Natural scientists have long recognized that regions with similar climate tend to have similar vegetation. Preliminary observations suggest that shrub steppe communities of the western US and western China may be two such regions with similar annual precipitation, temperature, land use, and vegetation. These cold dry shrub steppes have traditionally been grazed. Despite these similarities, patterns of species dominance are different. Annual species that are rare in China become dominant when introduced to the United States. The objective of this study was to investigate how climate, land use and community structure may explain these patterns of species dominance. Community structure and grazing intensity were measured at 5 sites in each region. This information was combined with a broader review of the literature describing the history of grazing in both basins. Climate was analyzed based on a spatially-gridded, interpolated weather time series (monthly records) and climatological summary (1961–1990 mean conditions) data set from the Climate Research Unit. We found that differences in summer precipitation and winter minimum temperature, land use intensity, and shrub size may all contribute to the dominance of annual species in the Great Basin, particularly Bromus tectorum. In particular, previous work indicates that summer precipitation and winter temperature drive the distribution of Bromus tectorum in the Great Basin. As a result, sites with wet summers and cold springs, similar to the Chinese sites, would not be expected to be dominated by Bromus tectorum. A history of more intense grazing of the Chinese sites, as described in the literature, also is likely to decrease fire frequency, and decreases litter and shrub dominance, all of which have been demonstrated to be important in Bromus tectorum establishment and ultimate dominance. Further research is necessary to determine if other annuals that follow the same pattern of scarcity in the Junggar Basin and dominance in the Great Basin are responding to the same influences.

Although alien and invasive plant species have been researched extensively in the European part of Russia, the situation in Siberia is another matter. Hitherto, alien and invasive species in Siberia have not received much attention because this problem was not especially acute in Siberia. The lack of attention on alien and invasive species in Siberia is attributed to three major reasons: 1) Low vegetative productivity and sparse human populations in the Siberian territory have limited botanical research interest in the area. 2) Severe Siberian climate likely prevents many alien and invasive species from increasing their distribution into Siberia. 3) Most Siberian plant communities have not been human-transformed and thus may be resistant to newcomers. Nevertheless, recent increased economic activities have resulted in increasing plant migration to Siberia, and this process should be monitored. Furthermore, global environmental changes may also have made Siberia more favorable for more alien and invasive species. Currently, research on alien and invasive species has begun in the Altai-Sayan region (Western Siberia) and the Magadan region (Northeastern Asia).

For a long time, forestry primarily had industrial goals. Volume of wood production was the main criterion of forestry efficacy, and thus rapid-growing arboreal species were cultivated in natural forests. More recently, nature protection has become one of forestry’s goals. Unfortunately, some introduced, rapid-growing species became aggressive components of natural ecological systems during the interim. In this paper, we first describe a method that we developed to categorize aggressiveness of invasive arboreal plants in natural forest ecosystems of Kazakhstan. We then apply this new scheme to monitoring data of invasive arboreal plants to provide an insight into the invasion potential of different species in the fruit forests of Southeast Kazakhstan.

The northeastern coast of the Caspian Sea is one of the youngest territories for plant colonization in Kazakhstan, and the flora of the most recent portion of this coastal area, the New Caspian marine plain, was chosen to study phytogeographical characteristics of plant species, especially as related to alien origin and invasive potential. Because of the recent formation of this flora, I expected that a large proportion of the species may be alien and invasive. After compiling a comprehensive species list from previous research, I identified the taxonomic, life form, ecological, and geographical structures of the flora. The area belongs to the northern type of deserts with continental climate and low annual precipitation. Taxonomic and life form structures show that the flora is specific to Central Asian deserts. Ecological structure demonstrates a high percentage of halophytes, which resulted from their adaptation to soil salinity and shallow ground waters that occur throughout the study area. Geoelements of the flora indicate allochtonous properties of the flora (i.e. species derived from areas outside the study area) with a low proportion of native (Caspian) plants. Alien species are estimated to comprise 12%–19% of the flora. Although some species have invasive features, severe arid environmental conditions and high salinity of soils and ground waters decrease invasive capacity of exotic plants. However, a threat of expansion of potentially invasive plants exists in the New Caspian marine plain due to the fast growth of anthropogenic habitats associated with recent oil developments.

