九种维管植物水力性状的演化趋势

维管植物从蕨类植物、裸子植物到被子植物的演化过程中, 生理结构和功能都被认为更趋向于适应干旱的环境。但是关于3类植物是否提升了水分传导和水分利用效率的研究目前多基于叶脉和气孔的形态结构推断, 而对水分传导速率的直接测量则集中于被子植物内部。因此, 同时测定3类植物叶片和枝条尺度的水力性状, 可以研究维管植物水力性状的演化趋势和协同演化关系。该研究测定了中国科学院华南植物园内的蕨类植物(芒萁(Dicranopteris pedata)、华南毛蕨(Cyclosorus parasiticus)、乌毛蕨(Blechnum orientale)), 裸子植物(罗汉松(Podocarpus macrophyllus)、竹柏(Podocarpus nagi)、落羽杉(Taxodium distichum))和被子植物(海南木莲(Manglietia fordiana var. hainanensis)、东京油楠(Sindora tonkinensis)、羊蹄甲(Bauhinia purpurea))共9种植物的水力结构与功能的相关性状。发现9种植物从原始到更演化物种的枝条比导水率(K_S)、叶片比导水率(K_L)和叶片水力导度(K_leaf)依次升高; 叶片蒸腾速率(E)和潜在水分利用效率(WUE_i)升高趋势不显著; 气孔面积指数(SPI)和木材密度(WD)在3个类群间无明显变化趋势。水力功能性状在枝条(K_S)和叶片(K_L、K_leaf和E)尺度显著相关, 但和两个结构性状并无显著相关性。对显著相关的性状进行系统发育独立差分析发现相关性依然存在, 表明枝条导水和叶片导水、叶片失水的协同性独立于系统发育而存在。该文以9种维管植物为例, 发现演化过程中水分传导相关的功能性状有显著提升, 且导水和失水的性状存在着协同演化关系。上述维管植物水力性状演化趋势的结论需要对更多物种、更精细的水力结构性状的进行测定验证。     

南亚热带常绿阔叶林4个树种对增温的生理生态适应能力比较

以红枝蒲桃(Syzygium rehderianum)、海南红豆(Ormosia pinnata)、红锥(Castanopsis hystrix)和木荷(Schima superba) 4种南亚热带常绿阔叶林典型树种为研究对象, 采用红外-箱式增温的方法, 研究4个树种叶片气孔性状(表征气孔调节能力)、叶片解剖结构(表征叶片组织调节能力)和光合特征(表征养分维持能力)对增温的响应情况, 比较不同树种在增温背景下的生理生态适应能力, 为预测该地区森林植物在全球变暖情形下的生长变化趋势提供理论依据。结果表明: 增温后, 红枝蒲桃叶片海绵组织厚度减小, 且光合氮利用效率(PNUE)和光合磷利用效率(PPUE)降低; 海南红豆气孔导度增大、气孔密度减小以及叶片厚度和栅栏组织厚度减小, 同时光合速率、PNUE和PPUE升高; 红锥气孔大小缩小, 但光合速率不变; 木荷气孔增大而密度减小, 栅栏组织厚度减小, 光合速率、PNUE和PPUE降低。综上所述, 红枝蒲桃、海南红豆和木荷能够通过降低叶片厚度来适应高温环境, 不同物种的气孔调节、养分维持、光合速率和光合养分利用效率对增温的响应存在差异。增温有利于固氮植物海南红豆的生长, 但不利于传统优势树种木荷和红枝蒲桃的生长。因此, 在未来气候变暖的情况下, 固氮植物海南红豆由于具有较强的适应能力, 在南亚热带常绿阔叶林中可能会取代木荷和红枝蒲桃等成为新的优势树种。     

