Showing papers on "Shrub published in 1977"

Micro-patterns of nitrogen mineralization activity in soils of some shrub-dominated semi-desert ecosystems of Utah

Abstract: Localization of litter fall beneath canopies of desert shrub species results in development of vertical and horizontal soil nitrogen distribution patterns. Concentration of these patterns increases towards the immediate surface of the profile and towards the under-canopy micro-habitat. Similar patterns of N mineralization activity were found in soils collected from shrub communities along an aridity gradient from northern to southern Utah. Mineralization rates were greatest in the 0–2.5 cm horizon of profiles and NO3−-N dominated. Below this level activity decreased abruptly and NH4+-N became quantitatively more significant. Mineralization activity peaks in surface soil reflected greater susceptibility of organic N residues to decomposition as well as the higher concentrations of total N in the 0–2.5 cm layer. Results for Atriplex confertifolia communities indicated that N compounds in litter of this species may be particularly prone to microbial breakdown and mineralization. Mineralization of N proceeded at a greater rate in soils from beneath shrub canopies than in soils from interspace areas between shrubs. Development of higher concentrations of total N and mineralization activity in surface soil generally, and under-canopy soil in particular, is interpreted as a structural and functional organization of the N capital of shrub communities that enhances N availability and therefore water-use efficiency of the vegetation.

Factors Affecting Seed Reserves in the Soil of a Mojave Desert Ecosystem, Rock Valley, Nye County, Nevada

Abstract: During 1972, a 2nd year of low herb production, there was a significant variation of seed reserves in the upper 2 cm of soil, with a doubling from February to June and a density-independent halving by October. In October 1972 there were 8 X 106 seeds/ha (5.3 kg/ha). After very high herb production in the spring, seed densities in October 1973 were 10-16 times greater under shrubs and 23-27 times greater in exposed areas (max 187.5 X 106 seeds/ha, 84.3 kg/ha). The increase was principally by the winter annual grass, Festuca octoflora. In 1972, when there was a small difference in rodent density between two plots (0.8:1.0), there was no effect of rodents on seed density. In 1973, when there was a 1:17.8 ratio of rodent densities, there was a significant effect on seeds under shrubs. Then from October 1973 to October 1974, seed reserves in exposed areas between shrubs decreased by 20% in the plot with few rodents, and by 40% in the plot with many rodents. Eating of seeds by rodents accounted for 30 to 80% of the seed reserve decreases observed. Germination losses were no more than 25%. There is slight evidence that pocket mice selectively decrease abundance of the heavier species of seeds. Seed density was at least five times greater under shrubs than in exposed areas ; density was significantly correlated with the size of shrub canopy. There was also a significant effect of the species of shrub on the density of seeds. During years of low production, under-shrub areas are a refuge for herb seed production, and in such years shrub seeds form a larger portion of the seed crop and new reserves. The difference in response of shrubs and herbs to weather increases the stability of seed reserves. In May 1973 the number of herbs per 100 seeds in the previous October was 16.8 under shrubs and 43.6 in exposed areas; this implies a minimum germination of 24% of seeds over the whole habitat. It takes an exceptional coincidence of events, even in deserts, to cause a severe depletion of seed reserves.

Carbon balance, productivity, and water use of cold-winter desert shrub communities dominated by C3 and C4 species.

Abstract: Common generalizations concerning the ecologic significance of C4 photosynthesis were tested in a study of plant gas exchange, productivity, carbon balance, and water use in monospecific communities of C3 and C4 salt desert shrubs. Contrary to expectations, few of the hypotheses concerning the performance of C4 species were supported. Like the C3 species, Ceratoides lanata, the C4 shrub, Atriplex confertifolia, initiated growth and photosynthetic activity in the cool spring months and also exhibited maximum photosynthetic rates at this time of year. To compete successfully with C3 species, Atriplex may have been forced to evolve the capacity for photosynthesis at low temperatures prevalent during the spring when moisture is most abundant. Maximum photosynthetic rates of Atriplex were lower than those of the C3 species. This was compensated by a prolonged period of low photosynthetic activity in the dry late summer months while Ceratoides became largely inactive. However, the annual photosynthetic carbon fixation per ground area was about the same in these two communities composed of C3 and C4 shrubs. The C4 species did not exhibit greater leaf diffusion resistance than the C3 species. The photosynthesis/transpiration ratios of the two species were about the same during the period of maximum photosynthetic rates in the spring. During the warm summer months the C4 species did have superior photosynthesis/transpiration ratios. Yet, since Ceratoides completed a somewhat greater proportion of its annual carbon fixation earlier in the season, the ratio of annual carbon fixation/transpiratory water loss in the two communities was about the same. Atriplex did incorporate a greater percentage of the annual carbon fixation into biomass production than did Ceratoides. However, this is considered to be a reflection of properties apart from the C4 photosynthetic pathway. Both species displayed a heavy commitment of carbon to the belowground system, and only about half of the annual moisture resource was utilized in both communities.

