毛乌素沙地西南缘不同植被下的土壤水分时空变化研究

在一个生长季内通过对毛乌素沙地不同植被下土壤水分的连续观测,研究毛乌素沙地不同植被下的土壤水分时空动态变化规律。结果表明:各样地土壤含水量生长期末低于生长期初,按时间变化可划分为3个时期,土壤水分积累期（4-6月）、土壤水分消耗期（7-9月）、土壤水分稳定期（10月至次年3月）。在空间上,各样地土壤含水量均随深度的增加而增加,整个土壤剖面自上而下按水分变化规律可划分为4层:土壤水分速变层、活跃层、过渡层和稳定层。土壤水分活跃层的深度与根系分布层密切相关,深根系的植物其水分活跃层分布较深。固定沙丘不同部位的土壤含水量及其变化规律不同,土壤含水量从大到小依次为坡脚>坡腰>坡顶。     

不同母质红壤和水分条件对连翘生长的影响

[目的] 在南方红壤侵蚀区不同母质发育红壤上种植和筛选适宜生长的连翘属植物生长特性,旨在为连翘资源的规模扩大和推广种植提供科学依据。[方法] 以连翘、金钟花和垂枝连翘为试材,通过人工控水试验在3种母质红壤（花岗岩红壤、红砂岩红壤和第四纪红壤）设计3个水分处理（20 cm深度处土壤基质势控制在-5,-20,-35 kPa）,研究不同母质和水分条件对3种连翘属植物生长的影响规律。[结果] ①在3种水分处理条件下,花岗岩红壤种植的连翘属植物,其灌水次数和灌水量最少;第四纪红壤种植的连翘属植物,在-5 kPa水分条件下,其灌水量和灌水次数,与红砂岩红壤相同,在-20 kPa和-35 kPa水分条件下,均高于红砂岩红壤。②土壤水分和土壤类型均显著影响连翘属植物的生长发育,而连翘品种之间却无显著差异;除了土壤水分—连翘品种的交互作用对枝条长度无显著影响外,其他土壤类型、土壤水分、连翘品种之间的双因素交互作用,对连翘属植物生长指标均具有极显著影响。3种连翘属植物中,在高水分条件下（-5 kPa）,连翘、金钟花在红砂岩红壤上生长最佳,垂枝连翘在第四纪红壤上生长最佳;随着水分含量下降（-20 kPa和-35 kPa）,3种连翘属植物均在第四纪红壤上生长得更好。[结论] 在适宜水分条件下（20 cm深度处土壤基质势>-35 kPa）,连翘、金钟花和垂枝连翘在南方红砂岩红壤和第四纪红壤上引种种植是可行的。     

毛乌素沙地西南缘不同植被下的土壤水分时空变化研究

在一个生长季内通过对毛乌素沙地不同植被下的土壤水分的连续观测,研究毛乌素沙地不同植被下的土壤水分时空动态变化规律。结果表明：各样地土壤含水量生长期末低于生长期初,按时间变化可划分为三个时期,土壤水分积累期（4～6月）、土壤水分消耗期（7～9月）、土壤水分稳定期（10月至次年3月）。在空间上,各样地土壤含水量均随深度的增加而有所增加,整个土壤剖面自上而下按水分变化规律可划分为四层：土壤水分速变层、活跃层、过渡层和稳定层。土壤水分活跃层的深度与根系分布层密切相关,深根系的植物其水分活跃层分布较深。固定沙丘不同部位的土壤含水量及其变化规律不同,土壤含水量从大到小依次为：坡脚〉坡腰〉坡顶。     

广东丘陵红壤土壤水分性能特征比较研究

对不同植被、不同利用方式下广东丘陵红壤水分性能进行了比较研究.结果表明,与自然地带性植被下的赤红壤比较,次生植被、人工植被下红壤类土壤导水性、持水能力和供水能力一般均较低.在同样的吸力下,次生植被、人工植被下红壤类土壤持水量较少,在同样吸力段.土壤释放的水量较少.玄武岩砖红壤持水量较大,但土壤水分有效性低.研究表明.广东丘陵旱地土壤局部干旱的发生,与其本身的土壤水分性能有密切关系,改良土壤水分性状,是调控广东丘陵旱地土壤水分的重要环节.     

