热带季节雨林林窗边缘不同热力作用面热力效应的季节变化特征

通过对热带季节雨林雾凉季和湿热季昼间林窗区域不同热力作用面的热力效应初步分析,指出在西双版纳,不论是雾凉季还是湿热季,热带季节雨林林窗边缘壁面均具有不可忽视的热力作用,且由于受林缘树木的影响,热力效应较强的东侧,北侧林缘壁面最大区域出现位置高于次生林林窗,而强度小于次生林林窗,显示了林窗边缘壁面的热力效应除与太阳高度角,太阳辐射的时间长短和强度有关之外,林窗边缘树木高度也是不可忽视的因子,其结果可为进一步研究林窗小气候形成机制提供研究基础,为研究林窗更新及生物多样性问题提供科学参考。     

西双版纳人工林林窗光照剖线分布特征

以林窗北缘为中心,研究了西双版纳地区橡胶林林窗及周边Ｎ－Ｓ样带上光照水平梯度分布。结果表明：林窗的发生导致光照明显增加,从林内到林窗中央,光强呈明显增大趋势,上午雾末消退时,相对光照强度水平梯度变化曲线峰值出现于林窗中央,午后雾消退后,林窗边缘为相对光强梯度变化最甚的地段,峰值由林窗中央向林窗北缘移进。林窗边缘,林窗中央及林内光照强度日变化曲线均为不对称的单峰型,但峰值出现和振幅不同。在太阳高度角     

西双版纳热带次生林林窗小气候要素的时空分布特征

利用西双版纳雾凉季和干热季热带次生林林窗的小气候垂直观测资料,探讨了昼间林窗区域树表温、气温、水汽压及相对湿度的时空分布和变化规律,指出在林窗区域,林窗边缘不仅具有显著的热力效应,同样具有明显的水汽效应。并由此构成了林窗区域立体空间的环境异质性,其结果对深入探讨林窗区域的热量、水汽传输,小气候的形成机制,生物多样性和更新等问题均具有重要意义。利用西双版纳雾凉季和干热季热带次生林林窗的小气候垂直观测资料,探讨了昼间林窗区域树表温、气温、水汽压及相对湿度的时空分布和变化规律,指出在林窗区域,林窗边缘不仅具有显著的热力效应,同样具有明显的水汽效应。并由此构成了林窗区域立体空间的环境异质性,其结果对深入探讨林窗区域的热量、水汽传输,小气候的形成机制,生物多样性和更新等问题均具有重要意义。     

西双版纳热带次生林林窗干热季气温分布特征的初步分析

利用西双版干热季次生林林窗的温度观测资料,探讨了林窗４方位的气温时空变化特征。由于林窗不同区域所受太阳辐射的影响不同,加之林缘热力效应的综合作用,林窗中存在明显的气温差异,特别是最高气温差异显著;气温最高值和气温日较差最大值不在林窗中央而出现在林窗东侧林缘树冠垂线处。     

热带次生林林窗不同热力作用面特征分析

利用热带次生林林窗边缘树表温和林窗区域地表温的观测资料,探讨了昼间林窗各热力作用面的热力效应及其变化规律,通过分析林窗边缘树表温和林窗地表温的变化,指出在林窗区域林窗边缘墙面是林冠面,林窗地面,林内地面之外的亲的第4热力作用面;各个热力作用面的热力效应随季节,位置和时刻的不同有着明显差异,在受浓雾影响的上午,林窗地面热力作用较强,在中午和下午林窗东侧林缘壁面,林窗东侧－东北侧地面的热力作用显著,中乖以林窗地面作用较强;而下午则以林窄边缘墙面作用较强,各个较力作用面的热力特征和相互作用将制约林窗的热力变化,影响植物的生长。     

干季晴天橡胶林林窗温度剖线分布特征

以林窗北侧林缘为中心,研究了西双版纳地区橡胶林林窗及周国Ｎ－Ｓ样带上气温水平梯度分布。结果表明：干季落叶期林窗及周边主要热力作用面在地面,但林缘的增温效应也相当明显,各热力作用面热量收支是林窗小气候形成的物理基础;林缘冠层结构,林缘乔木高度与林窗直径之比,太阳高度角,方位角,天气状况将影响林窗辐射平衡各分量的变化,林缘乔木群落结构的不同是造成林窗小气候差异最直接的原因;     

