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基于辅助变量的森林半腐层厚度空间插值精度 总被引:1,自引:0,他引:1
基于地统计学方法,利用3种以海拔作为辅助变量的空间插值算法[局部平均的简单kriging法(simple kriging with locally varying mean,SKlm)、带有外部漂移的kriging法(kriging with an external drift,KED)和协kriging法(cokrging,COK)]计算了森林半腐层厚度的空间插值精度,并进行了交叉验证.结果表明:KED法既考虑了变量之间的空间变异,又考虑到影响局部空间变化的因素,与其他插值方法相比,其精度有很大提高;由于海拔与半腐层厚度之间的相关关系较弱,导致SKlm法的插值精度没有达到预期效果;COK法直接将海拔用于估计半腐层厚度,由于在边界地区缺乏采样点数据,因此边界地区的插值出现了多处突变区域.对比地统计学方法与距离反比权重法(inverse distance weighting, IDW)在本研究中的插值精度,除了KED方法的插值精度较高外,其余方法的插值精度均不及IDW,原因可能是利用辅助变量辅助地统计学插值时,主、辅助变量之间的相关关系在插值中起着重要作用. 相似文献
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降水空间插值技术的研究进展 总被引:34,自引:1,他引:34
降水的空间分布信息在水资源管理、灾害预测预警和区域可持续发展研究等方面的地位已越来越重要。然而,空间降水插值却一直是个难题,影响降水的因素很多,如经度、纬度、高程、坡度、坡向、离水体的距离等,建立一个通用的降水插值模型几乎是不可能的。空间降水插值方法很多,优缺点和适用性不同。总体上,降水的空间插值方法有3类:整体插值法(趋势面法和多元回归法等)、局部插值法(泰森多边形法、反距离加权法、克里金插值法和样条法)和混合插值法(整体插值法和局部插值法的综合)。近年来,随着应用数学和人工神经网络技术的发展,很多新方法如BP网络、径向基函数网络等逐渐应用到降水插值中。另外,研究区域和时间尺度的不同决定了所选用的插值方法及模型不同;即使是同一种插值方法,应用于不同的研究区域,所取得的结果也不同。因此,应根据具体的研究区域的自然地理特征,选择不同的插值方法建立不同的插值模型。在各种插值方法中,兼具其它插值方法优点的混合插值法有利于提高降水插值的精度,是未来降水插值研究的一个发展方向。 相似文献
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利用GIS和多变量分析估算青藏高原月降水 总被引:7,自引:0,他引:7
随着空间降水信息需求的日益增加,空间降水插值已被广泛应用。降水区域不同,插值方法不同;时间尺度不同,插值方法也不相同。适合于所有地区的通用降水插值模型是不存在的。青藏高原自然地理特征独特,分析高原降水的时空格局意义重要。以青藏高原及其周边地区140个气象站点的月降水信息及其该地区的数字高程数据(DEM)为基础,利用G IS工具,对比分析了五种插值方法在青藏高原不同降水年份(以1998年、1997年分别代表丰水及欠水年份)的干湿季(1998年的干湿季分别以12月份和8月份为代表,1997年的干湿季分别以1月份和7月份为代表)月降水插值中的应用,并对整个高原地区的干季和湿季的月降水进行制图。这5种插值方法分别是:克里金插值法、反距离加权法、样条法、混合插值法Ⅰ和混合插值法Ⅱ,前3种插值方法未考虑海拔高度对降水的影响,而混合插值法则将高程作为降水的重要影响因子。结果表明:①在干季,无论是丰水还是欠水年份,月降水量都比较少,高程对降水量的影响较小,在月降水插值时可不考虑高程的影响,克里金法的月降水插值精度最高。②在湿季,月降水量较多,高程的影响较大,混合插值法比局部插值法及克里金插值法的精度高,尤以混合插值法Ⅱ(多元回归和样条法的综合)的精度最高。③干季,整个高原的月降水很少,西部和北部降水最少,东部和南部相对较多;湿季,高原的月降水较多,空间格局表现为由东南向西北递减。 相似文献
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杉木种子生理特性和地理变异(简报) 总被引:2,自引:0,他引:2
产地纬度较高的杉木种子发芽率高、涩籽率低,且有胚种子单宁含量较少,种子和胚的鲜、干重都较重,20~25℃为各产地种子的发茅适宜温度。各产地种子所含氨基酸种类变异不大。 相似文献
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不同干扰程度下土壤有机质空间最优插值法研究 总被引:4,自引:0,他引:4
选择最优空间插值方法对明确不同干扰程度下干旱区土壤有机质空间分布规律具有重要意义。通过对新疆阜康市土壤采样分析,分别运用普通克里格法(Ordinary Kriging, OK)、反距离权重法(inverse distance weight, IDW)、径向基函数法(radial basis function, RBF)、局部多项式法(local polynomial, LPI)4种插值方法,描述不同人为干扰程度下干旱区土壤有机质空间分布特征,以探讨其最优空间插值方法。结果表明:①随干扰程度增加,土壤有机质含量降低,空间变异性由弱到中等,变异系数由9.27%增加至28.7%;同时,土壤有机质空间自相关性逐渐降低,从无人为干扰区、人为干扰区到重度人为干扰区分别呈强烈、中等、弱相关关系,即干扰程度越强受随机因素作用越大。②虽然4种方法的插值精度均随干扰程度的增强而降低。但OK法在空间结构性较强的无人为干扰区插值效果最好,R~2为0.625;在人为干扰区及重度人为干扰区RBF法的插值精度均最高,R~2分别为0.562和0.434。该结果为寻找适合于不同干扰程度下干旱区土壤有机质的空间插值方法提供一定的科学参考。 相似文献
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基于辅助环境变量的土壤有机碳空间插值——以黄土丘陵区小流域为例 总被引:1,自引:0,他引:1
利用普通克里格法(OK)、反距离加权法(IDW)、径向基函数法(RBF)、基于土地利用类型修正的普通克里格法(OK_LU)4种插值方法,对黄土丘陵羊圈沟小流域的土壤有机碳含量进行空间插值。预测结果的准确性通过Pearson相关系数(R),平均绝对误差(MAE),均方根误差(RMSE),准确度(AC)来评价。研究结果表明:(1)在前3种常规空间插值方法中,OK对刻画区域土壤有机碳的空间分布趋势效果最佳,其预测MAE值和RMSE值均为最小,Pearson相关系数(R)和准确度(AC)最大,说明其预测结果的准确性最好、预测的极端误差也最小;其次为RBF;IDW预测的效果最差。(2)OK_LU在空间特征表达方面能够更好地反映复杂地形区的局部变异,其插值结果的精度相比OK有一定程度的提高,其平均绝对误差(MAE)从0.900%降到了0.567%,均方根误差(RMSE)从1.101%降到了0.777%,Pearson相关系数(R)从0.4026提高到0.5589,准确度(AC)从0.9081提高到0.9505。综合比较,在黄土丘陵地区,OK_LU能使插值结果的精度有较大提高,是土壤有机碳空间制图的有效途径。 相似文献
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杉木种子涩籽胚败育与过氧化物酶同工酶活性及脂质过氧化作用的关系 总被引:1,自引:0,他引:1
本文报导杉木种子涩籽胚败育过程中过氧化物酶同工酶活性及脂质过氧化产物丙二醛(MDA)含量的变化。试验结果表明,涩籽胚败育过程伴随着过氧化物酶活性降低,后胚期同工酶带比健籽少一条,胚成熟期酶带强度明显比健籽弱,而丙二醛含量比健籽增高5—10倍。由于过氧化物酶活性降低,促进了脂质过氧化作用,结果产生更多脂质自由基毒害细胞,导致胚与胚乳膜质结构破坏,细胞解体而死亡变质。健籽与涩籽同工酶谱的差异,可能是控制健籽胚正常发育的基因表达受到干扰,使形成涩籽的基因得到表达的结果。 相似文献
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Timothy G. Laman 《Oecologia》1996,107(3):347-355