The use of space by wintering sparrows

Abstract: Differences in microhabitat utilization by sparrows wintering in southeastern Arizona, USA may be sufficient to explain their coexistence. The species either forage in different mac- rohabitats or in the same habitat at different distances from tree or shrub cover. Seed size partitioning within habitats is sufficient to explain coexistence only in one case where the seed size distribution is bimodal. The species that forage in plains grassland habitat differ by foraging in concentric rings about tree or shrub cover. The behavior of each of these species appears to enhance predator avoidance and these behaviors change in a regular pattern with distance to cover both within and between species. Species foraging close to cover are social and tend to be conspicuous both in behavior and morphol- ogy. Two different strategies adapt species to avoiding predators at great distances to cover. In dense grassland, with increasing distance to shrub or tree cover, species in the genus Ammodramus are increasingly solitary and cryptic. In sparse grassland, Chestnut-collared Longspurs are social and cryptic on the ground but conspicuous in flight.

Energy Allocations in Annual and Perennial Lupines (lupinus: Leguminosae)

Abstract: The energy allocation patterns of 3 species of lupine, an annual, a perennial herb, and a shrub were investigated and related to life cycle differences as well as ecological differences among the species. All 3 species occur along the central California coast but differ in their specific environmental tolerances. The annual, Lupinus nanus, and the shrub, Lupinus arboreus, have high growth rates and photo- synthetic rates when compared with the perennial herb, Lupinus variicolor. The 3 species initially have similar energy allocation patterns, but they gradually diverge during the growing season. The annual ultimately devotes up to 61% of its energy to reproductive tissues and 29W to seeds alone while only 3%-4% ends up in the roots. Its life cycle strategy and energy allocation pattern make it a poor competi- tor in stable environments, and it is only found in disturbed sites along the coast. The perennial herb may not reproduce in the 1st year, and in the 2nd year devotes only 18% of its energy to reproduction and only 5% to seeds. At least 40W of its energy is invested in its large taproot system where energy for future growth can be stored. Its prostrate growth form and low investment in reproduction are related to its restriction to the climatically stable but fairly harsh environment found on cool, windy bluffs. The shrub also may not reproduce in the 1st year but later devotes at least 20W of its energy to reproduction and 6% to seeds. It typically devotes =z50% to stems, and this, along with its high growth rate, makes it a superior competitor, particularly in successional habitats away from the ocean bluffs. Its unusually short life span explains its fairly high reproductive effort as well as its absence from climax coastal communities. The 3 lupines have energy allocation patterns that fall within the patterns found for other plants with similar life cycle strategies except that the reproductive efforts are at the high ends of the respective ranges. Investments in seeds alone are more in line with previous findings and reveal that the lupines devote an unusually high percentage of their energy budgets to structures ancillary to reproduction.

Root systems of chaparral shrubs.

Abstract: Root systems of chaparral shrubs were excavated from a 70 m2 plot of a mixed chaparral stand located on a north-facing slope in San Diego County (32°54' N; 900 m above sea level). The main shrub species present were Adenostoma fasciculatum, Arctostaphylos pungens, Ceanothus greggii, Erigonum fasciculatum, and Haplopappus pinifolius. Shrubs were wired into their positions, and the soil was washed out beneath them down to a depth of approximately 60 cm, where impenetrable granite impeded further washing and root growth was severely restricted. Spacing and interweaving of root systems were recorded by an in-scale drawing. The roots were harvested in accordance to their depths, separated into diameter size classes for each species, and their dry weights measured. Roots of shrubs were largely confined to the upper soil levels. The roots of Eriogonum fasciculatum were concentrated in the upper soil layer. Roots of Adenostoma fasciculatum tended to be more superficial than those from Ceanothus greggii. It is hypothesized that the shallow soil at the excavation site impeded a clear depth zonation of the different root systems. The average dry weight root:shoot ratio was 0.6, ranging for the individual shrubs from 0.8 to 0.4. The root area always exceeded the shoot area, with the corresponding ratios ranging from 6 for Arctostaphylos pungens to 40 for Haplopappus pinifolius. The fine root density of 64 g dry weight per m2 under the canopy was significantly higher than in the unshaded area. However, the corresponding value of 45 g dry weight per m2 for the open ground is still high enough to make the establishment of other shrubs difficult.

The energy balance of leaves of the evergreen desert shrub Atriplex hymenelytra.

Abstract: Atriplex hymenelytra is an evergreen shrub distributed in the hot deserts of parts of Mexico and the southwestern United States. The leaves of the species have a number of characteristics that are adaptive in a hot, dry environment, some of which change seasonally. Steeply angled leaves reduce midday solar interception, yet result in relatively high interception when solar angles are low and vapor pressure deficits are at a minimum. The leaves substantially reduce their absorptance of incident radiation during the hot periods of the year by changing their moisture and hence dissolved salt contents. At these times the light intensity required for saturation of photosynthesis is low and a reduction in the radiation absorbed by the leaves therefore results in a greater water-use efficiency.

