forms are: 1) a single-stemmed tree reaching 20 to 40 feet (6-12 m) in height, with crooked, drooping branches, 2) an erect, multiple-stemmed bush or small tree, often 10 to 15 feet (3-4.6 m) tall, and 3) a decumbent or running bush found on deep sandy soils [64,125,130]. The largest trees are often found along water courses or floodplains where the deep root system has access to year-round water [115]. All mesquites have a strong tendency for apical dominance and a well-developed crown [129]. Undisturbed trees therefore develop into single-stemmed trees. If the aboveground growth is damaged or removed, such as by freezing weather, drought, fire, trampling, browsing, cutting, or herbicide treatment, dormant buds located on the underground stem initiate new growth, resulting in the many-stemmed growth form [61]. On the Rolling Plains of north-central Texas, 27 year-old plants within a fenced exclosure ranged from 0.7 to 4.9 feet (0.2-1.5 m) tall [155]. Thus small plants that are decades old may be mistaken for seedlings. Thorns may be 1 to over 2 inches (2.5-5 cm) long and generally occur singly on young branches [75]. The flowers are in a raceme [178]. The flattened, straight, or curved legume-type pods are 4 to 8 inches (10-20 cm) long and occur in drooping clusters [178]. The seeds are oval, 0.2 inch (5 mm) wide, 0.28 inch (7 mm) long, and 0.08 inch (2 mm) thick [125]. Honey mesquite's root system is well adapted to dry climates (during and shortly after seedling establishment, the rate of root growth exceeds that of shoot growth [163]). Honey mesquite is a facultative phreatophyte which extracts moisture from a large volume of soil through a well-developed root system [8,81,171]. Honey mesquite's taproot commonly reaches depths of 40 feet (12 m) when subsurface water is available [63], though a taproot 190 feet (58 m) deep has been observed [163]. In areas where the soil is shallow, where water does not penetrate deeply, or where a distinct calcium carbonate layer is present, the taproot seldom extends more than 3 to 6 feet (1-2 m), and an extensive system of lateral roots often extends up to 60 feet (18 m) away from the plant base [9,43,64,81,163]. Lateral roots of a 19.7 foot (6 m) tall honey mesquite tree excavated on the Rolling Plains of north-central Texas were concentrated in the upper 1 foot (0.3 m) of the soil profile [81]. Similarly, Sosebee and Dahl [162] reported that most active lateral roots are in the upper 2.5 feet (0.75 m) of soil. Sprouting from lateral roots is common [81]. These adaptations allow honey mesquite to retain most leaves in all but the most severe droughts. As a legume, honey mesquite is capable of housing N2-fixing bacteria in nodes along its roots; it is also commonly heavily colonized by arbuscular mycorrhizal fungi [14]. Mesquites obtain about half of their nitrogen from symbiotic bacteria housed in root nodules [108]. Deloach [47] commented that nodes are rarely seen in honey mesquite but that the nodulation process is likely under multifactorial control and may not always be observable. Rundel [148] found that in the Sonora Desert of California, honey mesquite may fix up to 66 lbs/ acre/ year. An nitrate accretion rate of 90 lbs/ acre/ year was observed for 10 years in California below a western honey mesquite stand [67]. Honey mesquite, though potentially detrimental to competitive grasses, also facilitates plant growth by increasing soil organic matter content and nitrogen status [7,16]. Maximum ages that plants attain is unclear. Near Amarillo, Texas, the maximum age of plants within a stand of multi-stemmed honey mesquites ranged from 40 to 110 years [64]. On the Rio Grande Plains of Texas, Archer [12,13] found that 89% to 93% of honey mesquite plants were less than 100 years old, and the maximum age of plants sampled was 172 to 217 years. RAUNKIAER [138] LIFE FORM:Phanerophyte REGENERATION PROCESSES:Breeding system: Honey mesquite flowers have both pistils and stamens [150]. Pollination: As is typical of insect-pollinated plants, honey mesquite flowers develop simultaneously with the leaves, are high in nectar, and are scented. Honey mesquite is pollinated primarily by bees. At least 160 species of bees are associated with mesquites in the American Southwest. Although mesquite inflorescences contain hundreds of flowers, only a few fruits develop per inflorescence. Most flowers are pollinated by numerous insect visitors, but self abortion prevents most ovules from maturing. This ensures that adequate resources are available for the fruits that do develop [160]. Seed production: Honey mesquite plants generally produce seed by 3 years of age [75]. Several seeds are encased within an indehiscent fruit. The reproductive potential of honey mesquite is often greatly reduced by seed-feeding insects, but honey mesquite produces pods in such abundance that numerous viable seeds are still produced [103]. Insects using flowers (leaf-footed bugs and thrips) reduced pod production from a mean of 131 pods per tree on insecticide-sprayed trees to 97 pods per tree on unsprayed trees in western Texas. Bruchid beetles (weevils) are dependent on mesquite pods. In a southern California study, western honey mesquite had an average of 12 seeds per pod, of which an average of 5 were destroyed by bruchid beetles [133]. Seed dispersal: Pods are eaten and then dispersed by domestic and wild animals. When honey mesquite pods were fed to livestock, 97%, 79%, and 16% of the seeds passed through the digestive tracts of horses, yearling steers, and ewes, respectively, with the greatest number of seeds passing through between 42 and 60 hours after consumption [64]. In southern Texas, Brown and Archer [33] found honey mesquite seedlings in 75% of cattle dung piles sampled in September, but no seedlings on sites fenced to exclude cattle. On sites without cattle, no seeds were found away from parent trees. Because it takes days for seeds to pass through the digestive tracts of domestic animals, seeds are dispersed great distances. Mesquite seedlings commonly germinate from uneaten seeds in rodent caches. Floods are also a common means of seed dispersal [69]. Seed banking: Most seeds of a closely related species, velvet mesquite, germinated within 3 years after pod segments were buried 1 inch (2.5 cm) below the soil surface of an Arizona site. About 35%, 9%, and 1% of germination occurred 1, 2, and 3 years after planting. Honey mesquite seeds in dry storage can remain viable for decades. Sixty percent viability was reported for 44-year-old velvet mesquite seeds taken from herbarium specimens [171]. Germination: Honey mesquite seeds contain a protective endocarp. Scarification of this hard seed coat must occur before the seed can germinate. Scarification occurs naturally when seeds pass through the digestive system of animals. Seeds remaining in pods not consumed by animals remain dormant until the seed coat is broken by weathering or fire [75]. Under laboratory conditions, scarified honey mesquite seeds placed on moistened filter paper germinated in about 7 hours at 93 degrees Fahrenheit (33 °C) [154]. Seedling establishment/growth: Honey mesquite seeds must be covered with a small amount of soil or dung for seedlings to establish. Seeds that germinate on the soil surface usually die. When honey mesquite seeds were planted at various soil depths, emergence rates were greatest for seeds planted between 0.2 and 0.6 inch (0.5-1.5 cm) from the soil surface. No seedlings emerged when seeds were planted more than 2 inches (5 cm) deep [154]. Field studies in southern Texas found that under natural conditions honey mesquite seedlings emerged from dung both fall and spring following peaks in rainfall. When honey mesquite pods were fed to livestock 82%, 69%, and 25% of the seeds that passed through the digestive tracts of horses, yearling steers, and ewes, respectively, germinated [64]. Kramp and others [104] tested the effect of coyote, cow, and deer scat on 1- year seedling survival. Ten percent survived in coyote and cow manure, 31% survived in deer scat, but there was a much higher average number of initial seedlings in cattle manure (7 per manure unit) than in coyote and deer scat (3 per unit). Kramp and others [105] found that 27% of seedlings survived 1 year in clipped plots compared to 9.4% in unclipped plots (p=0.14). In central Texas, establishment of honey mesquite seedlings from sown seed was high under several different clipping regimes on both grazed and protected areas. However, on grasslands protected from grazing for several years, seedling establishment was 7 to 8 times greater when the grasses were clipped monthly to 10 inches (25 cm) than when not clipped [34]. Dense grass cover can reduce honey mesquite seedling establishment because seedlings emerge and establish with a 50% reduction in solar radiation, but when solar radiation is reduced by 75%, survival of seedlings is reduced [152]. Asexual regeneration: Honey mesquite plants can sprout from numerous perennial dormant buds located along rhizomes or the upper part of the root [62,64]. Dormant buds can occur up to 12 inches (30 cm) below the soil surface on older trees but are most commonly concentrated along the basal portion of the underground stem in a zone 2 to 6 inches (5-15 cm) below the soil surface [62]. When aboveground growth is damaged or killed, new sprouts arise from the bud zone. If aboveground growth is destroyed or damaged during a dormant period, sprouts arise the following spring and often flower during their first growing season. If aboveground growth is damaged during the wet part of the growing season when root carbohydrate levels are high, plants resprout rapidly but do not flower until the following growing season. If destroyed during the dry portion of the growing season when root carbohydrate levels are low, sprouting