Tropical Montane Rain Forest Research Articles

Aboveground Adventitious Roots and Stemflow Chemistry of Ceratopetalum virchowii in an Australian Montane Tropical Rain Forest

Aboveground adventitious roots emerging from the stems and branches of the montane tropical rain forest canopy tree species, Ceratopetalum virchowii, do not require epiphyte mats to stimulate their growth. The adventitious roots grow in dense clumps on fully exposed aboveground woody surfaces of this species on Mount Bellenden Ker in northeast Queensland, Australia, where mean annual rainfall exceeds 6000 mm. While the soil at the study site is nutrient-poor, the nutrient content of the rainwater draining from the stems of C. virchowii is unusually high compared to the stemflow of other neighboring canopy tree species. Ceratopetalum virchowii is particularly prone to the leaching of Ca2+, Mg2+, K+, and Na+. The aboveground adventitious roots of C. virchowii, therefore, may serve the adaptive function of nutrient recovery before its nutrient-rich stemflow reaches the ground and becomes available to other plants. I hypothesize that the growth of the aboveground adventitious roots of C. virchowii is influenced by the high nutrient content of its stemflow and branchflow drainage, and by the moist condition of its woody surfaces which remain wetted for relatively long periods after rainfalls.

Litterfall and nutrient fluxes in two montane tropical rain forests, Colombia

ABSTRACTLitterfall was sampled during one year in two undisturbed Andean forests at altitudes of 2550 and 3370 m in the Colombian Cordillera Central. Total small litterfall at 2550 and 3370 m was 7.03 and 4.31 tha-1y-1respectively, of which 4.61 and 2.82 were leaves, 1.06 and 0.76 woody parts, 0.66 and 0.27 reproductive parts, 0.22 and 0.23 epiphytes, 0.47 and 0.23 unclassified.Clear differences were also found in nutrient concentrations, both between different litter fractions from one site and between equivalent litter fractions from different sites. Weighted mean concentrations for total small litterfall were (mgg-1, at 2550 and 3370m respectively): 11.7 and 7.3 for nitrogen; 0.86 and 0.44 for phosphorus; 8.4 and 3.1 for potassium. Comparison of nutrient concentrations in crown leaves and shed leaves indicated important reallocation of nitrogen (39% at both sites) and phosphorus (45% at 2550m, 65% at 3370m) before leaf shedding.The results for litterfall amounts, litter nutrient concentrations and reallocation of nutrients in the two forests are consistent with such data obtained in other montane forests in the wet tropics.

Pollination of Four Sumatran Impatiens Species by Hawkmoths and Bees.

Flowering patterns and pollination syndromes were compared among four sympatric Impatiens species (Balsaminaceae) in tropical montane rain forests in Sumatra, Indonesia. Pink flowers with long filiform spurs of I. platypetala produced nectar of 26 % sugar both in the daytime and at night and were po11inated by crepuscular hawkmoths, Macroglossum corythus. Yellow flowers with gradually tapering spurs of I. korthalsii, I. talangensis and I. eubotrya produced nectar of 34-39 % sugar, mainly in the daytime, and were po11inated by two specialized long-tongued anthophorid bees and an unusually long-tongued halictid bee. Spur morphology essentially determined nectar accessibility. Although the three Impatiens species partially shared the three bee species, they partitioned their po11inators by differing in sites of pollen deposition on the bee's bodies. The low po11inator visitation rates per day were compensated by the extended flowering period of the four species. Nectar robbing by two anthophorid bee species was observed, for the first time in Southeast Asia.

Nutrient Fluxes in Bulk Precipitation and Throughfall in Two Montane Tropical Rain Forests, Colombia

(1) The composition of bulk precipitation (rainfall plus dry deposition as collected by funnels) and throughfall water was studied during one year on a weekly basis in two epiphyte-rich Andean rain forests (Cordillera Central, Colombia, 2550 and 3370 m a.s.l.) (2) Nutrient input to the forest by bulk precipitation was higher at 2550 m because of larger precipitation volumes; rainfall was 2115 mm at 2550 m and 1453 mm at 3370 m. Losses of nutrients from the canopy, both total amounts and amounts per unit of precipitation, were also higher at 2550 m. (3) Net fluxes (throughfall flux minus bulk precipitation flux) and deposition ratios (ratio of throughfall flux to bulk prec;pitation flux) were generally within the range reported for other montane tropical rain forests. Differences between forests appear to be related to climate (mainly precipitation amounts), geographical situation (e.g. maritime influences) and the availability of nutrients in the soil. The patterns described in the present study are in accordance with other studies that show reduced cycling rates and limited availability of nitrogen and phosphorus in high-altitude rain forests. (4) Volcanic activity in the proximity of the forests (continuous SO2 emission and incidental ash-falls) was shown to affect precipitation chemistry. Inputs of S04-S were high (26 2 and 16 8 kg ha-' year' at 2550 and 3370 m, respectively) and correlated with rainfall acidity. As a consequence of an ash-fall, concentrations of Ca, Mg and S04-S in bulk precipitation were far above average on one occasion. Throughfall concentrations fell to normal within two to three weeks in spite of low rainfall.

