Tracheid development under a drought event producing intra-annual density fluctuations in the semi-arid China

Intra-annual density fluctuation (IADF) is a structural modification of the tree ring in response to fluctuations in the weather. The expected changes in monsoon flow would lead to heterogeneous moisture conditions during the growing season and increase the occurrence of IADF in trees of the arid ecosystems of continental Asia. To reveal the timings and physiological mechanisms behind IADF formation, we monitored cambial activity and wood formation in Chinese pine (Pinus tabuliformis) during 2017–2019 at three sites in semi-arid China. We compared the dynamics of xylem formation under a drought event, testing the hypothesis that drought affects the process of cell enlargement and thus induces the production of IADF. Wood microcores collected weekly from April to October were used for anatomical analyses to estimate the timings of cambial activity, and the phases of enlargement, wall thickening, and lignification of the xylem. The first cells started enlargement from late April to early May. The last latewood cells completed differentiation in mid-September. Trees produced IADF in 2018. During that year, a drought in June limited cell production in the cambium, only 36% of the xylem cells being formed in IADF trees, compared to 68% in normal tree rings. IADF cells enlarged under drought in early July and started wall thickening during the rainfall events of late July. The drought restricted cell enlargement and affected wall thickening, resulting in narrow cells with wide walls. Cambium and cell enlargement recovered from the abundant rainfall, producing a new layer with large earlywood tracheids. IADF is a specific adaptation of trees to cope with water deficit events occurring during xylem formation. Our findings confirmed the hypothesis that the June-July drought induces latewood-like IADFs by limiting the process of cell enlargement in the xylem. Our finding suggests a higher occurrence of IADF in trees of arid and semi-arid climates of continental Asia if the changes to monsoon flows result in more frequent drought events during the earlywood formation in June.

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Impacts of drying and reflooding on water quality of a tropical semi-arid reservoir during an extended drought event

Acta Limnologica Brasiliensia ◽

10.1590/s2179-975x6918 ◽

2019 ◽

Vol 31 ◽

Author(s):

Jéssica Nayara de Carvalho Leite ◽

Vanessa Becker

Keyword(s):

Water Quality ◽

Electrical Conductivity ◽

Chlorophyll A ◽

Total Phosphorus ◽

Algal Biomass ◽

Soluble Reactive Phosphorus ◽

Drought Event ◽

Reactive Phosphorus ◽

Semi Arid

Abstract Aim The aim of this study was to analyze the water quality of a tropical, semi-arid reservoir after a reflooding. In terms of impact on water quality after a drought event, it is expected that there will be improvements with the reflooding. Less algal biomass, increased water transparency, decreased turbidity and low nutrient concentration. Methods This study was performed in a tropical, semi-arid man-made lake (Dourado Reservoir), during an extended drought period. This study consisted of a comparison of three distinct periods determined by water accumulation. The limnological variables, including water transparency, turbidity, electrical conductivity, pH, total phosphorus, soluble reactive phosphorus, and chlorophyll-a were analyzed. A principal component analysis (PCA) was also performed to verify the patterns of the variables in relation to the sample units in the studied periods. Results After water renewal, there was an expressive reduction in chlorophyll-a. Electrical conductivity, pH, and turbidity variables also reduced after the reflooding, indicating an improvement in water quality. There was no reduction in total phosphorus and soluble reactive phosphorus after the reflooding compared to the previous periods. Conclusions The significant reduction in algal biomass after reflooding in Dourado indicates water quality improvement in terms of eutrophication due to the change of the trophic state from eutrophic to mesotrophic.

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Droughts and governance impacts on water scarcity: an~analysis in the Brazilian semi-arid

Proceedings of the International Association of Hydrological Sciences ◽

10.5194/piahs-369-129-2015 ◽

2015 ◽

Vol 369 ◽

pp. 129-134 ◽

Cited By ~ 4

Author(s):

A. C. S. Silva ◽

C. O. Galvão ◽

G. N. S. Silva

Keyword(s):

Climate Change ◽

Water Management ◽

Climate Variability ◽

Extreme Events ◽

Water Scarcity ◽

Ecological Systems ◽

Drought Event ◽

Social Ecological Systems ◽

Social Ecological ◽

Semi Arid

Abstract. Extreme events are part of climate variability. Dealing with variability is still a challenge that might be increased due to climate change. However, impacts of extreme events are not only dependent on their variability, but also on management and governance. In Brazil, its semi-arid region is vulnerable to extreme events, especially droughts, for centuries. Actually, other Brazilian regions that have been mostly concerned with floods are currently also experiencing droughts. This article evaluates how a combination between climate variability and water governance might affect water scarcity and increase the impacts of extreme events on some regions. For this evaluation, Ostrom's framework for analyzing social-ecological systems (SES) was applied. Ostrom's framework is useful for understanding interactions between resource systems, governance systems and resource users. This study focuses on social-ecological systems located in a drought-prone region of Brazil. Two extreme events were selected, one in 1997–2000, when Brazil's new water policy was very young, and the other one in 2012–2015. The analysis of SES considering Ostrom's principle "Clearly defined boundaries" showed that deficiencies in water management cause the intensification of drought's impacts for the water users. The reasons are more related to water management and governance problems than to drought event magnitude or climate change. This is a problem that holdup advances in dealing with extreme events.

