Long-term effects of mowing on plasticity and allometry of Leymus chinensis in a temperate semi-arid grassland,China

Mowing is an important land management practice for natural semi-arid regions.A growing body of empirical evidence shows that different mowing regimes affect the functioning of grassland ecosystems.However,the responses of plant functional traits to long-term mowing and their allometric scaling under long-term mowing are poorly understood.For a better understanding of the effects of mowing on grassland ecosystems,we analyzed the allometric traits of leaves and stems of Leymus chinensis(Trin.) Tzvel.,a dominant grass species in eastern Eurasian temperate grassland,at different mowing intensities(no clipping,clipping once every two years,once a year and twice a year).Experiments were conducted on plots established over a decade ago in a typical steppe of Xilinhot,Inner Mongolia,China.Results showed that most of the functional traits of L.chinensis decreased with the increased mowing intensity.The responses of leaves and stems to long-term mowing were asymmetric,in which leaf traits were more stable than stem traits.Also significant allometric relationships were found among most of the plant functional traits under the four mowing treatments.Sensitive traits of L.chinensis(e.g.leaf length and stem length) were primary indicators associated with aboveground biomass decline under high mowing intensity.In conclusion,the allometric growth of different functional traits of L.chinensis varies with different long-term mowing practices,which is likely to be a strategy used by the plant to adapt to the mowing disturbances.     

基于NDVI的乌梁素海湿地植被变化

运用3S技术,以1987、2000年和2010年的Landsat5 TM遥感影像为基础数据源,计算乌梁素海湿地3期的归一化植被指数(NDVI),基于NDVI像元二分模型反演了植被覆盖度。通过转移矩阵对比不同年际间各等级植被覆盖度的转化比例,并分析植被变化的驱动力。结果表明:1987—2010年,乌梁素海地区植被覆盖度总体较好,其中,低植被覆盖度(20%)所占比例由30.81%降低到了16.57%,中等植被覆盖度(20%~50%)所占比例变化不大,保持在14.50%左右,而高植被覆盖度(50%)所占比例则由原来的15.68%提高到了31.05%,整个地区的荒漠化土地在逐渐减少,农田的土地利用面积逐年增加。影响植被覆盖度的因素主要有人为因素和气候因素,人为因素不仅包括人类的生产活动对植被产生的影响,还包括对不同土地类型的利用及相关政策的实施等所产生的影响;气候因素则主要体现在温度和降水。     

Influence of vegetation parameters on runoff and sediment characteristics in patterned Artemisia capillaris plots

Vegetation patterns are important in the regulation of earth surface hydrological processes in arid and semi-arid areas. Laboratory-simulated rainfall experiments were used at the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling, northwestern China, to quantify the effects of Artemisia capillaris patterns on runoff and soil loss. The quantitative relationships between runoff/sediment yield and vegeta- tion parameters were also thoroughly analyzed using the path analysis method for identifying the reduction mechanism of vegetation on soil erosion. A simulated rainfall intensity of 90 mm/h was applied on a control plot without vegetation(C0) and on the other three different vegetation distribution patterns: a checkerboard pattern(CP), a banded pattern perpendicular to the slope direction(BP), and a single long strip parallel to the slope direction(LP). Each patterned plot received two sets of experiments, i.e. intact plants and roots only, respectively. All treatments had three replicates. The results showed that all the three other different patterns(CP, BP and LP) of A. capillaris could effectively reduce the runoff and sediment yield. Compared with C0, the other three intact plant plots had a 12%–25% less runoff and 58%–92% less sediment. Roots contributed more to sediment reduction(46%–70%), whereas shoots contributed more to runoff reduction(57%–81%). BP and CP exhibited preferable controlling effects on soil erosion compared with LP. Path analysis indicated that root length density and plant number were key pa- rameters influencing runoff rate, while root surface area density and root weight density were central indicators affecting sediment rate. The results indicated that an appropriate increase of sowing density has practical signifi- cance in conserving soil and water.     

Effects of deficit irrigation with saline water on spring wheat growth and yield in arid Northwest China

Field experiments were conducted in 2008 and 2009 to study the effects of deficit irrigation with saline water on spring wheat growth and yield in an arid region of Northwest China. Nine treatments included three salinity levels s1, s2 and s3 (0.65, 3.2, and 6.1 dS/m) in combination with three water levels w1, w2 and w3 (375, 300, and 225 mm). In 2008, for most treatments, deficit irrigation showed adverse effects on wheat growth; meanwhile, the effect of saline irrigation was not apparent. In 2009, growth parameters of w1 treatments were not always optimal under saline irrigation. At 3.2 and 6.1 dS/m in 2008, the highest yield was obtained by w1 treatments, however, in 2009, the weight of 1,000 grains and wheat yield both followed the order w2 > w1 > w3. In this study, spring wheat was sensitive to water deficit, especially at the booting to grain-filling stages, but was not significantly affected by saline irrigation and the combination of the two factors. The results demonstrated that 300-mm irrigation water with a salinity of less than 3.2 dS/m is suitable for wheat fields in the study area.     

