Robin A. Harrington

Bio: Robin A. Harrington is an academic researcher from University of Hawaii at Manoa. The author has contributed to research in topics: Leaf area index & Canopy. The author has an hindex of 10, co-authored 11 publications receiving 854 citations. Previous affiliations of Robin A. Harrington include University of Hawaii & University of Wisconsin-Madison.

Production and Resource Use Efficiencies in N- and P-Limited Tropical Forests: A Comparison of Responses to Long-term Fertilization

Abstract: At two sites at the extreme ends of a soil development chronosequence in Hawaii, we investigated whether forest responses to fertilization on young soils were similar to those on highly weathered soils and whether the initial responses were maintained after 6–11 years of fertilization. Aboveground net primary production (ANPP) was increased by nitrogen (N) application at the 300-year-old site and phosphorus (P) application at the 4.1-million-year-old site, thus confirming earlier results and their designations as N- and P-limited forests. Along with ANPP, application of the limiting element consistently increased leaf area index (LAI), radiation conversion efficiency (RCE), and foliar and litter nutrient concentrations. Fertilization did not consistently alter N or P retranslocation from senescent leaves at either site, but a comparison with other sites on the chronosequence and with a common-garden study suggests that there is a genetic basis for low foliar and litter nutrients and higher retranslocation at infertile sites vs more fertile sites. N limitation appears to be expressed as limitation to carbon gain, with long leaf lifespans and high leaf mass per area. P limitation results in high P-use efficiency and disproportionally large increases in P uptake after fertilization; a comparison with other studies indicates large investments in acquiring and storing P. Although the general responses of ANPP, LAI, and RCE were similar for the two sites, other aspects of nutrient use differ in relation to the physiological and biogeochemical roles of the two elements.

Ecophysiology of exotic and native shrubs in Southern Wisconsin : I. Relationship of leaf characteristics, resource availability, and phenology to seasonal patterns of carbon gain.

Abstract: We compared seasonal trends in photosynthesis of two naturalized exotic shrubs (Rhamnus cathartica and Lonicera X bella) and two native shrubs (Cornus racemosa and Prunus serotina) in open and understory habitats in southern Wisconsin. We examined the relationships between resource availability and leaf photosynthetic performance in these four species. All four species had similar relationships between leaf nitrogen (N) content and photosynthetic rate, but the species differed in absolute leaf N content and therefore in photosynthetic rates. Maximum daily photosynthetic rates of all species were significantly correlated with leaf N content in the open habitat, but not in the understory, where low light availability was the major limitation to photosynthesis. Extended leaf longevity was important in the forest understory because it allowed shrubs to take advantage of high light availability at times when the overstory canopy was leafless. Early leaf emergence was more important than late senescence: from 27% to 35% of the annual carbon gain of P. serotina, R. cathartica, and L. X bella occurred prior to leaf emergence of C. racemosa, the species with the shortest leaf life span. Extended leaf longevity of exotic shrubs may help explain their persistence in the understory habitat, but it contributed relatively less to their annual carbon gain in the open habitat.

Ecophysiology of exotic and native shrubs in Southern Wisconsin : II. Annual growth and carbon gain.

Abstract: In this study we compared the aboveground growth rates of two exotic shrubs (Rhamnus cathartica and Lonicera X bella) and two native shrubs (Cornus racemosa and Prunus serotina) that are important in southern Wisconsin hardwood forests. For all species except P. serotina, aboveground growth rates in an open habitat were greater than in an understory environment. Growth rates differed among species in the open habitat and were significantly correlated with woody production per unit leaf area. All species had greater leaf area per unit wood biomass in the understory than in the open habitat. A comparison of above-ground growth and annual carbon gain suggests much greater respiratory costs in the open habitat, especially for P. serotina. The data from this study were used to examine mechanisms of species response to different light availabilities. We found that the species that increased their production per unit leaf area in response to increased light did not increase their leaf area per unit wood biomass in response to low light, and vice versa. Production of proportionately high leaf area may be important for the growth of C. racemosa in low light.

Forest growth along a rainfall gradient in Hawaii: Acacia koa stand structure, productivity, foliar nutrients, and water- and nutrient-use efficiencies

Abstract: We tested whether variation in growth of native koa (Acacia koa) forest along a rainfall gradient was attributable to differences in leaf area index (LAI) or to differences in physiological performance per unit of leaf area Koa stands were studied on western Kauai prior to Hurricane Iniki, and ranged from 500 to 1130 m elevation and from 850 to 1800 mm annual precipitation Koa stands along the gradient had basal area ranging from 8 to 42 m2/ha, LAI ranging from 14 to 54, and wood increment ranging from 07 to 71 tonnes/ha/year N, P, and K contents by weight of sun leaves (phyllodes) were negatively correlated with specific leaf mass (SLM, g m-2) across sites; on a leaf area basis, N increased whereas P and K decreased with SLM LAI, aboveground woody biomass increment, and production per unit leaf area (E) increased as phyllode δ13C became more negative The δ13C data suggested that intrinsic water-use efficiency (ratio of assimilation to conductance) increased as water availability decreased In five of the six sites, phyllode P contents increased as LAI increased, but biomass increment and E were not correlated with phyllode nutrient contents, suggesting that productivity was limited more by water than by nutrient availability Because vapor pressure deficits increased with decreasing elevation, actual water-use efficiency (ratio of assimilation to transpiration) was lower at drier, low-elevation sites There was a trade-off between intrinsic water-use efficiency and production per unit of canopy N or P across the gradient In summary, koa responds to water limitation both by reducing stand LAI and by adjusting gas exchange, which results in increased intrinsic water-use efficiency but decreased E

The effect of environmentally induced stem temperature gradients on transpiration estimates from the heat balance method in two tropical woody species.

