山东蒙山6种造林树种40余年成林效果评价

植被恢复一直是恢复生态学研究的核心问题和首要解决目标。该文拟评估山东蒙山森林植被恢复与重建的现状和程度, 评价不同造林树种对植物多样性的影响, 筛选一批造林工具种, 为今后沂蒙山区森林植被恢复与重建的调控和预测提供依据。采用样地法和样方法, 选择林龄超过40年的6种主要人工林为样地, 采用典型取样法进行林内调查。根据乔木层、灌木层和草本层的物种丰富度、Shannon-Wiener多样性指数、Simpson多样性指数和Pielou均匀度指数评价物种多样性, 分析乔木径级分布, 判断植物发展类型。结果表明: 乔木层、灌木层和草本层的4种多样性指数较为一致地显示赤松(Pinus densiflora)、栓皮栎(Quercus variabilis)、黑松(Pinus thunbergii)、日本落叶松(Larix kaempferi)和刺槐(Robinia pseudoacacia)的成林效果较好, 油松(Pinus tabuliformis)相对较差。6种人工林群落灌木层和草本层的4种多样性指数基本无显著差异, 而乔木层中, 油松人工林群落的4种多样性指数与黑松人工林、刺槐人工林、栓皮栎人工林和日本落叶松人工林存在部分显著差异(p < 0.05)。从整体上看, 人工林群落灌木层发育最好, 4种多样性指数均为灌木层>乔木层>草本层, 且差异大多极显著(p < 0.01)。研究发现: 乔木扩展种29种、隐退种3种、稳定侵入种9种和随机侵入种11种, 表明人工林群落正处于向森林演替的过程中。数据显示: 3种隐退种赤松、油松和日本落叶松均为群落局部优势种, 赤松和油松种群更新困难, 日本落叶松完全没有更新幼苗。作者认为林下发达的灌草层可能是阻碍针叶林天然更新的关键因素。评估筛选出15种造林工具种: 早期开荒工具种(A类) 7种和后期顶级工具种(B类) 8种。其中A1类(建群种) 2种: 赤松和油松, A2类(伴生种) 5种: 黄檀(Dalbergia hupeana)、花曲柳(Fraxinus rhynchophylla)、君迁子(Cerasus serrulata)、山合欢(Albizia kalkora)和鹅耳枥(Carpinus turczaninowii); B1类(建群种) 2种: 栓皮栎和麻栎(Quercus acutissima), B2类(伴生种) 6种: 水榆花楸(Sorbus alnifolia)、槲树(Quercus dentata)、山樱花(Diospyros lotus)、小叶朴(Celtis bungeana)、大叶朴(Celtis koraiensis)和三桠乌药(Lindera obtusiloba)。     

Effects of tree mortality on the spatial patterns and interspecific associations of plant species in a Quercus aliena var. acuteserrata forest in Baotianman,Henan, China

Aims Tree mortality is an important ecological process in forest ecosystems. The aims of this study were to determine how tree mortality influences the spatial patterns and interspecific associations of plant species, and what are the causes of tree mortality in a 1 hm² permanent plot in Baotianman National Nature Reserve, Nanyang City, Henan Province.
Methods We conducted field investigations in the plot and used spatial point pattern analysis to examine the spatial patterns and interspecific associations of 17 species prior to and following mortality.
Important findings (1) Most of the species in the study plot showed an aggregated distribution both pre- and post-mortality. However, the number of species showing aggregated distribution decreased and the number of species showing random distribution increased following the mortality event. (2) Most species were positively associated with Quercus aliena var. acuteserrata both pre- and post-mortality, while some had no apparent association. Following tree mortality, on fine scales, the number of species with positive associations increased, and the number of species with negative associations decreased. (3) Tree mortality was in consistency with the random death hypothesis. The interspecific associations of four species with Q. aliena var. acuteserrata completely changed following death. For most species, the spatial patterns and the interspecific association with Q. aliena var. acuteserrata either changed at minor scales or did not change. The variations in spatial patterns or interspecific associations were inconsistent among species. (4) The dead trees of Q. aliena var. acuteserrata were significantly associated with the living trees in 13 species, but the associations between dead and living trees were not in agreement with the changes in interspecific association following mortality. Only five living tree species competed with the dead trees of Q. aliena var. acuteserrata, and the competition between each of these species and Q. aliena var. acuteserrata intensified after individual death. Tree mortality is the result of a variety of factors. Although the tree mortality in the study plot was in accordance with the random death hypothesis, there were also a few individuals which were dead from competition.     