Early Stages of Regeneration After Burning in Dry Sclerophyll Vegetation. II. Regeneration by Seed Germination

Abstract: Following experimental burns in three dry sclerophyll communities, all except the geophytic species regenerated from seedlings in the first year. The annual and perennial species in the shrub strata regenerated from surviving seeds in the soil and ash, and the eucalypts from seeds released from the trees after burning. Although many seeds were destroyed during the fires, the germination of most species was higher in burnt than in unburnt plots. Fire appeared to stimulate germination through direct heat effects on the seeds, and by removing inhibitors present in the unburnt vegetation. Seedling mortality was highest during the first year. Many seedlings died while in the cotyledon stage, the main observed causes of mortality being desiccation, fungal disease and predation by insects. Seedling survival was enhanced by burning, owing to the removal of the litter and other fire-induced changes which made conditions more favourable for seedling establishment and/or growth. Two years after burning, the relative positions of dominance of the three major species in the tall shrub stratum had changed compared with the pre-burn status of each. Evidence suggests that such shifts in dominance depend on a number of interacting factors which selectively promote or inhibit the recovery of each species.

The Modern and Late Quaternary Vegetation of the Campbell-Dolomite Uplands, near Inuvik, N.W.T., Canada

Abstract: The Campbell—Dolomite uplands comprise a small area (140 km2) of outcropping, faulted dolomite, limestone, and shale east of the Mackenzie River Delta, ~ 40 km south of the northern limit of trees. The major landforms are bedrock ridges and plateaux, steep colluvium, stable slopes, shorelines, and depressions. A principal component analysis of vegetation—cover data from 150 stands suggest that much of the variation within the heterogeneous vegetation is correlated with these broad habitat categories. Stable surfaces bear an open spruce woodland with alder, tree and dwarf birch, and a varied lichen—heath—Dryas ground vegetation. A glacially modified karstic (solution) depression contains a small (8 ha), relatively deep (22 m), apparently meromictic lake, which yielded a 12,000—yr core of sediment. A conventional percentage diagram, an influx diagram, and numerical analysis (principal components) suggest a sequence of pollen assemblage zones as follows: (1) Salix—Gramineae—Artemisia: 13,000 to 11,300 radiocarbon yr ago, (2) Betula (shrub)—Salix—Gramineae—Artemisia: 11,300 to 10,300, (3) Betula—Populus: 10,300 to 9,700, (4) Betula—Populus—Juniperus: 9,700 to 8,900, (5) Picea—Betula (tree and shrub)—Juniperus: 8,900 to 6,500, and (6) Picea—Betula—Alnus: 6,500 to present. Both percentage data and numerical analyses show that none of the pollen assemblage zones 1 to 5 has a modern analogue. With 1 exception, these patterns of change in pollen spectra can be interpreted parsimoniously without reference to regional environmental change. They suggest an initial phase of migration of willow and herbs from adjacent unglaciated Megaberingia (North Yukon and Alaska), followed rapidly by dwarf birch and later poplar. Megaberingian floristic elements (e.g., Plantago canescens, Selaginella sibirica) reached the area during this early phase of migration. Subsequently arriving from the south along the Mackenzie valley were juniper, ericads, spruce, and finally alder, which intensified competition and restricted the early Megaberingian herb types to open, unstable habitats where they persist today. Slow soil development (humus accumulation, rising permafrost table) probably favoured the spread of the palynologically 'silent' elements–lichens, ericads, and Dryas (the dominants of the modern ground vegetation). Changes in the influx values of Picea suggest a climatically induced increase in tree density and/or pollen production during the period 9,000—7,000 BP (Zone 5).

The Use of Water and Minerals by Evergreen and Deciduous Shrubs in Okefenokee Swamp

Abstract: Shoot water potentials, leaf diffusion resistances, and foliar concentrations of Ca++, Mg++, K+, N, and P were measured in an evergreen shrub (Lyonia lucida [Lam.] K. Koch) and a deciduous shrub (Clethra alnifolia L.) in Okefenokee Swamp, Georgia. An upland, evergreen species (L. ferruginea [Walt.] Nutt.) was included for comparison. Clethra alnifolia generally had the highest mineral contents (percentage of dry weight) and the highest water loss in transpiration. During several 24-h monitoring periods, the lowest observed shoot water potentials (L. lucida, -10.1 bars; C. alnifolia, -12.5 bars; L. ferruginea, -17.2 bars) did not suggest "physiological drought" in the swamp species. Only L. lucida showed any evidence of midday stomatal closure. In this warm-temperate swamp, evergreen species have the potential for greater efficiency of mineral use and productivity, largely due to their leaf longevity. In addition, sclerophyllous tissue is probably useful in defense against herbivores.

Biomass and structure of a subtropical eucalypt forest, North Stradbroke Island

Abstract: The plant biomass of a Eucalyptus signata-dominated forest 15 m tall growing on infertile sands off the Queensland coast is characterized in detail. The forest has a biomass of 180 t/ha, 90% of which is found in the nine species achieving > 2.5 m height. Of the total biomass, 42.5 % is below ground. Pteridium esculentum occupies 41 % of the understorey biomass, with 50 shrub and herb species partitioning the remainder. Dimension analysis of 10-11 individuals of each of three tree species- Eucalyptus signata, E. umbra subsp. umbra and Banksia aemula-has served to characterize the above- and below-ground growth forms of each species, and provide regressions of the mass of tree components on easily measured plant parts. The size distribution of tree and shrub stems on the site suggests that the major species have evolved quite different reproductive strategies for main- taining a steady-state population in the face of recurrent fires.

