• 中国中文核心期刊
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  • 第二届国家期刊奖提名奖
Volume 34 Issue 6
Dec.  2021
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Differences in the Response of Radial Growth and Intrinsic Water Use Efficiency of Robinia pseudoacacia to Climatic Factors in Minquan of He'nan Province and Baishui of Shaanxi Province

  • Corresponding author: SUN Shou-jia, ssj1011@163.com
  • Received Date: 2021-03-31
    Accepted Date: 2021-08-10
  • Objective To analyze the response of radial growth and intrinsic water use efficiency (WUEi) of Robinia pseudoacacia to climate factors at different locations, and to determine the dominant factors affecting the growth and water use mechanism, so as to provide reference for the management of R. pseudoacacia plantations in China under climate change. Method The ring width chronologies were established in Minquan (MQ) of He'nan Province and Baishui (BS) of Shaanxi Province. The stable carbon isotopic composition (δ13C) of tree ring was measured to calculate the WUEi. The differences in the response of R. pseudoacacia to climatic variation were analyzed with meteorological data. Result The plantations at the two locations were in similar age. The tree-ring width at BS presented a trend of initially increasing and thereafter decreasing with the increase of tree age, whereas at MQ, the tree-ring width showed a linear decreasing trend with tree age increase. The trends of basal area increment (BAI) of R. pseudoacacia at the two locations were similar, presenting a trend of initially increasing and thereafter decreasing with the increase of tree age. The δ13C value and WUEi of the trees in MQ were lower than those of BS. The Pearson correlation results showed that on a monthly scale, the STD index of R. pseudoacacia in the two locations was mainly positively correlated with the summer precipitation and drought index (SPEI) (P < 0.05), and the R. pseudoacacia in BS was significantly negatively correlated with the average precipitation and SPEI in November of the previous year (P < 0.05). The WUEi of trees in MQ was significantly positively correlated with the average temperature and maximum temperature in March and August (P < 0.05), while that of trees in BS was significantly positively correlated with the average temperature, maximum temperature and minimum temperature from March to April of the current year, and June to July of the previous and current year (P < 0.05). The path analysis model showed that on the annual scale, the STD index of R. pseudoacacia in BS had a significant positive effect on the average precipitation and average temperature (P < 0.05), while the R. pseudoacacia in MQ had no significant response to climate factors. The annual average temperature had significantly positive effect on WUEi of trees at both the locations (P < 0.05). Conclusion The average precipitation is the dominant factor influencing the radial growth of R. pseudoacacia at both the locations, and the sensitivity of growth of trees in BS is higher than that of trees in MQ. The average temperature is the dominant factor influencing WUEi at the two locations, and the WUEi of trees in BS is more sensitive to the temperature than that of trees in MQ.
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Differences in the Response of Radial Growth and Intrinsic Water Use Efficiency of Robinia pseudoacacia to Climatic Factors in Minquan of He'nan Province and Baishui of Shaanxi Province

    Corresponding author: SUN Shou-jia, ssj1011@163.com
  • Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China, Key Laboratory of Tree Breeding and Cultivation of National Forestry and Grasland Administration,Beijing 100091, China
  • 2. Co-Inovation for Sustainable Forestry in Southern China,Nanjing 210037,Jiangsu,China

Abstract:  Objective To analyze the response of radial growth and intrinsic water use efficiency (WUEi) of Robinia pseudoacacia to climate factors at different locations, and to determine the dominant factors affecting the growth and water use mechanism, so as to provide reference for the management of R. pseudoacacia plantations in China under climate change. Method The ring width chronologies were established in Minquan (MQ) of He'nan Province and Baishui (BS) of Shaanxi Province. The stable carbon isotopic composition (δ13C) of tree ring was measured to calculate the WUEi. The differences in the response of R. pseudoacacia to climatic variation were analyzed with meteorological data. Result The plantations at the two locations were in similar age. The tree-ring width at BS presented a trend of initially increasing and thereafter decreasing with the increase of tree age, whereas at MQ, the tree-ring width showed a linear decreasing trend with tree age increase. The trends of basal area increment (BAI) of R. pseudoacacia at the two locations were similar, presenting a trend of initially increasing and thereafter decreasing with the increase of tree age. The δ13C value and WUEi of the trees in MQ were lower than those of BS. The Pearson correlation results showed that on a monthly scale, the STD index of R. pseudoacacia in the two locations was mainly positively correlated with the summer precipitation and drought index (SPEI) (P < 0.05), and the R. pseudoacacia in BS was significantly negatively correlated with the average precipitation and SPEI in November of the previous year (P < 0.05). The WUEi of trees in MQ was significantly positively correlated with the average temperature and maximum temperature in March and August (P < 0.05), while that of trees in BS was significantly positively correlated with the average temperature, maximum temperature and minimum temperature from March to April of the current year, and June to July of the previous and current year (P < 0.05). The path analysis model showed that on the annual scale, the STD index of R. pseudoacacia in BS had a significant positive effect on the average precipitation and average temperature (P < 0.05), while the R. pseudoacacia in MQ had no significant response to climate factors. The annual average temperature had significantly positive effect on WUEi of trees at both the locations (P < 0.05). Conclusion The average precipitation is the dominant factor influencing the radial growth of R. pseudoacacia at both the locations, and the sensitivity of growth of trees in BS is higher than that of trees in MQ. The average temperature is the dominant factor influencing WUEi at the two locations, and the WUEi of trees in BS is more sensitive to the temperature than that of trees in MQ.

