祁连山排露沟流域青海云杉天然更新与土壤水热的关系

青海云杉是祁连山区森林生态系统的建群种,其天然更新对维持祁连山森林生态系统功能具有重要意义。以祁连山排露沟流域青海云杉林天然更新为研究对象,于2021年6-9月测定海拔2700-3300m的0-40cm土层土壤温度和水分数据,并于7月中旬对样地天然更新进行每木检尺,将天然更新划分为幼苗(第一龄级)阶段和幼树(第二龄级)阶段,通过方差分析探究不同海拔更新苗胸径、株高的差异,再进一步建立回归模型拟合更新苗胸径、株高与各层土壤水热的关系,探讨更新苗胸径、株高对土壤水热的响应。结果表明:(1)更新苗胸径、株高随海拔升高而降低,海拔2700m幼苗胸径与3300m幼苗胸径存在显著性差异(P<0.05),海拔2700m、2800m幼苗、幼树株高与3300m幼苗、幼树株高存在显著性差异(P<0.05),幼树胸径在各海拔均不存在显著性差异,表明更新苗胸径对海拔的敏感性要低于更新苗株高。(2)更新苗胸径、株高与土壤温度呈正相关,与土壤水分呈负相关,幼苗胸径与20cm土壤温度和土壤水分的相关系数最大,幼树胸径与40cm土壤温度和土壤水分相关系数最大,幼树株高与40cm土壤温度及20cm土壤水分相关系数最大。(3)回归模型显示幼苗胸径和株高对土壤水热的利用模式相同,而幼树胸径和株高对土壤水热的利用模式存在差异。(4)青海云杉天然更新随着龄级的增加,影响生长的主要因素由土壤温度逐渐变为土壤水分,更新苗胸径对土壤水热的响应也随着龄级的增加在逐渐减弱。

Relationship between natural regeneration of Picea crassifolia and soil moisture and temperature in Pailugou watershed of Qilian Mountains

Picea crassifolia is an established species of forest ecosystem in Qilian Mountains, and its natural regeneration is of great significance for maintaining forest ecosystem function in Qilian Mountains. In this study, the natural regeneration of P. crassifolia forest in Pailugou watershed of Qilian Mountains was taken as the research object. The soil temperature and moisture of 0-40cm soil layer at an altitude of 2700-3300m were measured from June to September 2021, and the natural regeneration of the sample plots was examined by tally in mid-July. The natural regeneration was divided into seedling (first age class) stage and sapling (second age class) stage, and the differences in diameter at breast height (DBH) and plant height of new seedlings at different altitudes were explored by analysis of variance (ANOVA). Then, a regression model was established to fit the relationship between DBH and plant height of new seedlings, soil temperature and soil moisture of each layer, and to explore the response of DBH and plant height of new seedlings to soil temperature and soil moisture. The results showed that: (1) the DBH and plant height of new seedlings decreased with the increase of altitude. There were significant differences in DBH between 2700m seedlings and 3300m seedlings (P<0.05). The height of seedlings and saplings at 2700m and 2800m was significantly different from that at 3300m (P<0.05). There was no significant difference in DBH of saplings at different altitudes, indicating that the DBH of new seedlings was less sensitive to altitude than height of new seedlings. (2) The DBH and plant height of new seedlings were correlated with soil temperature and soil moisture positively, while correlated with soil moisture negatively. The correlation coefficient between DBH of seedlings and soil temperature and moisture at 20cm was the highest. The correlation coefficient between DBH of saplings and soil temperature and moisture at 40cm was the highest. The correlation coefficient between height of saplings and soil temperature and moisture of at 40cm was the highest. (3) The regression model showed that the utilization patterns of soil water and temperature by DBH and plant height of seedlings were same, while the utilization patterns of soil temperature and soil moisture by DBH and plant height of saplings were different. (4) With increase of age class, the main factor affecting the growth of P. crassifolia natural regeneration gradually changed from soil temperature to soil moisture, and the response of DBH of new seedlings to soil water and temperature decreased gradually with the increase of age class.