Chapter 6

• Biome is a term used to classify the Earth's major ecosystems. A biome is defined primarily by the climate and predominant vegetation of a region.
• The flora and fauna occurring within a specific biome reflects the adaptations of those organisms to that particular environment.
• Properties of soil moisture and temperature regimes are largely determined by latitude, climate, topography, and upon the native vegetation that is adapted to these local conditions.
• The influence of native vegetation on the amount, type, and distribution of organic materials within the soil, and of the organisms living in the soil may also be drawn from the Biome classification.
• Basic characteristics of world biomes

  • Tundra
  • Boreal
  • Temperate
  • Mediterranean
  • Desert
  • Tropical
  • Humid
  • Semi-Arid
  • Permafrost
• The Earth's biomes are categorized into two major groups: terrestrial and aquatic.
• Terrestrial biomes


  • Tropical Rainforest
  • Temperate Forest
  • Desert
  • Tundra
  • Taiga (Boreal Forest)
  • Chaparral
  • Grassland
  • Savanna
• Aquatic biomes


  • Freshwater
  • Marine
• Forests have diverse structures, compositions, and functions. They can be classified on the basis of their regions of occurrence, species composition, habitat type, leaf type, persistence, etc.
• World forests are classified into three broad types; tropical forests, temperate forests, and boreal forests, mainly on the basis of geographical positions.
• Besides these types, there are montane forests, mangrove forests, and swamp forests.
• Six major types of Philippine forest

  • Dipterocarp forest
  • Molave forest
  • Pine forest
  • Mossy forest
  • Beach forest
  • Mangrove forest
• Mangrove forests are found in tropical and subtropical tidal areas at the mouths of streams (estuaries) and on the shores of protected bays.
• There is about 80 different species of mangrove trees. All of these trees grow in areas with low-oxygen soil, where slow-moving waters allow fine sediments to accumulate.
• Mangrove forests only grow at tropical and subtropical latitudes.
• Types of forests


  • Tropical forests
  • Temperate forests
  • Boreal forests
  • Montane forests
  • Mangrove forests
  • Swamp forests
• Types of Philippine forests

  • Dipterocarp forest
  • Molave forest
  • Pine forest
  • Mossy forest
  • Beach forest
  • Mangrove forest
• Mangrove forests


  • Found in tropical and subtropical tidal areas at the mouths of streams (estuaries) and on the shores of protected bays
  • About 80 different species of mangrove trees
  • Grow in areas with low-oxygen soil, where slow-moving waters allow fine sediments to accumulate
  • Cannot withstand freezing temperatures
  • Recognised by their dense tangle of prop roots that make the trees appear to be standing on stilts above the water
  • Tangle of roots allows the trees to handle the daily rise and fall of tides
  • Roots slow the movement of tidal waters, causing sediments to settle out of the water and build up the muddy bottom
  • Stabilize the coastline, reducing erosion from storm surges, currents, waves, and tides
• Beach forests


  • Ecosystems found adjacent to beaches
  • Some fruits and seeds are adapted to be dispersed by sea currents by evolving sea water resistance fruits
  • Able to prevent coastal erosion to a certain degree
  • Species poor tree community shows adaptations to salt spray and salty groundwater, high temperature and radiation as well as mobile substrates
  • Typically found above the high-tide mark in sandy soils
  • Experience wide variations in temperature, salinity, and humidity which influence the composition of plant species
  • Principal trees are talisai, dapdap, botong, palomaria, agoho, bani, and tawalis
• Molave forests


  • Occur in regions with distinct wet and dry seasons, each of several months' duration
  • Vegetation is largely leafless during the dry season, but grows luxuriantly in the wet season
  • Under certain local soil conditions during the dry season, there are places approaching desert-like conditions
  • Important species are molave, narra, tindalo, ipil, akle, and banuyo
• Dipterocarp forests


  • Occurred from sea level to elevations of 400 m or higher, with individual dipterocarps occurring up to 1,500 m
  • Quite tall (45-65 m) and dense, with three canopy layers
  • Lianas and bamboo are rare in mature forest but common in poorly developed evergreen forest
  • Ferns, orchids, and other epiphytic plants are found on the larger trees
  • Upper hill dipterocarp forest is found at elevations of 650 to about 1,500 m and contains dominant Shorea polysperma and oaks, chestnuts, and elaeocarps
• Pine forests


  • Occur on parts of Luzon and Mindoro where fires occur fairly frequently (yearly up to about once every 20 years), from about 900 m up to 2500 m, usually on rather steep slopes
  • Principal species is the Benguet pine, with tapulau found in the high mountains of Zambales and Mindoro
  • Understory is nearly pure grass in places where fires burn every few years, with no humus and little leaf-litter
  • Bracken and other ferns are common in places with less frequent fires, and as fires occur still less frequently, small, native woody plants begin to invade
• Mossy forests


