摘要：The organic matter in forest ecosystem that contribute to the organic horizon of soil profile decomposes to CO2. The DOC (dissolved organic carbon) leached to the mineral soil horizons could be decomposed, leached or adsorbed onto mineral surfaces. The effect of soil properties to the DOC dynamic has not been fully understood because of limited data. The objective of this research was to characterize the DOC in Bukit Duabelas National Park and reveal the effect of soil profile position in toposequence and soil properties to the DOC. Six soil profiles were made with different position in toposequence (two soil profiles on each upper, middle, and lower slope). Lysimeters were installed horizontally (in AO, AB and B horizons and in each soil profiles) and connected to a bottle collector that placed on the bottom of soil profile. The soil samples were collected from the each of the soil profiles, at the beginning of the research, while soil solutions were collected periodically. The results showed that independent sample t-test revealed that fluxes of DOC of soil profile on the lower slope were different from that of soil profiles on the upper and middle slopes. The concentration, amount, and fluxes of DOC in soil profile on the lower slope was higher than those of soil profiles on the upper and the middle slopes. Independent sample t-test also revealed that fluxes of DOC of AO horizons were different from those of AB and B horizons. The concentration, amount, and fluxes of DOC of AO horizon was higher than those of AB and B horizons. The result of Pearson correlation showed positive correlations between DOC fluxes with organic-C, total-N, and Cation Exchange Capacity (CEC), but negative correlation with soil bulk density, pH, and Fe dithionite-citrate-bicarbonate (Fed) content. The results suggested that soil profile on the lower slopes on toposequence had higher amount of DOC than that on other soil profiles above it. Horizon AO had higher amount of DOC than that of AB and B horizons. The increase of organic-C, total N and CEC increased DOC. On the other hand the increase of soil bulk density, pH and Fed decreased DOC..
其他摘要：Bahan organik dalam ekosistem hutan yang berkontribusi pada horizon organik dalam profil tanah terdekomposisi menjadi CO2. DOC (karbon organik terlarut) yang tercuci melalui horison tanah mineral dapat didekomposisi, larut sebagai DOC atau diserap ke permukaan mineral. Pengaruh sifat-sifat tanah terhadap dinamika DOC belum sepenuhnya dipahami karena data yang terbatas. Tujuan dari penelitian ini adalah untuk mengkaji pengaruh dari toposekuen terhadap sifat tanah dan DOC. Enam profil tanah dibuat dengan perbedaan posisi lereng dalam toposekuan. Lisimeter dipasang horisontal (di horison AO, AB, dan B di setiap profil tanah) dan dihubungkan dengan botol kolektor yang diletakkan di bawah profil tanah. Sampel tanah dikumpulkan dari setiap profil tanah pada awal penelitian, sedangkan larutan tanah dikumpulkan secara periodik. Hasil penelitian menunjukkan bahwa hasil uji beda rata-rata fluks DOC pada toposekuen menunjukkan bahwa fluks DOC di profil tanah lereng bawah dengan fluks DOC di profil tanah lereng atas dan tengah berbeda. Konsentrasi, jumlah, dan fluks DOC di profil tanah lereng bawah lebih tinggi dibandingkan di profil tanah lereng atas dan lereng tengah. Hasil uji beda rata-rata fluks DOC antar horison tanah menunjukkan fluks DOC di horison AO dengan fluks DOC di horison AB dan B berbeda. Konsentrasi, jumlah, dan fluks DOC di horison AO lebih tinggi dibandingkan di horison AB dan horison B. Hasil korelasi Pearson menunjukkan bahnwa fluks DOC berkorelasi positif dengan C-organik, total-N, dan kapasitas tukar kation (KTK), tetapi berkorelasi negatif dengan bobot isi, pH, dan kandungan Fe dithionite-citrate-bicarbonate (Fed). Penelitian menghasilkan bahwa profil tanah pada lereng yang lebih rendah secara toposekuen memiliki jumlah DOC yang lebih tinggi dibandingkan dengan profil tanah di atasnya. Horison tanah AO memiliki jumlah DOC yang lebih tinggi dibandingkan horison AB dan B. Peningkatan C-organik, N-total, dan KTK meningkatkan jumlah DOC. Di sisi lain peningkatan bobot isi tanah, pH dan Fed menurunkan jumlah DOC.