Leaf hydraulic traits and their trade-offs for nine Chinese temperate tree species with different wood properties

Aims Trees with different wood properties display variations in xylem anatomy and leaf vein structure, which may influence tree water transport efficiency and water-use strategy, and consequently constrain tree survival, growth and distribution. However, the effects of wood properties on leaf hydraulic conductance and vulnerability and their potential trade-offs at leaf level are not well understood. Our aims were to examine variations in leaf hydraulic traits of trees with different wood properties and explore potential trade-offs between leaf hydraulic efficiency and safety.
Methods Nine tree species with different wood properties were selected for measuring the leaf hydraulic traits, including three diffuse-porous species (Populus davidiana, Tilia amurensis, Betula platyphylla), three ring-porous species (Quercus mongolica, Fraxinus mandshurica, Juglans mandshurica), and three non-porous species (Picea koraiensis, Pinus sylvestris var. mongolica, Pinus koraiensis). Four dominant and healthy trees per species were randomly selected. The hydraulic traits measured included leaf hydraulic conductance on leaf area (K_area) and dry mass (K_mass) basis, leaf hydraulic vulnerability (P₅₀), and leaf water potential at turgor loss point (TLP), while the leaf structural traits were leaf dry mass content (LDMC), leaf density (LD) and leaf mass per unit area (LMA).
Important findings The K_area, K_mass, and P₅₀ differed significantly among the tree species with different woody properties (p < 0.05). Both K_area and K_mass were the lowest for the non-porous trees, and did not differ significantly between the diffuse-porous and ring-porous trees. The ring-porous trees had the highest P₅₀ values, while the diffuse-porous and non-porous trees showed no significant differences in P₅₀. Both K_area and K_mass were negatively correlated with P₅₀ (p < 0.05) for all the trees, and the relationships for the diffuse-porous, ring-porous, and non-porous trees were fitted into linear, power, exponential functions, respectively. This indicates that significant trade-offs exist between leaf hydraulic efficiency and safety. The K_mass was correlated (p < 0.01) with TLP in a negative linear function for the diffuse- and ring-porous trees and in a negative exponential function for the non-porous trees. The P₅₀ increased with increasing TLP. These results suggest that apoplastic and symplastic drought resistance are strictly coordinated in order to protect living cells from approaching their critical water status under water stresses. The K_mass was negatively correlated (p < 0.01) with LDMC, LD, or LMA, while the P₅₀ was positively correlated with LDMC and LD; this suggests that variations in K_mass and P₅₀ are driven by similar changes in structural traits regardless of wood traits. We conclude that the tree tolerance to hydraulic dysfunction increases with increasing carbon investment in the leaf hydraulic system.     

Carbon density characteristics of sparse Ulmus pumila forest and Populus simonii plantation in Onqin Daga Sandy Land and their relationships with stand age

Aims
Sparse Ulmus pumila forest is an intrazonal vegetation in Onqin Daga Sandy Land, while Populus simonii has been widely planted for windbreak and sand dune stabilization in the same region. Our objective was to compare the differences in carbon (C) density of these two forests and their relationships with stand age.
Methods
We measured the C content of tree organs (leaf, twig, stem, and root), herb layers (above ground vegetation and below ground root) and soil layers (up to 100 cm) in sparse Ulmus pumila forests and Populus simonii plantations of different stand ages, and then computed C density and their proportions in total ecosystem carbon density. In addition, we illustrated the variation in carbon density-stand age relationship for tree layer, soil layer and whole ecosystem. We finally estimated the C sequestration rates for these two forests by the space-for-time substitution approach.
Important findings
The average C contents of tree layer and soil layer for sparse Ulmus pumila forests were lower than those for Populus simonii plantations. The total C density of sparse Ulmus pumila forests was half of that of Populus simonii plantations. The carbon density of soil and tree layers accounted for more than 98% of ecosystem C density in the two forests. Irrespective of forest type, the C density ratios of soil to vegetation decreased with stand age. This ratio was 1.66 for sparse Ulmus pumila forests and 1.87 for Populus simonii plantations when they were over-matured. The C density of tree layer, soil layer, and total ecosystem in both forests increased along forest development. There were significantly positive correlations between tree layer’s C density and stand age in both forests and between the total ecosystem C density of sparse Ulmus pumila forests and stand age. The C sequestration rate of tree layer was 5-fold higher in Populus simonii plantation than in sparse Ulmus pumila forest. The ecosystem-level C sequestration rate was 0.81 Mg C·hm^-2·a^-1 for sparse Ulmus pumila forest and 5.35 Mg C·hm^-2·a^-1 for Populus simonii plantation. These findings have implications for C stock estimation of sandy land forest ecosystems and policy-making of ecological restoration and C sink enhancement in the studied area.     