  • IPCC报告显示,在2030—2052年,全球平均气温将比工业革命前提高1.5℃,气候变暖引发的干旱、高温等极端气候事件将对森林生态系统产生巨大影响。于健等[1]与赵学鹏等[2]研究发现,气候持续变暖对长白山树木径向生长及地理分布范围产生较大影响。理清树木生长对气候变化的响应机制,有利于制定合理的森林经营对策。树轮包含了树木生命周期中的气候信息,是分析气候变化的重要材料;然而,随着树轮-气候响应研究的深入,国内外学者对美国[3]、匈牙利[4]和新疆天山[5]等地区不同树种生长研究发现,轮宽对气候因子敏感性降低,利用其对气候进行重建会出现偏差,而树轮中的稳定碳同位素(δ13C)组成可以准确反映大气的13C/12C变化,对气候因子响应比轮宽更敏感[6]。将轮宽和稳定碳同位素综合分析有助于解释树木生长和长期水碳平衡与气候变化的关系,国内外学者依据树轮中的δ13C来推导年际水分利用效率,研究了瑞士石松(Pinus cembra L.)[7]和川西云杉(Picea likiangensis var. balfouriana (Rehd. et Wils.) Hillier ex Slsvin)[8]的水分利用效率对气候的响应,但同一树种对不同地点气象因子的响应可能不同。为了更好地理解植物对气候变化的生理响应过程,需要进一步加强对同一树种内在水分利用效率(WUEi)空间变异及关键影响因子响应的研究。

    刺槐(Robinia pseudoacacia L.)为豆科、刺槐属植物,其根系浅而发达,适应性强,为我国水土保持和植被恢复的先锋树种,但受不同地点环境条件的影响,导致其生长差别较大,适应环境的刺槐生长较好,反之,则出现枯梢和退化等现象。先前研究发现,黄土高原刺槐径向生长与年均温度[9]和帕默尔干旱指数(PDSI)[10]显著正相关,但主要分析了刺槐生长与气候的关系,而对刺槐水碳利用与气候因子的关系认识不足。刺槐对环境的响应是一个长期过程,需在水碳方面保持相对平衡,WUEi是碳同化速率与气孔导度的比值,将水碳耦合在一起,能够解释树木在年际尺度上对气候变化的生理响应机制[11]。因此,本研究以河南省民权县与陕西省白水县两地林龄相近的刺槐林为研究对象,通过测定轮宽与δ13C,计算胸高断面积增量(BAI)和WUEi,回溯性分析不同地点刺槐径向生长和水分利用对气候因子响应的差异,确定影响刺槐生长和水分利用效率的主导气候因子,理清不同地点刺槐水碳利用对气候因子响应的差异,为今后气候变化背景下刺槐人工林的树种更新、结构优化和营林管理等提供参考。

    • 民权县(114°49′~115°27′ E,34°32′~34°52′ N,海拔90 m)位于河南省商丘市,暖温带大陆性带季风气候,四季分明,夏季雨热同期,年均降水量约679 mm,年均气温约14℃,年活动积温约5 192.6℃,年均日照时数约2 365.5 h。白水县(109°16′~109°45′ E,35°4′~35°27′ N,海拔1 210 m)位于陕西省渭南市,属暖温带半湿润半干旱季风气候,四季分明,光照条件好,年均降水量约577.8 mm,但分布不均匀,年均气温约11.4℃,年活动积温约3 546.4℃,年均日照时数约1 851.9 h。

