赵冬柑桔锈螨的空间格局与抽样技术

应用6个聚集度指标分析了赵冬柑桔锈螨成虫的空间格局，并对抽样技术进行了探讨，结果表明，赵冬柑桔锈螨成虫的空间格局为聚集型；田间的最适抽样部位是植株上，中部叶片的叶腋处，提出了越冬成虫密度估计的序贯抽样方案。     

露地和避雨栽培条件下葡萄苗木霜霉病病株空间分布型及其抽样技术

【目的】明确不同栽培条件下葡萄霜霉病空间分布型及其抽样技术。【方法】通过5种聚集度指数测定法判定了不同栽培条件下葡萄霜霉病各个流行时期的空间分布格局,利用Taylor幂法则和Iwao回归法分析病害聚集原因,采用Iwao回归法计算不同发病程度下的理论抽样数及序贯抽样数。【结果】露地栽培条件下葡萄霜霉病空间分布型在始发期为随机分布,在盛发期转为聚集分布,在衰退期转为均匀分布;而避雨栽培条件下葡萄霜霉病整个生长季空间分布型均为聚集分布。不同栽培条件下,在病害始发期至盛发期,病株间均表现为相互吸引,病株的空间分布为聚集的,且聚集强度随着病株密度的增加而升高,而在盛发期至衰退期,随着病株密度的增加,露地栽培个体群在田间由聚集分布转为均匀分布,避雨栽培个体群在田间则仍呈现聚集分布的格局。盛发期葡萄霜霉病聚集的原因是由病原菌本身的生物学特性和环境因素共同作用引起的。用Iwao理论抽样模型,计算出不同发病程度情况下所需的最适抽样数量,随着病情指数的增加,所需抽样数量递减。露地栽培条件下葡萄霜霉病序贯抽样模型为To(N)=0.450N±2.154 N,避雨栽培条件下葡萄霜霉病序贯抽样模型为To(N)=0.450N±2.102 N。【结论】露地和避雨栽培条件下葡萄霜霉病的空间分布格局存在一定差异,并对比分析了造成2者差异的原因。明确了不同栽培条件下葡萄霜霉病各个流行时期的最佳取样方式、最适抽样数量及指导田间防治的序贯抽样表。     

栗瘿蜂虫瘿在板栗林内空间分布格局研究

应用聚集度指标法、Iwao回归分析法、Taylor幂指数法对怀柔区试验地板栗林内栗瘿蜂虫瘿空间分布格局进行了分析.结果表明:栗瘿蜂虫瘿在板栗林内呈现出聚集分布的特点,而且种群在一切密度下都是聚集的,聚集强度随种群密度的升高而增加.栗瘿蜂虫瘿数量在树冠东、西、南、北4个方向上的分布差异显著,以南方向最多,北方向最少.树冠上、中、下层虫瘿分布存在显著差异,以下层分布最多,上层最少.采用Iwao的方法分析了不同方位、不同层次分布特点和空间分布形式.结果表明:各个方向、不同层次上虫瘿分布普遍呈现聚集分布的特点.根据Iwao提出的新序贯抽样理论,列出了试验地区的序贯抽样表,为林间抽样调查和防治提供了依据.     

陕南柑桔草履蚧为害特点及防治对策

近年在陕南柑桔产区首次发现草履蚧为害枳和柑桔等。一年发生一代,以卵在树盘表土层或根颈部翘皮缝隙越冬。3月中下旬越冬卵陆续孵化若虫,5月中旬成虫开始上树为害,可为害温州蜜柑、朱红桔、椪柑、柚类和枳等,以成虫聚集栖息在主侧枝分叉处、果梗处以及当年新梢取食为害,7月中旬雌成虫陆续下树产卵。主要防治方法：冬季挖园,浅耕树盘,消灭越冬虫卵;成虫上树前(陕南在5月中旬前),树干缠绕塑料胶带或塑料薄膜,阻断成虫上树为害;采用“二次杀成虫法”,先选用45%毒死蜱乳油1 200倍液等对树冠进行喷雾,2～3 h后(90%成虫掉下树盘)选用45%毒死蜱乳油800倍液等再次对掉落树盘“假死”的成虫进行喷药。     

塞罕坝地区主要害鼠的空间分布型及抽样技术研究

通过调查塞罕坝地区不同林分类型以及林龄害鼠的危害,采用聚集度指标分析法和回归方程分析法分析该地区主要害鼠的空间分布型,明确御道口牧场以及塞罕坝机械林场草原鼢鼠和达乌尔黄鼠空间分布类型、分布的成分以及形成的原因,并确立相关抽样技术。研究表明:塞罕坝机械林场的优势种为达乌尔黄鼠,御道口牧场的优势种为草原鼢鼠,且两种害鼠均为聚集分布,其分布基本成分均为个体群,且个体间互相吸引,影响草原鼢鼠以及达乌尔黄鼠聚集分布是由于其本身的聚集行为和环境的异质性共同作用的结果;种群密度的抽样方法采用理论抽样模型和序贯抽样技术,确定了林间不同害鼠密度时最适抽样数。害鼠空间分布类型及抽样技术的确定为塞罕坝地区鼠害的预测预报及综合防控提供了技术支撑。     

