Ecological Site Description Ecological Site Characteristics Site Identification
|
|  Yüklə 2.33 Mb.
|
Understory species canopy cover under a range of overstory canopy covers in Native Wet Forest. Overstory includes upper tree, secondary tree, and tree fern canopies combined.
S  tate 1, Plant Community 1, Native Wet Forest.
State 2 – Grassland This state is comprised of three grassland plant communities. Most of the pastures in this ecological site are on former sugar plantations where guineagrass was an agricultural weed. Guineagrass now has taken over these lands as the dominant pasture grass. Kikuyugrass is the dominant grass, sometimes with pangolagrass in some higher elevation areas in Kahuku and Keauhou where these species had been planted. Most of these areas are now being reforested. Some parts of Kapapala Ranch appear to be in a transitional area between guineagrass and kikuyugrass dominance. Information on these kikuyugrass/pangolagrass pastures can be found in Ecological Site Description F161AY500HI, Transition Zone Ohia-Koa-Mamane Forest. Plant Community 2 (Good Condition Pasture) consists of guineagrass with an admixture of glycine (perennial soybean). Continuous grazing that does not allow the favored forage species time to recover from defoliation results in Plant Community 3 (Poor Condition Pasture), which is dominated by lower value forage species but contains enough remnant guineagrass to allow for a transition back to Plant Community 1 with prescribed grazing. Longer-term continuous grazing leads to Plant Community 4 (Weedy Pasture), which consists of low value grass species and increasing cover of alien shrubs and tree saplings. Improvement of this Plant Community requires weed control and prescribed grazing. Pathways from this state To State 1 – Native Forest, via “C&D&M”: C = weed control; D = lack of fire; D = native plant restoration; M = ungulate exclusion. It may be possible to recreate a plant community resembling Native Forest from Pasture. Weed control must be applied to pasture species and the many opportunistic plant species that invade the site. Weed control would be a perpetual process to capture and maintain the site at least until a closed canopy of native trees developed. Animal foraging (domestic or feral) would have to be eliminated by excluding all ungulates from the restoration site, but domestic ungulates would be useful to initially reduce grass cover and to manage vegetation outside the restoration site perimeter. Extensive planting of native species would follow. Increased shade from trees growing on the site causes a shift from C4 (warm-season) grass dominance (typically guineagrass or kikuyugrass) to C3 (cool-season) shade-tolerant grasses (typically meadow ricegrass). This meadow ricegrass layer can be very dense and detrimental to establishment of native plants. Attempts have been made to suppress meadow ricegrass by planting native shrubs and tree ferns that produce dense shade near the ground and litter that covers the grass.
C = weed control; G = exotic timber planting. Pasture may be converted to Tree Plantation by site preparation and planting of timber species (usually eucalyptus) and weed control.
K = abandonment. Abandonment of pastures leads to rapid invasion of alien tree species that take over from the initial growth of grasses and weedy shrubs. The most common tree species are silk oak, christmasberry, albizia, and common guava.
The dominant grass species in this pasture type is guineagrass that has volunteered in old sugarcane plantations. In higher elevation areas in Kahuku and Keauhou, kikuyugrass and sometimes pangolagrass have been planted. Pathways from this plant community To Plant Community 3, Poor Condition Pasture, via “E”: E = continuous grazing. Good Condition Pasture degrades to Poor Condition Pasture by continuous grazing that weakens preferred guineagrass or kikuyugrass and legumes in relation to poor forage species such as Hilograss, narrowleaf carpetgrass, and sedges.
This list of plants and their relative proportions are based on near-normal years. Fluctuations in species composition and relative production may change from year to year depending upon precipitation or other climatic factors.
S  tate 2, Plant Community 2, Good Condition Pasture.
Plant Community 3 – Poor Condition Pasture Poor Condition Pasture is dominated by grasses of low forage value such as Hilograss, narrowleaf carpetgrass, and sedges. Desirable forage legumes have been grazed out. Pathways from this plant community To Plant Community 2, Good Condition Pasture, via “F”: F = prescribed grazing. Poor Condition Pasture can be reconverted to Good Condition Pasture by prescribed grazing. A prescribed grazing plan provides for intensive but temporary grazing of pastures that ensures that cattle consume some low-value forage species along with preferred forages and allows preferred forages time to recover from defoliation. The grazing plan may require splitting the herd, creating additional water sources, and creating multiple pastures by cross-fencing. Invading broomsedge and beardgrass may be controlled by mowing their seed stalks before seed set and by liming to increase soil pH.
E = continuous grazing. Poor Condition Pasture degrades to Weedy Pasture by long-term continuous grazing. Guineagrass cover is greatly reduced and largely replaced by low-value forage grasses. Weedy forbs such as spiny amaranth, alien blackberries, and alien shrubs such as sourbush have increased. Broomsedge and beardgrass often are the most abundant grass species.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||