据《环境科技》（Environ. Sci. Technol.）网站2011年4月7日公布的美国9所大学与美国橡树林国家实验室以及沙漠研究所的科学家共同合作完成的研究结果，对横跨美国大陆的14个森林土壤中的Hg含量进行研究后发现，美国北部森林土壤中含Hg量竟然达到南部的森林土壤中含Hg量的16倍（ Environ. Sci. Technol., DOI: 10.1021/es104384m )。根据美国环境保护署的透露，每年进入大气层的汞在5000 t到8000 t之间。而自然的来源如火山喷发等仅是其中很少一部分,大多数是来源于工业生产，特别是燃煤发电厂。排向大气层的汞有些会迁入森林，因为森林中的树木、落叶层以及土壤均会吸收汞。因此森林已经成为自工业革命以来，一直在富集着排向大气层的汞元素。正是因为如此，科学家怀疑在全球范围内,森林对大气层汞的富集可达数十万吨,但是研究人员对其汞的地理分布知之甚少，更为令人担忧的是随着气候变暖，是否会导致汞的循环加快，使更多的汞进入到大气层。科学家们希望了解汞的迁移规律，因为它完全可能从大气中或从森林土壤层进入水体,最终在水生食物链中富集。沙漠研究所的 Daniel Obrist 领导的研究小组对横跨美国大陆的14个森林，每个森林中收集12个土样，在实验室里,采用冻干、粉碎后分析其样品中的汞和碳含量。研究人员发现,总的来说,高纬度森林土壤中汞含量较低纬度的更高一些。例如,来自美国缅因州Howland森林土壤中汞平均浓度是美国佛罗里达州盖恩斯维尔（Gainesville, Fla.）森林土壤中汞含量的17倍。根据这种分析结果研究人员认为,低纬度由于日光照射充足，导致其更多的汞蒸发,这可能会导致其在土壤中滞留期缩短，而高纬度地区气温较低，甚至有些地区气候终年严寒，被吸附而富集的金属汞不易挥发，导致汞含量高也是在预料之中。关于汞与碳含量的关系，科学家发现碳含量越高，则汞浓度也较高,这可能因为汞常与有机分子结合,所以说高碳水平可能有助于解释为什么在美国北部森林土壤含有更多的汞。美国佛罗里达大学生物系博士后Sue Natali认为，在凉爽的气候条件下,有机质分解缓慢,这可能使汞积累在土壤中，但是气候变化完全有可能扰乱这种格局。不断上升的气温可能会使有机物分解率加速、使汞逸出逃到大气中,并且最终将可能造成水体污染。这个过程是一种值得特别关注的过程,因为北纬地区气候变暖速度要快于世界其他地方。研究人员同时指出，在这个问题上应该继续深入研究,他们也承认他们拥有的实验数据非常有限。 更详细的信息请浏览： Mercury Distribution Across 14 U.S. Forests. Part I: Spatial Patterns of Concentrations in Biomass, Litter, and Soil s
四个素不相识的人组成了一个团队，参加4月在Taupo举办的100公里慈善行。四个人里，有两个来自葡萄园，一个刚大学毕业（室内设计），一个生物工程研究人员。团队名字叫'Strangers in the Night'。这个周末是第一次模拟训练，在Riverhead森林越野. 四个人里只有我有空参加。是一次很好的练兵，体会一下越野的滋味。这是营地。 有的队连续两天拉练，已安营扎寨： 注册点： Oxfam的人介绍路途特征，Oxfam的宗旨： 下午分三批出发，3：30， 4：30， 5：30， 看各个队期望有多长时间夜间行军而定。我一个人当然不想夜间行（后来才知这是个多么正确的决定！）3：32分出发。 先大路爬坡，这种路属于最好走的。 一边10公里跑，另一边32，22公里越野，不要走错： 伐木与成木： 这是艰苦行军前的最好风景：在山顶一览众山小。 马上转入真正的森林道路。 原来我们行走的trail也是山地自行车（MB)的trail,而MB上午刚举办过比赛，虽然天没下雨（谢天谢地），有些路段也非常泥泞。 一不小心就会陷入泥潭，苦不堪言。我就一脚踩入泥水，滑倒，看我的手，及右下的一点血迹： 甚至没办法通过，有地方一定要淌水。还有个水塘，也是完全把路阻断。注意：我们是第一批行军，还有很多人是在夜间通过这些路段，全靠头灯！ 大概有2/3的路在森林里，参天大树： 在森林转苦了，忽然看到： 真美啊： 视野开阔，这些路也很享受： 饮水也是问题。只带了600ML水，对水站不熟，不知有无供应，什么时候供应，所以省着喝。行走了两个小时已经dehydrated,才第一次喝水。还想如何把剩下的水留到6：30喝。下午天热，正是口干舌燥，撑不住时，看到： 觉得工作人员像天使一样：） 水太重要了！ 她告诉已经走了12公里,用了两个小时二十分钟： 后半段虽然也有难过的路段，但泥泞路少了，这就好。这是后半段最美的风景： 跟另一组团队共同走了好几公里： 4个小时45分钟后终于到达营地，天已暗。谢天谢地没有在黑夜行军，但Oxfam就必须这样了。 走完后我的鞋袜： Course Description: With milling going on in some parts close to the base we’ll take you all the way up Barlow Road to start with (sorry about that, but don’t worry 95% of the trails are still there, and they are looking great!). Once you have made the trek up Barlow road, you’ll go left on to Trig Road for a minute or two before jumping into a cool little track off Trig Road. For the next 4km’s from this point you will generally be heading down! And we guarantee you will love this section of fast hard packed trails linked by very short gravel sections. You will then have a short climb before getting to you first drinks station. A really nice native section follows, you will enjoy this! And from there you can really get into your work on the flat trail’s and roads that follow for the next few km. Once off Campbell Road the ‘out the back loop’ is a wicked combination long downhill’s, a couple of short sharp uphill’s, and some magic view’s!! Once you pass your third drinks station, it’s a nice and flat last km or two back to base!
