In this century, increasing concentrations of carbon dioxide (CO2) and other greenhouse gases in the Earth's atmosphere are expected to cause warmer surface temperatures and changes in precipitation patterns. At the same time, reactive nitrogen is entering natural systems at unprecedented rates. These global environmental changes have consequences for the functioning of natural ecosystems, and responses of these systems may feed back to affect climate and atmospheric composition. Here, we report plant growth responses of an ecosystem exposed to factorial combinations of four expected global environmental changes. We exposed California grassland to elevated CO2, temperature, precipitation, and nitrogen deposition for five years. Root and shoot production did not respond to elevated CO2 or modest warming. Supplemental precipitation led to increases in shoot production and offsetting decreases in root production. Supplemental nitrate deposition increased total production by an average of 26%, primarily by stimulating shoot growth. Interactions among the main treatments were rare. Together, these results suggest that production in this grassland will respond minimally to changes in CO2 and winter precipitation, and to small amounts of warming. Increased nitrate deposition would have stronger effects on the grassland. Aside from this nitrate response, expectations that a changing atmosphere and climate would promote carbon storage by increasing plant growth appear unlikely to be realized in this system.

Belowground vertical community composition and maximum rooting depth of the Edwards Plateau of central Texas were determined by using DNA sequence variation to identify roots from caves 5-65 m deep. Roots from caves were identified by comparing their DNA sequences for the internal transcribed spacer (ITS) region of the 18S-26S ribosomal DNA repeat against a reference ITS database developed for woody plants of the region. Sequencing the ITS provides, to our knowledge, the first universal method for identifying plant roots. At least six tree species in the system grew roots deeper than 5 m, but only the evergreen oak, Quercus fusiformis, was found below 10 m. The maximum rooting depth for the ecosystem was Ϸ25 m.18 O isotopic signatures for stem water of Q. fusiformis confirmed water uptake from 18 m underground. The availability of resources at depth, coupled with small surface pools of water and nutrients, may explain the occurrence of deep roots in this and other systems.Plant rooting depth influences the hydrology, biogeochemistry, and primary productivity of terrestrial ecosystems (1-7). Progress in determining the maximum rooting depth of species and in identifying the resources taken up at depth is limited by several factors. Access to the soil is difficult, particularly in rocky soils and in deeper layers. In addition, no universal method exists for identifying roots obtained from the soil, especially when only fine roots are available (8-10). There is considerable variation in maximum rooting depth and root biomass distributions, which affects the functioning of ecosystems (11-15). For example, in eastern Amazonia, water uptake from 2-to 8-m soil depths contributes to more than threefourths of the transpiration of evergreen forest in the dry season and helps maintain an evergreen canopy on Ͼ1 million km 2 of tropical forest (1, 16). Characteristics of roots and the soil are also needed in models of biosphere-atmosphere interactions (17). A comparison of 14 land surface parameterizations concluded that rooting depth and vertical soil characteristics were the most important factors explaining scatter among models for simulated transpiration (18, 19), determining the amount of water available to plants and partitioning its uptake from different layers. Conclusions were similar for global soil-moisture dynamics (20,21). Global simulations of net primary productivity and transpiration increased 16% and 18%, respectively, when optimized rooting depths incorporated soil water deeper than 1 m (22).We developed a method for identifying roots based on DNA sequence variation and applied this method to roots collected from caves 5-65 m deep to determine the belowground community structure and maximum rooting depth of the 100,000-km 2 Edwards Plateau of central Texas. The Edwards Plateau and other karst regions in Texas cover one-fifth of the state, with Ͼ3,000 caves identified to date (23, 24). Karst systems, in general, cover 7-10% of land surface area globally and supply a quarter of the earth's population ...

The enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase is best known for catalysing a rate-limiting step in cholesterol biosynthesis, but it also participates in the production of a wide variety of other compounds. Some clinical benefits attributed to inhibitors of HMG-CoA reductase are now thought to be independent of any serum cholesterol-lowering effect. Here we describe a new cholesterol-independent role for HMG-CoA reductase, in regulating a developmental process: primordial germ cell migration. We show that in Drosophila this enzyme is highly expressed in the somatic gonad and that it is necessary for primordial germ cells to migrate to this tissue. Misexpression of HMG-CoA reductase is sufficient to attract primordial germ cells to tissues other than the gonadal mesoderm. We conclude that the regulated expression of HMG-CoA reductase has a critical developmental function in providing spatial information to guide migrating primordial germ cells.

BackgroundClaims about the environmental benefits of charring biomass and applying the resulting “biochar” to soil are impressive. If true, they could influence land management worldwide. Alleged benefits include increased crop yields, soil fertility, and water-holding capacity; the most widely discussed idea is that applying biochar to soil will mitigate climate change. This claim rests on the assumption that biochar persists for hundreds or thousands of years, thus storing carbon that would otherwise decompose. We conducted a systematic review to quantify research effort directed toward ten aspects of biochar and closely evaluated the literature concerning biochar's stability.FindingsWe identified 311 peer-reviewed research articles published through 2011. We found very few field studies that addressed biochar's influence on several ecosystem processes: one on soil nutrient loss, one on soil contaminants, six concerning non-CO2 greenhouse gas (GHG) fluxes (some of which fail to support claims that biochar decreases non-CO2 GHG fluxes), and 16–19 on plants and soil properties. Of 74 studies related to biochar stability, transport or fate in soil, only seven estimated biochar decomposition rates in situ, with mean residence times ranging from 8 to almost 4,000 years.ConclusionsOur review shows there are not enough data to draw conclusions about how biochar production and application affect whole-system GHG budgets. Wide-ranging estimates of a key variable, biochar stability in situ, likely result from diverse environmental conditions, feedstocks, and study designs. There are even fewer data about the extent to which biochar stimulates decomposition of soil organic matter or affects non-CO2 GHG emissions. Identifying conditions where biochar amendments yield favorable GHG budgets requires a systematic field research program. Finally, evaluating biochar's suitability as a climate mitigation strategy requires comparing its effects with alternative uses of biomass and considering GHG budgets over both long and short time scales.