Due to their copious seed production and numerous dispersers, rain forest fig trees have been assumed to produce extensive and dense seed shadows. To test this idea, patterns of seed dispersal of two species of large hemiepiphytic fig tree were measured in a Bornean rain forest. The sample included four Ficus stupenda and three F. subtecta trees with crop sizes ranging from 2,000 to 40,000 figs (400,000 to 13,000,000 seeds). Seed rain out to a distance of 60 m from each study tree was quantified using arrays of seed traps deployed in the understory. These trees showed a strongly leptokurtic pattern of dispersal, as expected, but all individuals had measurable seed rain at 60 m, ranging from 0.2 to 5.0 seeds/m2. A regression of In-transformed seed rain density against distance gave a significant fit to all seven trees' dispersal patterns, indicating that the data could be fitted to the negative exponential distribution most commonly fitted to seed shadows. However, for six of seven trees, an improved fit was obtained for regressions in which distance was also In-transformed. This transformation corresponds to an inverse power distribution, indicating that for vertebrate-dispersed Ficus seeds, the tail of the seed rain distribution does not drop off as rapidly as in the exponential distribution typically associated with wind dispersed seed shadows. Over 50% of the seed crop was estimated to fall below each fig tree's crown. Up to 22% of the seed crop was dispersed beyond the crown edge, but within 60 m of the tree. Estimates of the maximum numbers of seeds which could have been transported beyond 60 m were 45% for the two largest crops of figs, but were under 24% for the trees with smaller crops. Seed traps positioned where they had an upper canopy layer above them were associated with higher probabilities of being hit by seeds, suggesting that vertebrate dispersal agents are likely to perch or travel through forest layers at the same level as the fig crown and could concentrate seeds in such areas to some degree. The probability of a safe site at 60 m from the fig tree being hit by seeds is calculated to be on the order of 0.01 per fruiting episode. Fig trees do not appear to saturate safe sites with seeds despite their large seed crops. If we in addition consider the rarity of quality establishment sites and post-dispersal factors reducing successful seedling establishment, hemiepiphytic fig trees appear to face severe obstacles to seedling recruitment. 相似文献
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Male reproductive output, pollen in plants and sperm in animals has been shown to constitute a substantial cost for many organisms. In parthenogenetic hermaphrodites, selection is therefore expected to reduce the allocation of resources to male reproductive output. However, sustained production of pollen or sperm has been observed in numerous asexual hermaphrodites. We studied the widespread production of pollen by triploid asexual dandelions, Taraxacum sect. Ruderalia, comparing rare male sterile individuals with pollen producing asexuals. We found that individuals can show plasticity in the production of pollen, but that it is nevertheless possible to distinguish between (facultatively) male sterile asexuals and male fertile asexuals. Based on evidence from genetic markers and crosses, we conclude that the male sterility in asexual dandelions is caused by nuclear genes, in contrast to the cytoplasmically inherited male sterility previously found in sexual dandelions. Male sterile lineages did not produce more seeds per flower head, heavier seeds or seeds that were more viable. However, male sterile plants did produce more seed heads and hence more seeds than pollen producing ones, indicating that they were able to reallocate resources toward seed production. Considering the difference in seed production, it remains puzzling that not more asexual dandelions are male sterile. 相似文献
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R.M. Cowling,D.M. Richardson & S.M. Pierce (eds.) 1977. Vegetation of Southern Africa. 总被引:4,自引:0,他引:4
