The leaf nutrient, biomass and carbon reserve of 9-year-old Populus×euramericana cv. ‘74/76’ stump grafting stand with 26-year-old P.×xiaozhuanica W.Y.Hsu et Liang cv.‘Popularis’as rootstock, 26-year-old P.×xiaozhuanica W.Y.Hsu et Liang cv.‘Popularis’ and 9-year-old P.×euramericana cv. ‘74/76’ planting stands were compared. The result showed that the average increment and the annual average increment of stump grafting stand were greater than the two planting stands. The total nitrogen content in leaves of stump grafting stand was the highest, and it was 1.26 times and 1.05 times as much as that of the planting stands of Populus×xiaozhuanica W.Y.Hsu et Liang cv.‘Popularis’ and P.×euramericana cv. ‘74/76’ separately. The total phosphorus content of stump grafting stand was 1.3 times as much as that of planting stand of 26-year-old P.×xiaozhuanica W.Y.Hsu et Liang cv.‘Popularis’, but there was little difference between stump graftin stand and planting stand of 9-year-old P.×euramericana cv. ‘74/76’. The total potassium of stump grafting stand was 46.6% and 95.8% lesser than that of the planting stands of P.×xiaozhuanica W.Y.Hsu et Liang cv.‘Popularis’ and P.×euramericana cv. ‘74/76’. The biomass of aerial parts and the biomasses of trunk, branches and leaves of stump grafting stand were 1.84, 1.80, 1.76, and 3.00 times as much as that of planting stand of P.×euramericana cv. ‘74/76’ separately. The total root biomass of the stump grafting stand was 1.42 times and 7.68 times as much as that of planting stands of 26-year-old P.×xiaozhuanica W.Y.Hsu et Liang cv.‘Popularis’ and 9-year-old P.×euramericana cv. ‘74/76’. There was an obvious advantage in carbon reserve from all the parts of the stump grafting stand and the carbon sequestration capacity was the highest, which was 2.66 times and 1.62 times as much as that of planting stands of 26-year-old P.×xiaozhuanica W.Y.Hsu et Liang cv.‘Popularis’ and 9-year-old P.×euramericana cv. ‘74/76’. These showed that the stump grafting stand had more advantages than planting stands.

本研究采用由热扩散植物液流技术测算得到的时间步长10 min的樟子松蒸腾速率数据,结合同步观测得到的冠层微气象要素值,分析了毛乌素沙区20年生樟子松主要生长季节蒸腾耗水规律及其冠层微气象的关系。结果表明:(1)樟子松蒸腾速率具有明显的时间变化特征。多云天气日,蒸腾速率日内变化总体呈多峰曲线趋势,单株蒸腾速率(Tr)在4-9月各月白天(6:00-19:00)的平均值为0．36-0．85 L．h-1;晴天日,除9月蒸腾速率日内变化呈多峰曲线趋势外,其余各月总体趋势呈单峰曲线,9月时Tr在10:00左右、13:00左右、15:00左右出现峰值,在 14:00左右出现谷值。4-8月各月日内Tr在10:00左右出现峰值。4-9月各月Tr白天平均值为0．37-0．83 L· h-1;阴天天气日,蒸腾速率日内变化总体呈单峰曲线趋势,日内Tr最大值出现在10:00左右。4-9月各月Tr白天 (6:00-19:00)平均值为0．29-0．63 L·h-1。在日际变化或季节变化方面,从4月份起,樟子松蒸腾耗水量逐渐增加,月耗水量在7月达到最高值,此后有所减小。4-9月总耗水量为1 143．7 mm,日平均为6．25 mm,7月份月耗水总量相对最大。4、5、6、7、8及9月耗水量分别占主要生长季节总量的10．76％、13．62％、14．05％、24．56％、 19．47％、17．52％。(2)主要生长期内,Tr与冠层太阳总辐射(Ra),空气温度(Ta)、湿度(RH),风速(V)等气象要素有很好的复相关性,并通过显著性检验(a=0．01),且各月内影响樟子松蒸腾的最主要气象因子都是Ra。

