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利用稳定氢同位素和热扩散技术研究张北防护林杨树的水分来源和蒸腾耗水,分析确定未退化与退化杨树的水分关系差异.结果表明:在生长季节中退化杨树主要利用0~30 cm土壤水分,未退化杨树主要利用30~80 cm土壤水分,两者的水分来源不同.旱季时,未退化杨树利用深层土壤水分和地下水的比例明显高于退化杨树.雨季中,杨树对0~30 cm土壤水分的利用比例增加,退化杨树增加幅度明显高于未退化杨树,对30~180 cm土壤水分的利用比例均减少.未退化杨树的液流速率大于退化杨树,不同天气中液流速率表现出相似的变化趋势,但未退化杨树液流的启动时间比退化杨树早.相关分析表明,未退化和退化杨树液流速率与土壤温度、风速、太阳辐射、相对湿度、空气温度均呈极显著的相关关系.退化杨树液流速率与土壤温度和空气相对湿度呈极显著负相关,与其他因素呈显著正相关,而未退化杨树仅与空气相对湿度呈极显著负相关,与其他因素均呈显著正相关关系,表明退化和未退化杨树蒸腾耗水易受环境条件的影响.退化杨树液流日累计量明显小于未退化杨树,表明其蒸腾耗水量较少;退化杨树水分来源浅,蒸腾耗水的减少并不能阻止林分退化.
Stable hydrogen isotope and thermal diffusion techniques were used to study the source of water and transpiration of poplar in Zhangbei shelterbelt, and the differences of water relationships between undegraded and degraded poplar were analyzed.The results showed that the main use of degenerated poplar was 0 ~ 30 cm soil moisture, the non-degenerated poplar mainly uses 30-80 cm soil moisture, and the water sources of the two are different.The proportion of deep soil water and groundwater utilization in the non-degraded poplar was significantly higher than that in the degraded poplar in the dry season.In the rainy season, The percentage of soil water utilization in 0-30 cm increased, while that of degraded poplar increased significantly than that of non-degraded poplar, while the proportion of soil water utilization in 30-180 cm decreased.The flow rate of non-degraded poplar was higher than that of degraded poplar Trees and the weathering rates showed a similar trend but the un-degenerated poplar flow started earlier than the degraded poplar.The correlation analysis showed that the non-degenerated and degraded poplar flow rate was positively correlated with the soil temperature, wind speed, Solar radiation, relative humidity and air temperature were significantly correlated.The degenerated poplar flow rate was significantly negatively correlated with soil temperature and air relative humidity, and positively correlated with other factors , While the non-degraded poplar only had a significant negative correlation with air relative humidity and a positive correlation with other factors, indicating that the water consumption of degraded and non-degraded poplar was susceptible to environmental conditions. Cumulative amount was significantly less than that of non-degenerated poplar, indicating that its transpiration water consumption is less; the source of degraded poplar is shallow, and the decrease of transpiration water consumption does not prevent the degradation of forest stand.