    2.   研究方法
    • 以国际树木年轮数据库(ITRDB)为采样准则[12],于2020年6月在民权县国营民权林场和白水县新卓国有林场分别随机设置6块20 m × 20 m样方,测定刺槐胸径、树高、郁闭度等指标(表1),民权与白水的刺槐林龄相近,密度相差约10%,且民权刺槐树高与胸径均大于白水。使用生长锥在两地随机选取生长状况良好的100株刺槐钻取树芯,每株沿东西、南北方向各取1根,待样芯自然晾干后使用不同目数的砂纸进行打磨,直至样芯年轮清晰可见。

      样地
      Sample
      plots
      经度(E)
      Longitude
      纬度(N)
      Latitude
      海拔/m
      Altitude
      样树/样芯
      Tree/Cores
      时间
      Time
      span
      树龄/a
      Stand
      age
      平均树高/m
      Average
      height
      平均胸径/cm
      Average
      DBH
      郁闭度/%
      Canopy
      density
      密度 / (株·hm−2)
      Density
      民权MQ115°4′48″34°43′54″9077/1541981—20183817.2±1.235.95±1.10.64±0.2896±66
      白水BS109°22′3″35°16′56″1 21080/1601979—20184014.6±1.528.65±1.30.73±0.1983±41

      Table 1.  Statistical description of plots.

    • 使用Lintab 6年轮分析仪(Rinntech公司,德国)与TASP-Win软件测定样品轮宽并进行交叉定年,精确至0.01 mm;使用COFECHA、ARSTAN程序构建刺槐年表[13],最终民权与白水两个样地分别选用154、160根样芯制作年表。经对比发现,剔除生长趋势及非气候信息的干扰后,标准化年表(STD)中保留较多的低频气候信息,因此,本文选用标准化年表指数对刺槐径向生长进行分析。胸高断面积增量(BAI,cm2)能较好反映树木生长量大小,用轮宽数据计算:

      式(1)中:R为树木半径/cm,n为年轮形成年份。

    • 已有研究证实,选取4棵树的4根样芯测定δ13C,结果基本可代表研究区δ13C的绝对含量和变化趋势[14]。因此,从两地各选取4根年轮清晰的样品逐年剥离,进行称量、烘干、粉碎及过筛等步骤后放入TOC(Elementar Analysensysteme,德国)内充分燃烧,利用气体混合仪(Li-6000,中国)及LGR CO2同位素测定仪(LGR-912,美国)测量δ13C值,每30样品插入一个标准样进行校准,测定精度0.1‰,δ13C值采用维也纳白垩系皮狄组地层内美洲拟箭石(VPDB)标准,计算公式如下[15]

      式(2)中:RsampleRstandard为样品与标准物13C /12C的摩尔比率。

    • 为避免树轮δ13C记录气候信息受工业革命影响,依据McCarrol与NOAA的方法对其进行校正[16],树轮中稳定碳同位素辨别值(Δ13C)可由Farquhar[17]等公式计算:

      式(3)中:δ13Catmδ13Ctree分别为大气δ13C值和树轮中δ13C值;对C3植物,Δ13C与胞间CO2浓度(Ca)和大气CO2浓度(Ci)线性关系有关[18]WUEi可通过Δ13C与Ca值之间的关系计算获得[19]

      式(4)中:数值1.6为水蒸汽和CO2在空气中扩散比率,a = 4.4‰,b = 27‰,分别表示CO2扩散及羧化过程的同位素分馏系数。

    • 气象数据来自国家气象局,民权与白水气象数据分别采用离采样点较近的商丘气象站(34°27′ N,115°40′ E,海拔50.1 m)和洛川气象站(35°49′ N,109°30′ E,海拔1 159.8 m),干旱指数(SPEI)使用软件SPEI计算[20]。本文使用SPSS完成Pearson相关分析,R语言软件绘制Pearson相关关系图,AMOS.22(IBM,美国)建立结构方程模型。

    3.   结果与分析
    • 图1表明:1979—2018年,民权县年降水量高于白水县,且呈递增趋势,两地年最高降水量均出现在2003年,均超过900 mm。两地年均温度呈上升趋势,白水县整体低于民权约4℃左右。民权县相对湿度呈下降趋势,白水县低于民权约10%左右且趋于稳定。民权县干旱指数呈升高趋势,干旱情况在逐渐缓解,白水县则相对稳定。月尺度上,两地月最高降水量、最高气温均出现在7月,白水县月均降水、月均气温及月均相对湿度均低于民权县,在夏季的差异尤为明显。

      Figure 1.  Variation in precipitation, temperature, relative humidity and standardized precipitation evapotranspiration index (SPEI) during the study period at MQ and BS at annual and monthly timescale.

