SIFAT KEAWETAN ALAMI, PENCUACAAN (WEATHERING), DAN EFEKTIFITAS BAHAN PENGAWET BORON PADA KAYU JATI HUTAN RAKYAT
Yus Andhini Bhekti Pertiwi, Dr. Ir. Sri Nugroho Marsoem, M.Agr. Sc.
2014 | Tesis | S2 Ilmu KehutananPemanfaatan kayu jati hutan rakyat saat ini semakin luas. Akan tetapi, lokasi penggunaan kayu perlu diperhatikan karena adanya berbagi macam ancaman organisme perusak kayu sehingga akan memperpendek umur pakainya. Selama ini muncul anggapan bahwa kayu jati hutan rakyat memiliki kualitas yang rendah dan belum jelas sifat keawetan alaminya karena pada umumnya ditebang pada umur yang masih muda. Penelitian mengenai keawetan alami kayu jati hutan rakyat di laboratorium sudah pernah dilaksanakan tetapi informasi keawetannya di lapangan masih terbatas. Penelitian ini dibagi dalam 3 sub bab, yaitu keawetan alami kayu jati hutan rakyat, pencuacaan kayu, dan usaha peningkatan keawetan kayu jati hutan rakyat. Untuk mengetahui keawetan alami kayu jati hutan rakyat maka metode penelitian yang digunakan adalah uji graveyard (uji kubur) selama 6 bulan berdasarkan Protocols for Assessement of Wood Preservatives Australia (2007). Pengumpanan contoh uji pencuacaan alami mengacu pada Metode Johnson dan perubahan warna diamati setiap bulan dengan menggunakan sistem CIA L*a*b*. Sedangkan untuk meningkatkan keawetan kayu gubal digunakan metode pengawetan dengan proses bethel kemudian dilakukan uji kubur. Penelitian ini menggunakan rancangan acak lengkap yang disusuan secara faktorial. Data penelitian diolah menggunakan analisis varians dan dilanjutkan dengan uji Tukey. Keawetan alami kayu jati hutan rakyat dipengaruhi oleh kedudukan radial (teras dan gubal) serta kondisi lingkungan dimana kayu itu digunakan, namun tidak dipengaruhi oleh bagian aksial. Dalam waktu 1 bulan, kayu jati hutan rakyat baik teras maupun gubal sudah terserang oleh rayap tanah. Meskipun demikian, kayu teras masih termasuk kelas awet II sedangkan kayu gubal termasuk kelas III. Setelah 6 bulan pencuacaan, perubahan warna (ΔEab) permukaan kayu pada kayu teras dan gubal sebesar 15,60 dan 19,34 sehingga menjadi keabu-abuan dan kusam karena photodegradasi lignin dan menurunkan L*, a*, dan b* pada kayu teras dan gubal yaitu 50,54 dan 49,45; 6,13 dan 5,54; 4,85 dan 5,32. Perubahan warna (ΔEab) sangat nyata pada bulan kedua setelah pencuacaan akan tetapi perubahan warna yang terjadi tidak signifikan setelah bulan ketiga sampai bulan keenam, dan pada akhirnya kayu teras dan gubal memiliki warna yang sama. Konsentrasi 7% senyawa boron sudah cukup melindungi kayu gubal dari serangan rayap tanah.
Nowadays, teak wood including young teak from community forest has been getting more widely utilized. Public opinion showed that teak wood from community forests possess low quality and less durable because of its early harvesting. Study on the natural durability of young teak on the various fields is necessary. However, there is a lack of information on the natural durability of teak wood from community forest to prove the public opinion. This study was divided into 3 parts, i.e. the natural durability, weathering, and preservation effort of teak wood from community forest. By considering the position of wood on the axial direction of tree and sapwood-heartwood, the natural durability of teak wood was determined by graveyard test for 6 months on two locations. The weathering test of teak wood as mentioned on previous part was conducting according to Johnson Method for 6 months by observing color and chemical changing based on CIA L*a*b* system and Fourier Transfer Infrared Spectroscopy (FTIR) analysis, respectively. Meanwhile, in order to improve the durability, sapwood was treated with various boron concentrations by a bethel process and then followed by graveyard test for 6 months. This study used completely randomized design. Data were analyzed by variance analysis and followed by Tukey’s test. The durability of teak wood from community forest was influenced by heartwood-sapwood and the environmental conditions of graveyard test locations where the wood applied. However, the teak wood durability was not influenced by the position of wood on the axial direction. Teak wood from the bottom and upper part of log showed no different in the natural durability. Both heartwood and sapwood were attacked by subterranean termites in a month. Teak heartwood from community forest could be classified in II durability class and sapwood was III-IV durability class. Both heartwood and sapwood surfaces showed discoloration with ΔEab 15.6 and 19.34, respectively, after weathering. Wood surface experienced discoloration on both sapwood and heartwood, the value were 15.60 and 19.34 respectively. After all, the color of teak wood become grey and dull due to the photodegradation of lignin according to FTIR analysis. The weathering also decreased the lightness (L*), redness (a*), and yellowness (b*) of heartwood and sapwood, 50.54 and 49.45; 6.13 and 5.54; 4.85 and 5.32, respectively. In the context of preservation effort, the study showed that 7% of boron concentration of preservative solution was sufficient to protect sapwood from termites attack.
Kata Kunci : jati hutan rakyat, keawetan alami, uji kubur, pencuacaan
