Effects of soil rock fragment content on the USLE-K factor estimating and its influencing factors

Rock fragments are an important component of soil, and their presence has a significant impact on soil erosion and sediment yield. In this paper, the effects of rock fragments in the topsoil profile (RFP) and rock fragments on the soil surface (RFS) on the soil erodibility factor (K) were assessed at a global scale. The spatial pattern of the relationship between stoniness and erodibility (R_S-K) and its predominant factors were explored through correlation analysis, pattern analysis, and random forest model analysis. The results were as followings: (1) The existence of RFP increased K by 2.84%. The RFS of the mountain land and desert/Gobi reduced K by 18.7%; therefore, once the RFP and RFS were taken into account in the calculation, K was 6.98% lower. (2) The predominant factors of the effect of RFS and the joint effect of RFP and RFS were elevation and slope gradient. The predominant factors of the effect of RFP were annual average precipitation and annual average temperature. (3) In assessing and mapping soil erosion in large regions, special attention should be given to areas with large rock fragment contents, a relatively high altitude, and the presence of steep slope. If rock fragments were not taken into consideration, the mapping results of soil erosion may be biased. This article made the calculation of K more complete and accurate, thereby improving the accuracy of regional soil erosion estimation. This research was of significance for the investigation of global hydrological effects and simulation of the global soil carbon budget.     

泥东风螺4个群体遗传多样性的AFLP分析

利用AFLP分子标记方法对4个群体(福建连江野生、连江养殖、长乐养殖、广西野生)的泥东风螺进行遗传多样性分析。结果:用11对引物共扩增出908条有效片段,其中684条(75.33%)为多态性片段,224条片段(24.67%)为4个群体所共有;遗传多样性指数分析显示,4个群体的有效等位基因数、平均等位基因数、Shannon’s多样性指数和平均杂合度依次为1.500 6、1.974 0、0.464 7、0.303 4,Nei’s遗传距离为0.128 4~0.180 6,遗传相似系数为0.834 8~0.879 5,表明4个泥东风螺群体具有较为丰富的遗传多样性,且群体间具有较高的遗传相似性;分子方差分析(AMOVA)结果显示,4个群体中83.49%的变异来源于群体内,14.65%的变异来源于地区间,而群体间的遗传变异仅为1.86%,且4个群体间的遗传分化(GST)为0.195 4,基因流(NM)为2.058 6,说明群体间的基因交流水平较低;UPGMA聚类分析和主坐标(PCA)分析结果表明,长乐养殖群体和广西野生群体遗传距离最近,而连江野生群体与其他3个群体的遗传距离最远。     

不同盐度低渗胁迫处理对龙须菜切段再生能力及光合生理的影响

为探究龙须菜对低渗胁迫的生理性适应，分析了龙须菜主枝切段在不同盐度低渗培养液(盐度19.500、13.000、6.500、0.000)下耐受不同胁迫时间(1、3、6、12和20 h)后，继续恢复正常盐度(盐度26.000)培养过程中的形态发生、光合生理指标和细胞器亚显微结构变化。结果显示，短于12 h的低渗(盐度0～19.500)胁迫可以促进龙须菜切段的出芽，其总出芽数均高于对照组(盐度26.000)。3 h的淡水胁迫后恢复至正常盐度培养，藻段再生过程的出芽数目较多，鲜重增加最多，表现出了明显的生长优势。龙须菜藻段经淡水胁迫3 h后恢复至正常盐度培养28 d，藻段的相对生长率(RGR)为0.91%/d，较对照组RGR提高了61.27%。1和3 h淡水胁迫对龙须菜藻段的光合生理指标无明显的负面效应，且恢复至正常盐度培养后藻段的光合生理活性增强，提示低渗胁迫可能增强了藻段的细胞代谢活力。透射电镜观察表明，经淡水胁迫3 h后，表皮细胞内的红藻淀粉颗粒、质体小球及脂质体等为藻体生长发育提供能量的物质和质体再生所需中性脂原料明显增加，适应于藻段再生过程的新生芽形成。相反，长时间的淡水胁迫对色素体...