Water Consumption Of Trees Research Articles

Azimuthal and radial variations in sap flow and its effects on the estimation of transpiration for Picea mongolica.

In this study, we applied thermal dissipation probe technology to examine sap flow in various directions (east, south, west, and north) and at different depths (0-2, 2-4, 4-6 cm) within the stem of natural Picea mongolica trees in the eastern of Otindag Sandy Land to provide a scientific basis for accurately quantifying water consumption of P. mongolica forests through transpiration and to enhance the understanding of water relations. The results showed that the diurnal variation of sap flow in different directions displayed a unimodal curve, with the sap flow sequence being south>east>west>north. The sap flow at different sapwood depths exhibited an obvious unimodal curve, with a significant decrease as sapwood depth increased. Compared with that calculated from the mean sap flux density in four directions (23.57 kg·d-1), water consumption calculated using the mean value in south-east, east-west, south-west, north-east, north-south, and north-west was overestimated by 10.2%, 5.5%, 14.5%, and underestimated by 12.3%, 8.2%, 9.8%, respectively. The water consumption calculated using the values from the east, south, and west was overestimated by 6.1%, 14.4%, and 15.4%, respectively, and underestimated by 30.7% in the north. In addition, compared with the water consumption calculated from the mean value in three sapwood depths (48.51 kg·d-1), that calculated using sap flux density at sapwood depths of 0-2, 2-4, and 4-6 cm were overestimated by 18.8%, underestimated by 1.7%, and underestimated by 62.9%, respectively. These results indicated that sap flow of P. mongolica had significant azimuthal and radial variations, which considerably influence the estimation of tree water consumption. Installing probes at 0-2 cm simultaneously in both the north and east of the trunk could effectively reduce the estimation error of whole-tree water consumption by 4.2%. This approach enabled the accurate quantification of water consumption of individual P. mongolica trees in sandy areas, thereby improving the precision of transpiration water consumption estimates scaling up from individual level to stand level.

Tree root-soil interaction: field study of the effect of trees on soil moisture and ground movement in an urban environment

Abstract Aims Little research has been conducted to quantify the atmosphere-plant-soil interaction in urban environments due to a lack of understanding of plant water use characteristics and the limited availability of high-quality field data. This research aims to quantify the drying effect of root systems of two Australian native tree species on soil water dynamics and ground movement using high-quality field measurement data. Methods A long-term field monitoring on soil moisture variation and ground movement close to C. maculata and M. styphelioides, was conducted for up to 45 months in Melbourne, Australia. The water requirement of each tree was monitored using sap flow sensors. Laboratory soil testing was conducted to obtain soil properties and develop profiles of soil suction and water content. The intercorrelation between soil water dynamics and tree soil water use was established. Results Tree roots could no longer extract water from the soil when total soil suction exceeded a wilting point of approximately 1000 kPa. The soil profile differences between the two sites were a significant factor causing substantial differences in tree water consumption. Conclusions At the C. maculata site, tree-induced soil desiccation occurred to a depth of 1.1 m, while at the M. styphelioides site, it extended down to 2.2 m depth. The tree root-soil interaction analysis shows that water uptake of 10.64 kL by tree roots partially contributes to a 5% decline in soil water content and a 270 kPa rise in soil suction, resulting in a continuous soil settlement of 22 mm.

Trees with anisohydric behavior as main drivers of nocturnal evapotranspiration in a tropical mountain rainforest.

This study addresses transpiration in a tropical evergreen mountain forest in the Ecuadorian Andes from the leaf to the stand level, with emphasis on nocturnal plant-water relations. The stand level: Evapotranspiration (ET) measured over 12 months with the Eddy-Covariance (ECov) technique proved as the major share (79%) of water received from precipitation. Irrespective of the humid climate, the vegetation transpired day and night. On average, 15.3% of the total daily ET were due to nocturnal transpiration. Short spells of drought increased daily ET, mainly by enhanced nighttime transpiration. Following leaf transpiration rather than air temperature and atmospheric water vapor deficit, ET showed its maximum already in the morning hours. The tree level: Due to the humid climate, the total water consumption of trees was generally low. Nevertheless, xylem sap flux measurements separated the investigated tree species into a group showing relatively high and another one with low sap flux rates. The leaf level: Transpiration rates of Tapirira guianensis, a member of the high-flux-rate group, were more than twice those of Ocotea aciphylla, a representative of the group showing low sap flux rates. Representatives of the Tapirira group operated at a relatively high leaf water potential but with a considerable diurnal amplitude, while the leaves of the Ocotea group showed low water potential and small diurnal fluctuations. Overall, the Tapirira group performed anisohydrically and the Ocotea group isohydrically. Grouping of the tree species by their water relations complied with the extents of the diurnal stem circumference fluctuations. Nighttime transpiration and hydrological type: In contrast to the isohydrically performing trees of the Ocotea group, the anisohydric trees showed considerable water vapour pressure deficit (VPD)-dependent nocturnal transpiration. Therefore, we conclude that nighttime ET at the forest level is mainly sourced by the tree species with anisohydric performance.