Lake surface water temperature (SWT) is an important indicator of lake state relative to its water chemistry and aquatic ecosystem, in addition to being an important regional climate indicator. However, few literatures involving spatial-temporal changes of lake SWT in the Qinghai-Tibet Plateau, including Qinghai Lake, are available. Our objective is to study the spatial-temporal changes in SWT of Qinghai Lake from 2001 to 2010, using Moderate-resolution Imaging Spectroradiometer (MODIS) data. Based on each pixel, we calculated the temporal SWT variations and long-term trends, compared the spatial patterns of annual average SWT in different years, and mapped and analyzed the seasonal cycles of the spatial patterns of SWT. The results revealed that the differences between the average daily SWT and air temperature during the temperature decreasing phase were relatively lar-ger than those during the temperature increasing phase. The increasing rate of the annual average SWT during the study period was about 0.01°C/a, followed by an increasing rate of about 0.05°C/a in annual average air tempera-ture. The annual average SWT from 2001 to 2010 showed similar spatial patterns, while the SWT spatial changes from January to December demonstrated an interesting seasonal reversion pattern. The high-temperature area transformed stepwise from the south to the north regions and then back to the south region from January to December, whereas the low-temperature area demonstrated a reversed annual cyclical trace. The spatial-temporal patterns of SWTs were shaped by the topography of the lake basin and the distribution of drainages.

Relative roles of climate change and human activities in desertification are the hotspot of research on desertification dynamic and its driving mechanism. To overcome the shortcomings of existing studies, this paper selected net primary productivity (NPP) as an indicator to analyze desertification dynamic and its impact factors. In addition, the change trends of actual NPP, potential NPP and HNPP (human appropriation of NPP, the difference between potential NPP and actual NPP) were used to analyze the desertification dynamic and calculate the relative roles of climate change, human activities and a combination of the two factors in desertification. In this study, the Moderate Resolution Imaging Spectroradiometer (MODIS)-Normalised Difference Vegetation Index (NDVI) and meteorological data were utilized to drive the Carnegie-Ames-Stanford Approach (CASA) model to calculate the actual NPP from 2001 to 2010 in the Heihe River Basin. Potential NPP was estimated using the Thornthwaite Memorial model. Results showed that 61% of the whole basin area underwent land degradation, of which 90.5% was caused by human activities, 8.6% by climate change, and 0.9% by a combination of the two factors. On the contrary, 1.5% of desertification reversion area was caused by human activities and 90.7% by climate change, the rest 7.8% by a combination of the two factors. Moreover, it was demonstrated that 95.9% of the total actual NPP decrease was induced by human activities, while 69.3% of the total actual NPP increase was caused by climate change. The results revealed that climate change dominated desertification reversion, while human activities dominated desertification expansion. Moreover, the relative roles of both climate change and human activities in desertification possessed great spatial heterogeneity. Additionally, ecological protection policies should be enhanced in the Heihe River Basin to prevent desertification expansion under the condition of climate change.

Fractal geometry is an important method in soil science, and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors. However, there have been few studies examining soil particle volume fractal dimension in alpine grasslands. To study the volume fractal dimension of soil particles (D) and its relationships with soil salt, soil nutrient and plant species diversity, we conducted an experiment on an alpine grassland under different disturbance degrees: non-disturbance (N0), light disturbance (L), moderate disturbance (M) and heavy disturbance (H). The results showed that (1) Ds varied from 2.573 to 2.635 among the different disturbance degrees and increased with increasing degrees of disturbance. (2) Shannon-Wiener diversity index, Pielou’s evenness index and Margalef richness index reached their highest values at the M degree, indicating that moderate disturbance is beneficial to the increase of plant species diversity. (3) In the L and M degrees, there was a significant positive correlation between D and clay content and a significant negative correlation between D and soil organic matter (SOM). In the H degree, D was significantly and positively correlated with total salt (TS). The results suggested that to a certain extent, D can be used to characterize the uniformity of soil texture in addition to soil fertility characteristics. (4) For the L degree, there was a significant negative correlation between D and the Shannon-Wiener diversity index; while for the M degree, there was a significant negative correlation between D and Pielou’s evenness index.

