A multidecadal oscillation in precipitation and temperature series is pronounced in low flow series from Puget Sound streams

In Pacific Northwest streams, summer low flows limit water available to competing instream (salmon) and out-of-stream (human) uses, creating broad interest in how and why low flows are trending. Analyses that assumed linear (monotonic) change over the last ~60 years revealed declining low flow trends in minimally disturbed streams. Here, polynomials were used to model flow trends between 1929 and 2015. A multidecadal oscillation was observed in flows, which increased initially from the 1930s until the 1950s, declined until the 1990s, and then increased again. A similar oscillation was detected in precipitation series, and opposing oscillations in surface temperature, Pacific Decadal Oscillation, and Interdecadal Pacific Oscillation series. Multidecadal oscillations with similar periods to those described here are well known in climate indices. Fitted model terms were consistent with flow trends being influenced by at least two drivers, one oscillating and the other monotonic. Anthropogenic warming is a candidate driver for the monotonic decline, and variation in (internal) climatic circulation for the oscillating trend, but others were not ruled out. The recent upturn in streamflows suggests that anthropogenic warming has not been the dominant factor driving streamflow trends, at least until 2015. Climate projections based on simulations that omit drivers of multidecadal variation are likely to underestimate the range, and rate of change, of future climatic variation.     

全球环境问题和我国的原则立场

目前全球气候变化、臭氧层破坏等生态环境问题,以及治理和保护环境问题,已成为各国政府和人民的共同认识和要求。本文阐述了发达国家和发展中国家在保护环境重大问题上的合作与分岐,以及我国对解决全球环境问题的基本原则。     

太湖地区3种水稻土不同温度培养中有机碳库变化及其对升温的响应

全球变暖下土壤有机碳储存的变化是土壤与全球变化研究的热点问题.本研究选择了3种太湖地区代表性水稻土的表层土壤,分别进行20℃和25℃的室内恒温培养,监测培养过程中总有机碳、溶解性有机碳和微生物量碳的变化动态,试图了解这些土壤的有机碳分解过程对全球变暖的响应特点.结果表明,这些土壤培养中总有机碳变化可以用一级衰变动力学方程或对数衰减方程描述,但动力学特征依培养温度的不同而异.升温大大促进了铁渗水耕人为土和潜育水耕人为土中有机碳的分解与呼吸损失,而铁聚水耕人为土没有显著变化.供试土壤总有机碳损失的Q₁₀系数分别为:潜育水耕人为土(11.1～14.1)＞铁渗水耕人为土(4.4～6.4)＞铁聚水耕人为土(0.63～0.73).这一方面说明温度敏感性在同一地带的不同土壤间的差异超过文献上报道的不同气候带的差异,但另一方面揭示了水稻土可能是一类对全球升温敏感响应的人为土.溶解性有机碳和微生物量的碳的变化还提示不同温度培养下水稻土微生物群落结构可能改变,因而影响到土壤有机碳库的生物有效性在温度条件下的变化.可以认为,土壤升温下有机碳的变化不但与土壤有机碳的性质有关,而且与土壤性质控制下的生物条件的改变有关.故土壤升温下有机碳的损失不仅仅是温度对分解过程的反应速度的影响.当然,对于不同土壤间的这种差异还需从有机碳-土壤环境-土壤生物的相互关系上做进一步的工作.     

1961—2010年广西气温变化对全球变暖的响应

利用广西88 个气象站1961—2010 年的年平均气温和年极端最高、最低气温数据,运用GIS 技术、气候倾向率以及Mann-Kendall 突变检验方法对广西近50 a 气温的时空变化特征及突变特征进行分析。结果表明:在全球变暖影响下, 近50 a 广西全区年平均气温和年极端最高、最低气温总体上均呈上升趋势,其中年平均气温和年极端最低气温的气候倾向率均达到了极显著水平;年平均气温和年极端最高气温的突变时间分别为2001 年和2003 年,均比极端最低气温(1984 年) 晚了近20 a 左右;年极端最高和最低气温存在非对称变化。时空分布图表明,区域平均值忽略了研究区域内的差异,尽管近50 a 来广西气温区域平均值的总体变化呈上升趋势,但不同时期各地区间气温变化的趋势和幅度各有差异。     

Effects of temperature variation on TSD in turtle (C. picta) populations

We formulate a two-sex model of temperature-dependent sex determination (TSD) for a freshwater turtle (C. picta) population. The aim is to understand how environmental temperature variations and nest heat conduction properties affect the long term dynamics of the population. This is a key to understanding how global temperature changes may affect their survival. With stochastic inputs of ambient temperature and solar radiation, the model uses the heat equation to determine the temperature in the egg layer in the nest; in turn, this determines the sex ratio in the egg clutch using a variable degree-day model. Finally, a nonlinear Leslie type, stage-based, two-sex model, is used to determine the long term male and female populations. A two-sex model is required because of different development rates for males and females. The model is flexible enough to enable other researchers to examine the effects of temperature variation variations on other species with TSD, e.g., crocodilians, reptilians, as well as other turtle species. It can be adapted to study effects of nest location, soil type, rain events, different incubation periods, and density effects, for example, the dependence of the mating function on the ratio of males to females and each’s contribution to the sex of hatchlings. Modifications can be easily made to fit a specific life history traits. The model is a beginning step in understanding the long term, high fitness shown by many reptile species with TSD, and it may suggest to experimentalists what data may be relevant to these issues; it can also be useful to wildlife managers in developing strategies for intervention if needed. Among the principal findings are that temperature variability and detailed nest heat conduction properties may buffer projected negative effects on a population.     

