The storage and utilization of carbohydrates in response to elevation mediated by tree organs in subtropical evergreen broad-leaved forests

Global climate change can affect tree growth and carbon sink function by influencing plant carbohydrate synthesis and utilization,while elevation can be used as an ideal setting under natural conditions to simulate climate change effects.The effect of elevation on tree growth may depend on organ type.However,the allocation patterns of nonstructural and structural carbohydrates(NSCs and SCs,respectively)in different tree organs and their response to elevation remain unclear.We selected four dominant tree species,Schima superba,Castanopsis eyrei,Castanopsis fargesii and Michelia maudiae,along an elevation gradient from 609 to 1,207 m in subtropical evergreen broad-leaved forests and analyzed leaf,trunk,and fine root NSCs,carbon(C),nitrogen(N)and phosphorus(P)concentrations and the relative abundance of SCs.Leaf NSCs increased initially and then decreased,and trunk NSCs increased with increasing elevation.However,root NSCs decreased with increasing elevation.The relative abundance of SCs in leaves and trunks decreased,while the relative abundance of root SCs increased with increasing elevation.No significant correlations between SCs and NSCs in leaves were detected,while there were negative correlations between SCs and NSCs in trunks,roots,and all organs.Hierarchical partitioning analysis indicated that plant C/N and C/P were the main predictors of changes in SCs and NSCs.Our results suggest that tree organs have divergent responses to elevation and that increasing elevation will inhibit the aboveground part growth and enhance the root growth of trees.A tradeoff between the C distribution used for growth and storage was confirmed along the elevation gradient,which is mainly manifested in the"sink"organs of NSCs.Our results provide insight into tree growth in the context of global climate change scenarios in subtropical forest ecosystems.

Community ecology and spatial distribution of trees in a tropical wet evergreen forest in Kaptai national park in Chittagong Hill Tracts, Bangladesh

We investigated the floristic composition, woody species diversity and spatial distribution of trees in a tropical wet evergreen forest in Kaptai national park in Chittagong Hill Tracks, Bangladesh. We recorded 25 families, 37 genera, 40 species and 1771 woody individuals in a 0.09 ha plot. Euphorbiaceae and Moraceae were the most species- rich families, and Castanopsis, Ficus and Terminaliawere the most species-rich genera. Bursera serrata Wall. ex Colebr. was the dominant species in terms of highest importance value （13%）. Trema orientalis （L.） B1 was typically a light demanding species as it appeared in the top can- opy with only one individual having the seventh highest IV, but had no regeneration. The expected maximum number of species （Smax） was 140, indicating that many species may invade the forest as the Sm~ is greater than the recorded total number of species. The nature of the disappear- ance and appearance of species in the present forest reflects instability of floristic composition. The values of Shannon＇s index H＇ and Pielou＇s index J＇ （evenness） were 3.36 bit and 0.63, respectively. These values show moderately high species diversity as compared to other subtropical forests in the tropics. In addition, a sample area of 200 m2 in this forest would be sufficient for measuring the diversity indices H＂ and ,/＇, whereas the trend of J＇may indicate the rate of equality of individuals among the different species decreased with increasing area. The distribu- tion pattern for the total stand was completely random. However, the dominant species showed aggregate distribution for small areas, but random distribution for large areas. The spatial association between species showed that the strongest positive interspecific association occurred between Streblus asper Lour. and Castanea indica Roxh. （09 = 0.51）. As a whole, most species were weakly associated with each other, of which 58% species associations were completely negative. The result of cluster analysis showed that species pairs were spatially independent at all or most small clusters; stands of species from all clusters are mosa- ics of complete habitat and pioneer habitat. All patches in this forest community have similar habitat and regeneration niches, which could be a phenomenon for a young growth forest. Thus, the existence of habitat and regeneration niches may be an important factor in the maintenance of diversity in this forest.