Strategies for Increasing Carbon Stored in Forests and Wood "Several strategies for offsetting carbon emissions have been proposed or are currently being implemented in the U.S.," says Mike Ryan from the United States Department of Agriculture, Forest Service and lead author of the paper. "Some of the important tradeoffs are worth mentioning because many people have viewed forests as a simple and uncomplicated partial solution to reducing CO2 in the atmosphere, and they are not." Mike Ryan and colleagues discuss eight strategies being used or proposed in the U.S., and the risks, uncertainties and tradeoffs of each. These include avoiding deforestation, afforestation (planting or replanting forests), decreasing harvests, increasing the growth rate of existing forests, using biomass energy from forests to reduce carbon emissions, using wood products in place of concrete or steel for building materials, implementing urban forestry and using fuel management to reduce fire threats. The tradeoffs of these strategies need to be taken into account accordingly. By reducing harvests, avoiding deforestation or afforestation, for example, we could increase the amount of forest carbon in the U.S. But the demand for forest products would still remain, so tree harvesting or other current land use may move to other areas, canceling out the carbon benefit to the atmosphere of the changes in the U.S. "The numbers are daunting because our fossil fuel use is so large," says Ryan. "Take increasing the use of wood for biomass energy: In order to offset just 10 percent of our fossil fuel use, we would need to harvest all of the annual forest production of U.S. forests. This practice also would lower the long term effects of carbon stored in forests." "To offset another 10 percent of our fossil fuel use with tree planting would require planting trees on one-third of our agricultural land," says co-author Robert B. Jackson from Duke University. These strategies are not yet cost effective and would require a price on carbon, regulation or incentives to succeed, say the authors. Another risk in relying on forests to lower atmospheric CO2 is that climate change may reduce carbon stored in forests by increasing fires, storms and insect outbreaks. "So, we need to make sure we focus on retaining the forests we have by making sure we get tree regeneration after these disturbances," says Ryan. The authors review these methods, and the cycle of forest growth, death and regeneration, and the use of wood removed from forests and how it ties into measuring carbon pools and flows. They also analyze the processes of measuring forest carbon and the science behind mechanisms proposed for increasing the amount of carbon stored in forests. "This topic could not be more relevant," says Jill Baron, Editor-in-Chief of Issues in Ecology. "The need for biological carbon storage is ever apparent, but the methods for making the most of our forest stores while not reducing other important forest ecosystem services are still underexplored. This paper, like future Issues in Ecology, provides a synthesis of the current scientific research and understanding on the topic. It should be on the desk of anyone interested in how to minimize the effects of climate change, and certainly anyone assigned with mitigating climate change through forest carbon storage." "A Synthesis of the Science on Forests and Carbon in U.S. Forests" is published in the spring 2010 edition of Issues in Ecology, a publication of the Ecological Society of America reporting the consensus on a specific issue from a panel of experts. This report, along with past and future issues, is available online at http://esa.org/science_resources/issues.php.
