Assessment of tree resources in the home gardens of Sri Lanka

Galle and Matara are adjoining districts and were administered as one forest division at the time of the assessment. The average tree density in the dry zone is around 125 trees per hectare. More than 260 trees per hectare are found in the wet zone. Tree density in Kandy is unusually low despite the fact that the well-known Kandyan Forest Gardens are found in this area. Polonnaruwa is the other district with very low density. These differences cannot be explained with the available data.

Most home garden tree species are well distributed over the country and are found in all three climatic zones (Table 13). Geographical distribution and the tree density of the most common home garden species are shown in Appendix 2.

Table 13. Distribution of species within the study area

Species name		Category	No. of DS divisions where species are present	Distribution as a % of total area
Local	Botanical	Category	No. of DS divisions where species are present	Distribution as a % of total area

Mango	Mangifera indica	TF	241	92.3
Jak	Artocarpus heterophyllus	TF	240	92.0
Coconut	Cocos nucifera	TF	232	88.9
Orange	Citrus cinensis	F	227	87.0
Guava	Psidium guajva	F	220	84.3
Teak	Tectona grandis	T	217	83.1
Lime	Citrus aurantifolia	F	214	82.0
Margosa	Azadirachta indica	T	213	81.6
Cashew	Anacardium occidentale	TF	211	80.8
Tamarind	Tamarindus indica	TF	211	80.8
Arecanut	Areca catechu	F	188	72.0
Del	Artocarpus altilis	TF	171	65.5
Butter fruit	Persea americana	F	170	65.1
Lunumidella	Melia dubia	T	168	64.4
Mahogany	Swietenia macrophylla	T	165	63.2
Anoda	Anona cherimolia	F	164	62.8
Jambu	Syzygium malaccensis	F	163	62.5
Alstonia	Alstonia macrophylla	T	159	60.9
Milla	Vitex altissima	T	156	59.8
Kitul	Caryota urens	TF	155	59.4
Veralu	Elaeocarpus serratus	F	148	56.7
Rambutan	Nephelium lappaceum	TF	142	54.4
Ambarella	Spondias dulcis	F	130	49.8
Suriyamara	Albizia odoratissima	T	120	46.0
Eucalyptus	Eucalyptus spp.	T	114	43.7
Domba	Calophyllum inophyllum	T	111	42.5
Bamboo	Bambusa vulgaris	T	104	39.8
Kottamba	Terminalia catappa	T	104	39.8
Halmilla	Berrya cordifolia	T	101	38.7
Albizzia_1	Albizia molucana	T	98	37.5
Satin	Chloroxylon swietenia	T	98	37.5
Nedun	Pericopsis mooniana	T	95	36.4
Kumbuk	Terminalia arjuna	T	93	35.6
Pihimbiya	Filicium decipiens	T	88	33.7
Beli	Aegle marmelos	F	87	33.3
Wood apple	Limonia acidissima	TF	85	32.6
Kon	Schleichera oleosa	T	83	31.8
Mee	Madhuca longifolia	T	81	31.0
Rubber	Hevea brasiliensis	T	81	31.0
Hora	Dipterocarpus zeylanicus	T	79	30.3
Palu	Manilkara hexandra	T	77	29.5
Delum	Punica granatum	F	76	29.1
Murunga	Moringa oleifera	F	76	29.1
Palmairah	Borrasus flabellifer	TF	69	26.4
Ketakela	Bridelia retusa	T	68	26.1
Helamba	Mitragyma parvifolia	T	63	24.1
Kolon	Adina cordifolia	T	60	23.0
Gansuriya	Thespesia populnea	T	59	22.6
Ebony	Diospyros ebenum	T	58	22.2
Godapara	Dillenia retusa	T	58	22.2
Ipil Ipil	Leucaena leucocephala	T	54	20.7
Damba	Syzygium assimile	T	51	19.5
Kahata	Careya arborea	T	51	19.5
Ehela	Cassia fistula	T	50	19.2
Weera	Drypetes sepiaria	T	49	18.8
Daminiya	Grewia damine	T	47	18.0
Nelli	Phyllanthus emblica	F	45	17.2
Bulu	Terminalia bellirica	T	41	15.7
Hik	Lannea coromandelica	T	38	14.6
Hulanhik	Chukrasia tabularis	T	38	14.6
Sabukku	Grevillea robusta	T	36	13.8
Wewarana	Alseodaphne semicarpifolia	T	36	13.8
Kaduru	Thevetia peruviana	T	34	13.0
Toona	Toona sinensis	T	34	13.0
Welang	Pterospermum suberifolium	T	32	12.3
Mora	Dimocarpus longana	TF	23	8.8
Gammalu	Pterocarpus marsupium	T	18	6.9
Kenda	Macaranga peltata	T	18	6.9
Etamba	Mangifera zeylanica	TF	16	6.1
Gal siyambala	Dialium ovoideum	TF	13	5.0
Albizzia_2	Albizia lebbeck	T	12	4.6
Cocoa	Theobroma cacao	F	12	4.6
Gliricidia	Gliricidia sepium L.	T	12	4.6
Aralu	Terminalia chebula	TF	10	3.8
Gini sapu	Michelia champaca	T	9	3.4
Coffee	Coffea arabica	F	8	3.1

