不同坡位对火力楠生长的影响

对广东高明云勇林场的火力楠Michelia macclurei纯林及其混交林2004～2007年的生长状况进行调查。运用多重比较方法分析上、中、下坡位的火力楠地径、树高、冠幅。结果表明,4年间(林分当年至3年生)所有样地的火力楠幼树平均地径、树高和冠幅均有显著增长。坡位对火力楠的地径生长具有显著影响,各坡位的火力楠平均地径为上坡>中坡>下坡,而坡位对树高和冠幅的影响不明显。     

鼢鼠鼠丘不同坡位和坡向对植被恢复的影响

对高原鼢鼠鼠丘不同坡位和不同坡向的植被性状进行了连续3年的监测,对比分析了不同坡位和坡向对植被恢复的影响,并对其作用机理进行了初步探讨.结果表明:(1)物种数、盖度、多度等植被性状在丘体不同坡位和坡向间均存在一定程度的差异,证明丘体坡位和坡向是影响鼠丘植被恢复速率和植被性状的重要因素;(2)不同坡位植被恢复速率的顺序是:丘缘>丘腰>丘顶,造成这种差异的主要原因是微地形对土壤水肥条件和繁殖体源的影响;(3)不同坡向恢复速率的顺序是:西坡>北坡>东坡>南坡,造成这种差异的原因在很大程度上取决于微地貌对土壤肥力及光照资源的再分配.     

干热河谷区不同坡位土壤水分对降雨的响应特征

研究干热河谷地区土壤水分在降雨过程中的短时动态变化,有助于揭示该地区的土壤水文功能。本研究选取贵州花江干热河谷作为研究区,运用原位监测法,获取不同坡位的高频土壤水分监测数据,分析土壤水分对降雨的短时动态响应特征。结果表明: 在整个监测期间,无论是坡上还是坡中,研究区各层土壤水分均为中等变异水平(15.2%≤变异系数CV≤29.7%),坡上土壤水分的波动幅度(CV=21.1%)大于坡中(CV=19.1%),0～5 cm土层(CV=26.2%)大于20～40 cm土层(CV=16.5%)。与坡中相比,坡上土壤水分对降雨的响应速度更快,降雨对土壤水分的补给量大、补给速率快;坡上的土壤水分补给速率与消退速率之差(2.3%·h^-1)大于坡中(1.8%·h^-1)。随土层深度增加,下层土壤水分对降雨的响应早于或同步于上层,降雨对土壤水分的补给量减少、补给速率减慢,土壤水分的消退速率也减慢。与坡中相比,坡上土壤水分入渗能力更强,保水能力更优。干热河谷的微观环境和小气候影响土壤水分对降雨的响应特征,而岩-土界面优先流的快速补给则会加快下层土壤水分对降雨的响应速度,使得该地区的坡面更容易形成混合产流机制。     

不同坡位胡枝子光合特性及其影响因子研究

采用Li-6400光合分析仪,在自然条件下对不同坡位胡枝子叶片净光合速率(Pn)、蒸腾速率(Tr)及其相关环境因子的日进程进行了观测。结果表明:在5月份晴天条件下,不同坡位胡枝子叶片Pn、Tr日变化均呈单峰曲线,而水分利用效率(WUE)表现出早晚高、中午低的变化趋势。它们的叶片Pn峰值不同坡位均出现在11:00,而且上坡位峰值和日平均值略高于下坡位和平地(P>0.05);Tr峰值上坡位出现在11:00,下坡位和平地均出现在13:00,且上坡位峰值和日平均值显著低于下坡位和平地(P<0.01);上坡和平地WUE均在15:00达到最大值,但下坡位推迟到17:00,而且上坡位峰值和日平均值略高于下坡和平地(P>0.05)。胡枝子叶片Pn与PAR、Ca、RH等生态因子间的拟合方程分别为:Y上pn=-26.148 0.002 3xPAR 0.11xCa-0.84xRH,Y平pn=-19.148 0.001 9xPAR 0.106xCa 0.86xRH,Y下pn=-27.148 0.002xPAR-1.16xRH,其主要生态影响因子及其大小顺序为XPAR>XRH>XCa。研究发现,不同坡位胡枝子叶片主要光合指标日变化趋势相似,但其峰值出现时间和高低有别,其主要生态影响因子为光合有效辐射、大气相对湿度和大气二氧化碳浓度。     

