【作者】 吴芳；

【导师】 陈云明；

【作者基本信息】 西北农林科技大学 ， 水土保持与荒漠化防治， 2011， 硕士

【摘要】 我国黄土高原半干旱地区,降水少,蒸发强烈,水土流失严重,生态环境脆弱,解决区域水资源不足与植被建设之间的矛盾,实现人工植被的持续发展,是改善黄土高原地区生态环境的根本途径。本研究以黄土丘陵半干旱区的刺槐和刺柏人工林为研究对象,利用TDP树干边材液流测定系统对刺槐和侧柏的树干液流进行连续监测,并结合气象数据,分析了刺槐和侧柏树干边材液流动态及其影响因素,计算两树种的单木蒸腾耗水量。取得的主要研究结果如下:1.典型天气条件下,刺槐和侧柏树干边材液流通量密度的变化趋势相似。晴天,刺槐和侧柏的树干边材液流通量密度的日变化均呈单峰型曲线,并与光合有效辐射、水蒸气压差的变化规律相似。刺槐和侧柏的日平均树干液流通量密度分别为晴天>多云天>阴天。展叶初期,随着刺槐叶片的生长,边材液流通量密度值逐渐增大,呈单峰型曲线,同一时期侧柏的边材液流通量密度大于刺槐。生长盛期,刺槐边材液流通量密度的日变化呈宽峰型曲线,液流通量密度在达到峰值后有小幅的波动,侧柏液流通量密度的日变化为单峰型曲线,液流启动后迅速上升,达到峰值后急剧下降。刺槐落叶期,边材液流通量密度逐渐减小,侧柏则变化幅度较小,但夜间有明显的液流存在。2.展叶末期和生长盛期,刺槐边材液流通量密度均与光合有效辐射、水蒸气压差、空气温度、风速呈显著正相关,与相对湿度呈显著负相关,且相关程度的大小顺序为光合有效辐射>空气温度>水蒸气压差>相对湿度>风速。侧柏生长盛期边材液流通量密度与气象因子的相关性与同一时期的刺槐相同。3.刺槐的胸径和边材面积,侧柏的地径和边材面积之间均呈幂指数关系。单木的日蒸腾耗水量随着胸(地)径的增大而增大。生长季不同时期,刺槐和侧柏的单木月蒸腾耗水累积量呈明显的季节变化规律,刺槐春季和秋季耗水量小,8月的耗水量最大,侧柏的蒸腾耗水量则为5月最大,在整个生长季总体呈下降趋势。2009年和2010年刺槐和侧柏单株在整个生长季的总蒸腾耗水量相差较大。但各月的蒸腾耗水量占整个生长季总蒸腾耗水量的比例在不同年份间的变化较小。2009年和2010年刺槐林地生长季的蒸腾耗水总量分别为103.25mm和96.75mm,侧柏林地生长季的蒸腾好水总量分别为194.97mm和181.90mm。4.刺槐和侧柏的根系主要分布在0-60cm土层,平均有效根重密度分别为0.14mg?cm-3,0.29 mg?cm-3,侧柏是刺槐的2.07倍。刺槐的有效根系(直径≤1mm)主要分布在20-30cm土层,侧柏的有效根系主要分布在10-20cm土层。刺槐和侧柏林地0-30cm土层的土壤含水量随着土层深度的增加迅速下降,这主要与有效根系的分布有关,根系吸水导致土壤水分含量下降,侧柏林地的土壤含水量低于刺槐。30cm以下刺槐和侧柏林地土壤水分的变化趋势相似,随着土层深度的增加,含水量有极小幅度的增加,同一土层刺槐和侧柏林地的土壤含水量相近。更多还原

