Effects of meteorlogical and soil factors on seed germination of Corethrodendron multijugum (Maxim.) B. H. Choi et H. Ohashi

Five distinct counties were selected within Qinghai Province: Hualong County (HL), Huzhu County (HZ), Guide County (GD), Wulan County (WL), and Dulan County (DL).For each county, five categories of meteorological data spanning 30 consecutive years were selected for analysis: annual average temperature (AT), annual average land surface temperature(LST), annual average relative humidity(RH), annual cumulative sunshine duration(SD), and annual cumulative precipitation(CP).Soil samples were collected using the following steps[24]. Using a soil auger with an inner diameter of 3.5 cm, collect nine S-shaped soil cores at depths ranging from 0 to 20 cm as composite soil samples. In addition, each sampling point uses a circular knife to take an undisturbed soil and immediately weigh its wet weight for subsequent determination of soil moisture content. To prevent the influence of plant litter on soil properties, we strictly excluded any presence or residue of such debris during sampling. Soil samples were then passed through a 2 mm sieve to remove roots and stones. Subsequently, each soil sample was divided into three portions. One portion was stored at 4°C for analysis of inorganic nitrogen (ammonium nitrogen and nitrate nitrogen nitrogen) and available phosphorus. Another portion was air-dried indoors for determining soil physicochemical properties. Seed germination test of Corethrodendron multijugum (Maxim.) B. H. Choi et H. Ohashi was carried out in the laboratory in December, 2024. From each sampling point, 50 seeds were randomly selected from the seed bag and the process was repeated three times. First, the seeds were rinsed with distilled water, then disinfected with a 10% NaClO solution for 5 minutes. Afterwards, the seeds were rinsed again with distilled water for 2 minutes, and finally dried by blotting with filter paper. Moisten the filter paper with distilled water and lay it flat in a sterile 9-cm diameter petri dish. Distribute the seeds evenly on the filter paper, then added 7 ml of distilled water to each dish. A total of 45 petri dishes were obtained (15 sampling points × 3 replicates). The light incubator should be set to a cycle of 14 hours of illumination at 25°C, followed by 10 hours of darkness at 20°C, with a relative humidity of 60%. Subsequently, all Petri dishes were to be placed inside. The number of germinated seeds was recorded once every 24 hours, and new filter paper and distilled water were replaced. When no new seeds germinate for five consecutive days, the seed germination experiment was considered complete. The germination test lasted a total of 14 days. On the final day of the experiment, the plumule length (PL), and radicle length (RL) of 10 seedlings in each petri dish were recorded. If fewer than 10 seedlings were present, the plumule and radicle lengths of all seedlings were measured.青海省共选取5个县域开展研究，分别为化隆县（Hualong County, HL）、互助县（Huzhu County, HZ）、贵德县（Guide County, GD）、乌兰县（Wulan County, WL）与都兰县（Dulan County, DL）。针对各所选县域，选取连续30年的5类气象数据进行分析，包括年平均气温（annual average temperature, AT）、年平均地表温度（annual average land surface temperature, LST）、年平均相对湿度（annual average relative humidity, RH）、年累计日照时数（annual cumulative sunshine duration, SD）以及年累计降水量（annual cumulative precipitation, CP）。 土壤样品采集流程参照文献[24]执行：采用内径3.5 cm的土钻，以S形布点法采集0~20 cm土层的9个土芯，混合制备为复合土壤样品；同时，每个采样点使用环刀采集原状土，并立即称量其湿重，用于后续土壤含水率测定。为避免植物凋落物对土壤属性的干扰，采样过程中严格清除此类碎屑的存在与残留。采集完成后，将土壤样品过2 mm筛以去除根系与石块，随后将每份样品分为三份：一份置于4℃冷藏保存，用于测定无机氮（铵态氮与硝态氮）及有效磷；一份置于室内风干，用于测定土壤理化性质。 2024年12月于实验室开展多枝岩黄耆（Corethrodendron multijugum (Maxim.) B. H. Choi et H. Ohashi）的种子发芽试验。从每个采样点的种子袋中随机选取50粒种子，每组处理重复3次。试验步骤如下：先用蒸馏水冲洗种子，再以10%次氯酸钠（NaClO）溶液消毒5 min；随后再次用蒸馏水冲洗种子2 min，最后用滤纸吸干表面水分。将蒸馏水浸湿的滤纸平铺于直径9 cm的无菌培养皿中，将种子均匀排布于滤纸上，向每个培养皿中加入7 ml蒸馏水，最终共制备45个培养皿（15个采样点×3次重复）。将光照培养箱设置为循环模式：25℃下光照14 h，随后20℃下黑暗10 h，相对湿度控制为60%，并将所有培养皿置于培养箱内。每24 h记录一次萌发种子数，并更换新的滤纸与蒸馏水；若连续5天无新种子萌发，则判定发芽试验结束。本次试验总时长为14天，试验结束当日，测定每个培养皿中10株幼苗的胚芽长（PL）与胚根长（RL）；若幼苗数量不足10株，则测定所有幼苗的胚芽与胚根长度。