Twenty-three years of stand dynamics in an old-growth Chamaecyparis forest in central Japan

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<ul><li><p>ORIGINAL ARTICLE</p><p>Twenty-three years of stand dynamics in an old-growthChamaecyparis forest in central Japan</p><p>Michinari Matsushita Daisuke Hoshino </p><p>Shin-Ichi Yamamoto Naoyuki Nishimura</p><p>Received: 25 June 2012 / Accepted: 26 January 2013 / Published online: 6 March 2013</p><p> The Japanese Forest Society and Springer Japan 2013</p><p>Abstract Structures and dynamics of old-growth conif-</p><p>erous stands are affected by several types of disturbances</p><p>including typhoons. We report the forest dynamics of four</p><p>old-growth Chamaecyparis stands in central Japan that</p><p>differ in the disturbance history of typhoons over a period</p><p>of 23 years. The stem number, basal area and mortality</p><p>were examined. In a predominant stand of C. obtusa (Sieb.</p><p>et Zucc.) Endl., 24 % of the C. obtusa canopy trees died,</p><p>mainly as a result of the severe damage of a strong typhoon</p><p>that caused a single tree-fall gap and the following gap</p><p>enlargements. In this stand, the total basal area decreased to</p><p>76.5 % of the initial value, although the mortality declined</p><p>in recent years. In contrast, the other three stands decreased</p><p>only slightly in the stem numbers (0.05.6 %) and</p><p>increased in the basal areas of C. obtusa canopy trees. It is</p><p>confirmed that the stand-level ingrowths of 300-year-old</p><p>C. obtusa canopy trees could contribute to the increase in</p><p>the stock of each stand. Our results support an idea that the</p><p>dynamics of old-growth Chamaecyparis forests were</p><p>greatly affected by typhoons. The stand structures will be</p><p>gradually changed (with the processes of gap dynamics)</p><p>and C. obtusa will continue to be dominant, potentially</p><p>over hundreds of years.</p><p>Keywords Forest dynamics Gap formation Long-term study Natural disturbance Stem growth</p><p>Introduction</p><p>Stand structures and dynamics are often affected by several</p><p>types of disturbances (e.g., typhoons) that vary in intensity</p><p>and frequency (Yamamoto et al. 2011; Torimaru et al.</p><p>2012). In many old-growth coniferous forests in East Asia,</p><p>gap creation by typhoons is one of the major disturbance</p><p>regimes (e.g., Asai et al. 2003). Because such disturbances</p><p>occur infrequently and stochastically (Yamamoto et al.</p><p>2011; Torimaru et al. 2012), their effects on dynamics of</p><p>old-growth forests are often complex (Parish and Antos</p><p>2004), and therefore long-term monitoring studies are</p><p>important.</p><p>The genus Chamaecyparis is distributed around the</p><p>Pacific basin and along the eastern coast of North America</p><p>(Farjon 2005). Most Chamaecyparis species are known as</p><p>long-lived with slow growth rates. For example, the max-</p><p>imum age of C. formosensis, a species in Taiwan, exceeds</p><p>ca. 3,000 years old (Zobel 1998). In North America,</p><p>C. nootkatensis is a very long-lived stress tolerator found in</p><p>a wide variety of habitats, which appears to need some</p><p>opening of the stand to reach the canopy (Antos and Zobel</p><p>1986; Antos et al. 2005; Parish and Antos 2006). Because</p><p>Nomenclature: Ohwi and Kitagawa (1992).</p><p>M. Matsushita (&amp;)Laboratory of Forest Sciences, Department of Biological</p><p>Environment, Akita Prefectural University, Akita 010-0195,</p><p>Japan</p><p>e-mail:</p><p>D. Hoshino</p><p>Tohoku Research Center, Forestry and Forest Products Research</p><p>Institute, 92-25, Morioka, Iwate 020-0123, Japan</p><p>S.-I. Yamamoto</p><p>Laboratory of Forest Plant Ecology, Graduate School</p><p>of Bioagricultural Sciences, Nagoya University, Chikusa,</p><p>Nagoya 464-8601, Japan</p><p>N. Nishimura</p><p>Environmental Sciences Laboratory, Faculty of Social</p><p>and Information Studies, Gunma University, 4-2 Aramaki,</p><p>Maebashi, Gunma 371-8510, Japan</p><p>123</p><p>J For Res (2014) 19:134142</p><p>DOI 10.1007/s10310-013-0398-x</p></li><li><p>of their longevities and slow growth, the regeneration</p><p>processes of Chamaecyparis species have not fully been</p><p>understood.