宁夏河东沙区刺槐和丝绵木水分利用策略

PDF HTML阅读 XML下载 导出引用 引用提醒 宁夏河东沙区刺槐和丝绵木水分利用策略 DOI: 10.5846/stxb202202100330 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31760236，42161013）；宁夏自然科学基金项目（2022AAC03094） Water use strategies of Robinia pseudoacacia and Euonymus bungeanus in the east sandy land of the Yellow River in Ningxia, China Author: Affiliation: Fund Project: The National Natural Science Foundation of China (31760236,42161013);The National Natural Science Foundation of Ningxia,China(2022AAC03094) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:刺槐和丝绵木混交林是宁夏河东沙区防护林建设的主要模式，了解刺槐和丝绵木的水分利用策略，能为区域植被恢复和防护林林分结构调整提供科学依据。以宁夏河东沙区刺槐（Robinia pseudoacacia）和丝绵木（Euonymus bungeanus）混交林为研究对象，通过监测微气象、树干液流和土壤质量含水量，结合大气降水、土壤水、植物木质部水同位素组成，采用Granier及其校正公式，运用贝叶斯混合模型（MixSIAR）和相似性比例指数（PS）研究2个树种的蒸腾耗水、水分来源和水分利用关系。结果表明：刺槐和丝绵木的蒸腾耗水量在生长季中期较高，前期和后期较小，刺槐的蒸腾耗水量是丝绵木的1.55倍；影响刺槐蒸腾耗水的主要环境因子为饱和水汽压差、太阳辐射、0-40 cm土壤质量含水量和40-120 cm土壤质量含水量；影响丝绵木蒸腾耗水的主要环境因子为饱和水汽压差、太阳辐射、平均气温、0-40 cm土壤质量含水量和40-120 cm土壤质量含水量；蒸腾耗水较高时，刺槐主要吸收利用中层土壤水，丝绵木主要吸收利用浅层土壤水，蒸腾耗水较低时，刺槐主要吸收利用浅层土壤水，丝绵木主要吸收利用中层土壤水；在土壤水分含量较小的月份，刺槐和丝绵木主要通过水分利用空间上的差异来应对干旱，维持自身的蒸腾耗水；土壤水分含量较高的月份，刺槐和丝绵木的相似性比例指数最大，存在较强的水分竞争关系；浅层土壤水分含量较高可能反映了沙区植物根系对土壤水分再分配作用下植物在水分和养分需求之间的平衡。 Abstract:The mixed forest of Robinia pseudoacacia and Euonymus bungeanus is the typical shelterbelt construction mode in the east sandy land of the Yellow River in Ningxia, China. Research on the water use strategies of Robinia pseudoacacia and Euonymus bungeanus could provide scientific basis for restoration regional vegetation and stand structure optimization allocation of shelter forest. In this study, the sap flow of Robinia pseudoacacia and Euonymus bungeanus was monitored continuously to clarify the characteristics of water consumption by transpiration which calculated by Granier and its correction formula, as well as simultaneous records of micro-meteorological factors and gravimetric soil water content. Combined with stable hydrogen and oxygen isotope analysis of rainfall, soil water and plant xylem water, the water source and water use relationship among symbiotic trees were quantitatively analyzed by Bayesian mixture model (MixSIAR) and the proportional similarity index (PS). The results showed that the water consumption of Robinia pseudoacacia and Euonymus bungeanus were higher in the middle growing season, but lower in the early and late growing season. The water consumption of Robinia pseudoacacia was 1.55 times larger than Euonymus bungeanus. The main environmental factors affecting water consumption of Robinia pseudoacacia were vapour pressure deficit, solar radiation, 0-40 cm gravimetric soil water content and 40-120 cm gravimetric soil water content. The main environmental factors affecting water consumption of Euonymus bungeanus were vapour pressure deficit, solar radiation, average temperature, 0-40 cm gravimetric soil water content and 40-120 cm gravimetric soil water content. Robinia pseudoacacia mainly used the middle layer soil water and Euonymus bungeanus mainly used the shallow layer soil water in the season with high water consumption. While the shallow layer soil water and the middle layer soil water were ultilized by Robinia pseudoacacia and Euonymus bungeanus separately in the season with lower tree water consumption. In addition, Robinia pseudoacacia and Euonymus bungeanus was able to deal with drought and maintain their own water consumption mainly through the spatial difference of water use strategy under drought seasons. In the seasons when gravimetric soil water content was higher, the proportional similarity index (PS) of Robinia pseudoacacia and Euonymus bungeanus was the highest, and there was a strong water competition relationship. The higher of shallow layer gravimetric soil water content might reflect a trade-off between water and nutrient requirements of plants under the effect of soil water redistribution by plant roots in the sandy land. 参考文献 相似文献 引证文献

Effects of Different Land Use Patterns on Soil Water in Loess Hilly and Gully Regions of China.

