Assessment of tree resources in the home gardens of Sri Lanka

Species distribution according to girth classes

Data were collected according to two different girth classes (below and above 30 cm girth). Most species have higher numbers of trees in the lower diameter class indicating the sustainable nature of home gardens. Notable differences are Albizzia molucana, eucalyptus, Gravilia robusta and Toona sinensis, which exhibit bigger trees. The four species are exotics and were not grown traditionally in home gardens until recently. Using multi-purpose tree species for smaller-diameter timber is not common as they are grown primarily for other products (e.g. coconut, rubber, jak and mango). Exotic timber species, on the other hand, are used for poles and small-diameter timber as and when required. This may explain to some extent the lower number of smaller diameter trees of exotic species.

The girth classes for coconut are of little use as an indicator of sustainable management, as coconuts have a girth exceeding 30 cm at all stages of growth. Small-scale rubber planting in home gardens and adjoining areas declined over the years owing to the uncertainty of rubber prices. Many former rubber areas have been converted to tea and cinnamon in the recent past. The lower number of small-diameter rubber trees is probably attributable to the decline in interest in rubber. Table 11 shows the total number of trees in each girth class.

Table 11. Tree distribution according to girth classes

Species Name		Family	Category	Girth class		Total
Local	Botanical			>30cm	<30 cm
Coconut	Cocos nucifera	Palme	TF	29 362 285	9 254 334	38 616 649
Rubber	Hevea brasiliensis	Euphorbiaceae	T	10 691 775	6 409 713	17 101 488
Jak	Artocarpus heterophyllus	Moraceae	TF	5 515 990	4 921 152	10 437 142
Arecanut	Areca catechu	Palme	F	2 661 675	7 036 269	9 697 944
Mahogany	Swietenia macrophylla	Meliaceae	T	1 105 066	5 305 182	6 410 248
Alstonia	Alstonia macrophylla	Apocynaceae	T	2 719 116	3 249 170	5 968 286
Mango	Mangifera indica	Anacardiaceae	TF	2 933 572	2 674 116	5 607 688
Albizzia_1	Albizia molucana	Fabaceae	T	4 148 863	1 458 678	5 607 581
Eucalyptus	Eucalyptus spp.	Myrtaceae	T	2 408 844	1 652 347	4 061 191
Teak	Tectona grandis	Verbenaceae	T	1 522 317	1 771 292	3 293 609
Margosa	Azadirachta indica	Meliaceae	T	1 357 844	1 687 088	3 044 932
Cashew	Anacardium occidentale	Anacardiaceae	TF	1 151 863	1 849 377	3 001 240
Lime	Citrus aurantifolia	Rutaceae	F	12 013	2 472 374	2 484 387
Lunumidella	Melia dubia	Meliaceae	T	1 251 112	1 098 133	2 349 245
Weera	Drypetes sepiaria	Euphorbiaceae	T	3 974 874	11 481 516	2 073 390
Guava	Psidium guajva	Myrtaceae	F	70 716	1 719 310	1 790 026
Kitul	Caryota urens	Palme	TF	809 525	941 491	1 751 016
Satin	Chloroxylon swietenia	Rutaceae	T	713 782	776 121	1 489 903
Orange	Citrus cinensis	Rutaceae	F	20 790	1 447 593	1 468 383
Sabukku	Grevillea robusta	Proteaceae	T	891 560	569 161	1 460 721
Bamboo	Bambusa vulgaris	Bambusaceae	T	369 924	963 149	1 333 073
Gliricidia	Gliricidia sepium L..	Euphorbiaceae	T	434 510	818 375	1 252 885
Halmilla	Berrya cordifolia	Tiliaceae	T	503 663	681 803	1 185 466
Rambutan	Nephelium lappaceum	Sapindaceae	TF	531 295	646 625	1 177 920
Toona	Toona sinensis	Meliaceae	T	639 165	384 606	1 023 771
Daminiya	Grewia damine	Tiliaceae	T	372 663	628 962	1 001 625
Butter fruit	Persea americana	Lauraceae	F	229 473	756 688	986 161
Wood apple	Limonia acidissima	Rutaceae	TF	320 223	628 529	948 752
Del	Artocarpus altilis	Moraceae	TF	503 085	407 388	910 473
Hora	Dipterocarpus zeylanicus	Dipterocarpaceae	T	373 536	491 901	865 437
Milla	Vitex altissima	Verbenaceae	T	345 797	428 622	774 419
Ketakela	Bridelia retusa	Euphorbiaceae	T	337 088	423 154	760 242
Tamarind	Tamarindus indica	Fabaceae	TF	272 991	416 931	689 922
Kumbuk	Terminalia arjuna	Combritaceae	T	324 890	362 063	686 953
Kon	Schleichera oleosa	Sapindaceae	T	285 113	379 423	664 536
Damba	Syzygium assimile	Myrtaceae	T	250 691	376 430	627 121
Murunga	Moringa oleifera	Moringaceae	F	23 013	598 271	621 284
Helamba	Mitragyma parvifolia	Rubiaceae	T	418 297	184 156	602 453
Palu	Manilkara hexandra	Sapotaceae	T	342 959	256 939	599 898
Welang	Pterospermum suberifolium	Sterculiaceae	T	208 850	355 581	564 431
Kolon	Adina cordifolia	Rubiaceae	T	267 154	281 310	548 464
Suriyamara	Albizia odoratissima	Fabaceae	T	235 364	274 227	509 591
Nedun	Pericopsis mooniana	Fabaceae	T	183 924	289 484	473 408
Jambu	Syzygium malaccensis	Myrtaceae	F	42 706	420 979	463 685
Aralu	Terminalia chebula	Combritaceae	TF	191 813	244 486	436 299
Gini sapu	Michelia champaca	Magnoliaceae	T	228 338	186 935	415 273
Kaduru	Thevetia peruviana	Apocynaceae	T	121 434	261 080	382 514
Ipil Ipil	Leucaena leucocephala	Fabaceae	T	163 087	210 334	373 421
Gammalu	Pterocarpus marsupium	Fabaceae	T	159 744	190 697	350 441
Anoda	Anona cherimolia	Annonaceae	F	6 050	319 845	325 895
Mee	Madhuca longifolia	Sapotaceae	T	175 665	122 722	298 387
Cocoa	Theobroma cacao	Sterculiaceae	F	36	259 462	259 498
Mora	Dimocarpus longana	Sapindaceae	TF	135 792	116 819	252 611
Kenda	Macaranga peltata	Euphorbiaceae	T	104 192	139 828	244 020
Veralu	Elaeocarpus serratus	Elaeocarpaceae	F	89 735	144 919	234 654
Gansuriya	Thespesia populnea	Malvaceae	T	102 219	100 634	202 853
Delum	Punica granatum	Panicaceae	F	30	197 911	197 941
Kottamba	Terminalia catappa	Combritaceae	T	92 201	94 464	186 665
Pihimbiya	Filicium decipiens	Sapindaceae	T	70 306	114 652	184 958
Bulu	Terminalia bellirica	Combritaceae	T	55 994	124 696	180 690
Ebony	Diospyros ebenum	Ebenaceae	T	89 507	84 498	174 005
Godapara	Dillenia retusa	Dilleniaceae	T	81 872	90 065	171 937
Domba	Calophyllum inophyllum	Clusiaceae	T	72 204	95 543	167 747
Beli	Aegle marmelos	Myrtaceae	F	23 106	142 615	165 718
Kahata	Careya arborea	Lecythidaceae	T	74 341	90 953	165 294
Wewarana	Alseodaphne semicarpifolia	Lauraceae	T	25 774	137 107	162 881
Hik	Lannea coromandelica	Anacardiaceae	T	121 229	27 848	149 077
Ehela	Cassia fistula	Fabaceae	T	49 382	91 583	140 965
Hulanhik	Chukrasia tabularis	Meliaceae	T	58 782	72 718	131 500
Palmairah	< span >Borrasus flabellifer	Palme	TF	65 190	62 150	127 340
Nelli	Phyllanthus emblica	Euphorbiaceae	F	24 279	92 449	116 728
Ambarella	Spondias dulcis	Anacardiaceae	F	18 663	67 537	86 200
Albizzia_2	Albizzia lebbeck	Fabaceaea	T	17 018	53 092	70 110
Gal siyambala	Dialium ovoideum	Fabaceae	TF	35 071	22 233	57 304
Etamba	Mangifera zeylanica	Anacardiaceae	TF	16 395	35 708	52 103
Coffee	Coffea arabica	Rubiaceae	F		40 936	40 936

