Defoliation-induced tree growth declines are jointly limited by carbon source and sink activities

Abstract Tree growth is generally considered to be temperature-limited at upper elevation treelines. Yet, climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polyepis tarapacana, the world’s highest elevation tree-species found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4,400 meters in elevation, along a 500-km latitude-aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon-sink processes along the gradient. Current-growing season temperature regulated RWI at wetter-northern sites, while prior-growing season precipitation determined RWI at arid-southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site-water availability. In contrast, warm and dry growing-seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern-drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. The manuscript also highlights a coupling and decoupling of physiological processes at leaf level versus wood formation depending on their respectively uniform and distinct sensitivity to climate. This study contributes to better understand and predict the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano.

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Carbon Source and Sink Analysis of Rhizosphere Micro-ecosystem of Calamagrostis Angustifolia in Xiaoxing’anling in Northeast China

Proceedings of the 2015 International Conference on Education, Management, Information and Medicine ◽

10.2991/emim-15.2015.244 ◽

2015 ◽

Author(s):

Xiuping Cai ◽

Jiguang Li ◽

Qishuo Wang ◽

Hui Sun ◽

Wei Xie ◽

...

Keyword(s):

Carbon Source ◽

Northeast China ◽

Source And Sink ◽

Calamagrostis Angustifolia

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Modelling tree growth taking into account carbon source and sink limitations

10.1101/063594 ◽

2016 ◽

Cited By ~ 1

Author(s):

Amaury Hayat ◽

Andrew J. Hacket-Pain ◽

Hans Pretzsch ◽

Tim Tito Rademacher ◽

Andrew D. Friend

Keyword(s):

Carbon Source ◽

Tree Growth ◽

Environmental Changes ◽

Tree Height ◽

Cellular Growth ◽

Control Mechanisms ◽

Initial State ◽

Individual Tree ◽

Runge Kutta ◽

Over Time

AbstractIncreasing CO2 concentrations are strongly controlled by the behaviour of undisturbed forests, which are believed to be a major current sink of atmospheric CO2. There are many models which predict forest responses to environmental changes but they are almost exclusively carbon source (i.e. photosynthesis) driven. Here we present a model for an individual tree that takes into account also the intrinsic limits of meristems and cellular growth rates, as well as control mechanisms within the tree that influence its diameter and height growth over time. This new framework is built on process-based understanding combined with differential equations solved by the Runge-Kutta-Fehlberg (RKF45) numerical method. It was successfully tested for stands of beech trees in two different sites representing part of a long-term forest yield experiment in Germany. This model provides new insights into tree growth and limits to tree height, and addresses limitations of previous models with respect to sink-limited growth.Author SummaryGreenhouse gas emissions, in particular of CO2, have emerged as one of the most important global concerns, and it is therefore important to understand the behaviour of forests as they absorb and store a very large quantity of carbon. Most models treat forests as boxes with growth only driven by photosynthesis, while their actual growth depends also on many other important processes such as the maximal rate at which individual cells can grow, the influences of temperature and soil moisture on these cells, and the control that the tree has on itself through endogenous signalling pathways. Therefore, and with inspiration from process-based understanding of the biological functioning of trees, we have developed a model which takes into account these different factors. We first use this knowledge and additional basic assumptions to derive a system of several equations which, when solved, enable us to predict the height and the radius of an individual tree at a given time, provided that we have enough information about its initial state and its surroundings. We use the Runge-Kutta-Fehlberg mathematical method to obtain a numerical solution and thus predict the development of the height and radius of an individual tree over time under specified conditions.

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Study on the Spatial Expansion Driving Force Mechanism of Carbon Source and Sink at Urban Fringe Areas

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.587-589.530 ◽

2014 ◽

Vol 587-589 ◽

pp. 530-535

Author(s):

Meng Lin Qin ◽

Jing Ya ◽

Jing Zhao ◽

Hang Li ◽

Xi Na Wei

Keyword(s):

Carbon Source ◽

Driving Force ◽

Urban Fringe ◽

Spatial Expansion ◽

Planning And Control ◽

Mass Psychology ◽

Point Analysis ◽

Natural Terrain ◽

Force Mechanism ◽

Source And Sink

Urban fringe areas are the core carrier for the balance of carbon source and sink in urban regions and the concentration area for conversion of land used for carbon emission and sink. With the support of interpreted data of remote sensing images, through combination of the “Breakaway Point” Analysis Approach and the Index Bound Method, the paper obtains the range of fringe areas of Nanning City and discusses about the driving force mechanism of spatial expansion of lands used for carbon source and sink at the urban fringe areas. The results show that conditions of natural terrain, social and economic factors, development of communication and transportation, urban planning and control, social culture and mass psychology form the driving force mechanism of spatial expansion of lands used for carbon source and sink at urban fringe areas.

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