抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

https://www.nrs.fs.fed.us/pubs/jrnl/2011/nrs_2011_pan_002-supporting.pdf

Supporting Online Material for A Large and Persistent Carbon Sink in the World's Forests

Common understanding of the causes of land-use and land-cover change is dominated by simplifications which, in turn, underlie many environment-development policies. This article tracks some of the major myths on driving forces of land-cover change and proposes alternative pathways of change that are better supported by case study evidence. Cases reviewed support the conclusion that neither population nor poverty alone constitute the sole and major underlying causes of land-cover change worldwide. Rather, peoples’ responses to economic opportunities, as mediated by institutional factors, drive land-cover changes. Opportunities and

/pdf/the-causes-of-land-use-and-land-cover-change-moving-beyond-3nfu1yqkcy.pdf

The causes of land-use and land-cover change: moving beyond the myths

Recent climatic changes have enhanced plant growth in northern mid-latitudes and high latitudes. However, a comprehensive analysis of the impact of global climatic changes on vegetation productivity has not before been expressed in the context of variable limiting factors to plant growth. We present a global investigation of vegetation responses to climatic changes by analyzing 18 years (1982 to 1999) of both climatic data and satellite observations of vegetation activity. Our results indicate that global changes in climate have eased several critical climatic constraints to plant growth, such that net primary production increased 6% (3.4 petagrams of carbon over 18 years) globally. The largest increase was in tropical ecosystems. Amazon rain forests accounted for 42% of the global increase in net primary production, owing mainly to decreased cloud cover and the resulting increase in solar radiation.

http://cliveg.bu.edu/download/manuscripts/nemani01.pdf

Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999

I. CONTEXT * The Ecosystem Concept * Earth's Climate System * Geology and Soils * II. MECHANISMS * Terrestrial Water and Energy Balance * Carbon Input to Terrestrial Ecosystems * Terrestrial Production Processes * Terrestrial Decomposition * Terrestrial Plant Nutrient Use * Terrestrial Nutrient Cycling * Aquatic Carbon and Nutrient Cycling * Trophic Dynamics * Community Effects on Ecosystem Processes * III. PATTERNS * Temporal Dynamics * Landscape Heterogeneity and Ecosystem Dynamics * IV. INTEGRATION * Global Biogeochemical Cycles * Managing and Sustaining Ecosystem * Abbreviations * Glossary * References

Principles of Terrestrial Ecosystem Ecology

The rates at which lands in the United States were cleared for agriculture, abandoned, harvested for wood, and burned were reconstructed from historical data for the period 1700-1990 and used in a terrestrial carbon model to calculate annual changes in the amount of carbon stored in terrestrial ecosystems, including wood products. Changes in land use released 27 +/- 6 petagrams of carbon to the atmosphere before 1945 and accumulated 2 +/- 2 petagrams of carbon after 1945, largely as a result of fire suppression and forest growth on abandoned farmlands. During the 1980s, the net flux of carbon attributable to land management offset 10 to 30 percent of U.S. fossil fuel emissions.

https://science.sciencemag.org/content/sci/285/5427/574.full.pdf

The U.S. Carbon Budget: Contributions from Land-Use Change

The distribution of sources and sinks of carbon among the world's ecosystems is uncertain Some analyses show northern mid-latitude lands to be a large sink, whereas the tropics are a net source; other analyses show the tropics to be nearly neutral, whereas northern mid-latitudes are a small sink Here we show that the annual flux of carbon from deforestation and abandonment of agricultural lands in the Brazilian Amazon was a source of about 02 Pg Cyr(-1) over the period 1989-1998 (1 Pg is 10(15) g) This estimate is based on annual rates of deforestation and spatially detailed estimates of deforestation, regrowing forests and biomass Logging may add another 5-10% to this estimate, and fires may double the magnitude of the source in years following a drought The annual source of carbon from land-use change and fire approximately offsets the sink calculated for natural ecosystems in the region Thus this large area of tropical forest is nearly balanced with respect to carbon, but has an interannual variability of +/- 02 PgC yr(-1)

Annual fluxes of carbon from deforestation and regrowth in the Brazilian Amazon

A period of continental aridification and ecosystem change occurred about seven million years ago. A global sea surface temperature reconstruction identifies cooling temperatures and a strengthened meridional temperature gradient at this time.

Late Miocene global cooling and the rise of modern ecosystems

The amount of carbon released to the atmosphere as a result of deforestation is determined, in part, by the amount of carbon held in the biomass of the forests converted to other uses. Uncertainty in forest biomass is responsible for much of the uncertainty in current estimates of the flux of carbon from land-use change. We compared several estimates of forest biomass for the Brazilian Amazon, based on spatial interpolations of direct measurements, relationships to climatic variables, and remote sensing data. We asked three questions. First, do the methods yield similar estimates? Second, do they yield similar spatial patterns of distribution of biomass? And, third, what factors need most attention if we are to predict more accurately the distribution of forest biomass over large areas? Amazonian forests (including dead and below-ground biomass) vary by more than a factor of two, from a low of 39 PgC to a high of 93 PgC. Furthermore, the estimates disagree as to the regions of high and low biomass. The lack of agreement among estimates confirms the need for reliable determination of aboveground biomass over large areas. Potential methods include direct measurement of biomass through forest inventories with improved allometric regression equations, dynamic modeling of forest recovery following observed stand-replacing disturbances (the approach used in this research), and estimation of aboveground biomass from airborne or satellite-based instruments sensitive to the vertical structure plant canopies.

The spatial distribution of forest biomass in the Brazilian Amazon: a comparison of estimates

A tropical Pacific climate state resembling that of a permanent El Nino is hypothesized to have ended as a result of a reorganization of the ocean heat budget ∼3 million years ago, a time when large ice sheets appeared in the high latitudes of the Northern Hemisphere. We report a high-resolution alkenone reconstruction of conditions in the heart of the eastern equatorial Pacific (EEP) cold tongue that reflects the combined influences of changes in the equatorial thermocline, the properties of the thermocline's source waters, atmospheric greenhouse gas content, and orbital variations on sea surface temperature (SST) and biological productivity over the past 5 million years. Our data indicate that the intensification of Northern Hemisphere glaciation ∼3 million years ago did not interrupt an almost monotonic cooling of the EEP during the Plio-Pleistocene. SST and productivity in the eastern tropical Pacific varied in phase with global ice volume changes at a dominant 41,000-year (obliquity) frequency throughout this time. Changes in the Southern Hemisphere most likely modulated most of the changes observed.

https://science.sciencemag.org/content/sci/312/5770/79.full.pdf

Kira T Lawrence

Papers

The U.S. Carbon Budget: Contributions from Land-Use Change

Annual fluxes of carbon from deforestation and regrowth in the Brazilian Amazon

Late Miocene global cooling and the rise of modern ecosystems

The spatial distribution of forest biomass in the Brazilian Amazon: a comparison of estimates

Evolution of the Eastern Tropical Pacific Through Plio-Pleistocene Glaciation