SOIL DEVELOPMENT AND PROPERTIES | Nutrient Cycling

Nutrient Accumulation and Cycling in Loblolly Pine (Pinus taeda L.) Plantation Ecosystems: The First Twenty Years1

Publisher Summary This chapter emphasizes on the fundamental unity of ecosystem physiology for describing all aspects and complexity of woodland ecology. The essentially dynamic nature of woodland ecosystems is masked by the impression of stability and permanence engendered by the longevity of trees. Yet, woodland ecosystems are characterized by a mass seasonal transfer of organic matter, energy, water and chemical elements, the seasonal magnitudes of that change greatly as the trees mature, and are replaced by trees of different species. The chapter discusses the concept and dynamics of forest ecosystem, organic matter dynamics, energy dynamics, woodland water circulation, circulation of chemical elements of woodland ecosystems. A better knowledge of woodland ecosystem dynamics is needed as woodlands, by virtue of their size and mass transfer of material, possess certain unique attributes enabling them to serve as models for fundamental studies into the interplay of climate, soil and vegetation. Although the problems to be solved in woodland ecology are so varied and immense, they present ecologists with both a challenge and a means of demonstrating the practical application of their subject for the welfare of man.

Quantitative Ecology and the Woodland Ecosystem Concept

The total weight of vegetation on an area of just over 1 acre of old secondary forest in the moist forest zone of Ghana has been determined, and found to be equivalent to roughly 150 tons per acre dry weight. The nutrient content of each component of the vegetation was also determined and showed that the amounts of the major nutrients immobilised in the vegetation were: N, 1,800 lb./acre; P, 120 lb./acre; K, 800 1b./acre; Ca, 2,400 lb./acre; Mg, 350 lb./acre. The corresponding amounts of nutrients in the top foot of soil supporting the vegetation were: total N, 4,100 lb./acre; ‘available’ P, 11 lb./acre; exchangeable K, 580 lb./acre; exchangeable Ca, 2,300 lb./acre; exchangeable Mg, 330 lb./acre. About half the nutrients stored in the vegetation were contained in readily combustible material, and except for N would be released to the soil if the forest were cleared and burnt for cultivation. The quantity of roots and the amounts of nutrients contained in them were not sufficiently great to make an important addition to the nutrient supply in the soil during subsequent cultivation. Of the total quantity of roots supporting the vegetation 85.5 per cent by weight were within 1 foot of the soil surface.

Nutrient content of the moist tropical forest of Ghana

Calculations are presented on the quantities of N, P, K, Mg and Ca in the soil and above-ground portions of two spruce-pulpwood stands on sites of average fertility in northern and southern Quebec. The magnitude of the depletions of these nutrients from the site, in full-tree and tree-length methods of logging, are compared with the available and total quantities of them in the soil. The ranges of values, from the literature, for the input of these nutrients in dust and precipitation, and the losses in leaching, are presented and discussed in relation to the logging losses.It is concluded that on both sites it is unlikely that full-tree logging will result in any reduction in growth, due to nutrient removal, during the second rotation of trees. However, nutrient depletion due to full-tree logging, particularly with respect to Ca, K and N, may require correction by means of fertilizers in forest ecosystems of marginal fertility. These are usually either dry sites with low reserves of organic matter and low...

The Influence of Wood Harvesting on the Nutrient Status of Two Spruce Stands

The combined effects of whole-tree harvesting (WTH) and soil leaching by both acid deposition and naturally-produced carbonic acid were evaluated in a mixed oak and a loblolly pine forest growing on similar soils in the Ridge and Valley province of eastern Tennessee. It was hypothesized that nutrient export via WTH would be greater in a mixed oak stand than in the loblolly pine stand because of greater nutrient concentrations in oak and hickory species than in pine. This hypothesis was true for N,P, and particularly Ca at the time of harvest, but not for K or Mg. When expressed on an annual basis, exports of N,P,K, and Mg were greater in the loblolly pine site and only Ca export was greater in the mixed oak site. It was also hypothesized that the large accumulation of Ca in the oak and hickory vegetation would cause lower exchangeable Ca2+ in soils, and, consequently, lower Ca2+ leaching in the mixed oak site than in the loblolly pine site. This hypothesis was supported by the data, which indicated 340–370% more exchangeable Ca and 100% more Ca2+ leaching in the loblolly pine site than in the mixed oak site.

SOIL DEVELOPMENT AND PROPERTIES | Nutrient Cycling

References

Nutrient Accumulation and Cycling in Loblolly Pine (Pinus taeda L.) Plantation Ecosystems: The First Twenty Years1

Quantitative Ecology and the Woodland Ecosystem Concept

Nutrient content of the moist tropical forest of Ghana

The Influence of Wood Harvesting on the Nutrient Status of Two Spruce Stands

Nutrient export by leaching and whole-tree harvesting in a loblolly pine and mixed oak forest

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