The effects of the rainy season and irrigation on soil water and oxygen in a seasonal forest in Panama

Kursar, Thomas A.; Wright, S. Joseph; Radulovich, Ricardo

doi:10.1017/s0266467400009044

Cited by 21 publications

(15 citation statements)

References 20 publications

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“…This is most hkely a result of differences in particle size distribution of clay and silt. However, greater precipitation may have affected the soil structure and increased water holding capacity, as observed in response to experimental irrigation on nearby Barro Colorado Island (Kursar et al 1995). Midday íZ/ieaf was lower at the 1,800-mm site than at the 3,100-mm site during the wet season but not during the dry season, despite strong differences in îZ'soii in the dry season, indicating that differences in atmospheric water content and stomatal function can affect îZ'ieaf independent of iZ/soii-Lack of a significant difference in predawn leaf water potential despite strong differences in ^soii during the dry season suggests high water-storage capacity (Goldstein et al 1998) or deep roots in dry forest species.…”

Section: Discussionmentioning

confidence: 99%

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Coordinated changes in photosynthesis, water relations and leaf nutritional traits of canopy trees along a precipitation gradient in lowland tropical forest

et al. 2004

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We investigated leaf physiological traits of dominant canopy trees in four lowland Panamanian forests with contrasting mean annual precipitation (1,800, 2,300, 3,100 and 3,500 mm). There was near complete turn-over of dominant canopy tree species among sites, resulting in greater dominance of evergreen species with long-lived leaves as precipitation increased. Mean structural and physiological traits changed along this gradient as predicted by cost-benefit theories of leaf life span. Nitrogen content per unit mass (Nmass) and light-and COa-saturated photosynthetic rates per unit mass (Pmass) of upper canopy leaves decreased with annual precipitation, and these changes were partially explained by increasing leaf thickness and decreasing specific leaf area (SLA). Comparison of 1,800 mm and 3,100 mm sites, where canopy access was available through the use of construction cranes, revealed an association among extended leaf longevity, greater structural defense, higher midday leaf water potential, and lower Pmass, N•iass, and SLA at wetter sites. Shorter leaf life spans and more enriched foliar 5 ^N values in drier sites suggest greater résorption and re-metabolism of leaf N in drier forest. Greater dominance of short-lived leaves with relatively high Pmass in drier sites reflects a strategy to maximize photosynthesis when water is available and to minimize water loss and respiration costs during rainless periods.

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Section: Discussionmentioning

confidence: 99%

“…Soils of the Panama Canal forests are well-drained clays high in Ca, Mg and N and low in K and P relative to other tropical soils (Dietrich et al 1982;Yavitt et al 1993;Kursar et al 1995). Three of the study sites are on volcanic substrate whereas the 3,100-mm site lies on sedimentary substrate.…”

Section: Site Characterization and Speciesmentioning

confidence: 99%

Coordinated changes in photosynthesis, water relations and leaf nutritional traits of canopy trees along a precipitation gradient in lowland tropical forest

et al. 2004

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“…Soils in this area tend to be well-drained (Kursar et al 1995), suggesting that low redox potential is not a strong factor in reducing plant productivity. A heterogeneous mosaic of geological formations constitutes the parent material of the Panama Canal watershed.…”

Section: Study Site and Water Availabilitymentioning

confidence: 98%

Leaf productivity along a precipitation gradient in lowland Panama: patterns from leaf to ecosystem

Santiago

Mulkey

2004

Trees

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Moisture availability has the potential to affect tropical forest productivity at scales ranging from leaf to ecosystem. We compared data for leaf photosynthetic, chemical and structural traits of canopy trees, litterfall production and seasonal availability of soil water at four sites across a precipitation gradient (1,800-3,500 mm year −1 ) in lowland Panamanian forest to determine how productivity at leaf and ecosystem scales may be related. We found stronger seasonality in soil water potential at drier sites. Values were close to zero at all sites during the wet season and varied between a minimum of −2.5 MPa and −0.3 MPa at the driest and wettest sites, respectively, during the dry season. Leaf photosynthesis and nitrogen concentration decreased with increasing precipitation, whereas leaf thickness increased with increasing precipitation. Leaf toughness and fiber/N ratios increased with increasing precipitation indicating reduced nutritional content and palatability with precipitation. Seasonality of litter production and quality decreased with increasing precipitation, but the amount of litterfall produced was not substantially different among sites. It appears that in Neotropical forest, moisture availability is associated with leaf photosynthetic and defensive traits that influence litterfall timing and quality. Therefore, variation in leaf physiological traits has the potential to influence decomposition and nutrient cycling through effects on litter quality.

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“…Drought-tolerant species could be at a disadvantage due to low soil oxygen in forests with higher rainfall. This seems unlikely, first, because the availability of oxygen in soil during the rainy season in a moist forest was quite high (Kursar et al 1995). In addition, species may not differ markedly in flooding tolerance (Lopez and Kursar 2003).…”

Section: Figmentioning

confidence: 99%

Pests vs. drought as determinants of plant distribution along a tropical rainfall gradient

Brenes-Arguedas

Coley

Kursar

2009

Ecology

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Abstract. Understanding the mechanisms that shape the distribution of organisms can help explain patterns of local and regional biodiversity and predict the susceptibility of communities to environmental change. In the species-rich tropics, a gradient in rainfall between wet evergreen and dry seasonal forests correlates with turnover of plant species. The strength of the dry season has previously been shown to correlate with species composition. Herbivores and pathogens (pests) have also been hypothesized to be important drivers of plant distribution, although empirical evidence is lacking. In this study we experimentally tested the existence of a gradient in pest pressure across a rainfall gradient in the Isthmus of Panama and measured the influence of pests relative to drought on species turnover. We established two common gardens on the dry and wet sides of the Isthmus using seedlings from 24 plant species with contrasting distributions along the Isthmus. By experimentally manipulating water availability and insect herbivore access, we showed that pests are not as strong a determinant of plant distributions as is seasonal drought. Seasonal drought in the dry site excluded wetdistribution species by significantly increasing their seedling mortality. Pathogen mortality and insect herbivore damage were both higher in the wet site, supporting the existence of a gradient in pest pressure. However, contrary to predictions, we found little evidence that drydistribution species suffered significantly more pest attack than wet-distribution species. Instead, we hypothesize that dry-distribution species are limited from colonizing wetter forests by their inherently slower growth rates imposed by drought adaptations. We conclude that mechanisms limiting the recruitment of dry-distribution species in wet forests are not nearly as strong as those limiting wet-distribution species from dry forests.

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The effects of the rainy season and irrigation on soil water and oxygen in a seasonal forest in Panama

Cited by 21 publications

References 20 publications

Coordinated changes in photosynthesis, water relations and leaf nutritional traits of canopy trees along a precipitation gradient in lowland tropical forest

Coordinated changes in photosynthesis, water relations and leaf nutritional traits of canopy trees along a precipitation gradient in lowland tropical forest

Leaf productivity along a precipitation gradient in lowland Panama: patterns from leaf to ecosystem

Pests vs. drought as determinants of plant distribution along a tropical rainfall gradient

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