Rainfall interception in two tropical montane rain forests, Colombia

AbstractRainfall interception was studied during one complete year in two montane rain forests in the Colombian Andes at altitudes of 2550 and 3370 m. Additional measurements were made in a subsequent period at 3370 m, comparing two plots with different tree genera. Special attention was paid to the possible consequences of the abundant epiphytic vegetation, representing a high but spatially variable storage capacity. On an annual basis, interception amounted to 262 mm (12.4 per cent) of 2115 mm incident precipitation at 2550 m, and to 265 mm (18.3 per cent) of 1453 mm incident precipitation at 3370 m. There was no evidence for fog precipitation. The fact that, in spite of lower annual rainfall and lower evaporation rate, absolute quantity of interception at 3370 m was not lower than at 2550 m is probably related to differences in rainfall distribution and canopy storage capacities. The different responses of the two tree genera (characterized by distinct epiphyte cover) and the lower interception after prolonged wet periods support the idea that epiphytes play a significant role in the interception process. A realistic description of the water balance of such ecosystems will require the adaptation of existing interception models.

Hydrological properties of the epiphyte mass of a montane tropical rain forest, Colombia

The effect of a well-developed epiphytic vegetation on the interception of rainfall was investigated in an upper montane rain forest at an altitude of 3370 m in the Cordillera Central of the Colombian Andes. Total epiphyte mass was estimated at 12 tonnes dry weight per hectare, most of it being bryophytes and dead organic matter. The hydrological properties of the epiphyte mass were studied using detached branches. Water gain (during rainfall) and water loss (after experimental saturation) were determined gravimetrically in the field. Rain falling on epiphyte-covered branches was efficiently captured. Drainage of water (held temporarily in excess of the retention capacity) was very gradual. Water loss through evaporation was slow. The observations are in accordance with previously reported data for rainfall interception in the forest studied. The potentially large influence of the exceptionally high canopy storage capacity is restricted due to the clumped distribution of epiphytes and associated low turnover rates of water in the epiphyte mass.

Canopy gaps and light penetration into a wind-exposed tropical lower montane rain forest

Penetration of light into the understory of tropical lower montane rain forests at Monteverde, Costa Rica, depends largely on the nature of canopy disruption by limb fall and tree fall. Midday photosynthetic photon flux densities (PPFD) above the forest canopy are low because of cloud cover (modal values are 400–500 μmol•m−2•s−1; daily integrations are 19 mol•m−2). The proportion of above-canopy PPFD that penetrates to the understory is greater in the elfin forests on wind-exposed ridge crests than in taller cloud forests in protected ravines (39 and 54% of understory locations receive <2% PPFD, respectively). PPFD is higher, and its vertical gradients steeper, in elfin forest gaps than in gaps of the same area in the taller forest. Gaps may or may not influence PPFD in adjacent forest understory, depending on vegetation structure on the gap periphery. In the taller cloud forest, understory PPFD is not correlated with distance to the nearest gap, but in the elfin forest it is (r = −0.467). This variation in the light environment is an integral part of disturbance and regrowth in these forests and seems to have played a major role in the evolution of tree growth strategies.

Light environments within montane tropical rainforest, Mt Bellenden Ker, North Queensland

AbstractIrradiance and photosynthetic photon flux density (PPFD) at five sites within a montane tropical rainforest were compared to test for differences among characteristic environments within the same forest type. The five habitats investigated were a large clearing (800 m2). a small gap (150 m2), the lower canopy, and two shaded understorey sites. Daily average irradiance ranged from 32.3 W m‐2 in the heavily shaded understorey to over 400 W m‐2 in the large clearing. Similarly, daily average PPFD ranged from 10.2 to over 800 μmol m‐2 s‐1 at corresponding sites, respectively. Daily total irradiation in the understorey, small gap, and lower canopy were 7.9–8.8%, 11.8% and 11.5%, respectively, of irradiation in the large clearing. For daily total PPFD, relative values for the same sites were 1.3–3.8%, 6.0% and 10.3%, respectively. Comparisons of frequency distributions for irradiance showed that the only significant difference was between the large clearing and the four forest sites. Comparisons of frequency distributions for PPFD showed significant differences among all five sites. Median PPFDs were always above the range of known light compensation points for rainforest plants even in the heavily shaded understorey, and usually above the known light saturation levels of canopy members. These results indicate that the reduction in PPFD by cloud cover does not limit the rates of photosynthesis.