叶片水力性状研究进展

叶片水力性状表征了叶片为适应外在环境而形成的水分传输方面的生存策略。叶片水力性状会限制整个植株的水分传输,并影响植物的气体交换及其对干旱的响应,因此关于叶片水力性状的研究已成为植物水分关系领域的研究热点之一。本文概括了叶片水力性状的基本指标(包括叶片整体水力导度(Kleaf)、叶片木质部水力导度(Kxylem)、叶片木质部外水力导度(Kout-xylem)等)和叶片水力导度的5种主要测量方法;总结了叶脉网络结构和环境因素对叶片水力性状的影响、叶片水力性状与叶片功能指标(气孔导度、叶片水势、叶片最大光合速率)的匹配与权衡关系,以及叶片水力性状与植物抗旱性关系的最新研究进展;对今后叶片水力性状的研究提出了两点建议:1)将叶片水力性状与气体交换和叶解剖结构等相结合,构建叶片碳-水耦合模型,揭示叶片应对外界环境变化而采取的生态策略,以及植物的水-碳投资机理;2)开展植株各部分(根-茎-叶)间水分传输的交互作用研究,筛选出水力系统高效安全的物种。     

陕北沙地高龄小叶杨光合速率下降的水力限制

黄土高原地区“小老树”现象多出现在成年树,幼树相对较少.为探讨树龄影响“小老树”形成的机制,以该地区“小老树”发生面积最大的树种小叶杨为例,研究了3个不同树龄(低龄:13～15 a;中龄:31～34 a;高龄:49～54 a)树木的生长、光合、水力学特性.结果表明: 随树龄增加,小叶杨枯稍长度显著增加,叶片光合速率、气孔导度和蒸腾速率显著下降,整株水力导度也显著下降,不同测定时间的光合速率、气孔导度与整株水力导度呈显著正相关,表明树龄增加引起的光合速率下降可能与整株水力导度下降有关.与中、低龄相比,高龄小叶杨枝干和叶片抵抗空穴化的能力(P₅₀)更强,但通过脆弱性曲线估算的不同树龄正午时的枝干栓塞程度和叶片水力导度无显著差异,表明高龄小叶杨土-根系统水流阻力的增加可能是导致其整株水力导度降低的重要原因.     

八个树种叶水力性状对水分条件的响应及其驱动因素

树木叶片的水力效率和安全性会对水分条件的改变做出一定的响应, 进而影响树木的生长和分布, 然而叶导水率(K_leaf)和叶水力脆弱性(P₅₀)对不同水分条件的响应模式及其影响因素尚不清楚。该研究选取了晋西北关帝山和黑茶山两种水分条件下的8种树种, 测量其水力性状、叶片导管和形态性状, 比较两地不同树种的K_leaf和P₅₀的变化, 分析叶片水力效率和安全性之间的权衡关系, 并探讨叶片水力性状在不同树种及水分条件下的响应模式及其驱动因素。结果表明: 对同一树种而言, 湿润的关帝山叶最大导水率(K_max)和P₅₀均高于干旱的黑茶山; 对同一地区而言, 从在高水分条件下生长的树种到在易干旱环境生长的树种, K_max和P₅₀均逐渐下降。K_max、P₅₀、膨压丧失点水势(TLP)之间均存在显著相关关系。两地叶片P₅₀与导管密度、导管塌陷预测值((t/b)³)、叶片厚度、比叶质量显著正相关, 与导管直径、叶面积显著负相关, 不同树种的K_leaf和P₅₀与叶导管性状的关系大于叶形态性状。同一树种的关帝山到黑茶山P₅₀变化量(δP₅₀)与比叶质量和叶干物质含量在两地的变化量显著正相关, 同一树种δP₅₀与叶形态性状变化量的关系大于与叶导管性状的。以上结果表明: 随着水分条件变差, 叶片水力效率降低, 水力安全性提高, 不同树种叶片水力效率与安全性之间存在一定的权衡关系, 不同树种叶水力性状的差别受叶导管性状影响的程度大于受叶形态性状的影响, 同一树种叶水力安全性对水分条件变化的响应主要依靠叶形态性状的驱动, 树木在提高自身叶水力安全的同时增加了叶构建的碳投资。     