Structure and floristic composition of old-growth wet evergreen forests of Nelliampathy Hills, Southern Western Ghats

We analyze the structure and composition of old-growth wet evergreen forest of Nelliampathy hills, the chain of hills lying immediately south of Palghat Gap, in the southern Western Ghats of India. We sampled 30 plots of 0.1 ha each （50 m × 20 m） at six locations enumerating all plants ？ 10 cm girth at breast height. We pooled the data and computed various structural parameters. There were 152 species of 120 genera and 51 families of the study area. Of these, 118 （77%） were trees, 24 were climbers （16%） and 10 were shrubs （7%）. Species richness varied from 58–99 per 0.5 ha sample and Shannon indices of diversity ranged from 4.4 to 5.2. Fifty-nine per cent （89 species） of the species were Indian Sub-continent elements and 34% （51 species） are endemic to the Western Ghats. Fifteen species are listed in various threat categories. Aglaia and Litsea were the most species-rich genera. Numbers of families ranged from 27–43 per 0.5 ha sample. Euphorbiaceae and Lauraceae were the most species-rich families. Stand density varied from 1714 to 2244 stems·ha？1 and basal area from 53.6 to 102.1 m2·ha？1. The vegetation was dominated by 3–6 species and six dominance patterns characterized the species composition within the hill complex. The old-growth evergreen forests of Nelliampathy exist as small fragments rich in biodiversity and can be used as benchmarks for comparison with disturbed forests.

Low net primary productivity of dominant tree species in a karst forest, southwestern China： first evidences from tree ring width and girth increment

Aboveground net primary productivity(ANPP)of two dominant species, one deciduous tree(Platycarya strobilacea) and one evergreen tree(Machilus cavaleriei),was estimated based on the tree-ring width and the girth increment as well as allometric functions in a karst evergreen and deciduous broadleaved mixed forest in central Guizhou Province, southwestern China. Results showed that the ANPP increased from 1961 to 2015, especially during the last 20–30 years, but with strong variations. The deciduous tree had higher ANPP than the evergreen tree according to two kinds of estimates by the tree ring and girth increment. The averaged ANPP for these two mature trees was 2.27 kg/individual/year, ca. 8 t/ha/year considering the normal stand density. Such karst forest productivity was lower than the natural subtropical forests in China and in the world.

Tree species diversity and utilities in a contracting lowland hillside rainforest fragment in Central Vietnam

Background： Within the highly bio-diverse ‘Northern Vietnam Lowland Rain Forests Ecoregion＇ only small, and mostly highly modified forestlands persist within vast exotic-species plantations. The aim of this study was to elucidate vegetation patterns of a secondary hillside rainforest remnant（elevation 120–330 m, 76 ha） as an outcome of natural processes, and anthropogenic processes linked to changing forest values.Methods： In the rainforest remnant tree species and various bio-physical parameters（relating to soils and terrain）were surveyed on forty 20 m × 20 m sized plots. The forest＇s vegetation patterns and tree diversity were analysed using dendrograms, canonical correspondence analysis, and other statistical tools.Results： Forest tree species richness was high（172 in the survey, 94 per hectare）, including many endemic species（〉16%; some recently described）. Vegetation patterns and diversity were largely explained by topography, with colline/sub-montane species present mainly along hillside ridges, and lowland/humid-tropical species predominant on lower slopes. Scarcity of high-value timber species reflected past logging, whereas abundance of light-demanding species, and species valued for fruits, provided evidence of human-aided forest restoration and ‘enrichment＇ in terms of useful trees. Exhaustion of sought-after forest products, and decreasing appreciation of non-wood products concurred with further encroachment of exotic plantations in between 2010 and 2015. Regeneration of rare tree species was reduced probably due to forest isolation.Conclusions： Despite long-term anthropogenic influences, remnant forests in the lowlands of Vietnam can harbor high plant biodiversity, including many endangered species. Various successive future changes（vanishing species, generalist dominance, and associated forest structural-qualitative changes） are, however, expected to occur in smal forest fragments.Lowland forest biodiversity can only be maintained if forest fragments maintain a certain size and/or are connected via corridors to larger forest networks. Preservation of the forests may be fostered using new economic incentive schemes.

