Nutrient budget of a montane evergreen broad‐leaved forest at Ailao Mountain National Nature Reserve,Yunnan, southwest China

Hydrological fluxes and associated nutrient budget were studied during a 2 year period (1998–99) in a montane moist evergreen broad‐leaved forest at Ailao Mountain, Yunnan. Water samples of rainfall, throughfall, and stemflow, and of surface runoff, soil water, and stream flow were collected bimonthly to determine the concentration and fluxes of nutrients. Soil budgets were determined from the difference between precipitation input (including nutrient leaching from canopy) and output via runoff and drainage. The forest was characterized by low canopy interception and surface runoff, and high percolation and stream flow. Concentrations of nutrients were increased in throughfall and stemflow compared with precipitation. Surface runoff and drainage water had higher nutrient concentrations than precipitation and stream water. Total nitrogen and NH₄⁺‐N concentrations were higher in soil water than stream water, whereas K⁺, Ca²⁺, and Mg²⁺ concentrations were lower in the former than the latter. Annual nutrient fluxes decreased with soil depth following the pattern of water flux. Annual losses of most nutrient elements via stream flow were less than the corresponding inputs via throughfall and stemflow, except for calcium, for which solute loss was greater than the inputs via precipitation. Leaching losses of that element may be compensated by weathering. Losses of nitrogen, phosphorus, potassium, magnesium, sodium, and sulphur could be replaced through atmospheric inputs. Copyright © 2002 John Wiley & Sons, Ltd.     

土地利用变化对亚热带山地红壤团聚体有机碳的影响

研究土地利用变化对土壤团聚体有机碳的影响。对福建省建瓯市山地红壤的农业利用(坡耕地、茶园、桔园)、林业利用(杉木、木荷、封育)不同土层(0~10 cm、10~20 cm)土壤团聚体有机碳含量与有机碳贮量进行研究。结果表明:不同土地利用方式土壤团聚体呈现粒径越小,有机碳含量越高的规律,其中木荷有机碳含量最高,茶园最小。林地随着粒径增加,土壤团聚体碳贮量呈增加的趋势,>2 mm团聚体有机碳贮量最高。土壤总有机碳增加主要受到大团聚体有机碳增加的影响。亚热带山地红壤内林地开垦为农业用地导致土壤及其团聚体中有机碳大幅度下降。     

Temporal and Spatial Characteristics of Intraseasonal Oscillations in the Meridional Wind Field over the Subtropical Northern Pacific

Based on the NCEP/NCAR reanalysis I daily data from 1958 to 2002, climatic characteristics of the 30-60-day intraseasonal oscillations (ISOs) of the zonal wind (u), meridional wind (v), and geopotential height (h) over global areas and especially the ISO of v over the subtropical northern Pacific are analyzed using the space-time spectrum analysis and wavelet transform methods. The results show that the ISO of v is very different from those of u and h, with the former representing the meridional low-frequency disturbances, which are the most active in the subtropics and mid-high latitudes, but very weak in the tropics. In the subtropical Northern Hemisphere, the energies of the ISOs of u and h are both concentrated on the waves with wave number of 1 and periods of 30-60 days, while the main energy of the ISO of v is concentrated on the waves with wave numbers of 4-6 and periods of 30-60 and 70-90 days. The westward propagating energies for the 30-60-day oscillations of u, v, and h are all stronger than the eastward propagating energies in the subtropics. In addition, the ISO of v is the strongest (weakest) in summer (winter) over the subtropics of East Asia and northwestern Pacific, while the situation is reversed over the subtropical northeastern Pacific, revealing a "seesaw" of the ISO intensity with seasons over the subtropics from the northwestern to northeastern Pacific. In the subtropical northwestern Pacific, the interannual and interdecadal changes of the ISO for v at 850 hPa indicate that its activities are significantly strong during 1958 1975, while obviously weak during 1976-1990, and are the strongest during 1991-2000, and its spectral energy is obviously abnormal but ruleless during the ENSO periods. However, in the 2 7-yr bandpass filtering series, the interannual changes of the v ISO over the subtropical northwestern Pacific contain distinct ENSO signals. And in the 9-yr low-pass filtering series, the v ISO changes over the subtropical northwestern Pacific are significantly out of phase with the changes of the Ni(n)o -3.4 SST, whereas the v ISO changes in the subtropical northeastern Pacific are significantly in phase with the changes of the Ni(n)o-3.4 SST.     

