地理生态学的干燥度指数及其应用评述

 干燥度指数（Aridity index，AI，该文特指气候干燥度）是表征一个地区干湿程度的指标，在地理学和生态学研究中长期应用，近来成为全球变化研究中经常涉及到的气候指标之一，尤其是气候变化和干旱化、荒漠化等研究。该文列举了国内外目前存在的22种干燥度指数，并对目前常用的8种指数进行了详细描述和分析，包括各自的原理、计算方法和在生态学与地理学研究中的应用等。结合其应用和中国的实际状况，分析了各自的优缺点，认为修改后的谢氏干燥度、de Martonne干燥度和Holdridge可能蒸散率（等同于某种意义上的干燥度）计算方法简单实用，有着明确的物理学和生态学意义，与我国的实际情况对应性较强，适合于中国气候变化及其相关的干旱化、荒漠化等方面的研究。  

干旱、CO2和温度升高对春小麦光合、蒸发蒸腾及水分利用效率的影响

研究了干旱、CO2 浓度和温度升高对春小麦生育期、光合速率 (Pn)、蒸发蒸腾 (ET)及水分利用效率 (WUE)的影响 .结果表明 ,大气CO2 浓度升高 (5 5 0、70 0 μmol·mol-1)虽可延长抽穗 成熟期 ,但高温 (日平均温度高于正常日平均温度约 4 .8℃ )对生育期的影响远大于高CO2 影响 ,使得高CO2 、高温下抽穗 成熟期缩短 ,且种子提前萌发 ;CO2 浓度升高和高温共同作用使各水分处理的小麦光合增强、气孔阻力增加、叶片水平的水分利用效率 (WUEl)和群体水平的水分利用效率 (WUE)增大 ,但对蒸腾速率影响不显著 .对蒸发蒸腾的影响因不同的土壤水分而不同 ,在高 (田间持水量的 75 %～ 85 % )、中 (田间持水量的 5 5 %～6 5 % )水分条件下 ,高温和高CO2 使蒸发蒸腾增加 ,而在低水分条件 (田间持水量的 35 %～ 4 5 % )下 ,高温和高CO2 使蒸发蒸腾减少  

森林蒸散测算方法研究进展与展望

对目前国内外森林蒸散研究中的主要理论和方法（蒸渗仪法、风调室法、涡动相关法、水量平衡法、能量平衡法、波文比法、彭曼联合法、SPAC法、经验公式法和应用遥感数据的方法）进行了总结，探讨了其实际应用中所存在的问题，简单介绍了应用闪烁计数器直接观测显热通量以及应用双频微波辐射计探测大气水汽、云中液态水含量的技术，提出通过对大气水汽平衡的研究来推求蒸散量的设想，预测了森林散研究的发展趋势。  

草原区不同植物群落蒸发蒸腾的研究

 在中国科学院内蒙古草原生态系统定位研究站，采用“土柱称重法”对典型草原群落蒸发蒸腾进行实验观测，主要研究结果如下：1．草原沙地、羊草草原和河漫滩草甸是本地区差异明显的三种群落。草甸蒸腾最大(9.2 mm·d-1)，比另两种群落高2—3倍；草甸蒸发最小(0.4mm·d-1)，约为沙地的1／4，草原 的l／8。2．羊草草原在本区分布广，大针茅草原是本区半干旱地带性代表。由于这两种群落主要有关背景值的不同，羊草群落蒸散值(4.4—5.Omm·d-1)明显高于大针茅群落(3.5—3.8 mm·d-1)，而且羊草群落的T／E1)值(～2)也明显大于大针茅(～1)。在生长季节中，羊草草原蒸散随气温升高而升高，在盛夏达最高值，然后随气温降低而降低。然而由于降雨变化的影响，羊草草原蒸发蒸腾的季节变化时而出现较大幅度的波动。3．根据1989年实测的降水和羊草群落蒸发蒸腾的季节变化，分析羊草群落的水分收支，可以看到实验区羊草草原的水分收支是大体平衡的。  

