Species diversity of Chinese beech forests in relation to warmth and climatic disturbances

The trends in the occurrence of climatic disturbances in the ChineseFagus range are described, and the relationship between woody species diversity and climatic factors in eight old-growth Chinese beech forests is characterized. In the ChineseFagus range that lies in the humid mountains of southern China, wind storms and heavy rain frequency increase towards the eastern coast. Thunderstorm frequency increases southwards. Snowfall frequency increases northwards. Glaze storm frequency peaks in the center near Lake Dongtian, but much higher in the east than in the west. Hailstorm frequency also peaks in the center. The forests sampled in this study are widely separated. Their canopies consist of either deciduous broad-leaved trees or a mixture of evergreen and deciduous broad-leaved trees. Their species diversity increases towards warmer sites and towards the east. The importance of the evergreen trees in relation to warmth and minimum temperature increases southwards. Our analysis suggests that wind storms and heavy rains enhance the species diversity of Chinese beech forests. Cold disturbances such as glaze and snow diminish the diversity and canopy dominance of evergreen broad-leaved trees but favor deciduous broad-leaved trees, especially beech. The annual precipitation received by the forests in this study varies from 1400–2550 mm. This is not correlated with diversity, however, probably because all of these forests grow in humid conditions with sufficient water being supplied by precipitation throughout the year.     

哀牢山中山湿性常绿阔叶林木径向生长季节动态及其对气候因子的响应

研究采用树木生长环在哀牢山中山湿性常绿阔叶林持续9年(2009—2017年)监测了2个常绿树种(厚皮香,Ternstroemia gymnanthera;南亚枇杷,Eriobotrya bengalensis)和2个落叶树种(西桦,Betula alnoides;珍珠花,Lyonia ovalifolia)的树干月生长量,采用逻辑斯蒂生长模型(Logistic model)模拟树木径向生长量和物候参数,并分析了年、季尺度上径向生长与主要气候因子的关系。结果表明:1)4个树种年平均生长量为6.3 mm,落叶树种年平均生长量(10.6 mm/a)显著高于常绿树种(3.0 mm/a);2)雨季(5—10月)是哀牢山中山湿性常绿阔叶林树木生长的主要时期,4个树种雨季平均生长量为5.9 mm,占全年总生长量的93%,其中落叶树种雨季生长量占全年的96%,而常绿树种雨季生长量占全年的86%;3)常绿树种生长季长度为169天,长于落叶树种(137天),而落叶树种最大生长速率(0.14 mm/d)显著高于常绿树种(0.03 mm/d),最大径向生长速率能很好地预测树种年生长量;4)低温、雾日和光合有效辐射是影响哀牢山亚热带常绿阔叶林4个研究树种径向生长的重要环境因子,其中温度对常绿树种径向生长具有显著影响,而雨日、雾日与空气湿度等水分因子对落叶树种径向生长更为重要。常绿树种年生长量对旱季气候因子的响应相比落叶树种更为敏感,树木旱季生长量除了受低温限制外,也受到水分供给的影响。气候变化可能改变不同物候类型树种在哀牢山中山湿性常绿阔叶林中的生长状态与分布格局。     

冠层结构和光环境的时空变化对紫耳箭竹种群特征的影响

选择金佛山国家自然保护区内落叶阔叶林、常绿落叶阔叶混交林、常绿阔叶林3种典型群落类型,研究冠层结构和光环境特征,以及林下优势种--紫耳箭竹的种群特征.结果表明: 随着落叶阔叶林→常绿落叶阔叶混交林→常绿阔叶林的演替,Shannon多样性指数、Simpson优势度指数和Pielou指数呈增加趋势,表明群落趋于稳定发展的状态;冠层结构特征也发生了显著改变,冠层开度和平均叶倾角减小,叶面积指数增加,冠层的消光能力增强,林下光照水平降低.上层林冠是造成林型郁闭的主要原因,其中冠层厚度和冠层面积是2个主要的影响因素.冠层结构与林下光照指标显著相关,对林下散射光的影响最大.冠层开度、林下光照条件均随着生长季的到来而下降,而叶面积指数呈现增长的趋势,峰值出现在6、7月;平均叶倾角在春季达到最大值,在夏季为最小值.紫耳箭竹的生长与冠层结构和光环境密切相关,其在光照适中的常绿落叶阔叶混交林中生长得最好,分株粗壮、密度大(29.69±1.68株·m^-2),地下茎拓展能力强;落叶阔叶林中的强光环境可能造成土壤水分缺失,从而对其生长产生影响;而在常绿阔叶林的低光环境下紫耳箭竹分株矮小,密度小(5.80±1.16株·m^-2),克隆扩展能力降低.在森林结构演变的过程中,冠层结构发生了明显的改变,显著影响林下光环境,过度的低光环境对紫耳箭竹种群的更新和发展有限制作用.     

