干旱区生态环境知识资源中心(Arid): Functional responses of the herbaceous plant community explain ecohydrological impacts of savanna shrub encroachment

Arid

DOI	10.1016/j.ppees.2019.125458
	Functional responses of the herbaceous plant community explain ecohydrological impacts of savanna shrub encroachment
	Geissler, Katja 1; Hahn, Claudia 2; Joubert, David 3; Blaum, Niels 1
通讯作者	Geissler, Katja
来源期刊	PERSPECTIVES IN PLANT ECOLOGY EVOLUTION AND SYSTEMATICS
ISSN	1433-8319
出版年	2019
卷号	39
英文摘要	Major drivers of savanna shrub encroachment are climatic conditions, CO2 and unsustainable grazing management including fire prevention. Although all drivers affect ecohydrological processes, and given that water is a seasonally scarce resource in savannas, it remains largely unclear how shrub encroachment itself affects hydrological conditions that feed back into water use and community assembly of the remaining plant community. Hence, understanding direct ecohydrological effects of shrubs that may limit the recovery of the perennial herbaceous vegetation in grazed areas and promote the establishment of shrub seedlings facilitates the identification of areas that are most sensitive to further encroachment. In our trait-based approach, we determined relationships among shrub cover, soil and plant trait characteristics sensitive to water limitation in 120 plots along a shrub cover gradient. We focused on two functional response traits indicating immediate drought stress and subsequent water use for drought stress recovery with associated competition for water (midday leaf/xylem water potential and diurnally recovery rate of leaf water potential), and three functional response traits indicating long-term stress adaptation and related resource use strategies (SLA, plant height and seed release height). To understand species assembly and the associated mechanisms of resource use, we calculated community weighted mean traits, intraspecific trait variability as a proxy for the mechanism of coexistence, and mean traits at plant functional type level including 2-year-old Acacia mellifera-saplings. We found a low intraspecific trait variability in drought stress recovery rate and height suggesting that competitive exclusion via active resource acquisition (i.e. water exploitation) played a minor role for community assembly in a shrub encroaching savanna. The dominant community assembly process was passive stress avoidance via resource conservation up to stress tolerance indicated by the high variability in SLA and midday leaf water potential. Correlations of traits with soil moisture suggest a rooting niche differentiation between annual and perennial grasses and that Acacia-shrub saplings within the first 50 cm of soil already escaped the highest drought stress. Interestingly, immediate drought stress for the herbaceous community was lowest on moderately shrub encroached sites and not on grass dominated sites. Since passive stress avoidance accompanied by a distinct stress tolerance in semi-arid savannas is more important than active competition, and assuming that the low drought stress of the herbaceous community at intermediate levels of shrub cover also applies to newly emerging shrub seedlings, these areas are likely to be most sensitive to further encroachment. As such, they should be considered as focal areas for prevention management.
英文关键词	Community-weighted means Drought stress Intraspecific variation Soil moisture Stress recovery Plant functional traits
类型	Article
语种	英语
国家	Germany ; Switzerland ; Namibia
收录类别	SCI-E
WOS记录号	WOS:000477762000003
WOS关键词	INTRASPECIFIC TRAIT VARIATION ; SEMIARID SAVANNA ; SUCCULENT KAROO ; WATER RELATIONS ; GROWTH ; FIRE ; DIVERSITY ; SOUTHERN ; ECOSYSTEMS ; RANGELANDS
WOS类目	Plant Sciences ; Ecology
WOS研究方向	Plant Sciences ; Environmental Sciences & Ecology
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/217928
作者单位	1.Univ Potsdam, Plant Ecol & Nat Conservat, Potsdam, Germany; 2.Univ Basel, Dept Environm Sci, Basel, Switzerland; 3.Namibia Univ Sci & Technol, Agr & Nat Resources Sci, Windhoek, Namibia
推荐引用方式 GB/T 7714	Geissler, Katja,Hahn, Claudia,Joubert, David,et al. Functional responses of the herbaceous plant community explain ecohydrological impacts of savanna shrub encroachment[J],2019,39.
APA	Geissler, Katja,Hahn, Claudia,Joubert, David,&Blaum, Niels.(2019).Functional responses of the herbaceous plant community explain ecohydrological impacts of savanna shrub encroachment.PERSPECTIVES IN PLANT ECOLOGY EVOLUTION AND SYSTEMATICS,39.
MLA	Geissler, Katja,et al."Functional responses of the herbaceous plant community explain ecohydrological impacts of savanna shrub encroachment".PERSPECTIVES IN PLANT ECOLOGY EVOLUTION AND SYSTEMATICS 39(2019).