In order to provide directionally genetically improved breeding materials of poplar by exploring the phenological traits genetic variation level and its develop- ment potential of Populus deltoides and the resource evaluation was carried out; 8 phenological phases in seedling period were observed and analyzed of 60 Populus deltoids clones introduced from America. The results showed that： （1） there was obvious difference in phonological character among clones, especially in leaf-spread- ing peak stage and the end term of leaf-falling stage, with the largest variation co- efficient of 14.97% and the minimum of 3.83% respectively. （2） Leaf-spreading peak stage scattered but the end term of leaf-falling stage concentrated the most. The phonological character in early stage of seedling growth was the main factor influ- encing the length of growing season. （3） By principal component analysis, pheno- logical phases were classified into 3 typical periods, including germination stage, leaf-spreading peak stage and leaf-falling stage. （4） Totaling 60 clones were classi- fied into 4 types by using clustering analysis in phenological time variables of clones.
岸线是长江湿地生态系统的重要组成部分,研究其土地利用变化及其生境质量时空响应对长江岸线生态保护和土地资源可持续利用具有重要意义。本文以1990、2000、2010、2020年4期土地利用数据为基础,采用生态系统服务和权衡的综合评估(integrated valuation of ecosystem services and tradeoffs,InVEST)模型,研究了湖南长江岸线30年来土地利用变化及生境质量时空演变特征。结果表明:(1)1990—2020年湖南长江岸线土地利用格局发生了明显变化,草地、建设用地、未利用土地面积持续增加,占比分别增加了3.69%、0.81%和0.56%,耕地和水域面积持续减小,占比分别降低了2.46%和1.88%。(2)1990—2020年湖南长江岸线生境质量均值为0.8075,其中1990—2010年生境质量呈下降趋势,2010年后生境质量明显提高。生境质量空间分布表现为长江干线到防洪大堤逐渐降低。(3)生境质量等级以“优”和“良好”为主。相较于1990年,2020年生境质量“优”等级和“良好”等级面积占比共减少了0.25%。(4)土地利用转化产生的负面影响大于正面影响,土地利用转化导致生态环境退化和改善的土地利用变化贡献指数(land use change contribution index,CI)分别为-1.8151和0.9569,其中草地、水域转为耕地和建设用地是造成研究区生境质量下降的主要原因。该研究有助于进一步了解长江岸线土地利用变化与生境质量之间的关系,可为长江经济带生态保护和可持续发展提供科学支撑。
