从大同北魏永固陵制看古代的长度单位——里

古代长度单位"里",与现今通用长度单位"里"的计量基准不同。中国古代各朝官尺计量基准有异。本文以大同永固陵制为据,认为古"里"所用尺度一直以"营造尺"为基准,1古里相当于现今576m。笔者认为,在考古中应采用"营造尺"为基准,或换算成现代长度单位,才是较为科学准确的做法。

Characteristics of Momentum and Heat Transfer over Semiarid Grasslands with Different Grazing Intensities in Inner Mongolia,China

The drag coefficient （Ca） and heat transfer coefficient （Ch） with the bulk transfer scheme are usually used to calculate the momentum and heat fluxes in meteorological models. The aerodynamic roughness length （z0m） and thermal roughness length （z0h） are two crucial parameters for bulk transfer equations. To improve the meteorological models, the seasonal and interannual variations of Z0m, Z0h, coefficient kB-1, Cd, and Ch were investigated based on eddy covariance data over different grazed semiarid grasslands of Inner Mongolia during the growing seasons （May to September） from 2005 to 2008. For an ungrazed Leymus chinensis grassland （ungrazed since 1979）, Z0m and z0h had significant seasonal and in- terannual variations. Zorn was affected by the amount and distribution of rainfall, kB 1 exhibited a relatively negative variation compared with z0h, which indicates that the seasonal variation of z0h cannot be described by kB 1. To parameterize Zorn and z0h, the linear regressions between ln（z0m）, ln（z0h）, and the leaf area index （LAI） were performed with R2=0.71 and 0.83. The monthly average kB-1 was found to decrease linearly with LAI. The four-year averaged values of Ca and Ch were 4.5 × 10^-3 and 3.9× 10^-3, respectively. The monthly average Cd only varied by 8% while the variation of Ch was 18%, which reflects the dif- ferent impacts of dead vegetation on momentum and heat transfer at this natural grassland. Moreover, with the removal of vegetation cover, grazing intensities reduced Z0m, Z0h, Cd, and Ch.

Growth of Scotch Pine （Pinus sylvestris L.） Plantation in Northern Mongolia

The growth of Scotch pine in Northem Mongolian plantations was studied to determine variation in heights, diameters at breast height （DBH）, and main and annual volume increment of stem volumes in relation to plantation age. The study was conducted in the Tujyin Nars region, where six plantations ranging from 9 to 25 years old were selected for the assessment. Results indicate that the growth of Scotch pine on the plantations did not vary by site, and that more intensive annual increment in height was observed on Scotch pine plantations between the ages of 8 to 15 years. The amount of annual height increment and radial growth improves regularly up to 9 to 11 years of age and then the intensity of annual increment declines due to competition for light and nutrients. Additionally, there was a reduction in the number of trees per ha. Results suggest that it is necessary to implement forestry thinning which aimed at improving growth of Scotch pine on the plantations because intensity of annual increment in height and diameter reduces regularly due to restriction of growing condition.

Field Studies of Frontal Area Index in Rangeland of Mongolia

Field observation was conducted at typical rangeland in Mongolia to examine the frontal area index. Frontal area index is the characteristics of surface roughness elements affecting sand transport. The frontal area was strongly correlated with the effective shelter length on sand transport in both short grasses and shrubs. The frontal area index was 0.031 and the relationship between the roughness length and frontal area index in this site agreed with past studies.

Comparison of Arbuscular Mycorrhizal Fungal Community in Roots and Rhizosphere of Invasive Cenchrus incertus and Native Plant in Inner Mongolia,China

Plant invasions could significantly alter arbuscular mycorrhizal(AM) fungal communities, but the effect may vary with plant species and local environments. Identifying changes in the AM fungal community due to plant invasion could improve our understanding of the invasion processes. Here, we examined the AM fungal community composition both in roots and rhizosphere soils of the invasive plant Cenchrus incertus and the dominant native plant Setaria viridis in a typical steppe in Inner Mongolia by using terminal restriction fragment length polymorphism analyses(T-RFLP). The results showed that AM fungal abundance in the rhizosphere soils of C. incertus was significantly lower than that of S. viridis. The AM fungal community composition in the rhizosphere soils of the two plant species also largely differed. In general, AM fungal community structures in roots corresponded very well to that in rhizosphere soils for both plant species. The dominant AM fungal type both in invasive and native plants was T-RFLP 524 bp, which represents Glomus sp.(Virtual taxa 109 and 287). Three specific T-RF types(280,190 and 141bp) were significantly more abundant in C. incertus, representing three clusters in Glomus which also named as VT(virtual taxa) 287, 64 and 214, Rhizophagus intraradices(VT 113) and Diversispora sp.(VT 60). While the specific T-RF types,189 and 279 bp, for S. viridis, only existed in Glomus cluster 1(VT 156), were significantly less abundant in C. incertus. These results indicated that AM fungi might play an important role in the invasion process of C. incertus, which still remains to be further investigated.