柑桔木虱越冬成虫冬春季种群数量动态观察

对广西柑桔产区柑桔木虱越冬成虫种群数量动态进行观察,了解其活动规律。结果表明,在冬春季柑桔木虱越冬成虫能在不同植株之间活动,特别是在气温8℃时,活动更明显;柑桔木虱越冬成虫种群数量与气温关系密切,遇到低于0℃或日平均气温低于8℃持续5天以上时,越冬成虫数量会减少。九里香春梢萌芽期开始后,越冬成虫快速减少。因此,笔者认为冬季防治柑桔木虱的时间,宜在2月下旬以前(柑桔嫩梢萌芽前)进行,结合冬季清园,在柑桔木虱越冬成虫产卵之前及时喷药杀灭,最大限度地减少越冬虫口基数。     

冬治梨木虱效果好

梨木虱是梨树上的主要害虫,每年发生4～5代。成虫分冬、夏型,冬型成虫大多在梨树枝干的裂缝内越冬,少部分在杂草、落叶、土壤中越冬。冬季对梨木虱越冬场所采取综合治理措施,可消灭80％以上的越冬成虫．为来年梨树丰产打下良好基础。具体措施：     

冬治梨木虱效果好

梨木虱是梨树上的最主要害虫。每年发生4—5代。成虫分冬、夏型两种．冬型成虫大部分在梨树枝干的裂缝内越冬,小部分在杂草、落叶及土壤中越冬。冬季对梨木虱越冬场所采取综合治理措施,可消灭80％以上的越冬成虫。为来年梨树丰产打下良好基础。     

冀北地区梨木虱大发生原因及防治措施

1　大发生原因1.1　梨木虱基数过高　越冬成虫数直接影响来年的发生程度。一般来说 ,梨树萌芽前喷施 1次 3～ 5°Be石硫合剂防治越冬害虫 ,能明显降低越冬成虫基数。而果农为节省资金或过分信赖其它药剂 ,取消了这次用药 ,造成越冬成虫基数过大 ,夏季为害严重。1.2　药剂使用不当　首先是药剂品种使用不合理 ,长期使用单一药剂 ,梨木虱产生抗药性。其次是药剂使用时期不科学 ,错过了最佳防治时期。据观察 ,梨木虱越冬成虫出蛰时期长 ,高峰期不明显 ,但成虫产卵期 (花芽膨大至花序分离 )较集中 ,这是药剂防治最有利的时期。部分果农未能抓住…     

冬治梨木虱效果好

梨木虱是梨树上的最主要的害虫，每年发生4—5代。成虫分冬、夏型两种，冬型成虫在梨树枝干的裂缝内越冬，少数在杂草、落叶及土壤中越冬。对其越冬场所进行综合农事操作，可消灭80％以上的越冬成虫。     

Estimating landscape pattern metrics from a sample of land cover

Although landscape pattern metrics can be computed directly from wall-to-wall land-cover maps, statistical sampling offers a practical alternative when complete coverage land-cover information is unavailable. Partitioning a region into spatial units and then selecting a subset (sample) of these units introduces artificial patch edge and patch truncation effects that may lead to biased sample-based estimators of landscape pattern metrics. The bias and variance of sample-based estimators of status and change in landscape pattern metrics were evaluated for four 120-km × 120-km test regions with land cover provided by the 1992 and 2001 National Land-Cover Data of the United States. Bias was generally small for both the estimators of status and estimators of change in landscape pattern, but exceptions to this favorable result exist and it is advisable to assess bias for the specific metrics and region of interest in any given application. A 10-km × 10-km sample block generally yielded larger biases but smaller variances for the estimators relative to a 20-km × 20-km sample block. Stratified random sampling improved precision of the estimators relative to simple random sampling. The methodology developed to determine properties of sample-based estimators can be readily extended to evaluate other landscape pattern metrics, regions, and sample block sizes.     

