Showing papers on "Tree canopy published in 1984"

The natural history of lianas on Barro Colorado Island, Panama

Abstract: Liana (woody vine) abundance, height, diameter, and climbing mode were studied in the mature tropical moist forest on Barro Colorado Island, Panama (BCI). Because lianas are capable of extended horizontal as well as vertical growth, sample plots were 100—m2 cylinders extending from the ground up to the treetops. The plots were randomly located in areas representing different stages of regeneration following treefalls. In order to examine canopy lianas closely, trees in or adjacent to the sample plots were climbed freehand or with the aid of mechanical rope ascenders. Lianas are abundant on BCI and play important roles in forest dynamics. A hectare of old—growth forest had 1597 climbing lianas distributed among 43% of the canopy trees. Trees with a least one liana has higher than random probability of having more than one liana, and individual lianas connected an average of 1.56 canopy trees. In the understory, 22% of the upright plants <2 m tall were lianas, and, depending on the species, between 15 and 90% of these plants were vegetative offshoots (ramets) and not true seedlings (genets). Lianas were most abundant in recent treefall gaps and decreased in abundance with time since last disturbance. Trellis availability was found to be a major factor limiting liana access to the forest canopy. Experimental manipulation of supports and experimental planting of Dioclea reflexa seedlings revealed that trellises consisting of small diameter, closely spaced supports are most abundant on the edges of treefall gaps. Tree and liana stems on the edges of treefall gaps provided a major pathway to the canopy for climbing plants. Trees carrying lianas suffered higher mortality rates and upon falling caused more other trees to fall than did liana—free trees. Few lianas died when their host tree fell, and many grew back to the canopy using the abundant trellises that occur on the edges of treefall gaps. Tree sapling growth rates in treefall gaps and Luehea seemannii growth rates in the canopy were slower where lianas were abundant.

Influence of Microtopography and Canopy Species on Spatial Patterns of Forest Understory Plants

Abstract: In a maple-beech forest in eastern New York, equal numbers of mounds, pits, and adjacent undisturbed soil microsites were censused for plant species density and cover over the growing seasons of 1978 and 1979. Several soil properties were also measured for each microsite. Detrended correspondence analysis (DCA) and chi-square goodness-of-fit tests were used to test whether the species were uniformly distributed over the microrelief positions. Comparisons of species composition, diversity, and vegetative phenologies were made between microsites and between hemlock- and hard- wood-dominated forest areas. Differences in soil properties between microsites and between the two forest areas were assessed with one-tailed paired t tests and Wilcoxon rank-sum tests, respectively. Microrelief created a mosaic of soil properties and a vegetation pattern in the understory, both of which were affected by the presence of hemlock in the canopy. Ordinations (DCA) indicated two factors that affected species composition of the microsites: (1) presence of hemlock (Tsuga canadensis) as the nearest canopy tree, and (2) microtopography (whether the microsite was a mound, pit, or undisturbed-soil site). Species in non-hemlock areas had patchy distributions in the forest community: eight species grew mainly on mounds, six in pits, and five on undisturbed soil. The mounds and pits had characteristic assemblages of species. Species richness and total density and cover of plants in each microsite were constant over the growing season. In contrast, little spatial or temporal community pattern was apparent in forest areas influenced by hemlock. The effect of hemlock on species distributions was due in part to its effect on soil properties. For all microsites, forest areas with hemlock had greater soil organic matter content, available nitrogen, cation exchange capacity, and litter depth, lower soil calcium content, moisture content, temperature, pH, and A, horizon depth; and no frost heaving. Microrelief also affected soil properties significantly. In comparison with pits, mounds were drier and poorer in nutrient content, and had a lower cation exchange capacity, less organic matter, less litter cover, a thinner A, horizon, and less snow accumulation. In areas without hemlock, the mounds were also more acid, warmer in summer and colder in winter, and more subject to frost heaving than pits. Hemlock-influenced areas had no consistent microsite differences in pH or temperature. The different microenvironments, created by the interaction of microrelief and hemlock, resulted in patchy distributions of most understory species. This pattern was likely a result of species require- ments for and tolerances of environmental conditions, tempered by competitive interactions.

