Norikazu Yamanaka

Phylogeography of Quercus variabilis Based on Chloroplast DNA Sequence in East Asia: Multiple Glacial Refugia and Mainland-Migrated Island Populations

The biogeographical relationships between far-separated populations, in particular, those in the mainland and islands, remain unclear for widespread species in eastern Asia where the current distribution of plants was greatly influenced by the Quaternary climate. Deciduous Oriental oak (Quercus variabilis) is one of the most widely distributed species in eastern Asia. In this study, leaf material of 528 Q. variabilis trees from 50 populations across the whole distribution (Mainland China, Korea Peninsular as well as Japan, Zhoushan and Taiwan Islands) was collected, and three cpDNA intergenic spacer fragments were sequenced using universal primers. A total of 26 haplotypes were detected, and it showed a weak phylogeographical structure in eastern Asia populations at species level, however, in the central-eastern region of Mainland China, the populations had more haplotypes than those in other regions, with a significant phylogeographical structure (N ST = 0.751> G ST = 0.690, P<0.05). Q. variabilis displayed high interpopulation and low intrapopulation genetic diversity across the distribution range. Both unimodal mismatch distribution and significant negative Fu’s FS indicated a demographic expansion of Q. variabilis populations in East Asia. A fossil calibrated phylogenetic tree showed a rapid speciation during Pleistocene, with a population augment occurred in Middle Pleistocene. Both diversity patterns and ecological niche modelling indicated there could be multiple glacial refugia and possible bottleneck or founder effects occurred in the southern Japan. We dated major spatial expansion of Q. variabilis population in eastern Asia to the last glacial cycle(s), a period with sea-level fluctuations and land bridges in East China Sea as possible dispersal corridors. This study showed that geographical heterogeneity combined with climate and sea-level changes have shaped the genetic structure of this wide-ranging tree species in East Asia.

Restoration and development of the degraded Loess Plateau, China

This book presents state-of-the-art scientific evidence and technological innovations to restore lands on the Loess Plateau of China, known worldwide for its serious land degradation and desertification problems. Supported by a rapidly developing Chinese economy and the dissemination of effective technology, the Grain-for-Green Project and Western Development Action launched by the Chinese government have resulted in successful ecological restoration and protection over the past 30 years. These programs have contributed not only to conservation of soil and water, but also to economic development. At the same time, however, these developmental interventions have brought new challenges that have not yet been fully addressed. The book describes (1) case studies of success and failure in practice, including rare success stories of combating desertification; (2) technical issues such as erosion control and breeding of stress-tolerant plant species, and socioeconomic measures taken by the Chinese government and lending policies with support from the World Bank; and (3) comprehensive measures against desertification, such as water and wind erosion, salinization, and deforestation. This volume is recommended for researchers and students above the undergraduate level in diverse fields including soil science, rural engineering, social technology and civil engineering, biology, ecology, climatology, physical and human geography, and developmental economics, among others. It also serves as a valuable resource for engineers, government officials, and NPOs and NGOs involved in afforestation, ecological restoration, combating desertification, disaster prevention, and sustainable rural development.

Identification of Cylindrocladium sp. causing damping-off disease of Japanese black pine ( Pinus thunbergii ) and factors affecting the disease severity in a black locust ( Robinia pseudoacacia )-dominated area

The regeneration of Japanese black pine (Pinus thunbergii) seedlings is inhibited in a black locust (Robinia pseudoacacia)-dominated area. We examined the presence of pathogenic fungi in Japanese black pine seedlings in the area in order to determine the effect of pathogenic fungi on the inhibition of regeneration. When Japanese black pine seedlings were planted in the soil obtained from a black locust-dominated area, all of the seedlings died under low-intensity light conditions, whereas 84% of the seedlings survived in the soil obtained from a Japanese black pine-dominated area under the same light conditions. One fungus was isolated from 48.7% of the dead pine seedlings and was identified as Cylindrocladium pacificum Kang, Crous & Schoch, based on the morphological characteristics, growth, and DNA analysis. This fungus was also isolated from 50% of the dead pine seedlings in 2005 and 66.7% of the seedlings in 2006—both were planted in a black locust-dominated area. The virulence of this fungus increased under high-nitrogen and/or low-intensity light conditions. These results reveal the possibility that the soil eutrophication and shading by the black locust are conducive to a severe damping-off disease and threaten the survival and regeneration of Japanese black pine seedlings.