模拟氮沉降对北京东灵山辽东栎林树木生长的影响

传统的元素限制模型认为氮是温带森林生长的限制元素, 不过该结论更多是从地上生物量以及群落水平进行阐述, 忽视了不同物种以及不同径级树木对外源氮的响应差异。辽东栎(Quercus wutaishanica)林是华北地区常见的森林类型, 该研究以北京东灵山辽东栎林为研究对象, 通过设置3个氮添加水平的实验, 即对照CK (0 kg·hm ^-2·a ^-1), N50 (50 kg·hm ^-2·a ^-1)和N100 (100 kg·hm ^-2·a ^-1), 模拟氮沉降对群落和物种水平以及不同径级树木生长的影响。经过7年氮添加, 实验结果显示: 物种水平上, 氮添加明显促进了优势树种辽东栎的生长; 群落水平上, 树木生长随氮浓度增加有不断上升趋势, 但统计学差异不显著; 氮添加显著抑制了辽东栎以及群落内小径级(3-10 cm)树木生长, 中(10-20 cm)、大径级(>20 cm)树木生长随氮沉降水平增加呈上升趋势, 但统计学差异不显著。表明氮是辽东栎以及温带森林树木生长的限制元素; 不同径级的辽东栎和群落内其他植物对氮添加响应不一致, 氮添加抑制了小径级树木生长, 中、大径级树木生长对氮添加响应不明显。     

Community characteristics and spatial distribution of dominant tree species in a deciduous broad-leaved forest of Muzhaling,Henan, China

Aims The objective of this paper is to quantify the species composition and spatial distribution pattern in a deciduous broad-leaved forest in temperate to subtropical ecological transition zone.
Methods In this study, a 3-hm² forest was selected in the temperate to subtropical ecological transition zone to analyze the community species composition, structure of diameter at breast height, community classification and spatial distribution pattern of dominant tree species.
Important findings Our results showed that in the plot there were 85 species, 52 genera and 31 families, mainly composed of Betulaceae, Celastraceae, Caprifoliaceae, Salicaceae and Aceraceae. Quercus aliena var. acuteserrata and Pinus armandii are dominant species of the community tree layer. The rare species and occasional species accounted for 20.0% and 28.24% of total species respectively. Size distribution of all species showed an invert J-shape, which indicates that the community is in a stable and normal growth status. Using multiple regression trees, the community in this plot can be divided into four categories: 1) Quercus aliena var. acuteserrata + Pinus armandii + Litsea tsinlingensis + Cerasus clarofolia + Lindera obtusiloba; 2) Quercus aliena var. acuteserrata + Salix chaenomeloides + Sorbus hupehensis; 3) Quercus aliena var. acuteserrata + Ailanthus altissima + Cerasus clarofolia + Litsea tsinlingensis; 4) Quercus aliena var. acuteserrata + Fraxinus chinensis + Litsea tsinlingensis + Philadelphus incanus. Under the completely random distribution model, the main species in the plot display clustered distributions, with the different species occurring in different habitat types, showing obvious terrain habitat preferences. However, under the heterogeneous Poisson distribution model, these species at different scales are distributed randomly or regularly. This study helps to understand the plant community species composition of the Muzhaling World Geopark, community structure and community distribution. The results show that the terrain habitat heterogeneity is an important factor influencing the spatial distribution of the species. The present work improves the understanding of plant community in Muzhaling World Geopark, and provides technical reference for biodiversity conservation and forest management of this area.     

基于序列trnL-trnF和ITS的榉属系统发育与地理分布格局的初步分析

榉属(Zelkova)是包含6个种的榆科小属, 呈东亚、西亚和南欧间断分布。该文基于DNA序列trnL-trnF和ITS构建了榉属的分子系统发育树, 大体上把此属分为3个分支, 分别对应东亚、西亚和南欧的种类, 与前人仅依据ITS序列的结果不同。生物地理的扩散和隔离分化分析(DIVA)表明, 榉属的原始祖先分布区可能是欧亚北温带, 包括了东亚、西亚和南欧的某个大的区域。分化过程以隔离分化为主要特征, 即3个分布区域是逐步隔离分化的。由于东亚的物种多样性, 北太平洋有可能是起源中心。榉属的现代分布格局可能主要是由于渐新世发生的古地中海西退、中新世发生的青藏高原大范围隆升, 以及第四纪冰川活动引起的分布区的收缩。     

Seasonality and drivers of stem CO2 efflux for four temperate coniferous tree species

