Initiating and promoting the aquatic ecosystem health concept: the Society and the Journal

Since the 1970's the management of aquatic habitats has changed from piecemeal monitoring to the ecosystem approach; this was initiated in the North American Great Lakes, comprising social, economic, and environmental aspects. The information included in this paper is based on the presentation made at the Seminar On Ecosystem Approach To Water Management held in Oslo, Norway during 1991. Recently, the multidisciplinary, holistic, and integrated concept of ecosystem health has emerged, and is being advanced for the implementation of an ecosystem approach to environmental management, which has resulted in the formation of an international society (Aquatic Ecosystem Health & Management Society) and the publication of a primary journal (Journal of Aquatic Ecosystem Health). The information has been updated to incorporate new developments and recent progress about the Society and the journal since the Oslo Seminar.     

A data-driven framework to model the organism–environment system

Organisms modify their development and function in response to the environment. At the same time, the environment is modified by the activities of the organism. Despite the ubiquity of such dynamical interactions in nature, it remains challenging to develop models that accurately represent them, and that can be fitted using data. These features are desirable when modeling phenomena such as phenotypic plasticity, to generate quantitative predictions of how the system will respond to environmental signals of different magnitude or at different times, for example, during ontogeny. Here, we explain a modeling framework that represents the organism and environment as a single coupled dynamical system in terms of inputs and outputs. Inputs are external signals, and outputs are measurements of the system in time. The framework uses time-series data of inputs and outputs to fit a nonlinear black-box model that allows to predict how the system will respond to novel input signals. The framework has three key properties: it captures the dynamical nature of the organism–environment system, it can be fitted with data, and it can be applied without detailed knowledge of the system. We study phenotypic plasticity using in silico experiments and demonstrate that the framework predicts the response to novel environmental signals. The framework allows us to model plasticity as a dynamical property that changes in time during ontogeny, reflecting the well-known fact that organisms are more or less plastic at different developmental stages.     

2000—2019年四川省植被恢复成效与影响因素

国家实施天然林资源保护工程与退耕还林等生态建设工程,为构筑长江上游生态屏障、促进长江流域经济可持续发展做出了突出贡献;评估退耕还林等生态工程实施后植被恢复成效及影响因素是促进区域植被恢复优化与生态环境改善的关键一步。基于MODIS MOD13Q1数据,应用Theil Sen斜率与Mann-Kendall趋势检验、“基线”评价方法、时空地理加权回归模型等量化不同时间尺度的植被时空变化、恢复成效和恢复机制。结果表明(1)植被覆盖状况良好,截止2019年底,四川省91%的区域植被出现增长,四川盆地东北部、四川省南部地区以及东南部乌蒙山、川西北高原地区植被覆盖较高;成都市内以及周围市区植被覆盖率较低。(2)植被恢复成效时空差异显著,占全省面积98.68%的区域植被恢复成效明显,高值区面积占比71.47%,集中于除成都平原外的四川省绝大部分区域。(3)气候变化对植被变化的影响以不显著为主,气温、降水对四川省植被恢复影响微弱,海拔和>35°坡度面积比等地理环境因子则以弱抑制作用为主。(4)在相对平稳的气候背景下,人均财政支出、耕地面积与人均GDP所代表的社会经济因素是植被恢复成效改善的重要影...     

变化环境下火干扰研究进展

火是地球系统的重要过程,也是一种剧烈的环境干扰因素。火是生态系统变化的驱动力和催化剂,调节着生态系统的结构和功能,同时反馈给气候系统。近年来,世界多个国家相继爆发了历史上罕见的极端火事件,使得火干扰、气候变化和人类活动之间的相互作用关系得到了空前的关注。主要从3个方面回顾了变化环境下火干扰研究的进展,包括(1)火干扰的时空格局;(2)火干扰的驱动机制;(3)火干扰的生态效应。概括起来,遥感技术的发展使得火监测精度不断提高,对火时空格局的刻画由过去侧重火燃烧面积单一因素转向具有多重属性的火干扰体系。气候变化和人类活动共同决定着火干扰的分布格局、频率和强度,考虑气候的季节性能够提高火干扰的预测能力。火干扰调节着生态系统的草木平衡,对于生物多样性和生境的维持非常重要。此外,火干扰通过生物质燃烧释放的大量温室气体影响大气组成和空气质量,同时通过改变地表状况和陆-气相互作用来影响气候系统。正确理解气候-植被-火之间的相互作用和反馈机制有助于未来火干扰体系的预测。随着高温、大风、干旱等极端气候事件增多,未来全球大部分区域火发生的风险增加,但是人类活动可能会使火和气候之间的关系发生解耦。可持续的火管...     

荒漠植物不同功能群性状特征及其与土壤环境的关系

研究不同功能群植物性状差异及其与土壤环境关系对于充分掌握植物的环境适应策略至关重要。以艾比湖流域为研究区,利用荒漠植物的植物高度、叶片碳、氮、磷、硫、钾、钙、钠、镁含量等9个性状,将高、低土壤水盐环境下的植物划分为5个功能群,分析不同功能群的植物组成、性状差异及其与土壤环境的关系。结果表明：(1)不同土壤水盐环境下,其植物功能群组成不同;其中白刺、胡杨和罗布麻在两个土壤水盐环境下的功能群中均存在。(2)植物的功能性状在不同土壤水盐环境下也发生了适应性的变化。高土壤水盐环境下3个功能群的植物高度、叶片碳、氮、磷和钙含量显著高于低土壤水盐环境功能群(P<0.05);低土壤水盐环境下2个功能群的植物叶片硫、钠和镁含量高于高土壤水盐环境功能群。(3)土壤含水量(SVWC)、电导率(EC)、pH以及土壤磷含量对荒漠植物功能性状影响较大。在高土壤水盐环境下,EC、pH与植物高度,叶片钾、钙含量正相关,与叶片硫含量负相关;在低土壤水盐环境下,SVWC、EC与植物高度呈显著正相关(P<0.05)。研究有助于理解荒漠植物对极端环境的适应对策,为保护荒漠地区生物多样性提供理论依据。     

