Summary, Introduction, Methods, Analysis, Results, Discussion, References, Acknowledgements, Photos, Links

Marona appears to be exclusively restricted to floodplain forest habitats associated with large meandering rivers such as the Madre de Dios. The extent of forest where the species was found was not reliably estimated using the spatial analysis techniques employed, due to insufficient separability or spectral overlap of forest types, a result of highly textured reflectance patterns at 30 m spatial resolution. Such problems have also been found and are discussed at length by Foody (1996abc, 2001), Blanco & Garcia (1997) and Hill (1999), who suggest other methods such as image segmentation, fuzzy modelling and texture analysis. Nevertheless, it might be prudent to determine the probability of encountering Marona in the regions indicated by the classification analysis undertaken in this study in order to determine its level of accuracy.

Areas around the communities of Boca Amigo and San Juan Grande harbour the majority of the Marona resource in the study site. The spatial distribution of Marona in the former is relatively clumped, as revealed by the density sampling techniques, and closely associated with large, multiple tree-fall gaps where light levels are high enough to sustain this apparently light demanding species. Although the species tends to prefer these areas of intermediate scale natural disturbance, there is little evidence to suggest that anthropogenic impacts have influenced current distribution to any degree. Only in the case of San Juan Grande, where large areas of forest have been cleared for goldmining purposes, and subsequently abandoned, in or near areas formerly dominated by Marona, is the species taking advantage of the high light environment and vigorously recolonising. The study also tentatively found that soil texture within large gaps, such as those investigated, is dominated by clays. This may indicate that soil properties, perhaps in the form of drainage characteristics, are important factors affecting the spatial distribution of Marona. This is not surprising given the likely water and stability requirements for such a large and fast-growing species. Nevertheless, such properties require more rigorous investigation in the future.

Abundance around Boca Amigo was high relative to other areas in the study site, although very much lower than potential abundance of a closely related species (Londoño 1998). The vast majority of clumps were also found to be small, averaging just 6 culms/clump. This evidence, in addition to the fact that mature flowering clumps were found in addition to remnants of large-diameter culms from long-dead mature clumps (Plate 2), suggest that the Marona population in the area is recovering from, and to some degree still undergoing, a flowering event which must have begun in the last 5 years or so. Local knowledge gleaned from local informants suggests that the abundance of large-diameter culm clumps was greater in the past than at present. The majority of the Marona population sampled, therefore, could simply be young plants which have regenerated from seed. So, it would be expected that mean clump size and mean culm dbh, which are so much lower than those associated with mature plants, will increase over the next few years. This process could be closely monitored, now that the location and characteristics of clumps in the area is known and permanent sample plots have been developed, in order to test this theory.

If one were to assume that an economic culm yields 5 m of economic length and each metre has a value of 1 Sole (US$ 0.29), the current going rate for Marona in the town of Puerto Maldonado (B. Zlatar pers. com.), then the standing value of Marona in the floodplain forest around Boca Amigo, at current population levels is 57 089 Soles (US$ 16 556) or approx. 18 Soles (US$ 5.00)/ha. The exchange rate at the time of this study was 3.5 soles to the dollar. The true value of the resource would, however, be much less, as extraction, a major cost in Madre de Dios in terms of labour (Flores and Ashton 2000), and transportation costs would need to be taken into account. Whether or not it will be economical in the future to extract Marona from this area will depend on assessing the magnitude of these costs, developing quality products of high marketable value and ensuring a constant supply of high quality raw material. It is encouraging to note that the abundance of economic culms is likely to increase in the medium term as the population ages. Evidence by Tripathi & Singh (1994), who studied Dendrocalamus strictus (a large-diameter bamboo species) in India, suggests that perhaps culm harvesting could even have a positive effect on culm recruitment far and above normal recruitment levels, although Londoño did not find a similar relationship in a long-term evaluation of G. angustifolia in Colombia. Nevertheless, it is a factor that should be monitored in the case of Marona.

A comprehensive analysis of economic value, utilising the methodologies set out by Godoy, Lubowski and Markandya (1993) and Flores and Ashton (2000), in conjunction with a full scale market study, and a detailed ecological assessment of population dynamics and genetic variation, the latter to assess how many distinct clones exist in the area and thus gauge future risk from synchronous flowering events, would be required before a decision is taken on whether this species should be brought under management.

Results clearly indicate that it is possible to use culm diameter and height to estimate allometrically the biomass of Marona culms, a finding also widely reported in other studies of bamboo (Tieren et al. 1987, Chin-ming & Tsair-huei 1992, Torezan, Marcelo & Silveira 2000). Furthermore, the freshweight of a culm can be more than double its dry mass, due to the large quantities of water stored in the tissues. This fact may help explain the high incidence of culm cracking during post-harvest air drying.

The study has highlighted that if harvested and simply left to dry in the open culms tend to suffer a number of undesirable fates, including severe cracking or splitting, as well as insect and fungal attack. Of all the treatment and drying methods tested, both chemical treatment with a 2% solution of BBA and "vinegrar", a process which involves in situ drying of culms with leaves still attached, proved to be the most appropriate post-harvest management technique for Marona. The former replaces starch and other photosynthate products in the culm, which sustain insect borers and fungi, with a chemical preservative and the latter reduces these factors naturally during normal evapotranspiration and respiration as the culm slowly dies (Londoño pers. com.).

Like most species of bamboo, the growth rate of Marona is impressive, averaging 16 cm/day. The potential value of this plant as a means for carbon sequestration, especially if brought under management, could be significant and should be investigated in more detail using methodologies similar to those employed in other studies (Taylor & Zisheng 1987, Chin-ming & Tsair-huei 1992, Tripathi & Singh 1994, Shanmughavel & Francis 1996, Silveira & Klink unpubl.). Nevertheless, whether it can sequester more carbon than canopy trees it tends to replace is debatable.

The vegetative propagation experiments were on the whole very successful, revealing the most promising region of the plant to be the mid region of the culm. Longhi (1998) also recommended this region for a close relative of Marona. The permanently marked plots installed at the LARC and the numbered seedlings should be monitored over the next few years to assess the medium term success of the techniques employed. Other soil and habitat types, particularly those in and around areas of anthropogenic disturbance, such as abandoned gold-mining pits or "chupaderas", should also be investigated.

Summary, Introduction, Methods, Analysis, Results, Discussion, References, Acknowledgements, Photos, Links