Aims Stem CO₂ efflux (E_s) is an important component of annual carbon budget in forest ecosystems, but how biotic and environmental factors regulate seasonal and inter-specific variations in E_s is poorly understood. The objectives of this study were: (1) to compare seasonal dynamics in E_s for four temperate coniferous tree species in northeastern China, including Korean pine (Pinus koraiensis), Korean spruce (Picea koraiensis), Mongolian pine (Pinus sylvestris var. mongolica), and Dahurian larch (Larix gmelinii); and (2) to explore factors driving the inter-specific variability in E_s during the growing and non-growing seasons.
Methods Ten to twelve trees for each tree species were sampled for E_s and stem temperature at 1 cm depth beneath the bark (T_s) measurements in situ with an infrared gas analyzer (LI-6400 IRGA) and a digital thermometer, respectively, from July to October 2013 and March to July 2014. The daily stem circumference increment (S_i), sapwood nitrogen concentration ([N]), and related environmental factors were monitored simultaneously.
Important findings The temporal variation in E_s for the four tree species overall followed the changes in T_s throughout the study period, with the maxima occurring in the summer months (late May to early July) characterized by higher temperature and more rapid stem growth and the minima in spring (late March to April) or autumn (October) having lower temperature. T_s accounted for 42%-91% and 56%-89% of variations in E_s during the growing (May to September) and non-growing (other months) seasons, respectively. Furthermore, apart from T_s, we also found significant regression relationships between E_s and S_i, relative air humidity and [N] during the growing season, but their forms and correlation coefficients were species-dependent. These results indicated that T_s was the dominant environmental factor affecting seasonal variations in E_s, but the magnitude of the effect varied with tree species and growth rhythm. Mean E_s for each of the four tree species was significantly higher in the growing season than in the non-growing season, whereas within the season there were also significant differences in mean E_s among the tree species (all p < 0.05). The temperature sensitivity of E_s (Q₁₀ value) did not differ significantly among the tree species during the growing season, ranging from 1.64 for Dahurian larch to 2.09 for Mongolian pine, but did differ during the non-growing season which varied from 1.80 for Korean pine to 3.14 for Dahurian larch. Moreover, Korean spruce, Mongolian pine and Dahurian larch had significantly greater Q₁₀ values in the non-growing season than in the growing season (p < 0.05). These findings suggested that the differences of the response of E_s to temperature change for different tree species were mainly from the non-growing season. Because the seasonality and inter-specific variability in E_s for these temperate coniferous tree species were primarily controlled by multiple factors such as temperature, we conclude that using a single annual temperature response curve to estimate the annual E_s may lead to more uncertainty.     

Leaf decomposition and nutrient release of dominant species in the forest and lake in the Jiuzhaigou National Nature Reserve,China

AimsLitter decomposition is an important ecological process in nutrient cycling and productivity of ecosystems. Our objective is to quantify the differences of litter decomposition and nutrient release (N and P) under the forest and in an alpine lake among the dominant tree species in the Jiuzhaigou National Nature Reserve.
Methods Fresh leaf litters of Abies ernestii, Pinus tabulaeformis, Betula albo-sinensis, and Salix cupularis were collected and placed in bags under the forest and in an alpine lake for a year.
Important findings The mass remaining ratio (MR) of the leaf litters was well predicted with Olson’s decay model (r > 0.93, p < 0.01). The time for 99% decomposition was the shortest for S. cupularis (6.80 a), followed by B. albo-sinensis (10.34 a), A. ernestii (18.88 a), and P. tabulaeformis (27.21 a). These values were 1.48-, 1.55-, 1.80-, and 1.65-folds of the corresponding values in the lake, respectively. Both MR and nitrogen remaining ratio (NR) had significantly negative correlations with the leaf initial N concentration, but significantly positive correlations with the initial C:N. The nutrient release was significantly different among the four species and between the two sites (i.e., forest and alpine lake). The N release of S. cupularis was consistent between forest and the lake (i.e. directly released in the beginning of decomposition), while other species had an obvious N enrichment process before it released. The release of P among was similar among the four species and between the two sites, with a release—enrichment—release pattern. Overall, the leaf litter decomposition appeared as an intricate process that was affected by the litter chemistry and and the environment. The fast litter decomposition in the lake may have a profound influence on the water quanlity in the Jiuzhaigou National Nature Reserve.     