Soil water is a major barrier to ecological restoration and sustainable land use in China’s Loess Hilly Region. For the restoration of local vegetation and the optimal use of the region’s land resources, both theoretically and practically, it is essential to comprehend the soil water regimes under various land use types. The soil water content in the 0−160 cm soil profile of slope cropland, terraced field, jujube orchard, and grassland was continuously measured using EC-5 soil moisture sensors during the growing season (May−October) in the Yuanzegou catchment in the Loess Hilly Region to characterize the changes in soil water in these four typical land use types. The results showed that in both years of normal precipitation and drought, land use patterns varied in seasonal variability, water storage characteristics, and vertical distribution of soil water. In the dry year of 2015, the terraced field effectively held water. During the growing season, the 0−60 cm soil layer’s average soil water content was 2.6%, 4.2%, and 1.8% higher than the slope cropland, jujube orchard, and grassland, respectively (p < 0.05), and the 0−160 cm soil layer’s water storage was 43.90, 32.08, and 18.69 mm higher than the slope cropland, jujube orchard, and grassland, respectively. The average soil water content of the 0−60 cm soil layer in the jujube orchard was 2.9%, 3.8%, and 4.5% lower than that of slope cropland, terraced field, and grassland, respectively, during the normal precipitation year (2014) (p < 0.05). Only 35.0% of the total soil water storage was effectively stored in the 0−160 cm soil layer of the jujube orchard during the drought year. There was a significant difference in the grey relational grade between the soil water in the top layer (0−20 cm) and the soil water in the middle layer (20−100 cm) under different land use types, with the terraced field having the highest similarity degree of soil water variation trend, followed by grassland, slope cropland, and jujube orchard. Slope croplands in the study region may be converted into terraced fields to enhance the effective use of rainfall resources and encourage the expansion of ecological agriculture. Proper water management practices must be employed to reduce jujube tree water consumption and other wasteful water usage in order to guarantee the jujube orchard’s ability to expand sustainably. This would address the issue of the acute water deficit in the rain-fed jujube orchards in the Loess Hilly Region.

Repeated summer drought changes the radial xylem sap flow profile in mature Norway spruce but not in European beech

Water consumption of trees is one of the most important processes connected to their survival under ongoing climate change and extreme events such as drought. Radial profiles of xylem sap flow density are an integral component to quantify the water transport for the level of an individual tree and that of ecosystems. However, knowledge of such radial profiles, in particular under stress, is very scarce. Here we show the radial profile of the xylem sap flow density in mature European beech (Fagus sylvatica L) and Norway spruce (Picea abies (L) Karst.) under repeated summer drought induced by throughfall exclusion (TE) and subsequent recovery compared to untreated control trees (CO). We measured xylem sap flow density (udaily in L dm−2 d−1) down to 8 cm sapwood depth at breast height using two different approaches, a thermal dissipation system and the heat field deformation method. In beech, repeated throughfall exclusion did not affect the radial xylem sap flow profile. However, in spruce, udaily was strongly reduced across the profile under repeated drought, changing the profile from a linear to a logarithmic regression. Even two years after drought release, the xylem sap flow profile did not fully recover in TE spruce. The reduction of udaily along the radial profile was accompanied by a reduction of the leaf area in TE spruce by c. 50%, while sapwood depth remained constant. The reduction of the xylem sap flow density along the profile reduced the calculated water consumption of TE spruce trees by more than 33% compared to CO trees, also after drought release. The impact of stressors such as repeated drought on the xylem sap flow density across the radial profile and its consequences for trees’ and stands’ water consumption needs to be addressed in more detail to minimize uncertainties in quantifying ecosystem water cycles.

Water use dynamics of trees in a Pinus tabuliformis plantation in semiarid sandy regions, Northeast China

Quantifying tree water use and its environmental controlling mechanisms are significantly important for understanding of adaptation strategy of trees and plantation management in semiarid and arid regions. Here, tree water consumption and tree conductance of Chinese pine (Pinus tabuliformis) plantation were quantified using sap flow measurements. Environmental variables were measured concurrently during the growing seasons of 2019 and 2020. Results showed that daily, daytime and nighttime tree water consumption averaged 27.4, 24.7, and 2.7 kg d-1 across two years, respectively. Nighttime tree water consumption accounted for 10% of the daily’s, which was mainly used for recharging stem water storage deficit caused by daytime transpiration to avoid hydraulic failure. Daytime tree water consumption was more driven by solar radiation than by vapor pressure deficit. Moreover, daytime tree conductance was 0.9 mm s-1, and significantly decreased with increasing vapor pressure deficit and decreasing soil moisture, indicating that trees had strict stomatal regulation on tree transpiration. Scaling-up from tree to stand transpiration, daytime stand transpiration averaged 1.1 mm d-1 across two years, while accumulated stand transpiration was 112.8 mm and 126.8 mm in 2019 and 2020, respectively, accounting for 33% and 37% of precipitation. However, soil evaporation occupied 35% and 51% of precipitation in 2019 and 2020, respectively. This indicated that most of water in the plantation was consumed by soil evaporation. Difference between precipitation and sum of daytime stand transpiration, canopy interception, soil evaporation, and change in soil water storage was positive in two years, indicating that water budget was balanced. These findings indicated that Chinese pine trees had strict stomatal regulation on tree transpiration, and could recharge stem water storage deficit by nighttime sap flow. Moreover, stand transpiration occupied a small part of the water balance, and thus water supply was surplus, resulting in maintaining the stability of Chinese pine plantation.

