多时间尺度的桉树人工林耗水及其对环境因子的响应

发布时间：2018-08-31 15:10

【摘要】：桉树(Eucalyptus)是联合国粮农组织推荐的三大类速生造林树种之一,已经成为我国南方速生丰产林的战略性树种。热带海南岛的中西部地区为重要的桉树人工林分布区,这里属于半湿润、半干旱区;连片种植桉树林产生了较好的经济效益,但也引起了一系列的生态问题,其中水生态问题尤为突出。本研究以海南儋州林场桉树林为研究对象,利用茎流测量系统长期监测4~5a桉树树干液流速率,并同步监测光合有效辐射、大气温度、相对湿度、降水、土壤水分等环境因子,分析桉树人工林液流速率在时、日、月等不同时间尺度上的变化规律,揭示不同时间尺度上桉树液流速率与环境因子的相关关系,探讨不同时间尺度桉树液流的主要影响因素,并测算桉树群落年耗水量,为桉树人工林的水分管理、合理经营提供理论依据和实践指导。研究结果表明:(1)时、日和月时间尺度上,光合有效辐射、气温、相对湿度变化显著;降水和土壤水分在月尺度上有明显变化,不同深度土层的土壤水分变化幅度不同,但存在极显著相关和显著差异,且受光合有效辐射的影响较大。(2)桉树不同方位树干液流实时监测结果表明:晴、阴、雨天桉树不同方位树干液流速率日变化规律相似,晴天呈单峰型曲线,阴天和雨天呈多峰型或无峰型曲线;树干东、南方位液流启动与到达峰值时间分别较西、北方位要早20分钟左右;晴、阴、雨天桉树各方位液流速率均呈极显著正相关,且存在显著或极显著差异;晴天东、南、西、北侧较低液流速率比较高液流速率低13.7%,阴天低34.4%,雨天低9.4%。晴天北侧的液流速率与均值最为接近,阴、雨天北侧的液流经过校正可以减少整树蒸腾测算误差。(3)在时尺度上,桉树液流速率呈现昼高夜低的变化;晴、阴、雨天桉树液流速率日变化曲线有差异,晴天以单峰曲线为主,阴天以单峰或多峰为主,雨天变化特征不明显;晴、阴、雨天桉树液流全天日均值分别是5.58 mL·cm-2·h-1、3.97 mL·cm-2·h-1、1.41mL·cm-2·h-1。在日尺度上,桉树液流速率变化幅度较大,变化范围为4.86~145.12mL·cm-2·d-1;即使是相邻两天,液流速率差异也可很大,外界环境因子是影响其差异的主要原因。在月尺度上,桉树树干液流速率大小依次为:7月、6月、9月、8月、5月、10月、4月、11月、12月、3月、2月、1月;雨季(5~10月)树干液流显著高于旱季(1~4月和11~12月),前者月均值为2.82 L·cm-2·month-1,后者为1.47 L·cm-2·month-1。(4)在时尺度上,旱季,光合有效辐射对晴天与阴天的桉树液流速率影响最大,空气相对湿度影响次之,晴天光合有效辐射对桉树液流速率的影响较阴天更大;雨天,空气相对湿度和光合有效辐射对桉树液流速率影响较大,空气相对湿度的影响更大一些;气温与土壤水分对桉树晴、阴、雨天的液流速率影响都较小。雨季,晴、阴、雨天桉树液流速率均受光合有效辐射、空气相对湿度和气温的影响,以光合有效辐射影响最大;气温与土壤水分对桉树液流速率影响都较小。在日尺度上,旱季光合有效辐射是桉树液流速率的主要影响因子;雨季气温和光合有效辐射是日尺度上桉树液流速率的主要影响因子。在月尺度上,光合有效辐射是全年各月桉树液流速率变化的最主要影响因子,30-60cm土壤水分是液流速率变化的重要因子。(5)桉树液流日累积量因天气、胸径不同而不同。晴天最多,雨天最少;胸径越大,日累积量越大。不同径阶标准木月耗水量有相似的月变化特征,但桉树径阶越大,单木月蒸腾耗水量差异越大;雨季,7.51cm、9.39cm、12.45cm径阶的桉树单木蒸腾耗水量为223.86L、766.31L、2164.6L;分别占全年的61.72%、66.26%、65.95%。2016年4~5a桉树人工林群落蒸腾耗水3137543.78L·hm-2,约占当地多年降水的26.15~39.2%,日均蒸腾耗水0.86 mm,旱季日均蒸腾耗水0.61 mm;雨季日均蒸腾耗水1.1 mm。
[Abstract]:Eucalyptus is one of the three fast-growing afforestation species recommended by FAO and has become a strategic tree species for fast-growing and High-yielding forests in southern China. In this study, Eucalyptus plantation in Hainan Yanzhou Forest Farm was selected as the research object, and the sap flow rate of Eucalyptus trunk was monitored by stem flow measurement system for a long period of 4 to 5 years, and the environmental factors such as photosynthetic active radiation, atmospheric temperature, relative humidity, precipitation and soil moisture were monitored synchronously. The relationship between Eucalyptus sap flow rate and environmental factors at different time scales was revealed. The main influencing factors of Eucalyptus sap flow at different time scales were discussed. The annual water consumption of Eucalyptus community was calculated to provide water management and rational management of Eucalyptus plantation. The results show that: (1) on the time scale of day and month, the changes of PAR, air temperature and relative humidity are significant; on the monthly scale, the precipitation and soil moisture have obvious changes, and the variation range of soil moisture in different depths is different, but there are extremely significant correlations and significant differences, and they are subject to PAR. (2) Real-time monitoring results of Eucalyptus trunk sap flow in different directions showed that the diurnal variation of sap flow rate in different directions of Eucalyptus trunk was similar in sunny, cloudy and rainy days, with a unimodal curve