Variations in the structure of airborne bacterial communities in Tsogt-Ovoo of Gobi desert area during dust events

Asian dust events transport the airborne bacteria in Chinese desert regions as well as mineral particles and influence downwind area varying biological ecosystems and climate changes. However, the airborne bacterial dynamics were rarely investigated in the Gobi desert area, where dust events are highly frequent. In this study, air samplings were sequentially performed at a 2-m high above the ground at the sampling site located in desert area (Tsogt-Ovoo of Gobi desert; Mongolia 44.2304°N, 105.1700°E). During the dust event days, the bacterial cells and mineral particles increased to more than tenfold of concentrations. MiSeq sequencing targeting 16S ribosomal DNA revealed that the airborne bacteria in desert area mainly belonged to the classes Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Bacilli, Alpha-proteobacteria, Beta-proteobacteria, and Gamma-proteobacteria. The bacterial community structures were different between dust events and non-dust events. The air samples collected at the dust events indicated high abundance rates of Alpha-proteobacteria, which were reported to dominate on the leaf surfaces of plants or in the saline lake environments. After the dust events, the members of Firmicutes (Bacilli) and Bacteroidetes, which are known to form endospore and attach with coarse particles, respectively, increased their relative abundances in the air samples. Presumably, the bacterial compositions and diversities in atmosphere significantly vary during dust events, which carry some particles from grassland (phyllo-sphere), dry lake, and sand surfaces, as well as some bacterial populations such as Firmicutes and Bacteroidetes maintain in the atmosphere for longer time.

Land-use types and soil chemical properties influence soil microbial communities in the semiarid Loess Plateau region in China

Similar land-use types usually have similar soil properties, and, most likely, similar microbial communities. Here, we assessed whether land-use types or soil chemical properties are the primary drivers of soil microbial community composition, and how changes in one part of the ecosystem affect another. We applied Ion Torrent sequencing to the bacterial and fungal communities of five different land-use (vegetation) types in the Loess Plateau of China. We found that the overall trend of soil quality was natural forest > plantation > bare land. Dominant bacterial phyla consisted of Proteobacteria (42.35%), Actinobacteria (15.61%), Acidobacteria (13.32%), Bacteroidetes (8.43%), and Gemmatimonadetes (6.0%). The dominant fungi phyla were Ascomycota (40.39%), Basidiomycota (38.01%), and Zygomycota (16.86%). The results of Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA) based on land-use types displayed groups according to the land-use types. Furthermore, the bacterial communities were mainly organized by soil organic carbon (SOC). The fungal communities were mainly related to available phosphorus (P). The results suggested that the changes of land use type generated changes in soil chemical properties, controlling the composition of microbial community in the semiarid Loess Plateau region. The microbial community could be an indicator for soil quality with respect to ecological restoration.

Colonization and community structure of root-associated microorganisms of Sabina vulgaris with soil depth in a semiarid desert ecosystem with shallow groundwater

Arbuscular mycorrhizal fungi (AMF) have been observed in deep soil layers in arid lands. However, change in AMF community structure with soil depth and vertical distributions of the other root-associated microorganisms are unclear. Here, we examined colonization by AMF and dark septate fungi (DSF), as well as the community structure of AMF and endophytic fungi (EF) and endophytic bacteria (EB) in association with soil depth in a semiarid desert with shallow groundwater. Roots of Sabina vulgaris and soils were collected from surface to groundwater level at 20-cm intervals. Soil chemistry (water content, total N, and available P) and colonization of AMF and DSF were measured. Community structures of AMF, EF, and EB were examined by terminal restriction fragment length polymorphism analysis. AMF colonization decreased with soil depth, although it was mostly higher than 50%. Number of AMF phylotypes decreased with soil depth, but more than five phylotypes were observed at depths up to 100 cm. Number of AMF phylotypes had a significant and positive relationship with soil moisture level within 0–15% of soil water content. DSF colonization was high but limited to soil surface. Number of phylotypes of EF and EB were diverse even in deep soil layers, and the community composition was associated with the colonization and community composition of AMF. This study indicates that AMF species richness in roots decreases but is maintained in deep soil layers in semiarid regions, and change in AMF colonization and community structure associates with community structure of the other root-associated microorganisms.