CURVATURE OF WOODY PLANTS ON SLOPES OF A TIMBERLINE MONTANE FOREST IN PERU

Measurements of above and below-ground portions of woody plants ≤ m in height were made along a transect on a 31 ´ slope in tropical montane rain forest near treeline in northern Peru. Almost all stems were basally curved, and most of the belowground axes were curved and situated upslope relative to the stem base. Microscopic examination demonstrated that underground curvature, and the resulting aboveground basal stem curvature, was due to stem burial, followed by adventitious rooting. We suggest that it was litter creep and branch movements along the slope that caused this burial. A threshold model would best explain how and when these curvatures occur: plant form and growth will only be affected by soil creep and other noncatastrophic downslope forces when the plant is within critical size classes of stem diameter and rooting depth. [Key words: geomorphic processes, Peru, soil creep, tropical montane forest.]

Wood Specific Gravity Gradients in Tropical Dry and Montane Rain Forest Trees

Wood Specific Gravity Gradients in Tropical Dry and Montane Rain Forest Trees

Changes in Soil Nitrogen-Mineralization and Nitrification Along an Altitudinal Transect in Tropical Rain Forest in Costa Rica

(1) Surface soils (0-15 cm) were collected from six sites in mature undisturbed tropical rain forest along an altitudinal transect (100 m-2600 m) on Volcan Barva, Costa Rica. The rates of nitrogen-mineralization and nitrification were measured under (a) field conditions, where the soils were incubated under the litter layer, and (b) laboratory conditions, where the incubations were done at higher temperatures, but at field moisture content. In addition, a measure of nitrogen-mineralization was made under 'improved' conditions, where the incubation temperature was increased, and aeration and moisture content improved. The moisture content, pH and the concentrations of a range of soil nutrients were also measured for each soil. A nutrient amendment experiment was also done, where selected nutrients were added to soils from three altitudes (100 m, 1000 m and 2600 m), and their effect on nitrogen mineralization and nitrification assessed. (2) The moisture content, total nitrogen and carbon, extractable potassium, calcium, magnesium and ammonium-nitrogen increased, and both extractable copper and nitratenitrogen decreased, with altitude. (3) Soil nitrogen-mineralization and nitrification both decreased with increasing altitude under field conditions, and both rates were not increased significantly by laboratory incubation, where the temperature alone was alleviated. However, where both temperature and aeration/moisture content were improved, then nitrogen-mineralization rate increased by between one and three orders of magnitude, and a positive relationship was found with altitude of origin. These combined results suggest that nitrogenmineralization may be limited under field conditions by the high moisture contents found in the montane soils. (4) Partial correlation analysis of these nitrogen turnover rates with other measures of soil chemistry showed that (a) under 'improved' conditions the mineralization rate was positively correlated with resource quality and negatively correlated with pH and perhaps reducing conditions, (b) under field and laboratory conditions the mineralization rate was correlated with the reaction product, and (c) nitrification was correlated with the reaction substrate, implying a resource limitation. (5) In the nutrient-addition experiment, ammonium-nitrogen increased nitrogenmineralization rates at low and high altitudes, but decreased rates at the intermediate altitude. Calcium carbonate addition increased mineralization rates at the low and intermediate altitude, whereas calcium sulphate increased these rates only at the highest altitude. Phosphorus addition had no effect on nitrogen-mineralization at any altitude. (6) Nitrification rates were increased by substrate addition, confirming that the reaction was substrate limited. However, the stimulation was much less than the amount of added substrate, and other limiting factors are clearly important. Calcium sulphate also increased nitrification, but only at the lowest altitude. (7) These findings agree with the general hypothesis that nitrogen-mineralization and nitrification rates are reduced in montane tropical rain forest, and may be a contributory factor controlling growth, species composition and stand structure. The significance of these results for future management of montane tropical rain forest is briefly discussed.

On Limits to Seed Production

On Limits to Seed Production

Early tertiary Tmesipteris (Psilotaceae) macrofossil from Tasmania

The discovery of a fossil Tmesipteris specimen from the Late Eocene–Oligocene Cethana deposit is the first macrofossil record of the Psilotaceae. The specimen is represented by a portion of an areial shoot and is assigned to the new species, T. tasmanica. Extant species are virtually confined to ever-wet temperature and tropical montane rainforests of Australiasia, eastern Malesia and islands of the Pacific. The discovery therefore provides an identification that the Cethana deposit was surrounded by vegetation which grew in cool and humid conditions.