The arbuscular mycorrhizal fungi status of selected tree nurseries in the Ethiopian highlands

We investigated the arbuscular mycorrhizal fungi(AMF)status of ten nurseries suitable for restoration of dry evergreen Afromontane forests in Ethiopia.We quantified AMF root colonization(RC)and spore abundance(SA)in seedlings of nine native tree species namely Acacia abyssinica Hochst.ex Benth.,Cordia africana Lam.,Dovyalis abyssinica(A.Rich.)Warb.,H agenia abyssinica J.F.Gmel.,Juniperus procera Hochst.ex Endl.,Millettia ferruginea(Hochst.)Baker,Olea europaea L.subsp.c uspidata(Wall.ex G.Don)Cif.,Podocarpus falcatus(Thunb.)R.Br.ex Mirb.and Prunus africana(Hook.f.)Kalkman.We used the ink and vinegar method to stain AMF in roots.RC levels ranged from 8.00 to 99.67%and were generally higher than the RC levels reported from other similar nurseries in Ethiopia.SA levels ranged from 1 to 25 spores g~(-1)and werecomparable with some reports from the field in Ethiopia but they were lower than levels reported by another similar study.RC was more affected by host species than nursery location,while the reverse was true for SA.The results also showed that nursery management could improve AMF status among seedlings.When all nursery tree species were considered,RC and SA levels were unrelated.No strong correlation existed between the nursery management variables considered and RC or SA.However,considering C.africana,J.procera and P.falcatus separately,RC-age(r_(s)=0.829,P=0.042)correlation for O.europaea and RC-pot diameter(r_(s)=0.820,P=0.046),RC-pot volume(r_(s)=0.928,P=0.008)and SA-age(r_(s)=0.943,P=0.005)correlations for C.africana,were significant,strong and positive.Generally,most of the tree species and particularly,early-mid successional tree species had sufficient AMF inoculum.Hence,only the mid-late successional tree species;J.procera,P.falcatus,and P.africana may require AMF inoculation,preferably,during filed planting.Based on our results,age and pot volume were identified to be important variables potentially affecting RC and SA.To better understand the effects of these and other nursery management variables,additional study is required.We demonstrated for the first time that black Hero ink is suitable for staining root AMF and can be used in future AMF research.

Species Composition and Stand Structure of Primary and Secondary Moist Evergreen Forests in the Tanintharyi Nature Reserve (TNR) Buffer Zone, Myanmar

The habitat structure and floristic composition examined for this study are of great importance, providing a scientific baseline of information for developing a biodiversity database and in supporting crucial information for the management decision-making process of the buffer zones. The primary objective of this study was to examine the current status of species composition and stand structure of moist evergreen forests distributed in the TNR buffer zone. Forest inventory was conducted in the primary moist evergreen forest (~1 ha) and secondary moist evergreen forest (~1 ha). In the TNR buffer zone, 83 species belonging to 31 families in the primary moist evergreen forest and 86 species belonging to 32 families in the secondary moist evergreen forest were found. The most dominant families in the primary moist evergreen forest were Dipterocarpaceae, Sapindaceae, Meliaceae, Myrtaceae, and Myristicaceae;at species level;this forest was composed of Nephelium lappaceum, Myristica malabarica, Nephelium laurium, Aglaia andamanica, and Diospyros peregrine. The most dominant families in the secondary moist evergreen forest were Myrtaceae, Sapindaceae, Euphorbiaceae, Myristicaceae, and Lauraceae, while Nephelium lappaceum, Syzygium claviflorum, Syzygium sp-1, Eugenia oblate, and Myristica angustifolia were the most dominant at the species level. The results of S?rensen’s similarity index based on common species (Ks) and the similarity index based on species dominance (Kd) were observed at about 55% and 75% between the primary and secondary moist evergreen forests. The basal area (51.39 m2.ha-1) of the primary moist evergreen forest was higher than that (44.50 m2.ha-1) of the secondary moist evergreen forest. Between these two forest types, the Shannon-Wiener, the Simpson and the Evenness indices were not significantly different at (p < 0.05). The total number of trees per hectare (n/ha) of the primary and secondary moist evergreen forests were 910 (±184) and 991 (±183). ?

