中国东部季风区植被气候生产潜力的时空特征

以中国东部季风区为研究区域、植被气候生产潜力为研究对象,以英国东英格利亚大学气候研究所公布的气候变化数据库(CRU TS v.4.06)中0.5°×0.5°月尺度时空分辨率的降水和气温数据集的气象数据(时间尺度为1981—2021年)、中山大学陆-气相互作用研究组2013年开发的中国陆地表面土壤数据库的土壤数据为数据源,采用迈阿密模型(Miami)、桑斯威特纪念模型(Thomthwaite Memorial)分析1981—2021年中国东部季风区植被气候生产潜力的时空特征,采用冗余分析(RDA)法分析植被气候生产潜力与土壤理化性质相关性。结果表明:过去40a,中国东部季风区气温生产潜力、降水生产潜力、蒸散生产潜力的时间演变,均分为2个阶段,气温生产潜力的第Ⅰ阶段为1981—2001年、第Ⅱ阶段为2002—2021年,降水生产潜力的第Ⅰ阶段为1981—2014年、第Ⅱ阶段为2014—2021年,蒸散生产潜力的第Ⅰ阶段为1981—2013年、第Ⅱ阶段为2013—2021年,2个阶段均呈现出生产潜力增加趋势,其中第Ⅱ阶段生产潜力增加幅度显著高于第Ⅰ阶段。气温生产潜力、降水生产潜力和蒸散生产潜力均存在1个22 a的显著周期转变,敏感性分析显示气温和降水均对蒸散生产潜力有显著正相关影响。在空间上,气温生产潜力、降水生产潜力、蒸散生产潜力,都呈现出从华南地区往东北地区递减的趋势,且第Ⅱ阶段植被气候生产潜力的增速显著高于第Ⅰ阶段,第Ⅱ阶段增速显著的区域多出现在高值区。冗余分析结果显示,东部季风区土壤表层理化性质对降水生产潜力、蒸散生产潜力有显著抑制作用,对气温生产潜力有显著的促进作用。

Responses of Vegetation and Primary Production in North-South Transect of Eastern China to Global Change Under Land Use Constraint

A regional model of vegetation dynamics was revised to include land use as a constraint to vegetation dynamics and primary production processes. The model was applied to a forest transect in eastern China (NSTEC, North-South transect of eastern China) to investigate the responses of the transect to possible future climatic change. The simulation result indicated that land use has profound effects on vegetation transition and primary production. In particular, land use reduced competition among vegetation classes and tended to result in less evergreen broadleaf forests but more shrubs and grasses in the transect area. The simulation runs with land use constraint also gave much more realistic estimation about net primary productivity as well as responses of the productivity to future climatic change along the transect. The simulations for future climate scenarios projected by general circulation models (GCM) with doubled atmospheric CO2 concentration predicted that deciduous broadleaf forests would increase, but conifer forests, shrubs and grasses would decrease. The overall effects of doubling CO2 and climatic changes on NSTEC were to produce an increased net primary productivity (NPP) at equilibrium for all seven GCM scenarios. The predicted range of NPP variation in the north is much larger than that in the south.

Assessing adaptability and response of vegetation to glacier recession in the afro-alpine moorland terrestrial ecosystem of Rwenzori Mountains

