Potential impacts of climate change on nitrogen transformations and greenhouse gas fluxes in forests: a soil transfer study

Relatively little research has been conducted on how climate change may affect the structure and function of arid to semiarid ecosystems of the American Southwest. Along the slopes of the San Francisco Peaks of Arizona, USA, I transferred intact soil cores from a spruce‐fir to a ponderosa pine forest 730 m lower in elevation to assess the potential impacts of climate change on soil N cycling and trace gas fluxes. The low‐elevation site has a mean annual soil temperature about 2.5°C higher than the high‐elevation site. Net rates of N transformations and trace gas fluxes were measured in high‐elevation soil cores incubated in situ and soil cores transferred to the low‐elevation site. Over a 13‐month period, volumetric soil water content was similar in transferred soil cores relative to soil cores incubated in situ. Net N mineralization and nitrification increased over 80% in transferred soil cores compared with in situ soil cores. Soil transfer significantly increased net CO₂ efflux (120%) and net CH₄ consumption (90%) relative to fluxes of these gases from soil cores incubated in situ. Soil net N₂O fluxes were relatively low and were not generally altered by soil transfer. Although the soil microbial biomass as a whole decreased in transferred soil cores compared with in situ soil cores after the incubation period, active bacterial biomass increased. Transferring soil cores from the low‐elevation to the high‐elevation site (i.e. simulated global cooling) commonly, but not consistently, resulted in the opposite effects on soil pools and processes. In general, soil containment (root trenching) did not significantly affect soil measurements. My results suggest that small increases in mean annual temperature can have large impacts on soil N cycling, soil–atmosphere trace gas exchanges, and soil microbial communities even in ecosystems where water availability is a major limiting resource.     

Coral bleaching, reef fish community phase shifts and the resilience of coral reefs

The 1998 global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. Annual censuses of reef fish community structure over a 12-year period spanning the bleaching event revealed a marked phase shift from a prebleach to postbleach assemblage. Surprisingly, we found that the bleaching event had no detectable effect on the abundance, diversity or species richness of a local cryptobenthic reef fish community. Furthermore, there is no evidence of regeneration even after 5–35 generations of these short-lived species. These results have significant implications for our understanding of the response of coral reef ecosystems to global warming and highlight the importance of selecting appropriate criteria for evaluating reef resilience.     

《昆明-蒙特利尔全球生物多样性框架》核心目标与我国的保护行动建议

在中国作为主席国的引领下,联合国《生物多样性公约》(以下简称《公约》)第十五次缔约方大会(以下简称COP15)第二阶段会议通过了62项决定,特别是达成了以变革理论为基础的《昆明-蒙特利尔全球生物多样性框架》(以下简称《昆蒙框架》),为全球生物多样性治理擘画了新的蓝图。该文就《昆蒙框架》的三个核心目标——保护地“3030目标”、资源调动、遗传资源数字序列信息进行解读,对保障《昆蒙框架》落地的相关决议进行简要介绍,并就我国未来的保护行动提出了相关建议:(1)加强生物多样性保护的主流化;(2)进一步制定详细的保护计划,明确保护区域的范围、目的和管理措施,并落实实施计划的责任部门和具体措施;(3)根据框架目标的监测要求,制定可操作的指标体系和监测计划;(4)继续加强生物多样性保护的意识和教育,提高公众对生物多样性保护的认识和重视程度,促进全社会的可持续生产和可持续消费;(5)大力推进国际合作,在更大尺度上探索和促进基于自然的解决方案,寻找对自然产生正面、积极效果的经济和社会发展路径。     

Viability analysis of endangered crayfish populations

The noble crayfish Astacus astacus L. is a threatened freshwater invertebrate. Many of the remaining populations are isolated and there is considerable concern that diseases and the increased frequency of flooding events may drive these remnant populations to extinction. We performed a population viability analysis for a typical isolated noble crayfish population. We quantified the extinction risk by the mean time to extinction within 1000 years for several scenarios (flooding events, restocking of adults). For a set of parameters derived from field estimates, we estimated the mean time to extinction to be 240 years. However, the median was only 80 years. Multiple sensitivity analysis by logistic regression revealed that spawning probability, juvenile and adult mortality were the important parameters for the survival of the population. The mean time to extinction decreased with increasing frequency of floodings. This is alarming, considering the magnitude of the effect and the expectation of an increasing number of floodings with global warming. Restocking, however, was found to have only a minor effect on the mean time to extinction. Overall, our simulations suggested that for the long-term and self-sustaining survival of the noble crayfish, particularly where they remain isolated, we have to improve the extent and quality of habitats. Nevertheless, additional measures are necessary, especially the removal of dispersal barriers to allow some exchange of individuals between populations. However, this also calls for a control of invasive crayfish species.     