The ADP-ribosylation factor (ARF) family is one of four subfamile of the RAS superfamily of low molclar weight GTP-blning proteins (G proteins). Highly degenerate ogueotides encoding two conserved regions were used in a PCR reacion to amplify cDNAs encoin each ofthe known ARF proteins and eight addit cDNA ments encoding previously unr d human members ofthe ARF family. Additional sequences were obtained from yeast or fly lbraries by using this tcie. These oligonudeotides speficaly amplify members of the ARF family but not the structurally related G protein a subunits or members of the other three subamilies of the RAS suerfamily. Fragments obtained by PCR were used to obtain fuol-length sequences encoding highly homologous ARF-like (ARL) gene products from human and Drosophila melanogaster libraries, termed ARL2 and Arl84F, respectively. The encoded proteins are each 184 amino acids long and are 76% identical, with 40-45% identiy to human ARF1 and Drosophila arf-like (ard) proteins. These genes appear to be generally expressed in human tisues and during Drosophila development. The purified human ARL2 protein differed in several biochemical properties from human ARF proteins, including the complete absence of ARF activity. Thus, the ARF family of low molecular welght GTP-bindng proteins includes at least 15 distinct but structurally conserved members, including both the functionally conserved ARF proteins and the functionally disparate ARL proteins. The latter proteins currently comprise two distinct gene products in Drosophila (arl and ARI4F) and one in man (ARL2).

E. 2004. Primary productivity and species richness: relationships among functional guilds, residency groups and vagility classes at multiple spatial scales. Á/ Ecography 27: 207 Á/217.One of the major determinants of species richness is the amount of energy available, often measured as primary productivity. Heterogeneity of environmental variables has also been found to influence species richness. Predicting species distributions across landscapes and identifying areas that have high species richness, or vulnerable groups of species, is useful for land management. Remotely sensed data may help identify such areas, with the Normalized Difference Vegetation Index (NDVI) providing an estimate of primary productivity. We examined the relationship between maximum productivity (NDVI), heterogeneity of productivity, and species richness of birds and butterflies at multiple spatial scales. We also explored relationships between productivity, functional guilds and residency groups of birds, and vagility classes of butterflies. Positive linear relationships between maximum NDVI and number of functional guilds of birds were found at two spatial scales. We also found positive linear relationships between maximum NDVI and species richness of neotropical migrant birds at two scales. Heterogeneity of NDVI, by contrast, was negatively associated with number of functional guilds of birds and species richness of resident birds. Maximum NDVI was associated with species richness of all butterflies and of the most vagile butterflies. No association was found between heterogeneity of NDVI and species richness of butterflies. In the Great Basin, where high greenness and availability of water correspond to areas of high species richness and maximum NDVI, our results suggest that NDVI can provide a reliable basis for stratifying surveys of biodiversity, by highlighting areas of potentially high biodiversity across large areas. Measures of heterogeneity of NDVI appear to be less useful in explaining species richness.

Gonad formation requires specific interactions between germ cells and specialized somatic cells, along with the elaborate morphogenetic movements of these cells to create an ovary or testis. We have identified mutations in the fear of intimacy (foi) gene that cause defects in the formation of the embryonic gonad in Drosophila. foi is of particular interest because it affects gonad formation without affecting gonad cell identity, and is therefore specifically required for the morphogenesis of this organ. foi is also required for tracheal branch fusion during tracheal development. E-cadherin/shotgun is similarly required for both gonad coalescence and tracheal branch fusion, suggesting that E-cadherin and FOI cooperate to mediate these processes. foi encodes a member of a novel family of transmembrane proteins that includes the closely related human protein LIV1. Our findings that FOI is a cell-surface protein required in the mesoderm for gonad morphogenesis shed light on the function of this new family of proteins and on the molecular mechanisms of organogenesis.

As part of a large project to determine rooting depth and resource uptake on the Edwards Plateau of central Texas, we developed a DNA-based technique that allows the below-ground parts of all plants to be identified to the level of genus and usually to species. Identification is achieved by comparing DNA sequences of the internal transcribed spacer (ITS) region of the 18S-26S nuclear ribosomal DNA repeat, derived from below-ground plant material, with a reference ITS region database for plants at a site. The method works throughout plants because the plant ITS region can be PCR amplified using a set of universal primers. Congeneric species can usually be identified because the ITS region evolves relatively rapidly. In our study, all roots were easily identified to the level of genus; most congeneric species were identified solely by ITS sequence differences but some required a combination of ITS sequence data and above-ground surveys of species at a site. In addition to showing the feasibility and efficacy of our technique, we compare it with another DNA-based technique used to identify below-ground plant parts. Finally, we also describe a DNA extraction and purification technique that reliably provides high-quality DNA of sufficient quantity from roots so that PCR can be readily accomplished. Our technique should allow the below-ground parts of plants in any system to be identified and thereby open new possibilities for the study of below-ground plant communities.