Climate change, largely caused by elevated carbon dioxide (CO2) concentrations, is a driver of lasting disturbances that cause changes in forest ecosystem functioning. This study aimed to investigate how Japanese cypress (Chamaecyparis obtusa) and Japanese cedar (Cryptomeria japonica D. Don) plantations in the subtropical forests of China respond to disturbances in tree growth under climate change. In this study, 23 canopy gaps were selected from two species in the Lushan National Nature Reserve of Jiangxi Province, China. Increment cores were obtained from trees retained near the edges of gaps and within the forest. Tree-ring chronologies were established, and the basal area increment (BAI) was calculated. The growth averaging method was used to detect growth release and analyze two key parameters of tree radial growth: magnitude and time lag. Moving correlation analyses were used to assess the long-term relationship between tree growth and climate, and regression analyses were used to quantify the relationship between the BAI and atmospheric CO2 concentrations. Species characteristics, tree distance from the gap center, gap size, and elevation all influenced tree growth release which was greater for Japanese cedar than Japanese cypress, and decreased with increasing distance from the gap center. Diameter at breast height (DBH) and pre-release growth influenced the time lag in growth release. The time-lag effect was more significant with smaller DBH and pre-release growth and did not differ between the two species. The correlations among growth, temperature, and precipitation were altered by the microclimatic environment created by the gaps. The BAI of Japanese cypress and Japanese cedar responded quadratically with increasing CO2 concentration (Ca), and the BAI increased with rising Ca, peaking at 360–380 ppm, followed by a decreasing trend. Due to the effect of the disturbance, there was a BAI increase of approximately 400 ppm (2015) for trees at the gap edge. Growth characteristics were influenced by tree- and gap-level variables. Disturbance altered the link between tree growth and climate responses, increasing tree growth sensitivity to climatic influences, shifting the quadratic relationship between BAI and CO2 concentration, and providing growth potential to trees that crossed the CO2 tipping point.

Objective]This study aimed to theoretically support the scientific assessment of the carbohydrate-water coupling connection of Cryptomeria japonica.[Method]The water use efficiency（WUE） of Cryptomeria japonica was calculated using the tree-ring stable carbon isotope method in this study.Additionally,average temperatures （T）,precipitation （W）,average wind speeds （Ws）,solar radiation（Rs）,the drought index （SPEI,SPI,WI）,and other climate change-related indicators were used to analyze the WUE of Cryptomeria japonica and its adaptation to climate change.[Result]（1） From 1969 to 2018 the sequence of 13C values of Cryptomeria japonica tree rings in Lushan Mountain,Jiangxi Province of eastern China showed a downward trend;the variation range was -23.09‰ to -25.67‰,and the annua average was -24.55‰;the inter-annual value of Cryptomeria japonica WUE showed an upward trend;the variation range was 91.06 to 118.89μmol/mol,with an annual average of 102.37μmol/mol.（2） Correlation analysis revealed that the WUE of Cryptomeria japonica in Lushan Mountain was significantly correlated with the temperature in July,September to November of the previous year,February to June,and September to November of the current year,and significantly negatively correlated with the wind speed in July to December of the previous year and January to December of the current year.However,the solar radiation precipitation,SPEI,WI,and SPI of each month had no significant impact on the WUE of Cryptomeria japonica on Lushan Mountain.（3）The multiple regression model analysis showed that the WUE of Cryptomeria japonica on Lushan Mountain was mainly related to Ws 1 （wind speed in January of the curren year）,T 3 （average temperature in March of the current year）,T 9 （average temperature in September of the current year）,T -9 （average temperature in September of the previous year）,and Ws 12 （wind speed in December of the current year）.[Conclusion]T and Ws are the primary climatic variables affecting WUE of Cryptomeria japonica.The WUE of Cryptomeria japonica on Lushan Mountain is not significantly affected by W,Rs,or the drought indicators （SPI,SPEI and WI）.