Evaluating stem conducting tissue as an estimator of leaf area in four woody angiosperms

Abstract: Four woody angiosperm species representing an evergreen tree (Castanopsis chrysophylla (Dougl.) A.DC), a deciduous tree (Acer macrophyllum Pursh), an evergreen shrub (Rhododendron macrophyllum G.Do...

Changes in understory vegetation with increasing stand age in New Brunswick forests: species composition, cover, biomass, and nutrients

Abstract: Understory relationships were examined in 12 jack pine and 11 mixed hardwood stands representing a 7- to 57-year age sequence in New Brunswick. All stands were of fire origin. Percentage cover and frequency of vascular species and major mosses and lichens were presented for each stand. Accumulation of shrub layer and herb layer biomass and distribution of N, P, K, Ca, and Mg were also examined. The biomass showed maximum values in the 10- to 20-year period after fire: it then decreased and stabilized. Contribution of the understory biomass to the total ecosystem biomass ranged from 71–88% on 13-and 16-year-old jack pine stands to 1–6% on the older stands. Nutrient accumulation generally showed a similar pattern to biomass, but some differences occurred owing to variation in nutrient concentration. In particular, shrub layer K increased dramatically on the two oldest jack pine stands; this was postulated to be due to increased dominance of Pteridium aquilinum on these stands. Understory contribution to the...

A Comparison of the Pattern of Herb and Shrub Growth in Comparable Sites in Chile and California

Abstract: Two physiognomically similar but floristically dissimilar brushland areas of central Chile and southern California were compared to test the hypothesis that where the dominant overstory vegetations are structurally and functionally similar, the understory or herbaceous vegetations will also be similar. This hypothesis was tested in a relatively undisturbed site, a heavily disturbed site and a burned site within each study area. Values of percent ground surface covered and relative density were obtained using the line-intercept method. Two modifications of this method were used to determine the relationship between herb species location and canopy cover. In the Chilean site herbs were best developed beneath the shrub canopy, were predominantly perennial (75% of the most commonly found species) and were sparse following fire. In the California site few herbs were present in the mature chaparral. But in the 1st year following a fire an abundant herbaceous flora was observed; 75% of the most common species were annuals. The role of man-caused disturbance, climatic differences, floristic histories and the role of fire are discussed as possible explanations for the differences observed.

The Ecology of a Semi-Evergreen Forest Community in Sri Lanka

Abstract: Semi-evergreen forests cover the dry zone plains of Sri Lanka and constitute four-fifths of the island's vegetation. In a sample area of 3 kM2, in the Polonnaruwa Sanctuary, 63 tree species were found; 46 were characteristic of other dry zone forests, and 17 occurred only under special edaphic and biotic conditions. As in other dry zone forests, Drypetes sepiara (Euphorbiaceae) prevailed with a relative density of 21.3 percent. The Shannon index of diversity was 4.23 bits per individual, of which 79.4 percent was attributable to evenness; most species had few individuals. Dominance was shared between species typical of the subcanopy and canopy. Measures of diversity and of dominance between species placed the semi-evergreen community in Polonnaruwa as a type intermediate between tropical rainforest and deciduous monsoon forest. Measures of diameters (DBH) and estimates of the height of trees indicated that all species with typically very large trees had few individuals that were distributed more or less evenly through all the size classes. Typically smaller species had large numerical representation. These facts are discussed in light of dominance relationships and regenerative patterns in the community, and are related to possible evolutionary trends. The distribution of most species was clumped, but that of certain rare species was random. Clumping at 2,500 m2 plot size usually meant clumping at smaller-sized plots. Clumping on a large scale reflected local differences in species dominance. Five shrub associations were distinguished by density and constitute dominant and co-dominant species. Differences were related to the amount of light penetrating through the tree canopy and to edaphic factors. Glycosmis pentaphylla (Rutaceae) was the dominant shrub species in the climax association which flourished under a fairly closed tree canopy and lacked an herbaceous layer. ALTHOUGH EVERGREEN RAINFORESTS and monsoon forests of tropical Asia have received considerable attention from eaologists (e.g., Richards 1962, Ashton 1964, Ogawa et al. 1961, 1965), the semi-evergreen forests have been less intensely studied. In Sri Lanka the forests have been surveyed primarily from an economic perspective (e.g., Andrews 1961). This paper aims first, quantitatively to describe some structural features of a community of semi-evergreen forest in Sri Lanka; second, to examine the dominance relationships between species in this community. These relationships are briefly related to possible successional patterns in the dry zone of Sri Lanka, and to possible evolutionary trends among plants in general. The semi-evergreen forest has been described by Walter (1971: 209) as one in which the "upper tree layer is defoliated for some of the year [during the droughti,' while the lower tree layer retains its foliage." According to certain structural features, annual rainfall and drought duration, it is a type intermediate between tropical evergreen rainforest and deciduous monsoon forest. The tropical island of Sri Lanka has a gradation of forests from lowland and montane rainforests to lowland scrub forests and savanna (fig. 1). The majority of the forests may be roughly classed as semievergreen, however. These cover the most extensive physiographic feature of Sri Lanka, the lowland plains in the dry zone. Several dassificatory schemes have been proposed for the vegetation of Sri Lanka (e.g., Koelmeyer 1958, Gaussen et al. 1964, Fernando 1968). Mueller-Dombois (1968) evaluates these schemes and offers an up-to-date reclassification according to long-term climatic information. The community of forest described herein is located within the Polonnaruwa Sanctuary in the northwestern dry zone at 070 56' N and 81? 00' E. Polonnaruwa was the capital of Sri Lanka for varying periods between the 8th and 13th centuries. It was completely abandoned by the end of the 13th century, and natural vegetation reclaimed the land for the next 700 years. The area was resettled only at the beginning of the 20th century. Most of the natural vegetation has been maintained within the Sanctuary, although the shrub layer has been removed in areas immediately surrounding archaeological sites. The cutting of trees is prohibited, but poaching, particularly of young trees of construction-pole size, is not completely prevented. Parts of the study area are completely devoid of young trees and shrubs. These areas have been largely omitted in the present sample. The study site encloses approximately 3 km2, is bounded by water and cultivation, and is continuous with more extensive expanses of forest by a narrow