Most soil respiration measurements are conducted during the growing season. In tundra and boreal forest ecosystems, cumulative, non-growing season soil CO₂ fluxes are reported to be a significant component of these systems’ annual carbon budgets. However, little information exists on soil CO₂ efflux during the non-growing season from alpine ecosystems. Therefore, comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of estimating ecosystem carbon budgets, as well as predicting the response of soil CO₂ efflux to climate changes. In this study, we measured soil CO₂ efflux and its spatial and temporal changes for different altitudes during the non-growing season in an alpine meadow located in the Qilian Mountains, Northwest China. Field experiments on the soil CO₂ efflux of alpine meadow from the Qilian Mountains were conducted along an elevation gradient from October 2010 to April 2011. We measured the soil CO₂ efflux, and analyzed the effects of soil water content and soil temperature on this measure. The results show that soil CO₂ efflux gradually decreased along the elevation gradient during the non-growing season. The daily variation of soil CO2 efflux appeared as a single-peak curve. The soil CO₂ efflux was low at night, with the lowest value occurring between 02:00–06:00. Then, values started to rise rapidly between 07:00–08:30, and then descend again between 16:00–18:30. The peak soil CO₂ efflux appeared from 11:00 to 16:00. The soil CO₂ efflux values gradually decreased from October to February of the next year and started to increase in March. Non-growing season Q₁₀ (the multiplier to the respiration rate for a 10ºC increase in temperature) was increased with raising altitude and average Q₁₀ of the Qilian Mountains was generally higher than the average growing season Q₁₀ of the Heihe River Basin. Seasonally, non-growing season soil CO₂ efflux was relatively high in October and early spring and low in the winter. The soil CO₂ efflux was positively correlated with soil temperature and soil water content. Our results indicate that in alpine ecosystems, soil CO₂ efflux continues throughout the non-growing season, and soil respiration is an impor-tant component of annual soil CO₂ efflux.

Water and nitrogen (N) inputs are considered as the two main limiting factors affecting plant growth. Changes in these inputs are expected to alter the structure and composition of the plant community, thereby influencing biodiversity and ecosystem function. Snowfall is a form of precipitation in winter, and snow melting can recharge soil water and result in a flourish of ephemerals during springtime in the Gurbantunggut Desert, China. A bi-factor experiment was designed and deployed during the snow-covering season from 2009 to 2010. The experiment aimed to explore the effects of different snow-covering depths and N addition levels on ephemerals. Findings indicated that deeper snow cover led to the increases in water content in topsoil as well as density and coverage of ephemeral plants in the same N treatment; by contrast, N addition sharply decreased the density of ephemerals in the same snow treatment. Meanwhile, N addition exhibited a different effect on the growth of ephemeral plants: in the 50% snow treatment, N addition limited the growth of ephemeral plants, showing that the height and the aboveground biomass of the ephemeral plants were lower than in those without N addition; while with the increases in snow depth (100% and 150% snow treatments), N addition benefited the growth of the dominant individual plants. Species richness was not significantly affected by snow in the same N treatment. However, N addition significantly decreased the species richness in the same snow-covering depth. The primary productivity of ephemerals in the N addition increased with the increase of snow depth. These variations indicated that the effect of N on the growth of ephemerals was restricted by water supply. With plenty of water (100% and 150% snow treatments), N addition contributed to the growth of ephemeral plants; while with less water (50% snow treatment), N addition restricted the growth of ephemeral plants.

The implementation of the Grain for Green Program is a great breakthrough in the history of China's ecological environment construction, which can control soil erosion effectively, increase land productivity and improve the ecological environment. To investigate the eco-environmental benefits brought by the Grain for Green Program, the spatiotemporal variations of vegetation cover in the growing season from 2000 to 2010 across the Hekou-Longmen (He-Long) region were analyzed by using remote sensing information, meteorological data and land use data. Moreover, the impacts of climate and human activities on vegetation change were evaluated objectively. Annual vegetation cover in the growing season increased very significantly. Increased vegetation cover occurred in 98.7% of the region, of which the area for vegetation cover improved slightly constituted 79.8% of the whole area. Vegetation moderately improved was mainly distributed in the south of the He-Long region, covering 9.6% of the area, and the area for vegetation basically unchanged concentrated in the middle and upper reaches of the Wuding River. Precipitation was found to be an important natural factor influencing vegetation cover change. The area of vegetation cover showing a significantly positive correlation with precipitation occupied 22.14% of the region. As driven by policies from the Grain for Green Program, forestland increased significantly and land use structure became more intensive. Human activities played a positive and effective role in the protection, restoration and improvement of vegetation in the places where vegetation cover was basically unchanged, even though precipitation declined greatly, and vegetation improved moderately with massive increases of forestland and grassland.