西双版纳干季晴天次生林林窗气温时空分布特征

利用西双版纳干季(12月、4月)次生林林窗的温度观测资料,探讨了晴天林窗4方位的气温的空气变化特征。由于林窗的不同位置所受太阳辐射的影响不同,加之林缘热力效应的综合作用,林窗中存在明显的气温差异,特别是最高气温差异显著;气温最高值和气温日较差最大值不在林窗中央而出现在林窗东侧林缘树冠垂线外。这势必造成林窗不同区域热量传输的不同,形成林窗小气候的差异。其结果可为进一步研究森林林窗小气候及有关生态学现象提供基础。     

西双版纳望天树林干热季不同林窗间的小气候差异

对西双版纳望天树林干热季不同林窗间的小气候差异进行了观测,对比分析了３个不同大小林窗（２００ｍ＾２、１４０ｍ＾２、６０ｍ＾２）内的温度、相对温度和光强分布状况及温度垂直分布形式。结果表明,各林窗内温度、温度日变化均比林内大,其中以大林窗最为明显,且最小林窗内的温湿度变化最为缓慢;林窗内的光照强度为林内的１０倍以上,大林窗中央地表温度及冠层０．５ｍ处气温、相对湿度日较差比最小林窗分别高１５．８℃、３     

川西亚高山森林林窗不同时期土壤转化酶和脲酶活性的特征

为了解川西亚高山森林林窗对不同时期土壤生态过程的影响,于2012年6月—2013年5月期间,根据温度动态过程,对比研究了生长季节(土壤完全融化期、生长季节前期和生长季节后期)与非生长季节(冻结初期、深冻期和融化期)川西亚高山粗枝云杉(Picea asperata)人工林林窗中心、林缘和林下土壤有机层和矿质土壤层转化酶和脲酶活性变化过程。结果表明:林窗不同区域中,土壤有机层转化酶活性均高于矿质土壤层;在生长季节,土壤有机层和矿质土转化酶活性表现为:林窗中心林下林缘,而脲酶活性表现为:林窗中心林缘林下。冻结初期和深冻期林窗中心土壤转化酶活性均高于林缘和林下,而在融化期林下转化酶活性高于林窗中心和林缘;冻结初期和融化期林下土壤脲酶活性显著高于林窗中心和林缘,而在深冻期林窗不同区域土壤脲酶活性没有显著差异。林窗不同区域在不同时期对土壤转化酶和脲酶活性的响应有着深刻影响。     

云南哀牢山常绿阔叶林林缘不同热力作用面热力特征

利用云南哀牢山原生的亚热带常绿阔叶林西南向边缘的表温观测资料,探讨了原生常绿阔叶林林缘区域不同热力作用面表温的水平、垂直分布特征及其差异。指出哀牢山原生的亚热带常绿阔叶林林缘与热带片断化季雨林林缘相同,其林缘壁面的热力效应同样是不可忽视的,在林缘区域构成了除了公认的林外地表面,林冠面和林内地表面3个热力作用面之外的一个新的第4热力作用面。对其进行深入研究,将有助于解释森林边缘的小气候效应和生物效应。     

Flowering phenology and reproductive success of native shrub Berberis darwinii Hook. along different light environments

Studies evaluating flowering phenology and reproductive success are necessary when we want to direct a domestication project in a species with a potential productive value. We studied flowering phenology and reproductive success of Berberis darwinii growing under different light conditions in its native distribution area in the Andean Patagonian forests of Argentina. We test the hypothesis that plants grown under conditions of high-light availability exhibit advanced phenology and higher reproductive success than those grown under conditions of lower light availability. Phenology and reproductive success were determined in three contrasting light conditions at two forest sites, which were, canopy, gap and forest edge. Plants did not bloom under the forest canopy. Flowering and fruiting period lengths were similar in both sites and light conditions of gap and forest edge during spring and summer. Although gap plants had more racemes per shoot, racemes of edge plants had more flowers, fruits and a higher proportion of flowers producing ripe fruit. We show that B. darwinii reproduction studied in the Andean Patagonian forests is conditioned by the canopy openness. Regarding reproductive success, edge plants invest less resources in flower production than gap plants to have similar fruit production.     

热带次生林森窗平均气温空间分布特征的初步分析

森林群落演替更新作为生态学研究的核心问题 ,一直是研究热点 ,而群落演替更新的重要生态动力乃是自然或人为的干扰。国内外关于大尺度干扰对不同森林类型演替更新已有较详细的研究 ;从 2 0世纪 80年代初开始 ,小尺度的林窗干扰开始受到广泛重视。由于林窗是群落演替的起始地 ,其大小和环境变化程度决定了林窗发展的方向和速度 ,并且林窗的更新状况直接影响到顶级森林的结构、种类组成和种群动态。对于世界范围内的各种森林类型的更新和演替均有重要作用 [17] ,而在热带雨林中的作用更加显著和重要[15] ,因此 ,国外学者十分重视林窗的研究。…     

