Tree roots can penetrate deeply in African semi-deciduous rain forests: evidence from two common soil types

2014 ◽  
Vol 31 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Vincent Freycon ◽  
Christelle Wonkam ◽  
Adeline Fayolle ◽  
Jean-Paul Laclau ◽  
Eric Lucot ◽  
...  
Keyword(s):  
Root Distribution ◽  
Soil Surface ◽  
Dry Season ◽  
Distribution Model ◽  
Root Penetration ◽  
Tropical Rain Forests ◽  
Rain Forests ◽  
Tree Roots ◽  
Sampling Depth ◽  
Deep Roots

Abstract:Despite the important functional role of deep roots in withdrawing water during drought, direct measurements of root distribution are very rare in tropical rain forests. The aim of this study was to investigate the root distribution of Entandrophragma cylindricum, a common tree species in the Central African semi-deciduous rain forest, in Ferralsols and Arenosols. We dug two pits to a depth of 6 m in Ferralsols and two pits to a depth of 3 m in Arenosols, close to E. cylindricum trees. The vertical soil profiles were divided into 10 × 10-cm grid cells and the roots counted were distributed in three diameter classes. We fitted a root distribution model to our dataset. We found that vertical root distribution was shallower in Arenosols than in Ferralsols. Root penetration was not stopped even by a Ferralsol with high gravel content in its subsoil. Overall, our measurements showed that 95% of all roots were distributed to depths of between 258 and 564 cm from the soil surface, which is much deeper than the 95 cm depth previously reported in the literature for tropical rain forests. As sampling depth could explain this discrepancy, we recommend a sampling depth of at least 3–5 m to accurately estimate root distribution. The drier the dry season, the deeper the sampling depth should be. Our results are consistent with global models of root distribution in forest ecosystems, which are driven by climate variables. We thus suggest that deep rooting could be common in rain forests with a marked dry season.

Response of tree roots to decomposing organic matter in two lowland Amazonian rain forests

1983 ◽  
Vol 13 (2) ◽  
pp. 346-349 ◽  
Author(s):  
T. V. St. John
Keyword(s):  
Organic Matter ◽  
Experimental Evidence ◽  
Dynamic Process ◽  
Fine Roots ◽  
Soil Surface ◽  
Tropical Rain Forests ◽  
Rain Forests ◽  
Tree Roots ◽  
Soil Volume

Fine roots of tropical rain forests are sometimes associated with decomposing organic matter at the soil surface. This association is considered by some authors to be important in recovery of nutrients by the vegetation. In this paper, experimental evidence is presented to show that the association results from a dynamic process and is not a coincidental result of negative geotropism. The association appears to be the result of random encounters of growing roots with organic matter, followed by increased branching at that site. The concentration of absorbing tissue in such relatively nutrient-rich sites as decomposing organic matter implies more effective ion absorbtion than would result if roots were randomly distributed in the soil volume.

Temporal and spatial variation of fine roots in a northern Australian Eucalyptus tetrodonta savanna

2008 ◽  
Vol 24 (2) ◽  
pp. 177-188 ◽  
Author(s):  
David P. Janos ◽  
John Scott ◽  
David M. J. S. Bowman
Keyword(s):  
Fine Roots ◽  
Soil Surface ◽  
Dry Season ◽  
Annual Rainfall ◽  
Tropical Savannas ◽  
Wet Season ◽  
Temporal And Spatial Variation ◽  
Deep Roots ◽  
Temporal And Spatial ◽  
Peak Abundance

Abstract:Six rhizotrons in an Eucalyptus tetrodonta savanna revealed seasonal changes in the abundance of fine roots (≤ 5 mm diameter). Fine roots were almost completely absent from the upper 1 m of soil during the dry season, but proliferated after the onset of wet-season rains. At peak abundance of 3.9 kg m−2 soil surface, fine roots were distributed relatively uniformly throughout 1 m depth, in contrast with many tropical savannas and tropical dry forests in which fine roots are most abundant near the soil surface. After 98% of cumulative annual rainfall had been received, fine roots began to disappear rapidly, such that 76 d later, less than 5.8% of peak abundance remained. The scarcity of fine roots in the upper 1 m of soil early in the dry season suggests that evergreen trees may be able to extract water from below 1 m throughout the dry season. Persistent deep roots together with abundant fine roots in the upper 1 m of soil during the wet season constitute a ‘dual’ root system. Deep roots might buffer atmospheric CO2 against increase by sequestering carbon at depth in the soil.