We determined the role of bird dispersal in seed and seedling dynamics of the tree Kalopanax pictus from 7 years of observing seed rain and seedling emergence in a broad-leaved deciduous forest in central Japan. We also performed an experiment on the influence of seed pulp on germination of seeds of K. pictus. Seeds of this species can lie dormant for several years, and this causes rather constant yearly seedling emergence in spite of irregular seed production. The spatial distribution of the seedlings that emerged each year (maximum distance from nearest conspecific seed-bearing tree of 90 m) was wider than that of gravity-dispersed seeds (max. distance of 37 m), suggesting seed dispersal by birds in winter. Emerged seedling densities at sites over 20 m from the nearest conspecific seed-bearing tree were highest in the spring of 1991, about half a year after the largest seed fall of the observation period. However, emerged seedling densities within 20 m from seed-bearing trees were highest in 1992, 1.5 years after the largest seed fall. These field observations may be explained by the experimental results on the effects of seed pulp on germination. Intact seeds germinate slowly at low germination rates, while seeds without seed pulp germinate quickly at high germination rates. Fallen seeds with seed pulp thus appear to form a seed bank near seed sources (temporal dispersal), while seeds scattered by birds appear to increase the possibility of reaching the present safe sites in distant areas with quick germination (spatial dispersal). 相似文献
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We developed a game-theoretic model for wind-dispersed seed production to examine the seed mass–dispersal ability relationship
and the evolutionarily stable distance of seed dispersal in terms of exploitation of safe sites. We assumed trade-offs between
masses of the embryo (including albumen) and the wind-dispersal structures per seed, and also between seed mass and number
of seeds per parent. We showed that ESS wing-loading is independent of embryo mass; that is, heavy seeds are not poor dispersers
if the cost of producing wind-dispersal structures per unit area is constant. The ESS embryo mass per seed depends only on
the factors which determine the probability of a seedling being established from a seed. However, wing-loading was found to
increase with embryo mass when the change in length was isometric and there was a negative correlation between seed mass and
dispersal ability. Thus, the area–mass relationship in wind-dispersal structures may have large effects on the ESS production
of wind-dispersed seeds. On the other hand, given that only a limited number of adults can be established at a safe site,
the ESS seed dispersal distance depends on the relative degree of sib to non-sib competition. A parent disperses its seeds
over a wide area to exploit many safe sites if sib competition is strong. However, it disperses its seeds within a narrow
area if the mean number of parents per unit area is large, or if non-sib competition is strong. Thus, in addition to an upper
limit on the number of adults per safe site, the degree of sib and non-sib competition may be important for the ESS dispersal
distance in wind-dispersed seeds.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Kathleen Donohue 《Oecologia》1997,110(4):520-527
A factorial design of three densities of siblings at three local distances from seed parents was employed to distinguish
effects of density from effects of dispersal distance on lifespan and fruit production of Cakile edentula var. lacustris, a plant with heteromorphic seeds. The segmented fruits produce two seed types: proximal and distal, with distal seeds having
greater mass and greater dispersibility. Effects of longer distances (0.5 km and 30 km) on lifespan and fruit production were
investigated using plants at low density. The prediction was tested that the greater seed mass of distal seeds increases fitness
when seeds are dispersed into sites of unknown quality away from the home site or when seeds are dispersed to low density.