The conversion of natural forests to planted forests has become a global trend, and the practice has wide-ranging effects on soil. This study aimed to explore the differences in soil water movement after the conversion of evergreen and deciduous broad-leaved mixed forests (natural forest, NF) to Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) plantations (CFP, 20–21 years old). Soil samples from five layers (0–5, 5–10, 10–20, 20–30, and 30–50 cm) were collected from NF and CFP before and after rainfall event in the Peng Chongjian watershed, Jiangxi Province. The physical properties of the soils, including the mean and coefficient of variation (CV) of soil moisture content and the soil particle composition, were determined in both forest types. The δD of soil water and the litter water-holding capacity were also measured. The results showed that the variation ranges of moisture content in each soil layer after the rainfall was 21.13%–49.40% in CFP and 21.33%–43.87% in NF. There were no significant differences in soil bulk density or porosity; the clay and silt contents were significantly increased in topsoil, while the sand was significantly decreased (P < 0.05). After the rainfall, soil water in CFP responded more promptly than NF. In the process of infiltration, the contribution of rainfall to soil moisture gradually decreased with increasing soil depth. Topsoil (0–5 cm) in NF responded promptly to rainfall, but the response showed a lag effect with the increase of soil depth. With the extension of infiltration time, the contribution of precipitation to deep soil gradually increased. The results showed that the soil did not degrade after the conversion of NF to CFP, a significant guiding result for plantation cultivation.

Forest litter plays an important role in the hydrological process of an ecosystem, but the mechanism of inter-ception is not well understood and has not been fully evaluated. We conducted a process-based experiment under five simulated rainfall intensities. We directly quantified the interception of leaf litter and determined the effects of litter mass (MA), rainfall characteristics (RI) and leaf type (SP) on the interception of six common subtropical tree species, including two coniferous (Cunninghamia lanceolata (Lamb.) Hook. and Pinus massoniana Lamb.) and four broadleaf deciduous (Phoebe bournei (Hemsl.) Yang, Schima superba Gardn. et Champ., Liquidambar for-mosana Hance and Cinnamomum camphora (L.) Presl) species. The results demonstrated the following. (1) The interception process of litter can be divided into three phases: the wetting phase, the saturation phase, and the postrainfall drainage phase. The first phase of which arrived approximately 95% of the maximum interception storage (Cmax) and the duration was longer in broadleaf species than in coniferous species. This phase was significantly different among the species and rainfall characteristics, but it was not affected by litter mass. (2) Cmax and the minimum interception storage capacity (Cmin)of litter were not significantly different between the two forest types, but among the six species, especially between P.bournei and each of the two coniferous species, these values showed the greatest differences. (3) Cmax and Cmin increased significantly with litter mass and rain intensity. (4) Based on commonality analysis, the interaction between MA and RI largely outweighed the other variables in terms of their contribution to Cmax; however, MA surpassed all the other variables in its contribution to Cmin. We also found that the effects of the individual variables on Cmax and Cmin as well as their interactions, were significantly different; the three most influential variables for Cmax ranked in the descending order of their contributions were the interaction between MA and RI (41.07%), RI alone (23.69%), and MA (20.81%), and those for Cmin were MA alone (52.59%), the interaction between MA and RI (25.81%) and leaf types (14.58%). The quantitative and mechanistic explanations regarding the effects of leaf types, rainfall characteristics, litter mass and their interactions on litter Cmax and Cmin presented in this study are expected to increase our under-standing of the mechanism underlying litter interception.

Litterfall is an important part of the process of nutrient circulation and energy flow in forest ecosystems. Mountain forests are strongly eroded by running water in that the surface soil is thinner, and the terrain is complex and diverse. They are more sensitive to climate change, which will affect the ecological processes and carbon sink functions of forest ecosystems. Taking Lushan Mountain as an example, we studied the dynamic characteristics of litterfall components, seasonal changes in carbon input and the influencing factors of typical forest communities in the subtropics. The results showed that the total annual average litterfall components of evergreen broad-leaved forest (EBF) > artificial coniferous forest (ACF) > deciduous broad-leaved forest (DBF) > renew young forest (RYF), and that leaf litterfall is the first productivity in the litterfall components, and the peak of litterfall is mainly concentrated in spring and autumn, showing a single- or double-peaked change pattern. There was a linear relationship between the components of litterfall in the four forest communities and the stand factor, but the correlation degree R-2 was small. Overall, the results showed that the total amount of litterfall in the four forest communities was affected by canopy density and stand density. Light, temperature and water at different altitudes had different effects on the amount of litterfall, with excessive temperatures at lower altitudes likely to limit forest growth and development under adequate light and water, and the opposite was true at higher altitudes. The results of Pearson correlation analysis showed that EBF and DBF were negatively correlated with rainfall, that ACF and RYF were negatively correlated with temperature and rainfall, and that wind speed was positively correlated. The average annual carbon input size of the four forest communities was EBF > ACF > RYF > DBF, which may be related to environmental conditions and vegetation types, and the seasonal differences were arranged in order of spring > autumn > summer > winter. It can be seen that, considering performance under future climate change, EBF is more conducive to nutrient input and has good soil fertility maintenance ability.

