Rainforestation farming: concept and history (Part I)

by Victor B. Asio, Dept of Soil Science, VSU

a) The concept

Rainforestation or Rainforestation farming is a concept of rehabilitating degraded lands or restoring forests using native forest tree species. It is based on the hypothesis that an ecosystem is more sustainable when its physical structure and species composition are closer to the local rainforest. The Rainforestation farming concept was first presented in seminars by the authors in 1992 and was first published in the peer-reviewed journal Annals of Tropical Research in 1994 (Milan and Margraf, 1994). Two years later a chapter on the Rainforestation concept appeared in the international book Dipterocarp Forest Ecosystems: Towards Sustainable Management by World Scientific (Margraf and Milan, 1996).

 

An idealized sketch of rainforestation about 15 years after its establishment (sketch by R. Dumalag)

The first demonstration sites in Baybay, Leyte were established in 1992. During the early iteration of the concept, spacing and line planting of the trees were considered which were then abandoned by Dr. Margraf because as he always stressed, “nature does not plant trees in straight lines”. Thus, he strongly advocated the random planting of the native trees to simulate a real rainforest. This random planting has thus become a fundamental principle behind the Rainforestation concept. According to the entropy law, the random distribution of tree species should mean more ecosystem stability.

In recent years, the concept has been promoted as a strategy to rehabilitate degraded lands in order to restore the tropical rainforests. In 2004, it was adopted as a national strategy when the Philippine Department of Environment and Natural Resources (DENR) Secretary Elisea G. Gozun through a Memorandum Circular 2004-06 ordered the integration of Rainforestation farming strategy in the development of open areas and denuded forests to promote biodiversity conservation and sustainable development in protected areas and other appropriate forest lands.

 

Photo of the first demonstration site in Mt Pangasugan about 10 years after the establishment

In 2006, the follow-up and monitoring research project funded by GTZ entitled “Rainforestation Farming: Alternative for Biodiversity Conservation and Forest Restoration” (P.P. Milan, M.J. Ceniza, V.B. Asio, S.B.Bulayog, and M. Napiza) was recognized by the Commission on Higher Education (CHED) as the Best Higher Education Institutes (HEI) Research Program. The project provided the needed scientific evidence that the concept was ecologically and economically feasible and now ready for wide-scale dissemination. 

b) Criticisms

From day 1, the concept has met severe and oftentimes unfair criticisms. The earliest criticism that hurt Dr. Margraf was the contention by critics including the ViSCA forestry professors that the originators (Dr. Margraf and Dr. Milan) were neither forest scientists nor vegetation scientists and thus they did not have the expertise to conceptualize a forest restoration strategy. Although valid to some extent, Dr. Margraf was aware of his knowledge limitations so he sought the advice of some of the most brilliant forest science experts in Germany and other countries. 

Another criticism from the agronomists was the use of crops under the “close canopy” demonstration site in that crops require full sunlight to produce yield. As a result, the field staff tried to use fruit trees but this was not very successful as well since the forest trees have the natural tendency to grow tall and cover the fruit trees below. Agroforestry specialists that visited the demonstration sites also consider the planting of crops and fruit trees in between forest trees as “just another variant of agroforestry”. 

Our CHED-PHERNET project site in Inopacan, Leyte, showing the successful 
establishment of the Rainforestation site although at a very high cost

Some forest science experts generally consider the assisted natural regeneration (ANR) as a better strategy to rehabilitate degraded lands because of its greater potential to rehabilitate vast areas of lands at a minimal cost. 

The project site shown in the previous photo in Inopacan, Leyte, appears just a tiny dot in the middle of the large degraded lands (above photo). The other large green patches are actually revegetated through the natural growth of shrubs and trees implying the potential of ANR. 

