' Seasonal Changes of Cold Resistance of Proteaceae of the South Chilean Laurel

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  Seasonal changes of cold resistance of Proteaceae of the South Chilean laurel forest* L. Steubing l, M. Alberdi 2 & H. Wenzel 2 Institute of Plant Ecology, Justus Liebig University, Heinrich-BufJ: Ring 38, D 6300 Gieflen, W. German), 2 lnstituto de Botanica, Universidad Austral de Chile, Valdivia, Chile Keywords: Cold-resistance, Laurel forest, Proteaceae, Rain forest, South Chile Abstract Seasonal changes in cold-resistance in five Proteaceae: Gevuina avellana, Lomatia hirsuta, Lomatia dentata, Lomatiaferruginea and Embothrium coccineum were studied in the Botanical Garden, U niversidad Austral de Chile in Valdivia, Chile. All species presented such changes in relation to the minimum air temperatures but not in relation to rainfall. Cold-resistance increased together with the temperature decrease from March to May. Maximum resistance was observed in winter June to August). The spring temperature increase caused a decrease of cold-resistance, which reached its maximum from spring November) to summer December to February). The results obtained for cold-resistance correspond to the weather conditions found in natural biotopes of the species. Introduction Weinberger et al. 1973) and Alberdi et al. 1974) provided data on the drought resistance of selected species of the temperate rainforests of South Chile laurel forests according to Oberdorfer, 1973. For 53 evergreen woody species a relation between geo- graphical distribution and drought adaptation was indicated. In the investigated araukano-patagonic region predominantly wind and winter-cold are limiting factors in the south, while summer drought is so in the north. Ecologically significant data on the regional climates can be found in Weinberger 1973, 1974, 1978), Weinberger et al. 1973), Alberdi et al. 1974) and Villagran 1980). We do not know about any investigations about the temperature re- sistance of trees of the temperature rain forests in Chile except for preliminary studies by Ramirez 1965). * We are thankful to Mrs. L. Berckhoffand Mr. A. Delgado for technical help. Vegetatio 52, 35~4 1983). © Dr W. Junk Publishers, The Hague. Printed in The Netherlands. For the Proteaceae a characteristic polarisation of drought resistance in dependance of the distribu- tion of the species was found Weinberger, 1974). The present study aims at clarifying, whether such a polarisation exists as well in relation to cold-resis- tance and to which extent the latter is subject to annual periodicity as is known for evergreen forests of other continents. Material and methods Figure I gives a list of the investigated Proteaceae including specifications of their geographical dis- tribution and the vegetation areas in which they are dominant. Lomatia hirsuta Radal), Lomatia den- rata Avenanillo) and Gevuina avellana Avenallo) have their distribution optimum in the warmer and n deciduous forest biotopes of Nothofagus oliqua, while Embothrium coccineum Notro) and Loma- tiaferruginea Romerillo) have their centre of dis- tribution in the colder and s biotopes of the subant- arctic rainforests Weinberger et al., 1973).  36 The plant material used came from the Botanical Garden of the Universidad Austral de Chile in Val- divia (39 ° 48' s), thus from a temperate climate (Westermeier, 1975). Between May 1977 and No- vember 1978 branches with completely developed leaves from previously marked trees of the same age have been sampled (except for Embothrium, where young new leaves from August have been used as well). The samples were always taken from the n side of the tree at an average height of 2 m. This plant material has been immediately packed in plas- tic bags and transported to the laboratory for inves- tigations on cold-resistance (Steubing, 1965; Kreeb, 1977). The test plants were kept 120 min at various degrees below zero and after this for the same time at -2°-+1 °. Afterwards the branches, which with the cut ends had been put into water, were taken to a cool room and protected against direct radiation. After 8-10 days visible injuries were evaluated in damaged leaf surface (Lange, 1961; Larcher, 1968). According to Levitt (1958) the 'resistance value' represents the temperature which causes an average 50 leaf injury (TL 50). For special ecolog- ical aspects also temperatures