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.     

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。     

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.     

Effects of topographic position,leaf litter and seed size on seedling demography in a semi-deciduous tropical forest in Panamá

This study examined whether topography-induced gradients in water potential and leaf litter depth contribute to species coexistence in tropical forests through species-specific effects on seedling emergence and mortality. Seedling emergence and mortality were followed for a period of 12 months in 36 (1 × 2 m) plots on Barro Colorado Island (BCI), Panamá. Plots with and without litter were distributed on slope and plateau sites in three catchments. In the absence of manipulations, the lower litter depth on slopes resulted in approximately four times as many emergent seedlings than on plateau sites. However, litter depth had little effect on seedling community composition. By the end of the first dry-season, post-emergence, there were no significant differences in surviving seedling numbers between any treatments. There were differences in the emergent seedling community between slope and plateau sites within the same catchment as well as differences in composition between catchments, suggesting that both niche partitioning and dispersal limitation might play a role in structuring seedling community composition. During the wet-season seedling mortality was highest on slope sites although this pattern was reversed during the dry-season. In both seasons mortality was higher for small-seeded species. These results demonstrate that gradients in water potential related to topography impact on patterns of seedling emergence and mortality although processes in the first year after emergence may be insufficient to explain observed habitat preferences of adult plants.     

Estimation of Precision in DLW Studies Using the Two-Point Methodology

Previous attempts to estimate precision of doubly labeled water (DLW) estimates of CO₂ production, using propagation of error analyses, have necessarily made simplifying assumptions which may compromise the resultant error estimate. Using an empirical iteration approach, error distributions for the DLW calculation were generated which overcome these problems. The error distribution for CO₂ estimates generated by DLW is symmetrical but not normal. The distribution is significantly truncated such that the 99% inclusion limits are 2.034 SD and not 2.58 SD. The precision error (99% CI for mean as percent of the mean) in DLW experiments, when using duplicate analyses, varies between approximately 3% and 47% depending on the ratio of the elimination constants of the two labels (k_o/k_d), experimental duration and initial isotope dose. The error could be improved by approximately 10 fold by increasing the number of replicates at all six isotope determinations from 2 to 5. Estimating precision in actual experiments can be made using the same empirical approach. The resultant estimates can be of extreme value in evaluating the role of precision as a factor influencing deviations during validation studies, and also for weighting mean estimates in applications of the technique. The deviations of DLW estimates from those made simultaneously by indirect calorimetry in a small mammal validation study were generally greater than the precision of the DLW estimates of CO₂ production. This may indicate there are more problems with the technique than precision alone.     

木霉属补充DNA条形码筛选

木霉属真菌是一类重要的生物资源,在工农业、环境保护等方面具有较高经济价值,对其进行快速、准确的物种鉴定兼具理论意义和应用前景。以木霉属35个概念清晰的种为材料,选择ITS、rpb2和 tef1作为候选基因序列,利用TaxonGap对231个序列片段进行分析,将种内与种间序列差异以及序列获取难易程度作为评价指标,筛选该属的补充条形码片段。结果表明,rpb2具有适宜的种内与种间序列差异,其最小的种间差异（2.48%）,大于最大种内差异（1.8%）,种内、种间遗传距离存在明显的间隔区,并且该基因序列具有较高的PCR扩增与测序成功率（94.4%）;ITS和tef1基因序列的种内与种间序列差异之间存在交叉重叠。因此建议rpb2作为木霉属的补充DNA条形码序列。