Ecophysiological responses of two closely related Magnoliaceae genera to seasonal changes in subtropical China

Aims Plants use a variety of hydraulic strategies to adapt to seasonal drought that differ by species and environmental conditions. The early-diverging Magnoliaceae family includes two closely related genera with contrasting leaf habits, Yulania (deciduous) and Michelia (evergreen), which naturally inhabit temperate and tropical regions, respectively. Here, we evaluate the hydraulic strategy of species from both genera that have been ex situ conserved in a subtropical region to determine how they respond to the novel cool–dry season climatic pattern.Methods We measured ecophysiological traits in five Michelia and five Yulania species conserved in the South China Botanical Garden in both wet and dry season conditions and monitored the whole-year sap flow for four of these species.Important findings We found that Magnoliaceae species that have been ex situ conserved in a subtropical climate did not suffer from excessive water stress due to the mild drought conditions of the dry season and the ecophysiological adjustments the species made to avoid this stress, which differed by leaf habit. Specifically, deciduous species completely shed their leaves during the dry season, while evergreen species decreased their turgor loss points, dry mass based photosynthetic rates, stomatal conductance and specific leaf areas (SLAs) compared to wet season measurements. In comparing the two distinct leaf habits during the wet season, the leathery-leaved evergreen species had higher leaf hydraulic conductance and leaf to sapwood area ratios than the papery-leaved deciduous species, while the deciduous species had greater hydraulic conductivity calculated on both a stem and leaf area basis, dry mass based photosynthetic rates, leaf nutrients, SLAs and stomatal sizes than the evergreen species. Interestingly, species from both genera maintained similar sap flow in the wet season. Both photosynthetically active radiation and vapour pressure deficit affected the diurnal patterns of sap flow in the wet season, while only vapour pressure deficit played a dominant role in the dry season. This study reveals contrasting hydraulic strategies in Yulania and Michelia species under subtropical seasonal conditions, and suggests that these ecophysiological adjustments might be affected more by leaf habit than seasonality, thus reflecting the divergent evolution of the two closely related genera. Furthermore, we show that Magnoliaceae species that are ex situ conserved in a subtropical climate are hydraulically sound, a finding that will inform future conservation efforts of this ancient family under the threat of climatic change.     

Species-Specific Growth Responses to Climate Variations in Understory Trees of a Central African Rain Forest

Basic knowledge of the relationships between tree growth and environmental variables is crucial for understanding forest dynamics and predicting vegetation responses to climate variations. Trees growing in tropical areas with a clear seasonality in rainfall often form annual growth rings. In the understory, however, tree growth is supposed to be mainly affected by interference for access to light and other resources. In the semi-deciduous Mayombe forest of the Democratic Republic of Congo, the evergreen species Aidia ochroleuca, Corynanthe paniculata and Xylopia wilwerthii dominate the understory. We studied their wood to determine whether they form annual growth rings in response to changing climate conditions. Distinct growth rings were proved to be annual and triggered by a common external factor for the three species. Species-specific site chronologies were thus constructed from the cross-dated individual growth-ring series. Correlation analysis with climatic variables revealed that annual radial stem growth is positively related to precipitation during the rainy season but at different months. The growth was found to associate with precipitation during the early rainy season for Aidia but at the end of the rainy season for Corynanthe and Xylopia. Our results suggest that a dendrochronological approach allows the understanding of climate–growth relationships in tropical forests, not only for canopy trees but also for evergreen understory species and thus arguably for the whole tree community. Global climate change influences climatic seasonality in tropical forest areas, which is likely to result in differential responses across species with a possible effect on forest composition over time.     