亚热带岩溶区典型常绿和落叶树种的蒸腾特征及其对环境因子的响应

植物蒸腾是水循环的重要组成部分，为了解亚热带岩溶区树木的蒸腾耗水情况，探究气候和水文地质条件对植物蒸腾的影响，运用Granier热耗散探针技术，对亚热带岩溶区次生林内的常绿树种女贞（L.lucidum）和落叶树种刺槐（R.pseudoacacia）的树干液流进行了连续监测，并同步监测了气象因子及土壤含水率（SMC），探讨在不同时间尺度下两种生活型树种的蒸腾特征及其对环境因子的响应。结果表明：（1）在季节尺度下，影响两树种整树蒸腾量（ET）的主要因子为太阳辐射强度（Rs）、气温（T）和水汽压亏缺（VPD）；女贞蒸腾量（ET_L）表现为夏季（1.29 kg/h） > 春季（0.57 kg/h） > 冬季（0.15 kg/h） > 秋季（0.13 kg/h），刺槐蒸腾量（ET_R）表现为夏季（0.90 kg/h） > 春季（0.31 kg/h） > 秋季（0.16 kg/h） > 冬季（0.04 kg/h）。（2）在日尺度下，晴天两树种ET呈现出明显的单峰日变化，且主要影响因子均为T、VPD和Rs；但由于常绿和落叶树种的生理特征差异，降雨时ET_L受到抑制，而ET_R则显著提升。（3）从昼夜层面来看，两树种夜间蒸腾量不足日蒸腾总量的35%。在夜雨现象和树木生理特征的影响下，秋冬季夜间蒸腾量占比明显高于春夏季，刺槐的平均夜间蒸腾量及其占比（1.56 kg，24.1%）高于女贞（1.08 kg，13.9%）。;Plant transpiration is an important part of water cycle in ecosystem, that is, the process of water transfer from soil to atmosphere through plants. It is driven by solar radiation, air temperature, air humidity and wind speed, and also affected by soil water storage capacity. Understanding and quantifying the influence mechanism of transpiration is an important basis to explore the water consumption of vegetation and the water balance of ecosystem. However, although the climate conditions in the subtropical karst area are good, there is a drought period of 4-5 months. At the same time, plants are often affected by water stress because of the thin soil layer and low water holding capacity of soil in karst area. The study of plant transpiration characteristics helps us understand the water consumption of trees in subtropical karst areas, and is also of great significance for exploring the impact of climate and hydro-geological conditions on plant transpiration. Granier's thermal dissipation probe method was used to continuously monitor the trunk sap flow of the evergreen tree species (L.lucidum) and the deciduous tree species (R.pseudoacacia) in the secondary forest in the subtropical karst area. The meteorological factors and soil moisture content (SMC) are also monitored simultaneously. Our purpose is to analyze the transpiration characteristics of two life-form tree species and their responses to environmental factors on different time scales. The results show that:(1) at the seasonal scale, the main factors affecting the whole-tree transpiration (ET) are solar radiation intensity (Rs), air temperature (T) and vapor pressure deficiency (VPD). The transpiration of L.lucidum (ET_L) is shown as summer (1.29 kg/h) > spring (0.57 kg/h) > winter (0.15 kg/h) > autumn (0.13 kg/h), transpiration of R.pseudoacacia (ET_R) is shown as summer (0.90 kg/h) > spring (0.31 kg/h) > autumn (0.16 kg/h) > winter (0.04 kg/h). (2) On the daily scale, the ET of the two tree species shown obvious single peak curve on sunny day, and the main factors affecting transpiration are T, VPD and Rs. However, due to the differences in the physiological characteristics of evergreen and deciduous tree species, ET_L is weakened during rainfall, while ET_R is significantly increased. (3) in terms of day and night, the nocturnal transpiration of the two tree species accounts for less than 35% of the total daily transpiration on average. Affected by the phenomenon of night precipitation and the physiological characteristics of trees, the proportion of nocturnal transpiration in the autumn and winter is significantly higher than that in the spring and summer. At the same time, the average daily nocturnal transpiration and its proportion of R.pseudoacacia (1.56 kg, 24.1%) is higher than that of L.lucidum (1.08 kg, 13.9%).

Use of gravimetric measurements to calibrate thermal dissipation probes with stem segments

AbstractTree transpiration is an important part of the global water cycle, and it is frequently represented by sap flow measurements at the individual plant scale. The thermal dissipation probes (TDPs) are commonly employed to measure and calculate sap flows, for which Granier equation is generally used. However, the original Granier equation has been found to underestimate sap flow rates. Calibration methods using different materials (i.e., whole trees or stem segments) have been proposed to recalibrate TDPs; however, these methods are often either expensive or complicated. This study proposes a new device that uses the gravimetric measurement method (GMM) to recalibrate TDPs. The GMM is relatively simple and easy to conduct. The proposed device uses a tube and siphon to maintain a constant pressure; an electronic balance is used to measure the actual sap flow. Four plant species with different stem porosity types, Pyrus pyrifolia (diffuse‐porous), Quercus fabri (ring‐porous), Platycarya strobilacea (ring‐porous) and Kalopanax septemlobus (ring‐porous), were selected to examine the performance of the GMM. The results showed that: (1) good correlations were obtained between the actual sap flow (from gravimetric measurements) and sap flow estimates obtained using the original TDP technique; (2) the results of the GMM‐recalibrated TDP measurement equation greatly differed from those of the original Granier calibration equation; and (3) the recalibration equation derived from the GMM outperformed the original Granier equation. This study suggests that the developed GMM can be used to recalibrate TDPs, and that using this method can help to improve sap flow measurements, thereby improving estimates of tree water consumption and transpiration.