Lastly, there is a widespread notion that many landowners are only interested to adopt Rainforestation in order to plant hardwood native trees that they could harvest and earn high profits in the future. The fact that a few of the original demonstration sites for the concept established in 1994 have already been harvested by the landowners supports this apprehension. Thus, some people doubt whether this will eventually lead to long-term forest rehabilitation in the country. This should be a big challenge to the Institute of Tropical Ecology and Environmental Management (ITEEM) and other institutions promoting the concept.

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To cite this article: Asio, V.B. 2019. Rainforestation farming: concept and history. http: soil-environment blogspot.com. 

A peer-reviewed article on the history of Rainforestation can be downloaded from the Annals of Tropical Research

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The author (V.B. Asio) has been actively involved in the development and evaluation of the Rainforestation concept from the 1990s until the present. He was a member of the Project Management Core Group of the ViSCA-GTZ Applied Tropical Ecology Project, and later was the first Head of the Terrestrial Ecosystems Division of the Institute of Tropical Ecology. The Core Group members were Dr. M.J.C. Ceniza, Dr. B.B. Dargantes, Dr. R.C. Guarte, Dr. J.M. Quimio, Dr. B.P. Germano & Dr. V.B. Asio.

Ecological quality, macroinvertebrate communities and diversity in rivers in Leyte, Philippines

Researchers from the Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, Belgium, in collaboration with researchers from the Institute of Tropical Ecology and Environmental Management of Visayas State University in Leyte have published scientific evidence of a strong link between ecological quality and macroinvertebrate communities and diversity in rivers in Leyte.

In a paper published this year (2017) in the prestigious journal Ecological Indicators, Vol. 77 and pages 228-238, Marie Anne Eurie Forio and colleagues assessed the macroinvertebrate communities, diversity, and ecological quality of 85 rivers on Leyte island. Specifically, they evaluated the biological (macroinvertebrates), chemical, physical and hydromorphological characteristics. Canonical Correspondence Analysis (CCA) and multivariable linear regression (LRM) were performed to relate the environmental variables and macroinvertebrates.

Eurie Forio and Daphne Radam during the field sampling in Cabintan, Ormoc
(at the central highlands of Leyte) in 2015

The researchers found several taxa of snails, shrimps, dragonflies, beetles, bugs and caddisflies. Although many sites had good to very good ecological quality and high diversity, about 41% had moderate to very bad ecological quality and low diversity. Based on CCA, the researchers concluded that macroinvertebrate communities were associated with velocity, sediment, conductivity and dissolved oxygen. They also observed that sensitive and tolerant taxa were encountered at high and low flow velocities, respectively. Moreover, LRM indicated that macroinvertebrate diversity and ecological quality were associated with physical (turbidity), chemical (chlorophyll), hydromorphological characteristics (bank slope & pool/riffle class), habitat degradation (gravel/sand quarrying, erosion) and the presence of logs and twigs.

Eurie Forio (lead author) and Prof. Peter Goethals (lead scientist)

This ecological study, the first of its kind (i.e. covering 85 rivers of an entire tropical island) to be conducted in the Philippines, supports the use of invertebrates as indicators of certain environmental conditions and the results of this investigation can serve as a basis to set up dedicated experiments to further prove the causality of these discovered relations. 

The study also revealed that organic pollution, as reflected by biological oxygen demand and chemical oxygen demand, was weakly related to invertebrate composition, diversity and ecological quality. This was linked to the low input in most sites and the relatively short rivers which are closely connected to the marine system. Thus, typical midstream and downstream systems were not encountered and the accumulation of these pollutants along the river is less likely. Although the island encounters intensive natural disturbances (e.g. severe typhoons), the taxa (families) were similar to those in other tropical systems and the effects of the environmental conditions were comparable.

The findings of this collaborative research are relevant and valuable in understanding the ecology of tropical islands. They also provide insights into the effects of environmental conditions on stream invertebrates, which aids in protecting and conserving tropical insular systems.

