Influence of rangeland protection and seasonal grazing on aboveground vegetation,forage quality and weight gain of small ruminants–a study in Thar Desert,Pakistan

The Thar Desert,Sindh,Pakistan is characterized by low productivity.Besides,economy is based on agriculture,livestock and mining,nevertheless,livestock graze freely on public and private land.The aim of this research was to determine biomass production and to evaluate the effects of continuous and seasonal grazing on protected and unprotected plots.A 45 ha protected rangeland area of Hurrabad in the Umerkot Thar desert was selected and divided into three blocks of 15 ha each.Blocks of the same size were also established in unprotected area.The data for vegetation biomass,canopy cover,forage nutrients and weight gain of animals in two seasons(spring and summer)was collected from both protected and unprotected sites.The results showed that biomass significantly increased in summer in both sites.However,the biomass values in protected sites were significantly higher.Similarly,the vegetation cover also seemed to increase in summer in both protected(90.7%±0.29%)and unprotected sites(39.2%±0.09%).The foliar concentrations of all nutrients varied significantly with season.The average final live-weight gain for does on the protected grazing sites during the 42-day period in spring and the 96 days after the monsoon was almost double that of does grazing on the unprotected site during 2016 and 2017(P<0.05).The study concludes that the protection of grazing lands during certain periods can lead to better production of vegetation and livestock and improve range conditions.

南岭同纬度带典型区域气候特征差异与成因分析

基于91个气象站观测值和大气环流模型CCSM3,对南岭同纬度典型区域的气候特征参数进行分析,并对未来不同区域的温度和降水进行预测,进一步探索净初级生产力对温度和降水的敏感性,并分析导致南岭同纬度带典型区域气候差异的可能原因。结果表明:1)南岭和同纬度其它区域呈现不同的干旱期和湿润期,撒哈拉沙漠、阿拉伯半岛沙漠和塔尔沙漠仅存在干旱期,墨西哥荒漠和南岭均存在湿润期,但两者湿润期出现的季节有差异。南岭在植物生长的春季和夏季雨热同期,而墨西哥荒漠雨水充沛的季节多在秋季。墨西哥除湿润期外,一年有两次干旱期,其中冬旱持续的时间较长。2)撒哈拉沙漠、阿拉伯半岛沙漠和塔尔沙漠的潜在蒸散、风速和日照百分率均高于墨西哥荒漠和南岭,但降水正好相反。墨西哥荒漠干季的水汽压与撒哈拉沙漠和阿拉伯半岛沙漠接近,低于该区域湿季及塔尔沙漠与南岭的值。3)在B1气候情景下,对2000―2099年5个阶段(每20年为一个阶段)与1981―2010年的温度和降水数据进行T-test检验发现,南岭同纬度5个典型区域的未来温度均呈极显著上升趋势(P<0.001),降水总体呈增加趋势,然而在不同阶段和区域也存在不同比例的显著减少和显著增加情况。4)通过比较5个区域是否存在温度或降水成为潜在生产力限制因子发现,南岭及同纬度的其它区域均为降水限制因子区域。其中,撒哈拉沙漠和阿拉伯半岛沙漠对降水的敏感性显著高于墨西哥荒漠、塔尔沙漠和南岭。5)南岭与同纬度其它区域气候迥异的原因除气候变化外,还包括海陆位置、人类活动干扰的强弱、地形地貌特征等因素。

Landscaping and performance of some aesthetic plant species in hot, arid conditions of India

Establishment of ornamental and aesthetic plants in hot, arid conditions of India is difficult due to the prevailing climatic, edaphic and biotic factors. Effect of turfgrass on the growth of ornamental plants in hot arid conditions has not been studied so far anywhere in the world. A study was conducted on the campus of Arid Forest Research Institute, Jodhpur, India to assess the performance of a few ornamental plant spe- cies in combination with turfgrass and without turfgrass with respect to different soil tilling intervals. Growth of plants was better with turfgrass than without turfgrass. We suggest adopting a soil tilling interval of 30 days to achieve optimum growth of ornamental plant species in terms of height and crown diameter. Our results can help reduce labor costs and achieving better landscapes in fewer days in hot urban conditions of Indian sub continent.

巴基斯坦塔尔沙漠风积砂土湿陷性特征

依托巴基斯坦塔尔矿区风积砂土湿陷性研究课题,基于前期勘察成果和相关湿陷性试验结果,对塔尔沙漠风积砂土的湿陷性特征及其基本物理指标与湿陷性的相关性进行分析研究。结果表明:风积砂土的湿陷性主要分布在①、②层,湿陷性系数平均值为0.039,湿陷性程度属于轻微-中等;风积砂土的颗粒组成和易溶盐特征是湿陷变形的主要内在基础;风积砂土湿陷性系数与含水率之间离散性较强,与孔隙比基本呈正相关关系,与干密度之间基本呈线性负相关,当孔隙比<0.65或干密度>1.60 g/cm^(3)时,风积砂土不具有湿陷性。

强夯法处理湿陷性风积砂土地基评价

工程界关于“湿陷性”的相关规范、研究成果主要集中在黄土,而对于“湿陷性砂土”则存在一定的缺失,可参考工程处理案例很少。以巴基斯坦塔尔沙漠某在建电厂场地地基处理工程为依托,基于强夯前后地基土检测、试验数据分析,对强夯法处理湿陷性砂土地基效果进行评价。试验结果及分析表明:强夯后风积砂土的干密度增大,孔隙比减小,压缩模量提高,基本可以消除湿陷性,是一种快速有效的处理湿陷性风积砂土地基的方法,对类似工程地基土的处理具有很好的借鉴及指导意义。