Frost Damage of Cerrado Plants in Botucatu, Brazil, as Related to the Geographical Distribution of the Species

Abstract: A very severe frost with temperatures down to -6.00C in July 1975 in the region of Botucatu, Sio Paulo State, caused not only damage to crops but also to natural vegetation. The frost damage to woody cerrado plants was studied on 40 tree species and 10 shrub species. A frost-damage index for each individual was obtained, and the average index for each species calculated. Of the 50 species, 9 were not damaged, 9 were damaged slightly, 17 moderately, 13 substantially, and 2 totally. The average index of frost damage for species was 8.3 percent. In a 400 m2 plot where all the individuals were counted, the frost damage was only 5.8 percent per individual. It was shown that species which are less resistant to frost are less frequent in the area. In many cases a clear relation between the degree of frost damage of species and their geographical distribution could be seen. Species which are distributed more to the north and which in Sio Paulo have their most southern occurrence were nearly totally or substantially damaged. Species which occur also to the south of Sao Paulo State, but whose genus as a whole has its distribution center in northern, warmer regions, had notable damage too. Species which occur in the Brazilian Planalto Central, and which in some cases go even further south than the State of Sao Paulo, showed negligible or no damage. Of two species of the same genus, the more northern species was more damaged and less frequent than the southern species. Frost seems to be one of the selective factors influencing the floristic composition of the cerrado at its southern limit. TH.E PRESENT PAPER gives the results of a study of the damage to "cerrado" (semideciduous xeromorphic woodland) plants by frost, which was carried out in the municipality of Botucatu, Sao Paulo State, Brazil. The city of Botucatu is situated on the Serra (Cuesta) de Botucatu, which in places reaches about 950 m altitude. The plateau is principally formed of Botucatu sandstone, yielding in general a poor sandy soil. The southern side of the Serra forms a steep slope, whereas the northern and northeastern sides slope more gently. The area was originally covered by semideciduous, mesophyll forests, cerrados, and some strips of natural grasslands bordering gallervforests, these distributed in mosaic fashion. The natural vegetation, however, is now widely replaced by cropland and pastures. The climate of the Serra region at about 800 m altitude is characterized by an average yearly precipitation of about 1350 mm and an average temperature of 19.4?C. A rainy season from October to March, with 1100 mm average precipitation, alternates with a dry season from April to September with 250 mm average precipitation. The average monthly temperatures increase abruptly from July, the coldest month, with 17.50C, to September with 20.6?C, then more steadily to January with 21.7?C, and decrease slowly to March and then more abruptly to June and July. The absolute maximum of monthly temperatures for the years 1959 to 1968 was 34.5?C in September and 27.5?C in June. The absolute minimum in the same period was 10?C in October to May, decreasing to O.1?C in August (Tubelis, Nascimento and Foloni 1971). Corresponding values for the lower parts of the Serra, such as where the following observations were made, would be slightly different, but are not presently available. In July 1975, the region of Botucatu. like large parts of south and southeast Brazil, was exposed to the lowest temperatures in 57 years. The resulting frost not only caused damages to crops such as coffee, sugar cane, bananas, etc., but also to the natural vegetation. Frost is a more or less regular phenomenon in the State of Sao Paulo. Since 1892 about 26 frosts have been registered, 12 of which are dassified as severe, 3, including the last one, as very severe, and the rest as moderate (Anonymous 1975:4). BIOTROPICA 9(4): 253-261 1977 253 1 Current address: Botanisches Institut, Universitit Wien, Rennweg 14, A-1030 Wien, Austria. This content downloaded from 207.46.13.151 on Wed, 28 Sep 2016 04:24:43 UTC All use subject to http://about.jstor.org/terms The minimum temperature measured in open vegetation on July 18, the coldest day of the year, was 5.8?C at Fazenda Sao Manuel (a few km SW of city of Sao Manuel at about 700 m altitude). This fazenda is 12 km SW of the studied area at an altitude 150 m higher. The vegetation of the Serra de Botucatu plateau (highest elevation at Rubiao Junior, about 950 m) was damaged more than the surrounding lower region. Forest and cerrado vegetation showed significant symptoms of damage. Leaves died on most trees, causing a brown, dry appearance of forest and cerrado. Frost damaged the leaves, branches or even whole trees of many species. Some other species, however, showed no damage. About two months later, but still before the first rains, the old leaves had fallen, and new ones had sprouted that turned the landscape to a fresh, light green. MATERIAL AND METHODS The frost damage to woody species of the cerrado vegetation was studied in the municipality of Botucatu, in an area 18 km north of Botucatu and 14 km east of Sao Manuel, at 22045'S, 48025'W. It is situated on the northern spur of the Serra de Botucatu on a slight elevation, at an altitude of 550 m. The average temperature, therefore, is slightly higher than that of the city of Botucatu, whose climatic data were previously given. The whole study area of about 60 hectares is a remnant of natural vegetation, more or less undisturbed for at least the last five years. The cerrado varies from denser tree and scrub woodland form (low "cerradao") on top of the elevation to a semi-open tree and scrub woodland form ("cerrado" sensm stricto) on one slope (Fig. 1), to a quite open scrub form ("campo cerrado") on the opposite slope, which is separated from the first slope by a narrow valley with a low scrubby gallery forest. The area was visited twice: first, a few days after frost to see the actual frost damage to leaves and buds, and the second time two months later, to see where on the plants new buds had sprouted and what part of the trees had definitely died. In an area of approximately 1.5 hectares of cerrado sensmr stricto, 151 individuals of 50 different woody species were examined, including 40 tree species of the 45 tree species occurring in this part of cerrado and 10 shrub species. The number of tree species and the delimitation of what we call tree or shrub are based on a quantitative study of this cerrado (Silberbauer-Gottsberger and Eiten, in preparation). The families and species involved are given N ..:v ... .. .::SS.::e.R FIGURE 1. General view of the semi-open tree and scrub woodland ("cerrado" sensa stricto) at the end of the dry season. The tall trees in front are Sclerolobium aureum and Styrax tferuginea.