罗汉松科3种植物茎和根木质部水分运输、解剖结构与机械强度之间的关系

水力失效是植物干旱死亡的主要机制。量化分析水力性状的种间和器官间差异是预测树木在气候变化下的响应甚至生存能力的基础。该研究对比分析了罗汉松科3种植物器官(茎和根)水平上水力功能性状的差异, 并探讨其与解剖结构和机械强度之间的关系。在湿生同质园内选择罗汉松科3种植物, 测定了茎和根木质部水力功能性状(最大比导率(K_s)和栓塞抗性(P₅₀))、解剖结构性状(管胞直径(D_t)、水力直径(D_h)、管胞密度(N_t)、管胞壁厚(T_w)、纹孔膜直径(D_p)和纹孔密度(N_p))和机械强度(木材密度(WD)和管胞厚度跨度比((t/b)²))。结果发现: (1)罗汉松科3种植物茎木质部不存在效率-安全权衡, 而根木质部存在权衡。(2)茎K_s与D_p显著正相关, 与(t/b)²和WD无关; 茎P₅₀与D_p极显著负相关, 与(t/b)²和WD无关。(3)根K_s与D_h显著正相关, 与T_w和(t/b)²极显著负相关; 根P₅₀与T_w、(t/b)²和WD均极显著正相关。在罗汉松科植物中, 根木质部性状与输水效率和栓塞抗性的密切关系是解释其存在效率-安全权衡的基础, 而茎木质部的过度建造是茎不存在效率-安全权衡的原因, 木质部的过度建造仍需要更多的实验证据。     

陕北沙地小叶杨“小老树”的水力适应性

以黄土高原"小老树"发生面积最大的树种-小叶杨为例,研究了不同水分生境下(水分相对好的沟道和干旱的梁坡片沙地,分别标记为生境A和生境B)小叶杨的生长、光合、水力学特性等,试图探讨小叶杨"小老树"对干旱生境的适应机制。结果表明:生境B小叶杨树高、地径、1 m树高处直径明显小于生境A,同时其主茎顶端枯枝长度大于生境A;生境B小叶杨叶净光合速率和气孔导度明显低于生境A。两种生境下小叶杨黎明前和正午叶水势无显著差异,生境B小叶杨正午时小枝枝干的比导水率明显低于生境A,但两种生境的比叶导水率则无显著差异,生境B小叶杨的Huber值明显大于生境A。生境B小叶杨枝干的P50(导水率损失50%时所对应的木质部水势)比生境A低约0.76 MPa左右,其气孔关闭的水势比生境A晚0.2 MPa左右,生境B小叶杨水分传输安全距离明显大于生境A。表明干旱生境下小叶杨高Huber值和低气孔导度有助于其叶水分关系维持相对稳定,低光合速率和维持大的水分传输安全距离所需的木质部碳投资增加是小叶杨形成"小老树"的重要原因。     

Changes in hydraulic traits of nine vascular plants from different evolutionary lineages

