BIOTROPICA 45(5): 541–548 2013 10.1111/btp.12048

Litterfall and Element Fluxes in a Natural Hardwood Forest and a Chinese-fir Plantation Experiencing Frequent Typhoon Disturbance in Central

Hsueh-Ching Wang1,2, Su-Fen Wang2, Kuo-Chuan Lin3, Pei-Jen Lee Shaner4, and Teng-Chiu Lin4,5 1 Department of Geography, National Taiwan University, , 10617 Taiwan 2 Department of Geography, National Changhua University of Education, Changhua, 50007 Taiwan 3 Taiwan Forestry Research Institute, Taipei, 10066 Taiwan 4 Department of Life Science, National Taiwan Normal University, Taipei, 11677 Taiwan

ABSTRACT Chinese fir(Cunninghamia lanceolata) is the most important forest plantation species in subtropical Asia and is rapidly replacing natural forests. Such land-use change may affect ecosystem nutrient cycling through changes in litterfall nutrient flux. Tropical cyclones often cause pulses of litterfall. Previous studies, however, have mostly focused on the effects of a single cyclone with little effort examining the effects of repeated cyclones. We examined litterfall in a natural hardwood forest and a Chinese-fir plantation in central Taiwan expe- riencing an average of one typhoon per year. The natural hardwood forest had 54 percent higher annual litterfall (11,400 kg/ha/yr) than the Chinese-fir plantation (7400 kg/ha/yr). Four typhoon-affected months (typhoon period) contributed to approximately 60 percent of the litterfall and litterfall element flux in the natural hardwood forest and 80 percent in the Chinese-fir plantation, with contributions from individual typhoons varied by more than twofold. Litterfall N and P concentrations were significantly higher in typhoon period than in non-typhoon period, likely the result of limited retranslocation. was a better predictor of quantity of typhoon-asso- ciated litterfall than wind velocity. Both types of forests in southeastern beyond the reach of typhoons have litterfall peaks in the dry season. In contrast, we measured higher litterfall during the typhoon period than during the dry season, suggesting that in regions with frequent cyclones, cyclones drive temporal variation of litterfall. Global climate change is affecting the frequency and intensity of cyclones; therefore, knowledge of typhoon-litterfall dynamics is indispensable for understanding the effects of climate change on ecosys- tem nutrient cycling.

Abstract in Chinese is available in the online version of this article.

Key words: Chinese fir plantation; land use; litterfall; retranslocation; typhoon disturbance.

LITTERFALL IS AN IMPORTANT COMPONENT OF NUTRIENT CYCLING IN replacement of natural forests by forest plantations, on nutrient FOREST ECOSYSTEMS (Brinson et al. 1980, Vitousek 1984, Aber & and carbon cycling is still unclear. Melillo 2001). Nutrient return from litterfall has been shown to Disturbances can greatly affect patterns of litterfall. Tropical be positively correlated with ecosystem productivity (Bray & cyclones (a generic term that has different names in different Gorham 1964, Chapin 1980). Numerous studies reported pat- geographic regions including typhoons, hurricanes and tropical terns of litterfall in temperate and tropical regions. Yet, empirical cyclones) often lead to sudden increases in litterfall followed by a data on litterfall patterns remain scarce in the subtropics of mon- period of low litterfall (Lodge et al. 1991, Lin et al. 2003, Beard soon Asia, although this region contains one of the world’s larg- et al. 2005). Studies in Hong Kong and showed that a sin- est areal expanses of forest plantations. For example, 9.1 million gle typhoon event could contribute 20–45 percent of the annual hectares of Chinese-fir(Cunninghamia lanceolata Lamb.) plantations litterfall (Lam & Dudgeon 1985, Xu et al. 2004) and in Taiwan, already existed in southern and southeastern China in early 1990s six typhoons in 1 yr contributed to more than 50 percent of the and is now rapidly replacing natural forests (Ma et al. 2007, Guo annual litterfall (Lin et al. 2003). Unlike naturally senesced leaves et al. 2010). A few studies have compared primary productivity, in which the nutrient concentration is substantially reduced due nutrient cycling (e.g., litterfall and litterfall decomposition) and fine to retranslocation, typhoons deposit a large quantity of green and root dynamics between natural forests and Chinese-fir plantations immature leaves with limited retranslocation, leading to a high (Yang et al. 2004a,b, 2005), but few have taken into account cli- litterfall nutrient flux through forest floor (Lodge et al. 1991). mate conditions and disturbance regimes. Therefore, our under- Forest plantations can be more vulnerable to cyclone distur- standing of the effects of forest land uses, especially the bance than natural forests. The 1989 hurricane Hugo caused greater mortality to a 64-yr mahogany plantation than to a nearby natural forest of similar age in Puerto Rico (Fu et al. 1996). In Received 2 February 2013; revision accepted 1 April 2013. northeastern Taiwan, a Japanese cedar (Cryptomera japonica [L. f.] [This article was corrected after online publication on 17 August 2013. The spelling of author Dr. Su-Fen Wang’s name was corrected.] Don.) plantation had greater reduction in canopy cover than an 5Corresponding author; e-mail: [email protected] adjacent natural hardwood forest following a category 3 typhoon ª 2013 The Association for Tropical Biology and Conservation 541 542 Wang, Wang, Lin, Shaner, and Lin

