PENGARUH RIZOSFER VEGETASI PIONIR TERHADAP KEBERADAAN BAKTERI PENAMBAT NITROGEN NON SIMBIOTIK PASCA ERUPSI GUNUNG MERAPI

RISA ARDHI ANDARI, Ir. Handojo H. Nurjanto M. Agr.Sc

2014 | Skripsi | BUDIDAYA HUTAN

Erupsi Gunung Merapi tahun 2010 mengeluarkan material vulkanik berupa gas, batuan, pasir dan debu. Material ini memiliki unsur hara total yang banyak namun unsur hara yang tersedia sedikit. Selain itu, pada batuan dan mineral tidak terdapat nitrogen akan tetapi nitrogen ini terdapat pada bahan organik atau bahan yang berasal dari bahan organik. Pada kawasan ini hanya vegetasi pionir yang mampu tumbuh. Daerah perakaran tanaman memberi pengaruh terhadap jumlah mikroorganisme tanah termasuk bakteri penambat N non simbiotik. Penelitian ini bertujuan untuk mengetahui pengaruh rizosfer (daerah perakaran) tanaman pionir yaitu dekurens (Acacia decurrens), edelweis (Anaphalis longifolia) dan tanaman paku tanah (Davalia divaricata) terhadap jumlah bakteri penambat N non simbiotik di areal bekas terkena dampak erupsi gunung Merapi. Penelitian ini dilakukan dengan mengambil sampel tanah rizosfer vegetasi pionir yang tumbuh pada area yang terkena erupsi (area yang tertutup pasir, kerikil dan batu) di Kali Adem dan area yang terkena dampak awan panas dan abu vulkanik di Kalitengah Lor. Sebagai perbandingan tanah tanpa vegetasi juga diambil. Jumlah bakteri penambat nitrogen non simbiotik dihitung menggunakan metode plate count dan kemudian koloni bakteri yang tumbuh diisolasi dan diidentifikasi. Kandungan Corganik dan N total pada tanah juga dianalisis dengan menggunakan metode Walkey and Black dan Kjehdahl. Hasil penelitian menunjukan bahwa vegetasi pionir belum memiliki pengaruh terhadap jumlah bakteri penambat nitrogen non simbiotik di masing-masing lokasi setelah tiga tahun terjadi erupsi Gunung Merapi. Untuk kedua lokasi tersebut, jumlah bakteri penambat N non simbiotik di daerah rizosfer relatif sama dengan jumlah bakteri di tanah tanpa vegetasi yaitu sekitar 1-6 x 106 cfu/g dengan rerata R/N rasio sebesar 0,03-0,5. Di daerah yang terkena material vulkanik secara langsung kandungan C-organik tanah rendah dan N total tanah sangat rendah. Sedangkan pada lokasi yang terkena dampak awan panas dan abu vulkanik kandungan C-organik dan N total dalam tanah relatif rendah. Masing-masing jenis isolat bakteri yang ditemukan memiliki karakteristik isolat yang berbeda.

In 2010 Merapi Mountain erupted volcanic materials in the form of gass, rock, sand and dust. These materials have abundant total mineral nutrients but few available nutrients. Besides, nitrogen does not exist in rocks and minerals but it exists in organic matters or their derivates. In the area affected by these materials, only pioneer vegetations can survive. Roots of these vegetations can affect population of soil microorganisms including population of non-symbiotic nitrogen fixing bacteria (NSNFB). The purpose of this research was to study the effect of rhizosphere of pioneer vegetations: bark beatle (A. decurrens), edelweiss (A. longifolia) and fern (D. divaricata) on the number of NSNFB in areas affected by the erupted materials of Merapi Mountain. The research was conducted by collecting samples of rhizospheres of pioneer vegetations growing in area affected severely by the eruption (which was covered by sand, gravels and stones, in Kali Adem) and in area struck by volcanic ash and pyroclastic (in Kali Tengah Lor). As comparison, soil from area without vegetation (bare land) was also collected. Population of NSNFB was counted using a plate count method and the colonies were isolated and identified. Organic carbon and total nitrogen content of the samples were also analysed. The results showed that there was no effect of pioneer vegetation on the population of NSNFB 3 years after Merapi Mountain eruption. The number of NSNFB in the rhizosphere and in the bare land was simillar on the both area averaging from 1 to 6 x 106 cfu/g with the R/N rasio of 0,03-0,5. However in area affected severely by volcanic material, the soil organic-C content of the soil was low and total N was very low, while in the area affected by pyroclastic and volcanic ash, the soil organic-C and total N were low. Bacteria isolated from those area had different characteristics.

Kata Kunci : Merapi Mountain, Pioneer’s plants, Rhizosphere effect, Non symbiotic fixing bacteria