亚热带流域氮磷排放与养殖业环境承载力实例研究

畜禽养殖业粪便排放已经成为我国农村地区主要的农业面源污染源之一,也是制约养殖业良性发展的主要瓶颈.本文以湖南省长沙县典型亚热带流域为研究单元,基于流域水环境定位观测、耕地氮(N)磷(P)消纳能力以及养殖业调查和土壤分析资料,初步分析了亚热带丘陵区的面源污染现状及畜禽养殖业的环境承载力.结果表明,研究区金井河流域134.4 km2范围内N、P年负荷分别为N 2.72 t·km-2和P0.11t·km-2,其中养殖粪便对水体总氮(TN)、总磷(TP)负荷的贡献率分别约为42.2％和62.0％.区内平均畜禽养殖密度为3.46 AU·hm-2(相当于流域内年出栏生猪24.39万头),显著高于现有化肥用量条件下流域的实际承载力1.13 AU·hm-2(相当于流域内年出栏生猪6.35万头),因此养殖密度过高是导致研究区水体NP负荷较高的主要原因.区内N、P盈余量分别为N 35.8 kg·hm-2、P 18.61 kg·hm-2.研究区基本不施用化肥条件下畜禽养殖业的最大环境承载力为7.26 AU·hm-2,在有机肥占合理施肥量30％条件下,当地畜禽养殖业的环境承载力为2.74AU·hm-2(相当于流域内年出栏生猪19.50万头).降低养殖密度、调整养殖业空间布局以及提高养殖废弃物的资源化利用率是防治当前面源污染的有效途径.     

Deriving state-and-transition models from an image series of grassland pattern dynamics

We present how state-and-transition models (STMs) may be derived from image data, providing a graphical means of understanding how ecological dynamics are driven by complex interactions among ecosystem events. A temporal sequence of imagery of fine scale vegetation patterning was acquired from close range photogrammetry (CRP) of 1 m quadrats, in a long term monitoring project of Themeda triandra (Forsskal) grasslands in north western Australia. A principal components scaling of image metrics calculated on the imagery defined the state space of the STM, and thereby characterised the different patterns found in the imagery. Using the state space, we were able to relate key events (i.e. fire and rainfall) to both the image data and aboveground biomass, and identified distinct ecological ‘phases’ and ‘transitions’ of the system. The methodology objectively constructs a STM from imagery and, in principle, may be applied to any temporal sequence of imagery captured in any event-driven system. Our approach, by integrating image data, addresses the labour constraint limiting the extensive use of STMs in managing vegetation change in arid and semiarid rangelands.     

两种光照生境下4种常绿阔叶树的单位叶面积干重、光合能力与化学防御物质含量比较

亚热带常绿阔叶林下分布着可塑性强的耐荫植物,其叶片应对外界干扰的防御对策至少有物理性防御和化学性防御两种,这两种防御代价在一定的昆虫取食压力下在理论上应该存在权衡.为检验这种权衡是否普遍存在,分别测定了重庆缙云山4个常绿物种——光叶山矾(Symplocos lancifolia)、四川山矾(S.setchuensis)、四川毛蕊茶(Camellialawii)和细枝柃(Eurya loquaiana)在林窗和林下两种对照光环境下个体叶片的光饱和下的净光合速率、叶面积干重和部分化学防御物质含量.结果表明,4个物种生活在林窗的个体单位叶面积干重、叶片氮含量和单位面积净光合速率通常高于林下的个体,但是单位质量和单位面积的总酚含量和C/N值却低于林下的个体.蛋白质和非结构性碳水化合物含量在不同生境中没有显著差异.因为不同物种叶片对光照条件的响应不同,不同参数的变化在两种生境间的差异并不完全一致.本研究结果在一定程度上暗示了物种在林窗和林下分别倾向于采取物理和化学性防御对策,并初步证实了两种防御强度之间存在权衡关系.图4参40     

REVIEW OF A SEVENTEEN-YEAR CHLOROPHYLL RECORD AS IT PERTAINS TO THE TROPIIIC STATUS OF LAKE OKEECHOBEE,FLORIDA, USA1

ABSTRACT: A 17-year record of chlorophyll a at eight limnetic sampling stations was used to evaluate putative changes in the trophic status of Lake Okeechobee, a shallow polymictic lake located in the subtropical environment of South Florida. Significant spatial differences were observed in the temporal patterns and variability of chlorophyll a concentrations. The highest chlorophyll a values were found in the northern and northwestern regions of the lake. The center of the lake, subject to high levels of non-algal suspended solids, exhibited relatively low chlorophyll a values and coefficient of variation. The lowest chlorophyll a values were observed at the southernmost sampling station in the lake. This was also the station that showed a significant upward trend in annual mean chlorophyll a values over the 17-year period of record. Examination of the relationship between chlorophyll a and three key environmental variables (i.e., total phosphorus concentration, phosphorus loading, and lake stage) revealed significant correlations at two out of the eight stations. The overall results of this study indicate that spatial and temporal disparities in the distribution and dynamics of chlorophyll a in Lake Okeechobee mandate more temporally and spatially intense approaches to the evaluation of trophic state than used in previous studies.     