The limited role of canopy gaps in the successional dynamics of a mature mixed Quercus forest remnant

Question: Are canopy gap dynamics responsible for driving the structural and compositional changes that have occurred over a 26‐year period in a mature Quercus forest remnant? Location: Dobbs Natural Area, an unlogged 3.6‐ha forest preserve in west‐central Indiana, USA. Methods: We analyzed mapped permanent plot data for a site that illustrates a trend common in Quercus‐dominated forests in eastern North America, where recruitment of new stems is dominated by mesophytic, shade‐tolerant species such as Acer saccharum, rather than Quercus. We developed a GIS database from stand census measurements taken in 1974 and 2000, employing it to conduct tree‐by‐tree comparisons that allow direct determination of ingrowth, mortality and survivorship, and to relate the spatial patterns of subcanopy dynamics to canopy gap occurrence. Results: The re‐census shows modest changes in canopy composition, but much greater turnover in the subcanopy. Nearly half of all individuals originally present died; much of this mortality resulted from a major decline in subcanopy Ulmus americana. While overall density remained fairly constant, the subcanopy experienced substantial ingrowth of shade‐tolerant Acer saccharum, Fagus grandifolia, and Tilia americana. Canopy gaps, although forming at rates in the upper range of regional averages, did not significantly benefit subcanopy populations of Quercus spp. or most other taxa with limited shade tolerance. Conclusions: Canopy gaps play a minor role in driving the recent demographic trends of this stand. The spatial and temporal scales of light availability in gaps do not support regeneration of most shade‐intolerant species. Compositional change parallels a historical shift in light regimes.     

东灵山地区辽东栎幼苗的建立和空间分布

研究树木实生苗的建立对森林生态系统的保育和恢复具有重要意义,在北京东灵山地区调查了辽东栎(Quercus liaotungensis)实生和萌生幼苗在几种典型的植被类型中的空间分布以及辽东栎一年生实生幼苗在1个林窗梯度上的建立。选择几种典型的植被类型,研究辽东栎实生幼苗和萌生幼苗在森林中的空间分布。结果显示,在不同植被类型中辽东栎实生和萌生幼苗的密度存在空间差异,实生苗密度随幼苗年龄增大逐渐降低,种群的更新主要依靠萌生苗完成。在1个落叶阔叶林中选择1个林窗,在不同梯度(即林窗中间、林窗和树冠连接处,以及树冠下)上,播种辽东栎坚果,第二年秋季调查实生幼苗的2个生长指标和出苗率。结果显示,林窗对一年生实生幼苗的生长高度有影响。幼苗高度在林窗中比在树冠下大;林窗对辽东栎幼苗最长叶片长度和幼苗的出苗率没有影响。说明辽东栎实生幼苗的良好生长需要阳光比较充足的生境条件。本项研究结果建议,对辽东栎种群的更新,应该适当择伐一些较大个体,使森林形成一些林窗或林中空地,以利于辽东栎实生幼苗的建立,这样才能使辽东栎种群通过实生苗进行更好的自然更新。     

热带季节雨林林窗辐射特征研究

利用不同季节热带季节雨林林窗、林内及旷地不同波长太阳辐射的实测资料,探讨了热带季节雨林林窗不同波长辐射特征。结果表明,热带季节雨林林窗中央和北侧林冠下的不同波长太阳辐射存在“突跃现象”,中午前后各辐射量值迅速达到最大后又急速下降;林窗内不同波长太阳辐射日总量值均大于林内,却小于旷地;林窗中央和北侧林冠下比较可见,在干热季、雨季和雨季后期,林窗中央的各辐射要素总量值高于北侧林冠下,但雾凉季时受浓雾和太阳高度以及方位的影响,各辐射要素总量值较北侧林冠下低;林窗中央的总辐射日总量在雨季太阳高度角最大时最高,雨季后期和干热季其次,雾凉季时最小;林窗中央和北侧林冠下的红外辐射及可见光在总辐射中所占份额随季节的变化而不同,充分显示了林窗辐射环境的异质性;与旷地和林内相比,林窗内各测点的红外辐射在总辐射中所占份额介于旷地和林内之间．高于旷地却低于林内;而可见光占总辐射的比值情况正好相反．另外,林窗可见光分配率的季节变化都大于红外辐射;热带季节雨林林窗育增加红外辐射、减少可见光的特征．     

Overstorey Control of Understorey Species Composition in a Near-natural Temperate Broadleaved Forest in Denmark