The 11 most valuable timber species can be found in more than 60 percent of the study area. Wood is used for all kinds of construction purposes, furniture and handicrafts. Table 14 shows the market prices of logs and timber classes of the most valuable home garden tree species. These are the prevailing log prices and timber classes of the State Timber Corporation (STC) and tend to change with market demand. Open market prices are somewhat higher than the STC prices.

Table 14. Most valuable timber species found in home gardens

Species name		Origin	Timber class	Log price/m³ (Rs.)
*Local*	*Botanical*	Origin	Timber class	Log price/m³ (Rs.)
Teak	Tectona grandis	Planted	Super luxury	23 040< /span>
Nedun	Pericopsis mooniana	Naturally grown/planted	Super luxury	23 040
Jak	Artocarpus heterophyllus	Planted	Luxury	15 120
Mahogany	Swietenia macrophylla	Planted	Luxury	14 760
Satin	Chloroxylon swietenia	Naturally grown	Luxury	15 180
Halmilla	Berrya cordifolia	Naturally grown/planted	Luxury	15 180
Milla	Vitex altissima	Naturally grown	Luxury	15 180
Eucalyptus	Eucalyptus spp.	Planted	Special & 2	5 700
Margosa	Azadirachta indica	Naturally grown/planted	Special	14 220
Kumbuk	Terminalia arjuna	Naturally grown/planted	Special	11 340
Palu	Manilkara hexandra	Naturally grown	Special	14 220
Welang	Pterospermum suberifolium	Naturally grown	Special	14 220
Kolon	Adina cordifolia	Naturally grown	Special	14 220
Suriyamara	Albizia odoratissima	Naturally grown	Special	14 220
Hora	Dipterocarpus zeylanicus	Naturally grown/planted	1	7 740
Ketakela	Bridelia retusa	Naturally grown	1	7 740
Kon	Schleichera oleosa	Naturally grown	1	7 740
Damba	Syzygium assimile	Naturally grown	1	7 740
Helamba	Mitragyma parvifolia	Naturally grown	1	7 740
Alstonia	Alstonia macrophylla	Planted	2	5 700
Toona	Toona sinensis	Naturally grown/planted	2	5 700
Coconut	Cocos nucifera	Planted	3	3 216
Rubber	Hevea brasiliensis	Planted	3	3 216
Mango	Mangifera indica	Planted	3	1 620
Albizzia_1	Albizia molucana	Planted	3	1 620
Lunumidella	Melia dubia	Naturally grown/planted	3	3 180
Sabukku	Grevillea robusta	Naturally grown/planted	3	3 180
Rambutan	Nephelium lappaceum	Planted	3	1 620
Daminiya	Grewia damine	Naturally grown	3	1 620
Tamarind	Tamarindus indica	Naturally grown/planted	3	1 620

Timber production potential

The contribution of home gardens to timber production is well known. The findings of this study can be used to obtain a tentative estimate of the timber production potential of home gardens in different climatic zones. Of the 76 species considered in this analysis, 61 species are capable of producing industrial timber. Species with above one million individuals and capable of producing industrial timber are shown in Table 15. There are 17 such species, which represent 83 percent of the total number of trees recorded during the survey.