High density caused earlier mortality and lower probability of reproduction. Distance from the maternal plant did not influence
lifespan or reproduction at distances of 15 m or less, but lifespan was longer 0.5 km from the home site. No interaction was
detected between the effects of density and distance on either lifespan or total fitness. Environmental conditions that influence
fitness did not vary as a function of dispersal distance in this system, and favorable conditions at the home site did not
persist between generations. Therefore, selection on dispersion patterns in natural conditions is likely to be through effects
of density rather than dispersal distance. Proximal seeds had greater reproduction than distal seeds at the home site, and
distal seeds had greater reproduction at the more distant sites (but not the most distant site), as expected, but these performance
differences could not be attributed to differences in mass between the two seed types. Reduced seed mass was favored at the
most distant site, but larger seed mass was favored most strongly at low density. Seeds that are dispersed to low density
are larger, suggesting that although kin selection may limit the effectiveness of individual selection to increase seed mass
under conditions of sibling competition, density-dependent individual selection on seed mass, rather than distant-dependent
selection, also contributes to the observed associations among seed type, seed mass and dispersal ability.
Received: 21 October 1996 / Accepted: 4 December 1996 相似文献
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利用蓝粒太谷核不育硬粒小麦89-2343[AABB 4D(MS2)/4E]与普通小麦7739-3(2n=42)杂交、回交所产生的蓝粒可育株与白粒矮败材料杂交、回交,育成了一份矮败蓝粒小麦.选用13份遗传背景不同的白粒普通小麦与之杂交、回交,育成了13份矮败蓝粒小麦.对后代的粒色和育性分离进行分析,蓝粒矮败不育株占22.1%,白粒非矮秆可育株占77.7%,表明蓝粒基因、Ms2和Rht10均位于附加染色体上,且连锁紧密;但不同轮回亲本,矮败蓝粒的传递率有差异,477A的传递率最高,接近50%.细胞学分析表明矮败蓝粒小麦仍为单体附加系;探讨了矮败蓝粒小麦在群体改良和杂种小麦生产中的应用. 相似文献
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William H. Satterthwaite 《Plant Ecology》2007,193(1):113-130
The traditional dichotomy of seed versus safe site limitation of plant populations is an oversimplification. While most plant
models implicitly assume that the number of safe sites colonized will increase directly with increased seed production by
each plant, the number of sites colonized may also strongly depend on patterns of seed dispersal relative to the parent plant,
since the majority of a plant’s seeds are deposited very close to it and so not all safe sites are equally accessible. I created
a series of spatially explicit individual based plant population models exploring how seed versus safe site limitation is
jointly affected by the number of seeds produced per plant and mean dispersal distances. While increased dispersal distance
led to reduced seed limitation (more saturation of available safe sites) when a parent plant’s site was temporarily unsuitable
following its death, increased dispersal distances could increase seed limitation, especially at low per-plant fecundities,
if safe sites did not turn over through time. Models comparing localized to global seed dispersal indicated substantially
different degrees of seed limitation for constant per-plant fecundities. Thus seed addition experiments need to be designed
to add seeds in realistic spatial patterns to yield meaningful results. 相似文献
