林业科学  2018, Vol. 54 Issue (9): 147-156   PDF    
DOI: 10.11707/j.1001-7488.20180917
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文章信息

高岚, 刘芸, 熊兴政, 邬静淳, 王萌, 袁贵琼, 欧阳, 任立
Gao Lan, Liu Yun, Xiong Xingzheng, Wu Jingchun, Wang Meng, Yuan Guiqiong, Ou Yang, Ren Li
引种植物水桦与乡土植物桑树对三峡库区消落带水淹的响应
Response of Introduced Plant Betula nigra and Native Plant Morus alba to Flooding in the Draw-down Zone in the Three Gorges Reservoir Area
林业科学, 2018, 54(9): 147-156.
Scientia Silvae Sinicae, 2018, 54(9): 147-156.
DOI: 10.11707/j.1001-7488.20180917

文章历史

收稿日期:2017-04-06
修回日期:2018-06-09

作者相关文章

高岚
刘芸
熊兴政
邬静淳
王萌
袁贵琼
欧阳
任立

引种植物水桦与乡土植物桑树对三峡库区消落带水淹的响应
高岚1, 刘芸1, 熊兴政1, 邬静淳1, 王萌1, 袁贵琼1, 欧阳1, 任立2     
1. 西南大学资源环境学院 重庆 400716;
2. 秀山县武陵山湿地植物工程技术研究开发中心 重庆 409902
摘要:【目的】对桑树与引种植物水桦在三峡库区消落带的生长及光合特性进行比较,探讨这2种木本植物对三峡库区消落带周期性水淹生境的适应性,为消落带植被重建适用树种选择提供理论依据。【方法】在重庆市万州区典型消落带170、175 m 2个高程的台地种植2年生桑树、水桦实生苗,之后自然生长,于每年4月上旬调查其存活率。供试种调查存活率后,于上述台地旁种植2年生桑树、水桦实生苗,2年后于4月上旬春季出露期、7月中旬夏季干旱期、9月底秋季淹水前期测定其生长量(株高、地径、冠幅)、光合特性(叶绿素、叶绿素荧光动力参数及气体交换参数)。【结果】170 m高程桑树、水桦的存活率显著低于175 m高程,而2个高程水桦存活率均大于桑树,其中170 m高程差异显著;170 m高程水桦的生长量均大于桑树,其中株高差异显著。春季出露期(SEP),170 m高程桑树叶片的叶绿素含量高于175 m高程,PnGsTrCi、WUE无明显差异;夏季干旱期(SDP),桑树和水桦170 m高程叶绿素含量及PnGsTrCi均大于175 m高程,其中桑树的CiTr差异显著、水桦的Tr差异显著;秋季水淹前期(PFP),170 m高程水桦的叶绿素含量显著大于桑树,Pn、WUE与175 m高程无明显差异。SEP期,170 m高程桑树的qP、ETR、ΦPSⅡ大于175 m高程;PFP期,水桦在2个高程的ΦPSⅡ、ETR、qP基本与SDP期一致,170 m高程qN大于175 m高程。【结论】乡土树种桑树能通过出露后快速恢复叶片PSⅡ光反应系统的能力,提高光电子的传递速率,增加叶绿素含量而增强光合作用,积累更多有机物恢复生长来适应三峡库区冬季水淹的胁迫;引种植物水桦则通过延长光合作用时间,在桑树进入休眠期后仍保持较高的光能转化效率,积累更多的有机物以应对冬季水淹的过度消耗。桑树和水桦均能在一定程度上适应三峡库区消落带特殊的生境,引种植物水桦较本地树种桑树对于三峡库区消落带生境表现出更强的适应能力,可以考虑用于三峡库区消落带的植被恢复。
关键词:引种植物    水桦    三峡库区    光合参数    荧光动力参数    
Response of Introduced Plant Betula nigra and Native Plant Morus alba to Flooding in the Draw-down Zone in the Three Gorges Reservoir Area
Gao Lan1, Liu Yun1 , Xiong Xingzheng1, Wu Jingchun1, Wang Meng1, Yuan Guiqiong1, Ou Yang1, Ren Li2    
1. College of Resources and Environment, Southwest University Chongqing 400715;
2. Xiushan County Wuling Mountain wetland plants Engineering Research and Development Center Chongqing 409902
Abstract: 【Objective】The growth and photosynthetic characteristics of the native Morus alba and the introduced plant Betula nigra planted in the Three Gorges Reservoir area were compared, and the adaptability of the two woody plants to the periodic flooded habitats of the Three Gorges reservoir zone was investigated to provide a scientific basis for the selection of suitable tree species for the vegetation restoration.【Method】In this study, two-year-old M. alba and B. nigra seedlings were planted on the tableland in typical draw-down zone at altitudes of 170 m and 175 m in Wanzhou, Chongqing. Then the seedlings grew naturally, and their survival rate was investigated in early April each year. After the preliminary experiment of testingsurvival rate, more two-year-old M. alba and B. nigra seedlings were planted on the side of the tableland. After two years, the growth (plant height, ground diameter, crown width) and photosynthetic characteristics (chlorophyll, fluorescence dynamic parameters, gas exchange parameters) were measured in Spring Exposure Period (SEP) of early April, Summer Drought Period (SDP) of mid-July and Pre-Autumn Flooding Period (PFP) at the end of September.