福建赤红壤旱地土壤水分特性及调控

福建不同母岩上发育的赤红壤旱地土壤水总库容在熟化度大致相当的情况下相差不大。玄武岩上发育的赤红壤旱地贮水库容、有效水库容分别比花岗岩发育的赤红壤旱地贮水库容、有效水库容要高 ,前者的保水性强于后者。不同利用方式主要通过影响土壤的有机质状况及熟化度 ,进而影响土壤结构 ,导致土壤持水容量不同。赤红壤旱地的比水容量达到 10 2 数量级在 - 10kPa～ 30kPa就开始出现 ,而红壤旱地出现在- 30kPa以下 ,表明赤红壤旱地的失水速度快 ,保水供水性能弱于红壤旱地。为此 ,福建省赤红壤旱地土壤水分调控管理的方向和措施有 :增加降水入渗、调整农业结构 ,采用复合农业技术、增施有机肥和改进灌溉等。     

不同利用方式下红壤坡地土壤水分时空动态变化规律研究

利用连续3年土壤水分定位观测数据，研究了红壤坡地不同利用方式下土壤水分的时空动态变化规律。结果表明：土壤水分时空动态变化主要受降雨和植被类型的影响。土壤水分季节变化分为相对稳定期、消耗期和补给期三个时段；土壤剖面（0～90cm）水分含量从表层到深层表现为增长型，依据2003年土壤水分标准差和变异系数。将土壤剖面划分为活跃层、次活跃层和相对稳定层3个层次；土壤剖面水分变异系数随降雨量和土层深度的增加而减小，随植被根系的增长而变大。平水年，深根系区与浅根系区土壤水分变化差异表现在30cm深度以下，而丰水年其差异主要表现在土壤表层（0～30cm）；无论平水年还是丰水年，深根系区土壤水分变幅均比浅根系区大。     

江西红壤在系统分类中的参比特征研究

在江西省选取了由花岗岩、泥页岩和红砂岩发育的46个典型红壤剖面,在明确剖面形态特征及理化性质的基础上,依据《中国土壤系统分类检索(第三版)》确定了其在中国土壤系统分类中的归属,由此讨论了不同纬度带下,红壤与中国土壤系统分类单元参比关系以及气候和母质对所划分出的系统分类单元的影响。结果表明,46个典型红壤共划分为3个土纲、3个亚纲、6个土类和14个亚类,其中江西省纬度28°N以北主要归属于湿润淋溶土,26°N以南主要归属于湿润富铁土,26°～28°N赣中地区,花岗岩发育的土壤主要归属于湿润富铁土,发育于泥页岩、红砂岩的典型红壤主要归属于湿润雏形土。     

低山丘陵区红壤水分的动态变化及影响因素

红壤分布区域是中国重要的粮食产地,但是降水时空分布的不均匀导致了季节性干旱的发生。因此,了解红壤中水分时空分布规律具有十分重要的意义。该文研究了低山丘陵区红壤旱地不同肥料配比长期试验小区土壤含水率的季节性变化状况及其与气象因素的关系,分析了典型红壤地区的土壤水分变化规律。结果表明：研究区1 a内的土壤含水率变化分为4个阶段：土壤水分充盈期、土壤水分亏缺期、土壤水分补充恢复期和土壤水分平稳期。空白小区土壤含水率变化较大;在施用肥料的试验小区中,蒸发对氮肥小区、氮磷小区和氮磷钾小区的影响逐渐降低;而降雨对氮肥小区、氮磷小区和氮磷钾小区的影响力逐渐增加。通过掌握典型红壤地区的土壤水分变化规律,对该地区水资源的调配管理、灌溉安排及干旱评估均可起到重要的指导作用。     

渭北黄土高原刺槐林-草地景观界面土壤水分影响域及其动态变化规律研究

对渭北黄土高原刺槐林—草地景观界面土壤水分影响域及其时空动态变化规律进行了研究。采用移动窗口法分析得出刺槐林—草地景观界面土壤水分影响域为林内4 m到林外12 m之间,宽度16 m,为渐变型界面,由此可将刺槐林—草地景观划分为3个区域：草地区、界面区和刺槐林区。经典统计分析表明,历经3个区域,不同层次的土壤水分在水平方向上随着水平距离梯度的变化表现出不同的上升或下降的趋势,在界面区域土壤含水量变化最为显著。基于标准差和变异系数两个指标,可将草地和林地区域土壤剖面水分垂直变化划分为4层,界面区域划分为3层。3个区域土壤含水量的季节变化表现为基本一致的“高-低-高”规律,可以划分为3个时期,4～5月中旬为土壤水分贮存期,6～7月中旬为土壤水分消耗期,8～10月中旬土壤水分恢复期。水分在时间和空间上的这种变化主要受植被类型、根系分布、降水资源再分配的影响。     