are of interest, at which the first injuries are visible (leaf injury 1-5 , TL5) and at which a total loss of the assimilation surface is expected. In addition the water content and osmotic value have also been measured (Larcher, 1954; Walter & Kreeb, 1970). Because of a shortage of refrigerators it was not possible to work with all plant species at the same time. Although the time difference between the sampling of the different Proteaceae and their in- vestigation was small, there were some differences in the corresponding climatic data, which came from the weather station of the U niversidad Austral de Chile in Valdivia. Because this weather station is near to the study area the reported data are repre- sentative. Since the atmospheric conditions of the past weeks are decisive, values for precipitation and air temperature were used, which had been measured 15 days before the analysis of the frost re- sistance of the investigated species. The tempera- ture minimum was determined at a height of 2 m in the weather cabin. Results Figure 1 shows that the investigated Proteaceae degree of sOuthern la(itude F o r meitione n 32 ° I 36 ° 410° 44 ° 48 ° 512° 56 ° I I I A B C Gevuina .v. ..a Mo I i ~ I LomStia dentata (Ret Pay )RBr i 1 ................... ~'1 Lomatia hirsuta Lain 1Diels I I ........................ q I Lomat;a ferruginea (Car)Br 1 i il Ernbot hriurn coecineum Forst [ i i i i i i i if Fig. 1. Geographical distribution of the investigated species and vegetation zones in which they are dominant (according to Skottsberg, 1910; Schmithiasen, 1956; and Weinberger et aL. 1973): A = summer forest of Nothofagus obliqua, B = n Patago- nian rain forest. can be divided in two groups according to the centre of their geographical distribution: deciduous summer forest-, and antarctic rain forest species. The three species of the deciduous summer forests Gevuina avellana (Fig. 2), Lomatia hirsuta (Fig. 3) and Lomatia dentata (Fig. 4) show similar values between -7,5 and -8,0 o C. However the tempera- ture at the TL 50 begin of the injury, TL 5, varies. For Gevuina avellana and Lomatia hirsuta it was ca. -6 ° C. Total injury (TL 90-100) was found at ca. -9 ° C for the three species. At the time of the lowest cold-resistance in late spring Lomatia hirsuta (Fig. 3) was most endangered by frost, the first injuries becoming visible already at 0 ° C. TL 50 was - 1 ° and (TL 90-100) 3 °C. Less frost sensitive during summer were Gevuina avellana TL 5 =-2 °, TL 50 -2,5 ° C) and Lomatia dentata (TL 5 = -2 ° C and TL 50 = -3 o C). The osmotic values of the three mentioned spe- cies were higher in winter than in summer. For Lomatia hirsuta and Lomatia dentata 21 arm was found as maximum value, for the water-rich Ge- vuina 14 atm. The variation between the extreme values was for this species 2,5 atm lower than for the two Lomatia species. For the latter species the de- crease in water content of the leaves during winter was more distinct. Lomatia ferruginea, which penetrates up to the subantarctic zone, differed from the two deciduous summer forest Lomatia species by a higher cold-re-   7 977 978 M J J A S O N D J F M A M J J A S O N ã ~ 20 5 1 2 3 4 u ~- 5- oi -- 6 L. 7 U 8 9 Atm b. Gevuina avellana t , J ', T L 90-100% t I t I I I I I I I I I 15- Q) :3 14- E 13 O 12- C ~ ~O ~ .,.,.~. /O ~. ~ / /~.,~'~ ~ sO 7 I I 1 I I 1 I I I I I I J I i I autu Iwin 'er [ pring. summer lauf'umn I winter [ spr't~g mm -500 -400 ã 300 -200 100 0 d.s. 180 ] -iso -120 ~ Fig. 2. Frost resistance of Gevuina avellana a) precipitation black columns), average of air temperature minimum black circles) and the oscillation of the temperature within 15 days; b) cold resistance according to leaf injury; c) osmotic value and water content.  38 ° c 25 20, ~. 15- 10- 0- -5 1977 1978 Mt J * J r A r S O N D J ~ F~MI AIM I j [ a. iAtsaOaN mm - 500 J I 00 ~ F ~°° ~_i - 200 -100 ~ 0 0 -1 - 2 - 3- C ¢~- 5 ¢1- 6. C7 -7- tJ . 8- -9- Atm 20- 18- i ã I /\ J \ b. / \\ / , / \ Lomatna hirsuta / / \\\ /// ~ /I \ lil / X / ã \ 1/ */ \ ~ A ~'e /f ã \ \/ã % e '\ %J ~z* It 90-100% i i A l I I I I I I I I I I I l I I c.- / ,,, e- --of ' /~----~;~ , / , ..._'--.o .. ./. ,, \.../,. / ',--,- - . .,\__,.. / ~. / -.. .--... - - -%/-., I i I 1 . I I I I I I I I I I I 1 ds. -150 I -130 ~v 110 ¢3 0 Fig. 3.Frost resistance of Lomatia hirsuta a), b) and c) as in Figure 2.
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