Karakteristik Lahan Bera Dengan Umur Berbeda dan Pengaruhnya Terhadap Dekomposisi Serasah di Manokwari, Papua Barat
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Balai Besar Penelitian dan Pengembangan Sumberdaya Lahan Pertanian
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Abstrak. Karakteristik umur lahan bera memiliki peran penting dalam pengembalian hara melalui proses dekomposisi. Penelitian dekomposisi serasah dan cadangan karbon pada beberapa umur lahan bera telah dilakukan di Manokwari, Provinsi Papua Barat dari Juli 2020 sampai Januari 2021. Penelitian bertujuan menganalisis proses dekomposisi in situ serasah daun vegetasi lokal pada beberapa umur lahan bera, serta mengukur cadangan karbon dari vegetasi masing-masing lahan bera. Setiap umur lahan bera dipasang sebanyak 18 kantung serasah yang masing-masingnya berisi 20 g serasah daun dari vegetasi lokal lahan bera. Sebanyak tiga kantung serasah diambil setiap bulan dari masing-masing umur lahan bera, kemudian dikeringkan hingga bobot kering konstan. Cadangan karbon biomassa vegetasi dianalisis menggunakan persamaan alometrik berdasarkan diameter pohon setinggi dada (dbh). Hasil penelitian menunjukkan bahwa kehilangan bobot serasah setelah 6 bulan dekomposisi pada lahan bera 5, 10, dan 15 tahun masing-masing mencapai 92,62%; 94,00%; dan 97,12%. Konstanta dekomposisi (tetapan kehilangan bobot serasah) pada lahan bera 5 dan 10 tahun tergolong rendah yakni 0,65 dan 0,94. Lahan bera 15 tahun memiliki konstanta dekomposisi yang tergolong sedang yakni 1,18. Cadangan karbon pada lahan bera 5, 10, dan 15 tahun masing-masing sebesar 7,57; 32,63; dan 141,33 ton/ha. Penurunan rasio C/N setelah 6 bulan dekomposisi pada lahan bera 5, 10, dan 15 tahun masing-masing sebesar 66,67%; 56,25%; dan 39,39%. Dekomposisi serasah pada lahan bera 5 tahun dipengaruhi oleh curah hujan, sedangkan pada lahan bera 15 tahun dipengaruhi oleh kelembapan tanah. Penelitian ini mengindikasikan bahwa umur lahan bera menyebabkan perbedaan komposisi vegetasi, sehingga berpengaruh pada proses dekomposisi dan banyaknya cadangan karbon. Abstract. The characteristics of the fallow land have an important role in the return of nutrients through decomposition process. Research on litter decomposition and carbon stock on different ages of fallow has been carried out in Manokwari, West Papua from July 2020 to January 2021. The aim of the study was to analyze the in situ decomposition process of leaves litterfall from local vegetation at several ages of fallow, and also measure the biomass carbon stock of each fallow land. A total 18 litterbags were installed, each containing 20 g leaves litterfall from the local vegetation of the fallow land. Three litter bags from each age fallow were taken every month and dried to constant mass. Biomass carbon stocks were analyzed using an allometric equation based on the diameter of the trees at breast height (dbh). The results showed that the litter mass loss at fallow 5, 10, and 15 years were 92.62%; 94.00%; and 97.12% respectively after 6-month decomposition. The slowest decay constants (constants of litter mass loss) were 0.65 and 0.94 at fallows 5 and 10 years respectively, whereas at fallow 15 years with k 1.18. Carbon stocks in fallow land of 5, 10, and 15 years were 7.57; 32.63; and 141.33 ton/ha, respectively. The decrease of C/N ratios at fallow 5, 10, and 15 years were 66.67%; 56.25%; and 39.39% respectively after 6 month decomposition. Litter decomposition was influenced by local rainfall on fallow land at 5 years old and soil moisture at 15 years old. This study indicates that the age of fallow lands lead to differences in the composition of vegetation, so that it affects decomposition process and the amount of carbon stocks.
Keywords
Ecology; soil science; micro climate; biology; agriculture (traditional); tropical ecology; forestry, fallow, decomposition, leaves litterfall, C/N ratios, carbon stock, Traditional agriculture; shifting cultivation; land resurces; fallow agriculture; fallow forest; agroforestry