【Result】The survival rate of M. alba and B. nigra at altitude 170 m was significantly lower than that at altitude 175 m. The survival rate of B. nigra was higher than M. alba at both altitudes, and the difference between the two species was significant at altitude 170 m. B. nigra grew faster than that of M. alba at altitude 170 m, and the height was significantly different. The chlorophyll content of M. alba at altitude 170 m was higher than that at altitude 175 m in SEP. There was no significant difference in Pn, Gs, Tr, Ci and WUE between the two altitudes. In SDP, the chlorophyll content and Pn, Gs, Tr, Ci of M. alba and B. nigra at altitude 170 m were higher than those at altitude 175 m. The differences in Ci and Tr of M. alba were significant, and the difference in Tr of B. nigra was significant between the two altitudes. In PFP, the chlorophyll content of B. nigra at altitude 170 m was significantly higher than that of M. alba, and there were no significant differences in Pn and WUE between the two species at altitude 175 m. In SEP, the qP, ETR and ΦPSⅡ of M. alba at 170 m altitude were higher than those at 175 m altitude. In PFP, the ΦPSⅡ, ETR and qP of B. nigra at both altitudes were basically similar with those in SDP, however qN of B. nigra at altitude 170 m was higher than that at altitude 175 m.【Conclusion】The native plant M. alba can rapidly recover the ability of the PSⅡ reaction systemof leaves, increase the transfer rate of photoelectron, increase the chlorophyll content and accumulate more organic compound to restore growth after Spring Exposure Period to adapt to the stress of flooding in the Three Gorges Reservoir Area in winter. The introduced plant B. nigra can prolong photosynthesis time, maintain a high efficiency of light energy conversion after M. alba entering dormancy. Thus it can accumulate more organic compound to cope with excessive consumption in winter. Within the range of this experiment, M. alba and B. nigra can adapt to the special habitat of the Three Gorges Reservoir to a certain extent. Compared with the native tree species, the introduced plant had stronger adaptability to the habitat of the Three Gorges Reservoir. It can be used for vegetation restoration in the draw-down zone of the Three Gorges Reservoir area. However, whether or not the introduced plant B. nigra has ecological invasion and whether it can be used as the restoration tree species in the Three Gorges Reservoir area has yet to be studied.
Key words: introduced plant    Betula nigra    Three Gorges Reservoir area    photosynthetic parameters    fluorescence dynamic parameters    

