川西南山地植被对2009/2010年冬干的响应研究

利用气象资料和卫星遥感资料,初步分析了2009/2010年冬季及2010年初春3月川西南山地植被对2009/2010年冬干的响应。结果表明,季降水评估的气象干旱为中到特旱,气象干旱强度突出;冬季平均温度偏高约2.0℃,冬季平均相对湿度偏少约17.0%。冬季及初春3月土壤相对湿度资料显示气象干旱发生发展趋势为冬季12、1月为轻旱,2～3月发展维持为中旱;冬季及初春3月卫星遥感监测月最大植被指数近5年安宁河平原区域植被指数逐月增加,川西南山地其余区域逐月减小,川西南山地中部及西部林区植被指数最高;植被指数差值分布显示,冬季到初春3月川西南山地2009/2010年冬干由南至北发展,总体上川西南山地南部区域以及安宁河平原区域受旱影响较为显著。     

1982-2010年松花江流域植被动态变化及其与气候因子的相关分析

利用1982-2010年GIMMS和MODIS两种遥感数据集的归一化植被指数（NDVI）数据,分析了松花江流域植被NDVI时空特征及其与气候因子的关系。结果表明,松花江流域植被覆盖存在着显著的空间差异,山区NDVI值明显高于中部平原区。过去29a间,松花江流域植被NDVI稳定性较强,总体上变化趋势不明显,但有明显的阶段性：1982-1990年植被NDVI持续增加;1991-1997年相对稳定,1997-2003年呈波动降低趋势,2003-2010年缓慢上升。基于像元的相关分析表明,松花江流域NDVI与气温和降水量间均具有很强的相关性（P〈0.01）,而且植被NDVI变化受气温影响程度强于降水,针叶林是松花江流域受气温影响最大的植被类型。     

The relationship between local extinctions of grassland butterflies and increased soil nitrogen levels

In contrast to many other western European countries, the knowledge about trends in the Swedish butterfly fauna is poor. We studied the effects of habitat and species characteristics on species turnover in 13 grassland sites in southern Sweden by comparing species richness and compositions at two separate occasions with an interval of 21 years. The mean number of species per site decreased from 30 to 24, with a large variation between sites. The number of extinctions was highest in sites where the proportion of trees and shrubs had increased most, but there was no detectable effect of area or of the composition of landscapes surrounding the sites. Areas protected as nature reserves had lost as many species as unprotected areas had, indicating both the importance of proper management of nature reserves and that nature reserves alone may not be enough to inhibit regional extinction of butterfly species. Species dependent on nutrient-poor conditions tended to decrease while species dependent on nutrient-rich conditions tended to increase, indicating a negative effect of increased soil nitrogen levels resulting from active fertilizing of pastures and/or atmospheric nitrogen deposition. A regular monitoring program could show whether our results are representative for Sweden or Northern Europe.     

Soil nitrogen and denitrification potential as affected by land use and stand age following agricultural abandonment in a headwater catchment

Changes in vegetation and soil properties because of agricultural abandonment may affect soil nitrogen (N) and associated processes. We investigated soil N (total N: TN, inorganic N: NH₄–N and NO₃–N) and denitrification potential in cropland, pine plantations and abandoned agricultural land along a secondary succession sequence (grassland→shrubland→secondary forest) in a headwater catchment in the Qinling Mountains, northwest China. The results show that the soil denitrification potential differed significantly among the five land‐use types with the highest potential in the secondary forest, followed by grassland, shrubland, cropland and plantations. The denitrification potential of the 20‐ to 40‐cm layer was significantly lower compared with the topsoil (0–20 cm) across all land‐use types. TN, soil organic matter (SOM) and NH₄–N increased significantly with stand age, whereas there was an opposite trend in soil pH. However, the denitrification potential did not relate to stand age in a linear manner. We conclude that changes in soil TN, SOM and pH during vegetation succession following agricultural abandonment are critical controls on the denitrification potential.     

Unusual soil nematode communities on karst mountain peaks in southwest China

On karst mountain peaks in southwest China, soils are very shallow and vegetation cover is very low. Although the subtropical monsoon climate provides abundant rainfall, the soils experience severe dry–wet cycles and extremely high temperatures in summer (wet season). We determined the composition of soil nematode communities along a vegetation succession sere of four common plant communities (i.e., moss crust, moss crust with sparse grasses, sparse grasses, and sparse dwarf shrubs) on karst mountain peaks in the wet and dry seasons. The results showed that the nematode communities were unusual. Specifically, Rhabdolaimus was the most abundant nematode genus. Rhabdolaimus is a common aquatic nematode genus that has been detected in hot springs but has not been previously reported as the dominant genus in relatively arid and semi-arid soils. Therefore, tolerance to extremely high soil temperatures and rapid wet–dry cycles may help explain why Rhabdolaimus dominates the nematode communities in the soils of karst mountain peaks in southwest China.     

