Edaphic Condition Research Articles

Species composition and forest structure in tropical moist deciduous forest of Bangladesh—a case study in Thakurgaon

This study was conducted in the tropical moist deciduous forest in Bangladesh to describe the species composition, diversity, and the forest structure. There were three plots established in Ranishonkoil, Ruhia, and Baliadangi forest beat in Thakurgaon. A total of 126 tree species, 1,991 stems (663 ha−1) of ≥10-cm girth were listed. Tree communities in these forest region differed in dominance, composition, diversity, and structure; and tree stand density varied from 651 to 685 ha−1. Species diversity (H1) ranges from 3.11 to 3.48. Meliaceae, Myrtaceae, and Rubiaceae were the most abundant families within the three plot area. Study site 2 is more diverse at spatial scale and taxonomic levels due to high rainfall and favorable edaphic condition. This study will help the foresters as baseline information for monitoring and sustaining diversity of tropical moist deciduous forests in Bangladesh.

Primary productivity of the agrobiogeocenoses on the experimental area of the land reclamation after mining impact

The results of the primary productivity investigation of agrobiogeocoenoses in different edaphic condition of reclamated soil have been presented. The spatial variability of the plant community biomass has been shown by means of GIS-approaches. By means of regression analysis the dependence of the phytomass on edaphic factors, such as aggregate composition and humus content, have been quantitatively assessed. The data obtained reveal that the rise of the soil aggregate with size of more than 3 mm leads to primary production increase of agrobiogeocenoses in the recultivated areas.

SOUND SOIL MANAGEMENT FOR PAPAYA: CASE STUDY OF THE NORTH OF ESPIRITO SANTO, BRAZIL

Agriculture and cattle husbandry as practiced in North of Espirito Santo State is an unsustainable model of food production due to inadequate soil management. Several factors such as monoculture, clean-cultivated orchard, intensive mechanization and inappropriate use of chemicals and irrigation lead to a nonproductive agro-ecosystem. Papaya cultivation, for instance, causes great impact on soil structure due to heavy traffic for harvesting, chemical applications, and other cultural operations. Also, traditional growers use plowing for land preparation and weed control create plow sole, which impairs water penetration into the subsoil. Indeed, uncovered soil after plowing the beating force of a raindrop may disaggregate soil particles and globules of mud are hurled in all directions initiating the erosion process. Yet inappropriate center pivot irrigation system common in the region accelerated soil degradation. Although the reduction of the productive capacity of soils through the loss of fertility and structure is considerable, the most serious problem is erosion. Nutrients can be added by fertilization, but the loss of topsoil cannot be so easily or quickly remedied. To cope with this scenario, the following sound practice has been suggested: (1) Site selection (edaphic condition) for orchard establishment is determinant for economically and environmentally sustainable production. Papaya trees fare best in deep, well-aerated sandy loam soils. (2) Use of minimum tillage system for land preparation. (3) Sod culture with grass mowed periodically with rotary mower that move the cutting grass down the papaya rows as mulch and maintain a vegetative cover within the row which retards erosion by breaking and cushioning the beating force of the rain and increasing the absorptive capacity of the soil. Mulching may improve soil biological activity since organic matter and microorganisms establish a favorable carbon balance in the soil for productivity maintenance. (4) Add 5 to 7 t/ha of organic compost being 60% in the establishment and 40% three months after transplanting (sexing time). Organic matter has a number of advantages: a) increases water-holding capacity; b) readily permits the infiltration of water; c) is a source of mineral elements; d) it may retain large quantities of minerals, thus preventing their loss from the soil by leaching. (5) Drip irrigation system to deliver water daily (two to four pulses during day time) to replenish loss by transpiration and evaporation from the soil surface. (6) Control of chemical soil dispersion caused by high Na:Ca ratio in the irrigation water by systematic application of calcium into the soil is also an important decision. (7) Tractors with wide tires moving on alternate rows by using 50% of the area may help on reducing hardpan during period of high traffic in the orchard. All suggested sound management has been successfully implemented by farmers in North of Espirito Santo which has drastically reduced soil erosion and maintained soil fertility and yield with high quality papaya.

Chlorophyll in desiccated seeds of a euhalophyte, Suaeda physophora, and its significancy in plant adaptation to salinity during germination

The seed cotyledons of a euhalophyte, Suaeda physophora, were found to be dark green. The pigment extracted from the cotyledons was proved to be chlorophyll for the absorption spectra curve of extracts the same as that for leaves. Photosynthetic oxygen-exchanging could be detected after the seeds were moistened for 6 h. Microstructure of organelles in cotyledons of ungerminated seeds was detected by transmission electron microscopy. Histochemical pigmentation was used to investigate the degree of damage on the membrane of radicles. A xerophyte, Haloxylon persicum, whose cotyledons of desiccated seeds also contain chlorophyll was used as a comparative species. The results showed that S. physophora maintained the ultra-structure of chloroplasts, the integrity of plasma membranes of radicles kept much better than that of H. persicum, which showed the great adaptability to salinity of the euhalophyte even at the seed-germination stage. Seeds were incubated in 0 and 700 mmol/L NaCl for 10 days in darkness at 20 degrees C, then ungerminated seeds in NaCl solution were transferred to deionised water and reincubated for another 8 days and was recorded the germination recovery. Dry seeds moistened with deionised water germinated gradually in the dark and germination was maximal after 3 or 4 d. Seeds at 700 mmol/L NaCl for 10 d and transferred back to deionised water germinated abruptly, most seeds germinated in one day and photosynthesis was also detected. It is concluded that recovery germination of S. physophora ensured the seeds could germinate rapidly after salinity declines, for example under the mild but transitory favorable edaphic condition in early spring. Photosynthesis function in seeds might also promoted radicle growth and seedling establishment.