维管植物从蕨类植物、裸子植物到被子植物的演化过程中, 生理结构和功能都被认为更趋向于适应干旱的环境。但是关于3类植物是否提升了水分传导和水分利用效率的研究目前多基于叶脉和气孔的形态结构推断, 而对水分传导速率的直接测量则集中于被子植物内部。因此, 同时测定3类植物叶片和枝条尺度的水力性状, 可以研究维管植物水力性状的演化趋势和协同演化关系。该研究测定了中国科学院华南植物园内的蕨类植物(芒萁(Dicranopteris pedata)、华南毛蕨(Cyclosorus parasiticus)、乌毛蕨(Blechnum orientale)), 裸子植物(罗汉松(Podocarpus macrophyllus)、竹柏(Podocarpus nagi)、落羽杉(Taxodium distichum))和被子植物(海南木莲(Manglietia fordiana var. hainanensis)、东京油楠(Sindora tonkinensis)、羊蹄甲(Bauhinia purpurea))共9种植物的水力结构与功能的相关性状。发现9种植物从原始到更演化物种的枝条比导水率(K_S)、叶片比导水率(K_L)和叶片水力导度(K_leaf)依次升高; 叶片蒸腾速率(E)和潜在水分利用效率(WUE_i)升高趋势不显著; 气孔面积指数(SPI)和木材密度(WD)在3个类群间无明显变化趋势。水力功能性状在枝条(K_S)和叶片(K_L、K_leaf和E)尺度显著相关, 但和两个结构性状并无显著相关性。对显著相关的性状进行系统发育独立差分析发现相关性依然存在, 表明枝条导水和叶片导水、叶片失水的协同性独立于系统发育而存在。该文以9种维管植物为例, 发现演化过程中水分传导相关的功能性状有显著提升, 且导水和失水的性状存在着协同演化关系。上述维管植物水力性状演化趋势的结论需要对更多物种、更精细的水力结构性状的进行测定验证。     

九种不同材性的温带树种叶水力性状及其权衡关系

不同材性树种的解剖、叶脉分布等结构性状差异会影响树木的水分运输效率和水分利用策略, 进而限制树木的生存、生长和分布。然而, 材性对叶导水率、水力脆弱性及其潜在的权衡关系的影响尚不清楚。该研究选择东北温带森林中不同材性的9种树种(散孔材: 山杨(Populus davidiana)、紫椴(Tilia amurensis)、白桦(Betula platyphylla); 环孔材: 蒙古栎(Quercus mongolica)、水曲柳(Fraxinus mandshurica)、胡桃楸(Juglans mandshurica); 无孔材: 红皮云杉(Picea koraiensis)、樟子松(Pinus sylvestris var. mongolica)、红松(Pinus koraiensis), 测量其基于叶面积和叶质量的叶导水率(K_area和K_mass)、水力脆弱性(P₅₀)、膨压丧失点水势(TLP)及叶结构性状, 以比较不同材性树种叶水力性状的差异, 并探索叶水力效率与安全的权衡关系。结果表明: 3种材性树种的K_area、K_mass和P₅₀均差异显著(p < 0.05)。无孔材树种的K_area和K_mass最低, 而散孔材和环孔材树种差异不显著; 环孔材树种P₅₀最高, 而散孔材和无孔材树种差异不显著。K_area和K_mass均与P₅₀显著负相关(p < 0.05), 但散孔材、环孔材和无孔材树种的相关关系分别呈线性、幂函数和指数函数关系。这表明叶水力效率与安全之间存在一定的权衡关系, 但该关系受树木材性的影响。K_mass与TLP显著负相关(p < 0.01), 其中散孔材和环孔材树种呈线性负相关, 无孔材树种呈负指数函数关系; P₅₀随TLP的增加而增加, 这表明树木在面临水分胁迫时, 其质外体和共质体抗旱阻力共同协调保护叶片活细胞, 防止其水分状况到达临界阈值。K_mass与叶干物质含量、叶密度、比叶重均显著负相关, 而P₅₀与之显著正相关(p < 0.01, P₅₀与比叶重的关系除外), 表明树木叶水力特性的变化受相同叶结构特性驱动, 树木增加对水力失调的容忍需要在叶水力系统构建上增加碳投资。     