三峡库区冬季正常水位为175 m,在库区形成长约600 km、宽1~2 km的大湖泊;而到夏季,水位降至145 m时,库区两岸出现20~30 m的消落带,出露期最长可达150余天(苏维词,2003)。三峡库区消落带的水位波动引起水、土、光、热、营养元素等关键生态因子的波动,导致生态系统结构和功能发生改变(郭泉水等,2010汤显强等,2012)。原来的陆生生态系统短时间内演变为季节性湿地生态系统,陆生环境物种因不适应新环境而逐步消亡,使得消落带生物多样性减少,生态系统结构和功能趋于简单化,稳定性变差(Abrahams,2008Li et al., 2009苏维词等,2010陶敏等,2011)。

对消落带和河岸带受损生态系统进行植物生态修复是非常有效的治理途径(Lowrance et al., 2000Parolin,2002戴方喜等,2006袁兴中等,2012),然而适用于生境突然改变后的三峡库区消落带植被恢复的种类很少,一些耐干旱的植物不耐水淹,而耐水淹的植物又不耐干旱(杨朝东等,2008黄小辉,2014)。草本植物对消落带植被恢复相对容易(马利民等,2009王强等,2009孙荣等,2010刘维暐等,2011卢志军等,2012),但对于水库两岸地形陡峻,相对高差大的、海拔较高的消落带,草本植物水土保持效果差,木本植物则有利于构建稳定的植物群落(黄小辉等,2012)。室内模拟落羽杉(Taxodium distichum)和池杉(Taxodium ascendens)(李昌晓等,20072008)、秋华柳(Salix variegate)(罗芳丽等,20072008)、澳洲白千层(Melaleuca leucadendron)、蒲桃(Syzygium jambos)(康志等,2007)、枫杨(Pterocarya stenoptera)(贾中民等,2007)、疏花水柏枝(Myricaria laxiflora)(陈芳清等,2008)等木本植物对于水淹逆境有一定的适应性。

从相似生境引种是应对突变生境植被恢复的途径之一。2008年,重庆市林业科学研究院引进水桦(Betula nigra)种子(美国FWSco公司),在三峡库区消落带进行了试种试验,至今长势良好(娄利华等,2010)。为探讨引种植物水桦对三峡库区特殊生境的适应机制,本文以耐逆境能力较强的乡土树种桑树(Morus alba)作为对照(贺秀斌等,2007刘芸等,2011张建军等,2012Liu et al., 2013, 2016黄小辉等,2013Feng et al., 2016),通过对这2种木本植物在三峡库区消落带的生长及光合特性进行比较研究,探讨水桦以及桑树对三峡库区消落带生境的适应能力,为消落带植被恢复适生树种选择提供理论依据。

1 材料与方法 1.1 研究区概况

研究区位于重庆市万州区(108°19′33.87″E,30°36′11.29″N)新田镇溪口乡长江沿岸的麒麟村、玉竹村170~175 m高程消落带。该地区属亚热带季风湿润带,特征为冬暖多雾;夏热多伏旱;春早气温回升快而不稳定,秋长。年平均气温17.7 ℃,年平均年日照时数1 484.4 h,年平均降水1 243 mm。该地区原为农用地和土坎梯田,地势平缓,虽受消落带水位消涨的影响,但依然保持着较好的阶梯状地貌,土壤为紫色土,土层厚度30~60 cm,有机质含量0.8%~2.4%,pH5.0—5.8。

1.2 试验设计

前期预备试验表明,在三峡库区消落带随着高程的降低,木本植物的存活率也随之降低,因此选择170 m高程以上进行试验。供试木本植物为2年生桑树、水桦实生苗。试验地为170、175 m高程的地质条件类似的消落带台地。样方大小20 m(垂直于江岸线)×12 m(与江岸线平行),样方间隔2 m,3个重复。2010年,在样方内按2 m×2 m的株行距分别种植桑树和水桦,苗木存活后自然生长,期间不除草不施肥不打农药,种植后每年4月上旬调查桑树与水桦的存活率。

试种调查存活率后,于2014年4月,在样方旁类似台地内按照上述方式种植2年生桑树和水桦,苗木存活后自然生长。结合三峡库区水位消涨规律和2014年9月—2016年11月实测水位数据(图 1),在苗木退水出露以后,缓苗1个月,分别于2016年4月上旬春季出露期(spring exposure period, SEP)、7月中旬夏季干旱期(summer drought period, SDP)、9月底秋季淹水前期(pre-autumn flooding period, PFP)测量其生长及光合指标。

图 1 2种木本植物桑树和水桦在170 m和175 m高程不同时期株高、地径、冠幅的比较 Figure 1 Comparison of height, ground diameter and crown width growth of two species of M. alba and B. nigra at altitude 170 m and 175 m 字母不同表示差同一时期不同高程异显著,α=0.05。下同。 Different letters indicate significant differences between different altitude in the same period, α=0.05.The same below.
1.3 试验方法

1) 存活率统计2010年种植后每年4月(消落带退水后)对试验区170和175 m高程桑树和水桦的存活棵数分别进行计数,用每个树种的存活棵数除以栽种总数,得到存活率。

2) 生长量测定用精度1 mm的卷尺测量株高(地面到苗木顶芽的距离)和冠幅(树冠东西方向和南北方向的直径均值),精度0.1 mm的游标卡尺测量地径(贴近地面1 cm处的苗木直径),每个树种每个样方随机选取5株共15株进行测量,并做标记,用于下次测量。