三峡山地不同类型植被和坡位对土壤水文功能的影响

土壤层下渗和贮蓄水分的水文功能是森林保持水土、涵养水源的基础。以三峡山地大老岭林区为研究区,采集常绿林、落叶林和草地覆盖下不同坡位的原状土样,测定其饱和导水率和水分特征曲线,分析植被类型和坡位对土壤水分参数和库容的影响。结果表明:常绿林地的入渗性能最好,饱和导水率为7.80—322.81 cm/d,大于落叶林地(0.33—137.03 cm/d)和草地(0.84—115.80 cm/d);坡位间差异表现为上坡高于下坡。不同样地的饱和含水量差异较小,但毛管持水量和田间持水量差异明显,草地最大,为20.77%—50.39%;不同坡位比较表现为下坡高于上坡。不同样地土壤水库容量差异较大,由田间持水量得到的库容量占总库容量的百分比以草地最大(63.25%),其次是落叶林地,常绿林地最小;坡位上表现为下坡的田间持水库容大于上坡。饱和导水率与土壤总孔隙度、有机质含量呈显著正相关,与容重呈显著负相关;饱和含水量、毛管持水量、田间持水量均与土壤总孔隙度、有机质含量和粉粒含量呈显著正相关,与容重、砂粒含量呈显著负相关。综合以上,草地持水性能最强,利于保蓄水分,常绿林地最弱,更利于水分入渗,补给地下水,下坡位的持水性能强于上坡位。     

坡位对东灵山辽东栎林土壤微生物量的影响

土壤微生物量是陆地生态系统中的重要组成部分,在森林生态系统养分循环和能量转化中扮演着重要的角色。坡位作为重要的地形因子,会影响土壤微环境、土壤理化性质、地上植被的生长以及地下碳输入等,从而影响着土壤微生物量。以北京东灵山海拔1000—1800 m范围内分布的辽东栎林为研究对象,分析相同植被群落中坡位对土壤微生物量空间分布的影响。方差分析结果表明,土壤微生物量碳、氮在各坡位间均无显著差异(P>0.05),而土壤理化性质在各坡位间差异显著(P<0.05),其中,下坡位的土壤含水量、土壤有机碳、土壤全氮显著高于中坡位和上坡位。偏相关分析结果表明,土壤微生物量碳、氮与土壤含水量、土壤有机碳和土壤全氮显著正相关(P<0.05),与草本丰富度显著负相关(P<0.05)。进一步的通径分析结果表明,在上坡位和中坡位,土壤含水量和土壤有机碳是主要的影响因素;而在下坡位,草本丰富度对土壤微生物量的负作用凸显。不同坡位上影响因素的差异可能是导致土壤微生物量在不同坡位间无显著差异的原因。     

坡位对北京东灵山辽东栎林物种多度分布的影响

海拔与坡位是气象因子和立地因子的综合表现.坡位影响环境因子在空间上的分布状况,与海拔共同营造物种生存的小生境,形成群落多度格局.本文选用5个描述种-多度关系的生态位模型(断棍模型BSM、生态位优先占领模型NPM、生态位重叠模型ONM、随机分配模型RAM、优势优先模型DPM),对北京东灵山辽东栎林的乔、灌、草3个层沿海拔梯度分别在上、中、下坡位进行群落多度格局调查.结果表明:在乔木层,从低海拔到高海拔、从下坡位到上坡位,能很好地反应群落多度格局变异的模型有由RAM、NPM向DPM过渡的趋势;能很好地拟合灌木层群落多度格局的生态位模型依次是NPM、BSM、RAM,DPM在高海拔地段拟合的效果也很好;BSM在草本层的拟合效果最好,其次是NPM和ONM.协方差分析表明,海拔和坡位都没有对辽东栎林的群落多度格局产生显薯影响.     