题目 Nutrient Cycling and Limitation: Hawai'i as a Model System 作者 Peter M. Vitousek 获奖 Winner of the 2005 Marsh Ecology Book of the Year Award, British Ecological Society 出版信息 Paper | 2004 | $52.00 / 35.95 232 pp. | 6 x 9 | 10 halftones. 84 line illus. 18 tables. 介绍 The availability or lack of nutrients shapes ecosystems in fundamental ways. From forest productivity to soil fertility, from the diversity of animals to the composition of microbial communities, nutrient cycling and limitation are the basic mechanisms underlying ecosystem ecology. In this book, Peter Vitousek builds on over twenty years of research in Hawai'i to evaluate the controls and consequences of variation in nutrient availability and limitation. Integrating research from geochemistry, pedology, atmospheric chemistry, ecophysiology, and ecology, Vitousek addresses fundamental questions: How do the cycles of different elements interact? How do biological processes operating in minutes or hours interact with geochemical processes operating over millions of years? How does biological diversity interact with nutrient cycling and limitation in ecosystems? The Hawaiian Islands provide the author with an excellent model system for answering these questions as he integrates across levels of biological organization. He evaluates the connections between plant nutrient use efficiency, nutrient cycling and limitation within ecosystems, and nutrient input-output budgets of ecosystems. This book makes use of the Hawaiian ecosystems to explore the mechanisms that shape productivity and diversity in ecosystems throughout the world. It will be essential reading for all ecologists and environmental scientists. Reviews: 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. . . . This book will reward reading and re-reading, and is an excellent introduction to biogeochemical ecology for those coming from other fields of science.--David Schimel, Nature One of the most impressive aspects of Nutrient Cycling and Limitatio is the scope of the material it covers, and the extent to which the material is integrated to provide a truly ecosystem-level overview, that is itself placed neatly within a global context. . . . he book provides a wide-ranging and authoritative coverage of a crucial topic.--Graeme Hastwell, Austral Ecology Peter Vitousek's Nutrient Cycling and Limitation makes an important contribution to the field of biogeochemistry. . . . excellent book. . . . Nutrient Cycling and Limitation is essential reading for students and scientists interested in terrestrial biogeochemistry. It is a model of good science writing and a crisp and clear introduction to some of the big ideas that intrigue ecosystem ecologists.--Jerry Melillo, Bioscience Endorsement: Peter Vitousek is tied closely to the 'aina--the land--of Hawaii, both by birth and by the successful scientific career he has nurtured over the past two decades. His personal, and sometimes passionate, presentation sweeps across habitats, across phyla and across disciplines. It is an authoritative account of his research and his vision.