不同水保措施下红壤坡耕地浅层土壤水分含量对降雨的响应

为探明次降雨条件下花生不同生长期红壤坡耕地土壤水分含量变化对水保措施的响应,利用人工模拟降雨试验,研究采取常规耕作、有机肥+常规耕作、稻草覆盖+深翻耕、保水剂+常规耕作等措施的红壤坡耕地小区20 cm深度层土壤水分含量在次降雨过程(1.5 h)及降雨结束后1 h内的连续变化规律。结果表明:花生不同生长期红壤坡耕地上、下坡20 cm深度土壤含水量在降雨后的变化幅度均呈收获期≈结荚期盛花期出苗期翻耕期(p0.01)。稻草覆盖+深翻耕措施在提高红壤坡耕地土壤蓄水能力方面效果最显著,尤其是在花生翻耕期和收获期,增幅分别比常规耕作措施高26%和64%。保水剂对红壤坡地土壤保水效果的促进作用主要体现在花生翻耕期,而花生其他生长期则不明显;而有机肥增施措施对红壤坡地土壤保水效果的促进作用主要体现在花生翻耕期、结荚期和收获期。研究结果表明稻草覆盖+深翻是适合红壤丘陵区坡耕地土壤水分持续高效利用的有效模式。     

海南岛土壤粘粒矿物特征与土壤系统分类

研究了海南岛不同母质土壤的粘粒矿物特征:都含有较多的高岭石,其中玄武岩发育土壤粘粒中高岭石最多,但其结晶最差。片岩和紫色砂岩发育土壤含相当多的水云母,粘粒部分水云母含量高达40％～45％,石灰岩发育土壤水云母含量亦较高,达20％～37％,此类水云母属二八面体型的水化白云母。玄武岩和花岗岩发育的“湿润”土壤粘粒中针铁矿与赤铁矿的含量之比为（3～4）:1,而花岗岩发育的“常湿”土壤粘粒中只有针铁矿,不见赤铁矿存在,证明土壤中氧化铁矿物的类型是土壤湿润状况的反应,在中国土壤系统分类中可以用来区分“湿润”和“常湿”土壤的一个指标。     

不同水分状况及施磷量对水稻土中速效磷含量的影响

通过室内培养试验研究了不同水分(淹水和60%田间持水量)及施P量对水稻土速效P及水层含P量的影响。结果表明,无论水分状况如何,土壤速效P含量随施P量的增加而呈明显增加趋势。土壤速效P出现富集的转折点因供试土壤而异,第三纪红壤性水稻土大致为P2O560~120mg/kg,而第四纪红壤性水稻土和黄泥土为P2O5120~180mg/kg。P肥施入土壤后,水溶性P主要存在于土壤溶液中,而分布于水层中的P相对较少。但在过量施P(P2O5>180mg/kg)时,施肥后短期内(0~30天),水层中P浓度较高(0.05~0.3mg/kg),如水分管理不当,则会造成P的损失。     

梅江盆地叶塘组紫色岩上发育土壤的物理性质研究

采用野外调查、取样和室内实验分析相结合的方法,研究了梅江盆地白垩系上统叶塘组（Kyt^2）紫色岩上土壤物理性质特征扣差异,结果表明：叶塘组紫色岩母质发育的土壤粘粒含量低而砂粒含量高,具有容重较大,比重相对偏小,孔隙度不高,自然含水量偏低的特点。从丘顶、丘腰到丘脚,土层逐渐增厚,土壤粘粒含量逐渐增加,砂粒含量逐渐减少,容重递增而比重减小。孔隙度表现出丘顶〉丘腰〉丘脚的趋势,含水量则表现出丘顶〈丘腰〈丘脚的趋势。针对情况,提出相应建议以维护紫色土利用的可持续发展。     