不同坡位水曲柳木质部解剖特征及其与气候关系

随着气候变暖,东北地区暖干化加剧。为了解干旱胁迫对小兴安岭地区不同坡位水曲柳径向生长的影响,采用木材解剖学方法,分析了水曲柳木质部解剖特征对不同坡位水分变化的响应。结果表明: 上、下坡位水曲柳木质部解剖参数整体上变化趋势一致,导管数量呈线性分布,最大导管面积和总导管面积总体上呈对数分布,平均导管面积总体上呈偏正态分布。不同坡位多个解剖参数均存在显著差异,下坡位导管数量、导管面积总体上大于上坡位。大部分解剖参数与日积温呈显著正相关,但存在一定差异,上坡位水曲柳总导管面积与日均温呈正相关,导管数量、总导管面积与相对湿度呈正相关,相关性均大于下坡位。上坡位最小导管面积与日积温和相对湿度呈显著负相关;而下坡位,总导管面积与相对湿度呈显著正相关。气候暖干化会导致水曲柳导管面积和导管数量相对减少,但基本上不影响导管分布状况,上、下坡位导管分布基本一致。目前,气候暖干化未限制而是促进了水曲柳的径向生长。     

巨尾桉生长量与不同坡向、坡位关系的研究

对福建寿宁县3年生巨尾桉不同坡向、坡位与生长量的关系进行研究,通过对比分析,结果表明：不同坡向、坡位的生长量差异显著。阳坡能显著促进巨尾桉生长,不同坡位之间差异显著,阳坡中下部对生长最有利。     

毛红椿人工林树干液流动态变化对坡位的响应

2012年7-10月,采用液流测定系统监测了位于浙江省开化县的毛红椿人工林上下坡位的树干液流,并同步监测生态环境因子,分析了毛红椿人工林树干液流与土壤含水量、温度和水势等环境因子的关系.结果表明: 研究区上、下坡位树干液流日变化均呈典型的“昼高夜低”单峰曲线;下坡位毛红椿树干液流速率平均值显著高于上坡位;上坡位土壤温度显著高于下坡位,而下坡位土壤含水量和土壤水势显著高于上坡位;下坡位土壤含水量和土壤水势是影响毛红椿树干液流速率的主要因子,而上坡位土壤温度和土壤水势对毛红椿树干液流速率有较大影响.     

Effects of habitat feature,antenna position,movement, and fix interval on GPS radio collar performance in Mount Fuji,central Japan

The location performance of a global positioning system (GPS) collar was assessed for different habitats and geographical areas. We tested the effects of habitat features, antenna position, movement, and fix interval on location performance around Mount Fuji, a single peak surrounded by wide and flat areas. Fix rate decreased from 100% in open flat areas to 53% under sloped dense canopy. The openness (the actual available sky, i.e., the percentage of a radio collar exposed to the sky when part of the collar is blocked due to terrain and vegetation) and canopy closure affected location accuracy and most other performance parameters. All nine habitat features except for available sky (theoretical, due to terrain) influenced location time. Any combination of obstructions between collar and satellite decreased the available number of satellites, the fix rate, increased the location time, and resulted in poorer location (higher DOP, lower 3-D proportion, or greater location error). A horizontal antenna yielded poorer location performance than a vertical one in the forest but not in the open area. Location performance always decreased when moving in forest rather than in open areas. Location performance changed with fix interval. Sixty-minute intervals resulted in a longer location time and a lower DOP than 10-min intervals. Vegetation affected location performance more than topography in the Mount Fuji area. Factors that cause a longer location time will shorten battery life. We suggest that location frequency and duration employed for field research should be decided by considering the aim of the study and the effects of habitat features, animal activity, and fix interval on GPS performance and battery longevity. The strengthened effect of canopy closure during windy weather should be considered for forest-dwelling animals.     