Carbon storage and potentials of the broad-leaved forest in alpine region of the Qinghai- Xizang Plateau,China

Aims
Our objective was to explore the vegetation carbon storages and their variations in the broad-leaved forests in the alpine region of the Qinghai-Xizang Plateau that includes Qinghai Province and Xizang Autonomous Region.
Methods
Based on forest resource inventory data and field sampling, this paper studied the carbon storage, its sequestration rate, and the potentials in the broad-leaved forests in the alpine region of the Qinghai-Xizang Plateau.
Important findings
The vegetation carbon storage in the broad-leaved forest accounted for 310.70 Tg in 2011, with the highest value in the broad-leaved mixed forest and the lowest in Populus forest among the six broad-leaved forests that include Quercus, Betula, Populus, other hard broad-leaved species, other soft broad-leaved species, and the broadleaved mixed forest. The carbon density of the broad-leaved forest was 89.04 Mg·hm^-2, with the highest value in other hard broad-leaved species forest and the lowest in other soft broad-leaved species forest. The carbon storage and carbon density in different layers of the forests followed a sequence of overstory layer > understory layer > litter layer > grass layer > dead wood layer, which all increased with forest age. In addition, the carbon storage of broad-leaved forest increased from 304.26 Tg in 2001 to 310.70 Tg in 2011. The mean annual carbon sequestration and its rate were 0.64 Tg·a^-1 and 0.19 Mg·hm^-2·a^-1, respectively. The maximum and minimum of the carbon sequestration rate were respectively found in other soft broad-leaved species forest and other hard broad-leaved species forest, with the highest value in the mature forest and the lowest in the young forest. Moreover, the carbon sequestration potential in the tree layer of broad-leaved forest reached 19.09 Mg·hm^-2 in 2011, with the highest value found in Quercus forest and the lowest in Betula forest. The carbon storage increased gradually during three inventory periods, indicating that the broad-leaved forest was well protected to maintain a healthy growth by the forest protection project of Qinghai Province and Xizang Autonomous Region.     

阿克苏市5种常见绿化树种滞尘规律

绿化树种在截留沙尘、降低大气颗粒污染物浓度、改善城市生态环境等方面发挥着不可替代的作用。该文选取新疆南部典型绿洲城市——阿克苏市不同功能区的绿化树种, 用多重比较法对比分析了二球悬铃木(Platanus × acerifolia)、新疆杨(Populus alba var. pyramidalis)、圆冠榆(Ulmus densa)、天山梣(Fraxinus sogdiana)和垂柳(Salix babylonica) 5个树种叶片平均滞尘量随时间变化及不同高度叶片的滞尘能力, 探讨了阿克苏市主要绿化树种的滞尘规律, 得出以下结论: 不同绿化树种单位叶面积滞尘量差异显著, 差距在1.15-2.17倍之间, 绿化树种滞尘量随着时间延长而增加; 同一树种在城市不同功能区的滞尘能力不同: 工业区>交通枢纽区>居民区>清洁区; 不同高度的叶片, 其滞尘量在工业区和交通枢纽区差异显著: 高度1 m的叶片滞尘量>高度2 m的叶片滞尘量>高度4 m的叶片滞尘量。     

亚热带不同树种凋落叶分解对氮添加的响应

为探究不同质量凋落物对氮(N)沉降的响应, 该研究采用尼龙网袋分解法, 在亚热带福建三明格氏栲(Castanopsis kawakamii)自然保护区的米槠(Castanopsis carlesii)天然林, 选取4种本区常见的具有不同初始化学性质的树种凋落叶进行模拟N沉降(N添加)分解实验(施N水平为对照0和50 kg·hm ^-2·a ^-1)。研究结果表明: 在2年的分解期内, 对照处理的各树种凋落叶的分解速率依次为观光木(Michelia odora, 0.557 a ^-1)、米槠(0.440 a ^-1)、台湾相思(Acacia confusa, 0.357 a ^-1)、杉木(Cunninghamia lanceolata, 0.354 a ^-1); N添加处理凋落叶分解速率依次为观光木(0.447 a ^-1)、米槠(0.354 a ^-1)、杉木(0.291 a ^-1)、台湾相思(0.230 a ^-1), 除杉木凋落叶外, N添加显著降低了其他3种凋落叶分解速率。N添加不仅使4种树木凋落叶分解过程中的N释放减慢, 同时还抑制凋落叶化学组成中木质素和纤维素的降解; N添加在凋落叶分解过程中总体上提高β-葡萄糖苷酶(βG)和酸性磷酸酶活性, 对纤维素水解酶的活性影响不一致, 而降低β-N-乙酰氨基葡萄糖苷酶活性和酚氧化酶活性。凋落叶分解速率与凋落叶中的碳获取酶(βG)活性以及其化学组分中的可萃取物含量极显著正相关, 与初始碳浓度、纤维素和木质素含量极显著负相关, 与初始N含量没有显著相关性。凋落物类型和N添加的交互作用虽未影响干质量损失速率, 但对木质素和纤维素的降解具有显著效应。综上所述, 化学组分比初始N含量能更好地预测凋落叶分解速率, 而N添加主要通过抑制分解木质素的氧化酶(如PHO)来降低凋落叶分解速率。     