Abstract: Commercially available sap flow gauges were used to evaluate the performance of the stem heat balance (SHB) technique for measuring sap flow in coffee (Coffea arabica L. cv. Yellow Catuai) and koa (Acacia koa Gray) plants under greenhouse and field conditions. Transpiration rates measured gravimetrically and with the SHB technique were similar in greenhouse tests, provided that insulation in addition to that supplied by the gauge manufacturer was applied to reduce radiant heating in the vicinity of the sap flow gauges. Unrealistic estimates of transpiration rates were sometimes obtained under both field and greenhouse conditions as a result of negative stem temperature differentials from below to above the gauge heater, even in the absence of power applied to the heaters. It was possible to correct this environmentally induced bias by means of additional stem insulation that minimized the rate of change in stem temperature, or by applying simple corrections using the DeltaT values for unheated gauges operated as blanks. In the field, where dense canopies reduced the radiant energy load on stems, temperature corrections were unnecessary, because DeltaT values in unheated gauges were near zero.

Terrestrial phosphorus limitation: mechanisms, implications, and nitrogen–phosphorus interactions

Abstract: Nutrient limitation to primary productivity and other biological processes is widespread in terrestrial ecosystems, and nitrogen (N) and phosphorus (P) are the most common limiting elements, both individually and in combination. Mechanisms that drive P limitation, and their interactions with the N cycle, have received less attention than mechanisms causing N limitation. We identify and discuss six mechanisms that could drive P limitation in terrestrial ecosystems. The best known of these is depletion-driven limitation, in which accumulated P losses during long-term soil and ecosystem development contribute to what Walker and Syers termed a "terminal steady state" of profound P depletion and limitation. The other mechanisms are soil barriers that prevent access to P; transactional limitation, in which weathering of P-containing minerals does not keep pace with the supply of other resources; low-P parent materials; P sinks; and anthropogenic changes that increase the supply of other resources (often N) relative to P. We distinguish proximate nutrient limitation (which occurs where additions of a nutrient stimulate biological processes, especially productivity) from ultimate nutrient limitation (where additions of a nutrient can transform ecosystems). Of the mechanisms that drive P limitation, we suggest that depletion, soil barriers, and low-P parent material often cause ultimate limitation because they control the ecosystem mass balance of P. Similarly, demand-independent losses and constraints to N fixation can control the ecosystem-level mass balance of N and cause it to be an ultimate limiting nutrient.

Hydraulic Limits to Tree Height and Tree Growth

Abstract: Examines what determines the height to which a tree will grow in a particular region and climate. The relationship between maximum tree height and the speed at which the tree grew when young; Mechanisms for growth including the respiration hypothesis, the nutrient limitation hypothesis, the maturation hypothesis and the hydraulic limitation hypothesis; Details about each hypothesis; Evidence for hydraulic limitation; Conclusions.

Scaling of c:n:p stoichiometry in forests worldwide: implications of terrestrial redfield‐type ratios

Abstract: Inspired by the importance of globally well-constrained carbon:nitrogen: phosphorus (C:N:P) ratios in planktonic biomass to the understanding of nutrient cycles and biotic feedbacks in marine ecosystems, we looked for analogous patterns in forest ecosystems worldwide. We used data from the literature to examine the stoichiometry of C, N, and P in forest foliage and litter on both global and biome levels. Additionally, we examined the scaling of nutrient investments with biomass and production both globally and within biomes to determine if and when these ratios respond to macroscale ecosystem properties (such as nutrient availability). We found that, while global forest C:N:P ratios in both foliage and litter were more variable than those of marine particulate matter, biome level (temperate broadleaf, temperate coniferous, and tropical) ratios were as constrained as marine ratios and statistically distinct from one another. While we were more interested in the relative constancy of the C:N:P ratios than their numerical value we did note, as have others, that the atomic ratios calculated for foliage (1212:28:1) and litter (3007:45:1) reflect the increased proportion of C-rich structural material characteristic of terrestrial vegetation. Carbon : nutrient ratios in litter were consistently higher than in comparable foliar data sets, suggesting that resorption of nutrients is a globally important mechanism, particularly for P. Litter C:N ratios were globally constant despite biome-level differences in foliar C:N; we speculate that this strong coupling may be caused by the significant contribution of immobile cell wall bound proteins to the total foliar N pool. Most ratios scaled isometrically across the range of biomass stocks and production in all biomes sug- gesting that ratios arise directly from physiological constraints and are insensitive to factors leading to shifts in biomass and production. There were, however, important exceptions to this pattern: nutrient investment in broadleaf forest litter and coniferous forest foliage increased disproportionately relative to C with increasing biomass and production sug- gesting a systematic influence of macroscopic factors on ratios.

Age-Related Decline in Forest Productivity: Pattern and Process

Abstract: Publisher Summary This chapter reviews the evidence for the pattern of growth decline with age and discusses the evidence for the mechanisms that may be responsible. It begins with an overview of the proposed mechanisms. The chapter also presents a framework for understanding the changes in stand productivity with age, because many of the proposed mechanisms are linked and affect carbon allocation. The available information on the importance of various mechanisms behind growth decline, in the context of the stand carbon cycle is presented. The common patterns of a decline in stand leaf area and leaf photosynthetic capacity suggest a new model of carbon balance with stand development. In this model, photosynthesis and above-ground dry-matter production increase with canopy development. After the forest reaches a maximum leaf area, photosynthesis and dry-matter production decline as leaf area, photosynthetic capacity, and photosynthesis also decline. The model assumes that allocation to respiration and below ground to roots and symbionts is a constant fraction of assimilation over the life of a forest stand.