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Cuphea lanceolata Ait. (Lythraceae) is an annual diploid (x = 6) with medium-chain fatty acid rich seed oils. Wild C. lanceolata populations are classified as C. lanceolata f. silenoides or C. lanceolata f. lanceolata on the basis of flower pigment differences. Although these taxa are taxonomically close, their interfertility has not been demonstrated. We describe meiotic phenomena underlying the sterility of hybrids between C. lanceolata f. silenoides (LNS-43) and C. lanceolata f. lanceolata (LNC-78) populations. We assayed metaphase and anaphase I microsporocytes of the parent and hybrid populations. The hybrids were female and male sterile. The mean percentage of stainable pollen was 94.9% for the parents and 1.1% for the hybrids. Chromosomes paired and disjoined normally in the parents (LNS-43 and LNC-78) and abnormally in the hybrids (LNS-43 x LNC-78 and LNC-78 x LNS-43). Univalents, unequal chromosome distributions, and laggards were observed in the hybrids. The mean number of univalents per cell was 0.00 for the parents and 5.95 for the hybrids, the mean number of bivalents per cell was 6.00 for the parents and 1.51 for the hybrids, and the mean number of chiasmata per cell was 9.19 for the parents and 4.04 for the hybrids. The most frequently observed (75%) anaphase I chromosome distribution for the hybrids was 7:5:0 (pole-pole-laggards). The genome affinities of the hybrids were half those of the parents (a mean of 0.5 for the hybrids as opposed to 1.0 for the parents). Although C. lanceolata f. silenoides and C. lanceolata f. lanceolata freely hybridize, their progeny are sterile, and the genetic diversity of LNC-78, and perhaps of C. lanceolata f. lanceolata as a whole, cannot be accessed through hybrids with C. lanceolata f. silenoides or C. viscosissima. 相似文献
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濒危植物秦岭冷杉生殖生态学特征 总被引:14,自引:0,他引:14
为了探索秦岭冷杉种群生殖生态学主要特征,通过样地调查、固定样地观测和室内实验分析,系统研究了秦岭地区5个秦岭冷杉(Abies chensiensis)种群生殖特性及其与环境因素的关系,结果表明,5个不同生境的种群都具有结实能力,海拔1500~1600m之间,秦岭冷杉球果的产量较高;各种群球果主要分布在树冠中上部和东、南、西方向;球果以中部产生饱满种子比率最高;秦岭冷杉种子千粒重为43.2g,其中具有生活力者占44.8%,种子的平均含水量为5.7%左右;在天然林散落条件下,种子库的萌发率仅为6.1%,霉坏、搬迁率93.9%;人工播种条件下,种子发芽率在苗圃内高于天然条件下,中低海拔高于高海拔地区。天然条件下,由种子转化成幼苗的过程是秦岭冷杉种群生活史的脆弱环节。秦岭冷杉林经营管理要以就地保护为主,促进种群生殖;要通过森林经营措施,为林下种子萌发和幼苗创造条件;种子脱落后,要及时扰动林下灌木、草本,使种子能够顺利落地,促其发芽成苗;种子大年要注意采种、育苗,扩大人工种群;速生丰产林培育应该以中低海拔的阴坡为主。 相似文献
20.
Five insect biological control agents that attack flower heads of spotted knapweed, Centaurea stoebe L. subsp. micranthos (Gugler) Hayek, became established in western Montana between 1973 and 1992. In a controlled field experiment in 2006, seed-head insects reduced spotted knapweed seed production per seed head by 84.4%. The seed production at two sites in western Montana where these biological control agents were well established was 91.6-93.8% lower in 2004-2005 than 1974-1975, whereas the number of seed heads per square meter was 70.7% lower, and the reproductive potential (seeds/m(2)) was 95.9-99.0% lower. The average seed bank in 2005 at four sites containing robust spotted knapweed populations was 281 seeds/m(2) compared with 19 seeds/m(2) at four sites where knapweed density has declined. Seed bank densities were much higher at sites in central Montana (4,218 seeds/m(2)), where the insects have been established for a shorter period. Urophora affinis Frauenfeld was the most abundant species at eight study sites, infesting 66.7% of the seed heads, followed by a 47.3% infestation by Larinus minutus Gyllenhal and L. obtusus Gyllenhal. From 1974 to 1985, Urophora spp. apparently reduced the number of seeds per seed head by 34.5-46.9%; the addition of Larinus spp. further reduced seed numbers 84.2-90.5% by 2005. Path analysis indicated that both Larinus spp. and U. affinis contributed significantly to reduction of seed production over the 30-yr period. Spotted knapweed density may not decrease significantly until the seed bank falls below a critical threshold. 相似文献