Epiphyte biomass and nutrient capital of a neotropical Elfin forest

Abstract: The epiphyte communities of a Costa Rican cloud forest make up a conspicuous portion of the canopy, especially on large canopy dominants. Non-destructive sampling methods were used to assess the composition, biomass, and nutrient concentration of live and dead epiphytes on representative host trees to determine the mineral capital contained in the epiphyte components of the standing vegetation. Epiphyte standing crop on a single large Clusia alata (Guttiferae) tree is 141.9 kg. The nutrient capital (in g) is: N = 3062; P = 97; K = 678; Ca = 460; Mg = 126; Na = 207. Using information on forest structure and epiphyte distribution, stand-level estimates of epiphyte mat nutrient capital were made. Although epiphyte biomass constitutes less than 2 percent of total elfin forest ecosystem dry weight, the nutrients they contain are equivalent to up to 45 percent of nutrients contained in ecosystem foliage of similar ecosystems. Assessment of epiphyte nutrient capital gives a more complete and accurate idea of the aboveground vegetation pools, and supports the idea that epiphytes may play a greater role in ecosystem nutrient dynamics than has been previously considered. ALTHOUGH THE IMPORTANCE OF MINERAL NUTRITION for plants and animals has been recognized for centuries, only recently has there been a systematic approach to mineral element cycling in entire ecosystems (Pomeroy 1970, Jordan et al. 1972, Golley et al. 1975). Estimates of the total amount of mineral elements and the rate of elemental cyding within a complete landscape unit during a period of time have resulted in the formulation of several basic mineral cycling concepts (Rodin and Bazilevich 1967, Jordan and Kline 1972, Bormann and Likens 1979). The general approach has been to divide the ecosystem into a series of compartments, or pools, and to measure the quantity and chemical composition of each pool and the pathways and rates of flux between each component in as great detail as possible. A small number of ecosystemlevel studies (e.g., Ovington and Madgwick 1959, Cole et al. 1968, Woodwell and Whittaker 1968, Duvigneaud and Denaeyer-DeSmet (1975), an even smaller number of which were tropical (e.g., Nye 1961, Odum and Pigeon 1970, Golley et al. 1975, Grubb 1977, Cole and Johnson 1978, Jordan 1982), have been important in the development of theories of community stability, nutrient use efficiency, and ecosystem resilience. Because of the greater diversity and complexity of tropical forests, and the greater logistical problems encountered there, the sizes of many of the compartments that make up tropical ecosystems remain poorly known. In most whole-ecosystem studies, epiphytes-plants deriving support but not nutrients directly from their host trees-have been discounted or ignored, as their biomass was considered insignificant in proportion to other forest components. However, vascular and non-vascular epiphytes make up a conspicuous portion of many rain forest canopies, reaching their greatest diversity and abundance in neotropical cloud and elfin forests, which are regularly enshrouded in mist and lack a prolonged dry season (Richards 1964, Sanford 1968, Madison 1977, Sugden and Robins 1979). Although the epiphytic flora of these forests has attracted a good deal of botanical attention, most of it has been focused on aspects of taxonomy (Dressler 1979, Benzing 1981a), phytosociology (Eggeling 1947, Sanford 1968, Johnson and Awan 1972, Russell and Miller 1977, Madison 1979, Sugden 1981, Yeaton and Gladstone 1982), and physiology (Hosokawa and Odani 1957, Medina 1972, Benzing and Ott 1981, Huber 1978). These canopy-dwelling plants must overcome greater extremes of insolation, temperature, humidity, and wind than their terrestrial counterparts. They lack organic connection to the bank of nutrients and water stored in forest soils. Resources are pulse-supplied from atmospheric sources, and canopy surfaces may be characterized by frequent and/or prolonged deprivations of moisture and nutrients (Benzing 198 1b). Many aspects of epiphyte morphology, physiology, and life history contribute to their efficiency at garnering and retaining airborne nutrients (Benzing 198 1b, 1982). By virtue of their powers of mineral accretion and their location along primary nutrient flux routes, epiphytes can be major participants in the impoundment and movements of mineral elements in a forest ecosystem (Nadkarni 1983). The effects of epiphytes on ecosystem-level interactions have been investigated in only a few studies, all in temperate forests (Denison et al. 1972, Pike 1972, 1978, Lang et al. 1976, 1980, Schlesinger and Marks 1977, Benzing and Seeman 1978). Assessing the mineral IReceived 3 November 1983, revised 3 February 1984, accepted 7 February 1984. BIOTROPICA 16(4): 249-256 1984 249 This content downloaded from 157.55.39.104 on Sun, 19 Jun 2016 06:38:59 UTC All use subject to http://about.jstor.org/terms capital contained in epiphytes is an important first step in determining their role in rain forest nutrient dynamics and in obtaining a more complete and accurate picture of all aboveground components. Minerals contained in their living and dead tissues constitute a nutrient pool, distinct from host tree minerals, which are immobilized for some span of time within the canopy. These can be transferred to other ecosystem pools via litterfall, crown wash, and in some cases, by host tree canopy root systems (Nadkarni 1981). In this paper, as part of a comparative study of within-canopy nutrient dynamics in temperate and tropical rain forests, I assess the composition, biomass, and nutrient content of epiphyte communities on large canopy trees in a neotropical elfin forest, compare the nutrient capital contained in epiphytes with other ecosystem components of similar forests, and discuss some of the processes by which epiphytes accrue and retain their nutrient capital. Some of the terms used in this paper have multiple or ambiguous meanings and are defined here: biomassthe dry weight of living matter present in a given plant community; standing crop-the dry weight of living and dead components of a given plant community; epiphyte mat-the composite unit of living arboreal plants and their associated detrital matter found within host tree