Reference:

Forio, M.A.E., K. Lock, E.D. Radam, M. Bande, V.B. Asio and P.L.M. Goethals (2017). Assessment and analysis of ecological quality, macroinvertebrate communities and diversity in rivers of a multifunctional tropical island. Ecological Indicators 77 (2017) 228–238

Tropical soils: some important aspects of these less understood soils

Tropical regions occur between the Tropic of Cancer and the Tropic of Capricorn. The tropics include approximately 40% of the land surface and is the largest ecozone of the earth. According to Köppen (1931), the tropics are characterized by an annual mean air temperature above 18°C through­out the whole year. The largest climatic variation is introduced by the variability of precipita­tion, reaching from nearly 0 mm in the Saharan and Atacama Desert to 11,700 mm on Mt. Waialeala in Hawaii (Eswaran et al., 1992).

An Afisol (Luvisol) soil derived from mudstone in Eastern Samar, Philippines

According to Uehara and Gillman  (1981), "tropical soils" is a common name used to identify any soil that occurs in the tropics. They noted that like most common names, the term lacks precision, but it is more readily understood by a larger audience than are the scientific names. In contrast, Sanchez (1976) argued against the use of the term "tropical soils" since it does not accurately reflect the soils in the tropics. 

Selected properties of the major tropical soils (Jahn and Asio, 2006)

The name tropical soils is now globally accepted but these soils have remained poorly understood until now. The following are some important aspects of tropical soils (Jahn and Asio , 2006):

1. The tropics,  the world’s largest ecological zone, have a very high potential for plant growth but with soil limitations in vast areas.
2. About one-third of the soils of the world are tropical soils. The most widespread are Ferralsols, Acrisols, Luvisols, Cambisols, and Arenosols.

3. The large proportion of Cambisols (Inceptisols) and Luvisols (Alfisols) in Southeast Asia re­flects clearly the younger age of land surfaces and therefore the short duration of weathering processes.

4. Some soils occur almost exclu­sively within the tropics. About 90% of the Ferralsols (Oxisols), 80% of the Nitisols (Oxisols/Ultisols), and 60% of the Acrisols (Ultisols) are situated in tropical regions.
5. The major soil limitations or soil constraints  are  low cation exchange capacity, low base saturation (low pH, high Al-saturation) and high P retention. They are most widespread in South America, Africa and Southeast Asia (in decreasing order based on area).
6. Physical constraints like high groundwater table, air deficiency, and low soil depth are of lesser significance but govern special requirements for soil management in specific landscapes.
7. Due to severe chemical limitations, proper management of nutrients is the main challenge for effective land-use systems in the tropics.
8. Internal and external fluxes of nutrients are different among soil types and different among tropical landscapes. These have to be considered in ecological land-use systems.
9. To conserve the stock of organic matter in tropical soils (and to increase it in degraded soils), biomass productivity will be a key point for ecological land-use systems.
10. To enable policy-makers as well as land users to establish sustainable and ecological land use systems in the tropics, more precise soil maps and soil information are needed.

References

Eswaran H., J. Kimble, T. Cook & F.H. Beinroth. 1992. Soil diversity in the tropics: Implications for agricultural development. In: Myths and Science of Soils in the Tropics. SSSA Special Publ. No. 29.

Jahn R. and V.B. Asio. 2006. Climate, geology and soils of the tropics with special reference to Southeast Asia and Leyte (Philippines). In: Proc. 11th International Seminar-Workshop on Tropical Ecology, 21-25 Aug 2006, VSU, Baybay City, Leyte, pp: 23-42.

Köppen W. 1931. Grundriss der Klimakunde. W. de Gruyter & Co., Berlin

Sanchez, P.A. 1976. Properties and Management of Soils in the Tropics. Wiley, New York

Uehara G. and G. Gillman. 1981. The Mineralogy, Chemistry, and Physics of Tropical Soils with Variable Charge Clays. Westview  Press, Boulder Colorado.