Simulating phenological shifts in French temperate forests under two climatic change scenarios and four driving global circulation models

After modeling the large-scale climate response patterns of leaf unfolding, leaf coloring and growing season length of evergreen and deciduous French temperate trees, we predicted the effects of eight future climate scenarios on phenological events. We used the ground observations from 103 temperate forests (10 species and 3,708 trees) from the French Renecofor Network and for the period 1997–2006. We applied RandomForest algorithms to predict phenological events from climatic and ecological variables. With the resulting models, we drew maps of phenological events throughout France under present climate and under two climatic change scenarios (A2, B2) and four global circulation models (HadCM3, CGCM2, CSIRO2 and PCM). We compared current observations and predicted values for the periods 2041–2070 and 2071–2100. On average, spring development of oaks precedes that of beech, which precedes that of conifers. Annual cycles in budburst and leaf coloring are highly correlated with January, March–April and October–November weather conditions through temperature, global solar radiation or potential evapotranspiration depending on species. At the end of the twenty-first century, each model predicts earlier budburst (mean: 7 days) and later leaf coloring (mean: 13 days) leading to an average increase in the growing season of about 20 days (for oaks and beech stands). The A2-HadCM3 hypothesis leads to an increase of up to 30 days in many areas. As a consequence of higher predicted warming during autumn than during winter or spring, shifts in leaf coloring dates appear greater than trends in leaf unfolding. At a regional scale, highly differing climatic response patterns were observed.     

Seasonal and diel variations in the activity of canopy insect herbivores differ between deciduous and evergreen plant species in a tropical dry forest

This study evaluated whether herbivorous insects can be expected to have particular adaptations to withstand the harsh dry season in tropical dry forests (TDFs). We specifically investigated a possible escape in space, with herbivorous insects moving to the few evergreen trees that occur in this ecosystem; and escape in time, with herbivores presenting an increased nocturnal rather than diurnal activity during the dry season. We determined the variation in the free-feeding herbivorous insects (sap-sucking and leaf chewing) between seasons (beginning and middle of both rainy and dry seasons), plant phenological groups (deciduous and evergreen trees) and diel period (diurnal and nocturnal) in a Brazilian TDF. We sampled a total of 5827 insect herbivores in 72 flight-interception traps. Contrary to our expectations, we found a greater herbivore diversity during the dry season, with low species overlap among seasons. In the dry season, evergreen trees supported greater richness and abundance of herbivores as compared to deciduous trees. Insects were also more active at night during the dry season, but no diel differences in insect abundance were detected during the rainy season. These results indicate that the strategies used by insect herbivores to withstand the severe climatic conditions of TDFs during the dry season include both small-scale escape in space and time, with evergreen trees playing a key role in maintaining resident insect herbivore populations in TDFs. Relatively more nocturnal activity during the dry season may be related to the avoidance of harsh climatic conditions during the day. We suggest that the few evergreen tree species occurring in the TDF landscape should be especially targeted for protection in this threatened ecosystem, given their importance for insect conservation.     

Pattern of changes in species diversity,structure and dynamics of forest ecosystems along latitudinal gradients in East Asia

We examined effects of seasonality of climate and dominant life form (evergreen/deciduous, broad-leaf/coniferous) together with energy condition on species diversity, forest structure, forest dynamics, and productivity of forest ecosystems by comparing the patterns of changes in these ecosystem attributes along altitudinal gradients in tropical regions without seasonality and along a latitudinal gradient from tropical to temperate regions in humid East Asia. We used warmth index (temperature sum during growing season, WI) as an index of energy condition common to both altitudinal and latitudinal gradients. There were apparent differences in patterns of changes in the ecosystem attributes in relation to WI among four forest formations that were classified according to dominant life form and climatic zone (tropical/temperate). Many of the ecosystem attributes—Fishers alpha of species-diversity indices, maximum tree height and stem density, productivity [increment rate of aboveground biomass (AGB)], and population and biomass turnover rates—changed sharply with WI in tropical and temperate evergreen broad-leaved forests, but did not change linearly or changed only loosely with WI in temperate deciduous broad-leaved and evergreen coniferous forests. Values of these ecosystem attributes in temperate deciduous broad-leaved and evergreen coniferous forests were higher (stem density was lower) than those in tropical and temperate evergreen broad-leaved forests under colder conditions (WI below 100°C). Present results indicate that seasonality of climate and resultant change in dominant life form work to buffer the effects of energy reduction on ecosystem attributes along latitudinal gradients.     

