Spatial patterns of primary productivity in the Greater Yellowstone Ecosystem

Landscapes are often heterogeneous in abiotic factors such as topography, climate, and soil, yet little is known about how these factors may influence the spatial distribution of primary productivity. We report estimates of aboveground net primary productivity (ANPP) in 90 sample stands stratified by cover type and elevation class, and use the results to predict ANPP across a portion of the Greater Yellowstone Ecosystem. Tree ANPP was estimated by sampling tree density by species and diameter classes and estimating average annual diameter increment by tree coring. Biomass for current tree diameter and past tree diameter were calculated by species and diameter class for each stand using the dimension analysis software BIOPAK. Shrub ANPP was estimated by calculating current biomass from basal area using BIOPAK and dividing by the assumed average life span of the shrubs. Clipping at the end of the growing season was used to estimate herb ANPP. Differences in ANPP among cover types and elevation classes were examined with analysis of variance. Multiple regression was used to examine relationships between ANPP, and soil parent material, topography, and cover type. The best regression model was used to predict ANPP across the study area.We found ANPP was highest in cottonwood, Douglas-fir, and aspen stands, intermediate in various seral stages of lodgepole pine, and lowest in grassland and sagebrush cover types. Parent material explained significant variation in ANPP in mature and old-growth lodgepole pine stands, with rhyolite ash/loess being the most productive parent material type. ANPP decreased with increasing elevation in most cover types, possibly because low temperatures limit plant growth at higher elevations in the study area. ANPP was not related to elevation in mature and old-growth lodgepole pine stands, due to relatively rapid growth of subalpine fir at higher elevations.A regression model based on cover type and elevation explained 89% of the variation in ANPP among the sample stands. This model was used to generate a spatially continuous surface of predicted ANPP across the study area. The frequency distribution of predicted ANPP was skewed towards lower levels of ANPP, and only 6.3% of the study area had a predicted ANPP level exceeding 4500 kg/ha/yr. Patches high in predicted ANPP were primarily at lower elevations, outside of Yellowstone National Park, and near the national forest/private lands boundary. These patterns of ANPP may influence fire behavior, vertebrate population dynamics, and other ecological processes. The results reinforce the need for coordinated management across ownership boundaries in the Greater Yellowstone Ecosystem.     

湿度密度仪在林道施工质检中的应用研究

通过对比试验及平行对比试验证明,湿度密度仪法的试验精度能够满足林区公路工程的要求,而且均在规程中允许的差值范围之内。该仪器具有时速快的特点,一次可测出干密度、湿密度及含水量三个指标,是林区公路工程施工质量管理中,可直接在现场提供可靠技术数据,监控现场施工质量较为理想的有效仪器。     

天牛防治法的演变及评述

本文对从古至今天牛防治方法的演变作了较为全面的论述,并对各种防治方法作了评价。     

海南西培农场橡胶树条溃疡病发生规律及防治经验总结

对海南省西培农场橡胶树条溃疡病的发生和流行规律,以及防治经验进行总结,以期引起生产者在生产实践中对该病害的重视。     

一类具有反馈控制捕食系统的持久性

利用微分方程比较原理研究了一类具有反馈控制的捕食系统，得到了保证该系统持续生存的充分条件．     

江西赣江沙害的流域生态学以及治理的初步研究

江西赣江是我国南方的重要河流,流域面积约占省域的一半.目前,其干流、部分支流和部分流域的沙害已极为严重,航运功能已基本丧失.本文对赣江的沙害进行了流域生态学的研究,以探索其流域中的沙源,部分流域的严重生态破坏和粗沙流出的原因,粗沙的流出量,以及沙害对生态环境和经济发展的影响.同时,也对沙害的相对完全治理进行了小流域的实验和示范,并提出了相关的推广建议.     

THE DECOUPLJNG CALCULATION OF MULTI-AREA POWER SYSTEM LOAD FREQUENCY CONTROL

The calculating burden of the decoupling judgement of multi-area power system load frequeney centrel is very large by tranditional methods. This paper changcs the decoupling judgement problem into a minimum cost network flow problem. The solution algorithm is out-of-kilter . algorithm which is characterized by simple manipaultion, fast and reliable convergence. In the paper, we discuss and calculate the decoupling problem of two arca power system load frequency control. The results show that the proposed approach is feasible and effective.     

蔬菜工厂化生产中夏秋季环境因子的合理调控

在自行设计和自行研制的温室无土栽培系统中进行了蔬菜营养液循环栽培试验，对夏秋季环境因子调控效果，调控指标及相适应的生产技术特点进行了探讨。     

“三控”施肥技术对水稻生长发育和氮素吸收利用的影响

以两系杂交稻品种粤杂889为材料,设置三控施肥法和习惯施肥法2种处理,进行了早、晚两季试验,研究了“三控”施肥技术下水稻的生长发育和氮素吸收利用特性。结果表明：（1）与习惯施肥法相比,三控施肥法在减少氮肥10 %的情况下增产6 %~8 %,有效穗数、结实率和千粒重均有不同程度的提高。（2）三控施肥法具有明显的物质生产优势,其总干物质量比习惯施肥法高3.8 %~11.0 %。三控施肥法的中、后期叶绿素含量高,但叶面积指数相差不大。（3）三控施肥法的成穗率高,其最高茎蘖数比习惯施肥法减少5.9 %~10.6 %,但有效穗反而高于习惯施肥法,成穗率比习惯施肥法高5.5~11.8个百分点。（4）与习惯施肥法相比,三控施肥法在前期（幼穗分化前）的吸氮量低,但中、后期的吸氮量和全生育期总吸氮量明显高于习惯施肥法。三控施肥法的氮肥吸收利用率、农学利用率和氮肥偏生产力均高于习惯施肥法。     

基于VB的电喷发动机运行监控系统开发与实现

发动机运行监控系统将人机交互界面嵌入PC机中,通过串行通信实现发动机运行状态参数的实时采集、显示以及在线调整。本文利用VB6．0设计了电喷发动机运行监控系统,通过VB6．0Active中的MSComm通信控件。实现了在windows环境下的上位机和主控单片机之间的串行通信,并通过对标志位的判断实现上、下位机参数的对应可视化。实验表明该系统能够较好地提高发动机参数匹配效率,从而获得发动机各工况下的最佳控制参数值。