3) 叶绿素荧光动力参数测定用JUNIOR-PAM 2100便携式脉冲调制荧光仪(德国,WALZ)测定2)中选取的植株的叶绿素荧光动力参数,每株选取植株上最新完全展开的健康功能叶(倒5叶)进行测定。测定前先将叶片暗适应30 min,照射检测光测得初始荧光(Fo)。然后用饱和脉冲光(10 000 μmol·m-2s-1)激发,使原初电子受体QA全部处于还原状态,测定最大荧光(Fm)。接着,打开测量光(600 μmol·m-2s-1),待Ft稳定后,取此时的Ft为稳态荧光(Fs),然后打开一个同样强度的饱和脉冲光,得到Fm′。之后将样品用黑布快速罩住,打开远红光(7 μmol·m-2s-1),得到Fo′,Fv=Fm-Fo。最大光化学效率(Fv/Fm)、光化学猝灭系数(qP)、非光化学猝灭系数(qN)、实际光化学效率(ΦPSⅡ)和电子传递速率(ETR)均由仪器自动给出。

4) 气体交换参数测定用美国LI-COR公司生产的Li-6400光合作用测量仪,在连续晴朗无风的天气条件下对3)中所述叶片在06:00—18:00间进行光合作用日变化的测量,每2 h测定净光合速率(Fn)、胞间CO2浓度(Ci)、蒸腾速率(Tr)、气孔导度(Gs)。水分利用效率(WUE)=Pn/Tr

5) 叶绿素含量测定采用混合液(丙酮(V):乙醇(V):水(V)=4:5:1)浸提法测定叶绿素含量(萧浪涛等,2005)。采集3)中所述植株叶片,每株8~10片,每个样称取0.1 g,加入10 mL混合液浸提10~12 h,得到的浸提液用Spectrumlab22可见分光光度计在波长652 nm下比色,计算叶绿素含量。

1.4 数据统计分析

采用Microsoft Excel 2013和Origin Pro 2016对试验数据进行初步计算与作图,SPSS 23.0进行统计分析,Duncan法比较试验处理间的差异显著性。

2 结果与分析 2.1 水淹对三峡库区消落带2种木本植物生长的影响

1) 水淹对2种木本植物存活率的影响

表 1可知,种植2年后,桑树与水桦存活数量趋于稳定。170 m高程桑树的存活率显著低于175 m高程;170 m水桦的存活率显著低于175 m高程,2个高程水桦存活率均大于桑树,其中170 m高程树种之间的存活率差异显著(P<0.05)。

表 1 2种木本植物桑树和水桦在170 m和175 m高程的存活率 Tab.1 The survival rate of woody plants Betula nigra and Morus alba at altitude 170 m and 175 m

2) 水淹对2种木本植物株高、地径、冠幅的影响由图 1可知,桑树在SEP、SDP、PFP期170和175 m高程株高均差异显著(P < 0.05)。水桦在SEP、SDP、PFP期170和175 m高程株高差异均不显著(P>0.05)。桑树在SEP、SDP、PFP期170和175 m高程地径差异均显著(P < 0.05);水桦在SEP期170和175 m高程地径差异不显著(P>0.05);SDP期差异显著(P < 0.05);PFP期差异显著(P < 0.05)。桑树在SEP、SDP、PFP期170和175 m高程冠幅均差异显著(P < 0.05)。水桦在SEP期170和175 m高程冠幅差异不显著(P>0.05);SDP、PFP期差异显著(P < 0.05)。

桑树和水桦在175 m高程(平均淹水1天)的株高、地径和冠幅在SEP、SDP、PFP时期均大于其在170 m(平均淹水128天)高程的,表明淹水胁迫对桑树和水桦植株生长有影响,且对桑树的影响大于水桦。

2.2 水淹对三峡库区消落带2种木本植物光合作用的影响

1) 水淹对2种木本植物叶绿素含量的影响由图 2可知,对于桑树叶绿素含量,SEP期170和175 m高程差异不显著(P>0.05);在SDP期,170 m的叶绿素含量比175 m高,差异显著(P<0.05);在PFP期,170和175 m高程差异不显著(P>0.05)。对于水桦叶绿素含量,在3个时期170和175 m高程差异均不显著(P>0.05),表明桑树经冬季水淹出露后,能增加自身的叶绿素含量,从而增强光合作用积累更多有机物质,以此来应对下一个淹水期的过度消耗。

图 2 2种木本植物桑树和水桦在170 m和175 m高程叶绿素含量 Figure 2 Chlorophyll content of woody plants M.alba and B. nigra at altitude 170 m and 175 m