高原鼢鼠土丘对矮嵩草草甸植被演替及土壤营养元素的作用

本文研究了矮蒿草草甸上高原酚鼠土丘的出现率及其对植被的覆盖状况,土丘高度的下降及其直径的变化,土丘植物地上生物量和土丘营养元素含量。高原鼢鼠土丘出现率为242个/只/年,合土壤干重为1023.82公斤/只/年,对植被的覆盖面积高达22.53平方米/只/年。土丘在地表滞留时间约1年,处于不同演替阶段植被区域内出现的土丘,其植物地上生物量间的差异显著。5月前,在原生植被区出现的土丘,经4个月后,土丘边缘形成环状富草区,士丘边缘至中心区形成环状贫草区,而土丘中心仍处于无草状况。在次生植被区上的土丘则无此现象。新土丘除速效钾的含量与对照区无显著差异外,速效氮、磷的含量显著地高于对照区。旧土丘土壤中的速效氮、磷、钾含量均低于新土丘,但氮、磷的含量仍高于对照区。     

Daily Rhythms of Body Temperature in Acornys russatus: The Response to Chemical Signals Released by Acomys cahirinus

Two species of spiny mice of the genus Acomys—the golden spiny A. russaturs and the common spiny A. cuhirinus—are syrnpatnc in the and and hot parts of the Rift Valley in Israel. The coexistence of these two species is due to exclusion of A. russatus mice by A. cuhirinus mice from nocturnal activity. The aim of this research was to study if odor signals released by A. cahirinus mice can play a role in the exclusion of A. russatus mice. A. russatus mice with an implanted transmitter recording body temperature (T_b) were kept alone in a metabolic chamber under constant conditions of ambient temperature (27°C) and photoperiod (12 h light: 12 h dark). After 5 days of recording, chemical signals from an A. cuhirinus mouse were added through the air tube going into the metabolic chamber of the A. russatus mice. This treatment caused a shift of ∼ 2 h inT_b daily rhythm of the naive tested A. russutus mice, whereas no shift was observed in A. russatus mice that had been kept in the same room with the A. cahirinus mouse before measurements. These results strongly support the idea that chemical signals released by A. cahirinus mice can entrain the T_b rhythms of A. russatus mice. Therefore, it may be assumed that the exclusion of A. russatus mice from nocturnal activity by A. cuhirinus mice could be achieved through the odor released by the latter.     

Canopy photosynthetic production in a Japanese larch forest. II. Estimation of the canopy photosynthetic production

Seasonal changes and yearly gross canopy photosynthetic production were estimated for an 18 year old Japanese larch (Larix leptolepis) forest between 1982 and 1984. A canopy photosynthesis model was applied for the estimation, which took into account the effect of light interception by the non-photosynthetic organs. Seasonal changes in photosynthetic ability, amount of canopy leaf area and light environment within the canopy were also taken into account. Amount of leaf area was estimated by the leaf area growth of a single leaf. The change of light environment within the canopy during the growing season was estimated with a light penetration model and the leaf increment within the canopy. Canopy respiration and surplus production were calculated as seasonal and yearly values for the three years studied. Mean yearly estimates of canopy photosynthesis, canopy respiration and surplus production were 37, 13 and 23 tCO₂ ha⁻¹ year⁻¹, respectively. Vertical trend, seasonal changes and yearly values of the estimates were analyzed in relation to environmental and stand factors.     

Diurnal changes in phosphoenolpyruvate carboxylase and pyruvate, orthophosphate dikinase properties in the natural environment: interplay of light and temperature in a C4 thermophile

Activities of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) were measured in leaf extracts of field grown Amaranthus paniculatus L. (C₄) during a natural diurnal irradiance and temperature pattern. Enzyme assays were run at both fixed (30°C) and the corresponding leaf temperature at the time of harvest. Light activation of PEP carboxylase (PEPCase) at fixed assay temperatures was expressed as a decrease in S_0–5 (PEP) after a threshold (> 330 μmol m^–2 s^–1) photon fluence rate was surpassed at noon. Earlier in the morning, increase in apparent enzyme affinity for PEP was observed when the assay was run at leaf temperature, indicating a physiologically meaningfull effect of temperature on S^0.5 (PEP). The 3.3-fold increase in PEPCase activity at low PEP and fixed assay temperature between the minimal and maximal irradiance and temperature hours of the day, became 12.8-, 11.5- and 7.4-fold when assays were run at the corresponding leaf temperature during three diurnal cycles with respective temperature differences (max minus min) of 9.0, 8.3 and 7.4°C. The extent of malate inhibition was the same for both day and night forms of PEPCase assayed at 35°C, but increased considerably with night enzyme at 25°C. The results indicate that light increases the apparent affinity of PEPCase for PEP and that at lower temperatures malate becomes more inhibitory. Pyruvate orthophosphate dikinase activity started to increase immediately after sunrise and the 10-fold increase at fixed temperature became 14.8-, 14.2- and 13.1-fold when assays were run at the above leaf temperatures. This indicates that the light effect predominates with pyruvate, orthophosphate dikinase, while with phosphoenolpyravate carboxylase, light and temperature co-operate to increase the day enzyme activities.