疏勒河流域不同植被类型土壤酶活性动态变化

以疏勒河流域中游玉门饮马农场不同植被类型（白刺、小麦、苜蓿、孜然和茴香）土壤为研究对象,以荒地为对照,探讨疏勒河流域绿洲荒漠过渡带不同植被类型条件下土壤酶活性季节变化特征。结果表明：不同植被类型显著提高了土壤脲酶、碱性磷酸酶、硝酸还原酶、脱氢酶和过氧化氢酶活性,且0～20 cm土层高于20～40 cm土层。其中苜蓿地土壤脲酶和硝酸还原酶含量最高,其平均值比对照分别增加了77.88%和156.94%;孜然地碱性磷酸酶含量最高,平均是对照的4.43倍;小麦地脱氢酶和过氧化氢酶活性最高,其平均值比对照分别提高了112.72%和51.00%。土壤脱氢酶活性与土壤磷酸酶、过氧化氢酶之间呈显著、极显著的正相关关系。土壤酶活性受生长季节影响较大,但无明显的规律性。5种植被类型土壤酶活性存在差异,但因季节因素的影响,很难确定哪种植被类型对土壤酶活性的影响最大。     

海南昌化江流域天然林景观格局演变研究

以遥感影像为基础数据源,通过面向对象的影像分析软件Ecognition和ArcGIS软件,解译提取昌化江流域1995年、2000年和2007年天然林信息,以Fragstats景观格局分析软件为景观指数计算工具,选择景观斑块形状指数、景观斑块数量破碎化指数、景观斑块分维数指数等指标,对昌化江流域天然林空间格局的动态变化进行研究。结果表明:1995年、2000年和2007年昌化江流域天然林总面积分别为1 431.38 km2,2 143.17 km2和1 487.98km2,天然林景观空间格局发生了波浪形变化,目前天然林破坏严重。分析结果为天然林的保护与恢复提供了科学依据。     

新疆环塔里木盆地林果产业发展现状及对策

新疆环塔里木盆地林果产业发展迅速,林果种植面积急速扩张,经济效益、社会效益喜人,但在产业结构调整、合理化布局过程中也出现了一些问题。通过充分调查与研究,从生态安全、粮食安全、可持续发展角度出发,分析存在的问题,提出了相应的对策措施。     

红枫湖水库底泥的氮磷蓄积量及分布特征

通过对红枫湖水库底泥分布及底泥厚度的调查,估算了建库48年来底泥的蓄积量,并探讨了水库底泥中营养盐的空间分布特征。结果表明,该水库蓄积的底泥总体积约为1 182×104m3,湿重约为1 429×104t,干重为550×104t;底泥中淤积的总氮、总磷的含量分别为31 333、8 528 t。总氮、总磷的水平分布既与其所处的地理环境有关,又反映了湖流作用、入湖河道位置的特点;总氮、总磷含量的垂直分布由底层向悬浮层呈明显的递增趋势,这种垂直变化反映了近年来红枫湖周边地区工业、农业与城市发展对水库水环境的影响。     

准噶尔盆地南缘绿洲景观格局变化分析

根据1989年和2000年2期TM影像,利用遥感和景观生态的研究方法,对准噶尔盆地南缘绿洲景观格局的变化进行了分析。结果表明:研究区域1989~2000年的植被覆盖面积在总面积中所占比例下降了4.90%。时间动态度分析表明,农田>低覆盖度植被>水域>高覆盖度植被>流动沙丘>戈壁滩>中覆盖度,其中农田、水域、高覆盖度植被、低覆盖度植被和流动沙丘都有不同程度的增加,中覆盖度植被和戈壁滩的面积明显减少;绿洲景观破碎化程度在增加;人工绿洲景观趋于完整连片;随着人类干预时间的延长,绿洲景观的类型趋于简单。     