雌雄异株植物山杨的气候响应差异

本文通过建立长白山阔叶红松林内雌雄异株植物山杨树轮宽度序列及标准化年表,分析不同气候条件下的生长差异及其与气候因子的关系,以期揭示性别因素对植株径向生长 气候因子关系的影响.结果表明： 不同气候条件下雌雄植株年径向生长速率存在显著差异,对气候因子的响应也有所不同.1980年以前,山杨雌株年均生长速率显著高于雄株,雌株与生长季末低温、上年生长季末和当年生长季降水量呈显著负相关,山杨雄株则与当年生长季温度呈显著正相关.1980年（含）以后,温度明显上升,尤其是最低温度,植株生长速率出现下降趋势,雌株生长速率显著低于雄株;雌株对低温变化更敏感,与上年生长季末低温呈显著负相关、与春季低温呈显著正相关,雄株与低温的相关关系均未达到显著水平.低温对长白山地区山杨雌株生长具有重要影响,在降水基本保持不变的条件下,低温的上升将明显抑制山杨雌株的生长,而对雄株影响不显著.     

西双版纳热带雨林和哀牢山亚热带常绿阔叶林雾特征研究

以西双版纳热带雨林和哀牢山亚热带常绿阔叶林为研究对象,利用PWS100天气现象仪获取两种森林类型的能见度数据。基于2014年西双版纳热带雨林和哀牢山亚热带常绿阔叶林的能见度数据,对两种森林类型雾的特征进行定量研究。研究结果表明:(1)西双版纳热带雨林全年雾日数为196 d,占全年的53.7%,哀牢山亚热带常绿阔叶林全年雾日数为100 d,占全年的27.4%,热带雨林全年雾日数几乎为亚热带常绿阔叶林雾日数的两倍;(2)热带雨林雨季和干季各占28.06%和71.94%,而亚热带常绿阔叶林雨季和干季各占72%和28%;(3)热带雨林一日内雾持续的最长时间为10.5 h,而亚热带常绿阔叶林雾生成和消散时间不定,一日内雾最长持续时间可达24 h,但雾发生的频率低于西双版纳热带雨林。两种森林类型全年雾日特征有明显的差异性,通过定量评价地处过渡带上的两种多雾森林生态系统雾特征,可为未来气候变化对不同森林生态系统碳水交换影响提供数据支撑。     

云南省三种典型气候带凋落物层弹尾类多样性分布格局

弹尾类是土壤动物中常见的优势类群,其作为土壤微食物网的重要组成部分,参与凋落物分解、土壤团聚体形成等重要生态过程。以往对弹尾类分布格局的研究通常关注其在不同海拔梯度或者不同生境类型下的分布情况,但在不同气候带下弹尾类多样性沿纬度分布格局仍不清楚。为讨论不同气候带下弹尾类沿纬度的分布格局及其潜在的环境影响机制,于2017年10月(雨季末期)在云南省同一经度(E 101°)分布的三种典型气候带设置海拔梯度样带:热带雨林(西双版纳,800 m、1000 m、1200 m、1400 m)、亚热带常绿阔叶林(哀牢山,2000 m、2200 m、2400 m、2600 m)、亚高山针叶林(丽江玉龙雪山,3200 m、3400 m、3600 m、3800 m),采集凋落物层弹尾类并调查分析土壤温度、土壤含水量、凋落物厚度、土壤pH、土壤容重及土壤孔隙度等环境因子。利用Berlese-Tullgren法收集土壤动物,共获得弹尾类19150只,隶属于10科29属,其中符■属(39.9%,等节■科)数量最多,其余优势属为棘■属(21.7%,棘■科)和球角■属(10.1%,球角■科),这3个属合计占总体的71.7%。凋落物层弹尾类的密度在亚高山针叶林明显高于热带雨林和亚热带常绿阔叶林,弹尾类的属数排序由多到少依次为热带雨林、亚高山针叶林、亚热带常绿阔叶林。通过最小二乘回归法对弹尾类多样性的海拔格局进行回归分析,得出弹尾类的丰富度指数(Margalef′s指数、Menhinick′s指数)、多样性指数(Shannon-Wiener多样性指数、Simpson多样性指数)和均匀度指数(Pielou均匀度指数)沿热带雨林、亚热带常绿阔叶林、亚高山针叶林呈单调递减格局。通过全模型子集回归筛选最佳环境模型表明,温度是影响弹尾类多样性沿不同气候带分布格局的主要环境因子。本研究为预测不同气候带下弹尾类多样性如何响应环境变化提供参考。     

