Preliminary studies on the large-scale geomorphic patterns of the complex longitudinal sand ridge zone in the Taklimakan Desert

Through analysis of satellite images from Google Earth, this article expounds the characteristics of large-scale geomorphic patterns of the complex longitudinal sand ridge zone in the Taklimakan Desert, and reduces the large-scale geomorphic patterns to six types: parallel pattern, "(sic)" character-shaped and "(sic)" character-shaped pattern, comb-shaped pattern, fork-shaped pattern, toe-shaped pattern and miscellaneous pattern. And according to the large-scale geomorphic pattern type (or composition of pattern types) as well as some other factors, the article divides the complex longitudinal sand ridge zone into 55 subzones. Lastly, aiming at the genetic problems of the large-scale geomorphic patterns, the article suggests three connective types of the sand ridges in the complex longitudinal sand ridge zone, i.e., connecting or intersecting after natural elongation, connecting in a narrow place and connecting with the aid of intermediary

The social and environmental costs associated with water management practices in state environmental protection projects in Xinjiang, China

Since the late 1970s the central government of China has initiated several ecological environmental protection projects. The most significant of these has been the tui geng huan lin (returning cultivated land to forest and pasture) project in operation since the late 1990s. China's northwest region is characterized by lack of water resources, yet such resources are of vital importance. There is scant discussion in the literature (including in China) on the linkages between the environmental protection projects and water management practices. This paper analyses how central government environmental protection projects are interpreted in the local setting, and how local water management policies and practices correspond to the projects. The conclusion is that local water management policies and practices are interlinked with both central government and local government policies on the environmental protection projects, and a new process for the redistribution of water has been established. When equity and social costs are not factored into the planning of new environmental protection projects, the social costs may be as high as the environmental costs. (C) 2009 Elsevier Ltd. All rights reserved

Evaluating the performance of PC-ANN for the estimation of rice nitrogen concentration from canopy hyperspectral reflectance

In this study, a wide range of leaf nitrogen concentration levels was established in field-grown rice with the application of three fertilizer levels. Hyperspectral reflectance data of the rice canopy through rice whole growth stages were acquired over the 350 nm to 2500 nm range. Comparisons of prediction power of two statistical methods (linear regression technique (LR) and artificial neural network (ANN)), for rice N estimation (nitrogen concentration, mg nitrogen g(-1) leaf dry weight) were performed using two different input variables (nitrogen sensitive hyperspectral reflectance and principal component scores). The results indicted very good agreement between the observed and the predicted N with all model methods, which was especially true for the PC-ANN model (artificial neural network based on principal component scores), with an RMSE 0.347 and REP 13.14%. Compared to the LR algorithm, the ANN increased accuracy by lowering the RMSE by 17.6% and 25.8% for models based on spectral reflectance and PCs, respectively

Plants water status of the shelterbelt along the Tarim Desert Highway

The plant water consumption and irrigation management are the core issue of the sustainable growing of the Tarim Desert Highway shelterbelt in the hyperaride Taklimakan Desert. The stem sap flow, water status and water consumption of shelterbelt plants were studied, then, the issue of the water save in the process of shelterbelt irrigation management was discussed by measuring the sap flow of shelterbelt plants with a stem sap flow gauge. The stem sap flow exhibited a distinct diurnal course with maximum values between 10:00 and 15:00, and minimum values between 00:00 and 03:00. Generally, sap flow was lower at night than during the day. The daily average stem sap flow of Calligonum arborescens, Tamarix ramosissima and Haloxylon ammodendron (diameter 1.9-2.0 cm) was 67.2 g.h(-1), 77.05 g.h(-1) and 61.54 g.h(-1) respectively. The sap flow was influenced by environmental factors, and the solar radiation, wind velocity, temperature and relative humidity were significantly correlative with plant stem sap flow. The annual water consumption of 8-a Calligonum arborescens, Tamarix ramosissima and Haloxylon ammodendron was 1937.80 kg, 1253.39 kg and 1026.96 kg, while daily average water consumption was 9.69 kg, 6.27 kg and 5.13 kg respectively. Under drip irrigation, soil moisture content of the shelterbelt in different months indicated no obvious fluctuation, and soil moisture was adequate. The predawn and midday plant water potential reflected that the plant water status was in good conditions. There is still some water-saving space if optimizing the present water management, integrating water resources conservation and protection performance