Aims Nitrous oxide (N2O) plays an important role in global climate change. Plant expansion can alter soil nutrient cycling and greenhouse gas (GHG) fluxes but the effects of fine root litter mixing from plant expansion on litter decomposition, nutrient cycling, and GHG fluxes are poorly understood. Methods To evaluate the impacts of fine root litter mixing from plant expansion on GHG budgets, we conducted an in situ study over sixteen months in Japanese cedar (Cryptomeria japonica) plantations experiencing moso bamboo (Phyllostachys edulis) expansions. Litter decomposition and N2O production were quantified in a full-factorial complete-randomized design by comparing fine root litter of Japanese cedar, moso bamboo or their mixtures, with or without nitrogen (N) addition. Results We found that litter mixing accelerated decomposition, demonstrating a synergistic non-additive effect (19% increase in mass loss). This might have accelerated release of chemicals that inhibit microbial activities because litter mixtures had lower microbial biomass. Soil N2O emissions in the mixed litter treatment were 16.8% and 24.4% lower than those with only cedar or bamboo litter, respectively. N deposition promoted mass loss of mixed litter (28% increase in mass loss) and increased N2O emissions by 36.7%, 60.6% and 33.6% from cedar, mixed and bamboo litter treatments, respectively. Conclusion The expansion of moso bamboo promotes the return of soil nutrients, reduces N2O emissions, and potentially mitigates GHG emissions. However, with increasing N deposition in the future, moso bamboo expansion will likely contribute to global warming.

Moso bamboo expansion is common across the world. The expansion of moso bamboo into adjacent forests altered plant and soil characteristics. While the community structure of soil fungi and bacteria plays an important role in maintaining the function of forest ecosystems, changes in microbial community compositions remain unclear, limiting our understanding of ecological process changes following moso bamboo expansion. To explore changes in the community structure of soil fungi and bacteria in Japanese cedar plantations experiencing expansion of moso bamboo, Illumina NovaSeq high-throughput sequencing technology was used to elucidate changes in soil microbial communities as well as alteration in litter and soil chemical characteristics. The results showed that moso bamboo expansion decreased content of soil organic carbon, total nitrogen, litter carbon, and the carbon to nitrogen ratio as well as the number of bacterial operational taxonomic units (OTUs) at the genus level, the α-diversity Simple index, and the abundance of Acidobacteria, Chloroflexi, and Gemmatimonadetes. Moso bamboo expansion also increased soil NH4+-N, pH, while it decreased fungi OTUs at the phyla, class, order, family, and genus level. The expansion of moso bamboo into Japanese cedar substantially altered soil fungal and bacterial community structure, which might have implications for changes in the ecosystem element-cycling process. In the forest ecosystem and expansion management of moso bamboo, the types and different expansion stages of moso bamboo should be paid attention to, in the assessment of ecological effects and soil microbial structure.

Plant community formation is determined by plant competition, while the water uptake depth of vegetation is regarded as a critical factor in maintaining species coexistence under competition. However, the source variation of montane plant water uptake remains poorly understood, especially under the condition of climate change. We introduced stable hydrogen and oxygen isotopes to investigate the water uptake pattern of the trees and shrubs in a Pinus taiwanensis Hayata community in subtropical mountains. The results showed that the main sources of water uptake in plants varied with soil water content, due to variations in annual precipitation distribution. In July and September, under extremely wet conditions, the evergreen conifer species P. taiwanensis and the shrub Eurya muricata mainly absorbed water from the deep soil layer (40–80 cm, more than 70%). By contrast, the deciduous shrub Rhododendron dilatatum largely relied on upper soil water (0–40 cm, 75.4%) in July but the same deep water source in September. In August and the non-growing season (January), when soil moisture content was low, plants preferred surface layer soil water (0–20 cm, above 50%). In October, the soil water in the middle (20–40 cm) and deep layers (40–80 cm) were the main water source of the three plants. However, the plant water sources showed great difference between P. taiwanensis and shrubs in November: P. taiwanensis absorbed more water from the soil surface layers (89.5%), while R. dilatatum mainly took up surface soil water (54.2%) and E. muricata predominantly obtained water from surface soil water (49.6%) and the deep soil layer (39.3%). These findings suggest that the water uptake of dominant woody plants in a P. taiwanensis community has great plasticity, and its water uptake depth varies with soil water content. In addition, these co-existing species generally absorbed water from similar soil layers in the P. taiwanensis community and exhibited a hydrological niche overlap, indicating a very possible competition between species in future water-limited conditions caused by climate change.