Morphological traits and physiological characteristics in drought tolerance in 20 shrub species on the Qinghai-Xizang Plateau

Aims Providing indispensably theoretical evidence for establishing indices of evaluation on drought tolerance in shrubs, and screening for tree species that are drought tolerant for afforestation in arid regions or for matching their characteristics with suitable habitat conditions are the key to vegetation restoration in the Qinghai-Xizang Plateau. However, these issues are not adequately addressed in recent research due to lack of systematic methods. Therefore, our objective was to make a comprehensive evaluation on drought tolerance in 20 shrub species collected from different areas in Qinghai-Xizang Plateau, and to study their underlying mechanisms in drought tolerance.
Methods We made measurements on variables depicting root characteristics, including the root length (TRL), surface area (TRSA), volume (TRV), and tips number (TRTN) of all roots, the root length (FRL), surface area (FRSA), volume (FRV), and tips number (FRTN) of fine roots (d≤2 mm), and derived plant characteristic indices including thickness of cuticle (CT), thickness of palisade tissue (TPT), thickness of spongy tissue (TST), TPT/TST, thickness of leaf (LT), palisable tissue cell density, and tissue structural tense ratio (CTR = TPT/LT × 100%) and spongy tissue loosened ratio (SR = TST/LT × 100%) of leaf anatomical structure, root to shoot ratio (RSR), leaf transpiration rate (T_r), instantaneous water use efficiency (WUE_i), and carbon isotopic composition (δ¹³C) of the 20 shrub species through field experiments. Correlation analysis and principal component analysis were performed on the 19 variables and indices.
Important findings Different shrubs had different mechanisms of drought tolerance. In this study, the character- istics of drought tolerance were mainly categorized into 6 types, involving modifications of (1) root systems, (2) leaf anatomical structure, (3) leaf pattern, and (4) biomass allocation, or via (5) low water-consumption and (6) high WUE_i. Different genera or different tree species within the same genus clearly differed in drought tolerance. The species of the genus Hippophae were relatively poorly tolerant to drought, whereas several shrubs including Potentilla fruticosa, Berberis julianae, Caragana arborescens, Spiraea salicifolia and Hippophae rhamnoides ssp. mongolica occurred to be more drought tolerant than other shrub species investigated in this study. On the other hand, there were highly significant correlations among the characteristics of root systems and among characteristics of leaf anatomical structure. The results of principal component analysis on 19 variables and indices showed that TRL, TRSA, TRV, TRTN, FRL, FRSA, FRV, FRTN, CT, TPT, TST and WUE_i could be effective indicators of drought tolerance of shrubs in the Qinghai-Xizang Plateau. In addition, the drought tolerance of shrubs had a close connection with their origin of collections; the shrubs collected from Xining prefecture in Qinghai Province were more drought tolerant than those from Tianshui Prefecture in Gansu and Lasa Prefecture in Xizang.     

Plant diversity and seasonal dynamics in forest gaps of varying sizes in Pinus massoniana plantations

人工林目前存在结构单一、土壤退化、生物多样性降低等人类普遍关注的生态问题。马尾松(Pinus massoniana)是长江上游低山丘陵区退耕还林的主要人工林树种。研究采伐林窗对植物物种组成和更新的影响, 对马尾松低效人工林的改造, 提升其生态服务功能具有重要的意义。该文以采伐39年生的马尾松人工林形成的7种不同大小的林窗为研究对象, 分析了不同季节林窗内的植物生活型组成及多样性变化。结果表明: 1)马尾松人工林林下植物以高位芽植物居多, 其次是地面、地下芽植物, 一年生植物较少而缺少地上芽植物。在林窗形成初期, 林窗的高位芽植物比例明显低于林下, 大林窗的高位芽植物比例稍高于小林窗, 地下芽和一年生植物的比例低于小林窗。2)林下的物种丰富度和物种多样性指数显著低于大林窗。不同林窗下植物的丰富度指数、优势度指数、多样性指数也存在显著差异。3)夏季林窗下植物多样性最高, 其次是秋季, 春季多样性最低。1225-1600 m²的大林窗能够促进马尾松人工林植物多样性恢复和植被更新。     

Effects of a winter wildfire on plant community structure and forage quality in subalpine grassland of western Sichuan,China