--David M. Karl, University of Hawaii 图书内容 TABLE OF CONTENTS: List of Tables xi List of Figures xiii Preface xix Chapter One: Introduction 1 Chapter Two: The Hawaiian Islands as a Model Ecosystem 6 Model Systems 6 Microcosms and Well-studied Systems 8 A Brief Natural History 9 The Formation of the Hawaiian Islands 9 Determinants of Climate 15 Isolation 19 Evolution, Conservation, and Culture 20 Evolution and Speciation 20 Conservation Biology 22 Cultural Evolution 22 Chapter Three: Gradients in Environmental Factors, Gradients in Ecosystems 24 The State Factor Framework 24 Environmental Gradients as Model Systems 26 Temperature 27 Precipitation 29 The Mauna Loa Matrix 30 A Substrate Age Gradient across the Hawaiian Islands 31 Age Control 35 Climate History 35 Basic Features of the Gradient 39 Chapter Four: Patterns and Processes in Long-term Ecosystem Development 42 A Theory for Nutrient Dynamics during Ecosystem Development 42 Biogeochemical Processes on the Substrate Age Gradient 45 Soil P Pools 45 C and N Pools 45 Available Nutrients 46 Foliar Nutrients 49 Forest Productivity 51 Efficiencies of Resource Use 53 Decomposition and Nutrient Regeneration 59 Soil Organic Matter Turnover 66 Plant-Soil-Microbial Feedbacks 66 Chapter Five: Experimental Studies of Nutrient Limitation and the Regulation of Nutrient Cycling 70 Fertilization Experiments 71 Nutrient Limitation 74 Nutrient Availability and Plant-Soil-Microbial Feedback 78 Tissue Nutrient Concentrations 78 Productivity 78 Resource Efficiencies 79 Decomposition 84 Nutrient Regeneration 87 Controls of Plant-Soil-Microbial Feedback 87 Chapter Six: Nutrient Inputs to Hawaiian Ecosystems: Pathways, Rates, and Controls 92 Inputs of Elements 92 Weathering 93 Concepts and Definitions 93 Approaches 94 Element Inputs via Weathering 97 Atmospheric Inputs 98 Background 98 Deposition Measurements 100 Inputs of Water 101 Nitrogen Inputs 101 Influence of an Active Volcano 102 Inputs of Other Elements 103 Long-Distance Dust Transport 105 Background 105 Methods 105 Element Inputs 106 The Fate of Dust 107 Biological N Fixation 109 Background 109 Approach 109 Rates of Fixation 110 Other Inputs 110 Combined Inputs by All Known Pathways 111 Strontium Isotopes: A Direct Test of Input Pathways 112 Chloride and Sulfate 114 Mobile Cations 114 Silicon and Aluminum 116 Nitrogen and Phosphorus 117 Chapter Seven: Nutrient Outputs: Pathways, Controls, and Input-Output Budgets 121 Output Pathways 122 Leaching 122 N-Containing Trace Gases 124 Erosion 126 Other Pathways of Loss 126 Rates and Controls of N and P Losses 128 Input-Output Budgets 133 Budget Calculations 134 Using These Element Budgets 142 Chapter Eight: Issues and Opportunities 143 Interactions of Time Scales 143 An Exploratory Model 143 Supply versus Demand 144 Plant-Soil-Microbial Feedbacks 146 Sources and Sinks 148 Inputs and Outputs 150 Interactions across Scales 152 The Regulation of Nutrient Inputs and Outputs 154 Demand-Independent Pathways of Element Loss 155 Implications of Demand-Independent Nutrient Losses 159 Stoichiometry and Flexibility 160 Within-System Element Cycling 162 Inputs and Outputs 169 Biological N Fixation 173 Differences in Populations, Species, and Diversity 177 Biological Differences and Ecosystem Functioning 177 Diversity and Ecosystem Functioning 184 Three Final Points 188 References 191 Index 219
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