南方丘陵区三种母质水耕人为土有机碳的累积特征与影响因素分析

本研究分析了南方丘陵区3种母质水耕人为土有机碳的累积特征与影响因素。结果表明：紫色砂页岩和第四纪红黏土母质的水耕人为土在发育过程中有机碳较易累积,在种稻初期土壤有机碳的增加主要集中在耕作层,到一定阶段后下层(耕作层以下)也明显增加;相比之下,红砂岩母质的水耕人为土在发育过程中有机碳较难累积。利用逐步回归方法得到的丘陵区水耕人为土耕作层有机碳动态变化模型表明丘陵区水耕人为土有机碳的动态变化主要受细颗粒(黏粒+细粉粒)的影响。     

CO2 emissions from subtropical arable soils of China

CO₂ efflux plays a key role in carbon exchange between the biosphere and atmosphere, but our understanding of the mechanism controlling its temporal and spatial variations is limited. The purpose of this study is to determine annual soil CO₂ flux and assess its variations in arable subtropical soils of China in relation to soil temperature, moisture, rainfall, microbial biomass carbon (MBC) and dissolved organic carbon (DOC) using the closed chamber method. Soils were derived from three parent materials including granite (G), tertiary red sandstone (T) and quaternary red clay (Q). The experiment was conducted at the Ecological Station of Red Soil, The Chinese Academy of Sciences, in a subtropical region of China. The results showed that soil CO₂ flux had clear seasonal fluctuations with the maximum value in summer, the minimum in winter and intermediate in spring and autumn. Further, significant differences in soil CO₂ flux were found among the three red soils, generally in the order of G>T>Q. The average annual fluxes were estimated as 2.84, 2.13 and 1.41 kg CO₂ m⁻² year⁻¹ for red soils derived from G, T and Q, respectively. Soil temperature strongly affects the seasonal variability of soil CO₂ flux (85.0-88.5% of the variability), followed by DOC (55.8-84.4%) and rainfall (43.0-55.8%). The differences in soil CO₂ flux among the three red soils were partly explained by MBC (33.7-58.9% of the variability) and DOC (23.8-33.6%).     

植被恢复过程中侵蚀红壤有机质变化研究

基于2001年与2011年两期土壤样品数据,对江西省兴国县植被恢复过程中侵蚀红壤有机质的变化进行了研究。结果表明：10年间,纯林、林草及林灌草结构下表层(0 ~ 10 cm)土壤有机质变化值分别为?-5.8、-0.1及8.0 g/kg,千枚岩、红砂岩及花岗岩成土母质发育的红壤表层土壤有机质变化值分别为8.7、-0.5及 -3.1 g/kg。植被垂直结构对表层土壤有机质的变化影响显著,主要是由于植被覆盖度及生物量的不同引起的凋落物量的差异所导致;土壤颗粒组成是表层土壤有机质变化的重要影响因素之一,研究区表层土壤有机质的变化与黏粒含量的变化呈显著正相关(P < 0.05);此外,林下土壤侵蚀也影响着表层土壤有机质的变化。     

江西省农田土壤有效硫现状研究

采集了江西 1 6个县市 9种主要母质的 6 0 9个农田耕层土样进行了土壤有效硫含量测定 .统计结果表明 :平均值为 2 6 7mg/kg ,缺硫和潜在缺硫样点占 39 1 % .按地区分 ,以赣南、赣东北山区缺硫最严重 ,有效硫小于 1 2mg/kg的样点占 2 6 6 %～ 4 4 7% ,其次是丘陵地区 ,有效硫小于 1 2mg/kg的样点占1 0 0 %～ 1 9 0 % .按母质分 ,以石英岩、花岗岩发育的土壤最缺 ,约占 50 %～ 6 0 % ,其次是红砂岩、泥质岩 ,缺硫为 30 %～ 4 0 % ,这些是江西省急需施用硫肥的土壤 .水稻土以黄砂泥田、麻砂泥田、红砂泥田、鳝泥田等土属有效硫缺乏面积最大 ,全省水稻土有效硫缺乏的面积约为 1 0 3 8万hm2 ,约占水稻土面积的 34 % .     