Ecology of subtropical evergreen broad-leaved forests of Yunnan,southwestern China as compared to those of southwestern Japan

Subtropical evergreen broad-leaved forests of Yunnan, China, including mid-montane moist, monsoon, and semi-humid categories, were studied in terms of ecological attributes of pertinent species, diversity, structure, dynamics and succession, as compared with the subtropical/warm-temperate evergreen broad-leaved rain forest of southwestern (SW) Japan. The genera and species of the forests of Yunnan and SW Japan are East Asian elements and indicate a very close relationship between the respective floras, though different assemblages of species occur in the two regions. Diversity indices and numerical data on taxon richness at family, genus and species level were similar in both regions. Four types of gap-regeneration behaviors among the major tree species were recognized in the two areas. In both, as a result of long-term human activity, the plant communities ranged from pioneer deciduous broad-leaved and/or pioneer coniferous stands to late-successional evergreen broad-leaved stands. Succession in the two regions followed parallel paths, beginning with pioneer Alnus in Yunnan and Alnus, Mallotus and Styrax in Japan, accompanied by coniferous Pinus in the two areas, and with late-successional evergreen broad-leaved Cyclobalanopsis and Castanopsis as their final stage. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Variation in evergreen and deciduous species leaf phenology in Assam, India

In the present study phenological activities such as leaf and shoot growth, leaf pool size and leaf fall were observed for 3 years (March 2007–March 2010) in 19 tree species (13 evergreen and 6 deciduous species) in a wet tropical forest in Assam, India. The study area receives total annual average rainfall of 2,318 mm of which most rain fall (>70 %) occurs during June–September. Both the plant groups varied significantly on most of the shoot and leaf phenology parameters. In general, growth in deciduous species initiated before the evergreen species and showed a rapid shoot growth, leaf recruitment and leaf expansion compared to evergreen species. Leaf recruitment period was significantly different between evergreen (4.2 months) and deciduous species (6.8 months). Shoot elongation rate was also significantly different for evergreen and deciduous species (0.09 vs. 0.14 cm day^?1 shoot^?1). Leaf number per shoot was greater for deciduous species than for evergreen species (34 vs. 16 leaves). The average leaf life span of evergreen species (328 ± 32 days) was significantly greater than that of deciduous species (205 ± 16 days). The leaf fall in deciduous species was concentrated during the winter season (Nov–Feb), whereas evergreens retained their leaves until the next growing season. Although the climate of the study area supports evergreen forests, the strategies of the deciduous species such as faster leaf recruitment rate, longer leaf recruitment time, faster shoot elongation rate during favorable growing season and short leaf life span perhaps allows them to coexist with evergreen species that have the liberty to photosynthesize round the year. Variations in phenological strategies perhaps help to reduce the competition among evergreen and deciduous species for resources in these forests and enable the coexistence of both the groups.     

Variation of δ<Superscript>13</Superscript>C of wood and foliage with canopy height differs between evergreen and deciduous species in a temperate forest

We investigated post-photosynthetic fractionation and carbon transfer mechanisms of different plant functional types growing under the same climatic conditions in North-eastern China. The variations in δ¹³C of trunk and branches were compared with leaf δ¹³C at different canopy heights of Pinus koraiensis (evergreen coniferous species), Larix gmelinii (deciduous coniferous species) and Quercus mongolica (deciduous broad-leaved species). Results showed that δ¹³C of leaves increased (became more enriched) with increasing canopy height for both coniferous species (P. koraiensis, L. gmelinii) but not for Q. mongolica (a deciduous broad-leaved species). δ¹³C of both trunk and branches also increased with sampling height for the evergreen conifer P. koraiensis but did not significantly vary for either of the deciduous species (L. gmelinii or Q. mongolica), except a significant increase in branch δ¹³C for L. gmelinii. Similarly, δ¹³C of trunk and branches were strongly correlated with leaf δ¹³C only in the evergreen conifer, P. koraiensis. ¹³C was consistently more enriched in trunk, branches, and roots compared to leaves in all three species. Our findings suggest that, even under the same climatic conditions, different plant functional types may exhibit different carbon transfer mechanisms. This is contrary to the previous hypothesis that different carbon transfer mechanisms operate in forests of different climatic zones, especially in tropical and temperate forests. Particularly, the differences occur predominantly between evergreen and deciduous trees rather than between coniferous and broad-leaved trees. The significant difference in δ¹³C between leaves and wood tissues confirms a previous post-photosynthetic isotope fractionation in temperate forests.     