研究植被恢复条件下土壤水稳性团聚体颗粒有机碳的分布特征及影响因素,为退化红壤区生态系统重建与土壤质量改善提供理论依据。在江西省泰和县植被恢复与重建基地,选取立地条件基本一致的马尾松纯林、湿地松纯林、木荷纯林、马尾松补植木荷、湿地松补植木荷、湿地松—木荷原始混交林6种恢复模式,于2019年通过调查取样和试验分析,探索不同植被恢复模式土壤各粒级水稳性团聚体颗粒有机碳(POC agg )、土壤物理化学性质变化特征及相互关系。结果表明:（1）退化红壤以水稳性大团聚体（＞0.25 mm）为主（百分比含量为87%）,木荷纯林、马尾松补植木荷林土壤大团聚体含量最低。表层（0—10 cm）土壤POC agg 受恢复模式影响最显著（P＜0.05）,以湿地松纯林POC agg 含量为最高（14.44 g/kg）;（2）土壤物理化学性质因恢复模式的不同而呈显著性差异,其中湿地松补植木荷林下土壤有机质（SOM）、木荷纯林下土壤全氮（TN）、湿地松纯林下土壤全磷（TP）含量分别为最高;（3）人工针叶纯林中团聚体组成对POC agg 影响最大,团聚体组成、SOM和TN是影响POC agg 的重要因素（P＜0.01）,且土层越深关联度显著增加（P＜0.01）;其中微团聚体（＜0.25 mm）POC agg 受其直接或间接效应均较高,TN在＜0.053 mm粒级团聚体POC agg 的影响最大。木荷纯林能明显改善土壤结构和肥力,且湿地松对林下土壤养分尤其是POC agg 固持能力较高。结合退化红壤区生态修复实践,以湿地松纯林作为先锋树种进行植被恢复,抚育过程中补植木荷可能会更好地改善土壤性质。

[目的]研究庐山日本柳杉早材、晚材宽度与温度、降水量的相关关系,以揭示日本柳杉早材、晚材径向生长对气候的响应规律,了解这一区域气候变化对森林生态系统的影响,并为未来气候变化条件下日本柳杉的保护和造林区域选择提供依据.[方法]以庐山自然保护区的人工林针叶树种日本柳杉为研究对象,采用树木年轮学的方法对日本柳杉进行了树芯样品取样和处理,并建立早材、晚材标准年表,将树木标准年表与庐山地区的气候要素进行相关性分析.[结果](1)早材年表各项统计特征均优于晚材年表,相比于晚材的径向生长,早材径向生长对月均温变化更加敏感.(2)该地区年均温度、年降水呈现显著增加的趋势,除了8月份以外,各个月份均温呈上升的趋势.(3)日本柳杉径向生长主要受温度影响,日本柳杉早材生长过程中气温的滞后效应尤为明显,夏季(7月)高温不仅阻碍当年早材年轮宽度的生长,还会影响到下一个生长季早材的形成.生长季时期(4-7月)降水量的增加有利于早材、晚材年轮的形成.[结论]不同季节温度、降水量变化影响早材、晚材年轮形成与生长.在未来气候变暖的背景 下,庐山地区日本柳杉林可能出现生长下降的现象.