</p><p>Two Chamaecyparis species, C. obtusa (Sieb. et Zucc.)</p><p>Endl. and C. pisifera (Sieb. et Zucc.) Endl. are indigenous</p><p>to Japan. The rates of exploitation of Chamaecyparis have</p><p>been very high in the past, since the lumber of Chamae-</p><p>cyparis spp., especially C. obtusa, has been used prefer-</p><p>entially to build feudal architectures (e.g., castles) because</p><p>of its excellent quality (Nishioka and Obara 1975; Ito</p><p>2000). According to IUCN 2010, C. obtusa is classified as</p><p>Near Threatened, and the remaining natural C. obtusa</p><p>forests are small and fragmented (Maeda 1951; Maeda and</p><p>Yoshioka 1952; Matsumoto et al. 2010). Therefore, their</p><p>conservation has been an important and urgent issue</p><p>(Yamamoto 1998; Tsumura et al. 2007). Currently, Kiso</p><p>district in central Japan is the core habitat over the entire</p><p>geographical distribution of natural C. obtusa populations</p><p>(Matsumoto et al. 2010); old-growth Chamaecyparis for-</p><p>ests are rare and thus very precious because of both</p><p>their ecological and commercial value (Yokouchi 1970;</p><p>Yamamoto 1998).</p><p>Akaswa Forest Reserve in the Kiso district is an excel-</p><p>lent representative of Chamaecyparis forests, characterized</p><p>by the pronounced dominance of C. obtusa (Nagano</p><p>Regional Forest Office 1985; Yamamoto 1993a; Hoshino</p><p>et al. 2001). Most Chamaecyparis canopy trees reach</p><p>around 300 years old (Hoshino et al. 2001; Asai et al.</p><p>2003). To understand the current condition and long-term</p><p>trends in Chamaecyparis forests, we began to examine the</p><p>dynamics of typical old-growth stands in this Reserve in</p><p>1985. In this paper, we report the dynamics of old-growth</p><p>C. obtusa stands over 23 years: i.e., the changes in the stem</p><p>number, basal area and mortality patterns. Since little</p><p>information is available on old-growth Chamaecyparis</p><p>forests, our report provides useful information about Cha-</p><p>maecyparis regeneration.</p><p>Here, specific questions were: (1) are the number and</p><p>basal area of C. obtusa canopy trees decreasing or</p><p>increasing; (2) how much are C. obtusa trees growing in</p><p>diameter; and (3) what, if any, are the mortality patterns of</p><p>C. obtusa trees? We summarized the structure and</p><p>dynamics of each stand focusing on the role of typhoon</p><p>disturbances, and then discussed long-term trends and</p><p>future states of old-growth Chamaecyparis forests.</p><p>Materials and methods</p><p>Study area</p><p>The Akasawa Forest Reserve (354305700N, 1373705000E;1,046 ha; 1,0801,558 m a.s.l.) is located in the Kiso</p><p>district of Nagano Prefecture, central Honshu, Japan</p><p>(Nagano Regional Forest Office 1985). Annual precipita-</p><p>tion is ca. 2,500 mm and snow accumulation is 50100 cm.</p><p>The mean annual temperature is 7.8 C at 1,113 m a.s.l.;the mean monthly maximum and minimum temperatures</p><p>are 14.3 C in August and -11.8 C in February, respec-tively. The reserve is on an elevated peneplain with a</p><p>gentle slope. The geology is dominated by acidic igneous</p><p>rocks, including granite, granite porphyry and rhyolite.</p><p>Soils are mainly dry or wet podzols, although brown forest</p><p>soils appear on hillsides or along streams (Nagano Regio-</p><p>nal Forest Office 1985; Yamamoto 1993a).</p><p>Old-growth Chamaecyparis stands in this Reserve, like</p><p>the other stands in the Kiso and neighboring districts, have</p><p>become established after heavy cutting during 16881703</p><p>(Nagano Regional Forest Office 1985). Since that time, most</p><p>stands have been protected from heavy cutting, but selection</p><p>cutting mainly for hardwoods has been undertaken.