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A. Hoshino Y. Yoshihara T. Sasaki T. Okayasu U. Jamsran T. Okuro K. Takeuchi 《Journal of Arid Environments》2009,73(6-7):687-690
The objective of this study was to clarify whether the changes in percent cover of plant functional types (i.e., life forms and growth forms) along a grazing gradient reflect the livestock number, which would reinforce the reliability of using a grazing gradient design and improve the management of rangeland. We selected two livestock camps that for many years have had different numbers of livestock, with approximately six times more sheep-equivalents at site 1 than at site 2. Vegetation was sampled in 10 quadrats on five transects along the grazing gradient at each site. In each quadrat, we recorded percent cover of each plant species. Our findings suggested that vegetation changes along the grazing gradient under different livestock numbers were characterized by changes in the cover of life forms: perennial species were replaced by annual species near the camps (10–50 m). However, we did not find growth form change that reflected the difference in the number of livestock. 相似文献
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Y. Yoshihara T. Okuro J. Undarmaa T. Sasaki K. Takeuchi 《Journal of Arid Environments》2009,73(3):364-368
We focused on the potential contribution of fossorial rodents to recovery of degraded abandoned Mongolian croplands. From field observations and the literature, we determined that plant litter and soil crusting were the main factors preventing establishment or growth of the perennial grass Elymus chinensis (Poaceae) on these croplands. We hypothesized that small fossorial rodents such as Mongolian gerbils promote grass establishment and growth by clearing litter and destroying crusts. We designed a path model linking number of burrows to patch size and plant volume of E. chinensis. As we hypothesized, small rodents increased the patch size of E. chinensis through reduction of litter cover. However, unexpectedly, we could not find significant effects on E. chinensis via crust thickness. Our results suggest that litter removal by the rodents gave E. chinensis suitable space that was free of competitors; this allowed expansion of the E. chinensis patches. Any effect of soil crusting on plant volume could not be explained simply by the variables we used, probably because some other mechanism, such as temporal variation in the crust, was involved. We demonstrate that small rodents are key agents in the recovery of degraded grasslands. 相似文献
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T. Sasaki T. Okayasu T. Ohkuro Y. Shirato U. Jamsran K. Takeuchi 《Journal of Arid Environments》2009,73(10):949-954
Starting in 2005, we examined differences in vegetation for three consecutive years across an airport fence that separated heavily grazed areas from areas in which grazing had been excluded for 24 years in Mandalgobi, Mongolia. We performed repeated-measures analysis separately on two community types (dominated by Allium polyrrhizum and Achnatherum splendens, respectively) to compare the effects of fencing and year on the cover of different plant functional types. There was a significant fence × year interaction for grass cover in the Allium type (but not the Achnatherum type), due to greater cover of grasses inside the fence only when rainfall was sufficient during the growing season. The effect of grazing exclusion on perennial forb cover was confounded by a significant fence × year interaction in both types. In 2007, perennial forbs were found outside the fence, but had almost disappeared inside the fence, resulting in this interaction. Annual forbs only had much greater cover values inside the fence than outside in 2006, also resulting in a significant fence × year interaction in both community types. This study thus suggests that the high rainfall variability in arid and semi-arid rangelands may modify the effects of long-term exclosure on vegetation. 相似文献
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Occurrence of water ponding on soil surfaces depending on infiltration rates on Mongolian rangeland 
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下载免费PDF全文 Katori Miyasaka Sho Shiozawa Kazuhiro Nishida Siilegmaa Batsukh Shuichiro Yoshida Undarmaa Jamsran 《水文研究》2017,31(22):3996-4005
The occurrence of water ponding on soil surfaces during and after heavy rainfall produces surface run‐off or surface water accumulation in low‐lying areas, which might reduce the water supply to soils and result in a reduction of the soil water that plants can use, especially in arid climates. On Mongolian rangeland, we observed ponded water on the surface of a specific soil condition subjected to a heavy rainfall of 30 mm/hr. By contrast, ponded water was not observed for the same type of soil where livestock grazing had been removed for 6–8 years via a fence or for nearby soil containing less clay. We measured the infiltration rate (the saturated hydraulic conductivity of the surface soil, Ks) of the three sites by applying ponded water on the soil surface (an intake rate test). The results showed that Ks in the rangeland was lower than the rainfall intensity in the site where water ponded on the soil surface; however, Ks of the soil inside of the fence has recovered to 3 times that of the soil outside of the fence to exceed the rainfall intensity. Heavy rainfall that exceeds the infiltration rate occurs several times a year at the livestock grazing site where we observed ponded water. Slight water repellency of the soil reduces rain infiltration to increase the possibility of surface ponding for the soil. 相似文献
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Jamsran Erdenebayar Takeyuki Ogata Akira Imai Jargalan Sereenen 《Resource Geology》2014,64(4):283-300
Unidirectional solidification texture (UST) in an aplite body is recognized in the Neoproterozoic highly differentiated granitic rocks at Kharaatyagaan, central Mongolia. On the basis of crystal morphology, two main types of UST were identified in the aplite body: (i) thin crenulate UST layers; and (ii) thick intergrowth UST layers. Bulk geochemistry indicates that the Kharaatyagaan UST‐bearing aplite and aplite dike are alkaline, and are enriched in light rare‐earth elements. Scanning electron microscopy and cathadoluminescence imaging of UST quartz from Kharaatyagaan show four types of quartz: euhedral quartz phenocrysts with well‐developed concentric growth zoning (Qa1) in the aplite; euhedral quartz with weak growth zoning in the aplite (Qa2); UST quartz exhibiting distinct growth zones (Qu1); and UST quartz showing mosaic texture (Qu2). Crystallization temperatures determined by the Ti‐in‐quartz geothermometer of Qa1 and Qu1 quartz range between around 500°C and 780°C and Qa2 and Qu2 range between about 490° and 630°C. The cathodoluminescence textures of quartz are predominantly caused by variations in the trace elements contents of quartz. The Qa1 and Qu1 quartz crystals are characterized by high Ti and Al concentrations in the quartz lattice, and are observed in the bottom of the Kharaatyagaan hill, which formed in the early, less evolved magmatic stage. The Qa2 and Qu2 UST quartz characterized by low Ti and variable Al concentrations are found at the top. The UST layers crystallized along the upper part of the magma chamber in the presence of fluid phases exsolved from felsic magma. 相似文献
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Wind erosion is a major contributor to land degradation and desertification. According to the Global Assessment of Human Induced Soil Degradation, the dryland territories of Mongolia are significantly affected by wind erosion. We used the wind erosion equation model in an ArcGIS environment to evaluate wind erosion across Mongolia. The individual factors of the wind erosion equation were parameterized using the following datasets: (a) monthly climatic data from 45 meteorological stations; (b) 16-day composites of MODIS Normalized Difference Vegetation Index data; (c) a SRTM DEM with a 90 m spatial resolution; and (d) the soil map of Mongolia. The results revealed the significant influence of aridity on wind erosion. The desert and semi-desert ecosystems were more vulnerable to wind erosion, hence more affected. The map of wind erosion revealed three major wind erosion regions where the maximum soil loss of 15–27 t/(hm2?a) was observed. In general, the wind erosion potentials for the entire country of Mongolia are 15–27 t/(hm2?a) in the deserts and semi-deserts, 10–15 t/(hm2?a) in the dry steppes and 5–10 t/(hm2?a) in the steppe regions. 相似文献
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