Genesis of red and dark brown soils on basaltic parent materials near Armidale,N.S.W., Australia

Morphological, physical, chemical and mineralogical data are presented for contiguous euchrozem (nitosols) and chocolate soils (cambisols) developed on basaltic parent materials in the Armidale district of northern New South Wales. The genesis and distribution of the different soils classified at great soil group and series level are related to parent material and topography. The dark brown chocolate soils associated with the modern surface overlie a uniform parent material of partly weathered alkali-olivine basalt. The red euchrozem soils, although having morphological and mineralogical properties associated with intensive weathering and long term soil genesis, have also developed on the modern surface under a moderate leaching regime. They are derived from re-exposed, highly weathered, sesquioxidic, interbasaltic lapilli tuffs and underlying basalt which were probably transformed under a different climate in Pliocene—Pleistocene times. The study showed further that reddish chocolate soils are not necessarily the uppermost member of a sequence of soils developed on partly weathered basalt.     

Changes in variability of soil moisture alter microbial community C and N resource use

Grassland ecosystems contain ∼12% of global soil organic carbon (C) stocks and are located in regions where global climate change will likely alter the timing and size of precipitation events, increasing soil moisture variability. In response to increased soil moisture variability and other forms of stress, microorganisms can induce ecosystem-scale alterations in C and N cycling processes through alterations in their function. We explored the influence of physiological stress on microbial communities by manipulating moisture variability in soils from four grassland sites in the Great Plains, representing a precipitation gradient of 485-1003 mm y⁻¹. Keeping water totals constant, we manipulated the frequency and size of water additions and dry down periods in these soils by applying water in two different, two-week long wetting-drying cycles in a 72-day laboratory incubation. To assess the effects of the treatments on microbial community function, we measured C mineralization, N dynamics, extracellular enzyme activities (EEA) and a proxy for substrate use efficiency. In soils from all four sites undergoing a long interval (LI) treatment for which added water was applied once at the beginning of each two-week cycle, 1.4-2.0 times more C was mineralized compared to soils undergoing a short interval (SI) treatment, for which four wetting events were evenly distributed over each two-week cycle. A proxy for carbon use efficiency (CUE) suggests declines in this parameter with the greater soil moisture stress imposed in LI soils from all four different native soil moisture regimes. A decline in CUE in LI soils may have been related to an increased effort by microbes to obtain N-rich organic substrates for use as protection against osmotic shock, consistent with EEA data. These results contrast with similar in situ studies of response to increased soil moisture variability and may indicate divergent autotrophic vs. heterotrophic responses to increased moisture variability. Increases in microbial N demand and decreases in microbial CUE with increased moisture variability observed in this study, regardless of the soils’ site of origin, imply that these systems may experience enhanced heterotrophic CO₂ release and declines in plant-available N with climate change. This has particularly important implications for C budgets in these grasslands when coupled with the declines in net primary productivity reported in other studies as a result of increases in precipitation variability across the region.     

Effects of soil properties and land management on the structure of grassland snail assemblages in SW Germany

Quantitative analyses of the snail assemblages of four a priori defined categories of grassland sites, characterized by soil moisture, land use and management, were conducted in SW Germany. Topsoil pH and calcium content were determined for each of 39 sites. The objectives were to study the effects of these habitat characteristics on snail density, species richness and quantitative structure of the land snail assemblages. With one exception, no significant relationships between soil pH (as a proxy for Ca supply) and the total numbers of individuals and species at the four site categories were observed. Snail density and species richness on groundwater soils, represented by rarely mown sedge stands and regularly mown meadows, were clearly higher than on intermediate moisture soils (as defined by the climatic water balance) of regularly mown meadows, indicating that soil moisture was the most important factor accounting for these differences. Furthermore, we observed specific conditions associated with the presence of trees in the category of meadow orchards on intermediate moisture soils. There, numbers of individuals and species were significantly higher than in the meadows on intermediate moisture soils. A posteriori cluster analysis of quantitative similarity of all snail assemblages showed that soil moisture accounts for the major differences between the site categories with respect to snail density, species richness and quantitative composition of the grassland snail assemblages. As these results are in contrast to the findings of many woodland studies, we suggest that the occurrence or abundance of certain species in the site categories are explained by land management, especially by frequent disturbances at the soil surface caused by mowing.