Temporal variation and controlling factors of tree water consumption in the thornbush savanna

For a typical encroacher tree of the thornbush savanna, we studied the responses of water consumption to changes in soil water availability within 80 cm depth, vapor pressure deficit (VPD), and global radiation. Therefore, we monitored the sap velocities of Senegalia mellifera trees over 2 years in a maximum of 20 stems (6–15 plant individuals) per measurement period on a site in central Namibia. For this water-restricted ecosystem we aimed to understand the role of an encroacher tree on soil water dynamics and potential groundwater recharge.At the day-to-day scale, soil water was the primary driver of cumulative daily sap velocities (Qn-day). In the dry season, Qn-day decreased with increasing soil drought. Rainy seasons triggered multiple sapflow phases, initiated by soil-wetting rain events and associated with increase of soil water. Maximum attainable Qn-day increased with VPD and radiation. We hypothesize a 3-stage response of tree water use to soil water tension (SWT): (1) SWT < pF 2.6–2.7: soil water is optimal for transpiration; (2) pF 2.6–2.7 < SWT < pF 3.2–3.7: transpiration decreases with soil drought; (3) SWT > pF 3.2–3.7: trees minimize transpiration. Our findings contribute to the understanding of tree–grass coexistence in savannas. The responses of tree water use to soil water within 80 cm depth indicate that S. mellifera exploits the same depths as grasses, in contrast to the classic hypothesis of vertical niche differentiation.

Tree Wind Breaks in Central Asia and Their Effects on Agricultural Water Consumption

Across Central Asia, agriculture largely depends on irrigation due to arid and semi-arid climatic conditions. Water is abstracted from rivers, which are largely fed by glacier melt. In the course of climate change, glaciers melt down so that a reduced glacier volume and reduced water runoffs are expected to be available for irrigation. Tree wind breaks are one option to reduce water consumption in irrigated agriculture and build resilience against climate change. This paper therefore assesses the water consumption of major crops in Kyrgyzstan and adjacent areas, i.e., cotton (Gossypium hirsutum L.), wheat (Triticum aestivum L.), corn (Zea mays L.), rice (Oryza sativa L.), potato (Solanum tuberosum L.), and barley (Hordeum vulgare L.) in combination with tree wind breaks. Crop water consumption was assessed through the Penman Monteith approach. Tree wind break types investigated were single rows from poplars (Populus spec.) and multiple rows with understory vegetation by elm (Ulmus minor L.) and poplar, respectively. Tree water consumption was determined through sapflow measurements. The seasonal reference evapotranspiration (ETo) for field crops was 876–995 mm without wind breaks and dropped to less than half through multiple row wind breaks with understory vegetation (50 m spacing). Tree water consumption was 1125–1558 mm for poplar and 435 mm for elm. Among the wind break crop systems, elm wind breaks resulted in the highest reductions of water consumption, followed by single row poplars, at spacing of 50 and 100 m, respectively. However, elm grows much slower than poplar, so poplars might be more attractive for farmers. Furthermore, single row wind breaks might by much easier to be integrated into the agrarian landscape as they consume less space.

Water consumption of Populus alba trees in tree shelterbelt systems in Central Asia – a case study in the Chui Valley, South Eastern Kazakhstan

Agriculture in Central Asia largely relies on irrigation. The water is withdrawn from the rivers of the region, which predominantly originate from snowfields and glaciers. Due to the global warming these water resources are expected to decline substantially, resulting in an aggravation of the already existing water scarcity. Tree shelterbelt systems as the most prominent practice of agroforestry in Central Asia are reported to help to reduce water consumption in irrigated agriculture. Though, studies about water consumption of the shelterbelts are lacking. Therefore, the objectives of this study are to investigate (1) the water consumption of Populus alba trees in a shelterbelt system in Central Asia and (2) analyze the influence of the local climatic conditions on the sap flow of such a shelterbelt. P. alba is one of the most important shelterbelt trees in Central Asia. Tree water consumption was assessed through sap flow measurements on three trees in a crop shelterbelt system in the Chui Valley in SE Kazakhstan during June and July 2016. The average daily water consumption were 187.6 l/d, 44.8 l/d, and 160 l/d for the trees, respectively. These results were extrapolated for a representative shelterbelt section. Water consumption of that section was 7.8 mm/d, while average ETo was 5.3 mm/d. Considerable influences of water vapor saturation deficit, air temperature and relative humidity on the sap flow could be observed. Solar radiation played a role, too, whereas little or no influence for wind speed was found.