Ecosystem-scale spatial heterogeneity of stable isotopes of soil nitrogen in African savannas

Soil ¹⁵N is a natural tracer of nitrogen (N) cycling. Its spatial distribution is a good indicator of processes that are critical to N cycling and of their controlling factors integrated both in time and space. The spatial distribution of soil δ¹⁵N and its underlying drivers at sub-kilometer scales are rarely investigated. This study utilizes two sites (dry vs. wet) from a megatransect in southern Africa encompassing locations with similar soil substrate but different rainfall and vegetation, to explore the effects of soil moisture and vegetation distribution on ecosystem-scale patterns of soil δ¹⁵N. A 300-m long transect was set up at each site and surface soil samples were randomly collected for analyses of δ¹⁵N, %N and nitrate content. At each soil sampling location the presence of grasses, woody plants, Acacia species (potential N fixer) as well as soil moisture levels were recorded. A spatial pattern of soil δ¹⁵N existed at the dry site, but not at the wet site. Woody cover distribution determined the soil δ¹⁵N spatial pattern at ecosystem-scale; however, the two Acacia species did not contribute to the spatial pattern of soil δ¹⁵N. Grass cover was negatively correlated with soil δ¹⁵N at both sites owing to the lower foliar δ¹⁵N values of grasses. Soil moisture did not play a role in the spatial pattern of soil δ¹⁵N at either site. These results suggest that vegetation distribution, directly, and water availability, indirectly, affect the spatial patterns of soil δ¹⁵N through their effects on woody plant and grass distributions.     

Empirical patterns of the effects of changing scale on landscape metrics

While ecologists are well aware that spatial heterogeneity is scale-dependent, a general understanding of scaling relationships of spatial pattern is still lacking. One way to improve this understanding is to systematically examine how pattern indices change with scale in real landscapes of different kinds. This study, therefore, was designed to investigate how a suite of commonly used landscape metrics respond to changing grain size, extent, and the direction of analysis (or sampling) using several different landscapes in North America. Our results showed that the responses of the 19 landscape metrics fell into three general categories: Type I metrics showed predictable responses with changing scale, and their scaling relations could be represented by simple scaling equations (linear, power-law, or logarithmic functions); Type II metrics exhibited staircase-like responses that were less predictable; and Type III metrics behaved erratically in response to changing scale, suggesting no consistent scaling relations. In general, the effect of changing grain size was more predictable than that of changing extent. Type I metrics represent those landscape features that can be readily and accurately extrapolated or interpolated across spatial scales, whereas Type II and III metrics represent those that require more explicit consideration of idiosyncratic details for successful scaling. To adequately quantify spatial heterogeneity, the metric-scalograms (the response curves of metrics to changing scale), instead of single-scale measures, seem necessary.This revised version was published online in May 2005 with corrections to the Cover Date.     

The effect of fire spatial scale on <Emphasis Type="Italic">Bison</Emphasis> grazing intensity

To determine whether fire spatial and temporal scales affect foraging behavior and grazing intensity by Bison (Bison bison), we burned three different patch sizes (225, 900, and 3600 m²) across an otherwise homogeneous grassland landscape. We then monitored grazing intensity for the succeeding 14 months. During the first 5 months after the burn (August–January), the Bison grazing intensity pattern was affected by whether a plot was burned and only marginally affected by plot size. During the next 5 months (January–June), grazing intensity was unaffected by plot size, but was greatest in the unburned 225 and 3600-m² plots. The final 4 months (June–October), grazing intensity was unaffected by treatments other than being higher in the unburned 3600-m² plots. By the final sampling date, biomass was significantly greater in the burned plots and grazing intensity appeared to be responding to the amount of biomass present and the total amount of N present. The pattern displayed within the first 5 months after the burn is congruent with the expectations of optimal foraging theory with overmatching in the smallest plot size of 225 m² (BioScience 37 (1987) 789–799). The next two sampling periods displayed a matching aggregate response relative to biomass availability (Oecologia 100 (1999) 107–117) and total nitrogen mass (g m⁻²). The temporal shift that we found in Bison response to burn patch size is, to our knowledge, the first such examination of both spatial and temporal responses by Bison to landscape heterogeneity. We now have quantitative evidence of how native herbivores can alter their foraging responses to changes in landscape structure over time.     

A method for the use of landscape metrics in freshwater research and management

Freshwater research and management efforts could be greatly enhanced by a better understanding of the relationship between landscape-scale factors and water quality indicators. This is particularly true in urban areas, where land transformation impacts stream systems at a variety of scales. Despite advances in landscape quantification methods, several studies attempting to elucidate the relationship between land use/land cover (LULC) and water quality have resulted in mixed conclusions. However, these studies have largely relied on compositional landscape metrics. For urban and urbanizing watersheds in particular, the use of metrics that capture spatial pattern may further aid in distinguishing the effects of various urban growth patterns, as well as exploring the interplay between environmental and socioeconomic variables. However, to be truly useful for freshwater applications, pattern metrics must be optimized based on characteristic watershed properties and common water quality point sampling methods. Using a freely available LULC data set for the Santa Clara Basin, California, USA, we quantified landscape composition and configuration for subwatershed areas upstream of individual sampling sites, reducing the number of metrics based on: (1) sensitivity to changes in extent and (2) redundancy, as determined by a multivariate factor analysis. The first two factors, interpreted as (1) patch density and distribution and (2) patch shape and landscape subdivision, explained approximately 85% of the variation in the data set, and are highly reflective of the heterogeneous urban development pattern found in the study area. Although offering slightly less explanatory power, compositional metrics can provide important contextual information.     