Responses of the carbon and oxygen isotope compositions of desert plants to spatial variation in soil salinity in Central Asia

We examined the isotopic parameters in two C3 species (Artemisia diffusa H. Krasch and Tamarix hispida Willd.) and a C4 species [Haloxylonaphyllum (Minkw.) Iljin.] growing or planted in soils with different levels of salinity in a Central Asian desert. The oxygen isotope ratios of stem water (δ18Ostem) in T. hispida and H. aphyllum distributed in high-salinity zones were similar to the δ18O of artesian water (δ18Oartesian) and different from that in A. diffusa distributed in lower-salinity zones. This indicates that T. hispida and H. aphyllum depend on water with low salinity in the deeper soil layer, whereas A. diffusa depends on water in the shallower soil layer that would be affected by salt accumulation. The carbon isotope composition of leaf organic matter (δ13Com) and oxygen isotope enrichment in leaf organic matter above stem water (Δ18Oom) were lower in A. diffusa than in the other species. The responses of δ13Com and Δ18Oom to soil salinity observed for T. hispida suggest that the species decreased its transpiration rate and increased its intrinsic water-use efficiency in response to increasing soil salinity. The δ13Com and Δ18Oom of H. aphyllum were higher than those of the C3 species, and were not correlated with soil salinity, suggesting that H. aphyllum reduced its salt uptake by decreasing transpiration—even though it was able to access less saline water in the deeper soil layer. These results indicate that the water-use strategy of desert plants in high-salinity environments can be assessed based on their carbon and oxygen isotope ratios.

Vegetation of the Loess Plateau

Natural vegetation on the Loess Plateau has been suffering gradual degradation over a long period, owing to human activities. As a result, hardly any original vegetation remains.

Location, Geology and Landforms of the Loess Plateau

The Loess Plateau is a highland region in north-central China with average elevation about 1,200 m. It has the thickest known loess deposits in the world. Although there are several definitions in the literature for the plateau boundary and area, two definitions are the most commonly reported. The first of these defines the plateau from the standpoint of physical geography. As a large geographical unit, “Loess Plateau” is defined as the highland area with thick loess deposit, covering about 380,000 km2. Another commonly accepted definition, is that of the “Loess Plateau region”, which refers to a larger loess-distribution area with loess landscape and related environmental characteristics, covering about 640,000 km2. Formation of the plateau began about 2.6 million years ago. Information about past global climate change has been derived from samples taken from deep layers of loess deposit. Since loess is highly subject to erosion, a unique morphology has developed in the region. Typical landforms are loess Yuan, Liang, and Mao and various valleys of different erosion magnitudes. Loess hills and gullies are very common and are symbolic landscapes of the plateau region.

Inorganic and organic osmolytes accumulation in five halophytes growing in saline habitats around the Aiding Lake area in Turpan Basin, Northwest China

ABSTRACT Halophytes dominate the plant community in saline soils. Here, osmoregulation via the accumulation of osmolytes is the basic strategy by which plants survive salinity stress. We investigated the accumulation of inorganic and organic osmolytes in the leaves of five halophytes (Tamarix hispida, Halocnemum strobilaceum, Kalidium foliatum, Karelinia caspica, and Phragmites australis) growing in the dry lakebed of Aiding Lake, Xinjiang, China. The succulent euhalophytes (H. strobilaceum and K. foliatum) accumulated large amounts of Na+, whereas other species had low Na+ concentrations. P. australis contained high concentrations of soluble carbohydrates, mainly sucrose, and amino acids, such as proline and alanine. K. caspica accumulated large quantities of mannitol. H. strobilaceum and K. foliatum had high glycine betaine contents. Only T. hispida accumulated γ-butyro betaine, which was found in high concentrations. Our findings indicate that at least four types of osmolytes (carbohydrates, polyols, amino acids, and betaines) function either alone, or in combination in the osmoregulation of these halophytes.