干旱胁迫下毛白杨和元宝槭的水力学调控

毛白杨(Populus tomentosa)和元宝槭(Acer truncatum)是华北平原人工林的主要树种, 研究两者水力结构和干旱-复水过程中茎非结构性碳水化合物(NSC)含量动态, 可揭示其水力学调控策略, 为全球气候变化背景下华北人工林水分平衡的科学管理提供理论依据。该研究以相同生境下分布的毛白杨和元宝槭幼树为研究材料, 测量两者的茎抗栓塞能力与水力安全阈、水力面积、叶膨压损失点等水力结构参数; 开展干旱-复水实验, 测定茎NSC含量动态以及干旱胁迫解除后复水阶段的木质部栓塞修复能力。结果表明: 毛白杨导水率损失50%对应的水势(-1.289 MPa)高于元宝槭(-2.894 MPa), 且膨压损失点时的渗透势低, 水力安全阈小, 木材密度小, 气孔调节偏向于变水行为, 表现为易栓塞的低水势忍耐脱水耐旱特性, 水分调节对策趋于冒险; 元宝槭则倾向于不易栓塞的高水势延迟脱水耐旱特性, 水分调节对策趋于保守。在干旱-复水实验中, 毛白杨可溶性糖、淀粉和茎NSC含量先减后增, 元宝槭则先增后减; 并且毛白杨表现出比元宝槭更高的栓塞修复能力, 这与植物体内茎NSC含量变化差异具有一定联系。毛白杨较高的栓塞修复能力也为其易栓塞的低水势忍耐脱水耐旱特性及冒险的水分调节对策提供水力安全保障。两树种在水力学调控上表现出的较大差异可能与其生活史特性相关。     

Scots pine plantations growth adaptation to climate warming in locations at the southernmost distribution limit of the species

Under the current climate change conjuncture, understanding the forest plantations capacity of acclimation to warming and increased drought stress is crucial for forest managers. To get some understanding of their adaptability, plantations of similar provenance but located in climatically contrasting sites can be compared. Here we study the growth dynamics and their relationship with climate and drought in two Scots pine (Pinus sylvestris L.) plantations located in the center (Sierra de Guadarrama, wetter site) and south (Sierra Nevada, drier site) of Spain, the latter situated at the southernmost distribution limit of the species. Our objectives are to quantify the trends in radial growth of these plantations, to quantify the influence of climate on growth, and to project the plantations growth as a function of forecasted climate. Results reveal that the plantations from the drier site show lower, and less responsive to climate, growth and greater resilience than those from the wetter site. Furthermore, if the current climate-growth relationships continue in the future, these plantations would maintain the current limited growth rate during the 21st century. On the contrary, plantations from the wetter site show higher growth rate and more resistance to drought, and they are projected to increase growth under the warmer conditions forecasted for the 21st century. Our study shows that plantations in drier sites may have a great capacity to acclimate to local climate conditions and would not be negatively impacted by the projected climate warming.     

不同林龄、树种落叶松人工林径向生长与气候变化的关系

研究人工林径向生长与气候变化的关系对全球气候变暖背景下人工林合理经营有着重要的意义。该文对在辽东山区广泛栽培的黄花落叶松(Larix olgensis)和日本落叶松(Larix kaempferi)人工林, 运用树木年轮气候学方法建立了辽宁草河口和湾甸子林场落叶松人工林年表, 分析了落叶松径向生长对气候变化的响应以及气候条件、树种、立地条件和林分因子(林龄、密度、蓄积量等)的相对影响程度。结果发现在影响年轮-气候关系的因素中, 气象因子的潜在蒸发散(PET)的影响力最大; 林龄、密度和蓄积量同时也具有重要的影响作用。中龄落叶松人工林径向生长主要与气温呈正相关关系, 成熟落叶松人工林径向生长主要与气温呈负相关关系; 而其他因素, 如树种、立地条件等的影响作用不大。这表明在气候变暖背景下随着林龄增加, 林分会逐渐受到气温升高导致的水分亏缺的限制, 导致明显的生长下降趋势, 因而气候变暖对成熟落叶松人工林威胁更为严重, 所以要注重对成熟林的优先保护, 同时可以预测, 随着东北地区今后气候进一步变暖, 可能将逐步影响到林龄更小的林分的生长, 因此需要进一步研究如何在落叶松人工林经营中采取科学的措施来更好地应对未来气候变化。     