2) 水淹对2种木本植物叶绿素荧光动力参数的影响

图 3可知,桑树在SEP期,170 m高程的ΦPSⅡ、ETR、qP均比175 m高程的大,且差异显著(P < 0.05),表明170 m高程桑树在经历长时间水淹后,不仅能快速恢复叶片PSⅡ光反应系统的能力,还能进一步促进光反应系统的开放,提高光电子的传递速率,增强对光电子的利用能力;2个高程的qNFv/Fm大小无显著差异(P>0.05);在SDP期,170和175 m高程的ΦPSⅡ、ETR一致,170 m高程的Fv/FmqN比175 m高程的低,qP比175 m高程的高;在PFP期,170 m高程的ΦPSⅡ、ETR、qP比175 m高程的大,qN较小,两者Fv/Fm一致。

图 3 2种木本植物桑树和水桦在170 m和175 m高程不同时期叶绿素荧光参数 Figure 3 Chlorophyll fluorescence parameters of woody plants M.alba and B.nigra in different periods of altitude 170 m and 175 m

水桦SEP期,170 m高程的ΦPSⅡ、ETR、qNqP均比175 m高程的小,而Fv/Fm一致,差异均不显著(P>0.05);SDP期,175 m高程的ΦPSⅡ、ETR、qPqN均比170 m高程的大,而Fv/Fm比170 m高程的小,差异均不显著(P>0.05);PFP期,2个高程的ΦPSⅡ、ETR、qP变化保持与SDP期一致,170 m高程qN比175 m高程略大,而Fv/Fm比175 m高程小,表明水桦在进入PFP期后,光反应系统开放程度未受影响,在该时期下依然保持较高的光能转化效率。

2.3 水淹对2种木本植物气体交换参数的影响

由如图 4可知,SEP期桑树在170和175 m高程的Pn日均值差异不显著(P>0.05),且两者日变化趋势一致,均呈双峰曲线变化。SDP期,170和175 m高程的Pn日均值差异不显著(P>0.05),两者日变化总体上呈双峰曲线变化。PFP期,桑树在170和175 m高程的Pn日均值差异显著(P<0.05),表明桑树在PFP期,能够通过增强光合作用从而应对下一个淹水期带来的过量物质消耗。170 m高程Pn日变化呈双峰曲线;175 m高程的Pn日变化呈单峰曲线。

图 4 2种木本植物桑树和水桦在170 m和175 m高程不同时期气体交换参数 Figure 4 Gas exchange parameters of woody plants M. alba and B. nigra in different periods of altitude 170 m and 175 m

SEP期水桦在170和175 m高程的Pn日均值差异不显著(P>0.05),两者Pn均呈双峰曲线变化。SDP期,170 m高程和175 m高程的Pn日均值差异不显著(P>0.05), 其变化趋势一致,呈单峰曲线变化。PFP期,170和175 m高程的Pn日均值差异不显著(P>0.05)。170 m高程水桦的Pn呈双峰曲线变化;175 m高程水桦的Pn变化趋势呈单峰曲线。

桑树在170和175 m高程的Gs均值差异不显著(P>0.05);水桦在170和175 m高程的Gs均值差异不显著(P>0.05)。Gs大小顺序为水桦>桑树,同一树种2个高程的Gs差异不显著(P>0.05)。

桑树在170和175 m高程的Tr均值差异不显著(P>0.05);水桦在170和175 m高程的Tr均值差异不显著(P>0.05);同一高程下,Tr大小为水桦>桑树。桑树在170和175 m高程的Ci均值差异不显著(P>0.05);水桦在170和175 m高程的Ci均值差异不显著(P>0.05)。桑树在170和175 m高程的WUE均值差异显著(P < 0.05);水桦在170和175 m高程的WUE均值差异不显著(P>0.05)。170 m高程桑树的WUE比175 m高程的小,170 m高程水桦的WUE与175 m高程的差异不显著(P>0.05)。

3 讨论

170 m高程的2年生桑树和水桦在种植2年以后,存活的数量趋于稳定,存活率分别为47%和64%,较175 m高程的存活率91%、95%差异显著,说明反季节水淹对桑树和水桦的存活率都有显著影响,且水桦较桑树有更强耐水淹能力。黄先智等(2013)在云阳县黄石镇中湾村的三峡库区消落带种植桑树3年后,调查在170~171 m的存活率仅为7.8%,与175 m存活率87%差异极显著,与本试验存活率有较大差异。其原因可能是三峡库区消落带地形、地貌复杂多样,土壤类型、土质、坡度差异大,本文选择的试验地水淹前曾是农田,土层较厚且是台地,春季种植后,桑树、水桦生长迅速。