Effect of wind speed and direction on forces acting on shade nets covering orchard trees

The use of nets and screens to cover orchards has greatly expanded during the last decade, since the nets protect the trees from excessive radiation, strong winds, hail and insects. Furthermore, recent studies have shown that, in certain orchards, the nets can significantly reduce the water consumption of trees. The nets are usually stretched above the trees and are fixed to the supporting poles by cables that run all around the net circumference. In this study, experiments were done to determine the forces acting on a horizontal shade net that covered an orchard (232×100 m(2)) in which peach trees were grown. A net section of 40×6 m(2), at an upwind edge of the net-house, was used to measure the forces. Sixty load cells that were evenly distributed on the section circumference were used to attach the net to the net-house cables. Results show that the force acting on the net at the point where the load cell is attached to the net is a second-order polynomial of wind speed. The forces acting on the net were stronger at the points where the net was attached to a cable at the outer edge of the net-house. At points where the net was attached to inner cables of the net-house, the forces were smaller. Extrapolating the second-order polynomial, it was shown that, at a wind speed of 150 km h(-1), the largest force acting at the point where the load cell was attached to the net could be 50 kg.

Tree Shelterbelts as an Element to Improve Water Resource Management in Central Asia

In Central Asia, agriculture, notably irrigated agriculture, is the largest water consumer. Currently, flood and furrow irrigation are the dominant irrigation methods in Central Asia, in particular in the post-Soviet countries. Against the background of current and increasing competition for water—e.g., through reduced river runoffs in the course of climate change—water consumption of agriculture needs to be reduced. On the field plot level, improved irrigation technologies, like drip irrigation or plastic mulch, can reduce water consumption substantially. Alternatively, tree lines as wind breaks (shelterbelts) also can reduce crop water consumption, as shown by research from many drylands around the world. As previous research has concentrated on crop water consumption and not on tree water consumption, this paper brings the two together, in order to approach a more holistic picture, in how far shelterbelt systems, including the trees, may have the potential to save water or not. Crop water consumption was assessed through the Penman–Monteith approach for corn, wheat, potato, barley, and pear under open field conditions and under an assumed influence of a tree shelterbelt. Tree water consumption was investigated through sap flow measurements. Crop water consumption was reduced by 10–12% under influence of a shelterbelt compared to open field conditions. When water consumption of shelterbelts was added, a slight reduction of water consumption of the whole crop-shelterbelt system was found for corn, potato, and pear under the assumption 25 ha (500 × 500 m) field sizes. Under an assumption of 4 ha (200 × 200 m) field size, water consumption of the whole crop-shelterbelt system was higher for all crops investigated except for pear. The results suggest that shelterbelts may play a role in improving water resource management in Central Asia in the context of water demanding crops, like corn or cotton. In further research, other effects of shelterbelts, like increased crop yields and additional income from trees, need to be investigated.

Response of young bearing olive trees to irrigation-induced salinity

Expansion of irrigated olives, combined with prevalence of water containing dissolved salts, leads to irrigation-induced exposure of olive trees to salinity. Root zone salinity can rise either as a function of increasing input irrigation water salinity (ECi) or relative reductions in water for leaching. We investigated five ECi levels from 0.5 to 11.0 dS m−1 with a constant leaching fraction (LF) of 0.29 and five leaching levels from 0.05 to 0.44 (drainage: irrigation ratio) with water of ECi = 5.0 dS m−1 on young bearing Olea europaea cv Barnea olive trees grown in 2.5 m3 weighing-drainage lysimeters over three years. Tree-scale response to increased salinity did not demonstrate any sign of a threshold value and was not differentiated by the cause of salinity, be it changes in input irrigation water salt concentrations or changes in LF. Soil salinity, measured as electrical conductivity of saturated soil paste extract (ECe) and maintained at stable levels over time, decreased tree water consumption and tree size measured as trunk area or above-ground biomass by 40–60 % as it increased from 1.2 to around 3.5–4.0 dS m−1. Further increases in ECe to as high as 7.5 dS m−1 brought these parameters to 20–30 % of the treatment with low salinity. Fruit yield also decreased with increasing salinity, albeit with less drastic relative effects. An analytical model calculating water and salt balance and subsequent evapotranspiration or biomass as a function of irrigation water quantity and salinity successfully predicted the measured results.

Combining sap flow measurements and modelling to assess water needs in an oasis farmland shelterbelt of Populus simonii Carr in Northwest China

Farmland shelterbelts provide an ecological protection screen for an oasis but exhibit high mortality in the face of water shortage. It is necessary to understand farmland shelterbelt tree transpiration under different levels of water stress and stand ages for proper management. Sap flux measurement techniques and models are among the most useful method to detect water stress and to evaluate plant water consumption. The usefulness of both methods decreases, however, when applied to species, such as Populus simonii Carr, that have an outstanding tolerance to drought and a remarkable capacity to take up water from drying soils. Our hypothesis is that analysis using simultaneous measurements of sap flow and models in the same trees is useful for assessing the irrigation needs in farmland shelterbelts. To test our hypothesis, we analysed the relationships between canopy transpiration, canopy conductance, relative extractable water and atmospheric factors in a farmland shelterbelt and evaluated the effectiveness of the model. Measurements were made during one growing season. The time courses of sap flow measured and modelled on days of contrasting weather and soil water conditions were analysed to evaluate the usefulness of the method to assess the crop water needs. We calculated the daily tree water consumption from sap flow measurements and the parameterized modified Jarvis-Stewart model, and we evaluated the model’s usefulness to assess the final water needs under water stress and stand ages for farmland shelterbelt irrigation. The transpiration decreased as the soil drought increased, and it increased as the atmospheric drought increased. The time course of the water needs showed that the occurrence of water stress in the farmland shelterbelt trees had a large impact on their water consumption, which increased as the water stress decreased, following the equation y=1/[1+e−60.67×(REWx−0.402)]. The simultaneous use of modelling and tree structural data increased the reliability of assessing water needs from youth to maturity. A similar analysis with the water consumption values, from which stand age values were derived, showed that water needs increased with the tree age following the equation y=847−844/[1+(x/87.9)1.9]. We conclude that compared to the use of sap flow records alone, the simultaneous use of sap flow records and model values provides more detailed information to assess water needs in a farmland shelterbelt, which has an important significance for farmland shelterbelt protection.