Long-term Biomass Dynamics in an Arid Chenopod Shrub Community at Koonamore, South Australia

Abstract: A method for estimating biomass from long-term, non-rigorously controlled photo-points was developed. The method was used to investigate the changes in biomass, from 1926 to 1972, of several important forage species on the Koonamore Vegetation Reserve, South Australia. The changes in biomass are correlated with the rainfall. The biomass dynamics of all the species studied tend to be dominated by large input pulses followed by a slow decline in biomass. The average above-ground biomass and productivity for the community studied is c. 90 gm-2 and 30 gm-2 yr-1 respectively, the major part being due to short-lived plants. Interactions between the short-lived plants and shrubs, and their importance to the grazing industry are discussed.

Early Stages of Regeneration After Burning in Dry Sclerophyll Vegetation. I. Regeneration of the Understorey by Vegetative Means

Abstract: The dynamics of regeneration by vegetative means were examined during the first 2 years after summer burning of dry sclerophyll vegetation Three shrub species were fire-sensitive, and the remaining perennial shrub and herb species fire-resistant and able to produce vegetative regrowth The latter were classified as 'increasers' or 'decreasers' on the basis of their ability to multiply vegetatively Of all pre-burn plants, 50-75 % commenced regrowth within 2 months of burning Vegetative recovery appeared to be affected most by fire intensity, post-burn soil moisture, plant age and the origin of the regrowth The vegetative multiplication of most increaser species was stimulated after burning Regrowth survival was high, and the few observed instances of death were caused by water stress The floristic composition of the vegetation remained the same after burning, and although species dominance appeared to change, it was related to differences in the method of species regeneration

Biomass Estimation for some Shrubs from Northeastern Minnesota

Abstract: Biomass prediction equations were developed for 23 northeastern Minnesota shrub species The allowmetric function was used to predict leaf, current annual woody twig, stem, and total woody biomass (dry grass), using stem diameter class estimated to the nearest 025 cm class at 15 cm above ground level as the independent variable

Germination, Establishment, and Demography of Coastal Bush Lupine (Lupinus Arboreus) at Bodega Head, California

Abstract: Lupinus arboreus is a large, fast-growing, short-lived shrub dominant in the northern coastal scrub of California. The age structure of its stands and the factors which contribute to that age structure were examined at Bodega Head, a coastal peninsula in Sonoma County, 73 km north of San Francisco. No plants older than 7 yr were found. Major causes of mortality of established plants were herbivory by two species of insect larvae and summer drought. Most plants flower and fruit after the age of 2 yr. Nearly all seeds dropped under lupine canopies are taken by mice, and the absence of establishment there is not caused by allelopathic factors or competition for light or moisture. Estab- lishment in surrounding grassland is limited by competition with grasses for light and moisture and, again, allelopathy is not a factor. Germination was enhanced by seed burial and exposure to alternate heat and cold, wetting and drying, and salt spray. Following seedling establishment, increase in biomass is approximately exponential for the first 4 yr, then growth rate declines. The mosaic of scrub and grassland at Bodega Head appears to be approaching a steady state, following release from grazing by cattle and protection from other disturbance since 1961.