Patterns of tree replacement: canopy effects on understory pattern in hemlock - northern hardwood forests*

Abstract: The effect of canopy trees on understory seedling and sapling distribution is examined in near-climax hemlock-northern hardwood forests in order to predict tree replacement patterns and assess compositional stability.

Correlations of understory herb distribution patterns with microhabitats under different tree species in a mixed mesophytic forest.

Abstract: This study examines the role of canopy trees in the formation and maintenance of different herb microhabitats in a mixed mesophytic forest stand. Herb abundance and reproductive success were recorded in 54 circular plots under seven species of canopy trees and in 15 circular control plots>2 m from any tree. Soil moisture, soil nutrient levels, litter depth, and light intensity were measured in a subset of these plots. Ordination of plots by both herb relative abundance and by reproductive success of common species indicated that herb assemblages under most canopy tree species were similar to those away from trees. However, herb assemblages under Fagus grandifolia trees differed moderately from the others while plots under Quercus alba trees supported significantly different herb assemblages. Analyses of variance revealed that several herb species occurred at significantly closer mean distance to the base of Q. alba or Fagus trees or at higher densities under these tree species. Soils around Q. alba trees had significantly higher concentrations of calcium and sulfate ions, and higher pH than plots under other tree species and control plots. This correlated closely with Q. alba stemflow which had higher concentrations of calcium and sulfate ions and lower concentrations of hydrogen ions than stemflow from other trees at this site. The slightly lower soil pH near the base of Fagus trees may have been related to the high volumes of stemflow produced by this species. Stepwise regression showed significant correlations between abundances of five common herb species and soil nutrient patterns. Maintenance of spatial heterogeneity in forest floor resources by the presence of different species of canopy trees may therefore be important in the maintenance of diversity in these understory herb communities.

Basal branching and vegetative spread in two tropical rain forest lianas

Abstract: In a primary evergreen rain forest in Veracruz, Mexico, liana recruitment to the forest canopy from the forest floor is commonly by vegetative mechanisms. Two liana species were selected to study this pattern of clonal growth. Ipomoea phillomega maintains extensive stolon systems, colonizing gaps from adjacent undisturbed forest and penetrating undisturbed forest from gaps. Marsdenia laxiflora is restricted to primary forest and its stolon systems generate new liana canopies from deep shade of the forest floor. Both species produce a variety of shoot types, each one with characteristic morphology, growth rate and survival rates of apex and leaves. Vegetative spread is by basal branching (the production of epicormic shoots). It is suggested that vegetative spread by stolons is a natural consequence of hydraulic constraints on liana canopy growth and that this pattern may result in long lives for established liana genetic individuals. CLIMBING PLANTS ARE CONSPICUOUS AND CHARACTERISTIC members of tropical forest communities. Estimates of their contribution to the vascular plant species diversity of the community range from 12% in Puerto Rico (Smith 1970) to 31 percent in Ghana (Hall and Swaine 1981). The suppressive effect of dimbers on other vegetation is often dramatic and presents a serious problem in tropical silviculture (Jackson 1956, Nicholson 1965, Fox 1968, Meijer 1970). Yet despite the abundance and ecological importance of climbers in the tropics, contemporary ecologists have directed little attention to their biology. To date, the most comprehensive reviews of the structure and strategies of dimbers remain those of Darwin (1867) and Schenck (1892, 1893). A few modern investigators have considered such aspects as the behavior of tendrils and twining shoots of cultivated climbers (Baillaud 1962a, b) or the architecture of garden-grown vines (Cremers 1973, 1974), but we have as yet little research relating the growth forms of climbers to their behavior in plant communities. Here I report observations on two lianas in an evergreen tropical forest in Veracruz, Mexico. I have been concerned with analyzing shoot architecture, monitoring growth rates and the appearance and disappearance of plant parts, and mapping the spread of these plants in the forest. Detailed accounts of the dynamics of growth and attachment and of the demography of shoot parts are available in other papers (Penialosa 1982, 1983, in