桑树和水桦在175 m高程(根据图 1求得平均淹水1天)的生长量均大于其在170 m(平均淹水128天)高程下的增长量,表明淹水胁迫对桑树和水桦植株生长有影响,并且这些影响可以直接反映到株高、地径、冠幅等生长指标(图 2)。有研究表明, 水淹处理会抑制植株的生长(Kozlowski,1997Pezeshki,2001),可能是缺氧的环境使它们产生无氧呼吸,大量消耗光合产物而积蓄的物质少,影响翌年生长。

叶绿素是植物进行光合作用的主要色素,因此叶绿素含量的高低与植物净光合速率关系十分密切。研究表明,淹水可使植物的叶绿素含量减少或光合作用减弱,而不同植物对淹水胁迫的响应不同(Nilsamranchit et al., 1996)。在SEP期,170 m高程桑树叶片的叶绿素含量高于175 m高程(图 3),PnGsTrCi、WUE无明显差异(图5),表明桑树出露后,通过增加叶绿素含量而增强光合作用,积累更多有机物恢复生长,这可能是桑树对于冬季水淹的适应机制。水桦在170 m高程的叶绿素含量、PnGsTrCi、WUE均小于175 m高程,但差异不显著。在SDP时期,桑树和水桦170 m高程叶绿素含量及PnGsTrCi均大于175 m高程,其中桑树的CiTr差异显著、水桦的Tr差异显著(P < 0.05),表明它们能通过合成更多的叶绿素增强光合作用,弥补淹水带来的影响,积累大量的光合产物利于生长,以应对下一个淹水期的物质过量消耗(张艳红等,2006Huang et al., 2013)。在PFP期,170 m高程水桦的叶绿素含量明显大于桑树(P < 0.05),表明桑树较水桦更早进入休眠期,细胞生理活性降低,叶绿素降解进程加快,光合作用能力减弱;而此时,水桦仍保持较高的Pn、WUE,光合作用时间延长有利于积累更多的干物质,以应对冬季水淹造成的有机物过度消耗,这可能是水桦对冬季水淹的一种适应机制。

叶绿素荧光与植物光合作用中各个反应过程紧密相关,任何逆境对光合作用各过程产生的影响都可通过体内叶绿素荧光诱导动力学变化反映出来(Rohacek,2002Force et al., 2003)。本研究中,170 m高程桑树在SEP期的qP、ETR、ΦPSⅡ大于175 m高程,表明170 m高程桑树在经历长时间水淹后,不仅能快速恢复叶片PSⅡ光反应系统的能力,还能进一步促进光反应系统的开放,提高光电子的传递速率,增强对光电子的利用能力,这与桑树在SEP期通过增加叶绿素含量而增强光合作用,积累更多有机物恢复生长来适应冬季水淹的结论一致。水桦在PFP期2个高程的ΦPSⅡ、ETR、qP基本与SDP期一致,170 m高程qN大于175 m高程,表明在进入PFP期后,水桦的光反应系统开放程度未受影响,在该时期下依然保持较高的光能转化效率,且为了保护光反应系统,通过非光化学猝灭(qN)过程来调整过量能量的耗散,以热形式耗散掉不能用于光合作用的光能,从而保护PSⅡ反应中心免受因吸收过多光能而引起的光氧化和光抑制伤害,这与水桦通过延长光合作用时间以应对冬季水淹的适应机制结论一致。

4 结论

本试验范围内,本地种桑树能通过出露后增加叶绿素含量而增强光合作用,积累更多有机物恢复生长来适应冬季淹水,引种植物水桦能通过延长光合作用时间以生成更多有机物来应对冬季淹水的胁迫。桑树和水桦2种木本植物通过不同的方式适应三峡库区消落带反季节水淹的特殊生境,这对于三峡库区消落带受损生态系统植被恢复及群落构建具有重要的应用价值。同时本试验中,水桦较桑树对于三峡库区消落带生境表现出更强的适应能力。但关于桑树和水桦能否长期适应三峡库区消落带特殊生境,以及引种植物水桦是否具有生态入侵性、能否作为三峡库区消落带恢复树种加以推广等问题,还有待继续试验及深入研究。

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