Keanekaragaman Mikrob Tanah Gambut di Bawah Hutan dan di Bawah Perkebunan Sawit di Provinsi Jambi

Abstract

Abstrak. Drainase lahan gambut diperkirakan akan mempengaruhi populasi dan keanekaragaman hayati di tanah gambut. Tujuan dari penelitian ini adalah untuk mengevaluasi pengaruh drainase dan tutupan lahan gambut di Tanjung Jabung Timur, Provinsi Jambi terhadap populasi dan keanekaragaman mikroba tanah gambut. Sampel tanah gambut diambil dari tiga lokasi yang berbeda yaitu: (A) perkebunan sawit dengan kedalaman saluran drainase 50-70 cm, (B) perkebunan sawit dengan kedalaman saluran drainase 20-50 cm, dan (C) hutan gambut. Total populasi mikroba dihitung menggunakan metode Total Plate Count dan media selektif pertumbuhan bakteri, fungi, dan aktinomicetes. Mikroba yang memperlihatkan tampilan fisiologis yang berbeda masing-masing dihitung populasinya, lalu dilakukan identifikasi menggunakan Biolog Identification Kit. Hasil penelitian menunjukkan bahwa total populasi dengan keragaman mikroba tertinggi terdapat pada contoh tanah gambut yang telah didrainase pada kedalaman tanah 0-20 cm. Bakteri penambat nitrogen Azotobacter hanya terdeteksi pada tanah gambut lapisan tanah 0-20 cm di lokasi A. Mikroba pelarut P dengan total populasi 2,00 x 104 - 4,00 x 104 cfu g-1 terdapat di tiga lokasi, tetapi hanya ditemukan pada kedalaman 0-20 cm. Pada tanah gambut di lokasi A di kedalaman 0-20 cm dijumpai delapan jenis mikroba, yaitu: Azotobacter sp., Bacillus luciferensis, B. salarius, B. soli, Cupriavidus paucalus, Mycobacterium cubhense, Paenibacillus illinoisensis, dan P. wynnii. Sedangkan pada kedalaman 20-50 cm diperoleh spesies bakteri yang lebih sedikit, yakni Bacillus kribbensis, Bacillus panaciterrae, Chryseobacterium balustinum, dan Paenibacillus peoriae. Pada lokasi B, jenis mikroba yang dijumpai lebih sedikit dan didominasi oleh enam spesies bakteri (Bacillus salarius, B. soli, Cupriavidus paucalus, Nocardia jiangxiensis, Paenibacillus wynnii, dan Pseudomonas aeruginosa), sedangkan di lokasi C didominasi oleh hanya lima spesies mikroba (Bacillus vallismortis, Nocardia jiangxiensi, Paenibacillus glycaniliticus, P. peoriae, dan Rhodococcus equi). Tampaknya drainase dan pemupukan pada lahan gambut di perkebunan sawit mendorong pertumbuhan mikroba.

Abstract. Drainage of peat is expected to affect belowground biodiversity. The purpose of this research was to evaluate the impact of drainage and peatlands cover in Tanjung Jabung Timur, Jambi Province on the soil microbial population and the soil microbial diversity. Peat soil samples were taken from three locations, namely (A) oil palm plantation with 50-70 cm drainage channel, (B) oil palm plantation with 20-50 cm drainage channel, and (C) logged-over forest. The total microbial population was calculated using the Total Plate Count method and the selective growth medium of bacteria, fungi and actinomycetes. The population of microbes exhibiting different physiological features were counted and then identified using the Biolog Identification Kit. The results showed that the highest total microbial population and diversity were found in drained peat at 0-20 cm soil depth. Nitrogen fixing bacteria, Azotobacter, was found only in 0-20 cm layer of the A location. P-solubilizing microbes were found only in the 0-20 cm layer peat with the total population ranged from 2.00 x 104 to 4.00 x 104 cfu g-1 soil in the three sites. In the 0-20 cm peat layer of location A, we found eight kinds of bacteria, namely: Azotobacter sp., Bacillus luciferensis, B. salarius, B. soli, Cupriavidus paucalus, Mycobacterium cubhense, Paenibacillus illinoisensis, and P. wynnii. In peat of location B, the total population of microbes was fewer, consecutively dominated by six species of bacteria, namely Bacillus salarius, B. soli, Cupriavidus paucalus, Nocardia jiangxiensis, Paenibacillus wynnii, and Pseudomonas aeruginosa, while in peat of location C was dominated by five species of bacteria (Bacillus vallismortis, Nocardia jiangxiensi, Paenibacillus glycaniliticus, P. peoriae, and Rhodococcus equi). It seems that drainage and fertilization in drained peatlands under oil palm plantations encouraged microbial growth.