Canopy Dynamics of Eucalyptus Maculata Hook. I. Distribution and Dynamics of Leaf Populations

Abstract: The canopy dynamics of a regenerated 16-year-old stand of pole and sapling E. maculata were studied for 2½ years by repetitive non-destructive measurements in tree crowns accessed from a 20 m high scaffold tower. Average canopy leaf area density over a sample plot of 36 m2 was 0.23 m2 m-3 at a leaf area index of 4.3. Some 75% of leaf area was held in the canopies of overstorey eucalypts above 10 m in height. Average size of leaves increased gradually from top to bottom of tree canopies. Foliage production was usually concentrated in the upper crowns of trees where there was a higher proportion of active shoots, more frequent growth flushes and more rapid turnover of leaves than in lower canopy layers. Leaf area in the upper canopy fluctuated widely but increased in the long term, in mid canopy was more or less maintained and in lowest canopy declined. Crops of developing flower buds present on uppermost branches delayed and/or reduced shoot growth. Foliage production occurred in all months of the year. There was a unimodal annual rhythm of growth rate reaching a maximum in summer and a minimum in winter. Variable water supply, however, influenced production to peak in spring, summer or autumn. No shoot growth occurs in E. maculata at Kioloa when daily mean temperature (averaged for weekly intervals) falls below c. 10½C in winter. An upper temperature limit for growth could not be defined. The species apparently lacks dormancy mechanisms. Shoot growth is 'opportunistic' and occurs whenever environmental conditions are favourable. Patterns of leaf production and leaf fall were variable but peaks showed a general synchrony. Leaf fall, however, tended to lag behind leaf production. Leaves of all ages were shed but main losses were from older cohorts. Some 49% (s.d.±18%) of new leaves were lost while still small or immature, mainly during periods of vigorous shoot growth or low water supply. Browse of immature foliage was light. Normal senescence and leaf fall accounted for almost the entire loss of mature foliage.

Fire Intensity Effects on the Understory in Ponderosa Pine Forests

Abstract: The effect of fire intensity on understory vegetation on serri stands of ponderosa pine are presented. Vegetational recovery for 2 burn intensities and unburned sites were compared. The results suggest a change in the understory dominance structure foilowhrg underburning is related to the amount of duff consumed by the fire and independent of fire line intensity and flame length. A significantly greater proportion of duff was removed on high fire intensity sites (80%) than on low intensity sites (40%). However, the variation in fire line intensity was great, with some overlap. Fire line intensity ranged from 30 to 3,034 kcai/m-s on high intensity sites and from 25 to 194 kcai/m-s on low intensity sites. Flame length ranged from 0.1 to 1.7 m on both high and low intensity sites. Graminoid canopy coverage was lowest on high intensity sites. The reduction was apparently the result of prolonged smoldering of the duff layer. There was no significant difference in coverage among treatments for shrubs or forbs. A significant change in frequency among treatments was noted for 11 of 54 species sampled. Prescribed burning can be an effective tool in managing seral stands of ponderosa pine (Pinusponderosa). Fire may be used to reduce fuel loading, thin thickets of saplings, create mineral seedbed for seed germination, remove shade tolerant trees from the understory, prune the lower branches from trees, and reduce needle litter on the soil surface (Biswell et al. 1973). Prescribed burning can also be an effective tool for understory vegetation management. Herbaceous yields are dependent on the percent tree overstory canopy closure and the amount of accumulated litter (Wright 1978). Different intensity fires may be used to manipulate the total tree canopy and litter depth. The effect fire intensity may have on understory development has not been previously studied. The objective of this study was to evaluate the effect of fire intensity on early vegetational development in ponderosa pine communities of the Douglas-fir/ ninebark (Pseudotsuga menriesiij Physocarpus