Evaluation of integrating topographic wetness index with backscattering coefficient of TerraSAR-X image for soil moisture estimation in a mountainous region

The estimation of soil moisture by using the backscattering coefficient of radar in a mountainous region is a challenging task due to the complex topography, which impacts the distribution of soil moisture and changes the backscattering coefficient. Complicated terrain can disturb empirical moisture estimation models, thereby, the resulting estimates of soil moisture are very unlikely reliable. This article proposed an innovative way of integration of the topographic wetness index (TWI) and the backscattering coefficient of soil obtained from the TerraSAR-X image, which improves the accuracy of measurement of the soil moisture. The standard estimation error and the coefficient of determination from the model were used to evaluate the performance of TWI. Our results show that the standard estimation error was decreased from: (1) 4.0% to 3.3% cm³ cm⁻³ at a depth of 5 cm and (2) 4.5% to 3.9% cm³ cm⁻³ at a depth of 10 cm. The most reliable estimation was observed at a depth of 5 cm, when it was compared with those of 0–5 cm, 10 cm and 15 cm. The TWI from the digital elevation model (DEM) is useful as a constraint condition for modeling work. This article concludes that the integration of the backscattering coefficient of soil with TWI can significantly reduce the uncertainty in the estimation of soil moisture in a mountainous region.     

Fix Success and Accuracy of Global Positioning System Collars in Old-Growth Temperate Coniferous Forests

Abstract: Global Positioning System (GPS) telemetry is used extensively to study animal distribution and resource selection patterns but is susceptible to biases resulting from data omission and spatial inaccuracies. These data errors may cause misinterpretation of wildlife habitat selection or spatial use patterns. We used both stationary test collars and collared free-ranging American black bears (Ursus americanus) to quantify systemic data loss and location error of GPS telemetry in mountainous, old-growth temperate forests of Olympic National Park, Washington, USA. We developed predictive models of environmental factors that influence the probability of obtaining GPS locations and evaluated the ability of weighting factors derived from these models to mitigate data omission biases from collared bears. We also examined the effects of microhabitat on collar fix success rate and examined collar accuracy as related to elevation changes between successive fixes. The probability of collars successfully obtaining location fixes was positively associated with elevation and unobstructed satellite view and was negatively affected by the interaction of overstory canopy and satellite view. Test collars were 33% more successful at acquiring fixes than those on bears. Fix success rates of collared bears varied seasonally and diurnally. Application of weighting factors to individual collared bear fixes recouped only 6% of lost data and failed to reduce seasonal or diurnal variation in fix success, suggesting that variables not included in our model contributed to data loss. Test collars placed to mimic bear bedding sites received 16% fewer fixes than randomly placed collars, indicating that microhabitat selection may contribute to data loss for wildlife equipped with GPS collars. Horizontal collar errors of >800 m occurred when elevation changes between successive fixes were >400 m. We conclude that significant limitations remain in accounting for data loss and error inherent in using GPS telemetry in coniferous forest ecosystems and that, at present, resource selection patterns of large mammals derived from GPS telemetry should be interpreted cautiously.     

The effect of inflorescence display size and flower position on pollination success in two deceptive and one rewarding orchid