Little is known about the importance of the forest overstorey relative to other factors in controlling the spatial variability in understorey species composition in near-natural temperate broadleaved forests. We addressed this question for the 19 ha ancient forest Suserup Skov (55°22′ N, 11°34′ E) in Denmark, one of the few old-growth temperate broadleaved forest remnants in north-western Europe, by inventorying understorey species composition and environmental conditions in 163 100 m² plots. We use unconstrained and constrained ordinations, variation partitioning, and Indicator Species Analysis to provide a quantitative assessment of the importance of the forest overstorey in controlling understorey species composition. Comparison of the gradients extracted by unconstrained and constrained ordinations showed that the main gradients in understorey species composition in our old-growth temperate broadleaved forest remnant are not caused by variability in the forest overstorey, but are related to topography and soil, edge effects, and unknown broad-scale factors. Nevertheless, overstorey-related variables uniquely accounted for 15% of the total explained variation in understorey species composition, with the pure overstorey-related (R_po), topography and soil (R_pt), edge and anthropogenic disturbance effects (R_pa), and spatial (R_ps) variation fractions being of equal magnitude. The forward variable selection showed that among the overstorey-related variables understorey light availability and to a lesser extent vertical forest structure were most important for understorey species composition. No unique influence of overstorey tree species identity could be documented. There were many indicator species for high understorey light levels and canopy gap centres, but none for medium or low light or closed canopy. Hence, no understorey species behaved as obligate shade plants. Our study shows that, the forest overstorey has a weak control of understorey species composition in near-natural broadleaved forest, in contrast to results from natural and managed forests comprising both conifer and broadleaved species. Nevertheless, >20% of the understorey species found were indicators of high light conditions or canopy openings. Hence, variability in canopy structure and understorey light availability is important for maintaining understorey species diversity.     

Cultivation of Non‐timber Forest Products Alters Understory Light Availability in a Humid Tropical Forest in Mexico1

The planting of non‐timber forest products (NTFPs) in the understory of tropical forests is promoted in many regions as a strategy to conserve forested lands and meet the economic needs of rural communities. While the forest canopy is left intact in most understory plantations, much of the midstory and understory vegetation is removed in order to increase light availability for cultivated species. We assessed the extent to which the removal of vegetation in understory plantations of Chamaedorea hooperiana Hodel (Arecaceae) alters understory light conditions. We also examined how any changes in light availability may be reflected by changes in the composition of canopy tree seedlings regenerating in understory plantations. We employed a blocked design consisting of four C. hooperiana plantation sites; each site was paired with an adjacent, unmanaged forest site. Hemispherical canopy photographs were taken and canopy tree seedlings were identified and measured within 12 3 × 2 m randomly placed plots in each site for a total of 96 plots (4 blocks × 2 sites × 12 plots). Plantation management did not affect canopy openness or direct light availability but understory plantations had a higher frequency of plots with greater total and diffuse light availability than unmanaged forest. Comparisons of canopy tree seedling composition between understory plantations and unmanaged forest sites were less conclusive but suggest that management practices have the potential to increase the proportion of shade‐intolerant species of tree seedlings establishing in plantations. Given the importance of advanced regeneration in gap‐phase forest dynamics, these changes may have implications for future patterns of succession in the areas of forest where NTFPs are cultivated.     

香果树实生苗的光合特性及其与环境因子的关系

为确定香果树实生苗的适生环境并为其自然更新提出有针对性策略,研究了不同生境(冠下、冠缘、林窗和林缘)中2年生香果树实生苗的净光合速率、水分利用效率、叶绿素含量、苗高、基径、生物量等的变化及其与生态因子之间的关系.结果表明: 4种生境中的光合有效辐射最大值为50～1380 μmol·m^-2·s^-1,冠下和冠缘中香果树实生苗的净光合速率日变化呈单峰型,而林窗和林缘实生苗的净光合速率日变化呈双峰型;香果树实生苗为耐阴植物,但耐阴能力较弱,其功能叶的光饱和点、补偿点和暗呼吸在4种生境中大小顺序为: 林缘>林窗>冠缘>冠下,表观量子效率的变化规律与之相反;林窗和冠缘2种生境中香果树实生苗的适应能力较强,叶片的蒸腾速率、气孔导度、水分利用效率和净光合速率较高;林窗中香果树实生苗叶片的叶绿素含量较低,但实生苗的生长速度最快,生物量最大;香果树实生苗的净光合速率与光合有效辐射和气孔导度呈显著正相关.对于冠下生境,需降低林冠层密度,增加透光率,以利于香果树实生苗的光合作用;对于林缘生境,则需要增加植被盖度,降低光照强度,以利于其快速生长.