Microclimate at Arctic Tree Line 1. Radiation Balance of Tundra and Forest

Abstract: Components of the radiation balance were measured or calculated for upland tundra and adjacent open spruce forest for the period from April to September 1979 at Churchill, Manitoba, Canada, which is positioned near the tree line and which is underlain by continuous permafrost. Because of deep winter snow accumulations, snow melt in the forest lags behind that of the tundra by almost a month. The tundra undergoes a stepwise change in albedo from 0.78 to 0.09 over a period of a few days of final snow melt. Its albedo is constant over the summer. On clear days for both surfaces there is a strong diurnal pattern of raised albedos in morning and evening due to specular reflection. On cloudy days there is almost no daily change. The tundra radiative surface temperatures are almost always larger than those of the forest, but differences decrease systematically as the summer progresses. In late winter, on clear days, the forest canopy averages 6.6°C warmer than the surrounding air and 12.6°C warmer than the snow beneath. This results from an absorption of incident and reflected solar radiation by the nontranspiring trees. In winter the forest canopy serves as a convective and radiative heat source to the snow beneath. This hastens snow melt in later winter. The forest has a larger net radiation than the tundra at all times, but this is particularly pronounced with the large solar radiation input of late winter before any snow melt takes place. Destruction of the forest will lead to a greatly modified radiation and surface temperature regime.

Canopy dynamics of Eucalyptus maculata Hook. II: Canopy leaf area balance

Abstract: The leaf area balance of a regenerated stand of E. maculata was monitored for a period of 2½ years on the basis of repetitive non-destructive measurements of production and loss of leaf area in sample branches of a group of trees representative of the forest. Leaf area loss measured in sample tree canopies was closely correlated with forest leaf fall (litter) and verified the phenological harmony between the sample group and the forest. Production and loss of leaf area from sample trees were scaled to the mean annual forest leaf fall to estimate production and loss at forest dimensions. Basal area of E. maculata tree bole was closely correlated with canopy leaf area. Basal area ratio (sample/forest) remained constant and was used to adjust sample group leaf area (determined by direct measurement) to forest dimensions for calculation of the forest leaf area balance. Basal area as an estimator of leaf area was insensitive to seasonal variations but provided a valuable reference datum. Leaf area index (LAI) of the eucalypt overstorey determined from basal area virtually remained unchanged. LAI of forest eucalypts estimated from the detailed leaf area balance fluctuated between 2.65 and 3.12. Maximum values of LAI were attained at the peak of growth seasons when rates of leaf production were high relative to leaf loss. Estimated annual production and loss of leaf area were not equal.

Factors affecting stomatal conductance of bracken below a forest canopy

Abstract: conditions of radiation, atmospheric humidity deficit and soil moisture was also investigated. The range of soil moisture conditions experienced by the bracken was extended by establishing plots which were either irrigated in addition to normal rainfall or from which rainfall was excluded.

Photosynthetic Characteristics of Wet Tropical Forest Plants

Abstract: The leaves of forest trees of the wet tropics are generally large and live an average of about one year. They, however, vary greatly, dependent on site, in their average leaf specific weights and nitrogen contents, encompassing values found for leaves of plants inhabiting arid climates. Those factors which affect photosynthesis, either directly or indirectly, light, humidity, and CO2 concentration, vary greatly from the top of the forest canopy to the forest floor. Those species which inhabit the understory, where the radiation level is only a few percent of that received in the open, utilize brief sunflecks to fix a large fraction of their daily carbon gain. They are able to respond quickly to an abrupt increase in radiation since stomata remain open even at very low light intensities. There is little information available on the photosynthetic responses of tropical trees to CO2, humdity, temperature, and water potential.

