Impact of El Niño and Logging on Canopy Tree Recruitment in Borneo

Abstract

Dipterocarpaceae, the dominant family of Bornean canopy trees, display the unusual reproductive strategy of strict interspecific mast-fruiting. During 1986-99, more than 50 dipterocarp species dispersed seed only within a 1- to 2-month period every 3 to 4 years during El Nino-Southern Oscillation events. Synchronous seed production occurred across extensive areas and was essential for satiating seed predators. Logging of dipterocarps reduced the extent and intensity of these reproductive episodes and exacerbated local El Nino conditions. Viable seed and seedling establishment have declined as a result of climate, logging, and predators. Since 1991, dipterocarps have experienced recruitment failure within a national park, now surrounded by logged forest.

Fire as a large-scale edge effect in Amazonian forests

“…To date, edge effects in Amazonian forests, such as alterations in microclimate, forest dynamics and faunal communities, have been shown to penetrate from 10-400 m into fragment interiors (Bierregaard et al 1992, Laurance et al, in press, Lovejoy et al 1986. Preliminary evidence, however, suggests that some edge-related changes in tropical forests could penetrate much further than this, perhaps as far as several km into fragment interiors (Curran et al 1999, Laurance 2000.…”

Abundance of insect seed predators and intensity of seed predation on Shorea (Dipterocarpaceae) in two consecutive masting events in Peninsular Malaysia

“…The leading hypothesis concerns seed survival through the satiation of seed predators (Curran et al 1999, Janzen 1974. The predator satiation hypothesis posits reductions in the abundance of generalist seed predators during multi-year intervals between masting events followed by satiation of the remaining seed predators by massive, synchronous seed production during these events.…”

“…Many dipterocarp species in aseasonal lowland rain forests of western Malesia flower synchronously during masting (or general flowering) events, which usually occur at irregular intervals of 2-10 y (Ashton et al 1988). Very few individuals flower at other times, and successful recruitment of seedlings is limited to those masting events (Ashton et al 1988, Curran et al 1999.…”

Rapid land-use change and its impacts on tropical biodiversity

“…In agricultural and urban areas, acid rain, pesticides and herbicides, hydrological changes, livestock grazing, and pressure from invading species can degrade the ecology of forest fragments [Myers, 1987;Hobbs and Huenneke, 1992;Weathers et al, 2001]. Tropical forest fragments and isolated nature reserves are frequently affected by selective logging and fuelwood gathering [Curran et al, 1999[Curran et al, , 2004Oluput and Chapman, in press, 2004;Peres and Michalski, in press, 2004]. One of the most widespread threats to wildlife in fragmented tropical forests is hunting.…”

“…Each year, roughly 6 million ha of forest is selectively logged-an area twice the size of Belgium [Whitmore, 1997]. Logging has been most intensive in Southeast Asia [Dinerstein and Wikramanayake, 1993;Primack and Lovejoy, 1995;Curran et al, 1999Curran et al, ,2004 and is expanding rapidly in tropical Africa, Central America, the Amazon, and Melanesia (New Guinea and the Solomon Islands) [Laurance, 1998, Plant communities and forest architecture also change in response to logging disturbance. Along skid tracks and logging roads, the abundance and diversity of native understory herbs decline, whereas invading herbs from non-rainforest habitats increase sharply in abundance [Costa and Magnusson, 2002].…”