• Inflorescence display size and flower position on the inflorescence play important roles in plant reproduction, in the formation of fruits and are primarily linked to pollinator behaviour. We used three orchids to determine how visitation rates and choice of pollinator depend on number and position of the flowers along the inflorescence.
• We measured reproductive success in (1) natural conditions, (2) hand-pollination experiments and (3) an experimental design, by modifying composition of inflorescences in populations of two deceptive orchids, Orchis anthropophora and O. italica, and one rewarding orchid, Anacamptis coriophora subsp. fragrans.
• There were no differences in natural fruit production in relation to flower position on the inflorescence (i.e. upper versus lower part), suggesting no preference of pollinators for different parts of the inflorescence. Hand-pollination experiments highlighted low pollen limitation in A. coriophora subsp. fragrans but high limitation in O. italica and O. anthropophora. Reproductive success of deceptive orchids in experimental plots decreased significantly when flowers on the upper half of the inflorescence were removed leading to reduced floral display, while reproductive success of the nectariferous species did not differ significantly.
• Our data highlight that in the examined orchids there is no clear relationship between fruit formation and flower position along inflorescences. Thus we can affirm that, for orchids, the entire inflorescence plays a dominant role in insect attraction but the part of the flower spike does not influence the choice of the insect. This implies that all flowers have the same possibility of receiving visits from pollinators, and therefore each flower has the same opportunity to set fruit.

     

Influence of age on reproductive performance in the Seychelles warbler

I studied age-related breeding performance of the cooperativelybreeding Seychelles warbler (Acrocephalus sechellensis) on CousinIsland, Seychelles, during 14 years. The annual number of youngthat fledged is significantly related to territory quality andnumber of helpers in the breeding group. Accounting for thesefactors and for the partner's breeding experience, annual productionof fledglings by breeding birds increases from 2 to 5 yearsand decreases beyond 5 years of age. Age-related changes inreproductive success within breeding individuals, paired withthe same experienced partner and occupying the same breedingterritory with similar amount of food from 2 to 8 years of age,show that Seychelles warblers have higher hatching success andproduce more hatchlings and fledglings as they become older.This is probably not a response to decreasing residual reproductivevalue caused by decreasing life expectancy as they become older.Primiparous warblers produce the same number of fledglings asmultiparous warblers of the same age, have a similar life expectancyas multiparous warblers, and occupy territories with similaramounts of resources available for reproduction. As all warblershave similar access to food before reproduction and similarforaging efficiency, the low reproductive success in youngerwarblers cannot be ascribed to differences in environment butto the bird's ability to breed successfully (e.g., a resultof previous helping and/or breeding experience). Effects ofsenescence on reproduction begin to occur from age 6 for bothsexes. From that age, eggs have lower hatching success, butfledging success remains the same. Birds that start breedingat a young age on a given quality territory produce more fledglingsin their lifetime than birds that delay breeding. Many old birdsnever fledge young of their own. They have not been able tobreed because of a shortage of breeding territory vacancies.[BehavEcol 7: 417–425 (1996)]     

2D与3D景观指数测定山区植被景观格局变化对比分析

植被和土地覆盖变化是环境变化的一个重要因素,同时也是引起景观和生态系统变化的重要原因。景观指数是定量分析植被和土地覆盖变化的重要研究方法之一。以滇西北高山峡谷区为案例区,比较分析传统2D景观指数和3D景观指数进行植被变化定量测定的差异。研究主要选取了基于斑块面积和周长几个常用指数来进行比较分析。研究结果表明在斑块层次上,除了分维数指数,其他指数的三维方法计算值显著地高于二维方法计算值;在类型层次上,三维的类型面积指数、平均斑块面积指数、平均最小邻近距离指数测定的变化值显著大于二维的相应指数测定变化值,但是二维和三维平均形状指数和分维指数测定的植被斑块的平均形状变化结果没有显著差异;在景观层次,只有三维的平均斑块面积和最小邻近距离指数测定的变化结果显著高于二维的平均面积和最小邻近距离指数测定的变化结果,其它指数如形状指数、分维指数、多样性指数和均一度指数等测定出两个不同时期的植被图格局变化结果均无显著差异,主要由于这些指数是采用面积和周长的对数或者比值计算得出,从而缩小了斑块表面面积与平面面积,表面周长与平面周长之间的差异。总体而言,利用二维景观指数在进行定量分析山区植被格局变化时,往往低估了其类型面积、平均斑块面积、斑块邻近距离等指数变化量,而三维景观指数得到相对较精确的变化值。