光照与紫外辐射对亚热带树木叶片排放CH4的影响

植物排放甲烷（CH4）的来源尚存很大争议,而光照和紫外辐射胁迫可能是植物排放CH4的重要影响因素．本研究选择亚热带常见树种米槠、木荷、浙江桂、罗浮栲、杉木、马尾松和柑橘7种树木为研究对象,利用控制实验研究了光照和增强紫外辐射对树木叶片CH4排放的影响．结果表明：7种树木叶片的平均CH4排放速率在光照条件下（21.176ng·CH4·g^-1DW·h^-1）是在黑暗条件下（9．699ng·CH4·g^-1DW·h^-1）的2．2倍,光照对不同树木叶片CH4排放速率的影响具有显著差异;在高UV-B辐射强度处理下,除浙江桂和柑橘外,其他5种树木的CH4排放速率均显著高于低UV—B辐射强度处理的CH4排放速率;树种及其与光照或UV辐射的交互作用对树木叶片CH4排放速率的都具有显著影响,光照或增强UV辐射强度对排放速率较低的树木种类排放CH4的促进作用更强．     

汉江一级阶地抬升以来北亚热带风尘堆积、发育与东亚季风演变的耦合关系——以郧县段汉江上游谷地为例

风成黄土对东亚冬夏季风优势期转换及起迄时间起到良好指示作用,探究风尘黄土堆积、发育特征与东亚季风演变的耦合关系十分必要。本文通过研究汉江一级阶地上覆黄土-古土壤序列的构型、磁化率、烧失量、粒度、元素组成特征,分析汉江一级阶地抬升以来黄土-古土壤序列的成因及成壤特征,探究东亚冬夏季风的演化序列。结果表明：（1）汉江上游地区黄土-古土壤序列的地层构型为表层土（MS）-近代黄土（L₀）-古土壤（S₀）-过渡层（L_t）-马兰黄土（L₁）,磁化率、粒度、烧失量、元素组成等特征指示各地层成壤强度特征为S₀>L₀/L_t>L₁。（2） 成壤强度指示18000 a BP以来,东亚冬夏季风演替特征为末次盛冰期冬季风强烈→全新世早期冬季风减弱→全新世中期夏季风主导→全新世晚期夏季风减弱~,冬季风强盛,其演变滞后于低纬太阳辐射变化2000~3000 a。（3）该风尘堆积物理化性质对6000~5000a BP的气候恶化期有所响应。总而言之,汉江上游一级阶地上覆黄土为风尘堆积物,指示18000a BP以来东亚季风的变迁规律及季风异常事件,能够体现北亚热带对全球气候变化及极端事件的响应。     

典型亚热带城市片林与草坪土壤全磷垂直分布特征

城市作为人类栖息的主要场所,其含有丰富P源的城市绿地土壤受到人为活动的强烈影响·为了探讨亚热带不同类型城市绿地土壤全P含量的分布特征,于2010年9--12月对福州市典型城市片林与草坪土壤全P垂直分布特征进行研究,结果表明：研究区绿地40cm以上土壤全P含量平均值为0．61g·kg^-1,其中城市片林和草坪土壤全P含量...     

Changes of citrus climate risk in subtropics of China

Based on the citrus temperature, precipitation, sunlight and climate risk degree, the article divides subtropics of China into three types: the low risk region, the moderate risk region and the high risk region. The citrus temperature risk increases with increasing latitude (except for the western mountainous area of subtropics of China). The citrus precipitation risk in the central part of subtropics of China is higher than that in the northern and western parts. The distributions of citrus sunlight risk are not consistent to those of the citrus precipitation risk. The citrus climate risk is mainly influenced by temperature. There is latitudinal zonal law for the distribution of the climate risk, that is, the climate risk increases with increasing latitude. At the same time the climate risk in mountainous area is high and that in eastern plain area is low. There are differences in the temporal and spatial changes of the citrus climate. In recent 46 years, the citrus climate risk presents a gradual increasing trend in subtropics of China, especially it has been increasing fast since the 1980s. Because of the global warming, the low risk region in the eastern and southern parts has a gradual decreasing trend, however, the high risk region in the northern and western parts has an increasing trend and the high risk region has been extending eastward and southward. The article analyses the distribution of the citrus climate risk degree of reduction rates of >10%, >20% and >30% in subtropics of China, and studies their changes in different time periods. Results show that the risk is increasing from southeast to northwest.     