</p><p>In the reserve, C. obtusa mainly dominates the over-</p><p>story, and C. pisifera frequently co-dominates on the lower</p><p>slopes or along the streams (Nagano Regional Forest Office</p><p>1985; Hoshino et al. 2001). Other coniferous trees like</p><p>Thujopsis dolabrata (L.f.) Sieb. et Zucc. and Thuja</p><p>standishii (Gordon) Carrie`re, and some hardwood trees</p><p>such as Magnolia obovata Thunb. and Quercus mongolica</p><p>Fisch. ex Ledeb. var. grosseserrata (Blume) Rehder et</p><p>E.H.Wilson, occasionally co-occur. The understory layer in</p><p>this Reserve is characterized by dense cover of the saplings</p><p>of T. dolabrata, occasionally with small trees of some</p><p>broadleaved species (Yamamoto and Suto 1994; Hoshino</p><p>et al. 2001, 2003; Matsushita et al. 2010). T. dolabrata is a</p><p>highly shade-tolerant species which can reproduce by</p><p>layering under closed canopy conditions (Yamamoto and</p><p>Suto 1994); meanwhile, the seedlings of C. obtusa estab-</p><p>lished on exposed mineral soil beneath tree-fall gaps</p><p>(Yamamoto 1988, 1993b), and there are no or very few</p><p>saplings of C. obtusa (Yamamoto and Suto 1994; Hoshino</p><p>et al. 2001, 2003).</p><p>Study plot and field methods</p><p>Four representative old-growth stands were chosen for this</p><p>study (Table 1). The canopy of Stand O consisted of only</p><p>C. obtusa, whereas Stands S and H had a few other species</p><p>in the canopy but were dominated by C. obtusa. However,</p><p>several species co-existed in the canopy of Stand K. While</p><p>there were no records of selection cutting in Stand H,</p><p>Stands O, S and K underwent selection cutting during the</p><p>period 19151947, mainly to remove dead canopy trees</p><p>(Nagano Regional Forest Office 1985). When C. obtusa</p><p>trees have died naturally (e.g., as the result of typhoons),</p><p>the dead trees have been (but not frequently) removed from</p><p>the reserve by forest managers.</p><p>J For Res (2014) 19:134142 135</p><p>123</p></li><li><p>There is no evidence of forest fires, but typhoons are a</p><p>major natural disturbance. The Isewan typhoon in 1959</p><p>caused severe damage to several stands in the reserve</p><p>(Nagano Regional Forest Office 1985), and, especially,</p><p>Stand K was severely damaged by the typhoon (Yamamoto</p><p>1993a). Stand O was affected by another strong typhoon in</p><p>1991. At these times, dead trees were removed from these</p><p>stands, and stumps were left.</p><p>In SeptemberOctober 1985, a 0.2-ha plot (40 9 50 m)</p><p>was laid out in a representative location within each forest</p><p>stand. In each plot, canopy trees [stem diameter at breast</p><p>height (DBH) C20 cm] were tagged, and their species</p><p>name, living status, location, and DBH were recorded.</p><p>Re-censuses were conducted from then until 2008 at ca.</p><p>5-year intervals (specific census years are shown in</p><p>Table 2). The condition of dead trees was classified as</p><p>standing dead, uprooted, stem broken or stump.</p><p>Data analysis</p><p>The annual rate of stem mortality was calculated as:</p><p>100 lnNi lnNs =T ;where Ni is the initial number of living stems and Ns is the</p><p>number of the surviving stems at each subsequent census,</p><p>and T is the time interval (years) between the censuses.</p><p>Basal area (BA) of each stem ([20 cm DBH) was cal-culated as: p 9 (DBH/2)2. Then, the stand-level BA wasdefined as the sum of the BAs of all stems ([20 cm DBH)within each plot. As an index of ingrowth, the increment in</p><p>the stand BA of surviving trees (excluding recruited trees)</p><p>was defined as follows:</p><p>Growth of stand BA ln BAf ln BAi =T;where BAf and BAi are the stand BAs at the final and initial</p><p>census, respectively, and T is the time interval (years)</p><p>between the final and initial censuses.</p><p>As an index of the growth of each individual stem, the</p><p>increment in the DBH of surviving trees was defined as the</p><p>absolute growth rate (AGR), as follows:</p><p>AGR DBHf DBHi =T;where DBHf and DBHi are the DBHs of each stem at the</p><p>final and initial census, respectively, and T is the time</p><p>interval (years) between the final and initial censuses.</p><p>The 95 % confidence intervals for these parameters</p><p>(mortality, growth of stand BA, and AGR), were estimated</p><p>by the standard bootstrapping method, with the populations</p><p>resampled 1,000 times from the original data. We used the</p><p>bias-corrected percentile method to determine confidence</p><p>intervals (Manly 2007). Statistical analyses were performed,</p><p>by using R 2.8.2 (R Development Core Team 2008).