中国东部森林样带典型森林水源涵养功能

通过对我国东部森林样带四个森林生态系统定位研究站（长白山站、北京站、会同站和鼎湖山站）的九种森林类型水源涵养监测数据的分析,研究了水热梯度下不同森林生态系统水源涵养功能。结果表明：在生长季的5-10月份,各森林类型的水源涵养特性表现出较大差异。林冠截留率的大小依次为：阔叶红松林＞杉木林＞常绿阔叶林＞针阔混交林＞季风常绿阔叶林＞落叶阔叶混交林＞马尾松林＞落叶松林＞油松林,最高的长白山站阔叶红松林的截留率是最低的北京站油松林的2.2倍。森林降雨截留量与林外降雨量呈显著的正相关,林冠截留率与降雨量呈显著负相关。枯落物最大持水深（5-10月份）以北京站落叶阔叶林最大,为6.0mm;鼎湖山站的季风常绿阔叶林最小,为1.0mm。0-60cm土层蓄水量最大的是会同站的人工杉木林,为247mm;最小的是北京站的落叶松林,仅为45.5mm;林分总持水量依次为：杉木林＞阔叶红松林＞常绿阔叶林＞针阔混交林＞季风常绿阔叶林＞落叶阔叶混交林＞马尾松林＞落叶松林＞油松林。各林分总持水量主要集中在土壤层,占总比例的90%以上。     

Cambial growth dynamics and climatic control of different tree life forms in tropical mountain forest in Ethiopia

Munessa Forest is a mountain forest in south-eastern Ethiopia experiencing seasonal rainfall variation. We investigated seasonal cambial activity and dormancy from increment rates of four different tree species belonging to varying life forms, namely, evergreen native conifer (Podocarpus falcatus), evergreen introduced conifer (Pinus patula), evergreen broadleaved tree (Prunus africana) and deciduous broadleaved tree (Celtis africana). Measurements of stem radius fluctuations were registered with the help of high-resolution electronic dendrometers. Daily amplitudes of stem diameter variations and daily and monthly net growth rates were determined and related to climatic variables measured at local climate stations. Thin sections of wood collected with a microcorer every 3–6 weeks allowed a visual control of newly formed wood cells during consecutive time intervals. Lack of water availability during the long dry season induced cambial dormancy of 5–7 months depending on life forms. After the onset of the short rainy season, stem swelling started quite synchronously with a variation of only single days in all studied species. Evergreen tree species were able to initiate wood formation during the short rainy season, whereas growth in the deciduous broadleaved species started in the long rainy season. The acquired data provide a basis for delineating the species-specific growth boundaries and the duration of the cambial growing season.     

南亚热带常绿阔叶林地上碳储量空间分布特征及其影响因素

旨在探讨南亚热带常绿阔叶林地上碳储量空间分布特征及其影响因素,为了解该区域森林的碳汇功能提供理论依据。通过对鼎湖山南亚热带常绿阔叶林20 hm²固定森林样地调查数据,采用一元线性回归分析和主成分分析方法,划分优势种和非优势种,研究地上碳储量的空间分布和生物/非生物因素的影响,获取了以下结果:(1)优势种对鼎湖山南亚热带常绿阔叶林地上碳储量贡献更大(1533.85 Mg,74.72%),尤其是大径级物种(1389.68 Mg,67.69%)。优势种地上碳储量(CV=0.635)的空间分布较非优势种(CV=0.690)更加均匀。(2)物种多样性与优势种和总体地上碳储量负相关,而与非优势种正相关。(3)群落总体、优势种和非优势种的地上碳储量均与结构多样性显著正相关。然而,结构多样性对非优势种地上碳储量的影响程度高于优势种。(4)群落中的土壤营养度、凹凸度与地上碳储量正相关。综上所述,通过提升非优势种的物种多样性可以增加鼎湖山南亚热带常绿阔叶林地上碳储量。此外,改善土壤营养条件也有助于提升南亚热带森林的碳汇功能。     

Study on the Dynamics and Rhythms of Midmontane Wet Evergreen Broad-Leaved Forest at Xujiaba,Ailao Mountains,Yunnan