增补UV-B辐射下南亚热带森林建群树种叶片对UV-B辐射的防护

研究了我国南亚热带森林5种建群树种UV-B辐射诱导的UV-B吸收物质(在280～320 nm波长下测定)的积累及抗UV-B辐射的可能性保护机制.增补UV-B辐射下,马尾松(Pinus massoniana)针叶的甲醇可溶性提取物和细胞壁的碱提取酚类的含量明显高于正常水平的光辐射下.红椎(Castanopsis hystrix)和厚壳桂(Cryptocarya chinensis)叶片的这些化学物质也升高,意味着增补UV-B辐射刺激UV-B辐射吸收物质的生成,形成抗UV-B辐射的功能性保护结构.然而,自然光下已含有大量细胞壁碱提取酚类的荷木(Schima superba)和藜蒴(Castanopsis fissa),这些化合物在增补UV-B辐射下则见下降,很有可能表皮层细胞壁碱提取酚类被转移到含有较低甲醇可溶性色素的液胞可溶性化合物里,这一现象意示着可能涉及叶肉组织光合机构的保护策略.增补UV-B下,马尾松针叶的叶绿素a和b含量不受影响,而其他4种阔叶树叶片则下降10.7% 到16.8%不等.胡萝卜素对增补UV-B辐射的响应变化不一,红椎和荷木的胡萝卜素水平下降,而马尾松、厚壳桂和藜蒴的胡萝卜素则上升,后者也许与功能性增加激发能耗散有关.结果显示,自然条件下不同树种展示出不同的驯化策略以形成抗UV-B辐射增加的防护机制.表4参29     

模拟氮沉降对苗圃地土壤动物群落的影响

通过人工喷施氮H4NO3建立了一个模拟氮沉降增加梯度系列,在近18个月的试验处理期间,研究了2003年7月、10月和2004年2月、5月这几个不同季度苗圃试验样地土壤动物群落对氮沉降增加的响应。实验分为5个处理组:对照、低氮、中氮、高氮和倍高氮,分别接受0、5、10、15、30g/(m2·a)的氮沉降量。土壤细菌和真菌的数量总体上随氮处理的加强而持续显著地增长,土壤有机氮含量也持续升高,土壤酸度则不断下降。采样期对土壤动物的个体数量、类群丰度和多样性存在显著的影响,总的来说,土壤动物群落随试验处理期加长而持续增长。土壤动物群落具有显著的垂直分异特征,土壤I层土壤动物个体数量、类群丰度和多样性显著高于II和III层。氮沉降增加对土壤动物群落有明显的影响,表现为施氮处理明显有利于土壤动物群落的发展,但也具有明显的阀值效应。与对照样地相比,各施氮处理样地土壤动物群落水平整体为高,而且随试验处理时间的增加这种差异有加大的趋势;氮沉降增加处理与取样期之间存在显著的交互作用,除了2月取样,中氮处理土壤动物群落水平都处于最高水平,而对照处理一般处于最低水平,这种趋势在最后一次取样中最为明显;氮沉降处理与土壤动物的垂直分布之间也有明显的交互作用:在土壤I层,从对照至倍高氮处理,土壤动物群     

Fate of parathion in soil under sub‐tropical field conditions

Abstract

Persistence, metabolism and binding of ¹⁴C‐parathion in alkaline sandy loam soil under sub‐tropical conditions of Delhi were studied for 545 days. After 3 days of treatment, ¹⁴C‐residues declined to 41% of the amount applied. The dissipation curve was biphasic; an initial rapid phase (up to 7 days) followed by slow dissipation. The half life of dissipation was only 3.36 days for the first phase and 84 days for the slow phase. The overall half life was 64.5 days. The total residues at zero‐time were 10.65 μg/g dry soil and were almost totally extractable. The extracts consisted of parathion, 4‐aminophenol, 4‐nitrophenol and paraoxon. The bound residues gradually increased and accounted for the total residue at the end of one year (0.7 μg/g).     

Dynamics of Ammonia Exchange in Response to Cutting and Fertilising in an Intensively-Managed Grassland

Continuous micrometorological measurements of ammonia (NH₃)exchange were made for a period of 19 months (May 1998–November 1999) over intensively managed grassland in southern Scotland. This study focused on the influence of management activities, such as cutting and fertilising, on vegetation-atmosphere exchange of NH₃. Measurements were conducted within the European project GRAMINAE (GRassland AMmonia INteractions Across Europe) within which the Scottish site forms one of 6 sites in an E–W transect across Europe. NH₃ emissions were enhanced (up to 300 ng m^-2 s^-1) after cutting followed by larger emissions after fertilising (up to 1400 ng m^-2 s^-1). Annual budget calculations show the intensive grassland acted as a net source (1.8 kg N ha^-1 yr¹) although fluxes were bi-directional with deposition dominating in the winter and emission in the summer. Initial modelling of the NH₃ exchange using a `canopy compensation point' model has been conducted for key periods. The dynamics of the fluxes during these key periods, such as before and after cutting and fertilising, may be reproduced by introducing different values of the apoplastic ratio, = [NH₄ ⁺]/[H⁺].     

2003年夏秋季大气环流异常对西北地区降水的影响

根据2003年6～10月西北地区118站逐日降水资料,对该地区、该时段的大气环流及其对该地区降水的影响进行了分析研究.