The Holocene history of Pinnus forests in the Spanish Northern Meseta

Pollen analysis from a 14.1 m core recoverecd from a vally mire at Espinosa de Cerrato (Palencia, Spain), suggests that Pinus woodland has dominated thils area of the Northern meseta throughout almost the entire Holocene in contrast to many other locations in lbetia where early-Holocene conifer woodland was progressively replaced by deciduous taxa. This unique pattern ofvegetationi developmenit is attributable to a combination of continental climate, edaphic condition of thesas. Mesetas. and perhaps fire. These data suggest that vegetation in this area has been remarkably stable over an extended timescale and that arguments aconcerning Pinus communities not being native in the region are unfounded. Anthropogenic impact can be detected at c. 4500 14C yr BP, affecting evergreen Quercus woodlands, and between c. 3000 and 2000 14C yr BP affecting Pinus woodlands. The pine forests were replaced by plant communities resembling the present-day landscape (shrubs and cereals) from c. 1500 14C yr BP.

Local and geographical distributions for a tropical tree genus, Scaphium (Sterculiaceae) in the Far East

Tropical rain forests have an amazingly large number of closely related, sympatric species. How the sympatric species coexist is central to understanding the maintenance of high biodiversity in tropical rain forests. We compared local and geographical distributions among trees in Scaphium (Sterculiaceae), a tropical canopy tree genus. Scaphium is endemic to the Far Eastern tropics and comprises six species. Scaphium scaphigerum is distributed in drier regions than the other species' geographical distribution ranges. Scaphium longiflorum is distributed swamp forests, whereas the others were distributed in lowland and hill tropical rain forests on undulating land. Scaphium borneense, S. longipetiolatum, and S. macropodum co-occurred in a 52-ha plot in Lambir, Sarawak and clearly showed an allopathic pattern of distribution related to elevation in it. In the plot, the elevational difference was correlated with soil variation. Consequently, the difference in edaphic condition promoted the habitat segregation of the species. Thus these five Scaphium species have divergent habitats at various spatial scales and coexist because they reduce direct competition by habitat niche differentiation. Although the non-equilibrium hypothesis for the coexistence of Scaphium species cannot be rejected categorically due to the lack of enough information about S. linearicarpum, the equilibrium force may play the predominant role which permits their coexistence.

Air pollution, forest condition and forest decline in Southern Europe: An overview

Over the last decades much of the work on the impact of air pollution on forests in Europe has concentrated on central and northern countries. The southern part of Europe has received far less attention, although air pollutants—especially the photochemical ones—can reach concentrations likely to have adverse effects on forest vegetation. Although international forest condition surveys present serious problems where data consistency is concerned, they reveal considerable year-by-year species-specific fluctuations rather than a large-scale forest decline. Cases of obvious decline related to environmental factors are well circumscribed: (1) the deterioration of some coastal forests due to the action of polluted seaspray; (2) the deterioration of reforestation projects, especially conifers, mainly due to the poor ecological compatibility between species and site; and (3) the decline of deciduous oaks in southern Italy and of evergreen oaks in the Iberian peninsula apparently due to the interaction of climate stresses and pests and diseases. However, besides obvious deterioration, changes in environmental factors can provoke situations of more subtle stress. The most sensitive stands are Mediterranean conifer forests and mesophile forests of the Mediterranean-montane plane growing at the edges of the natural ecological distribution. Evergreen sclerophyllous forests appear less sensitive to variations in climatic parameters, since they can adapt quite well to both drought and the action of UV-B rays. Several experiments were carried out to test the sensitivity of Mediterranean forest species to air pollutants. Most of those experiments used seedlings of different species treated with pollutant concentrations too high to be realistic, so it is difficult to derive adequate information on the response of adult trees in field conditions. Ozone has been proved to cause foliar injury in a variety of native forest species in different Southern European countries, while the effects of other pollutants (e.g. nitrogen, sulphur, acidic deposition) are less obvious and likely to be very localized. In the case of ozone, visible symptoms were almost completely missed by large-scale surveys and—at the same time—non-visible symptoms are suspected to be even more widespread than the visible ones. Owing to this and to the complex relationships existing between species sensitivity, ozone exposure and doses, length of the vegetative periods, influence of climatic and edaphic condition on the tree's response, the impacted areas are yet to be identified. Therefore, the large-scale impact of air pollutants on the forests of Southern Europe remains largely unknown, until more specific investigations are carried out.