Species density

The total number of trees reported in the survey was used to calculate the district base species density in home gardens. Unusually low densities appear in the northern and eastern administrative districts due to the partial coverage of the area. Although there are some variations, the average density is about 200 trees per hectare. Tree density is highest in the wet zone districts followed by the intermediate and dry zones (Table 12).

Table 12. Tree density in different districts and climatic zones

District	Land area (ha)	Area of home gardens (ha)	Home gardens%	Total no. of trees	Tree density/ha	Population	Climatic zone
Kegalle	168 328	46 782	27.8	22 226 316	475	779 000	Wet
Matale	206 050	20 258	9.8	8 019 140	396	442 000	Intermediate/dry
Nuwara Eliya	174 109	9 172	5.3	3 541 264	386	700 000	Wet
Kurunegula	489 787	72 892	14.9	23 505 457	322	1 452 000	Interm ediate/dry
Kalutara	164 391	33 156	20.2	10 533 752	318	1 060 000	Wet
Ampara	450 031	16 245	3.6	4 684 499	288	589 000	Dry
Colombo	68 469	8 577	12.5	2 427 509	283	2 234 000	Wet
Badulla	285 673	50 764	17.8	12 286 263	242	775 000	Intermediate/dry
Gampaha	141 890	56 884	40.1	11 057 048	194	2 066 000	Wet
Moneragala	576 763	56 739	9.8	10 905 497	192	396 000	Dry
Ratnapura	327 034	56 462	17.3	9 732 963	172	1 008 000	Wet
Galle+Matara	292 085	99 000	33.9	15 799 018	160	1 752 000	Wet
Hambantota	262 307	44 922	17.1	6 315 661	141	525 000	Dry
Anuradhapura	722 178	56 143	7.8	7 820 520	139	746 000	Dry
Kandy	192 808	61 029	31.7	5 694 609	93	1 272 000	Wet
Puttalam*	315 848	64 747	20.5	4 411 647	68	705 000	Dry
Polonnaruwa	344 988	36 180	10.5	1 730 037	48	359 000	Dry
Batticaloa*	263 983	14 359	5.4	446 427	31	486 000	Dry
Trincomalee*	267 991	14 083	5.3	281 137	20	340 000	Dry
TOTAL/AVG	5 714 713	818 394	14.3	161 418 764	197

* The entire area is not covered by the study for security reasons