Modelling forest management within a global vegetation model—Part 1: Model structure and general behaviour

This article describes a new forest management module (FMM) that explicitly simulates forest stand growth and management within a process-based global vegetation model (GVM) called ORCHIDEE. The net primary productivity simulated by ORCHIDEE is used as an input to the FMM. The FMM then calculates stand and management characteristics such as stand density, tree size distribution, tree growth, the timing and intensity of thinnings and clear-cuts, wood extraction and litter generated after thinning. Some of these variables are then fed back to ORCHIDEE. These computations are made possible with a distribution-based modelling of individual tree size. The model derives natural mortality from the relative density index (rdi), a competition index based on tree size and stand density. Based on the common forestry management principle of avoiding natural mortality, a set of rules is defined to calculate the recurrent intensity and frequency of forestry operations during the stand lifetime. The new-coupled model is called ORCHIDEE-FM (forest management).The general behaviour of ORCHIDEE-FM is analysed for a broadleaf forest in north-eastern France. Flux simulation throughout a forest rotation compare well with the literature values, both in absolute values and dynamics.Results from ORCHIDEE-FM highlight the impact of forest management on ecosystem C-cycling, both in terms of carbon fluxes and stocks. In particular, the average net ecosystem productivity (NEP) of 225 gC m⁻² year⁻¹ is close to the biome average of 311 gC m⁻² year⁻¹. The NEP of the “unmanaged” case is 40% lower, leading us to conclude that management explains 40% of the cumulated carbon sink over 150 years. A sensitivity analysis reveals 4 major avenues for improvement: a better determination of initial conditions, an improved allocation scheme to explain age-related decline in productivity, and an increased specificity of both the self-thinning curve and the biomass-diameter allometry.     

Analysis of the global warming dynamics from temperature time series

Global warming is the observed increase of the average temperature of the Earth. The primary cause of this phenomenon is the release of the greenhouse gases by burning of fossil fuels, land cleaning, agriculture, among others, leading to the increase of the so-called greenhouse effect. An approach to deal with this important problem is the time series analysis. In this regard, different techniques can be applied to evaluate the global warming dynamics. This kind of analysis allows one to make better predictions increasing our comprehension of the phenomenon. This article applies nonlinear tools to analyze temperature time series establishing state space reconstruction and prediction. Since noise contamination is unavoidable in data acquisition, it is important to employ robust techniques. The method of delay coordinates is employed for state space reconstruction and delay parameters are evaluated using the method of average mutual information and the method of false nearest neighbors. Afterwards, the simple nonlinear prediction method is employed to estimate temperatures of the future. Temperature time series from different places of the planet are used. Initially, the approach is verified considering known parts of the time series and afterwards, results are extrapolated for future values estimating temperature until 2028. Results show that these techniques are interesting to estimate temperature time history, presenting coherent estimations.     

模拟增温效应对西藏苔草繁殖生态的影响

通过采用国际冻原计划模拟增温对植物影响的方法,从繁殖生态学角度研究了西藏苔草（Carex thibetica Franch）种群的物候期、分蘖数、生物量和种群繁殖对增温的响应。结果表明：暖棚内气温、土壤表层温度分别了1.17℃和1.50℃;物候期提前或延迟,生长期延长;增温可以提高西藏苔草的生殖产量,但不提高其种子发芽率;增温可提高西藏苔草分蘖数和生物量;西藏苔草繁殖对策趋于营养繁殖。     

What are the barriers to successful community-based climate change adaptation? A review of grey literature

ABSTRACT

Across the Global South, community-based adaptation (CBA) projects are increasingly being implemented in an effort to respond effectively and sustainably to the impacts of climate change, with a particular focus on people’s livelihoods. Despite an increase in the number of CBA projects being implemented, detailed analysis and evaluation of their efficacy and the barriers faced in achieving successful outcomes is lacking. This study draws on an analysis of grey literature (i.e. project and donor reports) to explore the barriers faced in achieving effective CBA. An extensive global search of online project evaluations yielded 25 documents comprising 69 projects from which this analysis is based. This paper first presents an overview of the 69 projects and highlights any trends. Second, this paper describes the barriers to CBA according to three broad themes: socio-political, resource, and physical systems and processes. Following this is a discussion of the most prevalent barriers: cognitive and behavioural, financial, and human resources. Third, this paper discusses the key findings elucidated from this review. This includes the need for greater sharing of project reports and findings so lessons can be learned across spatial and temporal scales, and the disparity between critical academic literature on CBA and what is implemented in practice.     

Impact of bioenergy crops in a carbon dioxide constrained world: an application of the MiniCAM energy-agriculture and land use model

In the coming century, modern bioenergy crops have the potential to play a crucial role in the global energy mix, especially under policies to reduce carbon dioxide emissions as proposed by many in the international community. Previous studies have not fully addressed many of the dynamic interactions and effects of a policy-induced expansion of bioenergy crop production, particularly on crop yields and human food demand. This study combines an updated agriculture and land use (AgLU) model with a well-developed energy-economic model to provide an analysis of the effects of bioenergy crops on energy, agricultural and land use systems. The results indicate that carbon dioxide mitigation policies can stimulate a large production of bioenergy crops, dependent on the level of the policy. This production of bioenergy crops can lead to several impacts on the agriculture and land use system: decreases in forestland and unmanaged land, decreases in the average yield of food crops, increases in the prices of food crops, and decreases in the level of human demand of calories.