Studi Mutu Kayu Jati di Hutan Rakyat Gunungkidul I. Pengukuran Laju Pertumbuhan

Abstract

Kabupaten Gunungkidul menyimpan potensi sebagai penyedia kayu jati sebagai bahan baku industri dari hutan rakyatnya. Penelitian ini bertujuan untuk mengetahui besarnya laju pertumbuhan dan riap pohon jati di hutan rakyat di Kabupaten Gunungkidul serta dihubungkan dengan faktor hujan. Tempat tumbuh yang diamati yaitu Panggang, Playen dan Nglipar. Pengamatan dilakukan selama 3 tahun, yaitu periode I (Oktober 2009-September 2010), periode II (Oktober 2010-September 2011), dan periode III (Oktober 2011-September 2012). Pengukuran diameter pohon dilakukan setiap akhir bulan pada 3 kelas diameter pohon, yaitu besar, menengah dan kecil, dengan ulangan 5 pohon tiap kelasnya. Hasil pengamatan menunjukkan rerata riap diameter tertinggi sebesar 2,21 ± 0,52 cm/tahun diamati di Panggang untuk kelas diameter besar sedangkan nilai terendah sebesar 0,33 ± 0,19 cm/tahun diamati di Nglipar yaitu untuk kelas diameter kecil. Kelas diameter besar memberikan nilai riap yang tertinggi. Pertumbuhan saat periode I hampir semua menunjukkan tertinggi pada semua tempat tumbuh dan kelas diameter. Secara umum, pengukuran riap bulanan menunjukkan adanya pertumbuhan minim dan minus antara Mei-September, puncak pertumbuhan antara Nopember-Februari. Korelasi Pearson antara riap dan curah/hari hujan untuk semua data menunjukkan korelasi sangat nyata antara riap bulanan dengan curah hujan (r = 0,24) atau hari hujan (r = 0,28). Korelasi data berdasarkan faktor tempat tumbuh memperoleh derajat korelasi tertinggi (r = 0,67) yang diamati di Playen khususnya di periode II. Rendahnya derajat korelasi secara umum mengindikasikan beberapa faktor lain perlu diperhitungkan untuk mengetahui kecenderungan pertumbuhan pohon hutan rakyat Gunungkidul.

Katakunci: Tectona grandis, laju pertumbuhan, riap, Gunungkidul, curah hujan

A Study of Teakwood Quality Grown in Community Forests in Gunungkidul, I. Measurement of Growth-Rate

Abstract

Gunungkidul regency has a potentiality to be a producer of teak wood as raw materials for industrial purposes. This study aimed to find out the growth-rate and increment levels of teak trees from community forests in Gunungkidul regency and to correlate it with the rainfall factor. Three observed sites were Panggang, Playen and Nglipar. The observation was conducted during 3 years, i.e. 1st period (October 2009-September 2010), 2nd period (October 2010-September 2011), and 3rd period (October 2011-September 2012). The measurements of diameter were performed on trees in 3 diameter classes (high, middle, small) every in the end of the month by 5 replications of each class. The results were the highest average of diameter increment were 2.21 + 0.52 cm/year observed in Panggang for high diameter class as the lowest level was 0.33 + 0.19 cm/year observed in Nglipar for small diameter class. High diameter class showed the highest increment values. Most of the growth-rate levels of 1st period were the highest in every sites and diameter classes. Generally, the measurement of monthly increment showed the minimum or minus growth between May and September, the highest increment peaks were measured during November – February. Pearson’s correlation for all the data between the rates of increment and rainfall (r = 0.24) or rainy day (r = 0.28) were significant. Data correlation on the basis of gowth-sites showed the highest degree which were observed in Playen, especially in the 2nd period. The weak correlation generally indicates the other factors should be considered to discover the trend of the growth of teak trees in the community forests of Gunungkidul regency.