Available K in highly weathered soils in Leyte and Samar, Philippines

by Ivy L. Capilitan
Department of Agronomy and Soil Science
Visayas State University, Leyte

Soil potassium (K) may be divided into four pools: water-soluble, exchangeable, non-exchangeable, and matrix K (Darunsontaya et al. 2012). With K depletion by plants, water-soluble K and exchangeable K are lowered to minimum levels characteristic of soils. Brady (1974) reported that approximately 90 to 98% of the total soil K is in the non-exchangeable form (although some become available very slowly due to weathering) and is part of the internal structure of clay mineral particles and parent rock material. This form is not available for plant uptake. Feldspar is a general term for a group of aluminosilicate minerals containing Na, Ca or K. Along with mica, feldspar contains most of the K. The plants cannot use the K in this crystalline insoluble form but over long periods of time, these minerals weather (breakdown) and K is released. This process however is too slow to supply the full K needs of field crops yet as soon as these minerals weather, some K moves to the slowly available pool.  

Approximately 1 to 2% K is in the exchangeable form and is lightly bound or held (adsorbed) on the surface of clay particles and organic matter. This form becomes available rapidly and easily to plants when it exchanges with other cations and moves back into the soil solution. K availability also appears to be diminished by allophane through K fixation (van Reeuwijk and Devilliers, 1968 as cited by Poudel and West, 1999). Hopkins and Huner (2009) noted that positively charged K is naturally attracted to a region in the soil with the dominance of negative charges. Both the soil solution and exchangeable K are measured in a soil test as available K. But according to IPI (1977), the concentration of K in the soil solution is a better indicator of K availability than the amount of exchangeable K.

Relationship of exchangeable K and soil solution K with plant uptake of K (IPI, 1977)

Little information is available about K most specifically on its content and availability in highly weathered soils in the Philippines. Thus, we conducted a study that compared the K concentrations and availability in selected highly weathered soils in Leyte and Samar Islands and evaluated the factors affecting them. The soils we used have developed from basalt (Baybay and Biliran site), shale (Matalom site), and ultrabasic rocks (Salcedo site). In terms of the relative degree of weathering, the following sequence was observed: Salcedo soil > Matalom soil > Baybay soil > Biliran soil. The soils are deep, clayey with color ranging from brown to yellowish-brown and red to yellowish-red. They have angular to sub-angular blocky structure with friable and very friable to very firm consistency when moist but generally sticky and plastic when wet.  In terms of chemical characteristics, the soils have acidic pH values ranging from 5.0 to 5.4 (very strong acid). They have a low to medium amounts of organic matter of 2 and 6 %. The total N contents are high in the upper horizon which decreases with depth. All the soils are dominated by 1:1 type of clay minerals particularly kaolinite and halloysite as well as high amounts of iron and aluminum oxides which reflect the highly weathered nature of the soils. 

All the four soils have low exchangeable K and low soil solution K. In general, soil solution K was significantly correlated with soil pH. On the other hand, exchangeable K was generally not correlated with soil pH. The low levels of "available" soil K appear to be related to the highly leached and highly weathered nature of the soils. The study found no clear evidence of the connection between K availability and the type of parent rock of the soils studied. 

References
Darunsontaya T., Suddhaprikarn A., Kheoruenromne I, Prakongkep and Gilkes R. J.. 2012. Geoderma 170: 11-24.
Brady N.C.. 1974. The Nature and Properties of Soils. Macmillan Publishing Co. New York.
Hopkins W.G. and Huner N.P.A.. 2009. Introduction to Plant Physiology. John Wiley and Sons, Inc., New York.
International Potash Institute (IPI). 1977. Potassium dynamics in the soil. CH-3048 Worblaufen-Bern/Switzerland.
Poudel D.D. and West L.T.. 1999.  Soil Sci. Soc. Am. Journal 63:1258–1273.