黄土高原半湿润区刺槐树干液流对人工截留降雨输入及环境因子的响应

随着全球气候变化加剧, 局部地区温度上升和降水量改变将对区域植被的分布与生长产生重要影响。在黄土高原半湿润及半干旱地区植被恢复中, 刺槐(Robinia pseudoacacia)是大面积种植的人工林树种。为探究该树种蒸腾耗水特征对降水量改变及水分条件差异的响应, 于2015年4月起, 在地处黄土高原半湿润区的陕西省永寿县槐平林场, 于35年生刺槐人工林样地中布设了人工截留降雨试验, 减少了47.5%的降雨输入。处理当年生长季内, 截留降雨处理区0-100 cm土层的平均土壤含水量相对于对照区(23.76%)有明显降低(22.59%)。采用Granier热扩散探针对截留降雨处理区和对照区的样树树干液流动态进行连续监测, 并同步监测主要气象环境因子(太阳辐射、空气温度和湿度)和林地土壤含水量, 分析了截留降雨处理区与对照区树干液流通量密度动态特征及其对环境因子的响应。结果表明: 截留降雨输入处理降低了刺槐树干液流通量密度, 截留降雨处理期间典型天气的平均液流通量密度(1.64 mL·m ^-2·s ^-1)不仅低于同组样树在处理前一年同期的水平(2.42 mL·m ^-2·s ^-1), 而且远低于试验期间对照区样树的平均水平(3.38 mL·m ^-2·s ^-1); 同时, 截留降雨处理还降低了刺槐液流通量密度对气象因子变化的敏感性, 截留降雨处理区样树液流通量密度响应空气水汽压亏缺的拟合方程参数值与对照区样树差异显著。分析可知, 降水量水平不仅影响土壤水分状况, 而且影响刺槐对气象环境因子响应的敏感性, 降水量减少导致的土壤含水量整体降低会使得该区域刺槐蒸腾耗水量下降, 显示其对环境因子的适应性, 但最终会导致生产力的大幅度降低。     

Sap flow of Robinia pseudoacacia in response to rainfall exclusion treatment and environment factors in a sub-humid area in Loess Plateau

随着全球气候变化加剧, 局部地区温度上升和降水量改变将对区域植被的分布与生长产生重要影响。在黄土高原半湿润及半干旱地区植被恢复中, 刺槐(Robinia pseudoacacia)是大面积种植的人工林树种。为探究该树种蒸腾耗水特征对降水量改变及水分条件差异的响应, 于2015年4月起, 在地处黄土高原半湿润区的陕西省永寿县槐平林场, 于35年生刺槐人工林样地中布设了人工截留降雨试验, 减少了47.5%的降雨输入。处理当年生长季内, 截留降雨处理区0-100 cm土层的平均土壤含水量相对于对照区(23.76%)有明显降低(22.59%)。采用Granier热扩散探针对截留降雨处理区和对照区的样树树干液流动态进行连续监测, 并同步监测主要气象环境因子(太阳辐射、空气温度和湿度)和林地土壤含水量, 分析了截留降雨处理区与对照区树干液流通量密度动态特征及其对环境因子的响应。结果表明: 截留降雨输入处理降低了刺槐树干液流通量密度, 截留降雨处理期间典型天气的平均液流通量密度(1.64 mL·m ^-2·s ^-1)不仅低于同组样树在处理前一年同期的水平(2.42 mL·m ^-2·s ^-1), 而且远低于试验期间对照区样树的平均水平(3.38 mL·m ^-2·s ^-1); 同时, 截留降雨处理还降低了刺槐液流通量密度对气象因子变化的敏感性, 截留降雨处理区样树液流通量密度响应空气水汽压亏缺的拟合方程参数值与对照区样树差异显著。分析可知, 降水量水平不仅影响土壤水分状况, 而且影响刺槐对气象环境因子响应的敏感性, 降水量减少导致的土壤含水量整体降低会使得该区域刺槐蒸腾耗水量下降, 显示其对环境因子的适应性, 但最终会导致生产力的大幅度降低。     