东莞市亚热带常绿阔叶次生林优势种生态位特征研究

为了解广东省东莞市亚热带常绿阔叶次生林群落的生态位特征和演替现状,设置3个1 hm2样地,采用Levins生态位宽度和Pianka生态位重叠,对东莞市马山和银瓶山市级自然保护区的亚热带常绿阔叶次生林群落优势种进行生态位特征分析。结果表明,马山和银瓶山亚热带常绿阔叶次生林群落主要由樟科、芸香科、山茶科、鼠刺科、茜草科等树种组成。群落中山油柑(Acronychia pedunculata)、木荷(Shichima superb)、华润楠(Machilus chinensis)、黄樟(Cinnamomum parthenoxylon)、鼠刺(Itea chinensis)的生态位宽度较大,生态位宽度与频数关系密切。优势种生态位重叠值介于0~0.53,生态位重叠程度低,竞争关系较弱。3个样地所处演替阶段不同,银瓶山样地阳生树种与其他树种的生态位重叠值较大,马山样地中生性树种与其他树种的生态位重叠值更大,体现出常绿阔叶林从阳生树种建群到中生性树种建群的更替过程,为该区次生林的保护和管理提供科学依据。

镉对5种常绿树木若干生理生化特性的影响

研究了 5种常绿树木对镉污染胁迫的反应 ,实验结果表明 ,在高浓度镉胁迫下 ,5种树木叶片的叶绿素含量、细胞质膜透性、过氧化氢酶活性及镉富集量等生理生化特性均产生明显变化 ,但变化不尽一致。其中 ,黄杨、海桐 ,杉木抗镉污染能力优于香樟和冬青。

4种阔叶树种叶中氮和磷的季节动态及其转移(英文)

从叶完全展开到生长季结束 ,对常绿阔叶树种日本米槠 (Castanopsis cuspidata(Thunb.) Schottky)和具柄冬青 (Ilexpedunculosa Miq)及落叶阔叶树种栎 (Quercus serrata Murr.)和栓皮栎 (Quercus variabilis Blume)叶片的 N和 P浓度、含量和养分转移进行了测定 .在生长期中日本米槠新叶的 N浓度在 5月为 36 .6 g/ kg,然后降到 15 .5和 17.5 g/ kg之间 ,其老叶的N浓度波动于 10 .4和 13.1g/ kg的范围内 ,而具柄冬青新叶的 N浓度从 2 7.3下降到 16 .0 g/ kg,接着上升到 18.3g/ kg,其老叶的 N浓度在 12 .0到 15 .5 g/ kg的范围内。栎和栓皮栎的叶 N浓度分别从 2 8.8下降到 18.1g/ kg和从 2 8.5下降到17.5 g/ kg。日本米槠新叶的 N含量从 1.5 4下降到 1.35 g/ m2 ,接着上升到 1.5 0 g/ m2 ,其老叶 N含量从 1.36下降到1.0 0 g/ m2 ,接着上升到 1.2 1g/ m2 ,而具柄冬青新叶的 N含量从 2 .2 5下降到 1.6 0 g/ m2 ,接着上升到 2 .2 0 g/ m2 ,其老叶的 N含量从 2 .13下降到 1.6 5 g/ m2。栎和栓皮栎的叶 N含量分别从 2 .10下降到 1.2 8g/ m2和从 2 .95下降到 2 .13g/ m2。日本米槠新叶的 P浓度由 3.39g/ kg降到 1.12和 1.15 g/ kg之间 ,其老叶的 P浓度变化于 0 .6 6和 0 .88g/ kg的范围内 。

常绿树叶自然衰老的红外光谱研究

应用傅里叶变换红外光谱技术对七种常绿树的幼叶、成叶和老黄叶进行了研究,以期探讨常绿树叶自然衰老的光谱规律。不同时期叶片红外光谱变化主要在1 800～700cm-1范围,用吸光度比A1 070/A2 927和A1 070/A1 160考察叶样多糖相对含量变化,用A1 318/A2 922考察草酸钙相对含量变化,用1 800～1 500cm-1范围拟合峰的峰高比H1 650/H1 740考察蛋白质相对含量变化。结果显示在自然衰老过程中蛋白质、糖类、草酸钙相对含量有变化,但不同种树变化规律不同,说明不同种树叶衰老过程中物质积累、动员规律不同。证明中红外光谱可用于植物衰老生理变化的研究。

