Canopy leaf area index and litterfall in stands of the mangrove Rhizophora apiculata in Ca Mau Province, Vietnam (ACIAR Project FIS/94/12)

Brief description

Sampling was carried out in monocultures of Rhizophora apiculata aged 6, 9, 10, 12, 21 and 36 years in three mixed shrimp farming-mangrove forestry enterprises (Tam Giang 3, SFFE 184 and Kien Vang) in Ca Mau Province, the southern-most province of the Mekong Delta in Vietnam.Three litter traps of 1 m² in cross-sectional area were hung beneath the canopy in each stand. The litter traps were emptied at monthly intervals for 1 year, and the samples sorted into leaves, stipules, flower parts, propagules and a combination of woody material and debris. After counting the number of leaves, stipules and propagules in each sample, all fractions were oven dried to constant weight at 80°C for determination of dry weight (g dry weight/m² ground area/year).Canopy leaf area indices (LAI) were measured in six plots of each age, including those in which litter samples were collected. Measurements were made using a light attenuation method, in which leaf area index is estimated from the ratio of the light flux density beneath the canopy to that above the canopy, assuming that light attenuation within the canopy follows the Beer-Lambert Law. Between 100 and 200 measurements were made of the light flux density beneath the canopy on a clear sunny day between 1100 and 1400 hours, using a handheld quantum sensor. Measurements of the light flux density before and after the readings taken beneath the canopy were made in an open area well outside the canopy. All light readings were corrected for solar angle. This correction was calculated from the length of the shadow cast by a stick of known height thrust vertically into a flat area of ground outside the canopy. This research was undertaken to:-quantify the rate of litter fall in mangrove forests of different ages in Ca Mau Peninsula: mangrove derived detritus is a major source of carbon for estuarine food webs-investigate the dynamics of leaf production and leaf loss in relation to the leaf area index of mangrove stands of different ages: these relationships underpin the primary productivity, growth and yield of mangrove forests -investigate reproductive phenology and quantify seed (propagule) production in stands of different ages: this allows prediction of the seed supply for further plantings This research was part of a larger study, which aimed to develop better strategies for integrating aquaculture and mangrove forestry in the lower Mekong Delta, Vietnam.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The light attenuation method used to measure leaf area index is described in:Clough BF, Ong JE and Gong WK (1977) Estimating leaf area index and photosynthetic production in canopies of the mangrove Rhizophora apiculata. Marine Ecol. Prog. Series 159, 285-292.

Notes

Credit
Clough, Barry F, Dr (Principal Investigator)