辽宁省凌源市青龙河流域植被状况与恢复利用

对流域内植被恢复更新方法及资源利用途径进行了进行了详细阐述,对林业的可持续发展和资源保护具有一定的借鉴和指导意义。     

黄河滩区不同刈割期对热研4号王草生产性能和品质的影响

为了找到热研4号王草(Pennisrtum purpureumxp typhoidevm‘Reyan No.4’)在河南省黄河滩区营养和产量俱佳的刈割利用方式,从苗高80cm开始,在留茬15~20cm的情况下,采用每隔30d、40d、60d和全年1次性的刈割方式,研究不同刈割方式对王草生长、产量和营养水平的影响,为当地草食家畜的发展提供优质且稳定的饲草。研究表明:刈割会限制茎长,增加茎粗,有利于植株的分蘖及降低倒伏率;过频刈割会降低茎叶比(S/L ratio),叶面积指数(LAI)和生长速度,不利于饲草生产;适度的刈割有利于提高鲜干比(F/D ratio)、单株分蘖数和生长速度,有利于牧草的高产。另外,刈割次数对热研4号王草粗蛋白质和粗纤维含量有显著影响,而对粗脂肪、粗灰分和无氮浸出物含量影响不显著,多次刈割会提高粗蛋白质含量、降低粗纤维含量,每隔30d与40d刈割1次与1年仅割1次相比,粗蛋白质含量分别提高5.47%(P0.05)和2.80%,粗纤维含量分别降低6.67%(P0.05)和5.54%(P0.05),而每隔60d刈割1次和1年仅割1次相比,饲草营养没有显著差异。综合评价结果表明:每隔60d刈割1次,一年刈割2次,留茬15~20cm,牧草生长良好,粗蛋白质含量可达到13.01%,全年产草量达到29.83tDM·hm-2,均达到理想水平。     

1982-2012年全球干旱区植被变化及驱动因子分析

基于长时间序列卫星遥感数据GIMMS3g NDVI(1982-2012年),分析了全球干旱区(包括亚湿润干旱区、半干旱区、干旱区和极端干旱区)植被时空变化及其对气候和人文等非气候因子的响应.结果表明:①全球干旱区NDVI总体呈显著增长趋势(P＜0.001),增长速率为0.0005·a-1,略低于全球植被增长速率.显著上升区域和显著下降区域分别占全球植被显著变化区域面积的27.0％和7.7％(P＜0.05).显著退化面积最大区域为半干旱区.②降水作为干旱区植被变化的主要影响因子,主要表现在对干旱区和半干旱区植被的影响上,对亚湿润干旱区和极端干旱区影响较小.③全球不同干旱区植被变化及驱动因子存在较大差异.如澳大利亚南部主要受到季节降水的影响,植被改善;而南美和欧亚大陆中部则主要受到人为因素的影响,植被退化.     

Topographical and hydrological effects on meso-scale vegetation in desert steppe,Mongolia

This study investigated the seasonal variations of the normalized difference vegetation index(NDVI) and its relationships with climatic variables and topography in a small-scale(20 km×20 km) area(i.e., Tsogt-Ovoo village) within the desert steppe zone of Mongolia using in-situ observed climate data and satellite remote sensing data. We found that the topography is very important for vegetation growth in the desert steppe although the summer precipitation is the constraining factor. The unexpectedly high NDVI(up to 0.56), as well as the high aboveground biomass, in the valley bottom was primarily resulted from the topography-modulated redistribution of overland flow after relatively heavy precipitation events during the growing season. This makes the valley bottoms in desert steppes not only reliable feeding resources for livestock but also heavens for wild lives. But, the detected large standard deviation of annual maximum NDVI(NDVI_(max)) from 2000 to 2013 in the valley bottom in response to rather variable precipitation implies that the valley bottoms under desert steppe climates are more vulnerable to climatic change.     

Land cover change detection based on satellite data for an arid area to the south of Aksu in Taklimakan desert

An experiment is made to detect the land-cover change in the area located to the south of Aksu in the northern Taklimakan desert through analyses of satellite data pixel by pixel basis. The analyzed data are those observed in the late summer and early autumn of 1973, 1977, 1993 and 1995. As a parameter of land-cover, SAVI (Soil Adjusted Vegetation Index) derived from the data of Landsat MSS and JERS-1 OPS (Optical Sensor) is used. The result indicates the increase of vegetation in the oasis areas, confluent area of the Yarkant and Kashgar Rivers and around reservoirs while little change occurs in the desert area. The 1973 satellite image shows the abundant flow in the Yarkant River while the river is almost dried up in the satellite images of later years. The trend of the decrease in the Hotan River flow is recognized although not so dramatic as that of the Yarkant River.     

金沙江干热河谷主要造林树种干季光合与蒸腾作用区域效应分析

植物光合与水分生理特征是植物逆境适应能力评价的重要参考指标。文中研究探讨了金沙江干热河谷8个主要造林树种光合与蒸腾作用在河谷上段鹤庆县和中段元谋县的空间差异及干季转向干热季时的时序差异。结果表明:河谷上段与中段的地理变化对供试树种的净光合速率(Pn)、蒸腾速率(Tr)及水分利用效率(WUE)具有明显影响,但树种不同,影响程度具有明显区别;随河谷上段及中段的地理变化,供试树种Pn在3月干季发生的升降变化与5月干热季一致,具有一定的季节稳定性。在由3月干季转向5月干热季过程中,随着干热胁迫的持续与加深,绝大部分供试树种Pn、Tr在河谷上段与中段间的差异愈趋显著。