广西猫儿山不同海拔常绿和落叶树种的营养再吸收模式

土壤养分供给性大小是否影响植物氮和磷再吸收效率仍存在争议。调查了广西猫儿山不同海拔常绿和落叶树种成熟和衰老叶片的氮和磷含量,探讨营养再吸收是否受到叶片习性和海拔的影响。所有树种氮和磷再吸收效率的平均值分别为56.5%和52.1%。常绿树种比落叶树种有显著较高的氮再吸收效率(P<0.001)和磷再吸收效率(P<0.01),这与前者有较低的衰老叶片氮和磷含量密切相关。随着海拔的上升,氮再吸收效率显著下降(P<0.01),磷再吸收效率显著提高(P<0.05)。氮再吸收效率与土壤氮:磷比(r=-0.41,P<0.05)和成熟叶片氮:磷比(r=-0.37,P<0.05)负相关,磷再吸收效率与土壤氮:磷比(r=0.44,P<0.05)和成熟叶片氮:磷比(r=0.47,P<0.01)正相关,表明了树种对低海拔氮限制的适应逐渐转变为对高海拔磷限制的适应。此外,氮再吸收效率与年均温正相关(r=0.43,P<0.05)而磷再吸收效率与年均温负相关(r=-0.45,P<0.01),这表明气温也是调节树木营养再吸收格局的重要影响因素。不同海拔树种氮和磷再吸收模式的差异可能是引起广西猫儿山常绿树种沿海拔形成双峰分布的原因之一。

哀牢山中山湿性常绿阔叶林林窗更新研究

对云南哀牢山中山湿性常绿阔叶林林窗更新状况的调查结果表明,林内优势树种在林窗阶段不占优势,其在林窗内的重要值显著低于成熟林分;林窗内外的乔木幼苗在组成上存在较大差异,林窗内的幼苗多样性(H=2.73,D=0.89)高于林冠下(H=2.25,D=0.82),二者的Jaccard相似系数只有0.6,许多树种的幼苗只出现在林窗内;林窗内的乔木幼苗密度(38636株·hm^(-2))远远高于林冠下(17 323株·hm^(-2))林窗内和林冠下的乔木幼苗(H≤50cm)均以高度为11～20cm幼苗的在数量上占优势,但林窗内高度超过20 cm的幼苗比例明显高于林冠下;林窗大小对乔木幼苗更新有重要影响,不同树种的幼苗密度高峰出现在不同大小级别的林窗内。

哀牢山常绿阔叶林幼树C、N、P生态化学计量特征

研究了哀牢山中山湿性常绿阔叶林4种优势种幼树各器官中C、N、P化学计量特征,目的在于揭示不同物种生态适应特征及生态学意义。结果表明:上层树种腾冲栲、木果石栎和下层树种舟柄茶、红花木莲的幼树叶中具有较高的C质量分数,分别达到493.0、489.3、467.3、487.7 mg·g-1,且上层树种高于下层树种;4种幼树叶中的N和P质量分数与C质量分数有类似的特征,总体上看上层树种高于下层树种;4种幼树叶中的m(C)∶m(N)和m(C)∶m(P)分别为28.9、30.4、39.9、22.4和374.3、473.1、792.1、517.7,下层树种m(C)∶m(P)显著高于上层树种;m(N)∶m(P)以叶中的为最高,下层树种显著高于上层树种。下层树种幼树生长受P的限制较大,而上层树种幼树更加受N素的限制;上层树种在资源竞争中处于优势地位,而下层树种在养分资源的利用效率上更具优势。

