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K. W. Krauss

Publications and source records attributed to K. W. Krauss.

24 records · Page 2Linked to original sources
USGS2003

Influences of salinity and shade on seedling photosynthesis and growth of two mangrove species, Rhizophora mangle and Bruguiera sexangula, introduced to Hawaii

Rhizophora mangle was first introduced to Hawaii in 1902 to promote shoreline stabilization. Intertidal competition with native and introduced salt marsh species was low, and beyond the early 1920s, mangrove forests expanded rapidly. An additional mangrove species, Bruguiera sexangula, was introduced in 1922 and currently co-occurs with R. mangle in only a few stands on the north shore and windward sides of Oahu. Where the two species overlap, R. mangle, having colonized intertidal zones first, forms nearly monospecific forest stands. To determine why R. mangle remains the dominant mangrove, we initiated a greenhouse study to compare seedling growth and photosynthetic light response of both species growing at two light levels and contrasting salinity regimes (2, 10, 32 PSU). The asymptotic nature of B. sexangula' s assimilation response is indicative of stomatal regulation, whereas only light level appears to regulate photosynthesis in R. mangle. Shifts in patterns of biomass allocation and physiological response indicate two contrasting strategies relative to sunlight and salinity. B. sexangula's strategy is characterized by slow growth with little variation under favorable conditions and morphological plasticity under stressful conditions, which allows for adjustments in carbon gain efficiency (morphological strategy). On the other hand, R. mangle's strategy involves faster growth under a wide range of environmental conditions with physiological enhancement of carbon assimilation (physiological strategy). Low salinity combined with reduced light, or simply low sunlight alone, appears to favor R. mangle and B. sexangula equally. High salinity places greater, but not overwhelming, stress on B. sexangula seedlings, but tends to favor R. mangle at higher light levels.

Aquatic Botany↗
USGS2003

Differential rates of vertical accretion and elevation change among aerial root types in Micronesian mangrove forests

Root systems in mangrove swamps have captured the attention of scientists for decades. Among the postulated roles of root structures include a contribution to the geomorphological stability of mangrove soils through sediment trapping and binding. In this study, we used feldspar marker horizons and sediment pins to investigate the influence of three different functional root types - prop roots in Rhizophora spp., root knees in Bruguiera gymnorrhiza, and pneumatophores in Sonneratia alba - on vertical accretion and elevation change in three mangrove forests in the Federated States of Micronesia. Prop roots facilitated vertical accretion (11.0 mm year-1) more than pneumatophores or bare soil controls (mean, 8.3 mm year-1). Sediment elevation, on the other hand, increased at an average rate of only 1.3 mm year-1 across all root types, with rate differences by root type, ranging from -0.2 to 3.4 mm year-1, being detected within river basins. This investigation demonstrates that prop roots can assist in the settling of suspended sediments from estuarine waters, yet prop root structures are not as successful as pneumatophores in maintaining sediment elevation over 2.5 years. As root densities increase over time, an increase in turbulence-induced erosion and in shallow subsidence as organic peat layers form is expected in Micronesian mangrove forests. ?? 2003 Elsevier Science B.V. All rights reserved.

Estuarine, Coastal and Shelf Science↗
USGS2003

Factors influencing the regeneration of the mangrove Bruguiera gymnorrhiza (L.) Lamk. on a tropical Pacific island

Mangrove swamps occupy approximately two-thirds of the shoreline on Kosrae, Federated States of Micronesia (FSM), and also border the island's most populated areas. Kosraeans depend on mangrove swamps for a supply of wood to support a growing handicraft industry, for a dependable source of fuelwood, and for habitat to support the harvest of fish and mangrove crabs. One of the more prominent mangrove species on Kosrae is Bruguiera gymnorrhiza, yet it is not the most preferred species for carving or cooking. To evaluate B. gymnorrhiza's persistence in the intertidal and to develop a better understanding of factors influencing its regeneration, we investigated predispersal insect colonization of propagules, postdispersal propagule predation by crabs, and the relative effects of natural and artificial shade, salinity, and tidal flooding on early tree seedling survival and growth. Predispersal insect colonization of propagules by boring insects was very high (93%), but the damage did not seem to influence seedling survival. Postdispersal predation of B. gymnorrhiza propagules by crabs was low (17%) and did not change in gap versus understory plots. Predation did vary by intertidal location (lower intertidal > middle intertidal = upper intertidal), with lower predation occurring in an intertidal location with a B. gymnorrhiza-dominated overstory. Shade and tidal inundation reduced seedling growth more than salinity in greenhouse investigations, but sunlight had less positive influence on seedling growth in the field. In general, regeneration and growth occurred successfully under a variety of conditions, indicating that none of the factors investigated serve as strong regulators to B. gymnorrhiza regeneration and early growth on Kosrae. ?? 2002 Elsevier Science B.V. All rights reserved.

Forest Ecology and Management↗
USGS2000

Growth and nutrition of baldcypress families planted under varying salinity regimes in Louisiana, USA

Saltwater intrusion from the Gulf of Mexico is one important factor in the destruction of baldcypress (Taxodium distichum (L.) Rich.) swamps along the Louisiana Gulf Coast, USA. Recent restoration efforts have focused on identification of baldcypress genotypes with greater tolerance to saline conditions than previously reported. To date, salt tolerance investigations have not been conducted under saline field conditions. In 1996, therefore, three plantations were established with 10 half-sib genotype collections of baldcypress in mesohaline wetlands. Tree survival and growth were measured at the end of two growing seasons, and foliar ion concentrations of Na, Cl, K, and Ca and available soil nutrients were measured during the 1996 growing season. In general, soil nutrient concentrations exceeded averages found in other baldcypress stands in the southeastern United States. Seedlings differed among sites in all parameters measured, with height, diameter, foliar biomass, and survival decreasing as site salinity increased. Average seedling height at the end of two years, for example, was 196.4 cm on the lowest salinity site and 121.6 cm on the highest. Several half-sib families maintained greater height growth increments (ranging from 25.5 to 54.5 cm on the highest salinity site), as well as lower foliar ion concentrations of K, Cl, and Ca. Results indicate that genotypic screening of baldcypress may improve growth and vigor of seedlings planted within wetlands impacted by saltwater intrusion.

Louisiana↗
USGS1999

Root and shoot responses of Taxodium distichum seedlings subjected to saline flooding

Variation among progeny of five half-sib family collections of baldcypress (Taxodium distichum) from three freshwater and two brackish-water seed sources subjected to saline flooding was evaluated Mini-rhizotrons (slant tubes) were used to monitor root elongation for a period of 99 days. Salinity level produced significant effects across all baldcypress half-sib families, with root elongation averaging 1594.0, 956.8, and 382.1 mm, respectively, for the 0, 4, and 6 g l-1 treatments. Combined mean root elongation for families from brackish-water seed sources was greater (1236.7 mm) than for families from freshwater seed sources (794.6 mm). Considerable variation occurred at the highest salinity treatment, however, with one freshwater family maintaining more than 28% more root growth than the average of the two brackish-water collections. Hence, results indicate that short-term evaluation of root elongation at these salinity concentrations may not be a reliable method for salt tolerance screening of baldcypress. Species-level effects for height and diameter, which were measured at day 62, were significant for both parameters. Height increment in the control (7.4 cm), for example, was approximately five times greater than height increment in the 6 g l-1 salinity treatment (1.5 cm). Family-level variation was significant only for diameter, which had an incremental range of 0.2 to 1.5 mm across all salinity levels.

Environmental and Experimental Botany↗