Feeding behaviour of yaks on spring, transitional, summer and winter pasture in the alpine region of the Qinghai-Tibetan plateau

Of the present estimated world population of 14.2 million yaks, approximately 13.3 million occur within Chinese territories (Food and Agriculture Organization of the United Nations, 2003). Although there is an extensive bibliography covering the species, few studies have been conducted in the area of foraging behaviour. The present study was conducted at pasture during the spring, transitional, summer and winter seasons to determine the daily temporal patterns of grazing and ruminating behaviour by yaks. During each study period, two 24 h recordings were undertaken with each of six mature dairy yaks. One study period was conducted on each of the transitional, summer and winter pastures, whereas, due to the considerable changes occurring in the morphology of the spring pasture, three separate studies were completed during March, April and May. During the second of these studies (April), the effect of level of concentrate supplementation on grazing and ruminating behaviour was also examined. Behaviour recordings were made using solid-state behaviour recorders. Short-term intake rates (IR, g min(-1)) were calculated by weighing yaks before and after approximately 1 h of grazing, retaining the faeces and urine excreted and applying a correction for insensible weight loss. Yaks spent less time grazing during the dry season (the early period on the spring pasture) compared with the later green swards (the later period on the spring pasture, the transitional pasture and the summer pasture) (P < 0.05). When the forage quality improved, but there was still insufficient mass (the later period on the spring pasture), the yaks extended their grazing time at the expense of other activities. During the early periods on the spring pasture, the short-term IR by yaks was up to 53 g DM min(-1), significantly higher than at other times (P < 0.05). The level of concentrate offered had little or no effect on grazing or ruminating time. The total eating time of the yaks offered 0.5 or 1.0 kg concentrate was 2.9 and 4.5 h day(-1) respectively, significantly lower than unsupplemented yaks (6.8 h) (P < 0.05). In general, yaks can regulate their foraging behaviour according to the changes of sward conditions in order to achieve optimal grazing strategies. (C) 2007 Published by Elsevier B.V.

南海沉积物中的放射虫及其古环境意义

In this paper a systematic study of radiolarian from surface sediments of all the South China Sea (SCS) has initially been done for its deposit ecology, biogeography and paleoenvironment significance. The paleoenvironment information obtained by radiolarian analysis and other sedimentary method for core samples is also made use as the synthesis proxy for revealing the paleoenvironment changes in the SCS and the relations of it with the past globe change during last 200ka. Some results come out of this study as: 1) Radiolarian skeleton chemistry composition and skeleton morphological features were analyzed, chiefly dividing them as 15 types of basic morphological features: 2) Analysis of biogeographical feature demonstrates that the fauna in SCS obviously belonging to a transitional type of west Pacific - Indian Ocean and has a particularity of itself: 3) Tendency of radiolarian population distribution is lower in shallow continental shelf area, increasing gradually toward the abyssal region; 4) Nine character boundaries of radiolarian depth distribution in the sediments from whole the South China Sea may be recognized; 5)Two radiolarian transfer functions for paleotemperature and paleo-primary productivity in the South China Sea have also been established respectively. The equation of transfer function for winter paleotemperature has only an average estimated error of 0.18678 ℃ and the equation for paleo-primary productivity has the calculation accuracy of 85.31%; 6) Changes of radiolarian individuals, numbers of species and H(S) values in core NS93-5 show the completely different oceanic geographical circumstance and ecology structure in the Last Maximum Glacial with present; 7) The abundance variation of some raiolarian warm species and cold species indicate the changes of water masse features along with the paleoenvironment evolution, showing that this sea area clearly is controlled in 6 issues of oxygen isotopes by the cold water masses; 8) By comparative analysis of δ ~(18)O curves with GISP2;s ice core can core 17940 of the northern SCS, the occurring characters of D/O's events 1-21 and Heinrich's events H1-H6 have been revealed in this sea area by core NS93-5, which prove the existence of paleoclimatic tele-connections between the southern SCS and Arctic region since about 200ka BP.

Strong effect of transitional metals on the sulfur resistance of Pd/HY-Al2O3 catalysts for aromatic hydrogenation

In order to improve the sulfur resistance of noble metal catalysts in the aromatic hydrogenation of diesel fuel, the alloying effect of non-noble metals with Pd was studied. Toluene hydrogenation over Pd and Pd-M bimetallic catalysts (M = Cr, W,La, Mn, Mo, Ag) on a mixed HY-Al2O3 support was investigated in the presence of 3000 ppm sulfur as thiophene in the feedstock. The results showed that the addition of the second metals strongly affected the activity of toluene hydrogenation, which suggests that the sulfur resistibility of Pd-M bimetallic catalysts is much different from single Pd. La, Mn, Mo and Ag decreased the sulfur resistance of the palladium catalysts. For example, the toluene conversion at 553 K was observed to decrease sharply from 39.4 wt.% on Pd to 1.6 wt.% on Pd-Ag, which is by a factor of 25. One of the important findings in this article is that Cr and W increase hydrogenation activity of Pd catalysts. The reactions occurring on these catalysts include hydrogenation, isomerization and hydrocracking, The addition of the second metals has no noticeable effects on the hydrogenation and isomerization selectivity, but it slightly suppresses hydrocracking reactions. The four typical catalysts, Pd-Cr, Pd-W, Pd-Ag and Pd were characterized by infrared (IR) spectroscopy of pyridine and CO. LR spectra of CO revealed the strong interaction between Pd and the second metal as Cr, W and Ag (or their oxide), indicating that the improvement in sulfur resistance originates from electron-deficient Pd with the addition of second metals. (C) 2001 Elsevier Science B.V. All rights reserved.