Adaptive growth of Tamarix taklamakanensis root systems in response to wind action

Root distribution and characteristics were investigated on a 70-year-old Tamarix taklamakanensis individual through uprooting. Rooting depth was restricted by water table, and root morphology adapted to resist the wind movement associated with shallow rooting. Root systems had more structural root mass and length on the leeward side than the windward side of the tree relative to the prevailing wind direction. Additional resistance to wind bending can occur as a result of increased thickening of the lower stem along the axis of the prevailing wind direction, and in T taklamakanensis, this thickening is greater on the lee side of the stem. We conclude that increased root distribution and thickening of the lower stem on the leeward are an important strategy for T taklamakanensis in response to wind action in the hinterland of Taklimakan Desert

The vertical distribution of the root system of the desert highway shelterbelt in the hinterland of the Taklimakan Desert

In this work, the vertical distribution of the root system in the Tarim Desert Highway shelterbelt under high salinity water drip irrigation was investigated. The effect of site condition and shelterbelt age was studied. The root sample was collected by plant side soil column excavation. The root distribution was found to be dependent on soil texture, aspect, and plant age. In harden sand, the roots were mostly in the 0-40 cm soil. The root distribution is deep in flat sandy ground and ridge sand. In unit soil volume, the root weight of flat sandy ground was the highest. Compared with the shady slope, the sunny slope had much high total root weight, deeper root distribution, but less hair root. The root weight increased rapidly with the increase of the shelterbelt ages, and the most substantial increase was observed in the early years after forest implantation

Combining system dynamic model and CLUE-S model to improve land use scenario analyses at regional scale: A case study of Sangong watershed in Xinjiang, China

Uses of models of land use change are primary tools for analyzing the causes and consequences of land use changes, assessing the impacts of land use change on ecosystems and supporting land use planning and policy. However, no single model is able to capture all of key processes essential to explore land use change at different scales and make a full assessment of driving factors and impacts. Based on the multi-scale characteristics of land use change, combination and integration of currently existed models of land use change could be a feasible solution. Taken Sangong watershed as a case study, this paper describes an integrated methodology in which the conversion of land use and its effect model (CLUE), a spatially explicit land use change model, has been combined with a system dynamic model (SD) to analyze land use dynamics at different scales. A SD model is used to calculate area changes in demand for land types as a whole while a CLUE model is used to transfer these demands to land use patterns. Without the spatial consideration, the SD model ensures an appropriate treatment of macro-economic, demographic and technology developments, and changes in economic policies influencing the demand and supply for land use in a specific region. With CLUE model the land use change has been simulated at a high spatial resolution with the spatial consideration of land use suitability, spatial policies and restrictions to satisfy the balance between land use demand and supply. The application of the combination of SD and CLUE model in Sangong watershed suggests that this methodology have the ability to reflect the complex behaviors of land use system at different scales to some extent and be a useful tool for analysis of complex land use driving factors such as land use policies and assessment of its impacts on land use change. The established SD model was fitted or calibrated with the 1987-1998 data and validated with the 1998-2004 data; combining SD model with CLUE-S model, future land use scenarios were analyzed during 2004-2030. This work could be used for better understanding of the possible impacts of land use change on terrestrial ecosystem and provide scientific support for land use planning and managements of the watershed. (C) 2010 Elsevier B.V. All rights reserved

Pollen brush of Astragalus L. subgenus Pogonophace Bunge (Leguminosae) and its systematic significance

