Quantifying microbial biomass phosphorus in acid soils

 This study aimed to validate the fumigation-extraction method for measuring microbial biomass P in acid soils. Extractions with the Olsen (0.5 M NaHCO₃, pH 8.5) and Bray-1 (0.03 M NH₄F–0.025 M HCl) extractants at two soil:solution ratios (1 : 20 and 1 : 4, w/v) were compared using eight acid soils (pH 3.6–5.9). The data indicated that the flushes (increases following CHCl₃-fumigation) of total P (P_t) and inorganic P (P_i) determined by Olsen extraction provided little useful information for estimating the amount of microbial biomass P in the soils. Using the Bray-1 extractant at a soil:solution ratio of 1 : 4, and analysing P_i instead of P_t, improves the reproducibility (statistical significance and CV) of the P flush in these soils. In all the approaches studied, the P_i flush determined using the Bray-1 extractant at 1 : 4 provided the best estimate of soil microbial biomass P. Furthermore, the recovery of cultured bacterial and fungal biomass P added to the soils and extracted using the Bray-1 extractant at 1 : 4 was relatively constant (24.1–36.7% and 15.7–25.7%, respectively) with only one exception, and showed no relationship with soil pH, indicating that it behaved differently from added P_i (recovery decreased from 86% at pH 4.6 to 13% at pH 3.6). Thus, correcting for the incomplete recovery of biomass P using added P_i is inappropriate for acid soils. Although microbial biomass P in soil is generally estimated using the P_i flush and a conversion factor (k _P) of 0.4, more reliable estimates require that k _P values are best determined independently for each soil. Received: 3 February 2000     

黄土高原水土流失区森林资源价值核算

概述了目前常用的森林资源价值核算方法,较系统、全面地核算了黄土高原水土流失区森林资源环境价值(包括涵养水源价值、保育土壤价值、固碳制氧价值、景观游憩价值和净化环境污染价值)和实物价值(包括林地价值、林木和果品价值)的现值,并且分析了不同贴现率时森林资源价值的差异,指出基于可持续发展的需要,应取低贴现率进行森林资源价值核算。同时计算结果表明,森林资源环境价值是森林资源价值的主要部分,充分说明了森林环境价值的重要性,应该引起人们的高度重视。     

典型黑土pH值变化对营养元素有效态含量的影响研究

采用室内培养实验的方法,控制典型黑土样品的酸碱度值,探讨典型黑土中Cu、Zn、Mn、P和Fe等营养元素有效态含量与pH值的关系。结果表明:pH值变化0.5个单位左右,有效态铜含量变化约0.5～1倍;有效态锰含量变化约3～5倍;有效态锌含量变化9～15倍之多;有效态磷含量变化约1.5～2倍;有效态铁含量变化约3～4倍。说明精确掌握土壤的酸碱度值对于土壤诊断、合理施肥、提高作物产量和实现土地的可持续利用都具有重要的理论与实践意义。     

飞来峡水利枢纽水保工程监测内容和方法设计

通过对黄土高原水土保持世行贷款项目实施后土壤养分、pH和阳离子代换量变化的分析，研究了水土保持措施对土壤化学特性的影响。结果表明，坡耕地和荒坡地的土壤养分含量基本不随时间变化，而有措施地块的土壤养分含量随时间推移而递增；有措施较无措施地块的土壤养分含量增加，pH向中性变化；阳离子代换量增加。     

酸性硫酸盐土酸消长的水动力机制研究

以不同土壤湿度、不同干湿交替周期和原状土自然风干 8个处理进行酸性硫酸盐土 (简称ASS)室内模拟实验。通过对模拟过程内土壤pH、总硫化物性酸度和未氧化双氧水可氧化硫、交换性酸度、硫派生的实际酸度、KCl可提取硫等指标的动态变化过程的跟踪测定和分析显示 ,土壤水分条件是制约ASS酸度及酸形态转化的重要动力机制 ,可导致ASS酸度和酸形态的有规律变化。ASS产酸量和洗酸量受干湿交替周期制约     