【Abstract】 The semiarid region of Loess Plateau in China is characterized by low precipitation, strong evaporation, serious soil and water loss, and weak eco-environment. The improvement of eco-environment in the Loess Plateau is the basic approach to resolve the contradiction between insufficient water resource and vegetation construction and to realize the sustainable development of artificial vegetation in this area. With the thermal dissipation probe(TDP) sap flow measuring system and automatic meteorological station, the stem lever water use of Robinia pseudoacacia and Platycladus orientalis and related environment factors were monitored.The influencing factors of sap flow were analyzed systematically. The main results are as follows:1. Under typical weather conditions, R. pseudoacacia and P. orientalis have a similar trend in sap flux density. In sunny days, both the diurnal sap flux density variations of R. pseudoacacia and P. orientalis are shown as single-peak curves, which are in step with the changing patterns of photosynthetically active radiation (PAR) and vapor pressure differential (VPD), and the order of the sap flux density is sunny days> cloudy days> overcast days. In the early leaf frushing period, the sap flux density of R. pseudoacacia increases gradually with the growth of leaves, and it presents a single-peak curve in this stage. During the growing seaon, diurnal sap flux density variation process of R. pseudoacacia appears as a wide-peak curve; it reaches the peak at 11 o’clock in the morning and reduces with the decrease of solar radiation after that. While for P. orientalis, the diurnal sap flux density variation shows a single-peak curve whose shape is steep and narrow; it increases sharply in the beginning of growth stage and falls down significantly after getting to its maximum. In the deforliation period, the sap flux density of R. pseudoacacia declines gradually, while that of P. orientalis almost keeps stable, and there is an obvious rise during the night time.2. In the late leaf frushing period and the rapid growth period, sap flux density of R. pseudoacacia positively correlates with PAR, VPD, air temperature(T) and wind speed(Vs), while negatively correlates with relative humidity(RH). The order of the correlation degree is: PAR> T> VPD> RH> Vs. For P. orientalis, the correlativity between sap flux density and meteorological factors in the growth stage is the same with R. pseudoacacia in the corresponding period.3. There is a power exponent relationship between diameter at breast height (DBH) and sapwood area for R. pseudoacacia, and so is ground diameter and sapwood area for P. orientalis. Both the diurnal transpiration consumption per wood of R. pseudoacacia and P. orientalis increase as DBH (ground diameter) increases. In different growing seasons, the accumulative monthly water consumption per wood of these two species has clear seasonal characteristics. For R. pseudoacacia, the water consumption is relatively less in spring and autumn, but the most in August (280.11 L in 2009 and 238.32 L in 2010). While P. orientalis has the maximum transpiration consumption in May and June (238.21 L and 198.80 L respectively in 2009), the transpiration consumption decreases gradually during the whole growing season. There is a relatively big difference in total transpiration consumption per wood in the growing season between R. pseudoacacia and P. orientalis in 2009 and 2010. However, the monthly transpiration consumption presents stable ratios of the total transpiration consumption during the whole growing season in different years. The total transpiration consumption of R. pseudoacacia forest in the growing season is 103.25mm in 2009 and 96.75mm in 2010, and for P. orientalis forest, it is 194.97mm in 2009 and 181.90mm in2010.4. The root system of R. pseudoacacia and P. orientalis mainly distribute in the soil layer of 0-60 cm. The average effective root density of P. orientalis is as 2.07 times as that of R. pseudoacacia, and they are respectively 0.14 mg·cm-3 and 0.29 mg·cm-3. The effective root (diameter≤1mm) of R. pseudoacacia mainly distribute in the 20-30 cm layer, and 10-20 cm for P. orientalis. In the top 30 cm layer, soil moisture content of both R. pseudoacacia and P. orientalis decrease rapidly with soil depth, and that is because the most distributed effective root uptake a large amount of soil moisture. The soil moisture content of P. orientalis is lower than that of R. pseudoacacia in the 0-30 cm layer because of the higher effective root density in P. orientalis plantation. In the soil layer deeper than 30 cm, R. pseudoacacia and P. orientalis have a similar trend in soil moisture content which increases slightly with soil depth, and also similar moisture content values in same soil layers.更多还原