Nutrient content of forest shrubs following burning

Abstract: Prescribed burning under mature Larch/Douglas-fir forests produced changes in elemental uptake. Elemental analyses of individual species and existing biomass three years post-burn from hot, medium, and lightly burned sites and unburned controls showed a significant shift in species composition with burn intensity. Few species from hotly burned sites had elevated levels of ions, except phosphorus and iron, but the aboveground shrub and herb biomass did have greater total cations, percent ash, and individual cations (except Ca and Mg) on hotly burned sites. Although the hotly burned sites had the greatest total biomass, only iron, manganese, total nitrogen, sodium, and phosphorus were significantly higher (5%7 level) in biomass from hot burns compared to control biomass (g/m2 basis). Hot burns alter the soil pH to the alkaline range making some elements like iron less soluble and available. Some species growing on hotly burned sites appeared able to alter nutrient uptake making more iron, phosphorus, and other elements available for growth, even with low available levels, compared to control sites. Three-year-old western larch (Larix occidentalis Nutt.) seedlings were able to accumulate high levels of Fe, K, and P relative to controls. Marchantia polymorpha L. concentrated some ions on hotly burned soils, but it was not possible to locate this plant on unburned areas for comparison. CONTROLLED burning is a means of reducing fuel accumulations on the forest floor and is used as an effective management tool. The use of fire reduces organic matter and releases biologically essential nutrients to the soil as a natural fertilizer. When controlled burning is done with the objective of stimulating tree growth, the treatment often fails to produce a growth in trees. Many shrub species in fire-adapted forests sprout readily after fire: Vaccinium L. sp., (huckleberry), Spiraea betulifolia Pall. (spiraea) and many others have adventitious roots with latent buds which are released when the terminal bud is destroyed. The first year following a light or medium burn, these shrubs may resprout readily, producing a rapid increase in biomass. This rapid flush of growth is a logical reservoir for some of the nutrients released into the soil from burning. There is a question whether higher soil nutrient loading from hot burns of heavy fuels will result in more shrub biomass, and hence in greater total nutrient storage in the shrub compartment. This study examines that question. Athough it is most desirable to get the nutrients released from burning into the roots of trees to stimulate tree growth, the nutrients must pass into 'Received for publication 14 January 1977; revision accepted 18 July 1977. The authors are grateful to Paul Powlowski and Magdalena Catalfomo for assistance with this study. 2 The study was a cooperative effort between the McIntire-Stennis Program and the U.S. Forest Service, Northern Forest Fire Laboratory. the zone of shrub and herb roots before reaching the tree root zone. From a nutrient cycling standpoint, it is better to have the elements taken up by shrub or herb roots than to have massive nutrient losses below the tree root zone. Fire rarely kills all of the roots of shrubs, but when it does, nutrient losses from erosion and leaching can be significant (Stark, 1977). Little is known about the elemental content of vegetation following fire. The successional patterns following fire in northeastern Minnesota were studied by Ahlgren (1960) and elsewhere by Cushwa, Brender, and Cooper (1966). The influence of burning in restoring forage values has been widely studied (Grelen and Epps, 1967; Grelen and Enghardt, 1973; Pearson, Davis, and Schubert, 1972; Stark, 1973). A study in Washington by Cole, Gessel, and Dice (1967) discussed the effects of burning on Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco). An early fire study by Stark (1973) dealt with nutrient accumulations by Jeffrey pine (Pinus jeffreyi Grev. & Balf.) seedlings. The question of biomass and nutrient levels following burning remains unanswered and was the stimulus for this study (Pearson et al., 1972). The objective of the Lubrecht study2 was to examine the above and below ground effects of burning different fuel loadings under varied meteorological and fuel moisture conditions in Larch/Douglas-fir forests (Stark, 1977). This would allow the U.S. Forest Service to develop a prescription which would help the land manager

Ecophysiological studies of Sonoran Desert plants : II. Seasonal photosynthesis patterns and primary production of Ambrosia deltoidea and Olneya tesota.