温度对酸性草酸-草酸铵溶液浸提土壤无定形铁的影响

以下蜀黄土为试材,研究温度对酸性草酸-草酸铵缓冲溶液浸提土壤无定形铁的影响。结果表明:随着浸提温度的升高,铁的浸提量明显增加。30℃浸提出的铁约为20℃的1.57倍;而50℃浸提出的铁约为20℃的4.43倍。随温度的升高,浸提后土壤残渣的磁化率迅速降低。20℃浸提后残渣的磁化率值比原样略有减少;30℃浸提后残渣的磁化率约为原样的93.6%;50℃浸提后残渣的磁化率只有原样的65.3%。这说明随着温度的升高,以磁性矿物为代表的结晶态铁也被溶解,浸提出的铁其实已不仅是无定形铁。因此,用酸性草酸铵浸提无定形铁时,严格控制20℃的反应温度十分关键。     

Grazing intensity alters soil respiration in an alpine meadow on the Tibetan plateau

Grazing intensity may alter the soil respiration rate in grassland ecosystems. The objectives of our study were to (1) determine the influence of grazing intensity on temporal variations in soil respiration of an alpine meadow on the northeastern Tibetan Plateau; and (2) characterise the temperature response of soil respiration under different grazing intensities. Diurnal and seasonal soil respiration rates were measured for two alpine meadow sites with different grazing intensities. The light grazing (LG) meadow site had a grazing intensity of 2.55 sheep ha⁻¹, while the grazing intensity of the heavy grazing (HG) meadow site, 5.35 sheep ha⁻¹, was approximately twice that of the LG site. Soil respiration measurements showed that CO₂ efflux was almost twice as great at the LG site as at the HG site during the growing season, but the diurnal and seasonal patterns of soil respiration rate were similar for the two sites. Both exhibited the highest annual soil respiration rate in mid-August and the lowest in January. Soil respiration rate was highly dependent on soil temperature. The Q₁₀ value for annual soil respiration was lower for the HG site (2.75) than for the LG site (3.22). Estimates of net ecosystem CO₂ exchange from monthly measurements of biomass and soil respiration revealed that during the period from May 1998 to April 1999, the LG site released 2040 g CO₂ m⁻² y⁻¹ to the atmosphere, which was about one third more than the 1530 g CO₂ m⁻² y⁻¹ released at the HG site. The results suggest that (1) grazing intensity alters not only soil respiration rate, but also the temperature dependence of soil CO₂ efflux; and (2) soil temperature is the major environmental factor controlling the temporal variation of soil respiration rate in the alpine meadow ecosystem.     

桂牧1号象草营养价值评定及PEG对其产气量的影响

用体外产气法测定了桂牧1号象草不同月份、不同高度的产气量及添加聚乙二醇（PEG）对产气量的影响。结果显示：（1）桂牧1号象草各月份的干物质含量比较为：11月〉10月〉9月〉4月。其中，1．0m左右及1．0m以上的象草的干物质含量明显较高（P〈0．01）。（2）在体外产气法实验中添加PEG能显著增加样品12h和24h的产气量（P〈0．01），证明象草中所含有的抗营养因子对黑山羊瘤胃微生物活动有一定的制约作用。（3）9、11月份象草的最佳刈割高度应为1．5m左右，4、10月份象草的最佳刈割高度应为1．0m左右。（4）4月、9月份的象草，添加PEG后产气量提高率较高。利用此时期的象草喂食黑山羊时，适当做PEG处理可以提高象草的饲用价值。     

土地利用生态系统分析及服务价值估算——以北京市平谷区白各庄村为例

本研究以北京市平谷区白各庄村为例,详细分析了2002年土地利用生态系统的类型和特点,并进行生态系统服务价值核算,包括物质生产、吸收CO2、释放O2、水供给、废物处理和休闲娱乐,其总价值为1706.62万元,与农村经济总收入基本相等,其中吸收CO2的服务价值最大(72.57%),其次为释放O2价值(15.30%),物质生产服务价值仅占总价值的12.77%,水供给和休闲娱乐服务价值很小,而废物处理服务价值为负值。     

黄土高原生态系统演替进程中土壤有机质和pH值变化规律

通过对黄土高原生态系统演替进程中土壤有机质和pH值变化进行分析,结果表明:在同一演替系列中,随演替进程的推移,土壤中有机质增加,pH值减小;在不同地段上,演替高级阶段土壤的有机质高于低级阶段,pH值正好相反;人为间断干扰的生态系统土壤有机质下降,pH值升高;人为持续干扰的亚顶级生态系统土壤有机质明显降低,PH值明显升高.