西双版纳楝径向生长和木质部发生季节动态及其对环境因子的响应

热带森林在全球碳循环过程中起着重要的作用,研究热带树木的生长动态及其对环境因子的响应,有助于预测全球变化下热带森林固碳能力的变化。目前对热带树木径向生长以及木质部发生季节动态的研究相对较少。利用微树芯和生长环法对西双版纳热带植物园内的落叶树种楝(Melia azedarach)2021年的年内径向生长和木质部发生季节动态进行监测,结合环境因子的监测,分析了楝的径向生长过程的驱动因子。结果表明：2021年楝的扩大细胞在3月1日(年积日(DOY):60.2±1.6)开始出现,细胞壁加厚在12月11日(DOY:345.4±3.1)结束,年生长量为7.76 mm,最大生长速率为0.039 mm/d。生长环监测显示,楝在3月18日(DOY:76.6±8.6)左右开始生长,10月13日(DOY:286.4±6.8)生长结束,年径向生长量为(6.25±2.35)mm,最大生长速率为(0.056±0.02)mm/d。楝的径向生长速率与降水(r=0.77,P<0.001)、平均温度(r=0.61,P<0.05)和最低温度(r=0.67,P<0.001)均呈显著正相关,与风速(r=-0....     

芦芽山林线白杄生长季径向生长动态

高山林线作为树木分布的高度上限, 是全球范围最重要的植被过渡带之一, 其树木生长显著受到外界极端环境条件的影响。利用点状树木径向变化记录仪于2009年5-9月, 对山西省芦芽山林线组成树种白杄(Picea meyeri)生长季内树木径向生长进行了持续的动态监测。结果表明: 白杄茎干日变化主要受到树木蒸腾作用日变化的影响, 茎干呈现出白天脱水收缩与夜间吸水膨胀的循环变化; 生长季白杄径向生长可划分为3个不同的生长时段: 1)茎干水分恢复时段, 2)茎干快速生长时段, 3)茎干脱水收缩时段。在茎干水分恢复时段, 白杄茎干径向累积变化主要受到土壤含水量变化的影响。土壤温度是茎干快速生长时段影响茎干径向生长的主导环境因子, 同时它也影响着白杄茎干径向生长的开始。在茎干脱水收缩时段, 土壤温度、土壤含水量是影响茎干径向累积变化的主要环境因子。白杄径向生长最大速度出现在6月末, 其主要受到光周期(即白昼长短)影响, 是对林线处极端环境的一种适应。     

长白山阔叶红松林3个常见树种径向生长的影响因素

为探究树木径向生长的影响因子,基于对长白山阔叶红松林25 hm²样地中3个常见树种红松、紫椴、蒙古栎连续5年的生长环监测数据,分析各树种的季节生长变化,比较树种间的生长速率差异,并分析初始径级、邻体树木竞争、土壤、地形因素等对不同树种径向生长的作用.结果表明: 3个树种径向生长的季节变化趋势一致,树木于5月末开始生长,7月是生长旺盛期,8月底生长开始减缓,于10月中下旬停止生长.3个树种的径向相对生长率存在显著差异,蒙古栎相对径向生长率显著高于红松和紫椴,该差异在小、中径级个体中表现更为显著.3个树种径向生长的主要影响因子不同,邻体树木的竞争显著抑制了红松和蒙古栎的径向生长,而紫椴的径向生长主要受初始径级、土壤和地形等因子的影响.     

Different Patterns of Changes in the Dry Season Diameter at Breast Height of Dominant and Evergreen Tree Species in a Mature Subtropical Forest in South China