The objective of this study was to explore vegetation adaptability in a changing afro-alpine moorland terrestrial ecosystem on Mt. Rwenzori and to determine whether there were any links with response of vegetation to glacier recession. We analyzed the composition and distribution of plant species in relation to soils, geomorphic processes, and landscape positions in the Alpine zone. To accomplish this objective, archival data sources and published reports for this ecosystem were reviewed. A field trip was conducted in 2010 to study in detail seven vegetation sampling plots that were systematically selected using GIS maps and a nested-quadrat sampling design framework along an altitudinal gradient in the lower and upper alpine zones. Using these sampling plots, 105 vegetation and 13 soil samples were assessed in the alpine zone. Soil samples were taken for laboratory testing and analysis. The results show statistically significant differences in pH, OM, N, P, Ca, Mg, and K pools between soils samples drawn from the lower and upper alpine sites （p 〈 0.0033）. Furthermore, we observed a significant vegetation formation with numerous structural forms, but there was a limited diversity of speeies. The most significant forms included Alchemilla carpets, Bogs, Dendrosenecio woodland, and Scree slopes. The lower alpine area （3500-3900 masl） had a more diverse plant species than other areas, especially Alchemilla argyrophylla and Dendrosenecio adnivalis species that were evident due to well-drained deeper soils. The Alchemilla subnivalis were evident at a higher altitude of above 4000 mask Shifts in the Astareeeae （e.g. Senecio species） were particularly prominent even on recently deglaciated areas. The spatial variations of species distribution, structure, and composition suggest there are serious implications in terms of ecosystem adaptability, resilience, and stability that require further evaluation.

陆地氧循环过程研究进展

氧循环是地球系统重要的生物化学循环之一,其变化对地球的宜居性有着重要影响。工业革命以来,由于人类活动的影响,现代氧循环相比地质年代的氧循环发生了巨大的变化。陆地氧循环过程在现代氧循环中具有举足轻重的作用。从陆地植被生态系统产氧、陆地燃料燃烧耗氧等方面对已有陆地氧循环过程研究进行了回顾,表明:①陆地过程的变化会直接造成大气氧气浓度的波动,对大气氧气浓度有预测作用;②陆地氧循环过程反映了生态系统对人类活动与气候变化的响应,对评估生态安全具有指示作用。通过探究陆地氧循环过程对气候变化与人类活动的反馈,有助于预测未来大气氧气浓度的变化,为未来区域发展政策制定提供参考。

Remote sensing based monitoring of interannual variations in vegetation activity in China from 1982 to 2009

Terrestrial vegetation is one of the most important components of the Earth's land surface. Variations in terrestrial vegetation directly impact the Earth system's balance of material and energy. This paper describes detected variations in vegetation activity at a national scale for China based on nearly 30 years of remote sensing data derived from NOAA/AVHRR(1982–2006) and MODIS(2001–2009). Vegetation activity is analyzed for four regions covering agriculture, forests, grasslands, and China's Northwest region with sparse vegetation cover(including regions without vegetation). Relationships between variations in vegetation activity and climate change as well as agricultural production are also explored. The results show that vegetation activity has generally increased across large areas, especially during the most recent decade. The variations in vegetation activity have been driven primarily by human factors, especially in the southern forest region and the Northwest region with sparse vegetation cover. The results further show that the variations in vegetation activity have influenced agricultural production, but with a certain time lag.

Recent leveling off of vegetation greenness and primary production reveals the increasing soil water limitations on the greening Earth

Global vegetation photosynthesis and productivity have increased substantially since the 1980s,but this trend is heterogeneous in both time and space.Here,we categorize the secular trend in global vegetation greenness into sustained greening,sustained browning and greening-to-browning.We found that by 2016,increased global vegetation greenness had begun to level off,with the area of browning increasing in the last decade,reaching 39.0 million km^(2)(35.9%of the world’s vegetated area).This area is larger than the area with sustained increasing growth(27.8 million km^(2),26.4%);thus,12.0%±3.1%(0.019±0.004 NDVI a^(-1))of the previous earlier increase has been offset since 2010(2010–2016,P<0.05).Global gross primary production also leveled off,following the trend in vegetation greenness in time and space.This leveling off was caused by increasing soil water limitations due to the spatial expansion of drought,whose impact dominated over the impacts of temperature and solar radiation.This response of global gross primary production to soil water limitation was not identified by land submodels within Earth system models.Our results provide empirical evidence that global vegetation greenness and primary production are offset by water stress and suggest that as global warming continues,land submodels may overestimate the world’s capacity to take up carbon with global vegetation greening.