INTRODUCTION
Factors limiting tree growth are among the most important information required for properly managing forests, either native or planted (Blasing et al. 1984). Regardless if the management goal is economical return or conservation, an informed decision will depend on what conditions determine tree performance and survival in certain communities or regions. Common limiting factor to tree growth include amount of sunlight, water availability, competition, edaphic condition, and others (Blasing et al. 1984). But although several components might be important for tree growth, specific regions will display specific challenges for tree growth (Figure 1). A study with Douglas fir demonstrated that tree ring width of individuals were positively correlated with precipitation and temperature of the previous winter, indicating that growth of limited by summer dryness (Chen et al. 2010). Another study with Scutia buxifolia also demonstrated correlation of previous year precipitation and temperature with growth of the next season (Lucas et al. 2018). These cases illustrate the importance to understand how local species or communities may respond more closely to specific climate factor.
Climate is a major driver of tree species development. Differences mainly in precipitation and temperature are usually key components for species development. High temperatures are associate with high flow of water due to high rates of evapotranspiration. In turn, high temperature can be associated with high productivity. However if water availability is low, high transpiration rates may cause embolism and damage to the hydraulic system. On the other side, temperatures below zero may cause water to freeze and not be available for photosynthesis thus limiting growth. Contrasting responses may arise from contrasting environments indicating key factors for tree growth in the distinct environments.
Figure 1. Taken from BOISVENUE and RUNNING, 2006. World map representing the main potential limiting factors related to tree growth for each region.
Tree rings can capture (and store) these tree responses to changing conditions (Lara and Villalba 1993). This creates a very convenient way to assess growth performance under different environmental conditions. By measuring tree ring widths it is possible to correlate growth to environmental conditions of that specific location (Figure 2). Response function analysis are the most common type of analysis performed for that end (Blasing et al. 1984). More specifically this analysis correlates tree ring width of a given year to precipitation and temperature of each month of that year. However, some trees have shown to respond even to previous year’s conditions. Thus correlations can be verified with environmental conditions that goes back as old as two years before the growth occurs. The reason for that is that ring growth of given year might have started in the year before in which the growing season started. Also other reasons might include events of embolism for example, in which bubbles are formed inside the tree conduits and blocks water transportation to the leaves for the next year or two. Some species can refill conduits for example, while other may not, thus making recovery times vary.
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Figure 2. Cross-sectional view of a tree stem showing growth rings. Green band represents the favorable growing season, yellow band represents season with poorer conditions. Both bands combined represent one growth ring, and, for many species, a single year. The width of the ring can indicate tree productivity on that given year.
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Tree rings can capture (and store) these tree responses to changing conditions (Lara and Villalba 1993). This creates a very convenient way to assess growth performance under different environmental conditions. By measuring tree ring widths it is possible to correlate growth to environmental conditions of that specific location. Response function analysis are the most common type of analysis performed for that end (Blasing et al. 1984). More specifically this analysis correlates tree ring width of a given year to precipitation and temperature of each month of that year. However, some trees have shown to respond even to previous year’s conditions. Thus correlations can be verified with environmental conditions that goes back as old as two years before the growth occurs. The reason for that is that ring growth of given year might have started in the year before in which the growing season started. Also other reasons might include events of embolism for example, in which bubbles are formed inside the tree conduits and blocks water transportation to the leaves for the next year or two. Some species can refill conduits for example, while other may not, thus making recovery times vary.
The International Tree Ring Data Base possess chronology data on for most of southern South America that can be used to infer plant-climate interaction for the region. This portion of the continent possess a mosaic of different vegetation types that are reflex of the climate diversity of the region (Olson et al. 2001). The latitude range as well as the different ecosystem’s histories accounts for a very diverse flora. Little is known about climate-plant interaction for the conditions of South America and this knowledge gap has important consequences for future management actions, especially in the face of climate change. Thus, this research aimed to take steps to create an overview of factors that limit growth in South America, using available data from the International Tree-Ring Data Base (from the National Oceanic and Atmosphere Administration - NOAA - website). By analyzing the available tree chronologies we aimed to answer the following questions:
Are precipitation and/or temperature key limiting factors of tree communities in Southern of South America?
If yes, what is the main period that affects tree growth?
This answers will allow us to understand if what is observed in other climates also applies for this region and to what extent.
If yes, what is the main period that affects tree growth?
This answers will allow us to understand if what is observed in other climates also applies for this region and to what extent.
REFERENCES
BLASING, T.J., SOLOMON, A.M., AND DUVICK, D.N. 1984. Response Functions Revisited. Tree-Ring Bull. 44: 1–15. doi:10.2307/2131215.
CHEN, P.Y., WELSH, C., AND HAMANN, A. 2010. Geographic variation in growth response of Douglas-fir to interannual climate variability and projected climate change. Glob. Chang. Biol. 16(12): 3374–3385. doi:10.1111/j.1365-2486.2010.02166.x.
LARA, A., AND VILLALBA, R. 1993. A 3620-year temperature record from Fitzroya cupressoides tr. Science (80-. ). 260(5111): 1104. Available from http://ezproxy.puc.cl/docview/213568434?accountid=16788%5Cnhttp://sfx.alerta.cl/sfxpuc41??url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&genre=article&sid=ProQ:ProQ%3Aagriculturejournals&atitle=A+3620-year+temperature+record+from+Fitzroya+cu.
LUCAS, C., PUCHI, P., PROFUMO, L., FERREIRA, A., AND MUÑOZ, A. 2018. Effect of climate on tree growth in the Pampa biome of Southeastern South America: First tree-ring chronologies from Uruguay. Dendrochronologia 52(October): 113–122. Elsevier. doi:10.1016/j.dendro.2018.10.004.
OLSON, D.M., ALLNUTT, T.F., RICKETTS, T.H., KURA, Y.U.M.I.K.O., LAMOREUX, J.F., WESLEY, W., HEDAO, P., AND KASSEM, K.R. 2001. Terrestrial Ecoregions of the World: A New Map of Life on Earth. Bioscience 51(11): 933–938.
BLASING, T.J., SOLOMON, A.M., AND DUVICK, D.N. 1984. Response Functions Revisited. Tree-Ring Bull. 44: 1–15. doi:10.2307/2131215.
CHEN, P.Y., WELSH, C., AND HAMANN, A. 2010. Geographic variation in growth response of Douglas-fir to interannual climate variability and projected climate change. Glob. Chang. Biol. 16(12): 3374–3385. doi:10.1111/j.1365-2486.2010.02166.x.
LARA, A., AND VILLALBA, R. 1993. A 3620-year temperature record from Fitzroya cupressoides tr. Science (80-. ). 260(5111): 1104. Available from http://ezproxy.puc.cl/docview/213568434?accountid=16788%5Cnhttp://sfx.alerta.cl/sfxpuc41??url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&genre=article&sid=ProQ:ProQ%3Aagriculturejournals&atitle=A+3620-year+temperature+record+from+Fitzroya+cu.
LUCAS, C., PUCHI, P., PROFUMO, L., FERREIRA, A., AND MUÑOZ, A. 2018. Effect of climate on tree growth in the Pampa biome of Southeastern South America: First tree-ring chronologies from Uruguay. Dendrochronologia 52(October): 113–122. Elsevier. doi:10.1016/j.dendro.2018.10.004.
OLSON, D.M., ALLNUTT, T.F., RICKETTS, T.H., KURA, Y.U.M.I.K.O., LAMOREUX, J.F., WESLEY, W., HEDAO, P., AND KASSEM, K.R. 2001. Terrestrial Ecoregions of the World: A New Map of Life on Earth. Bioscience 51(11): 933–938.