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Root Dynamics (root + dynamics)

Distribution by Scientific Domains

Life Sciences	75%

Kinds of Root Dynamics

fine root dynamics

Selected Abstracts

Root dynamics and global change: seeking an ecosystem perspective

NEW PHYTOLOGIST, Issue 1 2000
RICHARD J. NORBY
Changes in the production and turnover of roots in forests and grasslands in response to rising atmospheric CO2 concentrations, elevated temperatures, altered precipitation, or nitrogen deposition could be a key link between plant responses and longer-term changes in soil organic matter and ecosystem carbon balance. Here we summarize the experimental observations, ideas, and new hypotheses developed in this area in the rest of this volume. Three central questions are posed. Do elevated atmospheric CO2, nitrogen deposition, and climatic change alter the dynamics of root production and mortality? What are the consequences of root responses to plant physiological processes? What are the implications of root dynamics to soil microbial communities and the fate of carbon in soil? Ecosystem-level observations of root production and mortality in response to global change parameters are just starting to emerge. The challenge to root biologists is to overcome the profound methodological and analytical problems and assemble a more comprehensive data set with sufficient ancillary data that differences between ecosystems can be explained. The assemblage of information reported herein on global patterns of root turnover, basic root biology that controls responses to environmental variables, and new observations of root and associated microbial responses to atmospheric and climatic change helps to sharpen our questions and stimulate new research approaches. New hypotheses have been developed to explain why responses of root turnover might differ in contrasting systems, how carbon allocation to roots is controlled, and how species differences in root chemistry might explain the ultimate fate of carbon in soil. These hypotheses and the enthusiasm for pursuing them are based on the firm belief that a deeper understanding of root dynamics is critical to describing the integrated response of ecosystems to global change. [source]

Increased temperature and precipitation interact to affect root production, mortality, and turnover in a temperate steppe: implications for ecosystem C cycling

GLOBAL CHANGE BIOLOGY, Issue 4 2010
WENMING BAI
Abstract Fine root production and turnover play important roles in regulating carbon (C) cycling in terrestrial ecosystems. In order to examine effects of climate change on root production and turnover, a field experiment with increased temperature and precipitation had been conducted in a semiarid temperate steppe in northern China since April 2005. Experimental warming decreased annual root production, mortality, and mean standing crop by 10.3%, 12.1%, 7.0%, respectively, while root turnover was not affected in 2006 and 2007 by the warming. Annual root production and turnover was 5.9% and 10.3% greater in the elevated than ambient precipitation plots. Changes in root production and mortality in response to increased temperature and precipitation could be largely attributed to the changes in gross ecosystem productivity (GEP) and belowground/aboveground C allocation. There were significant interactive effects of warming and increased precipitation on root productivity, mortality, and standing crop. Experimental warming had positive and negative effects on the three root variables (root production, mortality, standing crop) under ambient and increased precipitation, respectively. Increased precipitation stimulated and suppressed the three root variables in the unwarmed and warmed subplots, respectively. The positive dependence of soil respiration and ecosystem respiration upon root productivity and mortality highlights the important role of root dynamics in ecosystem C cycling. The nonadditive effects of increased temperature and precipitation on root productivity, mortality, and standing crop observed in this study are critical for model projections of climate,ecosystem feedbacks. These findings indicate that carbon allocation is a focal point for future research and that results from single factor experiments should be treated with caution because of factor interactions. [source]

Fine root dynamics in a loblolly pine forest are influenced by free-air-CO2 -enrichment: a six-year-minirhizotron study

GLOBAL CHANGE BIOLOGY, Issue 3 2008
SETH G. PRITCHARD
Abstract Efforts to characterize carbon (C) cycling among atmosphere, forest canopy, and soil C pools are hindered by poorly quantified fine root dynamics. We characterized the influence of free-air-CO2 -enrichment (ambient +200 ppm) on fine roots for a period of 6 years (Autumn 1998 through Autumn 2004) in an 18-year-old loblolly pine (Pinus taeda) plantation near Durham, NC, USA using minirhizotrons. Root production and mortality were synchronous processes that peaked most years during spring and early summer. Seasonality of fine root production and mortality was not influenced by atmospheric CO2 availability. Averaged over all 6 years of the study, CO2 enrichment increased average fine root standing crop (+23%), annual root length production (+25%), and annual root length mortality (+36%). Larger increase in mortality compared with production with CO2 enrichment is explained by shorter average fine root lifespans in elevated plots (500 days) compared with controls (574 days). The effects of CO2 -enrichment on fine root proliferation tended to shift from shallow (0,15 cm) to deeper soil depths (15,30) with increasing duration of the study. Diameters of fine roots were initially increased by CO2 -enrichment but this effect diminished over time. Averaged over 6 years, annual fine root NPP was estimated to be 163 g dw m,2 yr,1 in CO2 -enriched plots and 130 g dw m,2 yr,1 in control plots (P= 0.13) corresponding to an average annual additional input of fine root biomass to soil of 33 g m,2 yr,1 in CO2 -enriched plots. A lack of consistent CO2× year effects suggest that the positive effects of CO2 enrichment on fine root growth persisted 6 years following minirhizotron tube installation (8 years following initiation of the CO2 fumigation). Although CO2 -enrichment contributed to extra flow of C into soil in this experiment, the magnitude of the effect was small suggesting only modest potential for fine root processes to directly contribute to soil C storage in south-eastern pine forests. [source]