草坪蒸散研究进展

草坪蒸散量是指导草坪合理灌溉的重要指标。自20世纪中叶以来，以节水为目的的草坪蒸散研究越来越受到人们的重视。草坪蒸散研究的内容主要包括相互关联的3个方面：草坪蒸散率的测定与比较，草坪蒸散机制的研究和草坪节水灌溉的研究。草坪蒸散率在不同草种间存在不同程度的差异。暖季型草坪草和冷季型草坪草相比普遍具有较低的草坪蒸散率。暖季型草坪草的夏季日平均最大蒸散率为3.0-9.0mm，而冷季型草坪草的为3.6-12.6mm。密度大，生长缓慢的杂交狗牙根、结缕草、野牛草和假俭草的耗水量很低，细羊茅的耗水量中等，而草地早熟禾、高羊茅、1年生早熟禾和匍匐剪股颖的耗水量很大。同种草坪草的不同品种的草坪蒸散率存在差异。有些草种内品种间差异的程度高达64％，不亚于种间。冷季型草坪草品种的蒸散率与留茬量显著相关，但环境因子对品种的蒸散率影响很大，品种的蒸散特性不稳定。与冷季型草坪草相比，暖季型草坪草的种内品种间蒸散率的差异和谐较小。草坪的冠层是草坪蒸散的一个主要外部条件，具有较低蒸散率的草坪往往具备高冠层阻力和低叶面积。土壤水分不受限制时，不同的暖季型草坪草种间的草坪蒸散率与叶片背面的气孔密度显著负相关。但在种内品种间没有表现出相关性。冷季型草坪草种间和种内的叶片气孔数目和草坪的蒸散率不相关。草坪的作物系数是确定最适灌溉量的关键参数，线性梯度灌溉系统比小型蒸渗仪提供的草坪作物系数更接近于实际。当草坪的质量维持在可接受的水平时，以彭曼公式推测的苜蓿的潜在蒸散量为参照蒸散量，高羊茅草坪的作物系数为0.60-0.80，草地早熟禾草坪的作物系数为0.50-0.80。基于草坪冠层温度的作物水分胁迫系数（CWSI）是确定灌溉时机的比较合理的指标。CWSI在不同的季节和不同的草种间表现不稳定，并且这种方法的节水效果也表现不一，还处于发展阶段。草坪蒸散的研究在我国几乎处于空白状态，开展我国的草坪蒸散研究，寻求适合的草坪节水途径已势在必行。  

黄土区防护林主要造林树种水分供需关系研究

通过3年的定位观测，分析了晋西黄土区护林主要造林树种刺槐和油松寺地供水与耗水关系，油松和刺槐林地4－6月林地水分消耗大于供给，供耗矛盾突出；雨季水分供应充足，土壤贮水增加；相同条件下密度大的林分耗水量较大，在干旱季节和年份，相同条件下，密度大的林分林地有效供水较少，林地水分亏损较为严重；不同坡向的水分缺量大小顺序为阳坡＞半阳坡＞阴坡，本文引入耗水特性系数来表示林分耗水的大小和需水量的满足程度，研究表明，用耗水特性系数表示林木规律和水分供耗关系是适合的衡量指标。  

全球变化的中国气候-植被分类研究

区域潜在蒸散具有作为植被－气候相关分析与分类的综合气候指标的功能。根据区域潜在蒸散对气候－植被分类的热量与水分指标进行了初步探讨，并对中国气候－植被分类进行了初步的定量研究。根据该模式对中国陆地生态系统对全球变化的反应进行了探讨，结果表明我国自然植被在气温增加２℃或４ ℃、降水增加２０％ 时， 森林和草原的面积都有所减少，且随着温度的升高而减少，沙漠化趋势增强。特别是青藏高原地区对全球气候变化非常敏感，因而可以作为全球变化的先兆区或预警区，具有重要的监测和研究意义  

林地生态需水量计算方法与应用

从树木生长强度与土壤水分含量、蒸散量的相互关系出发 ,提出了林地生态需水量的等级标准和 计算方法 ,并以黄淮海地区为例 ,采用ＧＩＳ技术对该地区林地生态需水量进行了估算 ,分析了该地区林地在现状用水状况下的生态缺水量 .结果表明 ,该地区林地年生态需水量约 2 . 56× 1 0 1 0 ～ 4. 58× 1 0 1 0 ｍ3,在满足最小生态需水量要求下林地缺水量约为 2 .8× 1 0 9ｍ3,在满足适宜性生态需水要求下林地缺水量约为8.4× 1 0 9ｍ3.  