due to greater defoliation in the C. japonica plantation (Kang et al. ests in central Taiwan’s lowlands. The natural hardwood forests 2005). Both dead trees and fallen leaves contribute to litterfall. were dominated by Fagaceae and Lauraceae tree species, includ- Thus, the effects of tropical cyclones on litterfall dynamics could ing Schefflera taiwaniana (Nakai) Kanehira, Helicia formosana Hemsl., be very different between natural forests and forest plantations, Cinnamomum subavenium Miq., Cryptocarya chinensis (Hance) Hemsl., but it was rarely examined. Engelhardtia roxburghiana Wall., Cyclobalanopsis pachyloma (O. Seem.) Although litterfall dynamics driven by natural disturbances Schott., and Meliosma squamulata Hance. The majority of the are well documented, most studies have focused on the effect of remaining area in the experimental forest (192 out of 200 ha) is a single disturbance event. The intensity, duration, and timing of covered by conifer plantations. For the purpose of our study, the disturbance events can all affect ecosystem responses and feed- comparisons between the two forest types are only valid if they backs (Turner 2010) so that the results from a particular distur- have similar climate and disturbance regimes. Due to this con- bance event may not reflect the overall system responses to the straint, it is not possible to replicate at site level. Therefore, we type of disturbance. The lack of empirical studies on distur- focused the comparisons at the plot level. bance–ecosystem interactions driven by repeated disturbance The mean annual precipitation is 2200 mm and mean annual events is partly attributed to the unpredictability of most natural temperature is 20.8°C (lowest in January at 14.9°C and highest in disturbances (e.g., tropical cyclones and forest fires) in space and July at 25.4°C, 1961–2007). During our study period from May time. Therefore, a region with a high frequency of disturbance 2008 to April 2009, the annual precipitation was 3835 mm, and events (i.e., annual typhoons) might present great opportunities to mean annual temperature was 19.4°C (lowest in January at provide the much-needed empirical data. 13.2°C and highest in August at 23°C) (Fig. S2). There was a dry In this study, we examined patterns of litterfall in a Chinese- season between October and February with mean precipitation of fir plantation and an adjacent natural hardwood forest in Lienhu- 230 mm or approximately 10 percent of the annual precipitation achi Experimental Forest of central Taiwan (Table 1). The (Hsiao et al. 2007). experimental forest, on average, experienced 0.9 typhoon annually Litterfall patterns were examined at two paired (side-by- between 1994 and 2010 with as many as four typhoons in a year side) forest watersheds, an 8.4-ha natural hardwood forest, and (2008) (Lee et al. 2008, T. C. Lin unpubl. data) and a maximum a 5.9-ha Chinese-fir plantation. The plantation forest watershed of three consecutive years (1997–1999) without a typhoon. Spe- was originally a natural hardwood forest that was clearcut in the cifically, we tested the following two alternate hypotheses: (1) winter between November 1970 and March 1979 followed by typhoons influence temporal patterns of litterfall and litterfall planting seedlings of Chinese fir in 1981. Chinese-fir is a native nutrient flux; and (2) patterns of litterfall, litterfall element con- conifer widely distributed in southeastern China and Taiwan. centration and flux differ between natural hardwood forests and Between 1982 and 1985, weeds were cut several times a year Chinese-fir plantations. The results have important management and new seedlings planted to replace those that had died. There implications regarding forest nutrient cycling and carbon budgets have been no management activities in the watershed since not only for the study site but also for subtropical Asia where 1986. forest plantations are replacing natural forests. STAND PROPERTIES.—Diameter at breath height (dbh) and stand METHODS density of trees with dbh > 5 cm were measured in seven and four randomly located 20 9 20 m plots in the natural hardwood STUDY SITE.—The study was conducted at the Lienhuachi Experi- forest and Chinese-fir plantation, respectively. Aboveground bio- mental Forest (120o54′E, 23o54′N) in central Taiwan (Fig. S1). mass (ABG) of the two forests was estimated using allometric The Experimental Forest has a total area of 461 ha, of which models. Biomass of Chinese firs was calculated using an empirical 261 ha are covered by the only remaining natural hardwood for- model developed for Chinese fir (Lin et al. 2004). Biomass of natural hardwood trees was calculated using the Moist Model Without Height developed by Chave et al. (2004), McEwan et al. TABLE 1. Stand characteristics of the natural hardwood forest and Chinese-fir (2011). plantation at the Lienhuachi Experimental forest (mean Æ standard error). Chinese fir model: ABG = À2.74 + 2.43 9 ln(dbh) fi Natural hardwood Chinese- r Moist model without height: ABG = q 9 exp(À1.239 + forest plantation P-value 1.908 9 ln(dbh) + 0.207 9 (ln(dbh))2 – 0.0282 9 (ln(dbh))3) Stand characteristics where q is wood density (g/cm3) and the values were taken from Area (ha) 8.4 5.9 NA Global Wood Density Database (http://www.worldagroforestry. Age (years) Hundreds 30 NA org/sea/Products/AFDbases/WD/Index.htm). Five of the 49 Slope (%) 10.8 16.9 NA species were not included in the data base and the mean wood Æ Æ Tree density (# trees/ha) 1480 120 1160 55 0.09 density of the remaining species, 0.45 g/cm3, was used. dbh (cm) 15 Æ 0.68 17 Æ 0.83 0.11 Biomass (Mg/ha) 260 Æ 27 107 Æ 7.4 0.01 2 LITTERFALL COLLECTION AND ANALYSIS.—Six 1 m nylon litterfall NA, not available. traps at 1 m height aboveground were installed at random loca- Litterfall and Typhoon Disturbance 543

