Nutrient Cycling and Limitation: Hawai'i as a Model System

  • Peter Vitousek
Princeton University Press: 2004. 232 pp. $79.50, £51.95 (hbk); $35, £22.95 (pbk) 0691115796 | ISBN: 0-691-11579-6
Life goes on: plants recycle nutrients to grow from a lava flow. Credit: ANNIE GRIFFITHS BELT/NATIONAL GEPGRAPHIC/GETTY IMAGES

The regulation of growth by nutrient availability and the control of cycling of the elements through living communities are basic ideas in the field of ecology. Nutrient cycling, or biogeochemistry as it is known, is now a rich research field with a vast literature linked to disciplines as disparate as ecology, soil science and atmospheric science. It forms a bridge between the life and earth sciences, both of which are concerned with the cycling of elements but for vastly different reasons.

The ecological or process-oriented approach to nutrient cycling largely traces back to seminal work in New England in the 1960s and 1970s. In that oeuvre, Peter Vitousek's work for his doctoral thesis began to place nutrient cycling in a mechanistic rather than a budgetary framework. The concept of the limitation of nutrients was central, defined as “occurring when the addition of an essential element increases the growth of individual organisms or populations, or increases the rate of a biological process” (F. S. Chapin et al. Am. Nat. 127, 48–58; 1986). Nutrient limitation had long been known to foresters and agronomists as a spatially variable property but was usually treated as a static site characteristic. Following the publication of the nutrient-retention hypothesis by Vitousek and William Reiners (BioScience 25, 376–381; 1975), nutrient availability was viewed as an emergent property of an ecosystem, a dynamic property controlled by biological, hydrological and geological interactions.

I vividly remember Vitousek stating in a (probably beer-fuelled) conversation about research focus and scientific success that his focus was on “understanding nutrient limitation during succession”. His work began by understanding the interactive controls over nutrient limitation after forest disturbance. In Nutrient Cycling and Limitation, Vitousek explores this theme on a grand canvas, basing it on his own work and that of a small army of students and collaborators.

The island of Hawaii is formed from lava flows of diverse and known ages spanning many millions of years. Ecosystems have developed on soils formed from these lava, drawing from a relatively common palette of species but under vastly different conditions of nutrient limitation, depending on the age of the soils. Vitousek reports on several decades of research using age gradients (along with climatic gradients and manipulation and natural disturbance within the geological template) aimed at understanding how nutrient limitation has evolved as the lava soils of Hawaii have aged over the past 5 million years or so.

He expands the concepts of nutrient cycling, inputs and losses on the ecosystem disturbance and recovery time scale (from 10 to 1,000 years) to geological time. Processes that on ecosystem time scales are either too slow to matter, or too episodic, come to dominate on geological time scales. Expanding the time scale expands the spatial scale as well: the parsimonious explanation for some aspects of Hawaiian geochemistry turns out to be the transport of nutrient-containing dust across the Pacific, a process that occurs at low instantaneous rates and during climatic episodes separated in geological time, but that is essential to budgets over millions of years. Today's Hawaiian ecosystem dynamics, though, are controlled partly by nutrient budgets and ratios reflecting these inputs over the ages.

While Nutrient Cycling and Limitation builds a strong bridge to the geological view of biogeochemistry, and to geological time scales, it also extends the biological paradigm. In geochemistry, organisms often appear as essentially passive transducers of physical forces into chemical dynamics. In this view, athough rates might differ in the presence or absence of organisms, the geophysical environment is viewed as shaping the system.

Vitousek's view of nature is richer by far. He shows how the biogeochemical characteristics of organisms can alter the trajectory of geochemical development, on multiple time scales. He views these organismal characteristics as being shaped by the organisms' deep evolutionary history. When organisms migrate to or invade Hawaii, the conflict between their evolutionary history and that of the island can create new biogeochemical conditions and complex responses. This leads to a contingent rather than an environmentally deterministic view of ecological dynamics, and is an important counterpart to the simpler views often espoused in biogeography.

This short review does not do justice to the range of topics addressed in Nutrient Cycling and Limitation, nor does it convey the depth of theoretical perspective couched in reams of hard-won experimental and observational data. This book will reward reading and re-reading, and is an excellent introduction to biogeochemical ecology for those coming from other fields of science.