Rapid Assessment of Dispersal Failure and Seedling Recruitment of Large-Seeded Non-Timber Forest Products Trees in a Tropical Rainforest

Abstract

Forest managers and harvesters of non-timber forest products (NTFPs) need a tool for rapid measurement of the impact of their activities on seed dispersal and tree recruitment. Such a tool could be used for a prospective eco-label which would ensure regeneration. We propose, and have used a new rapid assessment protocol to sample and evaluate the impact of any anthropogenic disturbance on seed dispersal and seedling recruitment of hard-tegument fruit species enclosing large seeds. We set up this protocol in French Guiana for a large-seeded scatter-hoarded tree species, Carapa surinamensis (andiroba), at three different forest sites affected by a variety of anthropogenic pressures, such as hunting and logging. Over a limited time we assessed: 1) dispersal failure: from late May to mid-June, the proportion of seeds remaining undispersed was estimated by sampling the number of seeds, seedlings and fruit husks in 25-m 2 subplots under the tree crown; 2) recruitment effectiveness: in September-October, seedlings were sampled on four 100-m 2 plots located 5-15 m from the tree base around the tree crown. Altogether, 77 trees were sampled, some 1-2 hours being spent beneath each tree, during a total 4-6 weeks in the field for each dispersal and recruitment sampling. We showed that: 1) seed dispersal is affected by hunting, this being significantly marked in the coastal area, which faces major anthropogenic pressures; 2) logging treatments affect seed dispersal and regeneration, on the average. However, canopy gaps due to sylvicultural treatments raise the life expectancy of seedlings.Keywords: Andiroba, seed dispersal, seedling recruitment, rapid assessment, tropical rainforest Résumé Les gestionnaires ont besoin d'un outil permettant d'évaluer rapidement l'impact de l'exploitation forestière et de la collecte des produits forestiers non ligneux (PFNL) sur la dispersion des graines et la régénération des arbres. Cet outil permettrait d'établir un futur écolabel garantissant la régénération des espèces. Nous proposons une méthode rapide d'échantillonnage que nous avons utilisée afin d'évaluer l'impact des perturbations humaines sur la dispersion et la régénération des espèces à grosses graines et à coques dures. Nous avons testé ce protocole en Guyane française sur trois sites présentant différentes pressions anthropiques, comme la chasse et l'exploitation forestière, sur une espèce à grosses graines, Carapa surinamensis (andiroba). Dans un temps restreint, nous avons mesuré 1) la proportion de graines non dispersées : estimée entre fin mai et mi-juin en échantillonnant les graines et coques restées au sol à l'intérieur de quadrats de 25 m 2 sous la couronne ; 2) la régénération : en échantillonnant de septembre à octobre les plantules à l'intérieur de quatre quadrats de 100 m 2 , situés à 5-15 m de la base de l'arbre autour de la couronne. En 4 à 6 semaines, 77 arbres ont été échantillonnés pour la dispersion des graines et la régénération, soit 1 à 2 heures par arbre. L'étude montre que 1) la dispersion est aff...

Modifications of the rain forest frugivore community are associated with reduced seed removal at the community level

“…, Brodie et al. , Holbrook and Loiselle , Lermyte and Forget ). While the fact that hunting is responsible for the decline of large hunted species such as Ateles paniscus , Alouatta macconnelli and ungulates is the most parsimonious conclusion, we remain cautious regarding the factors leading to abundance changes in other, non‐hunted species.…”

“…, Brodie et al. , Holbrook and Loiselle , Lermyte and Forget ), but happens at the community level. At Nouragues, Burseraceae, Myristicaceae, Sapotaceae, and Fabaceae ( Inga spp.)…”

“…For each sampled tree, two proportions were calculated from these figures (Ratiarison and Forget , Lermyte and Forget , Boissier et al. ).…”

Evidence for Seed Dispersal by Rodents in Tropical Montane Forest in Africa

“…There was fruit shortage at the study site in 2008 and Carapa seeds were collected at a site ca 10 km away at the edge of the Kamiranzovu swamp (1910 m asl). In 2009 and 2010, the density of Carapa seeds was estimated using four 5 Â 5 m 2 quadrats per tree that captured fallen seeds (N = 16 trees in 2009 and ten trees in 2010; see Lermyte & Forget 2009 for a extensive description of sampling methods). Results of this sampling show that seed fall was greater in 2009 (mean = 4.1 seeds/m 2 ) than in 2010 (2.5 seeds/m 2 ; generalized linear model with a Poisson distribution of errors; w 2 = 439.17; df = 1; P o 0.0001).…”

Seed Removal Rates in Forest Remnants Respond to Forest Loss at the Landscape Scale

“…This is of paramount importance because species interaction is an often-missed component of biodiversity loss that can even precede species loss [15]. This rapid seed removal method allows the easier implementation of large-scale studies and provides a snapshot of the proportion of removed seeds by frugivores and seed predators [5,[16][17][18]. While not integrative of animal activity over the year, since seed removal of a given species can be estimated only during the fruiting period, it provides a realistic picture of it.…”