重金属胁迫对5个常绿阔叶树种生理生化特性的影响

研究了不同浓度Cu-Zn-Pb-Cd复合重金属污染对木荷(Schima superba Gardn.)、香樟(Cinnamomum camphora Presl.)、青枫(Acer palmatum Thunb.)、苦槠(Castanopsis sclerophylla Schott.)和舟山新木姜子(Neolitsea sericea Koidz.)5个浙江地区常见种植的园林常绿阔叶树种抗氧化酶活性的影响。结果表明,高浓度复合污染显著抑制植物的生长,植物受害现象严重,中浓度次之,低浓度下大部分植物危害较轻。随着土壤中复合重金属浓度的增加,5种植物不同处理的叶绿素含量都降低,中、高浓度处理与对照相比均达显著水平(P<0.05)和极显著水平(P<0.01);其中在高浓度处理条件下,木荷下降最为显著,舟山新木姜子下降最小。5种植物不同处理的可溶性蛋白质含量与对照相比均不显著,但是丙二醛含量与对照相比均达显著水平(P<0.05)和极显著水平(P<0.01)。不同浓度处理下,SOD、POD和CAT的活性均呈现出先升后降的趋势,表明5种植物都具有一定的抗逆能力。在高浓度处理条件下,舟山新木姜子CAT、POD和SOD活性比对照下降最少,木荷下降最为显著。5种常绿阔叶树种对复合重金属胁迫的耐受能力依次为:舟山新木姜子>香樟>苦槠>青枫>木荷。

5个常绿园林树种的夏季光合蒸腾特性

【目的】分析5个园林常绿绿化树种的夏季光合蒸腾日变化特征及其与环境因子的关系,以进一步研究城市园林植物的生理生态学特性,探讨其对城市环境的适应性及配置合理性,同时评价其生态功能,为城市园林绿化树种的选择和养护提供科学理论依据,以进一步改善城市热岛效应。【方法】本研究在2013年7月21—23日夏季典型晴朗天气,以上海地区5个常用的常绿绿化树种石楠、广玉兰、蚊母、香樟、桂花为研究对象,采用LI-6400XT光合作用仪测定各个树种的光合蒸腾生理生态指标和主要环境因子,并分析其相关性。【结果】5个常绿树种夏季Pn(净光合速率)日变化均为双峰型,具有明显的"光合午休"现象,分析主要为非气孔限制所致。石楠、桂花、广玉兰和蚊母的Tr(净蒸腾速率)日变化均呈双峰曲线,香樟呈单峰曲线;石楠Pn和Tr日均值显著大于其他4个树种,蚊母最小。石楠和蚊母WUE(水分利用效率)日均值较高。根据蒸腾光合特性的影响因子相关性分析,Pn与Gs(气孔导度)、Ci(胞间CO2浓度)、Tl(叶片温度)、PAR(光合有效辐射)和Ta(空气温度)呈显著正相关性,与RH(相对湿度)呈显著负相关性;Tr与Gs,Ci,PAR,RH,VPD(水汽压亏缺)和WUE呈显著正相关性。【结论】广玉兰和蚊母蒸腾速率较小,日均光合速率较低;蚊母水分利用效率较高,广玉兰较低,建议养护中适当采取遮光措施减弱光抑制;香樟蒸腾速率较大,水分利用效率较低,建议养护中加强遮荫、灌溉以降低其蒸腾失水。在夏季,石楠、香樟和桂花抗强光、高温能力优于蚊母和广玉兰;石楠、蚊母能更有效利用土壤水分,适应较干燥的环境气候。

5个常绿阔叶园林树种对低温变化的生理响应

以南京地区引种的5个常绿阔叶园林树种为研究对象,探讨各树种叶片的膜透性、可溶性糖含量、POD酶活性、多胺含量等生理生化指标对低温变化的响应。结果表明:(1)在测定期内,除乐东拟单性木兰外,其余4个树种叶片的细胞膜透性均表现出先升高后降低再升高的变化趋势。浙江樟的质膜透性相对比较稳定,红花木莲变幅最大。(2)5个树种叶片可溶性糖含量,游离脯氨酸含量,叶片POD活性,腐胺(Put)、亚精胺(Spd)及精胺(Spm)含量与多胺总含量等均呈现先上升后下降趋势。(3)在最低气温到来前叶片可溶性糖含量调整到最大值;随低温时间延长和低温强度加剧各树种叶片中游离脯氨酸含量逐渐积累,变化幅度最大的是秃瓣杜英和乐东拟单性木兰;乐东拟单性木兰POD活性最大值出现较早且稳定,浙江樟POD活性较高且稳定,红花木莲与乐昌含笑的POD活性变化不稳定。(4)浙江樟和乐东拟单性木兰各月低温半致死温度(LT50)均较低。除浙江樟外,其他树种的LT50与采样前10天的日平均最低气温显著相关。(5)除乐昌含笑外,其他树种通过调节多胺含量适应外界低温变化。