长期施肥影响下亚热带红壤性水稻土团聚体组成及氮储量分布特征

以亚热带典型红壤性水稻土为研究对象,利用干筛法研究长期单施化肥和化肥配施有机肥对耕作层和犁底层土壤团聚体组成及其全氮储量分布的影响.结果表明:＞5 mm的块状结构是土壤团聚体的主要组分,其含量比例高达65.7％～83.4％;同时,该级团聚体中全氮储量占土壤总储量的比例亦高达63.1％～82.7％,是土壤全氮储量的主要载体.随土层加深,块状结构体比例增加,其他粒级团聚体含量降低.除＜0.25 mm粒级外,团聚体中全氮含量随其粒径减小而增大,而全氮储量则呈降低趋势.施肥特别是化肥配施有机肥后同土层0.25～5 mm大团聚体含量显著增加.团聚体稳定性增强,2～5、0.5～2、0.25～0.5 mm团聚体及土壤中全氮含量和储量显著增加(P＜0.05),新增氮储量主要向大团聚体,特别是2～5 mm团聚体中富集.施肥对团聚体组成及其全氮含量的影响随土层加深而减弱.与单施化肥相比较,化肥配施有机肥显著提升犁底层和全层土壤全氮储量(P＜0.05),是更好的施肥模式,可在亚热带红壤性水稻土分布区推广应用.     

亚热带樟树树干液流通量变化规律

采用热脉冲技术于2013―2015 年连续测定了樟树的树干液流,并同步监测了环境因子,分析了樟树树干液流日变化和季节变化特征以及对不同环境条件的响应。结果表明：樟树树干液流速率晴天日变化为典型的单峰型曲线,季节变化明显,液流速率峰值夏季＞春季＞秋季＞冬季,峰宽随季节变化存在“窄→宽→窄”的逐步变化过程。樟树存在微弱的夜间液流,且生长季较其他月份活跃。液流启动时间夏季最早,冬季最晚,液流结束（进入夜间低值）时间夏季晚于冬季约1~2 h。上下午液流量比值均＜1,平均值为0.74。同月不同天气条件下,液流速率和液流量均为晴天＞阴天＞雨天。干旱环境下,樟树树干液流峰值下降了约95%,与2014 年相比,同期内液流总量减少了约47.8%,在干旱中液流量与气温、水汽压亏缺呈显著负相关,改变了常年中（没有干旱）液流量与气温和水汽压亏缺呈显著正相关的关系。干旱显著降低了樟树的树干液流量,也反映了樟树对干旱的适应过程。     

A Climatological Investigation of the Activity of Summer Subtropical Vortices

By applying a new vortex detection method to the ECMWF 40-yr reanalysis (ERA40) data from 1985 to 2002, the climatology of summer vortices has been investigated in five subtropical regions, i.e., the northwestern Pacific, northeastern Pacific, northwestern Atlantic, northeastern Atlantic, and Australia-South Pacific, followed by validation with NCEP/NCAR reanalysis data. Results are as follows: (1) The spatial distributions of ERA40 vortex activities (VAC) were well consistent with those of NCEP/NCAR reanalysis (NRA) results in all regions, especially in northwestern Pacific. (2) Because of different model resolutions, both the number and intensity of vortices obtained from NRA were significantly weaker thanERA40's. (3) Vortices mainly cruised in coasts and the adjacent seas, from where to the land or the open sea vortex activities were gradually decreased. (4) There were two active centers in the northwestern Pacific:one was located in South China Sea and the other, as the largest center of the five regions, spread from the east side of the Philippines to Japan. (5) Over the northwestern Atlantic, most vortices occurred in Panama and its west-side offshore. (6) The spatial distributions of vortices were alike between the northeastern Pacific and northeastern Atlantic, both spreading from coasts to the west-side sea at 5°-20°N. (7) In the Anstralia-South Pacific, vortices were not as active as those in the other four regions, and mostly took place in the equator-side of near ocean areas. (8) Except the northwestern Pacific and northwestern Atlantic, the VAC interannual variations in the other three regions were different between ERA40 and NRA data. (9)In the northwestern Pacific and northwestern Atlantic, the VAC interannual variation could be separated to several distinct stages. (10) Since the mid 1980s, mean vortex intensity was getting increased in the northwestern Pacific, which was most significant in the subtropical areas on a global basis. In the western North Atlantic, there was a decreasing (increasing) trend of the mean vortex intensity before (after) the mid1990s.