Episodic stemflow inputs of magnesium and potassium to a tropical forest floor during heavy rainfall events.

Stemflow inputs of magnesium and potassium were measured from 57 canopy trees representing eight species under heavy rainfall conditions in two tropical forest sites in northeast Queensland, Australia. In the premontane tropical moist forest site on the Atherton Tableland, the stemflow input per unit trunk basal area of 51 canopy trees was found to be 0.46 g m-2 of Mg2+ and 4.22 g m-2 of K+ for an average wet season rainday of 99 mm. In the wetter montane tropical rainforest site on Mount Bellenden Ker, the stemflow input per unit trunk basal area of six canopy trees was 5.55 g m-2 of Mg2+ and 9.12 g m-2 of K+ for a wet season rainday of 38 mm. These stemflow inputs from single raindays are greater than the mean annual rainfall input and are almost of the same order of magnitude as the mean annual throughfall input of these cations to areas equal to the trunk basal area from which the stemflow was collected. Stemflow cation fluxes of this magnitude are mainly attributable to the funnelling of large quantities of rainwater down the trunks of these canopy trees by their thoroughly wetted, upwardly inclined branches.

A new species of phlebotomine sand fly (Diptera: Psychodidae) from Guatemala.

Lutzomyia guatemalensis is a new species of phlebotomine sand fly from tropical lower montane rain forests in Guatemala; it appears to be most closely related to the species of the L. shannoni group. Unlike other species in this group, the antennal ascoids of L. guatemalensis have a short posterior spur with an acute tip. The spermathecal capsule is finely annulated. The size of several morphologic characters differed significantly (P < 0.5) between males and females. The most pronounced differences (P < 0.001) were in head height, interocular space, clypeus, labrum, pharynx, maxillary palpomeres 1+2, maxillary palpomere 3, wing width, and antealar setae.

Jamaican Montane Forests: Nutrient Capital and Cost of Growth

(1) Concentrations of N, P, K, Ca and Mg were measured in the biomass of two 10 x 10 m plots at about 1550 m altitude in the Jamaican mountains: one in Mor Ridge forest and one in well-developed Mull Ridge forest. (2) Arithmetic mean concentrations in leaf and composite stem samples in Mor Ridge forest were, respectively (in mg g-D), N, 11.1, 2.0; P, 0 64, 0.15; K, 4.3, 1.6; Ca, 8.0, 1.9; Mg, 3.3, 0.80. The corresponding concentrations for well-developed Mull Ridge forest were N, 17 8, 3.1; P, 0.76, 0 13; K, 11.7, 3.1; Ca, 10.0, 3.0; Mg, 4.6, 0.61. Concentrations calculated by dividing the total weight of an element by the biomass dry weight were lower than arithmetic means in every case. (3) Concentrations per unit area (kg ha-') and (in parentheses) per unit dry weight (mg g-1) of above-ground standing crop were lower in the lower stature, slower growing Mor Ridge forest: N, 426 (2.0); P, 29.7 (0.14); K, 272 (1.3); Ca, 353 (1.7); Mg, 155 (0.74) than in the well-developed Mull Ridge forest: N, 857 (2-5); P, 41.2 (0-12); K, 829 (2.5); Ca, 940 (2.8); Mg, 193 (0-57). (4) First estimates of the amounts of nutrients used in trunk growth in the Mor Ridge forest each year are 1.9% of extractable soil N (NO3 + NH4), 0.4% of exchangeable soil K, 2.3% of exchangeable soil Ca and 0.08% of exchangeable soil Mg. For well-developed Mull Ridge forest the corresponding values are N, 2.0%; K, 1.2%; Ca, 1. 1%; Mg, 0.3%. (5) The impoverishment of the Mor Ridge forest compared to the well-developed Mull Ridge forest is probably due to the limitation of growth by the supply of N and K, and possibly by P and Ca. (6) The impoverishment of the Jamaican Upper Montane Rain forest compared to better-developed Montane Rain forests at higher altitudes on larger mountains is probably not a result of poor supply of N, K, Ca or Mg, though the role of P is still not clear. (7) Tropical montane rain forests in general may be short of N, P, K and Ca compared to the most nutrient-rich tropical lowland rain forests.

Ecological Constraints on Wood Density in a Tropical Montane Rain Forest

Ecological Constraints on Wood Density in a Tropical Montane Rain Forest

Nitrogen Fixing Lichen Roles from Desert to Alpine in the Sangre de Cristo Mountains, New Mexico

Nitrogen Fixing Lichen Roles from Desert to Alpine in the Sangre de Cristo Mountains, New Mexico