鼎湖山季风常绿阔叶林土壤酸度对土壤养分的影响

通过在鼎湖山季风常绿阔叶林的研究发现 :( 1 )季风常绿阔叶林土壤整个剖面 ( 0～ 60cm)pH值都较低 ,小于 4 5。 ( 2 )土壤养分含量随着土壤剖面层次 ( 0～ 2 0cm、2 0～ 40cm、40～ 60cm)的降低而下降。养分除水解性N外 ,有效P、速效K以及交换性Ca、Mg含量都很少。 ( 3 ) 0～ 2 0cm土壤养分比其它层的土壤养分更容易受到土壤酸度的影响。 40～ 60cm土壤养分除了交换性Ca外 ,其它养分的含量与土壤酸度无显著关系。就不同月份来说 ,1月份和 4月份土壤养分比 7月份和 1 0月份土壤养分容易受到土壤pH值的影响。不同养分比较 ,交换性Ca和Mg以及有效P含量比其它养分更容易受到土壤酸度的影响。     

Estimation of supplementary water to paddy fields in the lower Mekong River basin during the dry season

Efficient management of water resources in paddy fields requires an understanding of the volume of supplementary water used. However, quantifying the volume is laborious due to the large amount of data that must be collected and analyzed. The purpose of our study was to estimate the volume of supplementary water used in paddy fields, based on several years of available statistical data, and to provide information on how much water can be supplied to paddy fields in each target area. In this study, the lower Mekong River basin of northeast Thailand, Laos, and Cambodia was selected as the study area. In the first step, we used agricultural statistics for each country, rainfall data acquired from the Mekong River Commission Secretariat (MRCS), and the value of virtual water required per unit of rice production. Because several years of data were used for dry season harvested areas and rice production in each country, the supplementary water to paddy fields in each province was calculated using virtual water and rainfall. This method made it possible to estimate changes in supplementary water in each province. Through this study, the supplementary water to paddy fields during the dry season in three countries was approximated from the minimum number of data sets. Moreover, for cases in which it is not possible to procure agricultural water use data for a hydrological model simulation, an alternative solution is proposed.     

黑龙江省近40年夏季季风的变化规律

为了分析黑龙江省夏季季风的变化规律和夏季季风与年降水之间关系的变化,采用Samel发明的方法,用逐日降雨量数据计算每一年夏季季风到达、离开、停留在黑龙江省的时间。研究结果显示:在1960年至2000年间,黑龙江省的年降水量变化趋势是每10a增加2.229mm,这一变化趋势不显著;夏季季风停留的时间和季风期间的降水量呈显著减少的趋势,分别为每10a减少6.9d和17.5mm。夏季季风这一变化主要原因在于1960–1975期间是夏季季风离开该省的时间提前,1990–2000年间是到达该省的时间拖后。夏季季风在过去40a的减弱使它对年降水量的贡献率每10a减少4.4%。     

Community economies in Monsoon Asia: Keywords and key reflections

A diversity of place‐based community economic practices that enact ethical interdependence has long enabled livelihoods in Monsoon Asia. Managed either democratically or coercively, these culturally inflected practices have survived the rise of a cash economy, albeit in modified form, sometimes being co‐opted to state projects. In the modern development imaginary, these practices have been positioned as ‘traditional’, ‘rural’ and largely superseded. But if we read against the grain of modernisation, a largely hidden geography of community economic practices emerges. This paper introduces the project of documenting keywords of place‐based community economies in Monsoon Asia. It extends Raymond William’s cultural analysis of keywords into a non‐western context and situates this discursive approach within a material semiotic framing. The paper has been collaboratively written with co‐researchers across Southeast Asia and represents an experimental mode of scholarship that aims to advance a post‐development agenda.     

Features of the AFFRC model for evaluating the relationship between the water cycle and rice production

This paper introduces the Agriculture, Forestry and Fisheries Research Council of Japan (AFFRC) model, an integrated model that predicts future rice production in the Mekong River basin by taking into account the effect of global warming on both the water cycle and the rice economy. The model focuses especially on the water balance of paddy fields for different farmland water use systems. We defined six categories of irrigated paddies and three categories of rain-fed paddies on the basis of their systems of water usage. We included a process-based model to predict future rice production, accounting for daily changes in available water resources such as precipitation. Many models of crop production treat rice in the same way as other crops; the particular characteristics of rice farming are considered in more detail in our model. Our results show that it is possible to estimate future rice production in the Mekong River basin by taking into account changes in available water, and to model the resultant effects on the grain market.     

