土壤有机碳同位素组成在农田生态系统碳循环中的应用进展

土壤有机碳是地球表层储量最高且储存周期最长的生态系统碳库之一。如何提高土壤有机碳稳定性和增强土壤固碳减排能力,是陆地生态系统碳管理可持续战略的关键科学问题。国际学术界一致认为农田生态系统在固碳方面的作用越来越明显,在实现碳中和的进程中发挥重要的作用。农田管理实践方式会扰动土壤碳循环过程,采取有效的管理方式会使其成为碳汇。目前,国内研究主要集中在耕作方式、施肥和灌溉水平、秸秆还田对农田生产力、碳固持速率、温室气体排放方面的影响,但就农田生态系统有机碳稳定性对不同农田管理方式的响应机制以及与土壤碳排放之间的关系认识尚未明确。^(13)C同位素技术是研究农田土壤碳循环过程的有力工具,通过测定土壤碳排放过程中不同有机碳组分的同位素丰度,能够精准区别土壤呼吸组分和来源,从而更好地揭示土壤有机碳稳定性对农田管理措施的响应机制,为增强土壤碳汇效应和农业可持续发展提供科学依据。以往的研究大多集中在模拟试验以及小范围、短时间监测,与实际差距较大,测量结果会高估或低估实际值。因此,在未来的农田土壤碳循环研究过程中要采取多点、长时间实时原位监测,并结合^(13)C同位素技术,实现土壤CO_(2)排放实时分解,达到揭示土壤有机碳稳定性机制的目的。

Advances in Quantifying Impact and Extent of Water-Land-Food Nexus for Food Security in Africa

Food systems have the potential to promote human health and enhance environmental sustainability;yet most African countries have decadal starvation and malnourishment due to unstable food systems lacking basic nutritional profiles. To understand the key questions of the African food production and food security crisis, it is important to evaluate the past and the present balance of food production and consumption quantitatively and comprehensively and identify resource constraints. This continental study analyzed water-land-food (WLF) nexus in recent decades (1997-2017) and accessed whether these resources cope with different population growth projections, dietary changes and agricultural water management. The findings revealed that in 2017, total production in Africa for the four major crops was 83.3, 34.1, 21.0 and 26.7 million tons for, respectively, maize, rice, sorghum and wheat. Together with the imported food, 38 countries experienced an increase in kcal by food supply, while 7 countries encountered a decrease. However, only 6 countries were above the 1500 kcal∙capita−1∙day−1—the global average food consumption from the four major crops. The study also found that in the context of food production and out of the total African population, 268 million (21.6%) have enough land and water, 310 million (25.0%) is without enough land and water, further 279 million (22.5%) have enough water but not enough land, and 381 million (30.8%) encounter enough land but not enough water. This is the first WLF nexus study for the African continent and emphasizes the need for efficient and rapid changes in the food systems of the African population, both in production and consumption, in order to provide sustainable and secure food systems, and ultimately approach the first three Sustainable Development Goals.

Global Dryland Ecosystem Programme(G-DEP):Africa consultative meeting report

In order to enhance and restore the ecosystems of natural capital in African arid regions,the Global Dryland Ecosystem Programme(G-DEP)consultative meeting was hosted in Dakar,Senegal,from 23 to 25 September 2019.This paper details the first African meeting of the G-DEP.Consultative meeting reviewed preceding dryland ecosystems case studies,identified vulnerable arid and semi-arid regions,and proposed sustainable solutions to problems.It also identified the successes and failures of previous attempts to improve vulnerable ecosystems and ultimately formed an action plan to improve these attempts.Climate,ecosystems,and livelihoods for Sustainable Development Goals(SDGs),Great Green Wall Initiative(GGWI)for Sahara and Sahel,and China-Africa cooperation on science,technology,and innovation are three extra main sections concerned of the meeting.Separately,more specific topics as the complicated relationship between these natural processes and human activity,including pastoralism,soil restoration,and vegetation regenerate techniques,were fully discussed.Consultative meeting also identified the positive effects international collaboration can have on dryland regions,specifically in the capacity of sharing information,technology,and innovation on purpose to develop a joint proposal for long-term research programs in African arid and semi-arid areas.Moreover,meetings that review the progress made on ecosystem management for the sustainable livelihoods in Africa,identification of priority areas,and the development and implementation of ecosystem programs for proper research and collaboration in African arid and semi-arid zones,have been proposed as strategic recommendations to enhance the global partnership for sustainable development.Furthermore,as the outcomes of the workshop,there are three steps proposed to handle African dryland climate changes,several aspects suggested to solve current dilemmas of the GGWI,and a series of actions recommended for G-DEP related activities in Africa.

Resilience, Adaptability, and Regime Shifts Thinking: A Perspective of Dryland Socio-ecology System

Arid areas are widespread globally and support a third of the world’s population’s livelihoods. The increasing population, urbanization, land-use changes, and the climate significantly affect coupled natural and human systems and threaten environments and socio-ecological land systems. The degradation of drylands poses a severe and widespread threat to the lives of millions of people, especially in developing countries and in the global environment. This review assesses published literature on dryland socio-ecological systems to reveal current research trends and changes in research themes over time and introduces basic theories and advances in dryland socio-ecological system frameworks, resilience measurement, and regime shifts. Developing a more general but adaptable framework and a more practical strategy for long-term coordination and partnership and attaining specific insights into ecological services should receive more attention and be strengthened in future studies on drylands sustainability.