Abstract: The gas exchange and water relations of two Sonoran Desert plants was measured throughout a 12-month period. Seasonal photosynthesis patterns of both plants followed the seasonal variation in plant water potential. Ambrosia deltoidea, a drought-deciduous shrub, is mainly winter-spring active since maximum photosynthesis rates of 38 mg CO2 dm-2 h-1 were measured at this time. This plant is characterized by marked seasonal variations in plant water potential, and was deciduous for approximately 120 days when plant water potential was below-50 bars. Olneya tesota, a non-riparian microphyllous tree, is evergreen and photosynthetically active throughout the entire year, although demonstrating maximum photosynthesis rates of 12 mg CO2 dm-2 h-1 in spring and summer. The deep-rooted tree species maintains a favorable year-round water balance since minimum plant water potentials were seldom below-33 bars. The two species maintain a relatively high water use efficiency throughout the year, despite the high evaporative gradient characteristic of the Sonoran Desert.The leaves are the major site for carbon assimilation, contributing 87 and 81% of the annual carbon gain for the shrub and tree species, respectively. Above-ground gross primary production throughout the 12-month period was estimated solely from the leaf 14CO2 assimilation studies. This production estimate was compared to above-ground net primary production determined by the harvest method. For both plant species gross production was interpreted to exceed net production by nearly a three-fold difference. On a per plant basis gross production was estimated to be 1.14 and 7.42 kg dry wt plant-1 yr-1 for A. deltoidea and O. tesota. The large difference between net and gross production is probably related to year-round utilization of carbon.

Biomass and net primary productivity of artificial tropical rainforest in Xishuangbanna

Abstract: The stand biomass and primary net productivity of artificial tropical rainforest in Xishuangbanna were estimated, based on sample tree method and harvesting method. The results showed that the standing biomass was 390.4 t.hm-2, of which, 362.5 t.hm-2(92.8%) were contributed by tree layers. The biomass of shrub and inter-layer plants (including epiphytes) was 19.3 t.hm-2(4.9%) and 3.6 t.hm-2(0.9%), respectively, and that of herbaceous layers was 5.0 t.hm-2. The primary net productivity of the stand was 2227.3 g.m-2.yr-1, of which, 1553.5 g.m-2.yr-1(69.7%) were contributed by tree layers. In the allocation of primary net productivity in different parts of trees stems showed the highest net productivity, accounted for 42.0%. Leaves and branches were accounted for 30.2% and 13.5%, respectively. The leaf area index (LAI) was 7.061. The optimum regression models of different dominant plants and organs of the sample trees of tree layer in the artificial tropical forest were built.

Influence on soil properties of prescribed burning under mature red pine.

Abstract: Prescribed fires in mature red pine stands reduced shrub competition and the organic layer thickness. The fires reduced nutrient in the forest floor, increased them in the mineral soil, but had no effect on overstory growth.

Food habits of mule deer in a semidesert grass shrub habitat.

Abstract: Highlight: Mule deer (Odocoileus hemionus) selectively consumed cactus fruit, has developed, in this century, an browse leaves and fruit, and forbs, when present, on semidesert grass-shrub habitats extensive cover of cactus and perenniin southern Arizona. Plant species utilized were generally those that have invaded and al woody species (Reynolds and Martin proliferated on semidesert grasslands during the twentieth century. The seasonal diet seemed deficient in phosphorus, which may affect deer reproduction and general well 1968) characteristic of many of the f ormer semidesert grasslands of the being.

Cattle diets and distribution on spring–fall and summer ranges near kamloops, british columbia

Abstract: A 2-yr investigation of the herd distribution and diet selection of beef cattle on range was conducted near Kamloops, British Columbia. Two ranges were studied: one grazed in spring and fall, and the other in summer. Diet selection was determined by grazing two rumen-fistulated beef cattle, by clipping plots before and after grazing on the spring–fall range, and by conducting browse surveys on the summer range. Cattle distribution was determined on the spring–fall range. During the 2 yr, the diet composition averaged 93% grass, 2% forbs, 2% shrubs, and 3% trees. Grass was consumed more in the spring (95%) than in either summer or fall (93 and 92%, respectively). Interseasonal change in the consumption of the four plant types (grass, forbs, shrubs, trees) was greatest in the summer and fall. In the summer, consumption of forbs and trees increased, while consumption of grasses remained constant and consumption of shrubs decreased. In the fall, grass and shrub consumption increased, while forb and tree consu...

Root System of Shrub Live Oak in Relation to Water Yield by Chaparral

Abstract: The root system of shrub live oak (Quercus turbinella) was studied in an initial effort to classify the major Arizona chaparral shrubs as potential users of soil water based on root system characteristics. The root system was of the generalized type with a taproot, many deeply penetrating roots, and a strong lateral root system. Roots penetrated 21 feet to bedrock through cracks and fractures in the rocky regolith. A dense network of small surface laterals radiated from the root crown and permeated the upper foot of soil. Because of its root system, shrub live oak is well adapted to utilize both ephemeral surface soil moisture as well as deeply stored moisture. Emphasis is placed on the importance of a knowledge of the root systems of chaparral shrubs and depth of the regolith in planning vegetation conversions to increase water yield.

Above ground growth rate of a dwarf shrub community

Abstract: The aim of the paper is to study the estimation of daily production of structural biomass by means of the height growth of plants. In particular, attention is paid to the relationship between dry matter production and self regulation of plants and the environment. A method for estimating the daily production of structural biomass based on these factors is presented for a dwarf shrub community of Vaccinium myrtillus (L.) and Vaccinium vitis-ida&a (L.). The amount of dry matter produced and the production ability of the plant community during different phases of the growing period is presented and discussed.