Assessing the Population Status of a Tree Species Using Distance Sampling: Aquilaria crassna

Lack of reliable and accurate field data affect assessments of population status of tree species, especially tropical taxa with broad distributions. Use of distance sampling techniques may help to overcome the problem. This paper describes a method for estimation of absolute density of a rare tree species with scattered and clumped distribution, using line transect distance sampling. The method was applied to previously harvested populations of Aquilaria crassna Pierre ex H. Lec. (Thymelaeaceae) at four sites in Northern Laos. This species is destructively harvested to yield agarwood, probably the world’s most valuable nontimber forest product and categorised as ”critically endangered“. The average density of felled A. crassna trees at the four sites was 2.2 ha−1, indicating that harvesting has been extensive. However, the estimated densities of living saplings, 10.9 ha−1, small trees (DBH < 10 cm), 10.6 ha−1, and larger trees (DBH ≥ 10 cm), 1.7 ha−1, suggest that populations are not wiped flat. The survey method should stand a good chance of wider use as a tool in management and conservation of a wide range of tree species. Results of the present case study could suggest that the conservation status of A. crassna should be re-categorised

Plant density and life history traits of <i style="">Aconitum spicatum</i> in North-central Nepal:effects of elevation and anthropogenic disturbances

Increasing cross-border trade of medicinal and aromatic plants (MAPs) has put heavy pressure on a considerable number of species in the Himalayas. One of the threatened species in Nepal is Aconitum spicatum. Unfortunately for this species and for many others, our knowledge on population ecology and performance across the distribution range is insufficient, hindering the formulation of species-specific management plans. We therefore studied density and population structure of A. spicatum and assessed variation in its life history traits among three populations (subalpine, lower alpine and alpine) along an elevation gradient (3,000–4,200 m a.s.l.) in Annapurna Conservation Area, north-central Nepal. The results show that human disturbances and topographic factors contributed to the variation in density and life history traits. The overall density ranged between 0.56 ± 0.09 (Mean ± SE) and 2.48 ±  0.24 plants/m2 with highest mean density in the lower alpine and lowest in the subalpine population. The subalpine population was also characterized by lower investment in reproductive structures with lowest seed mass and low seed viability and fecundity. Among the environmental variables tested, harvesting, animal droppings and fire appeared to be the most important factors affecting density of different life stages of A. spicatum. The prevailing harvesting pattern is destructive as it involves uprooting of the whole plant and this appears to be a main reason for low recruitment and reduced density of the subalpine population. The level of disturbance decreased with increasing elevation. In terms of reproductive effort, the alpine population performed best. Our results indicate that the viability of A. spicatum populations depends on controlling over-harvesting and pre-mature harvesting of tubers and protecting younger life stages from grazing, trampling and fire. We therefore recommend that when formulating management guidelines, measures aiming to mitigate such anthropogenic disturbances should be considered

Wild edible plant knowledge, distribution and transmission:a case study of the Achí Mayans of Guatemala

BACKGROUND: Knowledge about wild edible plants (WEPs) has a high direct-use value. Yet, little is known about factors shaping the distribution and transfer of knowledge of WEPs at global level and there is concern that use of and knowledge about WEPs is decreasing. This study aimed to investigate the distribution, transmission and loss of traditional ecological knowledge (TEK) concerning WEPs used by a Mayan community of Guatemala and to enumerate such plants. METHODS: The case study was carried out in a semi-isolated community where part of the population took refuge in the mountains in 1982–1985 with WEPs as the main source of food. Major variables possibly determining knowledge and therefore investigated were socio-demographic characteristics, distance to and abundance of natural resources and main source of knowledge transmission. A reference list of species was prepared with the help of three key informants. Information about the theoretical dimension of knowledge was gathered through free listing and a questionnaire survey, while practical skills were assessed using a plant identification test with photographs. All villagers older than 7 years participated in the research (n = 62 including key informants). RESULTS: A total of 44 WEPs were recorded. Theoretical knowledge was unevenly distributed among the population, and a small group including very few informants (n = 3) mentioned, on average, three times more plants than the rest of the population during the free listing. Practical knowledge was more homogeneously distributed, key informants recognising 23 plants on average and the rest of the population 17. Theoretical and practical knowledge increased with age, the latter decreasing in the late phases of life. Knowledge about WEPs was transmitted through relatives in 76% of the cases, which led to increased knowledge of plants and ability to recognise them. CONCLUSIONS: The WEP survey may serve as a reference point and as a useful compilation of knowledge for the community for their current and future generations. This study shows that the elder and the refugees living in the area for longer time know more than others about WEPs. It also shows the important role of knowledge transmission through relatives to preserve TEK