A closely spaced (1 x 1 m) cottonwood (Populus deltoides Bartr.) platation was established to evaluate the effects of nutrient availability on fine root dynamics. Slow-release fertilizer (17:6:12 N, P, K plus micronutrients) was applied to 225-m2 plots at 0, 50, 100, 200 kg N ha-1, and plots were monitored for two growing seasons. Fine root production, mortality, live root standing crop and life span were analyzed based on monthly minirhizotron observations. Fine root biomass was measured in soil cores. Fine root dynamics were controlled more by temporal, depth and root diameter factors than by fertilization. Cumulative fine root production and mortality showed strong seasonal patterns; production was greatest in the middle of the growing season and mortality was greatest after the grwoing season. Small diameter roots at shallow soil depths cycled more rapidly than large or deeper roots. The strongest trearment effects were found in the most rapidly cycling roots. The standing crop of live roots increased with fertilizer treatment according to both minirhizotron and soil coring methods. However, production and mortality had unique treatment response patterns. Although cumulative mortality decreased in response to increased fertilization, cumulative production was intermediate at 0 kg N ha-1, lowest with 50 kg N ha-1, and highest with 200 kg N ha-1. Above ground growth responded positively to fertilization up to an application rate of 50 kg N ha-1 but no further increase in application rate. Median fine root life span varied from 307 to over 700 day and increased with depth, diameter and nutrient availability.

We established Populus deltoides Bartr. stands differing in nitrogen (N) availability and tested if: (1) N-induced carbon (C) allocation could be explained by develop- mental allocation controls; and (2) N uptake per unit root mass, i.e., specific N-uptake rate, increased with N availability. Closely spaced (1 x 1 m) stands were treated with 50, 100 and 200 kg N ha -1 year 1-1 of time-release balanced fertilizer (50N, 100N and 200N) and compared with unfertilized controls (0N). Measurements were made during two complete growing seasons from May 1998 through October 1999. Repeated nondestructive measurements were carried out to determine stem height and diameter, leaf area and fine-root dynamics. In October of both years, above- and belowground biomass was harvested, including soil cores for fine-root biomass. Leaves were harvested in July 1999. Harvested tissues were analyzed for C and N content. Nondestructive stem diameter and and fine-root dynamic measurements were combined with destructive harvest data to estimate whole-tree biomass and N content at the end of the year, and to estimate specific N-uptake rates during the 1999 growing season. Shoot growth response was greater in fertilized trees than in control trees; however, the 100N and 200N treatments did not enhance growth more than the 50N treatment. Root biomass proportions decreased over time and with increasing fertilizer treatment. Fertilizer-induced changes in allocation were explained by accelerated development. Specific N-uptake rates increased during the growing season and were higher for fertilized trees than for control trees.

In a highly readable fashion, this book describes the scientific principles which are used throughout the world to ensure rapid, healthy plantation growth. It is written for a world-wide audience, from forestry professionals and scientists through to small plantation growers, to describe how plantations may be grown responsibly and profitably. The author has been a forest scientist for over 30 years.

This book describes the scientific principles that are used throughout the world to ensure the rapid, healthy growth of forest plantations. As the population of the world increases so does the amount of wood people use. Large areas of natural forests are being cleared every year and converted to other uses. Almost as large an area of plantation forests is being established annually to replace those lost natural forests. Eventually, plantations will produce a large proportion of the wood used around the world for firewood, building, the manufacture of paper and bioenergy. Forest plantations can also provide various environmental benefits including carbon storage, rehabilitation of degraded land, serving as disposal sites for various forms of industrial or agricultural waste and enhancing biodiversity in regions that have been largely cleared for agriculture. Whatever their motivation, plantation forest growers want their plantations to be healthy and grow rapidly to achieve their purpose as soon as possible. This book discusses how this is done. It is written for a worldwide audience, from forestry professionals and scientists through to small plantation growers, and describes how plantations may be grown responsibly and profitably.

The decade since the publication of the third edition of this volume has been an era of great progress in biology in general and the plant sciences in particular. This is especially true with the advancements brought on by the sequencing of whole genomes of model organisms and the development of "omics" techniques. This fourth edition of Plant Roots: The Hidden Half reflects these developments that have transformed not only the field of biology, but also the many facets of root science. Highlights of this new edition include: The basics of root research and their evolution and role in the global context of soil development and atmosphere composition New understandings about roots gained in the post-genomic era, for example, how the development of roots became possible, and the genetic basis required for this to occur The mechanisms that determine root structure, with chapters on cellular patterning, lateral root and vascular development, the molecular basis of adventitious roots, and other topics Plant hormone action and signaling pathways that control root development, including new chapters on strigolactones and brassinosteroids Soil resource acquisition from agricultural and ecological perspectives Root response to stress, with chapters that address the impact of the genomic revolution on this topic Root-rhizosphere interactions, from beneficial microorganisms to detrimental nematodes Modern research techniques for the field and the lab Each chapter not only presents a clear summation of the topic under discussion, but also includes a vision of what is to be expected in the years to come. The wide coverage of themes in this volume continues the tradition that makes this work recognized as a fundamental source of information for root scientists at all levels.

Almost 50% of the total area of Austria is forested, and the forests are dominated by commercially valuable stands of Norway spruce ( (Picea abies). The few remaining forests that resemble the natural vegetation composition are located in forest reserves with restricted management. These natural forests are used as reference systems for evaluating silvicultural research on sustainable forest management. Natural forests are expected to have high biodiversity, where the structural richness of the habitat enables complex relationships between fauna, flora, and microflora. They also provide refugia for rare plants and animals found only in natural forest types. Austria had 180 of these forest reserves up to the year 2003. Most of these forests are privately owned, and owners are compensated by the government for loss of income associated with conservation status. The Ministerial Conference for the Protection of Forest Ecosystems (MCPFE) has launched a world-wide network of protected forest areas which should cover all major forest types (MCPFE and UNECE/FAO, 2003). The sites selected for our investigation of soil conditions and communities were chosen by vegetation ecologists and soil scientists. The stands have developed under natural competition conditions with no management interventions. All sites were well documented with known forest history. Our set of sites spans gradients of environmental conditions as well as species composition, providing a realistic evaluation of the interactions of biotic and abiotic factors.