基于热扩散技术的三倍体毛白杨单木及林分蒸腾耗水研究

PDF HTML阅读 XML下载 导出引用 引用提醒 基于热扩散技术的三倍体毛白杨单木及林分蒸腾耗水研究 DOI: 10.5846/stxb201409171846 作者: 作者单位: 国家开放大学,北京林业大学,黑龙江省大庆市林业局,北京林业大学,北京林业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业公益性行业科研专项经费重大项目(201004004);北京林业大学"985"优势学科创新平台开放基金(000-1108003) Study of transpiration and water consumption of triploid Populus tomentosa at individual tree and stand scales by using thermal dissipation technology Author: Affiliation: The Open University of China,Beijing Forestry University,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:定量分析单木及林分的蒸腾耗水特征,是林木水分管理的关键环节。采用热扩散式边材液流检测技术,结合自动气象站,对三倍体毛白杨树干边材液流及环境因子进行了连续2年的动态观测。结果表明:(1)单株尺度上,三倍体毛白杨边材液流速率日变化在晴天表现为"单峰型",关键影响因子为水汽压亏缺(VPD)和太阳辐射(Qs),日平均液流速率在4-10月分别为0.65×10-3、2.12×10-3、2.09×10-3、1.78×10-3、1.84×10-3、1.76×10-3、1.04×10-3 cm/s;(2)林分尺度上,三倍体毛白杨在2008、2009年(栽植第4年和第5年)的蒸腾耗水量分别为339.52和410.62 mm,主要影响因素为气孔导度(Gc)、相对湿度(RH),以及VPD;(3)多元线性回归模型可以较好的模拟三倍体毛白杨边材液流速率对环境因子的响应特征(P < 0.01,2008年),模型预测值较实测值偏大6.39%(2009年),二者极显著线性相关(R2=0.910,Sig.=0.00054,n=1008)。 Abstract:Quantitative analysis of the transpiration and water consumption characteristics at the individual tree and stand scales of forests is critical for forest water management. Developing fast-growing and high-yielding poplar plantations has been identified as a major solution to the shortage of wood fibers in China, because of the strong demand for fibrous products for the large population and limited land resources. The triploid Populus tomentosa has been one of the most widely planted species in recent years due to its superior growth vigor and high timber yield. Accurately measuring the transpiration and water consumption of trees is essential for regulating water use in triploid P. tomentosa plantations. In this study, thermal dissipation probe (TDP) monitoring technology was combined with an automatic weather station to investigate the transpiration and water consumption of triploid P. tomentosa at the individual tree and stand scales over two years. The response of sap flow velocity (Vsp) in P. tomentosa trees to environmental factors, including solar radiation (Qs), air temperature (Ta), relative humidity (RH), wind speed (WS), soil water content (SWC), soil temperature (Ts), and vapor pressure deficit (VPD), were analyzed using a multiple linear regression model. The results showed that (1) the daily variation in sap flow velocity in individual P. tomentosa trees was significantly affected by the Qs and VPD. Diurnal variation in Vsp for individual trees had a unimodal pattern on sunny days. The flow rate rose from nearly zero at sunrise to a maximum at around 13:00 local time and decreased gradually to nearly zero by midnight. In the growing season (from April to October), the average Vsp for each month was 0.65 × 10-3, 2.12 × 10-3, 2.09 × 10-3, 1.78 × 10-3, 1.84 × 10-3, 1.76 × 10-3, and 1.04 × 10-3 cm/s, respectively. The results of the correlation analysis showed that the Vsp correlated significantly (α = 0.01) with the Qs, Ta, WS, RH, SWC, Ts, and VPD. With the exception of RH, all correlations were positive. The VPD and Qs had stronger effects on Vsp than SWC at a daily variation scale. (2) The water consumption of the P. tomentosa stand was 339.52 and 410.62 mm during the growing season in the fourth and fifth years after planting (2008 and 2009), respectively. The water consumption at the stand level was significantly affected by stomatal conductance (Gc), RH, and VPD. The variation in average daily water consumption followed a "low-high-low" unimodal pattern in the growing season and high water consumption values were recorded in August 2008 and June 2009. The main factors that drove the seasonal changes in water consumption in the stand were Gs, RH, and VPD. Lastly, (3) the regression model, with the measured environmental factors as independent variables, explained the variation in Vsp well during the growing season in 2008 (P < 0.01). When the constructed model was used to predict the Vsp in the growing season in 2009, the simulated values correlated well with the measured values (R2 = 0.910) but was 6.39% higher than the measured values on average. 参考文献 相似文献 引证文献

