The Seasonal Variability and Environmental Factors Influencing the Transpiration of Western Juniper (Juniperus occidentalis) Saplings

IF 3.1 Q2 WATER RESOURCES

Hydrology Pub Date : 2023-12-06 DOI:10.3390/hydrology10120232

Carlos G. Ochoa, Mohamed A. B. Abdallah

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Abstract

There is scarce information regarding the interactions between young tree water uptake and the environment in water-limited ecosystems. This study was conducted in a semiarid rangeland ecosystem in central Oregon, Pacific Northwest Region, USA. We measured the tree transpiration of western juniper (Juniperus occidentalis) saplings using the stem heat balance (SHB) method. We analyzed the correlation between transpiration and environmental factors affecting the saplings’ water use from May to October for 2017, 2018, 2019, 2021, and 2022. The study results showed that total annual precipitation for all but one year was below the long-term (2005 to 2022) mean precipitation value of 307 mm for the study site. Significantly higher transpiration rates were observed in the wet vs. dry years. The highest monthly averaged transpiration rates (2.95 L d−1) were obtained in August during the above-average precipitation year (2017). Peak transpiration rates for the below-average precipitation years were generally reached in June or July, ranging from 0.91 to 1.65 L d−1. The seasonal response of transpiration to different environmental factors varied. For all years, vapor pressure deficit (VPD), solar radiation (SR), and air temperature (AT) showed a positive correlation with transpiration, whereas precipitation (Pr) and relative humidity (RH) indicated a negative correlation with transpiration. Soil moisture (SM) and soil temperature (ST) positively correlated with transpiration for most years. A strong association between VPD and transpiration was observed during the wettest (2017; 327 mm) and driest (2021; 198 mm) years. Results from this study add to the limited literature on sapling transpiration and can contribute to the improved management of cool-climate rangeland ecosystems through an enhanced understanding of water use by young-stage trees and its potential impacts on the water balance of restored juniper landscapes.

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影响西部杜松树苗蒸腾作用的季节变化和环境因素

在水资源有限的生态系统中，关于幼树水分吸收与环境之间相互作用的信息很少。本研究在美国太平洋西北地区俄勒冈中部半干旱的牧地生态系统中进行。采用茎热平衡(SHB)法测定了西部杜松(Juniperus occidentalis)幼树的蒸腾量。分析了2017年、2018年、2019年、2021年和2022年5 - 10月林分蒸腾与影响林分水分利用的环境因子的相关性。研究结果表明，除1年外，该站年总降水量均低于长期(2005 ~ 2022年)平均降水量307 mm。在干湿年份，蒸腾速率明显高于干湿年份。在高于平均降水年份(2017年)，8月份的月平均蒸腾速率最高，为2.95 L d−1。低于平均降水年的蒸腾速率峰值一般出现在6月或7月，在0.91 ~ 1.65 L d−1之间。蒸腾对不同环境因子的季节响应存在差异。水汽压差(VPD)、太阳辐射(SR)和气温(AT)与蒸腾呈显著正相关，降水量(Pr)和相对湿度(RH)与蒸腾呈显著负相关。土壤湿度(SM)和土壤温度(ST)与蒸腾蒸腾呈显著正相关。在最潮湿的季节(2017年;327毫米)和最干燥(2021;198毫米)年。本研究的结果补充了关于幼树蒸腾作用的有限文献，并有助于通过加深对幼树水分利用及其对恢复后杜松景观水分平衡的潜在影响的了解，改善冷气候草原生态系统的管理。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Hydrology Earth and Planetary Sciences-Earth-Surface Processes

CiteScore

4.90

自引率

21.90%

发文量

192

审稿时长

6 weeks

期刊介绍： Journal of Hydrology publishes original research papers and comprehensive reviews in all the subfields of the hydrological sciences, including water based management and policy issues that impact on economics and society. These comprise, but are not limited to the physical, chemical, biogeochemical, stochastic and systems aspects of surface and groundwater hydrology, hydrometeorology, hydrogeology and hydrogeophysics. Relevant topics incorporating the insights and methodologies of disciplines such as climatology, water resource systems, ecohydrology, geomorphology, soil science, instrumentation and remote sensing, data and information sciences, civil and environmental engineering are within scope. Social science perspectives on hydrological problems such as resource and ecological economics, sociology, psychology and behavioural science, management and policy analysis are also invited. Multi-and interdisciplinary analyses of hydrological problems are within scope. The science published in the Journal of Hydrology is relevant to catchment scales rather than exclusively to a local scale or site. Studies focused on urban hydrological issues are included.

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