Importance of mangrove plantations for climate change mitigation in Bangladesh

Mangroves have been identified as blue carbon ecosystems that are natural carbon sinks. In Bangladesh, the establishment of mangrove plantations for coastal protection has occurred since the 1960s, but the plantations may also be a sustainable pathway to enhance carbon sequestration, which can help Bangladesh meet its greenhouse gas (GHG) emission reduction targets, contributing to climate change mitigation. As a part of its Nationally Determined Contribution (NDC) under the Paris Agreement 2016, Bangladesh is committed to limiting the GHG emissions through the expansion of mangrove plantations, but the level of carbon removal that could be achieved through the establishment of plantations has not yet been estimated. The mean ecosystem carbon stock of 5–42 years aged (average age: 25.5 years) mangrove plantations was 190.1 (±30.3) Mg C ha⁻¹, with ecosystem carbon stocks varying regionally. The biomass carbon stock was 60.3 (±5.6) Mg C ha⁻¹ and the soil carbon stock was 129.8 (±24.8) Mg C ha⁻¹ in the top 1 m of which 43.9 Mg C ha⁻¹ was added to the soil after plantation establishment. Plantations at age 5 to 42 years achieved 52% of the mean ecosystem carbon stock calculated for the reference site (Sundarbans natural mangroves). Since 1966, the 28,000 ha of established plantations to the east of the Sundarbans have accumulated approximately 76,607 Mg C year⁻¹ sequestration in biomass and 37,542 Mg C year⁻¹ sequestration in soils, totaling 114,149 Mg C year⁻¹. Continuation of the current plantation success rate would sequester an additional 664,850 Mg C by 2030, which is 4.4% of Bangladesh's 2030 GHG reduction target from all sectors described in its NDC, however, plantations for climate change mitigation would be most effective 20 years after establishment. Higher levels of investment in mangrove plantations and higher plantation establishment success could contribute up to 2,098,093 Mg C to blue carbon sequestration and climate change mitigation in Bangladesh by 2030.     

Natural climate solutions versus bioenergy: Can carbon benefits of natural succession compete with bioenergy from short rotation coppice?

Short rotation plantations are often considered as holding vast potentials for future global bioenergy supply. In contrast to raising biomass harvests in forests, purpose‐grown biomass does not interfere with forest carbon (C) stocks. Provided that agricultural land can be diverted from food and feed production without impairing food security, energy plantations on current agricultural land appear as a beneficial option in terms of renewable, climate‐friendly energy supply. However, instead of supporting energy plantations, land could also be devoted to natural succession. It then acts as a long‐term C sink which also results in C benefits. We here compare the sink strength of natural succession on arable land with the C saving effects of bioenergy from plantations. Using geographically explicit data on global cropland distribution among climate and ecological zones, regionally specific C accumulation rates are calculated with IPCC default methods and values. C savings from bioenergy are given for a range of displacement factors (DFs), acknowledging the varying efficiency of bioenergy routes and technologies in fossil fuel displacement. A uniform spatial pattern is assumed for succession and bioenergy plantations, and the considered timeframes range from 20 to 100 years. For many parameter settings—in particular, longer timeframes and high DFs—bioenergy yields higher cumulative C savings than natural succession. Still, if woody biomass displaces liquid transport fuels or natural gas‐based electricity generation, natural succession is competitive or even superior for timeframes of 20–50 years. This finding has strong implications with climate and environmental policies: Freeing land for natural succession is a worthwhile low‐cost natural climate solution that has many co‐benefits for biodiversity and other ecosystem services. A considerable risk, however, is C stock losses (i.e., emissions) due to disturbances or land conversion at a later time.     