火是继土壤、水分、温度之后, 塑造地表植被的主要力量。该文以2010年“12·5”冬草场火烧事件为背景, 通过对比川西亚高山草地火烧区域和未火烧区域火后第一年植被群落结构和牧草质量, 探讨亚高山草地植被对冬季火烧的响应机制。通过物种多样性分析、双向指示种分析(TWINSPAN)和干重等级法(dry-weight-rank)分析发现, 冬季火烧未改变植被的生物多样性、均匀度和物种丰富度, 却改变了植被群落结构的物种组成。冬季火烧导致一年生禾草、一年生杂草、灌木等3种生活型植物的数量和生物量增加; 多年生杂草数量减少, 生物量增加; 多年生禾草数量和生物量减少。冬季火烧也极大地减少了可食禾草的比例, 增加了各种杂草的生物量比例。此次火烧事件降低了细柄草(Capillipedium parviflorum)和早熟禾(Poa sp.)等可食禾草的竞争能力, 增加了一些杂草(如火绒草(Leontopodium leontopodioides)、白莲蒿(Artemisia sacrorum)、草玉梅(Anemone rivularis)等)在资源竞争中的相对优势, 最终表现为火后牧草的可食性下降。     

Early responses of vegetation and soil organic carbon to waterlogging and winter wildfire on abandoned red paddy soils

为了探明积水和冬季火烧对弃耕红壤稻田地表植被和土壤有机碳的影响, 该实验设置了对照(无人为干扰)、积水、冬季火烧和积水-冬季火烧4个不同处理, 采用样方法对样地植物的高度、密度、盖度及物种组成进行了调查。地上部分生物量采用收获法进行测定, 根系采用土柱法获取, 弃耕前后土壤有机碳含量的测定采用K₂Cr₂O₇外加热法。结果表明: 1)积水和冬季火烧对红壤稻田弃耕早期物种组成、丰富度、均匀度及多样性具有重要的影响。双穗雀稗(Paspalum paspaloides)和水竹叶(Murdannia triquetra)是积水条件下的优势种, 而柔枝莠竹(Microstegium vimineum)是冬季火烧条件下的优势种, 大狼杷草(Bidens frondosa)是积水和冬季火烧条件下的共优种。2)分布在0-5 cm表层土壤中的根系占0-20 cm深度土壤中根系的66.50%-80.34%。样地在积水条件下, 2011-2013年0-20 cm深度的土壤根系生物量分别高出对照样地的49.84%、73.34%和28.94%。3)冬季火烧可以提高样地的物种多样性和增加地上部分生物量, 2011-2013年冬季火烧样地分别高出对照样地的25.74%、64.30%和50.24%。4)与稻田弃耕前土壤有机碳含量逐渐上升趋势相反, 稻田弃耕6年后, 对照、积水、冬季火烧和积水-冬季火烧样地中土壤有机碳含量分别降低11.16%、18.99%、9.17%和19.12%, 并且在积水条件下土壤有机碳含量降低更明显(p < 0.05)。研究结果表明, 红壤稻田弃耕后地表植被物种组成、地上和地下生物量、土壤有机碳含量与积水和冬季火烧关系密切(p < 0.05)。     

2012年夏季长湖浮游植物群落特征及其与环境因子的关系

为查明长湖浮游植物群落特征及其水环境影响因子, 并确定水体富营养化程度, 于2012年夏季对长湖浮游植物及相关环境因子进行调查检测分析, 运用藻类生物学法和综合营养状态指数法, 对长湖水体营养状态进行综合评定, 同时利用典范对应分析法(CCA)对浮游植物与环境因子的关系进行了分析。结果表明, 2012年夏季长湖浮游植物共有53种(含变种、变型), 隶属于7门41属, 其中以绿藻最多(24种, 占总数量的38.9%), 其次为蓝藻(15种, 占总数量的36.0%)和硅藻(7种, 占总数量的14.1%)。优势种(优势度指数大于0.02)共10种, 其中两栖颤藻(Oscillatoria amphibia)是4个区域的共有优势种, 最高优势度达0.72。浮游植物丰度为12.03 × 10 ⁶- 62.13 × 10 ⁶cell·L ^-1, 平均值为27.71 × 10 ⁶cell·L ^-1。浮游植物丰度的平面分布呈现圆心湖、海子湖、马洪台、庙湖依次降低的特点。浮游植物多样性指数变化范围为0.89-3.24, 均匀度指数变化范围为0.23-0.83。选取叶绿素a、总磷、总氮、透明度和化学需氧量5项参数计算得出综合营养化指数。通过藻类生物学法和综合营养状态指数法进行综合评价发现: 2012年夏季长湖处于中度富营养化到富营养化程度。典范对应分析表明: 浮游植物空间分布主要受总氮、总悬浮物、总磷、溶氧以及亚硝酸氮等环境因子的影响。针状蓝纤维藻(Dactylococcopsis acicularis)、两栖颤藻、席藻属(Phormidium)、鱼腥藻属(Anabeana)等蓝藻对总氮的需求较大。长湖各站点由于在不同程度上受到地形、人为干扰以及水动力条件的影响, 它们与环境因子的典范对应分析表现出明显的区域性。     