A multi-scale perspective of water pulses in dryland ecosystems: climatology and ecohydrology of the western USA

In dryland ecosystems, the timing and magnitude of precipitation pulses drive many key ecological processes, notably soil water availability for plants and soil microbiota. Plant available water has frequently been viewed simply as incoming precipitation, yet processes at larger scales drive precipitation pulses, and the subsequent transformation of precipitation pulses to plant available water are complex. We provide an overview of the factors that influence the spatial and temporal availability of water to plants and soil biota using examples from western USA drylands. Large spatial- and temporal-scale drivers of regional precipitation patterns include the position of the jet streams and frontal boundaries, the North American Monsoon, El Niño Southern Oscillation events, and the Pacific Decadal Oscillation. Topography and orography modify the patterns set up by the larger-scale drivers, resulting in regional patterns (10²–10⁶ km²) of precipitation magnitude, timing, and variation. Together, the large-scale and regional drivers impose important pulsed patterns on long-term precipitation trends at landscape scales, in which most site precipitation is received as small events (<5 mm) and with most of the intervals between events being short (<10 days). The drivers also influence the translation of precipitation events into available water via linkages between soil water content and components of the water budget, including interception, infiltration and runoff, soil evaporation, plant water use and hydraulic redistribution, and seepage below the rooting zone. Soil water content varies not only vertically with depth but also horizontally beneath versus between plants and/or soil crusts in ways that are ecologically important to different plant and crust types. We highlight the importance of considering larger-scale drivers, and their effects on regional patterns; small, frequent precipitation events; and spatio-temporal heterogeneity in soil water content in translating from climatology to precipitation pulses to the dryland ecohydrology of water availability for plants and soil biota.  

Litter mass loss rates in pine forests of Europe and Eastern United States: some relationships with climate and litter quality

The purpose of this study was to relate regional variation in litter mass-loss rates (first year) in pine forests to climate across a large, continental-scale area. The variation in mass-loss rate was analyzed using 39 experimental sites spanning climatic regions from the subarctic to subtropical and Mediterranean: the latitudinal gradient ranged from 31 °N to 70 °N and may represent the the largest geographical area that has ever been sampled and observed for the purpose of studying biogeochemical processes. Because of unified site design and uniform laboratory procedures, data from all sites were directly comparable and permitted a determination of the relative influence of climateversus substrate quality viewed from the perspective of broad regional scales. Simple correlation applied to the entire data set indicated that annual actual evapotranspiration (AET) should be the leading climatic constraint on mass-loss rates (R_adj ² = 0.496). The combination of AET, average July temp. and average annual temp. could explain about 70% of the sites' variability on litter mass-loss. In an analysis of 23 Scots pine sites north of the Alps and Carpatians AET alone could account for about 65% of the variation and the addition of a substrate-quality variable was sufficiently significant to be used in a model. The influence of litter quality was introduced into a model, using data from 11 sites at which litter of different quality had been incubated. These sites are found in Germany, the Netherlands, Sweden and Finland. At any one site most ( ≫ 90%) of the variation in mass-loss rates could be explained by one of the litter-quality variables giving concentration of nitrogen, phosphorus or water solubles. However, even when these models included nitrogen or phosphorus even small changes in potential evapotranspiration resulted in large changes in early-phase decay rates. Further regional subdivision of the data set, resulted in a range of strength in the relationship between loss rate and climatic variables, from very weak in Central Europe to strong for the Scandinavian and Atlantic coast sites (R_adj ² = 0.912; AETversus litter mass loss). Much of the variation in observed loss rates could be related to continentalversus marine/Atlantic influences. Inland locations had mass-loss rates lower than should be expected on the basis of for example AET alone. Attempts to include seasonality variables were not successful. It is clear that either unknown errors and biases, or, unknown variables are causing these regional differences in response to climatic variables. Nevertheless these results show the powerful influence of climate as a control of the broad-scale geography of mass-loss rates and substrate quality at the stand level. Some of these relationships between mass-loss rate and climatic variables are among the highest ever reported, probably because of the care taken to select uniform sites and experimental methods. This suggest that superior, base line maps of predicted mass-loss rates could be produced using climatic data. These models should be useful to predict the changing equilibrium litter dynamics resulting from climatic change.