黄土高原植被恢复过程中土壤表面电化学性质演变特征

土壤胶体表面所带电荷是土壤具有一系列物理、化学性质的根本原因。表面电荷数量、比表面积、表面电荷密度、表面电场强度以及表面电位是土壤胶体颗粒重要性质,影响土壤中物理、化学、生物化学过程。运用带电颗粒表面性质联合分析法,测定黄土高原子午岭地区不同植被类型下土壤表面电荷性质,研究自然植被恢复过程对土壤表面电荷性质的影响。结果表明:随着植被的演替,子午岭林区土壤表面电荷数量、比表面积、表面电荷密度均随植被的恢复增加,变化范围分别为10.88～19.85 cmol·kg^–1、40.67～61.71 m²·g^–1和0.22～0.31 c·m^–2,平均值分别为16.18 cmol·kg^–1、54.88 m2·g^–1和0.28 c·m^–2,土壤表面电场强度达108 V·m^–1数量级;土壤黏粒、有机碳含量是影响表面电荷性质的主要因素,解释率分别为62.5%和27.9%;土壤基本性质对表面电荷性质的影响由强到弱依次为:黏粒、有机碳、...     

阴山北麓缓坡丘陵不同植被类型下土壤水分空间分布特征—以武川县为例

近年来由于农耕面积的进一步扩大,阴山北麓植被破坏程度加深,水蚀风蚀沙化现象日益严重。本文以内蒙古阴山北麓为研究对象,研究了这一地区缓坡丘陵的土壤水分分布特征及不同植被类型下土壤水分时空分布,为这一地区的生态治理过程中,植被类型、种植模式的选择提供数字依据。结果表明:(1)后山地区与内地相反,缓坡丘陵土壤水分以阳坡为最高,阴坡次之,顶部为最低;(2)该地区的土壤水分分布受植被类型等的影响,表现出一定的空间变异特性。     

Factors maintaining species diversity in satoyama, a traditional agricultural landscape of Japan

Satoyama is a traditional agricultural landscape in Japan. It contains many kinds of organisms, including endangered species. Satoyama is composed of several habitat types, including paddy fields, secondary forests, secondary grasslands, ponds, and streams. High species richness has been sustained in most habitats by anthropogenic disturbances of intermediate impact, mainly activities related to agriculture. The variety of habitats and connectivity among them have contributed to the high species diversity within satoyama. These factors allow organisms to move among habitats and use different habitat types to obtain different resources. The connectivity among habitats is often more vulnerable than the specific habitats themselves under anthropogenic influences. In satoyama, species that require connectivity among habitats (e.g., grey-faced buzzard [Butastur indicus] and Genji firefly [Luciola cruciata]) have tended to decrease. The grey-faced buzzard is categorized as a “vulnerable” species in the Japanese Red List. It usually nests in forest trees and forages in habitats such as paddy fields, grasslands, and forests. Its foraging locations shift seasonally depending on food availability. It is thought that the degradation of either paddy fields or forests in a landscape may result in the disappearance of this species. The Genji firefly spends its larval period in stream water, pupates underground along streams, and flies near streams after emergence. This species requires not only the integrity of streams and nearby areas, but also connectivity between these areas. The ecology of these species suggests that the variety of habitats and connectivity among them are critical factors for their survival.     

Estimating floristic integrity in tallgrass prairie

Indices are needed in habitat conservation and restoration to provide repeatable measures relevant to conservation goals. A monitoring and research program was established at Nachusa Grasslands in north-central Illinois (USA) to assess progress in tallgrass prairie restoration and reconstruction efforts and evaluate the effectiveness of indices used to measure community-level properties related to vegetation integrity. Indices selected for comparison included standard diversity measures (e.g., Shannon-Weiner Index, Evenness, Species Richness) and indices developed specifically to estimate vegetation integrity. These latter indices included two unweighted diversity indices, the Species Richness Index and Native Richness Index, and two indices weighted by characteristics of species composition, the Floristic Quality Index (FQI) and its component Mean Coefficient of Conservatism (Mean C). A coefficient of conservatism (CC) is an integer ranging from 0 to 10 assigned a priori to each taxon in a regional flora that estimates the fidelity of a species to natural areas (non-native and most ruderal species are assigned 0 or low values, respectively; species known primarily from natural areas are assigned higher values). All indices compared in this study were calculated using vegetation data collected from equal-sized sampling grids stratified across seven prairie units. The units included remnants and plantings representing a wide range of habitat quality. The FQI and Mean C explained the most variation among sites and were most effective at distinguishing recognized qualitative differences indicating they can be more informative than traditional species-diversity measures in assessing floristic integrity within community types. The FQI and Mean C are applicable to both quantitative ecological monitoring and plotless survey methods.     

Tundra plants protect the soil surface from UV

In the Arctic, seasonal ozone depletion is resulting in periods of enhanced UV-B radiation at ground level while regional climate change is associated with increasing temperatures. These changes are likely to alter plant distribution, biodiversity and morphology, which may have knock-on effects for microbially driven biogeochemical cycling and other soil processes. Our study examined the transmission of solar UV radiation through arctic tundra plants using a portable UV radiometer and the DLR-biofilm biological UV dosimeter. A strong negative correlation was found between vegetation cover and UV transmission to the soil surface. Penetration of UV to the soil beneath tundra plants varied depending upon plant morphology, being greater through low creeping plants than cushion plants, grasses or mosses. UV transmission to the soil surface beyond the foliage edge also varied with plant morphology and the presence of flowers.