Remote sensing is a valuable and effective tool for monitoring and estimating aboveground biomass (AGB) in large areas. The current international research on biomass estimation by remote sensing technique mainly focused on forests, grasslands and crops, with relatively few applications for desert ecosystems. In this paper, Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper Plus (ETM+) images from 1988 to 2007 and the data of 283 AGB samples in August 2007 were used to estimate the AGB for Mu Us Sandy Land over the past 30 years. Moreover, temporal and spatial distribution characteristics of AGB and influencing factors of climate and underlying surface were also studied. Results show that: (1) Differences of correlations exist in the fitted equations between AGB and different vegetation indices in desert areas. The modified soil adjusted vegetation index (MSAVI) and soil adjusted vegetation index (SAVI) show relatively higher correlations with AGB, while the correlation between normalized difference vegetation index (NDVI) and AGB is relatively lower. Error testing shows that the AGB- MSAVI model established can be used to accurately estimate AGB of Mu Us Sandy Land in August. (2) AGB in Mu Us Sandy Land shows the fluctuant characteristics over the past 30 years, which decreased from the 1980s to the 1990s, and increased from the 1990s to 2007. AGB in 2007 had the highest value, with a total AGB of 3.352×10⁶ t. Moreover, in the 1990s, AGB had the lowest value with a total AGB of 2.328×10⁶ t. (3) AGB with relatively higher values was mainly located in the middle and southern parts of Mu Us Sandy Land in the 1980s. AGB was low in the whole area in the1990s, and relatively higher AGB values were mainly located in the southern parts of Uxin. In 2007, AGB in the whole area was relatively higher than those of the last twenty years, and higher AGB values were mainly located in the northern, western and middle parts of Mu Us Sandy Land.

Riparian vegetation belts in arid regions of Central Asia are endangered to lose their ecosystem ser-vices due to intensified land use. For the development of sustained land use, management knowledge of plant performance in relation to resource supply is needed. We estimated productivity related functional traits at the edges of the habitat of Populus euphratica Oliv. Specific leaf area (SLA) and carbon/nitrogen (C/N) ratio of P. euphratica leaves growing near a former river bank and close to moving sand dunes in the Ebinur Lake National Nature Reserve in Xinjiang, Northwest China (near Kazakhstan) were determined and daily courses of CO₂ net as-similation (PN), transpiration (E), and stomatal conductance (g_s) of two consecutive seasons were measured during July–August 2007 and June–July 2008. Groundwater level was high (1.5–2.5 m below ground) throughout the years and no flooding occurred at the two tree stands. SLA was slightly lower near the desert than at the former river bank and leaves contained less N in relation to C. Highest E and gs of P. euphratica were reached in the morning before noon on both stands and a second low maximum occurred in the afternoon despite of the unchanged high levels of air to leaf water vapor pressure deficit (ALVPD). Decline of gs in P. euphratica was followed by decrease of E. Water use efficiency (WUE) of leaves near the desert were higher in the morning and the evening, in contrast to leaves from the former river bank that maintained an almost stable level throughout the day. High light compensation points and high light saturation levels of P_N indicated the characteristics of leaves well-adapted to intensive irradiation at both stands. In general, leaves of P. euphratica decreased their gs beyond 20 Pa/kPa ALVPD in order to limit water losses. Decrease of E did not occur in both stands until 40 Pa/kPa ALVPD was reached. Full stomatal closure of P. euphratica was achieved at 60 Pa/kPa ALVPD in both stands. E through the leaf surface amounted up to 30% of the highest E rates, indicating dependence on water recharge from the ground despite of obviously closed stomata. A distinct leaf surface temperature (T_leaf) threshold of around 30°C also existed before stomata started to close. Generally, the differences in gas exchange between both stands were small, which led to the conclusion that micro-climatic constraints to E and photosynthesis were not the major factors for declining tree density with increasing distance from the river.

The effect of variation in water supply on woody seedling growth in arid environments remain poorly known. The subshrub Alhagi sparsifolia Shap. (Leguminosae), distributed in the southern fringe of the Taklimakan Desert, Xinjiang, northwestern China, has evolved deep roots and is exclusively dependent on groundwater, and performs a crucial role for the local ecological safety. In the Cele oasis, we studied the responses of A. sparsifolia seedling roots to water supplement at 10 and 14 weeks under three irrigation treatments (none water supply of 0 m³/m² (NW), middle water supply of 0.1 m³/m² (MW), and high water supply of 0.2 m³/m² (HW)). The results showed that the variations of soil water content (SWC) significantly influenced the root growth of A. sparsifolia seedlings. The leaf area, basal diameter and crown diameter were significantly higher in the HW treatment than in the other treatments. The biomass, root surface area (RSA), root depth and relative growth rate (RGR) of A. sparsifolia roots were all significantly higher in the NW treatment than in the HW and MW treatments at 10 weeks. However, these root parameters were significantly lower in the NW treatment than in the other treatments at 14 weeks. When SWC continued to decline as the experiment went on (until less than 8% gravimetric SWC), the seedlings still showed drought tolerance through morphological and physiological responses, but root growth suffered serious water stress compared to better water supply treatments. According to our study, keeping a minimum gravimetric SWC of 8% might be important for the growth and establishment of A. sparsifolia during the early growth stage. These results will not only enrich our knowledge of the responses of woody seedlings to various water availabilities, but also provide a new insight to successfully establish and manage A. sparsifolia in arid environments, further supporting the sustainable development of oases.