in sunny days and a multi-modal or non-modal curve in cloudy and rainy days. On sunny days, the sap flow rate on the north side is 13.7%, 34.4% on cloudy days and 9.4% on rainy days. On sunny days, the sap flow rate on the north side is the closest to the mean value. On cloudy and rainy days, the sap flow on the north side passes through correction. (3) On the time scale, the sap flow rate of Eucalyptus presents the change of day-high and night-low; on sunny, cloudy and rainy days, the diurnal variation curves of sap flow rate of Eucalyptus are different; on sunny days, single peak curves are dominant; on cloudy days, single or multi-peak curves are dominant; on rainy days, the variation characteristics of sap flow of Eucalyptus are not obvious; on sunny, cloudy and rainy days, the diurnal mean values of sap flow of Eucalyptus are respectively 5.58 mL.cm-2.h-1,3.97 mL.cm-2.h-1,1.41 mL.cm-2.h-1.On the diurnal scale, the sap flow rate of Eucalyptus varied greatly, ranging from 4.86 mL.cm-2.d-1 to 145.12 mL.cm-2.d-1.Even in the adjacent two days, the sap flow rate varied greatly, and the main reason for the difference was the environmental factors. In the rainy season (May-October), the trunk sap flow was significantly higher than that in the dry season (January-April and November-December), the monthly mean value of the former was 2.82 L.cm-2.month-1, and the latter was 1.47 L.cm-2.month-1. (4) On the time scale, in the dry season, the shading rate of PAR on sunny and cloudy days was significantly higher than that in the dry season (January-April and November-December). On rainy days, the relative humidity of air and the photosynthetic active radiation have a greater impact on the sap flow rate of eucalyptus, and the influence of air temperature and soil moisture on the sap flow rate of Eucalyptus is greater. In rainy season, sunny, cloudy and rainy days, the sap flow rate of Eucalyptus was affected by PAR, air relative humidity and air temperature, and PAR was the most important factor. The influence of air temperature and soil moisture on sap flow rate of Eucalyptus was small. Photosynthetically active radiation (PAR) is the main influencing factor of Eucalyptus sap flow rate on a daily scale. On a monthly scale, PAR is the most important influencing factor of Eucalyptus sap flow rate on a monthly scale, and 30-60 cm soil moisture is an important factor of sap flow rate. (5) Daily accumulation of sap flow varies with weather and DBH. The monthly water consumption of standard trees with different diameter scales had similar monthly variation characteristics, but the monthly water consumption of individual trees with larger diameter scales had greater differences; the monthly water consumption of individual trees with 7.51 cm, 9.39 cm and 12.45 cm diameter scales in rainy season was 223.86 L, 766.31 L and 2164.6 L, accounting for 61.72%, 66.26% and 65.95% respectively. Eucalyptus plantation community transpiration consumed 3137543.78 L HM 2, accounting for 26.15 39.2% of local precipitation, 0.86 mm of daily transpiration, 0.61 mm of daily transpiration in dry season and 1.1 mm of daily transpiration in rainy season.
【学位授予单位】：海南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S792.39

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