ResearchMWatch Global circulation patterns mask deforestation’s impacts
warming temperatures If the earth’s surface continues to warm, the amount of carbon dioxide released into the atmosphere from soil respiration may be less than scientists currently predict, according to new evidence reported by Yiqi Luo and colleagues at the University of Oklahoma. The findings suggest that assumptions used in current climate change models regarding the temperature sensitivity of soil respiration may be unwarranted. The researchers conducted experiments in a tall grass prairie in Oklahoma to study how soil respiration responds to a temperature increase of 2 °C. Under current climate conditions, scientists expect soil respiration to approximately double for
temporal scales than those examined in this study, soil ecosystems in warmer climates are likely to acclimatize more than those in cooler climates. (Nature 2001, 413, 622–625)
Changes in global circulation patterns over several decades are masking the full impacts of deforestation in the Amazon Basin, according to TsingChang Chen, Eugene Takle, and colGlobal warming’s evolutionary leagues at Iowa State University. Consequently, numerical models for downside simulating deforestation, which typiAlthough plants can evolve in recally do not account for long-term sponse to climate change, there’s a changes, are likely to be in error and big problem: Some of them are not may even predict the opposite of able to adapt fast enough to survive. what occurs. As a result, some plants that are Several deforestation impact modhere today may not be around toels predict that as the Amazon rainmorrow, report Julie Etterson and forest disappears and is replaced by Ruth Shaw of the University of pasture, higher surface temperatures, Minnesota’s Department of Ecology leading to less evaporation and rainin St. Paul. fall, will result. However, precipitation Generally, plants respond to data over the past changing condicentury show a trend tions by either toward increased adapting or miClimate Atmospheric CO2 precipitation in grating to other warming concentration the Amazon Basin. regions, where The researchers conditions are attribute this dismore favorable Carbon Photosynthesis Acclimatization sequestration crepancy to the fact to their survival. that global water Habitat fragNutrient Vegetation availability vapor converging in mentation, howgrowth South America is a ever, is likely to major force that make migration Respiration overrides all others. less of an option Positive Negative Such large-scale in the future, in forces, however, are which case, Major feedbacks in a coupled climate–carbon cycle system. not included in curplants will have Acclimatization of soil respiration to warming could weaken to rely on their rent models. the positive warming–respiration–atmospheric CO2 feedback. The effect of ability to adapt. Source: Copyright 2001 Macmillan Magazines Ltd. global climate patterns on deforestaUnfortunately, tion impacts can be adaptive evolueither positive or negative, say the reevery 10 °C increase, but under tion can be slowed down when varisearchers. In the coming decades, warmer conditions, the researchers ous beneficial plant traits compete global patterns could reverse, in found soil respiration to be less sensiwith each other to be expressed, say which case the Amazon Basin could tive to temperature. Etterson and Shaw. In this instance, experience intense drying and one of traits that otherwise might help the the worst droughts ever. The effect According to the researchers, this plants adapt and survive are slower to could be much worse than that pretemperature sensitivity reduction be inherited together than they would dicted with current models, they may be caused by several factors rebe separately. warn. (Bull. Am. Meteorol. Soc. 2001, lated to warmer conditions, including Etterson and Shaw 82, 2209–2216) increased soil dryness, which reduces demonstrated this behavior by root and microbial activity, and restudying the genetic architecture of duced substrate supplies. If the rethree populations of Chamaecrista Soil ecosystems adapt to sponse holds over larger spatial and fasciculata, a common North DECEMBER 1, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY I 479 A
and growing thicker leaves help plants adapt to changing climate conditions, but antagonistic genetic relationships between these traits prolong the time it takes for plants to do both at once. (Science 2001, 294, 151–154).
Lakes feel effects of climate change Dutch researchers have uncovered the first evidence that climate change may strongly influence the condition of lakes and their ecosystems. The average temperature of European lakes has risen by more than a degree since 1960, as a result of climatic changes in the North Atlantic, they report. Increased temperatures could help lakes recover from eutrophication. Marten Scheffer and colleagues from Wageningen University studied 71 shallow lakes in the Netherlands and 28 central European lakes. They found that over the past decades, lake temperatures have “risen significantly”, in line with the North Atlantic Oscillation (NAO), a large-scale climatic phenomenon. The NAO index in winter can be used to predict the temperature of lakes in the subsequent year. The team also demonstrated that increased water temperatures produced earlier periods of clear water. Lakes often, but not always, experience a phase of clear water in the spring. This occurs as zooplankton become more active after the winter and start filtering algae from the water. Scheffer estimates that clear-water phases appear about one week earlier if the first-quarter water temperature is one degree higher. Higher temperatures also appear to make clear-water phases more likely in lakes, where such phases are rare. This is good news for turbid lakes. Submerged aquatic plants, which are key to recovering biodiversity in these damaged lake ecosystems, benefit from improved light conditions and higher temperatures. (Limnol. Oceanogr. 2001, 46, 1780–1783)
gus, Verticillium sp., which reduces the ions and forms ~25-nm-diameter gold nanoparticles. The work helps to fill a growing need to develop “green” ways of synthesizing nanoparticles. As gold particles form inside the fungal cells, the cells change from golden yellow to bright purple. Using UV-visible spectroscopy and X-ray diffraction, the researchers confirmed that no extracellular particle formation occurs. The particle size was estimated from the diffraction pattern. Scanning electron microscopy confirmed that the mycelia were covered with welldispersed gold nanoparticles. With these facts and transmission electron microscopy data, the researchers speculated on the mechanism of reduction and particle formation. Many organisms produce inorganic materials naturally, and some bacteria have been shown to reduce aqueous silver ions to silver nanoparticles, but fungi are known to secrete higher levels of protein than bacteria and thus synthesize more particles. Because the particles bind better to a fungus’s cytoplasmic membrane than its cell wall, the process may be used for producing catalysts or precursors to electronic coatings. (Angew. Chem., Int. Ed. Engl. 2001, 40, 3585–3588)
Fungi make gold nanoparticles Researchers in India at the National Chemical Laboratory, Armed Forces Medical College, and Central Institute for Medicinal and Aromatic Plants have found a nontoxic way to make gold nanoparticles using eukaryotic organisms. Aqueous gold chloride ions (AuCl4−) are simply exposed to the fun480 A I ENVIRONMENTAL SCIENCE & TECHNOLOGY / DECEMBER 1, 2001
Verticillium sp. fungal cells: (a) after removal from culture medium; (b) after exposure to 10–4 M aqueous solution of HAuCl4 for 72 hours.