[目的]研究选用SPEI(标准化降水蒸散指数)分析庐山自然保护区干旱状况,及其对日本柳杉(Cryptomoria japonica)径向生长的影响,为庐山日本柳杉的生长和林分经营等提供一些理论依据.[方法]通过建立STD(树轮年表)的树轮宽度指数来反映庐山日本柳杉的径向生长量情况,计算分析SPEI来反映庐山自然保护区近几十年来的干旱变化情况.采用Mann-Kendall突变检验、相关性检验分析、小波分析、多元回归等方法探讨研究庐山日本柳杉径向生长量以及干旱变化.[结果]研究发现:(1)在1967—1970年、1977—1981年、2004—2012年庐山日本柳杉生长情况低于预期标准;(2)标准化降水蒸散指数随时间尺度的增大,波动周期越来越长较长,相对而言,SPEI12更为集中、波动较小,能够更好更准确的反映干旱年变化特征.SPEI12反映出庐山1967—1970年达到重旱程度,1978—1980年特旱,2002—2003年中旱,2005—2013年中旱至重旱;(3)树轮宽度指数与月尺度、半年尺度标准化降水蒸散指数呈显著正相关,与年尺度标准化降水蒸散指数呈极显著正相关关系.同时树轮宽度指数与上年8月至当年6月年尺度标准化降水蒸散指数呈显著正相关,其中与当年5月呈极显著正相关.[结论]日本柳杉生长量的周期变化与干旱周期变化接近,日本柳杉生长量变化相对干旱的变化会持续一到两年左右.

以庐山自然保护区3个不同海拔样地采集的138根日本柳杉样芯为研究材料,利用树木年轮学方法分析其径向生长与季节和月气候因子的响应关系.结果 表明:低海拔处日本柳杉径向生长对气候因子的响应相比于中、高海拔更敏感;中、低海拔径向生长与春季相对湿度呈显著正相关(P＜0.05),低海拔径向生长与春季日照时数、夏季均温呈显著负相关(P＜0.05),而中海拔径向生长与夏、秋季均温呈显著负相关(P＜0.05);高海拔径向生长与各个季节气候因子表现出一定的相关性,但相关性不显著;3个海拔径向生长均与当年1月均温呈显著正相关(P＜0.05),中、低海拔径向生长与上年7月及当年7月均温呈显著负相关(P＜0.05),高温会抑制树木的生长,低海拔径向生长与当年4月空气相对湿度、降水量呈显著正相关(P＜0.05),与当年4月日照时数呈显著负相关(P＜0.05),随海拔的升高相关性降低;庐山日本柳杉径向生长与主要气候要素之间的相关性呈现出明显的季节性,日本柳杉径向生长主要受上年7及7月均温和4月空气相对湿度的影响,海拔是影响日本柳杉径向生长对气候因子响应的重要因素,最终建立的标准年轮宽度年表适合进行树木年轮气候学的研究.

为了探究不同植被恢复模式对土壤碳（C）、氮（N）、磷（P）分配格局及其生态化学计量特征的影响,为红壤侵蚀区的植被恢复措施及生态治理模式优化提供科学依据,以江西省泰和县红壤严重退化地为研究对象,对研究区马尾松纯林、湿地松纯林、木荷纯林、马尾松木荷混交林（马木混交林）以及湿地松木荷混交林（湿木混交林）5种植被恢复模式0—20,20—40cm土层不同粒径水稳性团聚体C、N、P分配格局及其化学计量特征进行了研究。结果表明:（1）0—40cm不同粒径团聚体分别占总重56.34%（＞2mm）,30.01%（0.25～2mm）,7.14%（0.053～0.25mm）,6.54%（＜0.053mm）,各植被恢复模式土壤水稳性团聚体含量随着粒径的减小而降低,且差异显著（p＜0.05）,马木混交林＞2mm土壤水稳性团聚体含量显著高于其他恢复模式（p＜0.05）;（2）各植被恢复模式土壤C、N、P含量以马木混交林及湿地松纯林较高,水稳性团聚体C、N、P的含量总体随着粒径减小呈升高的趋势,以较小粒级养分含量较高,且存在显著差异（p＜0.05）;土层间C、N含量差异显著,P无显著差异,C∶N、C∶P及N∶P存在显著差异（p＜0.05）;粒径间C∶N、C∶P及N∶P存在显著差异;土壤团聚体C、N与C∶N、C∶P、N∶P均呈极显著相关关系,N∶P值较高且P与N∶P存在显著负相关性（p＜0.05）;（3）土壤C、N与土壤团聚体C、N含量显著相关（p＜0.05）,土壤团聚体C、N与土壤容重及含水率存在极显著相关性（p＜0.01）。研究结果表明,不同植被恢复模式对土壤养分的改善作用主要集中于表层土壤;土壤团聚体养分对土壤养分状况具有指示作用,且土壤团聚体养分保持能力与土壤物理性质有关;研究区植被生长限制因素以P限制为主且大团聚体和微团聚体受P限制作用更严重;马木混交林较其它植被恢复模式对土壤质量和结构提升均具有显著作用。