Nutrient content and seasonal fluctuations in the leaf component of coark-oak (Quercus suber L.) litterfall

Nutrient content and seasonality of the leaf component in cork-oak litterfal were studied over a two year period in two cork-oak forest sites differing in biomass and edaphic condition in the north-eastern Iberian peninsula. Fallen senescent leaves compared to young leaves showed higher non-mobile nutrient concentrations and lower mobile nutrient concentrations, specially P, N, K, and Mg. At both sites, seasonal fluctuations affected both leaf production and leaf mineral content. The maximum leaf fall period correspond to the start of the vegetative growth and to the lowest N and P concentration in the falling leaves. The opposite was true for the winter, when litterfal was minimal and N and P content in falling leaves was at a maximum.

Why Don't East Texas Savannas Grow Up to Forest?

To explain the low density of trees on two adjacent East Texas savannas (designated as bluestem savanna and grass-sedge meadow), several indicators of disturbance history, site favorableness for woody plants and site flammability were compared among the savannas and a neighboring upland forest. The upland forest was previously a savanna as shown on 1930, 1941, 1952 and 1956 aerial photographs. However, between 1956 and 1968 tree density increased in the upland forest but not on two present-day savannas. Tree age distributions from the three communities have a noticeable gap during 1956, which was a drought year, suggesting a climatic limitation on tree regeneration. The gap is particularly extensive (1951-1956) for the bluestem savanna. Widespread fire in conjunction with this drought may have more severely limited tree regeneration in this community. The grass-sedge meadow occurs on acid soil with a high clay content, and this edaphic condition is apparently responsible for its distinctive vegetation, low sapling and tree density and slow tree growth rates. In contrast, tree regeneration on the bluestem savanna does not appear to be edaphically limited since soil properties and woody species composition are similar to those of the adjacent forest. In fact, both rapid tree growth and the abundance of saplings indicate that the bluestem savanna is currently a more favorable habitat for trees than the forest and provide further support for the role of fire in limiting tree density in this community. Flammability estimates based on measured fuel bed characteristics suggest that both savannas are more flammable (especially under humid conditions) and consequently likely to burn more frequently than the forest. Although fires have occurred in both the savannas and the forest (as indicated by widespread soil charcoal), the upland forest has remained fire-free long enough to develop a densely packed moistureretentive fuel bed. The present nonflammability of this forest and older upland stands, in contrast to that of the savannas, suggests that some areas may effectively escape the influence of fire.

Edaphic conditions of different islands under different hydrological regimes in the coastal zone of Bangladesh

Physical and chemical properties of soils from the southern coastal zone of Bangladesh were studied to understand the effect of inundation on different soil variables. Soil samples were collected from three different islands representing different hydrological regimes, viz. Char Motherbunia (Island I) is inundated twice daily, Char Taposhi (Island II) is inundated by high tide and Char Kashem (Island III) is totally raised, inundated only during storm surges. Three transects in each island perpendicular to the river Buragauranga were established. Five soil samples, each with a composite of five sub-samples, were collected from each transect, 15 variables were tested from total 15 samples of each island. To test the variations among the islands and within the island, ANOVA was used. Soils of the three islands were found to be rather similar in chemical properties, although there were some significant differences in pH and potassium concentration. The results indicated that broad-scale hydrology did not effect the variation found in the edaphic condition rather duration and amplitude may be responsible for some observed variation. A correlation matrix of the soil variables showed a strong correlation among chemical elements and that the majority of elements were significantly correlated with pH. Key words: Edaphic conditions; Coastal zone; Hydrological regimes; Tidal amplitude DOI: http://dx.doi.org/10.3329/dujbs.v19i1.8941 DUJBS 2010; 19(1): 27-40

Decline of Old‐Growth Redwood Forests in Relation to Some Soil Microbiological Processes

Observations on a number of old—growth coast redwood Sequoia sempervirens (D. Don) Endl. forests indicated unusual features of stand decline. To test the hypothesis that this decline resulted from some deterioration in the forest—site relationship, a series of studies was made on forest soils under old—growth redwood and at various stages of the hardwood succession following logging. Proliferation of redwood seedling roots was restricted in old—growth redwood soil and some evidence of seedling susceptibility to a root pathogen was found. Soil respiration patterns indicated that the availability of carbonaceous material from the organic matter in a form suitable for microbial digestion may be the primary factor limiting biological activity. The end results may be failure of, or abnormalities in, the process of nitrogen mineralization, and the establishment of an edaphic condition in which pathogens can attack seedling roots. Although nitrogen was found to be strongly immobilized in soils from an age sequence of tan oak developed on former redwood sites, it seems possible that tan oak litter could stimulate a higher level of microbial activity and so accelerate the decomposition of redwood humus. Deterioration in both the soil microbiological processes and the plant—soil relationship in a redwood forest are discussed in terms of the long—term incorporation of redwood litter into the soil.