Non‐methane hydrocarbons (NMHCs) play very important roles in atmospheric chemistry, yet little is known about their abundance in the atmosphere of China, especially in the background atmospheres. Measurements of C2‐C10 NMHCs were concurrently carried out at two remote background sites and one rural background site in April and May 2004 in this study: Tengchong Mountain (TM) in Yunnan province on the border of southwestern China; Jianfeng Mountain (JM) on the southwest coast of Hainan Island, southern China; and Lin'an (LA) in Zhejiang province in eastern China. Additional samples were collected at an urban site, Tengyue Town (TT, about 10 km from TM), to obtain local urban NMHC profiles. NMHC levels in these background sites were compared with other rural and remote sites in Asia and other global background stations. In the urban site of TT, local biofuel combustion was the major contributor to the high levels of ethene, ethyne, and ethane. In LA, the major sources of NMHCs were the emissions from fossil fuel and biofuel combustion and from industrial solvent use. Compared with another study conducted in 2001, toluene levels had increased by 75% in 2004 in this study, whereas the levels of other anthropogenic hydrocarbons remained at the same levels. Local industrial emissions and transports from the Yangtze River Delta were the major sources of toluene, ethylbenzene, and xylenes in LA. While in TM, the major sources were regional biofuel combustions and biomass burning emissions from Southeast Asia. Long‐range transport of air masses from Southeast Asia was the major source of NMHCs in JM in spring. JM showed the lowest levels of most hydrocarbons among the three background sites. Several hydrocarbon molar ratios, such as benzene/toluene and ethane/propane, were used to characterize the signatures of air masses from different regions.

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1. Interspecific root separation is an important example of spatial niche differentiation that drives species coexistence in many ecosystems. Particularly under water-stressed conditions, it is believed to be an inevitable outcome of species interactions. However, evidence for and against this idea has been found. So far, studies aiming at reconciling the debate have mainly focused on abiotic determinants. It remains unclear if and to what extent root separation depends on the type and growth form of interacting plants. 2. We conducted a detailed field study in three adjacently located (with pairwise distances <500 m) arid patchy communities where a common tussock grass species Achnatherum splendens grew in association with either a tree Elaeagnus angustifolia, a shrub Nitraria tangutorum or a perennial forb species Sophora alopecuroides. In each community, roots and soils were sampled along the soil layers from five depths (0-10, 10-30, 30-60, 60-100 and 100-150 cm) in the patches and in the adjacent bare ground outside the patches. 3. Significant vertical interspecific root separation occurred in the species-association patches of tree-grass and forb-grass communities, but not in the shrub-grass community. As the neighbour changed going from trees to shrubs and to forbs, rooting profiles of the grass Achnatherum became progressively deeper, with progressively less roots allocated in the upmost 10 cm soil layer and more in the subsequent two layers. After controlling for the differences in soil water and nutrient conditions among the three communities, the effects of neighbour type on grass rooting profiles remained robust. 4. Synthesis. We found that the root distributions of plants in the dryland strongly depend on the type of neighbour plants, which can, at least partially, determine the extent of interspecific root separation at the community scale. Our work poses new questions about plasticity in root distribution and helps to better understand species interactions and coexistence under stressful conditions.

[1] Nonmethane hydrocarbons (NMHCs) were investigated in a clean remote tropical rain forest site of Jianfengling Natural Reserve in Hainan Island in spring, autumn and early winter of 2004. The aim was to characterize air pollution transported from east Asia and SE Asian subcontinent on this relatively undeveloped region of south China. Ethane, ethyne, isoprene and ethene are the most abundant hydrocarbons. The relative contributions of pollution transport from urban and industrial zones of east Asia and agricultural zones of SE Asia are discussed with the help of backward air trajectories. The air masses from the SE Asian biomass burning region contained higher concentrations of ethane and ethyne while air masses traveling through coastal east China contained higher concentrations of ethene and toluene in addition to ethane and ethyne. It was found that anthropogenic emissions transported from the SE and south China developed and developing regions in autumn had a higher input than biomass burning emission from SE Asia in spring. Local biogenic emission was deduced to be the major source of isoprene. Hydrocarbon concentration ratios were found to be good indicators for identification of inflow air masses from different source regions.

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Abstract:Lianas are important components of tropical forests and have significant impacts on the diversity, structure and dynamics of tropical forests. The present study documented the liana flora in a Chinese tropical region. Species richness, abundance, size-class distribution and spatial patterns of lianas were investigated in three 1-ha plots in tropical seasonal rain forests in Xishuangbanna, SW China. All lianas with ≥ 2 cm diameter at breast height (dbh) were measured, tagged and identified. A total of 458 liana stems belonging to 95 species (ranging from 38 to 50 species/ha), 59 genera and 32 families were recorded in the three plots. The most well-represented families were Loganiaceae, Annonceae, Papilionaceae, Apocynaceae and Rhamnaceae. Papilionaceae (14 species recorded) was the most important family in the study forests. The population density, basal area and importance value index (IvI) varied greatly across the three plots. Strychnos cathayensis, Byttneria grandifolia and Bousigonia mekongensis were the dominant species in terms of IvI across the three plots. The mean aboveground biomass of lianas (3 396 kg/ha) accounted for 1.4% of the total community aboveground biomass. The abundance, diversity and biomass of lianas in Xishuangbanna tropical seasonal rain forests are lower than those in tropical moist and wet forests, but higher than those in tropical dry forests. This study provides new data on lianas from a geographical region that has been little-studied. Our findings emphasize that other factors beyond the amount and seasonality of precipitation should be included when considering the liana abundance patterns across scales. Rev. Biol. Trop. 57 (1-2): 211-222. Epub 2009 June 30.Key words: biodiversity, liana abundance, liana biomass, species richness, tropical forests.The woody climbing plants, lianas, are important components of tropical forests. They typically rely on other plants for mechanical support and are abundant, diverse, and make a significant contribution (10-25%) to the overall plant diversity in the tropical forests (Gentry and Dodson 1987, Nabe-Nielsen 2001). Before the 1980s, limited attention is paid to lianas in the tropical forest. Recent years, however, more and more studies about lianas have been conducted due to the awareness of the important role of lianas in the tropical forest ecosystems (Schnitzer 2005, Gerwing et al. 2006. Even though, the ecology of lianas in most forests is still poorly understood (Mascaro et al. 2004).Lianas have been found to play a vital role in many aspects of forest ecosystem dynamics and functioning, including reducing treegrowth rates (Putz 1984), suppressing tree regeneration , providing valuable food sources for insects and animals (Nabe-Nielsen 2001), physically linking trees together and thereby increasing community stability and providing canopy-to-canopy access for arboreal animals (Schnitzer and Bongers 2002). However, we still have only a vague idea of the liana composition of most tropical forests and know little about the role th...