Saturday, October 10, 2009

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.


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.


Herve said...

Thanks for putting this information on line.

It is difficult to find a good introduction to rainforest and soils in southeast asia / Philippines. Is there any book you would suggest?

Victor B. Asio said...

I appreciate your comments. Thanks. You are right that it is difficult to find a good introduction to rainforest and soils in Southeast Asia/Philippines. The book "Soils of tropical forest ecosystems" edited by Schulte and Ruhiyat (Springer Verlag)is informative although it is for the humid tropics.

Herve said...

Thanks - looks quite interesting.

I spent some time in the Philippines and I look forward to the day I will go back there.

Anonymous said...

Do you have topics on soil and rock formation in NCR espcially in Makati. It's quite interesting to me.. need to study if indeed it is safe to build high building here?

Victor B. Asio said...

We have done pedological studies in different places in the country but not yet inside the Metro Manila area. Thank you for your interest in the subject. For Makati, there is a good information material about its geology which is available in the city website.

For the soils of the area, you may contact the Bureau of Soil and Water Management in Quezon City which has all the soil maps for the entire country.

If you need my help in interpreting soil information that you will be able to collect, please email me.



Jip Leon said...

Hello sir Good Day .Im a civil engineering student. Im currently doing a research about information of Laterite or Lateritic Soils here in Philippines. DO you by any chance have information about it sir? I cant find any article or research about laterites in will be a big help for my thesis .Hoping you can help me .Thank you very much.

Victor B. Asio said...

Hi Jip,

Thanks for dropping by this blog. There are several soils in Leyte and Samar which can be considered as lateritic soils. These soils are very red, clayey, deep and highly weathered. They occur in Matalom, Leyte; Silago, Southern Leyte; Biliran Province; and Salcedo, Eastern Samar. We have a few papers on some of these soils. Please email me your email address so I can send you the said publications.