is delayed or slow, sometimes for 3 to 5 years [163]. SITE CHARACTERISTICS:Honey mesquite grows on a wide variety of sites and soil types in the Chihuahuan Desert and southern Great Plains. Honey mesquite was less common and more restricted to drainages prior to European-American settlement and livestock introduction. It has invaded grasslands as a result of overgrazing and reduced fire frequency [50]. On upland sites it often invades grasslands where it forms shrubby thickets. On some sites it occurs as scattered plants forming mesquite savannas, but on others its persistence has led to many grasslands being converted to "brushy ranges" or thorny scrublands [12,13,151]. Johnston [98] describes the "plains" of southern Texas as being covered by more or less dense growths of shrubs and low trees. Density of mature plants can range from 50 to over 1,500 plants per acre (124-3,716/ ha.) [62]. Up to 3,000 seedlings per acre (7,500/ ha.) have been observed in northern Texas [156]. In the Mojave and Sonoran deserts, rainfall is generally insufficient to provide adequate surface soil moisture for western honey mesquite to survive. Under these extremely arid conditions, western honey mesquite is a phreatophyte, typically occupying alkali sinks, outwash plains, dry lakes, oases, arroyos, or riverbanks, where plants have access to permanent underground water [96,158]. Plants are much less common outside washes [102]. Soils: Mesquites are adapted to most soil types, but in Texas, honey mesquite tends to grow best on medium to fine-textured soils. In areas of western Texas and southern New Mexico, honey mesquite grows on hummocky sand dunes [44]. Honey mesquite can grow rapidly to keep photosynthetic and reproductive structures above rising sand level [110]. On the Jornada Experimental Range near Las Cruces, New Mexico, honey mesquite is found on all soil types including loamy sand, sandy loam, calcareous silt loam, noncalcareous silt loam, gravelly sand loam, deep sandy loam, and calcareous clay [37]. Elevation: Honey mesquite generally grows below 4,500 feet (1,387 m) in elevation [64]. Western honey mesquite's elevational range in California is from 197 feet (60 m) below sea level to 3,575 feet (1,090 m) above sea level [88]; in Utah western honey mesquite grows between 2,197 feet (670 m) and 3,838 feet (1,170 m) [181]. In Arizona, western honey mesquite grows primarily below 5,000 feet (1500 m) [102]. In New Mexico, the typical variety of honey mesquite grows primarily between 3,000 and 5,000 feet (900-1500 m) [116]. Climate: In arid areas where annual rainfall is less than 6 inches (150 mm), honey mesquite is typically found along drainageways. It appears to be best adapted to uplands where annual rainfall reaches 15 to 20 inches (380-510 mm) and may be found on sites where annual rainfall exceeds 30 inches (760 mm) [151]. Honey mesquite is restricted northward and is limited to where the average annual minimum temperature is above -5 degrees Fahrenheit (-20 °C) and the frost-free growing season is 200 days or more [64]. SUCCESSIONAL STATUS:The successional pattern of grasslands that have become dominated by honey mesquite on the Rio Grande Plains of southern Texas has been from grassland to savanna to woodland. After colonizing grassland sites, a lone honey mesquite plant establishes a circular cluster of other woody plants within 10 to 15 years [33,34]. Honey mesquite apparently aids the establishment of other shrubs by attracting birds which disperse seeds of other woody species [24,33]. On study sites at the Texas Agricultural Experiment Station near Alice, Texas, a lone honey mesquite plant was found in 80% of all upland clusters of other shrubs. Woody plant clusters generally ranged from 3.3 to 132 feet (1-40 m) in diameter and contained 1 to 15 woody species. As new clusters are formed and old clusters expand and coalesce, a woodland is eventually formed. In about 25% of the clusters, the original lone honey mesquite had died. Death usually occurred before age 30 [33,34]. Invasion and establishment of honey mesquite in grasslands on the High Plains of western Texas facilitated the establishment of redberry juniper in much the same manner as described above [122]. Drought also appears to be a factor in the spread of honey mesquite. Honey mesquite seedlings often establish on areas where black grama cover has been reduced and gaps were created from the death of many plants following drought [37,61]. Western honey mesquite's deep root system increases its ability to compete with black grama on sandy soils during droughts [37]. The geographic range of honey mesquite has probably changed very little in the past 300 to 500 years, but the abundance of mesquite within this range has increased [50,98]. Some researchers state that range fires were very important in controlling honey mesquite before the introduction of cattle, while others believe that honey mesquite