    • 图2显示:民权县刺槐标准化年表(STD)指数前期与后期波动较大,在1984年出现峰值,1993—2001年处于较低水平,2000年至2004年呈上升趋势,2004后逐渐下降。白水县STD指数趋势整体波动较小,介于0.8~1.2。

      Figure 2.  STD index of Robinia pseudoacacia at MQ and BS sites

    • 图3表明:两地轮宽变化趋势差异较大,民权县刺槐年际轮宽变化呈明显下降趋势,1981—2018下降约75.2%,白水县轮宽年际变化呈“升-降”趋势,1993年出现峰值。两地BAI随年份增加的变化曲线均呈极显著二次曲线关系(P < 0.01),后期均出现下降趋势,民权刺槐BAI自2008年开始下降,早于白水县约6 a,但整体BAI下降趋势不明显。

      Figure 3.  Differences in tree-ring width and BAI of Robinia pseudoacacia at MQ and BS sites

    • 图4表明:δ13C序列没有因幼龄效应表现显著上升趋势,民权县树轮δ13C值随时间呈极显著下降趋势(P < 0.01),白水县呈不显著的小幅度上升(P > 0.05),其δ13C值整体高于民权县。两地刺槐树轮WUEi均表现为随时间呈极显著上升趋势(P < 0.01),白水县的WUEi整体高于民权县,但白水县刺槐方程斜率为1.03,高于民权县刺槐的0.54,表明白水刺槐的WUEi升高较快。

      Figure 4.  Differences in of δ13C and WUEi of Robinia pseudoacacia at MQ and BS sites

    • 图5显示:民权县刺槐STD指数与当年8、9月平均降水及SPEI呈显著或极显著正相关(P < 0.05、P < 0.01),与当年7月的平均温度及7、9月的最高温度呈显著负相关(P < 0.05)。δ13C与上年10月平均降水、相对湿度、SPEI呈极显著正相关(P < 0.01),与上年7月平均温度、最低温度、最高温度均呈显著负相关(P < 0.05)。WUEi与上年10月平均降水、上年9、10月的最低温度、当年3月的平均温度和最高温度、当年3、8月的最高温度呈极显著正相关(P < 0.01),与当年8月的平均降水、平均温度呈显著正相关(P < 0.05)。总体来看,民权县刺槐径向生长、δ13C、WUEi受上年10月、当年3月和8月的气象因子影响较大,而δ13C、WUEi比径向生长更易受到气象因子的影响。

      Figure 5.  The STDindex, δ13C and WUEi related with monthly meteorological factors in MQ(left) and BS(right).

      白水县刺槐STD指数与当年7月的平均降水、相对湿度、SPEI呈显著或极显著正相关(P < 0.05,P < 0.01),而与上年11月的平均降水、相对湿度、SPEI呈显著或极显著负相关(P < 0.05,P < 0.01)。δ13C与当年2月平均温度、最低温度和最高温度呈显著或极显著正相关(P < 0.05,P < 0.01)。WUEi与上年及当年6、7月、当年3、4月平均温度、最低温度和最高温度呈显著或极显著正相关(P < 0.05,P < 0.01)。总体看,白水县刺槐径向生长受夏季降水和SPEI影响较大,WUEi受上年和当年生长季温度影响较大。与径向生长和δ13C相比,白水刺槐的WUEi更易受到气象因子特别是温度的影响。

    • 路径分析结果(图6)显示:在民权县,年尺度气象因子对刺槐STD指数无显著效应(p > 0.05);相对湿度对δ13C有显著正效应(P < 0.05),平均温度对δ13C有极显著负效应(P < 0.01),最高温度对δ13C有极显著正效应(P < 0.01);平均降水和最高温度对WUEi有显著正效应(P < 0.05),SPEI和平均温度对WUEi有极显著正效应(P < 0.01)。在白水县,平均降水与平均温度对刺槐STD指数有极显著正效应(P < 0.01),而最高温度与最低温度有极显著负效应(P < 0.01);SPEI对刺槐δ13C有显著正效应(P < 0.05),最低温度和最高温度对δ13C有极显著负效应(P < 0.01),平均温度对δ13C有极显著正效应(P < 0.01);相对湿度对WUEi有显著正效应(P < 0.05),平均温度对WUEi有极显著正效应(P < 0.01),最低温度对WUEi有极显著负效应(P < 0.01)。

      Figure 6.  Path analysis for STD index,δ13C and WUEi of Robinia pseudoacacia with meteorological factors