Environmental control of fine root dynamics in a northern hardwood forest

GLOBAL CHANGE BIOLOGY, Issue 5 2003
GERALDINE L. TIERNEY
Abstract Understanding how exogenous and endogenous factors control the distribution, production and mortality of fine roots is fundamental to assessing the implications of global change, yet our knowledge of control over fine root dynamics remains rudimentary. To improve understanding of these processes, the present study developed regression relationships between environmental variables and fine root dynamics within a northern hardwood forest in New Hampshire, USA, which was experimentally manipulated with a snow removal treatment. Fine roots (< 1 mm diameter) were observed using minirhizotrons for 2 years in sugar maple and yellow birch stands and analyzed in relation to temperature, water and nutrient availability. Fine root dynamics at this site fluctuated seasonally, with growth and mortality peaking during warmer months. Monthly fine root production was strongly associated with mean monthly air temperature and neither soil moisture nor nutrient availability added additional predictive power to this relationship. This relationship exhibited a seasonal temperature hysteresis, which was altered by snow removal treatment. These results suggest that both exogenous and endogenous cues may be important in controlling fine root growth in this system. Proportional fine root mortality was directly associated with mean monthly soil temperature, and proportional fine root mortality during the over-winter interval was strongly related to whether the soil froze. The strong relationship between fine root production and air temperature reported herein contrasts with findings from some hardwood forest sites and indicates that controls on fine root dynamics vary geographically. Future research must more clearly distinguish between endogenous and exogenous control over fine root dynamics in various ecosystems. [source]

Effects of water and nutrient availability on fine root growth in eastern Amazonian forest regrowth, Brazil

NEW PHYTOLOGIST, Issue 3 2010
Tâmara Thaiz Santana Lima
Summary ,Fine root dynamics is widely recognized as an important biogeochemical process, but there are few data on fine root growth and its response to soil resource availability, especially for tropical forests. ,We evaluated the response of fine root dynamics to altered availability of soil water and nutrients in a 20-yr-old forest regrowth in eastern Amazonia. In one experiment the dry season reduction in soil moisture was alleviated by irrigation. In the other experiment, nutrient supply was reduced by litter removal. We used the ingrowth core technique to measure fine root mass growth, length growth, mortality and specific root length. ,Dry-season irrigation had no significant effect on mass and length of live and dead roots, whereas litter removal reduced mass and length of live roots. For both irrigation and litter removal experiments, root growth was significantly greater in the dry season than in the wet season. ,Increased root growth was associated with decreased soil water availability. However, root growth did not increase in response to nutrient reduction in litter removal plots. Overall, our results suggest that belowground allocation may differ according to the type of soil resource limitation. [source]

Root dynamics and global change: seeking an ecosystem perspective

Biological and environmental factors controlling root dynamics and function: effects of root ageing and soil moisture

AUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2010
L.H. COMAS
Abstract Understanding factors controlling root dynamics and functioning can lead to more efficient and profitable vineyard management. However, our current understanding of root dynamics and their regulation by plant and environmental factors is limited, particularly under field conditions. This paper presents current understanding of grape root dynamics, highlighting studies using minirhizotron cameras, which directly assess root dynamics, and experiments on roots of known age, which link root phenology and function. Data summarised here show timing of grape root production varies widely among different regions, as well as among rootstocks and canopy management systems in the same region. Timing of production can be responsive to differences in soil moisture. Lifespan of grape roots, however, appears less affected by soil moisture because of nocturnal hydraulic redistribution. Root function, such as capacity for P and N uptake, declines rapidly with root age. Differences in timing and spatial distribution of root production can effect above-ground growth and vineyard water-use efficiency. Improving our understanding of when roots grow and are functionally active in agricultural systems can lead to improved water and fertiliser applications, and more precise vineyard management. Because both environmental and biological factors affect root dynamics, simple predictions of timing of root production or standing populations with shoot development are unlikely to be achieved. However, with multi-year data on root dynamics, and environmental and biological factors, regionally specific models of root populations and their functioning may be possible to develop. [source]

Estimating Fine Root Turnover in Tropical Forests along an Elevational Transect using Minirhizotrons

BIOTROPICA, Issue 5 2008
Sophie Graefe
ABSTRACT Growth and death of fine roots represent an important carbon sink in forests. Our understanding of the patterns of fine root turnover is limited, in particular in tropical forests, despite its acknowledged importance in the global carbon cycle. We used the minirhizotron technique for studying the changes in fine root longevity and turnover along a 2000-m-elevational transect in the tropical mountain forests of South Ecuador. Fine root growth and loss rates were monitored during a 5-mo period at intervals of four weeks with each 10 minirhizotron tubes in three stands at 1050, 1890, and 3060 m asl. Average root loss rate decreased from 1.07 to 0.72 g/g/yr from 1050 to 1890 m, indicating an increase in mean root longevity with increasing elevation. However average root loss rate increased again toward the uppermost stand at 3060 m (1.30 g/g/yr). Thus, root longevity increased from lower montane to mid-montane elevation as would be expected from an effect of low temperature on root turnover, but it decreased further upslope despite colder temperatures. We suggest that adverse soil conditions may reduce root longevity at high elevations in South Ecuador, and are thus additional factors besides temperature that control root dynamics in tropical mountain forests. [source]