济南市常绿阔叶树种的调查与应用

对济南市常绿阔叶树种资源现状进行了实地调查,结果表明:已有60多种常绿阔叶树种在济南市引种成功,但在生产中常绿阔叶树种应用较少。根据调查结果,作者为济南市常绿阔叶树种的引种与栽培、开发与利用等方面的研究提出了参考建议。

南亚热带常绿阔叶林不同大小和发育阶段林隙的树种多样性研究

分析了南亚热带常绿阔叶林不同大小和发育阶段林隙内树种多样性的变化规律 .结果表明 ,在南亚热带常绿阔叶林中 ,多样性指数在 <40 0m2 的林隙中变化不大 ,但在 40 0～ 5 0 0m2 的林隙中达到最大 ,而在 5 0 0～60 0m2 的林隙中最小 ,在 >60 0m2 的林隙中又有所增大 .树种多样性指数随林隙年龄的变化趋势是中间高两端低 ,即在 2 0～ 5 0年期间的多样性最大 ,其次是 2 0年以下的 ,5 0年以后的多样性相对最小 .林隙更新层中树种多样性指数在 5 0 0～ 60 0m2 的林隙中达到最大 ,在 >60 0m2 和 2 0 0～ 3 0 0m2 的林隙中最小 .林隙更新层树种多样性指数在林隙形成最初的 10年内达到最大值 ,但随着林隙年龄的增加 ,总体上表现出下降趋势 ,在 3 0～ 40年和 5 0～ 60年左右又分别形成两个相对的峰值 .物种丰富度的变化趋势总体上与树种多样性指数相一致 .不同大小和发育阶段的林隙通过其生态因子的改变 ,对不同树种的更新起到了不同的作用 ,从而使得不同大小和发育阶段的林隙中树种的多样性特征不同 .

庐山若干常绿树种对冬季低温的生理生化响应

为了探讨引种的珍贵树种对庐山冬季低温环境的适应性,以庐山植物园引种栽培的6种常绿园林树种即乐东拟单性木兰（Parakmeria Latungensis）、红花木莲（Manglietia insignis）、桂南木莲（Manglietia chingii）、四川含笑（Michelia szechuanica）、深山含笑（Michelia maudiae）和广玉兰（Magnolia grandiflora）为研究对象,以庐山乡土树种云锦杜鹃（Rhododendron fortunei）为对照,采集冬季不同时期的鲜叶样品,分析了7个树种叶片4个主要生理生化指标随气温变化而变化的特征,研究低温环境对这些树种生理生化过程的影响。结果表明：1）在冬季,大部分树种的可溶性糖含量呈现出与气温变化相反的趋势即先上升后下降,只有深山含笑在1月份,比上年12月份下降了7.54%,其他树种增加幅度处于11.56%~34.49%之间,而乐东拟单性木兰和广玉兰的可溶性糖含量呈现不断上升趋势。2）除桂南木莲和广玉兰外,可反映植物耐寒程度的丙二醛含量呈现不断上升的趋势,从上年12月份到当年1月份,上升幅度较大的有红花木莲、深山含笑和四川含笑,而从1月份到3月份,增加幅度较大的为广玉兰、桂南木莲、深山含笑和云锦杜鹃等树种。3）乐东拟单性木兰和深山含笑呈逐渐增加的趋势,而大部分树种的SOD活性都呈现与气温相似的变化趋势即先下降后上升的趋势;除了广玉兰的POD活性先上升后下降,其他树种则不断上升,但不同树种POD活性大小及变化幅度不尽相同,POD活性最高且变异性最大的是乐东拟单性木兰。4）单因素方差分析表明,可溶性糖含量和POD活性在不同温度下和不同树种间存在显著差异,丙二醛含量和SOD活性只在不同温度下存在显著差异,树种之间差异不明显。通过分析4个表征植物耐寒性的生化指标,显示出可溶性糖含量能够较客观地反映植物随着气温变化所发生的生理生化变化,可作为本地区植物耐寒性的一个重要指标。由于不同树种适应低温环境的生理生化机制存在差异,在选择表征植物耐寒性的生化指标时,应综合分析。