通过对毛乌素地区4种树苗进行盆栽水分胁迫试验,研究了5种水分条件下4种树苗的水势、枝条相对含水量、相对电导率、叶绿素含量和脯氨酸含量等生理指标,比较了各树苗的耐旱能力。结果表明:随着干旱胁迫的加剧,4种树苗的相对含水量、叶绿素含量明显降低,相对电导率和脯氨酸含量增加。从正常水分条件至严重干旱胁迫,樟子松、新疆杨、紫穗槐和乌柳的电导率分别为34.19%～39.25%、15.67%～49.77%、18.91%～56.27%和17.01～%77.26%;相对含水量分别为86.47%～58.19%、87.02%～36.42%、90.08%～46.19%和90.67%～51.19%;脯氨酸含量分别为21.26～234.30、32.25～181.93、32.18～284.59、24.76～122.16μg.g-1(FW);叶绿素总量变化不大,阔叶树平均为3.2～71.82 mg.g-1,樟子松为2.2～51.05 mg.g-1;平均比正常水分条件相对含水量降低40.56%、叶绿素含量降低1.33 mg.g-1、相对电导率增加34.19%、脯氨酸含量增加178.14μg.g-1(FW)。研究结果还表明,樟子松和紫穗槐抗旱性较强,较适合在干旱地区栽培利用。

通过对祁连山水源涵养林区的苔藓-青海云杉林、亚高山灌丛、灌木-青海云杉林、中低山灌木林和祁连圆柏以及牧草地等6种植被土壤水分物理性质的测定与计算,比较分析了不同植被的水源涵养能力,建立了主要土壤类型的入渗模型、土壤水分消退方程,评价了不同植被土壤层水文特征及其与植被间的关系。祁连山区主要森林的平均土壤密度均小于1 g·cm-3,土壤的蓄水能力很强但各植被间差异较大。各种森林植被土壤均表现出较高的入渗性能,土壤初渗率、稳渗率及蓄水能力从大到小的次序均为:苔藓-青海云杉林、亚高山灌丛、灌木-青海云杉林、中低山灌木林、祁连圆柏林和牧草地。在相同的环境条件下,森林土壤(山地灰褐土)的保水能力较高,水势消退曲线呈凸形,而牧草地土壤(山地栗钙土)的保水能力相对较弱,水势消退曲线呈凹形。土壤含水量相同时,后者所持水分的有效性更大。

在半干旱黄土丘陵区,采用C IRAS-2型光合作用系统,在不同土壤水分条件下,对2年生杠柳的净光合速率、蒸腾速率、叶片水分利用效率、气孔导度和胞间CO2浓度等叶片气体交换参数的日变化进行了研究。结果表明:土壤水分的变化会影响到杠柳光合速率、蒸腾速率和水分利用效率的日变化过程。相对含水量为31.6%84.9%时,杠柳可以维持较高光合生产力和较高的叶片水分利用效率,杠柳维持正常生理和生长过程所需的最低相对含水量为21.7%。据此认为:杠柳对土壤水分的适应范围较广,适宜栽植在黄土丘陵区水分较少的阳坡、陡坡。

利用CIRAS-2型便携式光合作用仪,测定了不同土壤水分条件下3年生金银花叶片的净光合速率( Pn ) 、蒸腾速率( Tr )及水分利用效率(WUE)等生理参数的光响应过程,阐明其气体交换参数及水分利用效率对土壤水分和光合有效辐射的响应规律,探讨了金银花正常生长发育所需的土壤水分和光照条件。结果表明:金银花叶片的Pn、Tr及WUE对土壤水分和光合有效辐射的变化具有明显的阈值响应;金银花叶片正常生长(同时具有较高Pn 和WUE)的适宜土壤质量含水量(Wm )为121～206 g·kg-1 ,适宜的光合有效辐射为600～1 600μmol·m-2·s-1 ; Wm 为172g·kg-1左右为“最佳高产高效水”,最佳光合有效辐射为800～1 000μmol·m-2·s-1。以光合生理参数为指标对金银花土壤水分有效性及生产力进行分级与评价,确定Wm 在62 g·kg-1以下为“无效水”;Wm在234 g·kg-1以上和62～90 g·kg-1阈值内属于“低产低效水”;在121～145 g·kg-1阈值内为“中产中效水”;在172～206 g·kg-1阈值内为“高产高效水”。

应用英国PPS公司生产的CIRAS-2型光合作用系统,在半干旱黄土丘陵沟壑区,测定了3年生山桃苗在不同土壤水分条件下叶片光合及蒸腾等生理参数的日变化特征。结果表明:不同土壤水分条件下,光合速率、蒸腾速率及水分利用效率的日变化过程呈现不同的变化规律。土壤相对含水量为57. 3%、70. 1%、80. 2%时,光合速率的日最大值分别出现在13: 00、9: 00、13: 00,分别为10. 51、12. 52、9. 25μmol·m-2·s-1 ,日均值分别为6. 83 ±4. 92、6. 40±4. 43、5. 66 ±3. 44μmol·m-2·s-1 ;在其它水分条件下,光合速率有明显午休现象。蒸腾速率的日变化过程与光合速率相似,土壤相对含水量为57. 3%、70. 1%、80. 2%时,最大值均出现在13: 00,日均值分别为1. 91 ±1. 03、3. 27±2. 09、2. 90 ±1. 70μmol·mol- 1。在所测水分范围内水分利用效率上午时段的最大值大部分出现在7: 00或9: 00,下午时段最大值出现的时间相差较大。当土壤相对含水量大于57. 3%时,山桃光合速率下降的主要原因是气孔限制引起的,在其它土壤水分条件下,山桃在上午时段(13: 00以前)以气孔限制为主,而下午时段(13: 00以后)转变为以非气孔限制为主。依据光合速率、蒸腾速率和水分利用效率与土壤水分的定量关系,在半干旱黄土丘陵沟壑区,维持山桃正常生长的适宜水分范围是土壤相对含水量为30. 9%～57. 3% ,应选择阴坡或半阴坡进行栽培。

