PERAN REVEGETASI TERHADAP RESTORASI TANAH PADA LAHAN REHABILITASI TAMBANG BATUBARA DI DAERAH TROPIKA (The Role of Revegetation on the Soil Restoration in Rehabilitation Areas of Tropical Coal Mining)

ABSTRAK Pertambangan batubara terbuka menyebabkan degradasi lahan, sehingga perlu upaya rehabilitasi lahan melalui program revegetasi. Penelitian dilakukan di areal PT. Berau Coal  pada site Binungan, Lati dan Sambarata, Kabupaten Berau, Kalimantan Timur, Indonesia. Penelitian menggunakan rancangan acak lengkap ber-blok dengan umur revegetasi sebagai perlakuan, tiga kali ulangan dan tiga site sebagai blok. Pemilihan lokasi menggunakan metode purposif sampling yaitu pengambilan sampel yang didasarkan pada pertimbangan pada umur pengolahan lahan revegetasi, meliputi S1 : area hutan sebelum ditambang (rona awal), S2 : revegetasi awal, umur tanaman  < 1 tahun, S3 : revegetasi menengah, umur tanaman 3 tahun, dan S4: revegetasi lanjut, umur tanaman  > 5 tahun. Pengambilan sampel tanah pada  kedalaman 0–20 dan 20-40 cm pada setiap perlakuan di ketiga lokasi, selanjutnya dianalisis sifat fisik dan kimianya. Tanah Typic Hapludult pada lahan hutan sebelum ditambang batubara secara terbuka (S1,  rona awal) mempunyai kadar C-organik (1,87 %), N-total (0,14 %), P-tersedia (31,40 ppm), K-tertukar (0,11 me/100g), pH (3,98), KTK (10,72 me/100g) dan kejenuhan basa (17 %). Penambangan terbuka batubara telah menyebabkan lapisan bawah dan  permukaan tanah menjadi terbongkar dan terjadi penurunan kualitas tanah yang sangat drastis. Penimbunan lahan dengan media tanah permukaan sebelumnya, telah cukup  mampu memperbaiki sifat-sifat tanah tertambang namun belum sesuai sebagai media pertumbuhan, serta sangat rentan terhadap degradasi lahan lebih lanjut. Revegetasi menggunakan tanaman pionir, cepat tumbuh dan adaptif seperti Sengon, Akasia, Sungkai, Melina, Angsana, Jarak serta Legume Cover Crop (LCC) pada area bekas tambang  batubara memberikan pengaruh yang  nyata terhadap peningkatan kandungan C-organik, N-total dan  pH tanah. Revegetasi menggunakan spesies cepat tumbuh setelah berumur 5 tahun telah mengembalikan bahkan memperbaiki sifat kimia tanah dibanding dengan kondisi pada hutan tropika basah sebelum dilakukan penambangan terbuka.   ABSTRACT Open coal mining causes land degradation, so they need land rehabilitation through re-vegetation programs. The study was conducted in the PT Berau Coal area of Binungan, Lati and Sambarata site, Berau regency, East Kalimantan, Indonesia. Research using a randomized completely block design with the age of re-vegetation as treatments, three replication and three sites as blocks. Sampling unit was selected using a purposive sampling method that is based on the re-vegetation management, including: (i) S1: forest area without mining activities (baseline), (ii) S2: initial re-vegetation, plant age < 1 year, (iii) S3 : medium re-vegetation, plant age 3 years, (iv) further re-vegetation, plant age > 5 years. Soil sample was collected from 0-20 and 20-40 cm soil depth in each treatment at three locations, then analyzed for soil  physic and chemistry. Soil of Typic Hapludult on forest land without coal mining has a C-organic (1.87 %), N-total (0.14 %), available-P (31.40 ppm), exchangeable-K (0.11 me/100g), pH (3.98), CEC (10.72 me/100g) and base saturation (17 %). Opened coal mining has led the soil layer becomes exposed and a declining in soil quality drastically. Land closure with the top soil media has been quite able to improve soil properties in rehabilitation areas, but not suitable as media for plant growth, and highly susceptible for further degradation. Land rehabilitation and re-vegetation with fast growing and adaptive pioneer plants such as: Sengon, Acacia, Sungkai, Melina, Angsana, Jarak and Legume Cover Crop (LCC) in the rehabilitation area of coal mining, gave significant effect on the increasing of  C-organic, N-total and soil pH. Re-vegetation with fast growing species after 5-year-old has returned the soil chemical properties that are equivalent or even better than thier condition in moist tropical forests without open coal mining.