Central European hardwood trees in a high‐CO2 future: synthesis of an 8‐year forest canopy CO2 enrichment project

Summary Rapidly increasing atmospheric CO2 is not only changing the climate system but may also affect the biosphere directly through stimulation of plant growth and ecosystem carbon and nutrient cycling. Although forest ecosystems play a critical role in the global carbon cycle, experimental information on forest responses to rising CO2 is scarce, due to the sheer size of trees. Here, we present a synthesis of the only study world‐wide where a diverse set of mature broadleaved trees growing in a natural forest has been exposed to future atmospheric CO2 levels (c. 550 ppm) by free‐air CO2 enrichment (FACE). We show that litter production, leaf traits and radial growth across the studied hardwood species remained unaffected by elevated CO2 over 8 years. CO2 enrichment reduced tree water consumption resulting in detectable soil moisture savings. Soil air CO2 and dissolved inorganic carbon both increased suggesting enhanced below‐ground activity. Carbon release to the rhizosphere and/or higher soil moisture primed nitrification and nitrate leaching under elevated CO2; however, the export of dissolved organic carbon remained unaltered. Synthesis. Our findings provide no evidence for carbon‐limitation in five central European hardwood trees at current ambient CO2 concentrations. The results of this long‐term study challenge the idea of a universal CO2 fertilization effect on forests, as commonly assumed in climate–carbon cycle models.

Assessing water stress in a hedgerow olive orchard from sap flow and trunk diameter measurements

We used sap flow and trunk diameter measurements for assessing water stress in a high-density ‘Arbequina’ olive orchard with control trees irrigated to replace 100 % of the crop water needs, and 60RDI and 30RDI trees, in which irrigation replaced ca. 60 and 30 % of the control, respectively. We calculated the daily difference for both tree water consumption (\( D_{{E_{\text{p}} }} \)) and maximum trunk diameter (DMXTD) between RDI trees and control trees. The seasonal dynamics of \( D_{{E_{\text{p}} }} \) agreed reasonably well with that of the stem water potential. We identified peculiarities on the response \( D_{{E_{\text{p}} }} \) to changes in water stressing conditions, which must be taken into account when using the index. An analysis of the water stress variability in the orchard is required for choosing the instrumented trees. The reliability of the DMXTD index was poorer than that of \( D_{{E_{\text{p}} }} \). The maximum daily shrinkage (MDS) was not a reliable water stress indicator.

山地梨枣树耗水特征及模型

The regulation of water consumption by mountain jujube trees,jujube pear-like,has not been previously researched in a systematic fashion because of differences among the jujube samples,including age,variety,canopy morphology,meteorological conditions,and land surface conditions.Numerical simulation is an effective and convenient method to investigate the patterns of water consumption of trees,including jujube trees.Therefore,this paper introduces a mathematical model(HYDRUS-1D) to simulate the soil moisture requirements for jujube pear-like. First,to develop the model,the forecast parameters of the HYDRUS-1D model,such as soil properties,weather conditions,leaf area index(LAI),root distribution,and basal crop coefficient,were measured in the northern hilly area of Shannxi Province,China,from 2008 to 2010.Second,the dynamic characteristics of soil moisture in a rain-proof plot experiment were roughly simulated using the HYDRUS-1D model,then,we adjusted the model so that the simulated results better fit the measured data of soil moisture.We inversely extrapolated the parameters of soil water stress coefficient and extinction coefficient,which determine the values of the potential transpiration and potential evaporation,respectively,for the atmospheric boundary conditions.Finally,using the parameters we estimated,we used the HYDRUS-1D model to predict water consumption by eight-year-old jujube pear-like trees in the field. The results showed the following.(1) The changes in LAI of jujube pear-like were consistent with a Gaussian function from germination to fruit ripening.Average LAI of jujube pear-like increased from young to old trees,but the inter-annual differences in LAI decreased in trees that were older than six years.(2) Root depth of jujube pear-like increased linearly with the age of the tree.At the same time,the distribution of capillary roots decreased linearly with an increase in the root depth.The percentage of capillary roots at a depth of 40 cm was more than 70%.(3) To obtain the boundary conditions of the HYDRUS-1D model,we used LAI and the extinction coefficient combined with the crop coefficient to calculate the daily reference evapotranspiration.Fitting the model to the data indicated that,when extinction coefficient of mountain jujube pear-like was 0.52,the measured data of soil moisture fit the simulation quite well.(4) The correlation coefficient of simulated values and measured data of soil water storage reached 0.89,which proved that the parameters of the model with respect to water consumption of jujube pear-like were reliable and that the HYDRUS-1D model could simulate well the dynamic process of soil moisture changes and accurately estimate the water requirements of jujube pear-like.(5) As a result,cumulative evaporation of mountain jujube pear-like was 92 mm,and cumulative transpiration was 175 mm.The total water volume consumed by eight-year-old jujube pear-like trees,from germination to harvest,was 267 mm.Based on the actual amounts of local rainfall and water resources,jujube pear-like should be irrigated two to three times during its flowering and fruiting periods,and water application depths should reach 30—40 mm to meet the growth requirements of this crop plant.