和田河流域不同景观类型下的土壤肥力差异研究

[目的]研究和田河流域不同景观下土壤肥力差异。[方法]通过对和田河流域不同景观下土壤肥力元素含量的测定,总结不同景观土壤肥力的变化规律。[结果]和田河流域各景观间土壤肥力元素具有空间变异性。N、P含量:绿洲>过渡带>荒漠;而由于盐渍化的影响K含量:荒漠>过渡带>绿洲。土壤养分分布是由结构性因素和随机性因素共同作用的结果。[结论]为和田河流域生态环境的治理和资源合理开发提供依据。     

潮白河上游1961—2005年径流变化趋势及原因分析

基于潮白河上游流域内的气象资料和水文资料,利用时间序列对比法分析了1961—2005年该流域年径流变化特征和变化趋势,研究了气候变化和人类活动因素对径流变化的影响,揭示了流域径流变化的成因。结果表明:潮白河上游径流的年内分配极不平衡,年际变化大;年径流量总体上呈现出明显减少的趋势,20世纪90年代的流域径流量平均值仅为60年代的75.8%,减少幅度较大。通过分析认为:降水、气温变化不是造成年径流量显著下降的主要影响因素,流域径流量的减少在很大程度上受水资源利用、土地利用、修建水库以及跨流域调水等人类活动因素的影响。     

三峡库区饲草玉米(SAUMZ1)的生物学特性与栽培模式

在对三峡库区生态环境与饲草玉米（SAUMZ1）生态适应性分析基础上,进行了不同海拔高度饲草玉米越冬保种、无性繁殖与生物学特性观测等试验,提出了三峡库区饲草玉米的栽培模式。结果表明：饲草玉米适宜于三峡库区栽植与利用,能在三峡库区生态环境建设及退耕还草养畜工程中大力推广应用。     

Reservoir operation management through optimization and deficit irrigation

One of the methods for increasing productivity of water consumed in agriculture is by improved water supply management. This paper presents results from an optimization study of the Malampuzha irrigation project of the Bharathapuzha river basin of Kerala in India. The objective of this study is to determine whether significant improvements might be realized from optimization of operation of the reservoir system. To do this a mixed integer linear programming (MILP) model is developed and five different management strategies are tested. The result indicates that a management strategy with deficit irrigation by supplying less water in non-critical growth period and maximum water during stress sensitive periods is a best viable solution for better performance. A MILP model, rather than a linear programming (LP) model, is used to ensure that the reservoir does not spill before reaching its capacity.     

Simulated long-term nitrogen losses for a midwestern agricultural watershed in the United States

Adequate knowledge on the movement of nutrients under various agricultural practices is essential for developing remedial measures to reduce nonpoint source pollution. Mathematical models, after extensive calibration and validation, are useful to derive such knowledge and to identify site-specific alternative agricultural management practices. A spatial-process model that uses GIS and ADAPT, a field scale daily time-step continuous water table management model, was calibrated and validated for flow and nitrate-N discharges from a 365 ha agricultural watershed in central Iowa, in the Midwestern United States. This watershed was monitored for nitrate-N losses from 1991 to 1997. Spatial patterns in crops, topography, fertilizer applications and climate were used as input to drive the model. The first half of the monitored data was used for calibration and the other half was used in validation of the model. For the calibration period, the observed and predicted flow and nitrate-N discharges were in excellent agreement with r² values of 0.88 and 0.74, respectively. During the validation period, the observed and predicted flow and nitrate-N discharges were in good agreement with r² values of 0.71 and 0.50, respectively. For all 6 years of data, the observed annual nitrate-N losses of 26 kg ha⁻¹ for the entire simulation were in excellent agreement with predicted nitrate-N losses of 24.2 kg ha⁻¹. The calibrated model was used to investigate the long-term impacts of nitrate-N losses to changes in the rate and timing of fertilizer application. Results indicate that nitrate-N losses were sensitive to rate and timing of fertilizer application. Modeled annual nitrate-N losses showed a 17% reduction in nitrate-N losses by reducing the fertilizer application rate by 20% and switching the application timing from fall to spring. Further reductions in nitrate-N losses require conversion of row cropland to pasture and/or replacement of continuous corn or corn–soybean rotation systems with alternative crops.