    4.   讨论
    • 受海拔影响,白水县温度明显低于民权县,降水和湿度也较低,SPEI变幅较小。两地刺槐径向生长也表现出明显差别,民权县刺槐年际轮宽变化呈明显下降趋势,白水县呈“升-降”趋势,表明民权县高温高湿的环境促进了刺槐前期径向生长,而较低的温度及干燥的气候则使白水刺槐前期径向生长缓慢。两地刺槐BAI与年龄均呈二次曲线变化,其原因在于刺槐生长后期随树龄增加生长速度逐渐下降。

      树木径向生长与当年气象因子及上年生长季后期和非生长季的气候因子密切相关。本研究中,两地刺槐STD指数与夏季降水和SPEI显著正相关,且民权刺槐与当年夏季最高温度呈负相关,白水刺槐与上年11月平均降水、SPEI显著负相关,这与李宗善等[21]观测到辽东栎对降水与温度的响应结果类似,可能是夏季高温导致刺槐部分气孔关闭,光合作用下降,限制刺槐径向生长,而充沛的降水利于土壤水源补充,促进了刺槐生长季后期及来年生长季初期的径向生长,秋季水分亏缺使植物根系活动受限,不利于有机物储存,在一定程度上影响来年生长量。

      在年尺度上,两地刺槐径向生长对气候响应的规律不明显。白水县年均降水、年均温度对刺槐STD指数为显著正效应,年最高温及年最低温为显著负效应,而民权刺槐STD指数与年尺度气候因子关系不显著,这与Aryal等[22]研究不同海拔落叶松径向生长的结果一致,可能是刺槐对温度较敏感,高温与低温环境均不利于其生长,白水县海拔较高,温度与降水成为限制刺槐生长关键因子。民权气候较适宜,年均降水充沛、年均温度稳定,刺槐生长受到年际间气候因子变化影响较小。

    • 由于对环境资源的利用策略不同,不同地点树木之间的δ13C与WUEi表现出明显差别。随着工业排放增加,大气CO2浓度持续升高和δ13C值降低影响了树木碳同化[23],导致WUEi升高,民权和白水刺槐WUEi随生长均呈极显著上升趋势印证了这种现象。

      民权刺槐δ13C与上年10月平均降水、SPEI和相对湿度呈正相关,与夏季高温呈负相关,可能是高温影响了树木的光合速率,限制了树木δ13C分馏。10月刺槐生理活动并未完全停止,此时优越的水分条件显著影响刺槐δ13C变化。而白水刺槐δ13C与2月温度呈正相关,这与朱娜等[24]对油松树轮的研究结果一致,但2月刺槐尚未发芽,可能是当温度回升至0℃以上,刺槐早春生理活动开始恢复,储存的碳水化合物中δ13C出现分馏现象。

      WUEi对多种气候因素非常敏感,尤其是干旱、温度和CO2浓度。在民权县,刺槐WUEi与3月温度正相关,而与SPEI负相关,这表明早春气温升高,促使刺槐生理活动恢复,但此时较干旱,使刺槐的WUEi提高;而夏季民权刺槐WUEi与降水和温度显著正相关,这与Tian等[25]观测到西南林区水分利用效率与降水呈负相关的结果不同,可能是当水分充足时,温度升高使光合速率增加幅度超过了气孔导度,进而导致WUEi上升。白水刺槐WUEi与生长季的温度显著正相关,可能是由于生长季期间温度升高导致树木光合作用加强,从而提高了WUEi

      在年尺度上,年均温度均对两地刺槐WUEi存在显著正效应,表明温度是影响两地刺槐WUEi的关键因子。此外,民权刺槐WUEi与年SPEI、年均降水也存在显著正效应,这与路伟伟等[26]研究油松水分利用效率结果一致,可能是温度与降水同时对树木WUEi变化产生作用,但水分对树木WUEi的影响小于温度的作用,导致刺槐WUEi对温度更敏感。

    5.   结论
    • 民权刺槐的径向生长在前期较快,生长量明显高于白水刺槐,δ13C和WUEi则均低于白水刺槐,主要与生长地点气候条件不同有关。两地刺槐径向生长对气候因子响应差异较大,平均降水是主要的主导因子,且白水刺槐生长对平均降水、平均温度等气候因子的敏感性高于民权。两地刺槐WUEi对气候因子响应基本一致,但存在部分差别,平均温度为主导因子,民权刺槐WUEi对平均降水等水分条件依赖性高于白水,白水刺槐WUEi较民权刺槐对温度变化更敏感。气候变化尤其是温度升高,将对白水县刺槐水分利用产生较大影响,因此,在黄土高原刺槐造林时需要充分考虑温度和水分条件,保持合理的结构和密度。

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