Variation in canopy structure, light and soil nutrition across elevation of a Sri Lankan tropical rain forest

Mixed dipterocarp forests are perhaps the single most important rain forest type in the wet tropics. Only a few studies have purposefully examined differences in resource availability across mixed dipterocarp forest landscapes by simply measuring the abiotic variables of light, soil nutrition and soil water availability in relation to forest structure. We sought to directly measure the environment of canopy gaps across elevation and geology—from lowland mixed dipterocarp forest (100 m amsl) to lower montane dipterocarp forest (1200 m amsl) in southwest Sri Lanka. Middle elevation gap sites (300–900 m amsl) were subdivided into valley, mid-slope and ridge topographic positions. Eighteen natural disturbances all of which were canopy openings caused by tree fall, were randomly selected within primary rain forest that ranged across 100–1200 m elevation. Plots were placed in gap centers and in adjacent understories and measurements taken of forest structure (basal area, canopy height, canopy cover index, CCI), shade (light sensors—photosynthetically active radiation [PAR], canopy hemispherical photographs—global site factor [GSF]) and soil nutrition (pH, exchangeable Al, K, Mg and Ca; Total N; and plant available P). Soil moisture was measured at bi-weekly intervals for five years across middle elevation sites only (300–900 m amsl). Stand basal area, mean canopy height, and canopy cover index all declined with increase in elevation. Understory PAR and GSF decreased with increases in canopy height, basal area and CCI. Size of canopy opening decreased with increase in elevation, but PAR and GSF increased. Valley sites had significantly greater levels of mean percent soil water content as compared to mid-slope and ridge sites of middle elevation sites. However, at the onset of the southwest monsoons in May all sites were similar. Differences were most pronounced during the dry season (December–April). No differences in soil moisture content could be found between gap and understory microsites. K and Ca in gap centers and adjacent forest understories increased with increase in elevation and change in associated geology. pH increased and Al decreased with elevation and associated geology but only for forest understory conditions. Results demonstrate strong differentiation in soil and light resources with elevation that appears related to size of tree-fall disturbance, stature of the forest, topographic position and underlying geology and soil-weathering environment. This suggests that forest management and conservation practices need to develop and tailor techniques and treatments (silviculture) to the forest that emulate and/or account for change in elevation, geology and topographic position. Further studies are needed to identify which are the primary underlying mechanisms (e.g. temperature, wind, soil nutrients, soil moisture availability) defining change in forest structure across elevation.     

云南雨季开始期的时空变化特征及其与季风的关系

利用197l-2007年云南124站逐日降水资料计算雨季开始期,采用EOF(经验正交函数)分解和最大熵谱分析方法,研究云南雨季开始期的空间分布、时间演变及周期变化特征,并初步分析云南雨季开始期不同分布型与季风的关系,以期为指导春季农业生产提供依据。结果表明,全省雨季开始期一致偏早或偏晚为云南雨季开始期的最主要空间分布特征,其次为滇中及以东地区与滇西北及滇西南地区雨季开始期反向变化的空间分布型;雨季开始期全省一致分布型存在3～5a的显著周期变化,滇中及以东地区与滇西北及滇西南地区雨季开始期反向变化的空间分布型存在3～4a的显著周期变化;云南雨季开始期与同年5月孟加拉湾地区和南海地区OLR有显著的相关关系(P<0.05);南亚季风与南海季风强度指数对云南雨季开始期有重要的指示性意义。     

燕山南麓夏季降水对东亚夏季风变化的响应

利用燕山南麓1951-2005年夏季降水资料和NCEP/NCAR高度场、风场资料,采用趋势分析、小波变换、突变检验等方法,对燕山南麓夏季降水规律和东亚夏季风变化进行了分析。结果发现:(1)燕山南麓夏季降水从1980年以来呈减少趋势,在1996年发生了突变,近年减少更加显著。线性减少趋势显著,平均每10 a减少29mm。(2)燕山南麓夏季降水存在10 a的变化周期,东亚夏季风存在11 a的变化周期,二者变化周期基本一致。降水的10 a周期显著,东亚夏季风11 a周期不太显著。(3)强夏季风年,蒙古地区低气压显著降低,蒙古上空低槽活动频繁,极涡明显变弱,燕山南麓夏季降水偏多。弱夏季风年,蒙古地区低气压明显减弱,蒙古上空低槽活动较少,极涡显著加深,燕山南麓夏季降水偏少。(4)燕山南麓夏季降水减少是对东亚夏季风减弱和对应的中高度大气纬环流变化的响应。     

近百年来季风尾闾区的动态变化及其预测

季风尾闾区的最南位置、最北位置分别出现在20年代末和50年代末,其动态变化主要有整体南北移动和东西相反摆动两种型式;1990—1994年季风尾闾区以北移为主,1995—2000年以南移为主。     

Climate‐driven winter variations of Calanus sinicus abundance in the East China Sea

Global environmental changes threaten the sustainable use of resources and raise uncertainties regarding marine populations' responses in a changing Ocean. The pelagic copepods of the genus Calanus play a central role in shelf ecosystems transferring phytoplankton carbon to harvested populations, from boreal to temperate regions. Here we examined a 15‐yr time series of Calanus sinicus abundance in regards to climate forcing in the East China Sea. We identified a compound effect of the Pacific Decadal Oscillation (PDO) and the East Asian Winter Monsoon (EAWM) on environmental conditions in the East China Sea. Such climate influences not only a southward transport of C. sinicus from its population centres into the Taiwan area, but favours advantageous thermal conditions for the species as well. On the interannual scale, our results show that the population size of C. sinicus echoes climate‐driven temperature changes. Hence, the possibility of using the PDO and EAWM variability for assessing and predicting interannual abundance changes of C. sinicus in the East China Sea is considered. The observed close relationship between climate and C. sinicus may promote bottom‐up controls in the pelagic food web, further influencing the southern edge of the species' geographic distribution. Owing to the prominent role this species plays in food web dynamics these results might help integrative fisheries management policies in the heavily exploited East China Sea.