Information on changes in diameter at breast height （DBH） is important for net primary production （NPP） estimates, timing of forest inventory, and forest management. In the present study, patterns of DBH change were measured under field conditions during the dry season for three dominant and native tree species in a monsoon evergreen broad-leaved forest in the Dinghushan Biosphere Reserve. For each tree species, different patterns of DBH change were observed. In the case of the fast-growing tree species Castanopsis chinensis Hance, large diurnal fluctuations occur, with a peak DBH in the early morning （around 05：00 h） that decreases to a minimum by about 14：00 h. Both Schima superba Gardn. et Chemp and Cryptocarya chinensis （Hance） Hemsh exhibited less diurnal swelling and shrinkage. Diurnal fluctuations for these species were observed on a few occasions over the period of observation. Graphical comparisons and statistical analysis of changes in DBH with meteorological variables indicate that for different trees, the different changes in DBH observed responded to different meteorological variables. Large stem changes were found to occur for Ca. chinensis trees that were associated with variations in solar radiation. However, both S. superba and Cr. chinensis were found to be less sensitive to solar radiation. Changes in the DBH of these two species were found to be controlled mainly by soil temperature and soil moisture. During the later dry season, with a lower soil temperature and soil moisture, all three tree species stopped growing and only negligible shrinkage, expansion, or fluctuation occurred, suggesting that the optimum time to measure tree growth in the Dinghushan Biosphere Reserve is the later dry season.     

The pulse of the tree is under genetic control: eucalyptus as a case study

The pulse of the tree (diurnal cycle of stem radius fluctuations) has been widely studied as a way of analyzing tree responses to the environment, including the phenotypic plasticity of tree–water relationships in particular. However, the genetic basis of this daily phenotype and its interplay with the environment remain largely unexplored. We characterized the genetic and environmental determinants of this response, by monitoring daily stem radius fluctuation (dSRF) on 210 trees from a Eucalyptus urophylla × E. grandis full‐sib family over 2 years. The dSRF signal was broken down into hydraulic capacitance, assessed as the daily amplitude of shrinkage (DA), and net growth, estimated as the change in maximum radius between two consecutive days (ΔR). The environmental determinants of these two traits were clearly different: DA was positively correlated with atmospheric variables relating to water demand, while ΔR was associated with soil water content. The heritability for these two traits ranged from low to moderate over time, revealing a time‐dependent or environment‐dependent complex genetic determinism. We identified 686 and 384 daily quantitative trait loci (QTL) representing 32 and 31 QTL regions for DA and ΔR, respectively. The identification of gene networks underlying the 27 major genomics regions for both traits generated additional hypotheses concerning the biological mechanisms involved in response to water demand and supply. This study highlights that environmentally induced changes in daily stem radius fluctuation are genetically controlled in trees and suggests that these daily responses integrated over time shape the genetic architecture of mature traits.     

Separating water‐potential induced swelling and shrinking from measured radial stem variations reveals a cambial growth and osmotic concentration signal

The quantification of cambial growth over short time periods has been hampered by problems to discern between growth and the swelling and shrinking of a tree stem. This paper presents a model, which separates cambial growth and reversible water‐potential induced diurnal changes from simultaneously measured whole stem and xylem radial variations, from field‐measured Scots pine trees in Finland. The modelled growth, which includes osmotic concentration changes, was compared with (direct) dendrometer measurements and microcore samples. In addition, the relationship of modelled growth and dendrometer measurements to environmental factors was analysed. The results showed that the water‐potential induced changes of tree radius were successfully separated from stem growth. Daily growth predicted by the model exhibited a high correlation with the modelled daily changes of osmotic concentration in phloem, and a temperature dependency in early summer. Late‐summer growth saw higher dependency on water availability and temperature. Evaluation of the model against dendrometer measurements showed that the latter masked a true environmental signal in stem growth due to water‐potential induced changes. The model provides better understanding of radial growth physiology and offers potential to examine growth dynamics and changes due to osmotic concentration, and how the environment affects growth.     

The negative effect of lianas on tree growth varies with tree species and season

Lianas reduce tree growth, reproduction, and survival in tropical forests. Liana competition can be particularly intense in isolated forest fragments, where liana densities are high, and thus, host tree infestation is common. Furthermore, lianas appear to grow particularly well during seasonal drought, when they may compete particularly intensely with trees. Few studies, however, have experimentally quantified the seasonal effects of liana competition on multiple tree species in tropical forests. We used a liana removal experiment in a forest fragment in southeastern Brazil to test whether the effects of lianas on tree growth vary with season and tree species identity. We conducted monthly diameter measurements using dendrometer bands on 88 individuals of five tree species for 24 months. We found that lianas had a stronger negative effect on some tree species during the wet season compared to the dry season. Furthermore, lianas significantly reduced the diameter growth of two tree species but had no effect on the other three tree species. The strong negative effect of lianas on some trees, particularly during the wet season, indicates that the effect of lianas on trees varies both seasonally and with tree species identity. Abstract in Portuguese is available with online material.     