Community dynamics of evergreen broadleaf forests in southwestern Japan: III. Revegetation in gaps in an evergreen oak forest

Abstract: The process and rate of revegetation in gaps in an evergreen oak forest were studied by comparing the species composition, tree density, frequency distribution of tree height, and relation between diameter at breast height and tree height among different aged stands. For estimating stand ages, the ages of gap indicators, such as,Symplocos prunifolia andAcer rufinerve, were very useful. It took about 70 years for gaps to be filled by large fully-grown trees. Since the mean residence time of the forest canopy was 180 years, the trees that attain the forest canopy were expected to be canopy trees for 110 years on the average. Tree densities of all broadleaved evergreens exceptS. prunifolia, were independent of stand age. On the other hand, densities of gap indicators,S. prunifolia andA. rufinerve, decreased as stand age increased. Other deciduous broadleaf and coniferous species were scarce as a whole. According to the frequency distributions of height of live and dead trees in different aged stands, it was suggested that shorter trees were more susceptible to death than taller trees. The self-thinning in revegetation process in gaps approximately followed the 3/2 power law, though the power was larger (−1.32) than expected from the law.

Collection of in situ forest canopy spectra using a helicopter - A discussion of methodology and preliminary results

Abstract: An important part of fundamental remote sensing research is based on the measurement and analysis of spectral reflectance from earth surface materials in situ. It has been found that for an effective analysis of the target of interest, different applications of remotely sensed data require spectral measurements from different portions of the electromagnetic spectrum. It is pointed out that the detailed spectral reflectance characteristics of forest vegetation are currently not well understood, particularly in the middle infrared wavelength region. Details regarding the need for in situ forest canopy measurements are examined, taking into account certain difficulties arising in the case of satellite observations. Because of these difficulties, the present paper provides a discussion of methodology and preliminary spectra based on an experiment to use a helicopter as an observing platform for in situ forest canopy spectra measurement.

Leaf conductance responses of Viola species from sun and shade habitats

Abstract: The diurnal pattern of leaf conductance was measured extensively for two Viola species from New England forest and meadow habitats throughout the growing season. The amount of light available to the two species constituted the major micrometeorological difference between their habitats. In the forest, light intensity was highly variable and composed of low-intensity, foliage-filtered light with brief, periodic bursts of high-intensity sun flecks. These contributed less than 25% of total photosynthetically active radiation reaching the forest floor. Comparatively unobstructed, high-intensity light was measured at the meadow site. The forest canopy also buffered air temperature to a greater extent than the grass and shrub vegetation in the meadow, although leaf temperatures in the forest increased briefly during sun flecks. High morning conductance values decreased during the day, perhaps in response to increasing heat load (meadow species) or decreasing light levels (forest species) during the late afterno...

Effects of cork oak (Quercus suber L.) canopy cover on seasonal herbage production, foliar cover, and nutritive quality in the Mamora National Forest of Morocco

Abstract: This research was conducted in the Mamora National Forest of Morocco to: (1) Evaluate the effect of cork oak (Quercus suber L.) crown cover on seasonal herbage production, nutritive quality, and foliar cover on two distinctive sites in each of two years (1982, 1983) and to (2) assess the effects of one and two growing seasons' protection from grazing on herbage production and foliar cover. Sites differed in the dominance (81% cover) of a 1.5-3m tall legumeshrub (Genista linifolia L.) on one (G) and the near absence of this layer on the other (NG). Understory herbage yields on G were over twice as much as the NG regardless of oak cover, plant phenology or years. On the G yields were similar from 25% to full oak canopy cover and declined approximately one-third at less than 25%. Yields on the NG were essentially the same regardless of canopy cover. Yields peaked at the pre-reproductive phase and then declined by approximately one-third by maturity. Herbage under canopied stands contained more crude protein, fat and water but less crude fiber than in the open. Nutritive quality of herbage from the G site was approximately three times greater than that from the NG. Living vegetation ground cover was 70% at canopy cover of 25% or less but was 85% above 25% canopy. Annual grasses decreased in cover from 57% to 30% as crown cover decreased. Annual forbs were less under the densest canopy but were approximately 30% as canopy declined. Perennials tended to be similar (13%) under all canopy treatments. Foliar cover was higher on the G site. Vegetation and soil characteristics showed G having higher production potential. The amount of rest from grazing had pronounced effects. Average herbage yields were 30% more protected two growing seasons as compared to one. Percent cover of annual grasses, perennial grasses and oak seedlings was higher when contrasting two to one seasons' protection. Results suggest that both tree canopy cover and site characteristics such as intermediate shrub layer were major determinants in affecting herbage yields, quality, cover and composition. Rest from grazing also had important effects. Such information will be helpful in developing future Mamora management plan.