用L i-6400便携式光合仪,于2004年6—9月测定了毛乌素沙地紫穗槐的光合速率与蒸腾速率,研究了光合速率和蒸腾速率日变化特征及环境因子对其的影响,结果表明:光合速率日变化在6、7月呈双峰型,峰值分别出现在8:00和18:00时,在8、9月呈单峰型,最大值出现在12:00时;蒸腾速率日变化在6、7月呈双峰型,6月峰值分别出现在10:00和18:00时,7月峰值分别出现在10:00和16:00时,低谷都出现在14:00时,在8、9月呈单峰型,峰值出现在12:00时;8月是光合速率和蒸腾速率最大的月份,分别为15.48μmol.m-2.s-1、5.87 mmol.m-2.s-1。在土壤含水量和光强适宜的情况下,空气湿度对紫穗槐光合速率和蒸腾速率的影响大于温度;在6—9月,紫穗槐的水分利用效率呈现波动,表明其光合速率、蒸腾速率受环境影响较大。

在晋西黄土区，研究了荒草地、锦鸡儿灌木林地和刺槐乔木林地3种典型植被不同土层的土壤密度、含水量、贮水能力和入渗性能的差异及其相关性，结果显示：3种植被类型都能有效减小表层（0~20 cm）土壤密度； 3种植被类型表层（0~20 cm）的土壤滞留贮水量较大，锦鸡儿林地（198.80 t·m-3）>刺槐林地（166.10 t·m-3）>荒草地（87.37 t·m-3），20~40 cm土层的土壤滞留贮水量也是锦鸡儿林地（127.30 t·m-3）>刺槐林地（55.60 t·m-3）>荒草地（47.30 t·m-3），表明在3种植被类型中，锦鸡儿林地对晋西黄土丘陵区土壤水分的涵养作用最强；锦鸡儿林地的土壤稳渗速率最大，为1.80 mm·min-1，刺槐林地次之，为1.46 mm·min-1，荒草地依然最小，且锦鸡儿林地土壤的均渗速率最大，为4.81 mm·min-1，其次是刺槐林地，为4.51 mm·min-1，荒草地最小。土壤密度与滞留贮水量呈极显著负相关关系，与土壤初渗速率和均渗速率呈极显著负相关关系，与稳渗速率呈显著负相关关系，非毛管孔隙度与稳渗速率和均渗速率存在极显著相关关系。 Kostiakov模型和Horton模型对晋西黄土区3种植被类型土壤入渗过程模拟的拟合系数高达0.97和0.95，明显优于Philip模型（0.43）。

In order to compare the differences in eco-physiological characteristics between male and female plants and to further understand the ecological adaptability of Rhus typhina Linn., the diurnal variations of photosynthetic parameters and the fluorescence characteristics of male and female plants were determined respectively with photosynthesis system (CIRAS-2) and portable chlorophyll fluorometer (PAM-2100). The relative chlorophyll content was determined with relative chlorophyll content determination (SPAD-502). The length and width of leaf were measured with ruler. The results showed that the SPAD of male was greater than that of the female by 9.6%. The diurnal variation of net photosynthetic rate of male and female plants showed obvious midday depression. The daily mean of net photosynthetic rate of male plant was greater than that of the female by 22.7%, and there was significant difference between them. The daily means of transpiration rate was greater than that of the female by 18.5%. The water use efficiency of male plant was 2.3 μmol·mmol-1, which was greater than that of the female by 21.7%, and there was significant differences between them. The diurnal variations of light use efficiency of male and female plants were similar but the light use efficiency of male was higher. The Fv/Fm of male plant was higher than 0.76 and was higher than that of the female during the measurement period. The female reduced to the lowest which was 0.69 at 13:00 p.m. Both the leaf length and width of female were smaller, but the ratio of length and width was greater compared with the male, and there was significant difference between them. The net photosynthetic rate, water use efficiency and light use efficiency of male were higher than that of female, and it had stronger adaptability to environment.