Nutrient sources in four forest watersheds in Japan: the contribution of precipitation, weathering and litter fall

<p>Base cation such as calcium and potassium is important nutrient for tree growth in forest ecosystems.  Major sources of basic cation to forest soil are precipitation, weathering of parent material and litter fall.  Weathering rate of basic cation is estimated from the input from precipitation, runoff from stream and uptake by vegetation.  Nutrient cycling of many Japanese forest ecosystems has been studied but information about the contribution of these sources is limited.  This study compared three nutrient sources in four forest watersheds in Japan.  These are Oyasan (Gunma Pref.), Kamikamo (Kyoto Pref.), Kiryu (Shiga pref.) and Takatori (Kochi Pref.).  We calculated nutrient budget of potassium, calcium and magnesium.  The rate of rock weathering of base cation ranged from 0.22 to 4.37 kmolc ha<sup>-1</sup> yr<sup>-1</sup> and increased in the order of Kamigamo < Kiryu < Oyasan < Takatori.  In potassium cycling, the contribution of litter fall was greater than that of weathering or precipitation.  The runoff of calcium and magnesium from soil was greater in Takatori, where the rate of weathering was high.  Although the rate of weathering varied substantially among forest watersheds, the annual flux of litter fall was relatively constant.  Similar calculation was applied for nitrogen cycling and the　source from soil was treated as that from nitrogen accumulated during the past pedogenesis.  Nitrogen input from the accumulated soil source was 36 % in Oyasan whereas that in other three watersheds was 0%. Oyasan was considered as a nitrogen-saturated forest and the result of the study suggest the ecosystem relies on different nitrogen source.</p>

KEANEKARAGAMAN JENIS IKAN AIR TAWAR DI SUNGAI DONG SANDAR DAN SUNGAI REMPANGI DI KECAMATAN SUNGAI LAUR KABUPATEN KETAPANG

Deforestation will affect changes in the condition of the waters of the protected and secondary forest watersheds that can affect in it biota . Fish have limited ability to choose areas that are safe for their lives, especially the environment that is very supportive for the availability of food sources. The fish population in the Dong Sandar River and Rempangi as well as the diversity of fish species in both rivers is unknown. The problem of this research is how the diversity of fish species in the Dong Sandar River and Rempangi River, Sungai Laur District, Ketapang. Research on the diversity of freshwater fish species in the Dong River between the protection of protected forests and the Rempangi River in the secondary forest of Sungai Laur Subdistrict, Ketapang District, West Kalimantan consisting of 20 stations each of which there are 10 observation stations conducted on May 1 - 21, 2018. The selection of observation stations is selected (purposive sampling) which is based on consideration of the conditions and conditions of the aquatic environment. The results of the research were 884 individuals from 50 species of 18 families with the use of scattered, pukat, seluak, bubu, temilar, sauk , and ambe exploration tools. The most types of fish obtained on the Dong Sandar River and Rempangi River consist of the Cyprinidae family (20 species), Bagridae family (7 species), Siluridae family (4 species). The diversity of fish species in the Dong Sandar River and Rempangi River in Ketapang Regency is relatively moderate (H '<3) with a diversity index (H') of 2.94, if H '<1 means low diversity, if 1 <H' <3 means moderate diversity and if H '> 3 means high species diversity. The dominant index (C) on the Dong Sandar River is 0.09 while in the Rempangi River 0.11, the range of dominant index values is 0 - 1 if the value C = 0 means that there are no types of fish dominating and if C = 1 means there are other types of fish dominating. The highest evenness index (E) is found in the Rempangi River of 0.77 and in the Dong Sandar River 0.76, it can be seen the range of evenness of species index 0-1 if the value E = 0 means low type evenness, and if the value E = 1 means evenness is relatively evenly. The species richness index (R) of the Dong Sandar River has abundant types of fish with a value of 7.26 while in the Rempangi River only 4.40. Evenness on both rivers is 57.53%.Keyword : Diversity, Dong Sandar River, Fish, Rempangi River