Effects of methyl viologen on the antioxidant system in cultured Salvia miltiorrhiza cells

为了探讨甲基紫精(MV)对丹参(Salvia miltiorrhiza)体内抗氧化防护系统的影响及其生理机制。以MV为诱导剂, 以敌草隆(DCMU)为抑制剂, 考察了MV与DCMU处理后丹参悬浮培养细胞中H₂O₂、丙二醛、还原型谷胱甘肽的含量以及抗氧化防护酶(超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT))活性变化和同工酶的表达差异。结果表明, MV处理显著提高了丹参培养细胞内H₂O₂、丙二醛以及还原型谷胱甘肽含量; MV处理使CAT、POD活性增强, 谱带颜色更亮, 条带增加。DCMU处理显著抑制了MV诱导的H₂O₂、丙二醛、还原型谷胱甘肽含量的增加, 抗氧化酶活性的升高和同工酶的表达。以上结果说明, MV可诱导丹参培养细胞叶绿体产生H₂O₂, H₂O₂激活了丹参培养细胞抗氧化防护系统以维持细胞正常的生理活动。     

Dominant species and ecosystem gas exchange in temperate grassland under different land use patterns

在内蒙古温带草原围封、放牧和割草3种处理下的样地内, 对生态系统尺度和大针茅(Stipa grandis)、冷蒿(Artemisia frigida)、羊草(Leymus chinensis) 3种优势种植物叶片尺度上的气体交换和水分关系进行了测定, 对比研究了植物碳水对环境的响应。结果表明, 在优势种单株尺度和生态系统尺度上, 大气-植被CO₂交换因草地利用方式的不同而具有不同的表现。在生态系统层面, 放牧样地的群落净CO₂气体交换量和总初级生产力都与围封样地和割草样地有差异, 群落总初级生产力受生态系统呼吸的影响。在放牧处理下, 群落净CO₂气体交换量日变化表现为生态系统对碳的吸收, 而围封和割草则以碳释放为主。单叶光合速率出现负值并随时间推移而恢复的现象, 应是植物对干旱高温、高光照的特殊反应。生态系统水分利用效率没有明显不同, 但各样地的蒸散能力有趋势上的变化; 对于同种植物, 放牧样地植物单叶水分利用效率的日变化波动幅度最大, 围封样地最小。     

Responses in allometric growth of two dominant species of subalpine meadow—Arundinella anomala and Miscanthus sinensis—to climate warming in Wugongshan Mountains,China

AimsArundinella anomala and Miscanthus sinensis are dominant species in the subalpine meadow of Wugongshan Mountains. Here we studied the effects of climate warming on allometric relationships among different growth components in the two species through simulated warming in natural habitat.
Methods The warming experiments were conducted with open-top chambers (OTCs) in natural habitat in a subalpine meadow community of Wugongshan Mountains. The two main Gramineae species, Arundinella anomala and Miscanthus sinensis, were selected as the study materials. Two sizes of OTCs were set up to create contrasting levels of warming (i.e. TD for low warming and TG for high warming). The morphological variables, such as the plant height and the basal diameter of shoots, were measured. Allometric analysis was conducted with the Smart Package in R software.
Important findings Significant or highly significant correlations and significant allometric relationships were found between and among growth components in both species. The allometry of the growth in most morphological features was strengthened and modified by simulated warming. Stem diameter and plant height, and spike length in A. anomala and M. sinensis changed from isometric to allometric following warming. The relationship The synchronized growth between stem diameter and spikelet in A. anomala was weakened, but their allometry was enhanced with increased warming. The allometric relationship between plant height and leaf length in A. anomala transformed into isometric growth, but it was in reversed pattern in M. sinensis. Warming promoted the plant height and leaf sheath length in A. anomala, whilst higher warming changed the growth relationship between plant height and leaf sheath length in M. sinensis. Similar allometric relationships among the leaf traits were observed, but warming did not significantly impact their allometric exponents. The results suggested that climate warming could have varied effects on different plants, and the differences are often related to the adaptability of plants.