Carmen Sotelo Montes

Origins and genetic conservation of tropical trees in agroforestry systems: a case study from the Peruvian Amazon

Hundreds of native tree species are currently found in extensive agroforestry ecosystems in the Peruvian Amazon, forming an important reservoir of biodiversity. To further promote conservation, farmers are encouraged to supplement intra-specific genetic diversity in these populations with seed collected from local forests. For some tree species, however, this approach may be inappropriate, as stands of these taxa already found on-farm may not be of local origin. Despite this issue being of importance for conservation, little information is available on the history of cultivated trees in the region, a situation that we here rectify for the important fruit tree Inga edulis. Based on nuclear SSR and chloroplast DHPLC analyses of closely geographically matched natural and planted stands at five sites, it appears that cultivated material of I. edulis is primarily of non-local origin, indicating that conservation based on new wide-scale infusions from local wild stands into farms may be inappropriate in the region. Although nuclear and chloroplast diversity were both lower in planted stands, values were still relatively high (∼80 and 70% of natural stands, respectively), indicating that when farmers plant trees, good collection practice of seed from already cultivated I. edulis should be an effective means for ensuring long-term conservation on farms.

Variation in stem-growth and branch-wood traits among provenances of Calycophyllum spruceanum Benth. from the Peruvian Amazon

Calycophyllum spruceanum Benth. is an important tree for timber, charcoal and firewood in the Peruvian Amazon. The first provenance trial was established on farms in three zones located in one watershed in the Peruvian Amazon. The three zones differ in soil fertility and rainfall. Seven provenances from the Peruvian Amazon were tested in all three zones. Variation in four stem-growth traits (height, diameter, number of nodes and branches) and two branch-wood traits (basic density, heat content) was analyzed 18 months after establishment. There were significant differences in stem height and number of stem nodes among provenances in the analysis across zones. Provenance-related variation in stem-growth traits was most significant in the zone with the most fertile soils and highest rainfall. Branch-wood traits did not vary significantly among provenances in the analysis across zones or within zones. Branch-wood heat content was correlated with latitude, increasing from north to south, but this was only observed in a zone with low soil fertility and intermediate rainfall. Branch-wood density was correlated positively with stem diameter in the driest zone, but negatively with stem nodes in the intermediate zone and with stem height in the wettest zone. Results illustrate the potential for selection of fast-growing provenances, and the importance of replicating trials on different test environments to detect variation among provenances.

Phenotypic Selection of Calycophyllum spruceanum on Farms in the Peruvian Amazon: Evaluating a Low-Intensity Selection Strategy

Abstract A low-intensity selection strategy was recommended for timber trees in the Peruvian Amazon to maintain genetic variation on farms and produce modest gains in tree growth. The effectiveness of this strategy was evaluated using Calycophyllum spruceanum. Farmers selected 66 mother trees of different ages on farms in seven locations (~20% of all trees in the locations) in one watershed, based on a visual assessment of growth, form and external disease symptoms. Another 66 mother trees were chosen at random. Tree height, stem diameter, stem bifurcations and mortality of progeny of the selected and random groups of mother trees were evaluated at 15, 26 and 38 months in a provenance/progeny test located on farms in the same watershed. Height was significantly greater (10%) in the selected group at 15 months, but it did not differ significantly between the selected and random groups at 26 and 38 months. There were no significant differences in diameter, bifurcations and mortality between the groups. There was significant variation in height and diameter at all measurement ages due to families, and results suggested that variation in bifurcations and mortality due to families was also significant. Based on approximate 95% confidence intervals, family variances in height and diameter did not differ significantly between the selected and random groups at any measurement age, but evaluations should continue to confirm these tentative conclusions. Some practical implications for tree improvement programs are discussed.

Variation in growth, wood density and carbon concentration in five tree and shrub species in Niger

There is little information about variation in growth, wood density and carbon concentration in native tree and shrub species in Africa. This information is needed to make realistic projections about carbon sequestration of different species in different environments. Farmers manage natural regeneration of many native species in the drylands of Niger, so there is interest in carbon sequestration potential of the species. The objectives of this study were to determine: (1) if tree height, stem diameter, mean ring width, wood density and carbon concentration differ among five tree and shrub species (Combretum glutinosum, Combretum micranthum, Combretum nigricans, Guiera senegalensis, Piliostigma reticulatum) in Niger; (2) if variation within species is affected by land use type (parkland agroforests, woodlands), soil type (sandy, rocky), terrain type (temporarily flooded, flat, hill slope) and mean annual rainfall; and (3) if growth variables, wood density and carbon concentration are correlated in the five species. Environmental variables did not have strong effects on growth and wood variables of the species, and some effects differed among species. Height across species increased with mean annual rainfall. Stem diameter and mean ring width across species were greater in parkland agroforests than in woodlands. Carbon concentration was positively correlated with growth variables of four species, but was not correlated with wood density in most species. Correlations between wood density and growth differed in sign among some species. We conclude that above-ground carbon sequestration per tree probably increases with mean annual rainfall and is greater in parkland agroforests than in woodlands.