</p><p>Results</p><p>Changes in the stem density and mortality</p><p>Over the 23-year study period, the numbers of coniferous</p><p>canopy trees decreased from 75 to 57 in Stand O, from 67</p><p>to 65 in Stand S, and from 85 to 76 in Stand H, but</p><p>increased from 85 to 96 in Stand K (Table 2). When tar-</p><p>geting only C. obtusa, whereas there was a slight increase</p><p>in the number from 15 to 16 in Stand K, the numbers</p><p>decreased in the other three stands.</p><p>The mortality rate of canopy trees was highest in Stand</p><p>O, whereas it was very low in Stands S and K (Fig. 1). In</p><p>Stand O, the mortality rate of C. obtusa canopy trees was</p><p>higher in the periods 19901998 and 19982003, and then</p><p>decreased in the period 20032008 (Table 2). During the</p><p>23 years, stem recruitment events were observed only for</p><p>Stand K, where 1 C. obtusa tree and 12 hardwood trees</p><p>(mainly of M. obovata) were recruited, while there was no</p><p>recruitment stems in Stands O, S and H.</p><p>Table 1 Attributes of the four old-growth Chamaecyparis stands in the Akasawa Forest Reserve</p><p>Stand H Stand S Stand O Stand K</p><p>Topographic position Middle slope Middle slope Upper slope Lower slope</p><p>Slope direction E SW NW SW</p><p>Slope inclination () 05 05 05 510Stand height (m) 3334 35 3536 2526</p><p>Dominant canopy tree</p><p>species</p><p>Chamaecyparis obtusa, Thujopsis</p><p>dolabrata, Magnolia obovata</p><p>C. obtusa, Thujopsis</p><p>dolabrata</p><p>C. obtusa C. obtusa, C. pisifera;</p><p>hardwood trees</p><p>Dominant understory</p><p>species</p><p>Thujopsis dolabrata T. dolabrata Deciduous broad-</p><p>leaved shrubs</p><p>C. pisifera</p><p>History of major</p><p>disturbance</p><p>None Selection cutting</p><p>during 19151947</p><p>Selection cutting</p><p>during 19151947</p><p>Strong typhoon in</p><p>1991</p><p>Selection cutting during</p><p>19151947</p><p>Isewan typhoon in 1957</p><p>136 J For Res (2014) 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2.1</p><p>0(0</p><p>.00</p><p>7</p><p>.13</p><p>)</p><p>1.4</p><p>1.4</p><p>(0.0</p><p>)1</p><p>.3(0</p><p>.1)</p><p>1.2</p><p>(0.1</p><p>)1</p><p>.1(0</p><p>.1)</p><p>Oth</p><p>ers</p><p>11</p><p>10</p><p>00</p><p>.10</p><p>.10</p><p>.10</p><p>.10</p><p>.0</p><p>To</p><p>tal</p><p>85</p><p>83</p><p>0.4</p><p>8(0</p><p>.00</p><p>1</p><p>.21</p><p>)</p><p>79</p><p>0.4</p><p>9(0</p><p>.12</p><p>1</p><p>.01</p><p>)</p><p>77</p><p>0.4</p><p>9(0</p><p>.85</p><p>2</p><p>.18</p><p>)</p><p>76</p><p>0.2</p><p>6(0</p><p>.00</p><p>0</p><p>.80</p><p>)</p><p>17</p><p>.21</p><p>7.3</p><p>(0.1</p><p>)1</p><p>7.3</p><p>(0.5</p><p>)1</p><p>7.2</p><p>(0.2</p><p>)1</p><p>7.6</p><p>(0.1</p><p>)</p><p>Sta</p><p>nd</p><p>K</p><p>Ch</p><p>am</p><p>aec</p><p>ypa</p><p>ris</p><p>ob</p><p>tusa</p><p>15</p><p>15</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>16</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>16</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>16</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>1.7</p><p>1.7</p><p>(0.0</p><p>)1</p><p>.9(0</p><p>.0)</p><p>2.0</p><p>(0.0</p><p>)2</p><p>.1(0</p><p>.0)</p><p>Ch</p><p>am</p><p>aec</p><p>ypa</p><p>ris</p><p>pis</p><p>ifer</p><p>a3</p><p>33</p><p>3</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>33</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>33</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>32</p><p>0.6</p><p>2(0</p><p>.00</p><p>1</p><p>.90</p><p>)</p><p>4.1</p><p>4.3</p><p>(0.0</p><p>)4</p><p>.6(0</p><p>.0)</p><p>4.7</p><p>(0.0</p><p>)4</p><p>.8(0</p><p>.1)</p><p>Oth</p><p>ers</p><p>37</p><p>42</p><p>49</p><p>48</p><p>48</p><p>1.8</p><p>2.4</p><p>2.9</p><p>3.1</p><p>3.5</p><p>To</p><p>tal</p><p>85</p><p>90</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>98</p><p>0.0</p><p>0(n</p><p>ot</p><p>test</p><p>ed)</p><p>97</p><p>0.2</p><p>1(0</p><p>.00</p><p>0</p><p>.62</p><p>)</p><p>96</p><p>0.4</p><p>2(0</p><p>.00</p><p>1</p><p>.06</p><p>)</p><p>7.6</p><p>8.4</p><p>(0.0</p><p>)9</p><p>.4(0</p><p>.0)</p><p>9.8</p><p>(0.0</p><p>)1</p><p>0.4</p><p>(0.1</p><p>)</p><p>Fo</p><p>rth</p><p>en</p><p>um</p><p>ber</p><p>of</p><p