The geoecology of the limestone and shale areas in Samar, Philippines

Contributed by

Dr. Ian A. Navarrete
Humboldt Fellow
Soil Science of Tropical and Subtropical Ecosystems
Buesgen Institute
University of Göttingen, Germany

Geoecology, a term coined some 41 years ago by the geomorphologist Carl Troll who was at the time professor at the University of Bonn, Germany, is a broad integrative term to the study of forms and functions of terrestrial geoecosystem (Huggett, 1995). It emphasizes the interdependency and/or inter-relationships of the ecological biosphere with landscape and hence sometimes equated with landscape ecology. For example, the movement and distribution of solutes across soil landscapes are influenced by the geomorphic position in the soil within the landscape thus influencing soil genesis (Sommer and Schlichting, 1997) and vegetation development (Huggett, 1975). 

Fig 1. Relation of primary forest and grasslands of Samar

During our fieldwork at the Samar Island Natural Park (along the Paranas-Taft road at about 300 m above sea level) in Feb 2012, we observed two typical grassland ecosystems occurring near or far from the primary forests (Fig 1A).

The first type is the grassland that occurs in the lower residual limestone soil or at the margin of the primary forest. The soils in such grassland are younger as indicated by poor soil profile development. The dominant grass is Paspalum conjugatum which in many areas occur in association with Chromolaena odorata. The second type is the grassland in the degraded rolling and hilly areas usually away from primary forests. The soils in these areas are different from the soils in the primary forest on the upper slopes in that they are mature, reddish, and deep (Fig 1B). They appear to have formed from the limestone residue or from the shale (underlying the limestone) that is widely exposed in the rolling areas. The dominant grass is Imperata cylindrica. 

Fig 2. Primary forest soil in Samar

The soils of the primary forest (limestone forest) on the upper and usually steep slopes are generally very thin and are underlain by consolidated limestone rocks (Fig 2). The presence of nutrient-enriched weathering pockets (where deposition of nutrient and decomposition of organic matter take place) of the limestone parent material, and the high annual rainfall explain the lush growth of the forest vegetation. It also partly explains the high tree species diversity of the forest.

(Members of the team: V.B. Asio, Ariel Bolledo, Mark Moreno, Pearl Carnice, Richel Lupos, Forester Elpidio Cabahit Jr. from the Samar Island Natural Park, and myself)

References

Huggett RJ (1975). Soil landscape systems: a model of soil genesis. Geoderma 13: 1-22.
Huggett RJ (1995). Geoecology: An Evolutionary Approach. Routledge, London.
Sommer M, Schlichting E (1997). Archetypes of catenas in respect to matter-a concept for
structuring and grouping catenas. Geoderma 76:1-33.

Melanterite Soil: A green soil in the highlands of Samar

A soil at the heart of Samar, the third largest island of the Philippine archipelago, and along the Paranas-Taft road at about 300 m above sea level (within the Samar Island Natural Park) easily catches the attention of travellers. This is because it is unique: it is green in color. As far as I know, no soil with such color has yet been reported in the scientific literature.

The melanterite soil near the Bagacay mining area in Samar island

The dominant green color is probably due to the abundance of the secondary mineral called melanterite, a hydrated iron sulphate mineral (FeSO4.7H2O) formed from the decomposition of pyrite or other iron minerals due to the action of surface waters. Melanterite is known to be stable only under highly acidic condition. It is commonly found in mines as a post-mining formation on mine walls, in sulfidic sedimentary and metamorphic rocks as well as in coal and lignite deposits. It indicates the possible presence of sulfuric acid and should not be handled with bare hands or inhaled (www.mindat.org).

Photo of the site along the highway in Central Samar where the melanterite soil occurs

The green soil we have examined in Samar developed from mudstone interlayered with coal deposit. The site is not far from an area which was mined for coal and pyrite and thus it appears to satisfy the environmental conditions favorable for melanterite occurrence.