The style morphologies of Astragalus subgenus Pogonophace (Leguminosae) were examined using the scanning electron microscope. The results showed that in most species, there are erect and upwardly pointed trichomes on the style. This kind of structure is exactly a pollen brush. The style of A. craibianus Simps. is glabrous, and there are finger-like projections formed by the epidermal cells only on the stigma. A. hoantchy Franch. has a penicillate stigma. The three types of styles are not homologous. These supported the exclusion of sect. Sesbanella and A. craibianus from Pogonophace. In molecular studies, some Pogonophace species are nested within the Coluteinae clade. This study found that those species rightly have the structure of pollen brush. Therefore, the pollen brush is likely to be a synapomorphy of Pogonophace and Coluteinae. The close relationship between Pogonophace and subtribe Coluteinae (tribe Galegeae) can be supported by the pollen brush

Photosynthesis responses of endemic shrubs of Taklimakan Desert to adverse temperature, humidity and radiation

Under the native habitat conditions, the seasonal gas exchange characteristics of two natural endemic plant species, Calligonum taklimakanensis B.R. Pan & GM. Shen and Tamarix taklamakanensis M.T. Liu, which are located in the hinterland of the Taklimakan Desert, are measured and compared by Li-6400 photosynthesis system. The results indicate that temperature (degrees C), solar radiation (PAR), soil water content (SWC), and other environmental factors have obvious seasonal variations and the gas exchange characteristics of two plants have different changes in different growing seasons. For C. taklimakanensis, both in July and September, its daily changes of net photosynthetic rate tend to be obvious double peak curve, but in July its peak appeared earlier. Besides its maximum net photosynthetic rate (P-max), apparent quantum efficiency (Phi), range of effective photosynthetic radiation significantly less than that in September. Moreover, its water use efficiency (WUE) in July was also lower than that in September due to the higher transpiration rate (T-r). For T. taklamakanensis, although its daily change of net photosynthetic rate is a single peak curve in September, its peak time has not changed, and except that its WUE is higher in September like C. taklimakanensis, the maximum net photosynthetic rate (P-max), apparent quantum efficiency (Phi), light saturation point, and range of effective photosynthetic radiation has not changed or slightly declined. That is to say C. taklimakanensis select a season that habitat was better (like September) to progress relative effectively photosynthesis accumulation, in contrast, T. taklamakanensis still keep a relatively stable photosynthesis rate in different growth seasons. The difference of gas exchange characteristics of the two plants in different seasons shows that adaptation strategies of the two plants to extreme conditions in desert are different. Besides, both the higher photosynthetic accumulation rate and the higher water use efficiency in September also indicate that these two endemic desert shrubs possess the abilities and strategies to make the best of limited natural resources

Evolutionary response of Caragana (Fabaceae) to Qinghai-Tibetan Plateau uplift and Asian interior aridification

Caragana is endemic to temperate Asia, with most species distributed on the Qinghai-Tibetan Plateau (QTP) and in Northwestern China. Consequently its biogeography should be hypothesized to have been affected by QTP uplift. To examine the biogeography of Caragana in relation to QTP uplift and consequent interior aridification, we conducted molecular dating analyses based on three genes (ITS, cpDNA trnS-trnG and rbcL). Results from relaxed Bayesian BEAST, relaxed Bayesian Multidivtime, and PL (penalized likelihood) indicate that QTP uplift, especially the onset of Himalayan motion at 21-17 Ma, triggered the origin of Caragana (with estimated ages 16-14 Ma). The subsequent QTP rapid uplift at 8 Ma is inferred to have driven the evolution and diversification of the three major clades of Caragana: section Caragana (northern China and the Junggar-Altai-Sayan region), section Frutescentes (Central Asia), and sections Bracteolatae and Jubatae, centered in the QTP. A rapid and active speciation process occurring in the QTP intense uplift at 3.4-1.8 Ma, is indicated by the chronogram