Mortality in trees

Death can take many forms in tropical trees. Natural disasters including hurricanes, landslides, earthquakes, floods or droughts, lightning strikes, high winds, and diseases, as well as old age, can all be causes of mortality. Tropical rain forests occur at sites differing considerably in incidence of intense natural disturbances. For instance, Carey et al. (1994) reported that 64% of mortality in Venezuela involved trees dying standing, whereas in Costa Rica (Lieberman et al. 1985b) and Central Amazonia (Rankin-de-Merona et al. 1990) this figure was only one quarter of stems, and in the wet climate and rugged topography of the Rio Hoja Blanca Hills in Ecuador it was further reduced to 15% (Gale & Barfod 1999), indicating more death through treefall in the latter sites.

Repeated enumerations of plots of tropical rain forest have generally found

Table 3.1. Estimates ofpopulation finite growth rates (X) and elasticity analysis for tropical rain-forest tree species based on Lefkovitch matrix model

Largest elasticities found for: P^, probabilities of remaining in the same stage (survival); Gtj, probabilities of advancing to following stages (growth); Fy, fecundities of seedling recruitment. Life stages: s, seeds; j, juveniles; pa, pre-adults; a, adults.

Table 3.1. Estimates ofpopulation finite growth rates (X) and elasticity analysis for tropical rain-forest tree species based on Lefkovitch matrix model

Largest

Longevity

Species

Life history

1

elasticity

(years)

Palms

Astrocaryum mexicanum

understorey, slow

0.99-1.01

puo

125

Chamaedora tepejilota

understorey, slow

0.97-1.12

Pu(p )

60

Coccothrinax readii

understorey, slow

1.01-1.10

U(P )

145

Euterpe edulis

understorey, slow

1.19-1.28

PU()

n.d.

Podococcus barteri

understorey, slow

1.01

U(P )

75

Pseudophoenix sargentii

understorey, slow

1.01-1.20

PU(P )

80

Thrinax radiata

understorey, slow

0.99-1.01

p rU(P )

120

Others

Araucaria hunsteinii

canopy, slow

0.99-1.09

PU()

100

Araucaria cunninghamii

canopy, slow

1.01-1.02

pu<>

100

Brosimum alicastrum

canopy, fast

1.06

PU( )

120

Cecropia obtusifolia

pioneer

0.99-1.03

PU( )' GUU)> Fij

35

Omphalea oleifera

canopy, medium

1.01

pu<>

140

Pentaclethra macroloba

canopy, slow

1.00

PU(P )

150

Stryphnodendron excelsum

canopy, slow

1.05

p rU(P )

150

From Alvarez-Buylla et al. (1996) and Silva Matos et al. (1999).

From Alvarez-Buylla et al. (1996) and Silva Matos et al. (1999).

Figure 3.1 Frequency distribution of mean annual mortality rate for stems 10-99 mm dbh for 202 species on Barro Colorado Island, Panama. Data fromCondit et al. (1995).

annual mortality rates for trees (> 10 cm dbh) of 1-2% (Swaine et al. 1987). There tends to be some degree of size-dependence to mortality, at least when viewed across the full range of sizes, with seedlings having higher mortality rates than mature trees. However, once above about 10 cm dbh mortality levels off markedly.

Only in large plots are sample sizes for most species big enough to make meaningful comparisons between species. At Barro Colorado Island, Panama, it has been found that mortality rates vary considerably between species (Fig. 3.1). Over the period 1985-1990, annual mortality for stems of 1099 mm dbh varied between zero in several species and 20% in Solanum hayesii (Condit et al. 1995). The modal mortality rates were 0.5-2.0 % (Fig. 3.1). The size dependence of mortality varied considerably between species (Fig. 3.2). Those with high mortality rates tended to show a strong increase in survivorship of individuals with size, whereas those with low overall mortality showed relatively little difference in survival between size classes.

Clark & Clark (1996) studied very large trees ( 70 cm dbh) on 150 ha at La Selva in Costa Rica. A total of 282 individuals in five species were monitored over six years. They represented only 2% of stems of 10 cm dbh or greater, but were 23% of stand basal area and 27% of its biomass. The mean annual mortality of the big trees was 0.6%, substantially lower than the average of 2.3% for all stems greater than 10 cm dbh.

Was this article helpful?

0 0
Disaster Preparedness Kit

Disaster Preparedness Kit

Don't get caught out in a disaster, be prepared for the unlikely. You just never know when disaster will strike, but if it does you will be more then prepared for it with the information this ebook gives you.

Get My Free Ebook


Post a comment