was rare on grasslands because of limited seed dispersal. Johnston [98] states that where mesquite has dominated former grasslands, it was probably originally present but stunted by repeated fire. Fire effects research supports this theory, demonstrating that honey mesquite is very fire tolerant when only 3 years old [190]. Plants may be top-killed by fire, but most resprout. Thus prior to grazing by livestock, repeated grassland fires probably only killed mesquite seedlings and a few other individuals but kept most plants low in stature and prevented many from producing seed. Dispersal of mesquite seeds was likely greater during the Pleistocene when browsing megafauna, such as camelids, stegomastodons, notoungulates, and edentates were present [129]. With the introduction of livestock by European settlers, mesquite invaded grasslands as cattle transported seed from plants which were primarily found in draws and drainageways. Brown and Archer [33] state that seed dispersal was probably the most important factor in honey mesquite's increase. Reduced fire frequencies due to overgrazing would have allowed honey mesquite plants that were previously suppressed and kept low in stature to reach maturity and thus produce more seed for livestock to disperse away from the parent plants. Fire exclusion has facilitated spread of honey mesquite. See the "Fire Ecology" section of this summary for further information. In the Mesilla basin of southern New Mexico and northern Mexico there are extensive dune fields, some of which predate European-American settlement, and some that have been transformed from semidesert grasslands during this century. It is theorized that conversion to dunelands is a self-sustaining process which leads to further desertification [147]. With heavy grazing, drought, and competition with honey mesquite for soil moisture, much of the grass cover on these sandy sites was depleted. The loss of grass cover led to wind erosion and the formation of dunes around honey mesquite plants. The multi-stemmed growth form of honey mesquite, which characteristically occurs on sandy soils, entraps drifting sands [72,82]. SEASONAL DEVELOPMENT:Spring bud break in honey mesquite can vary by as much as 6 weeks from year to year. Bud break is dependent upon both photo- and thermal periods and rarely occurs until after the last spring frost has passed or the photoperiod exceeds 11.5 hours [43,163]. Honey mesquite apparently has a cold requirement that must be met before bud burst occurs. Goen and Dahl [70] found that the higher the number of consecutive days with minimum temperatures below 30 degrees Fahrenheit (-1 °C) during January 15 to February 14, the earlier spring bud break occurs. They give equations for predicting honey mesquite bud break based on minimum winter temperatures. Other researchers state that honey mesquite bud burst begins in the spring when the soil warms to 64 degrees Fahrenheit (18 °C) [124]. Plants from northern populations generally exhibit later bud burst than plants from southern populations [120]. Following bud burst, twig elongation and leaf growth are rapid and generally completed in about 6 weeks [43]. New foliage is generally very dense following a wet spring and fall, but less foliage is produced if the preceding spring and fall were dry [163]. Inflorescences emerge in the spring with the leaves. By the time the leaves are fully expanded, miniature fruit pods have begun to develop [43]. It takes 2 to 3 months for the fruits to mature, and by late summer they fall from the plant. More than 1 fruit crop per year is possible but uncommon. Sometimes a wet period late in the flowering season causes a flush of new growth, producing new leaves and flowers and, consequently, a 2nd fruit crop. Flowering may occur up to 4 times in 1 growing season. Flower production varies with amount of available soil moisture. Heavy flowering and fruiting often occur when soil moisture is low; high soil moisture at the time of flowering appears to suppress fruit production [129]. Leaf drop generally occurs in November or December and is often initiated by a killing frost or leaf removal by insects [43]. Plants from northern populations show early dormancy and are more resistant to freezing damage than plants from southern populations [134]. Seasonal development of honey mesquite plants in western Texas was documented as follows [182]:
Related categories for SPECIES: Prosopis glandulosa | Honey Mesquite |
 |
 | |
| |
| |
| Content on this web site is provided for informational purposes only. We accept no responsibility for any loss, injury or inconvenience sustained by any person resulting from information published on this site. We encourage you to verify any critical information with the relevant authorities. | |
| |
|
About Us | Contact Us | Terms of Use | Privacy | Links Directory |
| 1Up Info All Rights reserved. Site best viewed in 800 x 600 resolution. |