利用热扩散式探针法对庐山自然保护区内不同胸径大小的日本柳杉在2016年7月树干液流情况进行连续监测,并同期监测样地区域的气象因子(降雨、气温、湿度、太阳辐射等),揭示不同胸径日本柳杉的液流变化规律和蒸腾耗水特征以及对主要气象因子改变的响应情况.结果 表明:液流呈现明显昼夜变化规律,其日变化呈多峰曲线型,平均每日峰的次数晴天约3.5次,雾天3次;在典型晴天,液流每日平均起始时间为6:45,总持续时间15h,首次峰值出现时间约为11:45,峰值总持续时间4.25 h,雾天,液流每日平均起始时间为7:30,总持续时间11.5 h,首次峰值出现时间约为10:45,峰值总持续时间4.5 h,且液流峰值出现时间、下降时间、结束时间、最大峰值出现时间雾天均要早于晴天;不同胸径树干液流的日变化规律有差异,总体来看,随着树干胸径的增加,液流日波动次数增加,各样树的液流首次到达峰值和峰值结束的时间分布不同,液流最大峰值随着胸径的增加而增大;晴天液流日均值与胸径的大小存在良好线性正相关关系,而雾天的线性相关拟合一般,太阳辐射和大气水汽压亏缺(VPD)是树干液流的主要影响因素,树干液流对太阳辐射和VPD均以幂函数形式呈正相关关系,液流变化对于太阳辐射变化存在45～ 135min的时滞效应,但是其峰值持续时间比太阳辐射峰值持续时间少1h;在典型晴天,胸径越大树木日总蒸腾量越大,蒸腾量与胸径以幂函数的形式呈现正相关关系,在雾天,蒸腾量与胸径之间的正相关性不如晴天.

为研究杉木人工林取代常绿落叶阔叶混交林后土壤水源涵养能力的变化,采用室内浸水法和环刀法分别研究杉木纯林和常绿落叶阔叶混交林的枯落物与土壤的持水特性.结果 表明:(1)枯落物平均蓄积量表现为常绿落叶阔叶混交林(3.42 t/hm2)＞杉木纯林(3.12 t/hm2),枯落物平均厚度表现为杉木纯林(9.17 cm)＞常绿落叶阔叶混交林(5.42 cm).(2)最大持水量表现为常绿落叶阔叶混交林(6.23 t/hm2)＞杉木纯林(5.57 t/hm2),最大持水率也表现出相同的规律,即常绿落叶阔叶混交林(184.40％)＞杉木纯林(179.50％);有效拦蓄量表现为常绿落叶阔叶混交林(4.48 t/hm2)＞杉木纯林(4.13 t/hm2),最大拦蓄量表现为常绿落叶阔叶混交林(5.41 t/hm2)＞杉木纯林(4.97 t/hm2).(3)枯落物层的吸水量与浸水时间符合对数函数Q=aln(t)+b,而吸水速率与浸水时间符合指数函数V=atb,常绿落叶阔叶混交林的蓄水能力强于杉木纯林.(4)土壤水分最大吸持贮水量表现为常绿落叶阔叶混交林(43.58 mm)＞杉木纯林(41.88mm),可以看出常绿落叶阔叶混交林内的土壤可以更好地为植被提供良好的水分供其生长;土壤水分最大滞留贮存量表现为常绿落叶阔叶混交林(8.20 mm)＜杉木纯林(10.22mm),即杉木纯林内的土壤具有更好的涵养水源能力.从枯落物最大持水量、有效拦蓄量以及土壤毛管孔隙度、非毛管孔隙度等多个因素的计算综合推断可知,杉木人工林水源涵养能力优于常绿落叶阔叶混交林.