  • Found on high and very rough mountainous regions, sometimes called "upper montane forest" or "cloud forest"
  • Characterized by short trees, often with twisted trunks and branches that reach 8 m in protected spots but only 2-3 m on ridge tops
  • Moss covers most tree trunks and branches, often hanging in sheets, and most ground surfaces are covered by moss and leaf litter over a thick layer of humus
  • Ants and termites are absent, and earthworms are abundant
  • Principal species are Dacrydium, Podocarpus, Eugenia, Decaspermum, Quercus, Myrica, Symplocos, and Tristania decorticata
• Forest formations of the Philippines

  • Tropical lowland evergreen rain forest
  • Tropical lower montane rain forest
  • Tropical upper montane rain forest
  • Tropical subalpine forest
  • Forest over limestone
  • Forest over ultramafic rocks
  • Beach forest
  • Mangrove forest
  • Peat swamp forest
  • Freshwater swamp forest
  • Tropical semi-evergreen rain forest
  • Tropical moist deciduous forest
• Forest soil


  Soil that is under the influence of forest vegetation
• Characteristics of forest soils

  • Deeply rooted trees
  • Significant "litter layers" or forest floors (O horizons)
  • Recycling of organic matter and nutrients by wide varieties of soil-dwelling organisms
  • Influenced by forest vegetation, climate, parent material, and other organisms
  • Provide physical support, supply nutrients and moisture for growth, and store elements for recycling back to trees
  • Diverse plant materials comprising forest floors are habitats for animals and microorganisms, and facilitate and buffer precipitation inputs
• Tropical forest soils


  • Formed under high temperature and precipitation rates from volcanic parent material
  • Fragile nutrient cycle
  • High clay content and lower soil organic matter accumulation
  • Low pH and low plant nutrients due to translocation of clay particles that carried nonacid cations into the soil
  • Examples are Ultisols and Oxisols
• Temperate forest soils


  • Higher organic matter due to lower temperatures slowing decomposition
  • Highly weathered due to seasonal temperature and precipitation
  • Accumulation of calcium carbonate and clay particles in deeper horizons due to leaching
  • CEC up to 35%
  • Reflect the seasonal variability in temperature and precipitation that make them productive and highly variable
  • Reflect the forest vegetation under which they develop
  • Examples are Alfisols and Spodosols
• Soil formation


  1. Climate

  2. Organisms

  3. Parent material

  4. Time

  5. Relief
• Forest floor


  Organic layer on the soil surface containing fresh organic materials from dead plants and animals that are easily degraded by microorganisms
• Soil organic matter


  • Most important role of vegetation on soil is the accumulation of organic matter
  • Tree leaves represent the most important source of carbon in the soil
  • Type of vegetation affects soil acidity - litter from conifer trees requires more time to decompose, litter from deciduous trees is easily decomposed
• Humus forms in forest

  • Mor-humus formation
  • Mull-humus formation
  • Moder-humus formation
• 1. humus formation


  Raw humus condition, occurs in soil that has few micro-organisms or animals, such as earthworms, to decompose the organic matter that lies on the soil surface
• Mor soils


  • Acidic (low pH), characteristic of coniferous forest areas, especially in cold regions and at high altitudes
• Mull-humus formation


  • Characteristic of hardwood forests, deciduous forests, or grasslands in warm, humid climates, porous, crumbly humus rapidly decomposes and becomes well mixed into the mineral soil, bacteria, earthworms, and larger insects are abundant, pH is high (alkaline)
• Moder-humus formation


  • Intermediate between mor and mull extremes, contains more organic material than a mull formation, but this material is not as well mixed with mineral components, distinguished by the presence of many arthropod fecal pellets
• Soil group in Japan

  • Podzolic soils
  • Brown forest soils
  • Red and Yellow soils
  • Black soils
  • Dark-red soils
  • Gley soils
  • Peaty soils
  • Immature soils
• Soil subgroup in Japan

  • Dry podzolic soils
  • Wet-iron podzolic soils
  • Wet-humus podzolic soils
  • Brown forest soils (typical)
  • Dark-brown forest soils
  • Reddish-brown forest soils
  • Yellowish-brown forest soils
  • Surface-gleyed brown forest soils
  • Red soils
  • Yellow soils
  • Surface-gleyed red and yellow soils
  • Black soils (typical)
  • Light-colored black soils
  • Eutric dark-red soils
  • Dystric dark-red soils
  • Volcanogenus dark-red soils
  • Gley
  • Pseudogley
  • Podzolic gley
  • Peat soil
  • Muck soil
  • Peat podzol
  • (Regosols)
  • (Eroded soils)
• Soil group


  An assemblage of the soils having the same sequence and characteristics of diagnostic horizons in soil profiles in common with each other. Conceptually, it nearly corresponds to "Soil type" in West Germany (FRG) and Soviet Union (U.S.S.R.)
• Soil subgroup


  Subdivision of soil group. In addition to typical subgroup which possesses typical characteristics of soil group, soils which are partially influenced by other soil formation process or possess intermediate nature from one soil group to other soil group are distinguished. The soil subgroup corresponds nearly to "Soil subtype" in West Germany and Soviet Union.