We had the chance to examine the soil during our fieldwork in Samar on 2-3 Feb 2012 as part of my graduate course in pedology (Soil Science 212). We plan to conduct a detailed pedological and geochemical study on this soil in the near future. For easy reference, I suggest to call it “Samar melanterite soil”.

Recent updates: In the book "Assessment, Restoration and Reclamation of Mining Influenced Soils" edited by Prof. Jaume Bech (University of Barcelona) and his colleagues and published by Academic Press, London, in 2017,  the occurrence of melanterite mineral in some mining-affected soils from Spain and Portugal has been mentioned. This seems to confirm our observation about the green soil in Samar in 2012.

(Members of the team: Ariel Bolledo, Mark Moreno, Pearl Carnice, Richel Lupos, Dr. Ian Navarrete (Humboldt Research Fellow), Forester Elpidio Cabahit Jr. from the Samar Island Natural Park, and myself (VBA)).

Soil excursion to Southern Leyte, Philippines with Prof. R Jahn

On 09 April 2010, we organized a soil excursion to Southern Leyte for selected graduate students pursuing MSc degree in Soil Science at the Department of Agronomy and Soil Science of Visayas State University in Baybay, Leyte. The main objective of the activity was to observe the important soils of the province.

Prof. Dr. Reinhold Jahn of Martin Luther University (Germany), former Chairman of the Soil Geography Commission of the International Union of Soil Sciences (IUSS), served as the resource person. The participants included Grace Enojada, Marilou Sarong, Katrina Piamonte, Deejay Maranguit, Glenn Largo, and Raffy Rodrigo.

The group first focused on the young soils in the alluvial plains which are generally used for lowland rice production. Prof. Jahn discussed the important features of paddy (rice) soils particularly gleying, mottling, and the occurrence of plow pan.

During his recent fieldwork in the Banaue rice terraces in northern Luzon, Prof. Jahn noted that plow pan is generally absent in the rice terraces since puddling is not part of the normal cultural management practices there. Puddling is the process of destroying the structure of rice soil by cultivating it when it is wet in order to homogenize the soil and to produce a watertight soil paste to hold water on the soil surface.

In the mountainous portion of Southern Leyte, highly weathered soils (Ultisols) that developed from basalt and other igneous rocks are widespread. The group examined a Ultisol soil profile that was very deep and heavy clay, and which showed the occurrence of mottles and exfoliation weathering of rock in the lower portion of the profile. Ultisols are acidic, clayey, and have generally low nutrient status. They are the most widespread soils in the Philippines.

The group also found a very beautiful soil profile of a Ultisol near the town of Silago. It formed from two parent materials (bisequm) and clearly showed lithologic discontinuity (i.e. the heterogeneity of the parent rock material).

Soil degradation in the Philippines

Soil degradation is a severe global problem of modern times. About six (6) million hectares of agricultural land worldwide become unproductive every year due to the various soil degradation processes. The problem is much more serious in tropical than in temperate areas since tropical soils are generally more prone to degradation because of the nature of their properties (e.g. they are more weathered) and the prevalent climatic conditions. Countries in Asia and Africa that depend upon agriculture as the engine of economic growth are believed to suffer the greatest impact of soil degradation. In the Philippines, soil degradation is one of the most serious ecological problems today. The National Action Plan (NAP) for 2004 to 2010 identified soil degradation as a major threat to food security in the country. NAP reported that about 5.2 million hectares are seriously degraded resulting in a 30 to 50% reduction in soil productivity.

A degraded upland in Leyte

Soil degradation is defined as the process which lowers the current or future capacity of the soil to produce goods or services. It implies a long-term decline in soil productivity and its environment-moderating capacity. The concept of soil degradation was first used by Kostychiev and Korchinski in 1888 to describe a natural soil change. Since natural degradation is slow, the present concept of soil degradation according to the Global Assessment of Soil Degradation (GLASOD) focuses on a human-induced process. Soil degradation occurs because of drastic changes or disruption in the normal processes of soil formation due to human activities.

