Studi Mutu Kayu Jati di Hutan Rakyat Gunungkidul. VII. Ketahanan terhadap Rayap Tanah

Kayu jati telah digunakan untuk bermacam produk karena sifat ketahanan alami di atas rata-rata serta keindahan serat dan warna kayunya. Meski demikian, terdapat variasi untuk sifat ketahanan alami di antara pohon yang tumbuh di tempat tumbuh yang berbeda. Penelitian sebelumnya telah mendeskripsikan sifat kimia kayu jati tumbuh di zona ekologis yang berbeda (Nglipar, Panggang, dan Playen). Sebagai lanjutan, penelitian ini bertujuan menentukan sifat ketahahan alami terhadap rayap pada kayu jati yang tumbuh di hutan rakyat Gunungkidul dan mengeksplorasi faktor yang berkorelasi terhadap sifat tersebut yaitu sifat kimia dan warna kayu. Tujuan lainnya adalah membandingkan data yang diperoleh dengan data kayu yang tumbuh di hutan tanaman Perhutani (Randulatung). Uji pengumpanan tanpa pilihan menggunakan rayap tanah Coptotermes curvignathus terhadap sampel kayu dari tiga tempat tumbuh tersebut. Sifat warna tiap sampel diukur dengan sistem diukur menggunakan sistem CIELAB(L*, a*, b*). Data sifat kimia dan warna kemudian dihubungkan dengan kehilangan berat dan persen hidup rayap setelah 13 hari pengumpanan. Kayu gubal dan teras dari semua pohon menunjukkan aktivitas anti rayap. Perbedaan nyata diamati dalam persen hidup dalam interaksi faktor tempat tumbuh dan arah radial pohon. Sampel dari Panggang menunjukkan ketahanan alami yang lebih tinggi didasarkan persen hidup rayapnya. Selanjutnya, bagian teras dari sampel Playen dan Panggang menunjukkan aktivitas anti rayap yang lebih tinggi dibandingkan sampel dari Randublatung. Pengukuran warna menghasilkan tidak adanya beda nyata untuk kecerahan (L*) antara teras bagian luar dan dalam. Berdasar tempat tumbuhnya, sampel Playen memberikan warna kayu yang paling cerah. Apabila data di bagian teras dan gubal digabungkan, nilai kehilangan berat berhubungan positif dengan nilai kelarutan dalam air panas serta nilai kehilangan berat berhubungan negatif dengan nilai kadar ekstraktif etanol-toluena. Selain itu, nilai pH berkorelasi secara moderat dengan persen hidup rayap selama 8 hari pengamatan. Untuk sifat warna, diamati nilai kemerahan (a*) yang semakin tinggi diiringi oleh kenaikan kehilangan berat di bagian teras. Study of Teakwood Quality from Community Forests in Gunungkidul. VII. Natural Subterranean Termite ResistanceAbstractTeak wood has been used for various uses because of its excellent natural durability as well as beautiful grain and colour of its heartwood. However, variability in natural durability exists between trees of different geographical zones. The previous paper in this series reported on the chemical properties of teak wood from different zones (Nglipar, Panggang, and Playen). In this study, as a continuation, natural termite resistance of teak wood grown in community forests of Gunungkidul and the factors correlating to the termite resistance i.e. chemical and colour properties, were determined. Further, the data obtained here were compared with that of wood samples from Perhutani forest plantation (Randublatung site). No-choice termite feeding test by using a subterranean termite Coptotermes curvignathus were conducted on wood samples taken from three trees of three planted sites. The colour properties of each sample were measured using the CIELAB (L*, a*, b*) system. The chemical and colour characteristics results then were correlated with the mass loss of wood and survival rate of termites after 13 days of feeding. The heartwood and sapwood of all of the trees tested exhibited antitermitic activities. Significant differences were found in survival rate of termites due to interaction of the site and radial position. Samples from Panggang had larger termite resistance judging by its survival rate of termites. Further, the heartwood regions of Panggang and Playen sites exhibited higher antitermite activities than those of Randublatung samples. Measurements of colour showed that no significant differences were found between outer and inner heartwood parts. Samples from Playen showed the lightest on the basis of the sites. In the combined sapwood and heartwood data, mass loss was positively associated with hot-water solubility levels and negatively with ethanol-toluene extractive content. In addition, pH values moderately correlated with survival rate on 8-day observation. With regard to colour properties, it was measured that larger a* values (redness) induced larger mass loss of heartwood.