Recent decline in precipitation and tree growth in the eastern Mediterranean

We present evidence of a recent drying in the eastern Mediterranean, based on weather and tree‐ring data for Samos, an island of the eastern Aegean Sea. Rainfall declined rapidly after the late 1970s following trends for the entire Mediterranean and was associated with reduced tree‐ring width in Pinus brutia. The most recent decline led to the lowest annual radial stem increment after the last 100 years (as far as records reach). As moisture availability decreased best correlations of tree growth with rainfall were obtained for progressively longer integration periods (1–2 years in moister periods, 5–6 years during the severe dryness of 20th century's last decades), suggesting increasing dependency in deep soil water. Such long‐term integration periods of tree‐growth responses to precipitation have not been reported before. They may reflect a tree‐rooting pattern adapted to cope with even several successive dry years. In late summer 2000, moisture reserves became exhausted, however, and a substantial fraction of low altitude pines died, including some 80‐year‐old trees, which underlines the exceptional extent this trend had reached. Our findings provide empirical support for Intergovernmental Panel on Climate Change projections derived from global circulation models that the Mediterranean, its eastern basin in particular, should become drier as temperature rises, as was the case in the recent past.     

Man-made environmental changes affect the boundary between two taxa of Laudakia

This project tested whether, and how, man-made changes in the environment would affect the boundary between parapatric-related taxa of Laudakia ( Reptilia: Agamidae ), whose distributions meet at a boundary between ecological regions. Israel is ecologically diverse with a mesic (Mediterranean) north and an arid (Saharo-Arabian) south. The lizard hardun Laudakia stellio is represented in Israel mainly by two subspecies: the Mediterranean Lau . s . ssp. and the desert Lau. s. brachydactyla . These are conventionally distinguished by the key character, number of subdigital lamellae under the fourth toe, visible in museum specimens examined for the purpose. The results revealed that during 1935–1978, the boundary between the two subspecies had shifted 15 km southwards. This is interpreted as resulting from the documented southwards spread of irrigated agriculture. During this time, the average subdigital count of each subspecies near the inter-taxa boundary shifted slightly towards the average of the other subspecies. In each subspecies, in this area, at the same time, the coefficient of variation of the subdigital count increased. The last two processes are interpreted as reflecting reciprocal migration, enhanced by the documented expanded road system and intensified human transportation. Hence, in this case, anthropogenic developments have changed both the location and the genetic structure of the boundary between two parapatric taxa.     

The Knox method and other tests for space-time interaction

The Knox method, as well as other tests for space-time interaction, are biased when there are geographical population shifts, i.e., when there are different percent population growths in different regions. In this paper, the size of the population shift bias is investigated for the Knox test, and it is shown that it can be a considerable problem. A Monte Carlo method for constructing unbiased space-time interaction tests is then presented and illustrated on the Knox test as well as for a combined Knox test. Practical implications are discussed in terms of the interpretation of past results and the design of future studies.     

Temporal Duration and Event Size Distribution at the Epidemic Threshold

The epidemic event, seen as a nonequilibrium dynamic process, is studied through a simple stochastic system reminiscent of the classical SIR model. The system is described in terms of global and local variables and was mainly treated by means of Monte Carlo simulation; square lattices N×N, with N=23, 51, 100, 151, and 211 were used. Distinct extensive runs were performed and then classified as corresponding to epidemic or non-epidemic phase. They were examined with detail through the analysis of the event duration and event size; illustrations, such as density-like plots in the space of the model's parameters, are provided. The epidemic/non-epidemic phase presents smaller/larger relative fluctuations, whereas closer to the threshold the uncertainty reaches its highest values. Far enough from the threshold, the distribution (t) of the events time duration t shows a step-like appearance. However at the threshold line it shows an exponential behavior of the form (t) exp (-t); the same behavior is observed for the event size distribution. These results help to explain why the approach to epidemic threshold would be hard to anticipate with standard census data.     

Random-coil chemical shifts of phosphorylated amino acids

The ¹H, ¹³C, ¹⁵N and ³¹ P random-coil chemical shifts and phosphate pK_a values of the phosphorylated amino acids pSer, pThr and pTyr in the protected peptide Ac-Gly-Gly-X-Gly-Gly-NH₂ have been obtained in water at 25°C over the pH range 2 to 9. Analysis of ROESY spectra indicates that the peptides are unstructured. Phosphorylation induces changes in random-coil chemical shifts, some of which are comparable to those caused by secondary structure formation, and are therefore significant in structural analyses based on the chemical shift.