According to data of long-term observation, the dynamics and the rhythms of the wet evergreen broad-leaved forest in respect of seed germination, seedling growth, growth laws, and phenological rhythms of the mature trees of constituent species were analyzed. The species numbers of the seeds, germinable seeds and germinated seeds of the forest in rainy season were larger than those in dry season. The growth rate of the seedlings was faster in rainy season as well indicating a season most favourable for the growth of seedlings. The growth of trees was a process of inter-specific competition, self-regulation and self-thinning. The long and indistinctive phenologieal phases of the mature trees differed from those short and distinctive phenological phases of the broad-leaved forests in the temperate. Its continuous flowering, fruiting and fruit-falling were similar to the phenological rhythms of seasonal rain forests in Xishuangbanna. However, leaf-shedding of the seasonal rain forests in Xishuangbanna, the evergreen broad-leaved forests and the temperate broad-leaved forests was in spring (February ～March), in Winter (November ～ December) and in autumn (September～October) respectively. Based on the characteristics in the phenological rhythms of the species and their responses to the climates, the three eeo-phenological types were divided as: 1. The warm temperate eeo-phenological type, whieh accounts for 82 % of the total species number (50); 2. The temperate ecophenological type, 12%; 3. The cool temperate eco-phenological type, 0. 6 %.     

Global quantification of contrasting leaf life span strategies for deciduous and evergreen species in response to environmental conditions

Aim Species with deciduous and evergreen leaf habits typically differ in leaf life span (LLS). Yet quantification of the response of LLS, within each habit, to key environmental conditions is surprisingly lacking. The aim of this study is to quantify LLS strategies of the two leaf habits under varying temperature, moisture and nutrient conditions, using a global database. We hypothesize that deciduous LLS reflects the length of the growing season, avoiding unfavourable conditions regardless of the cause. Evergreen species adjust to unfavourable periods and amortize lower net carbon gains over several growing seasons, with increasing LLS associated with increasingly short favourable versus unfavourable season lengths. Location Global. Methods Data on LLS and environmental variables were compiled from global datasets for 189 deciduous and 506 evergreen species across 83 study locations. Individual and combined effects of measures of seasonality of temperature, water and nutrient availability on length of the growing season and on LLS were quantified using linear mixed models. The best models for predicting LLS were obtained using Akaike's information criterion (AIC) and ΔAIC. Results The LLS of deciduous and evergreen species showed opposite responses to changes in environmental conditions. Under unfavourable conditions, deciduous LLS decreases while evergreen LLS increases. A measure of temperature alone was the best predictor of the growing season. The LLS of deciduous species was independent of environmental conditions after expressing LLS in relation to the number of growing seasons. Evergreen species, on the other hand, adjusted to unfavourable conditions by increasing LLS up to four growing seasons. Contrary to expectations, variation in LLS was best explained solely by temperature, instead of by combined measures of temperature, moisture and nutrient availability. Shifts in the photosynthesis to respiration balance might provide a physiological explanation. Main conclusions Temperature, and not drought or nutrient availability, is the primary driver of contrasting responses of LLS for different leaf habit types.     

南京灵谷寺森林50年来的动态变化研究

 为进一步揭示北亚热带森林次生演替规律,于2002年5月在定点样带上沿用前人的方法,对南京灵谷寺森林进行了群落调查。通过比较1951、1981、2002年的定点样带资料,对灵谷寺森林的物种组成、多度、频度、重要值、种群结构以及物种多样性的动态变化进行了研究。50多年来,群落中立木株数相对基本稳定,但空间分布异质性逐渐增加,而林下苗木和灌木个体数波动幅度极大,由1951年的4 712株大幅上升至1981年的44 130株,到2002年又回落至7 372株。群落中物种数和建群种构成等都存在明显变化,物种数由1951年的75种下降到1981年的50种,2002年又上升为73种。物种多样性指数也存在波动,但目前尚未发现物种多样性指数有明显的上升或下降趋势。历经50多年的次生演替,早期人工针叶林中的马尾松（Pinus massoniana）逐渐衰退,首先被阳性落叶阔叶树,如黄连木（Pistacia chinensis）、枫香（Liquidambar formosana）等取代,之后又被相对耐荫的栓皮栎（Quercus variabilis）等树种所替代,一些常绿树种成功入侵,人工针叶林经针阔混交林、落叶阔叶林,逐渐向地带性植被落叶 常绿阔叶混交林方向演替,其中立地条件较好地段的群落演替速度也较快。