Homegarden agroforestry systems are suggested to hold a large potential for climate change mitigation and adaptation. This is due to their multifunctional role in providing income, food and ecosystem services while decreasing pressure on natural forests and hence saving and storing carbon. In this paper, above-ground biomass carbon and tree species diversity of trees was quantified in homegardens around two villages in the dry south-eastern part of Moneragala district of Sri Lanka. A total of 45 dry zone homegardens were sampled on size, diameter at breast height, tree height and species diversity. Using allometric equations, we find a mean above-ground biomass stock of 13 Mega grams of carbon per hectare (Mg C ha -1 ) with a large range among homegardens (1 to 56 Mg C ha -1 , n=45) due to a variation of tree diversity and composition between individual homegardens. Mean above-ground carbon stock per unit area was higher in small homegardens (0.2 ha, 26 Mg C ha -1 , n=11) and statistically different compared to medium (0.4-0.8 ha, 9 Mg C ha -1 , n=27) and large (1.0-1.2 ha, 8 Mg C ha -1 , n=7) homegardens. In total, 4,278 trees were sampled and 70 tree species identified and recorded. The Shannon Wiener index were used to evaluate diversity per homegarden and ranged from 0.76 to 3.01 with a mean value of 2.05  0.07 indicating a medium evenly distributed diversity of sampled tree species. The results show a vast heterogeneity in terms of carbon stock and tree diversity within the less studied dry zone homegardens; results that contribute to more knowledge of their expansion potential as well as climate mitigation and adaptation potential. The results are also useful for whether homegardens should be considered to be included as an activity to enhance natural forest cover within Sri Lanka's newly commenced UN-REDD National Programme.

No abstract

The genus Cinnamomum consists of about 250 species spread globally. Out of these, C. verum (C. zeylanicum), also known as true cinnamon or Ceylon cinnamon, has gained worldwide attention due to its culinary uses and medicinal values. Sri Lanka is the largest true cinnamon producer in the world and accounts for about 80–90% of global production. Other than the cultivated species, Sri Lankan natural vegetation is home to seven endemic wild species of the genus Cinnamomum. While these are underutilized, proper identification and characterization are essential steps in any sustainable conservation and utilization strategies. Currently, species identification is purely based on morphological traits, and intraspecific diversity has made it more challenging. In this study, all the eight Cinnamomum species found in Sri Lanka, C. capparu-coronde, C. citriodorum C. dubium, C. litseifolium, C. ovalifolium, C. rivulorum, C. sinharajaense, and C. verum were collected in triplicates and identified using typical morphological traits. DNA extracted with the same collection was assessed with universal barcoding regions, rbcL, matK, and trnH-psbA. While no intraspecific sequence differences were observed in C. citriodorum, C. rivulorum, and C. verum, the others had polymorphic sites in one, two, or all regions assessed. Interestingly, two individuals of C. sinharajaense had identical barcodes to the cultivated species C. verum, while the other one had one variable cite in matK region and three cites in trnH-psbA reigon. Further, one C. dubium and one C. capparu-coronde accession each had identical, rbcL, and trnH-psbA sequences while those had only a single nucleotide variation observed in matK region. Overall, the phylogeny of Cinnamomum species found in Sri Lanka could not be completely resolved with DNA barcoding regions studied.

Cinnamomum zeylanicum Blume is a commercially important species cultivated in Sri Lanka and traded as Ceylon cinnamon or true cinnamon. In addition, seven endemic wild species of the genus Cinnamomum have been reported in Sri Lanka. The literature on wild relatives of C. dubium, C. capparucoronde, C. citriodorum, C. litseaefolium, C. ovalifolium, C. rivulorum and C. sinharajaense is limited. Therefore, proper field level identification and differentiation of both wild and cultivated species are critical for the conservation and utilization of such species. Since the cinnamon is a crosspollinated species, intra-species diversity is also a possibility. Our work focused on inter-and intra-species diversity of Cinnamomum leaf morphology to develop a "Leaf Morphological Index" for field-level identification of reported species. Forty accessions, representing a minimum of two from each species, collected from natural and cultivated habitats, were assessed with 12 morphological characters. The highest within-species variation was observed in C. zeylanicum, followed by C. dubium. Of the morphological characters, five-leaf traits, leaf shape, apex, base, venation, and size significantly contributed to the main principle components. Therefore, those traits were used for developing a leaf morphological index. The morphological index could distinguish all the species at the field level.

Clearing of natural ecosystems and land degradation due to unsustainable agricultural practices are becoming threats to the sustainability and productivity of agricultural systems in Sri Lanka. Tropical home gardens can be identified as an alternative, which provide economic and socio-cultural benefits to the subsistence farmers. These home gardens generate income as well as serve as a source of nutrition to the households. Along with the economic value, home gardens are known for their high species diversity. The broad objective of this study was to quantify the species diversity of perennials and annuals by determining the species composition of 30 home gardens in the Meegahakiula region of Sri Lanka. These 30 home gardens were selected randomly from three slope categories according to topographical arrangement as steep (> 30% slope), moderate (10-30% slope) and flat land (< 10% slope). The Shannon Weiner and Margalef indices were calculated in order to ascertain the levels of diversity of perennial and annual species in these home gardens. The relative importance value was calculated separately for perennial species and annual species. The Shannon Weiner index of perennial species was similar to that of the natural forest in Kerala, India and home gardens in Indonesia. Five major perennial species categories and six important annual species were identified in home gardens. There was a greater distribution of annuals in home gardens in the flat land category while the home gardens with moderate and steep land category had a distribution of perennial species.