Spatial dependence and the relationship of soil organic carbon and soil moisture in the Luquillo Experimental Forest,Puerto Rico

We used geo-spatial statistical techniques to examine the spatial variation and relationship of soil organic carbon (SOC) and soil moisture (SM) in the Luquillo Experimental Forest (LEF), Puerto Rico, in order to test the hypothesis that mountainous terrain introduces spatial autocorrelation and crosscorrelation in ecosystem and soil properties. Soil samples (n = 100) were collected from the LEF in the summer of 1998 and analyzed for SOC, SM, and bulk density (BD). A global positioning system was used to georeference the location of each sampling site. At each site, elevation, slope and aspect were recorded. We calculated the isotropic and anisotropic semivariograms of soil and topographic properties, as well as the cross-variograms between SOC and SM, and between SOC and elevation. Then we used four models (random, linear, spherical and wave/hole) to test the semi-variances of SOC, SM, BD, elevation, slope and aspect for spatial dependence. Our results indicate that all the studied properties except slope angle exhibit spatial dependence within the scale of sampling (200 – 1000 m sampling interval). The spatially structured variance (the variance due to the location of sampling sites) accounted for a large proportion of the sample variance for elevation (99%), BD (90%), SOC (68%), aspect (56%) and SM (44%). The ranges of spatial dependence (the distances within which parameters are spatially dependent) for aspect, SOC, elevation, SM, and BD were 9810 m, 3070 m, 1120 m, 930 m and 430 m, respectively. Cross correlograms indicate that SOC varies closely with elevation and SM depending on the distances between samples. The correlation can shift from positive to negative as the separation distance increases. Larger ranges of spatial dependence of SOC, aspect and elevation indicate that the distribution of SOC in the LEF is determined by a combination of biotic (e.g., litterfall) and abiotic factors (e.g., microclimate and topographic features) related to elevation and aspect. This demonstrates the importance of both elevation and topographic gradients in controlling climate, vegetation distribution and soil properties as well as the associated biogeochemical processes in the LEF.This revised version was published online in May 2005 with corrections to the Cover Date.     

越橘园铜绿丽金龟幼虫田间分布型及抽样技术

通过田间调查和计算,明确了铜绿丽金龟幼虫在越橘园内呈聚集分布,且符合奈曼分布型和负二项分布型.通过对比三点法、五点法和棋盘式抽样法发现,棋盘式抽样法最适合对铜绿丽金龟幼虫进行调查.在棋盘式抽样法中,以每个样点的抽样面积为1 m2为最佳,这样既省时省力,又高效.     

The influence of sampling scheme and interpolation method on the power to detect spatial effects of forest birds in Ontario (Canada)

Spatial ecology is becoming an increasingly important component of resource management, and the general monitoring of how human activities affect the distribution and abundance of wildlife. Yet most work on the reliability of sampling strategies is based on a non-spatial analysis of variance paradigm, and little work has been done assessing the power of alternative spatial methods for creating reliable maps of animal abundance. Such a map forms a critical response variable for multiple scale studies relating landscape structure to biotic function. The power to reconstruct patterns of distribution and abundance is influenced by sample placement strategy and density, the nature of spatial auto-correlation among points, and by the technique used to extrapolate points into an animal abundance map. Faced with uncertainty concerning the influence of these factors, we chose to first synthesize a model reference system of known properties and then evaluate the relative performance of alternative sampling and mapping procedures using it. We used published habitat associations of tree nesting boreal neo-tropical birds, a classified habitat map from the Manitou Lakes area of northwestern Ontario, and point count means and variances determined from field studies in boreal Canada to create 4 simulated models of avian abundance to function as reference maps. Four point sampling strategies were evaluated by 4 spatial mapping methods. We found mixed-cluster sampling to be an effective point sampling strategy, particularly when high habitat fragmentation was avoided by restricting samples to habitat patches >10 ha in size. We also found that of the 4 mapping methods, only stratified ordinary point kriging (OPK) was able to generate maps that reproduced an embedded landscape-scale spatial effect that reduced nesting bird abundance in areas of higher forest age-class fragmentation. Global OPK was effective only for detecting broader, regional-scale differences. This revised version was published online in July 2006 with corrections to the Cover Date.