Termites facilitate root foraging by trees in a Bornean tropical forest

2013 ◽  
Vol 29 (6) ◽  
pp. 563-566 ◽  
Author(s):  
Mingzhen Lu ◽  
Mircea Davidescu ◽  
Rahayu Sukmaria Sukri ◽  
Joshua H. Daskin
Keyword(s):  
Nutrient Cycling ◽  
Tropical Forest ◽  
Late Stage ◽  
Root Colonization ◽  
Soil Surface ◽  
Tropical Rain Forests ◽  
Rain Forests ◽  
Dead Tree ◽  
Root Foraging ◽  
Physical Barriers

Abstract:Plants can develop novel adaptations for nutrient acquisition in nutrient-limited ecosystems. These adaptations include colonization by roots of tree trunks and logs that can act as nutrient reservoirs. Termites may facilitate this root colonization by digging tunnels and accelerating decomposition in logs and tree trunks. We measured the frequency with which above-ground tree root colonization co-occurs with the presence of termites or their tunnels inside living trees above 20 cm dbh (n = 178) and dead tree trunks and logs at least 15 cm in diameter (n = 146) in a Bornean tropical forest. Roots above the soil surface co-occur with termite tunnels 39% more frequently than expected by chance in trunks of living trees and 17% more frequently than expected by chance in logs. By categorizing logs according to hardness through ease of penetration, we found that softer logs at a late stage of decay did not show co-occurrence of termite activity and roots to the same extent as harder logs. This suggests that trees forage where termites have removed physical barriers to colonization. In this fashion, termites may accelerate nutrient cycling in tropical rain forests.

Ants accelerate litter decomposition in a Costa Rican lowland tropical rain forest

2012 ◽  
Vol 28 (5) ◽  
pp. 437-443 ◽  
Author(s):  
Terrence P. McGlynn ◽  
Evan K. Poirson
Keyword(s):  
Mass Loss ◽  
Leaf Litter ◽  
Litter Decomposition ◽  
Rain Forest ◽  
Costa Rican ◽  
Tropical Rain Forests ◽  
Rain Forests ◽  
Food Web Structure ◽  
Litter Bags ◽  
Lowland Rain Forest

Abstract:The decomposition of leaf litter is governed, in part, by litter invertebrates. In tropical rain forests, ants are dominant predators in the leaf litter and may alter litter decomposition through the action of a top-down control of food web structure. The role of ants in litter decomposition was investigated in a Costa Rican lowland rain forest with two experiments. In a mesocosm experiment, we manipulated ant presence in 50 ambient leaf-litter mesocosms. In a litterbag gradient experiment, Cecropia obtusifolia litter was used to measure decomposition rate constants across gradients in nutrients, ant density and richness, with 27 separate litterbag treatments for total arthropod exclusion or partial arthropod exclusion. After 2 mo, mass loss in mesocosms containing ants was 30.9%, significantly greater than the 23.5% mass loss in mesocosms without ants. In the litter bags with all arthropods excluded, decomposition was best accounted by the carbon: phosphorus content of soil (r2 = 0.41). In litter bags permitting smaller arthropods but excluding ants, decomposition was best explained by the local biomass of ants in the vicinity of the litter bags (r2 = 0.50). Once the microarthropod prey of ants are permitted to enter litterbags, the biomass of ants near the litterbags overtakes soil chemistry as the regulator of decomposition. In concert, these results support a working hypothesis that litter-dwelling ants are responsible for accelerating litter decomposition in lowland tropical rain forests.

scholarly journals Resilience of tropical rain forests: tree community reassembly in secondary forests

2009 ◽  
Vol 12 (5) ◽  
pp. 385-394 ◽  
Author(s):  
Natalia Norden ◽  
Robin L. Chazdon ◽  
Anne Chao ◽  
Yi-Huei Jiang ◽  
Braulio Vílchez-Alvarado
Keyword(s):  
Secondary Forests ◽  
Tropical Rain Forests ◽  
Rain Forests ◽  
Tree Community ◽  
Community Reassembly

Resource allocation to reproductive organs during masting in the tropical emergent tree, Dipterocarpus tempehes

2005 ◽  
Vol 21 (2) ◽  
pp. 237-241 ◽  
Author(s):  
Tomoaki Ichie ◽  
Tanaka Kenta ◽  
Michiko Nakagawa ◽  
Kaori Sato ◽  
Tohru Nakashizuka
Keyword(s):  
Forest Ecosystems ◽  
Reproductive Organs ◽  
Nutrient Cycle ◽  
South East Asia ◽  
Tropical Rain Forests ◽  
Rain Forests ◽  
Mass Flowering ◽  
Animal Populations ◽  
Dipterocarp Forests ◽  
Interspecific Synchronization

Some tree species exhibit large year-to-year variation in seed production, a phenomenon known as masting (Kelly 1994, Kelly & Sork 2002). Even in tropical rain forests, in which the climate is suitable for plant growth all year round with little seasonal variation (Whitmore 1998), there are many reports of masting (Appanah 1993, Hart 1995, Newbery et al. 1998, Newstrom et al. 1994, Wheelwright 1986). In particular, Dipterocarpaceae, the dominant family in lowland mixed dipterocarp forests in South-East Asia, undergo mast fruiting following mass-flowering with strong interspecific synchronization in aseasonal western Malesia (Appanah 1985, 1993; Ashton 1989, Ashton et al. 1988, Curran et al. 1999, Janzen 1974, Medway 1972, Sakai et al. 1999, Whitmore 1998, Wood 1956). In mixed-dipterocarp forests, dipterocarp species contribute more than 70% of the canopy biomass (Bruenig 1996, Curran & Leighton 2000). Masting of dipterocarp species is therefore likely to have a major impact on animal populations, and also on the nutrient cycle in such forest ecosystems by causing fluctuations in the availability of resources (Sakai 2002).

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