热带喀斯特森林多花白头树木质部年内生长动态及其对环境因子的响应

多花白头树(Garuga floribunda var.gamblei)是西双版纳热带喀斯特森林中常见的落叶树种,容易受水分亏缺的影响。为探究热带喀斯特森林树木年内生长动态及其对环境因子的响应,该研究利用生长环和微树芯两种方法监测了多花白头树在2020—2021年的树干径向变化和木质部生长动态,并分析了树干径向变化和木质部生长与环境因子的相关性。微树芯法的监测表明,在2020年,多花白头树在3月底开始出现扩大细胞,9月底细胞壁加厚结束;在2021年,多花白头树在4月中旬开始出现扩大细胞,10月中旬细胞壁加厚结束。生长环的监测表明,2020年和2021年的径向生长开始时间均晚于扩大细胞出现时间,径向生长结束时间均早于细胞壁加厚结束时间。多花白头树在2020年和2021年的木质部生长持续时间大致相同,2020年的木质部生长量((2.87±1.46)mm)也与2021年((2.98±1.02)mm)几乎一致。多花白头树的月径向生长量、扩大细胞区域宽度和细胞壁加厚区域宽度均与降水呈显著正相关,这表明水分状况在多花白头树的木质部生长过程中发挥了重要作用;扩大细胞区域宽度还与日平均气温和日最低温显...     

小兴安岭红松日径向变化及其对气象因子的响应

利用带状树干径向变化记录仪监测了小兴安岭凉水国家级自然保护区原始阔叶红松林中的红松树干径向生长,分别用两种数据处理方法(日最大值法与周期循环法)分析了红松径向生长与气象因子的关系。结果表明:红松径向生长于5月中旬开始,在7月末趋于结束,最大径向生长速率出现在6月中旬。使用Gompertz生长模型能很好的拟合红松的径向生长,可以解释红松92%以上的径向变化。对于日最大值法,偏相关分析表明日径向变化与空气相对湿度、土壤温度和降雨量显著相关;对于周期循环法,第一阶段(收缩阶段)收缩量主要受到相对湿度、土壤温度和水汽压亏缺的影响。第二阶段(膨胀阶段)影响树干径向恢复的主要因子是降雨量和最高气温。第三阶段(增长阶段)对树干径向生长影响最显著的是最低气温和降雨量。应用多元线性模型分析显示,周期循环法能更加细化的分析日气象因子对红松径向生长的影响,能够更为真实地解释红松径向生长动态变化特点与规律,其中第二和第三阶段的降雨和最低气温对红松径向生长的影响最大。     

热带季节性湿润林苦楝(Melia azedarach)径向生长季节动态及其对环境因子的响应

气候变化导致的温度升高和降水格局改变可能会影响到树木的生长速率和季节物候。西双版纳热带季节性湿润林分布在石灰岩山中部,属于热带喀斯特生境。由于土层浅薄,土壤保水能力极差,植物生长更容易遭到受到季节性干旱气候的影响。为探究热带季节性湿润林的树木径向生长季节动态及其对环境因子的响应,利用高精度树木生长仪连续两年监测了云南西双版纳热带季节性湿润林中落叶树种苦楝（Melia azedarach）的树干径向变化,并与同步监测的环境因子进行相关分析。结果表明,苦楝径向生长开始、结束以及持续生长的时间在年际间存在差异。与2018年相比,2019年苦楝生长开始和结束的时间较晚,且年生长量较小,这可能是与2019年雨季开始较晚且在生长季早期经历了严重的高温干旱有关。苦楝的径向日生长量与日降水量和相对湿度呈正相关关系,与光合有效辐射、水汽压亏缺和风速呈负相关关系,表明了在苦楝的径向生长主要受水分条件限制。在干旱年份（2019年）,苦楝的日生长量与降水和相对湿度的相关性更强。研究结果有助于进一步了解热带喀斯特生境树木生长对气候变化的敏感性以及树木适应季节性干旱气候的策略。