A degraded upland covered with Imperata (cogon) grass in Samar

In a review paper on the problem of soil degradation in the Philippines published in the Annals of Tropical Research vol. 31, we (Asio et al. 2009) revealed that soil erosion is the most widespread process of soil degradation and is also the most studied in the country. Other important but less studied soil degradation processes include loss of nutrients and organic matter, salinization, acidification, pollution, compaction, and subsidence. 

A degraded upland in Bukidnon

Studies reviewed have shown that the widespread degraded upland soils possess chemical and physical constraints for crop growth like acidic or calcareous pH, low organic matter and nutrient contents, shallow solum, presence of toxic substances, and compaction. The major factors that cause soil degradation include deforestation, overgrazing, agricultural practices, industrial activities, mining, and waste disposal. Deforestation is the main cause of soil degradation in Asia and South America while overgrazing is the main factor in the dryland areas of Australia, Africa, Europe, and Asia.

The typical degraded land in Cagayan Valley due to deforestation & overgrazing 

There is a need for more data on the physical and socio-economic characteristics of degraded lands to aid in the formulation of appropriate soil management strategies to support biodiesel production in these unproductive lands which are now being promoted by the Philippine government. Also, there is the danger that the use of the degraded lands for intensive and long-term biodiesel production without the appropriate soil management would cause further soil deterioration and thus aggravate the ecological problems that are now occurring.

Reference

Asio VB, Jahn R, Perez FO, Navarrete IA, and Abit SM Jr. 2009. A review of soil degradation in the Philippines. Annals of Tropical Research 31: 69-94

Note: All photos are owned by the author.

Characteristics and formation of rain forest soils from Quaternary basalt in Leyte, Philippines

The classical view about soils of tropical rain forest ecosystems is that these soils are old, acidic, and infertile. It is now widely acknowledged that this view which has greatly influenced research and management of the fragile rain forest ecosystem during the last several decades is largely a misconception. Although highly weathered soils (Oxisols or Ferralsols) are the most dominant soils in the humid tropics, tropical soils range from relatively young fertile soils (e.g. Inceptisols) to the highly weathered infertile soils (e..g. Oxisols). The extent of highly weathered soils is less in geologically young areas like in much of SE Asia.

More detailed investigations of rain forest soils are vital for the sustainable management of this threatened ecosystems. These could also lead to a better understanding of the response of rain forests to climate change.

Navarrete et al. (2009) recently conducted a study to evaluate the physical, chemical and mineralogical characterisitics of rain forest soils in Leyte, Philippines. Some of the important findings of that study include:

1) Soils along the catena studied showed minimal variations in their morphological, physical and chemical properties. This has important ecological implications as it tends to not support the idea that high soil spatial variability at short distances in rain forest ecosystems is a major factor for its high biodiversity.

2) The dominant soil-forming processes that produced the soils in the study area are weathering, loss of bases and acidification, desilification, ferrugination, clay formation and translocation, and structure formation. The loss of bases and acidification due to rapid leaching are shown by the low base saturation, very low exchangeable bases, acidic pH, and the low contents of total Ca, Na, Mg, and K. The degree of desilification is almost unifrom in all soils and may have reached 12-19% of that found in the parent material. Ferrugination is shown by the increased loss of bases, halloysitic and kaolinitic mineralogy, high contents of iron oxides and low base saturation. Clay formation and translocation are reflected by the high clay contents particularly in the middle part of the soil profile. Soil structure formation is exhibited by the good soil physical condition.

3) The nature of the basalt parent rock and the climatic condition prevailing in the area as well as its relief appear to be the dominant factors affecting the development of the soils.

Reference

Navarrete IA, K Tsutsuki, VB Asio, R Kondo. 2009. Characteristics and formation of rain forest soils derived from late Quaternary basaltic rocks in Leyte, Philippines. Environmental Geology 58: 1257-1268.