The earlier FSMP studies indicated that one hectare of home gardens would produce 0.95 m³ of sawlogs and 0.5 m³ of poles per year. According to this estimate poles account for 34 percent of the total volume production. Multi-purpose tree species (e.g. jak, coconut, rubber and mango) are rarely used for poles and small-diameter timber. The bulk of poles and small-diameter timber is produced from other species, especially exotics (e.g. alstonia, eucalyptus, mahogany). The potential timber production has been calculated for each species taking into account the above facts (Table 15). In addition, it is assumed that only 40 to 70 percent of the total number of trees, depending on the species, reaches maturity to produce sawlogs. Average values have been used for the rotation age and timber volume of individual trees (volume over bark).

Table 15. Estimated sawlog production

Species name		Category	Total no. of trees	Estimated no. of trees that would reach maturity	Rotation age (years)	Timber volume per tree (m³)	Estimated timber volume (m³)
Local	Botanical	Category	Total no. of trees	Estimated no. of trees that would reach maturity	Rotation age (years)	Timber volume per tree (m³)	Estimated timber volume (m³)
Coconut	Cocos nucifera	Timber & food	38 616 649	27 031 654	50	0.15	81 095
Rubber	Hevea brasiliensis	Timber	17 101 488	10 260 893	30	0.3	102 609
Jak	Artocarpus heterophyllus	Timber & food	10 437 142	8 349 714	40	0.5	104 371
Mahogany	Swietenia macrophylla	Timber	6 410 248	2 564 099	30	0.6	51 282
Alstonia	Alstonia macrophylla	Timber	5 968 286	2 387 314	25	0.3	28 648
Mango	Mangifera indica	Timber & food	5 607 688	3 925 382	40	0.4	39 254
Albizzia_1	Albizia molucana	Timber	5 607 581	2 243 032	25	0.4	35 889
Eucalyptus	Eucalyptus spp.	Timber	4 061 191	1 624 476	25	0.6	38 987
Teak	Tectona grandis	Timber	3 293 609	1 317 444	35	0.6	22 585
Margosa	Azadirachta indica	Timber	3 044 932	2 131 452	45	0.4	18 946
Lunumidella	Melia dubia	Timber	2 349 245	1 409 547	25	0.4	22 553
Kitul	Caryota urens	Timber & food	1 751 016	1 225 711	35	0.15	5 253
Satin	Chloroxylon swietenia	Timber	1 489 903	1 042 932	70	0.4	5 960
Sabukku	Grevillea robusta	Timber	1 460 721	584 288	30	0.35	6 817
Halmilla	Berrya cordifolia	Timber	1 185 466	829 826	40	0.4	8 298
Rambutan	Nephelium lappaceum	Timber & food	1 177 920	824 544	40	0.4	8 245
Toona	Toona sinensis	Timber	1 023 771	511 886	25	0.4	8 190
Daminiya	Grewia damine	Timber	1 001 625	600 975	40	0.4	6 010
Total							594 992

Five exotic timber species (mahogany, alstonia, albizzia, eucalyptus and teak), which are later additions to the species mix of home gardens, account for 30 percent of the total timber volume produced in home gardens. Rubber alone would produce about 17 percent of the timber volume while three main multi-purpose tree species traditionally grown in home gardens (coconut, jak, and mango) would produce 38 percent of the timber volume.

The FSMP estimated the production potential of home gardens as 0.583 million m³ of sawlogs in 2000 (Table 4). The estimated volume using the data in this survey is 0.594 million m³. This is about 25 percent higher than the FSMP estimates considering that the study has covered only 87 percent of the country and the volume has been calculated only for 83 percent of the species found in home gardens.