Effects of climate change on net primary productivity in Larix olgensis plantations based on process modeling

Aims Climate change has significant effects on net primary productivity (NPP) in forests, but there is a large uncertainty in the direction and magnitude of the effects. Process-based models are important tools for understanding the responses of forests to climate change. The objective of the study is to simulate changes in NPP of Larix olgensis plantations under future climate scenarios using 3-PG model in order to guide the management of L. olgensis plantations in the context of global climate change.Methods Data were obtained for 30 permanent plots of L. olgensis plantations in Siping, Linjiang, Baishan, etc. of Jilin Province, and a process model, 3-PG model, was applied to simulate changes in NPP over a rotation period of 40 years under different climate scenarios. Parameter sensitivity was also determined. Important findings The locally parameterized 3-PG model well simulates the changes in NPP against the measured NPP data, with values between 272.79-844.80 g·m^-2·a^-1 and both mean relative error and relative root mean square error within 12%. The NPP in L. olgensis plantations would increase significantly with increases in atmospheric CO₂ concentration, temperature and precipitation collectively. However, an increase in temperature alone would lead to a decrease in NPP, but increases in precipitation and atmospheric CO₂ concentration would increase NPP; the positive effect of increasing precipitation appears to be weaker than the negative effect of increasing temperature. Sensitivity analysis shows that the model performance is sensitive to the optimum temperature, stand age at which specific leaf area equals to half of the sum of specific leaf area at age 0 (SLA₀) and that for mature leaves (SLA₁), and days of production loss due to frost.     

Sustainability potential for Ginkgo biloba L. plantations under climate change uncertainty: An ex-situ conservation perspective

G. biloba is native to China and one of the oldest living species. It has high economic value and has been used for medicinal, ornamental and other purposes. The current study sought to assess the potential sustainability of the plantations of the endangered species under climate change scenarios. The sustainability of the existing small wild population and plantations of the species worldwide were evaluated by assessing the changes in the climatic suitability of the areas to be used for the species plantations under different emission scenarios. A survey for the species distribution worldwide showed that it is currently planted in 29 botanic gardens. In Egypt only 31 trees exist in private and public botanic gardens. Propagation and germination experiments have been tested in 4 successive years to assess the effect of climate changes on germination requirements and phenology of the species. Propagation trials showed that seeds that were grown in soil media for 5 months under 25 °C attained high germination rate (>60%). Propagation trials in the nursery by stem cuttings gave promising results (100%) in 2015–2016. Using SDMs approach for assessing the change in the potential climatically suitable areas for the plantations and ex situ conservation of G. biloba under different climate change and emission scenarios, revealed that overall G. biloba is predicted to gain more climatically suitable areas under the four representative concentration pathway scenarios (RCP 2.6, 4.5, 6.0 and 8.5), however, a gain in the climatically suitable areas for the species is expected under the low and moderate emission scenarios and a decline is expected under the more warming scenarios. Also, a northwards shift is predicted in the climatic suitability for the plantations of the species. The projected latitudinal shift needs to be considered by mangers of G. biloba plantations. The provided predictions can guide the managers in developing short- and long-term plans for sustaining the plantations of the species under a precipitously changing climate.     

Tree-ring growth varies with climate and stand density in a red pine plantation forest in the Great Lakes region of North America

Red pine (Pinus resinosa Ait.) was widely planted across the Great Lakes region of North America in the early 20th century to restore tree cover to degraded forest and agricultural lands. In this study, a dendrochronological assessment of radial growth response to climate was conducted in an 82-year-old, previously thinned red pine plantation forest in southern Ontario, Canada. Climate-growth relationships were analyzed at multi-monthly and annual time scales using a 72-year residual growth chronology (1942–2013). Warmer temperatures and periodic drought during the current and previous growing seasons were associated with decreased growth, while higher precipitation during the early part of the current growing season was associated with increased growth. Moving interval correlation analysis of long-term trends indicated that climate-growth relations were temporally unstable due to thinning and variation in climate over the length of the chronology. The correlation between climate and growth was stronger when stand density was relatively high and diminished in the two decades following thinning. These results indicate that growth of red pine plantations near the species’ southern range limit may be much reduced if exposed to a warmer, drier future climate and that periodic thinning can help mitigate the impacts of future climate change on these plantations.