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Increasy eutrophication symptoms during a prolonged drought event in tropical semi-arid reservoirs, Brazil

RBRH ◽

10.1590/2318-0331.262120210097 ◽

2021 ◽

Vol 26 ◽

Author(s):

Diógenes Fernandes dos Santos ◽

Jonathan Mota da Silva ◽

Vanessa Becker

Keyword(s):

Trophic State ◽

Temporal Trend ◽

Standardized Precipitation Index ◽

Principal Component ◽

Water Volume ◽

Drought Event ◽

Drought Period ◽

Prolonged Drought ◽

The Standardized Precipitation Index ◽

Semi Arid

ABSTRACT Eutrophication is a global problem and an important cause of the ecological health degradation of aquatic ecosystems. The aim was to evaluate the effect of prolonged drought period (2012 to 2019) on the trophic state of two Brazilian semi-arid reservoirs, Boqueirão de Parelhas (BOQ) and Passagem das Traíras (TRA). The work was carried out according to a drought classification system, based on the Standardized Precipitation Index (SPI), with an aggregated timescale of 36 months, defining three periods. In the Period I, higher values of Secchi and lower values of turbidity, solids, nutrients and chlorophyll-a were registered, when compared to the other periods, mainly in BOQ. The principal component analyses of both reservoirs reveled a showed a temporal trend of the sample units according to the consequences of the prolonged drought. The results indicated changes in limnological variables due to the reduction of accumulated water volume, and they demonstrated that prolonged droughts impact the intensification of eutrophication in both systems. The trophic state of the BOQ reservoir was changed from mesotrophic to eutrophic as a consequence of the drought, while in TRA the eutrophic state remained, but with more intensified symptoms, with higher concentration values of nutrients, solids and algal biomass.

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Climate Variability, Climate Change and Social Vulnerability in the Semi-arid Tropics

10.1017/cbo9780511608308 ◽

1996 ◽

Cited By ~ 42

Keyword(s):

Climate Change ◽

Climate Variability ◽

Social Vulnerability ◽

Semi Arid

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Ferrihydrite dissolution at the root zone of crops under semi-arid condition controls the plant uptake of uranium and arsenic

10.1021/scimeetings.0c03694 ◽

2020 ◽

Author(s):

Arindam Malakar ◽

Michael Kaiser ◽

Daniel D. Snow ◽

Harkamal Walia ◽

Chittaranjan Ray

Keyword(s):

Plant Uptake ◽

Root Zone ◽

Arid Condition ◽

Semi Arid

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Life strategies in a semi-arid grassland community — mechanisms of dispersal and reproduction within Lapiedro martinezii-Stipetum tenacissimae (Southeastern Spain)

Feddes Repertorium ◽

10.1002/fedr.4921100310 ◽

1999 ◽

Vol 110 (3-4) ◽

pp. 265-285 ◽

Cited By ~ 1

Author(s):

I. Hensen

Keyword(s):

Life Strategies ◽

Grassland Community ◽

Southeastern Spain ◽

Semi Arid

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THE CLASSIFICATION OF LAND ACCORDING TO THE DEGREE OF RABBIT INFESTATION IN CENTRAL OTAGO

Proceedings of the New Zealand Grassland Association ◽

10.33584/jnzg.1987.48.1792 ◽

1987 ◽

pp. 65-70

Author(s):

I.G.C. Kerr ◽

J.M. Williams ◽

W.D. Ross ◽

J.M. Pollard

Keyword(s):

Carrying Capacity ◽

Mediterranean Climate ◽

Natural Habitat ◽

Public Funding ◽

Soil Survey ◽

European Rabbit ◽

Cultural Modification ◽

Classification Information ◽

Semi Arid

The European rabbit (Oryctolagus cuniculus) introduced into New Zealand in the 183Os, has consistently flourished in Central Otago, the upper Waitaki, and inland Marlborough, all areas of mediterranean climate. It has proved difficult to manage in these habitats. The 'rabbit problem' is largely confined to 105,000 ha of low producing land mostly in semi arid areas of Central Otago. No field scale modifications of the natural habitat have been successful in limiting rabbit numbers. The costs of control exceed the revenue from the land and continued public funding for control operations appears necessary. A system for classifying land according to the degree of rabbit proneness is described. Soil survey and land classification information for Central Otago is related to the distribution and density of rabbits. This intormation can be used as a basis for defining rabbit carrying capacity and consequent land use constraints and management needs. It is concluded that the natural rabbit carrying capacity of land can be defined by reference to soil survey information and cultural modification to the natural vegetation. Classification of land according to rabbit proneness is proposed as a means of identifying the need for, and allocation of, public funding tor rabbit management. Keywords: Rabbit habitat, rabbit proneness, use of rabbit prone land.

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