tions within each of the two forests. Due to the small amount of TABLE 2. Typhoon data for Taiwan in 2008. litterfall insufficient for chemical analysis in the Chinese-fir plantation, one additional trap was installed next to each of the Name Kalmaegi Fungwong Sinlkau Jangmi existing traps. Litterfall samples from the two neighboring traps * – – – – were mixed after collection. Litterfall was collected monthly from Period 07/16 18 07/26 29 09/11 16 09/26 29 May 2008 to April 2009. Because the second typhoon Fungwong Direction (degree) 270 200 270 200 occurred at the end of July (26–29), the typhoon-induced litterfall Maximum wind velocity 33 43 51 53 fi (m/s) was collected in the following week, the rst week of August. † Mean wind velocity (m/s) 26 19 32 29 Similarly, the fourth typhoon (Jangmi) occurred in the last week † of September (26–29) so the litterfall was collected in the first Precipitation (mm) 580 210 860 440 week of October. As a result, litterfall of each of the 4 mo (July– *Period of each typhoon was defined by the first and last dates of typhoon October) included litterfall induced by one typhoon. The 4 mo warnings issued by the Central Weather Bureau of Taiwan. are referred as the typhoon period and the remaining 8 mo are †Data from Sun-Moon Lake Weather Station 7 km southeast of the Lienhu- referred as non-typhoon period hereafter. achi Experimental Forest. Litterfall was separated into leaves and branches for hard- wood tree species, but, for Chinese fir, the ‘leaves’ also included TYPHOON INFORMATION.—Four typhoons made landfall in Taiwan the small branchlets to which they were attached. Litter from between July and September 2008: Kalmaegi, Fungwong, Sinlkau, non-planted hardwood tree species that have invaded the Chi- and Jangmi (Table 2), bringing a total of 2,090 mm of rainfall nese-fir plantation was categorized as ‘other’. The collected litter- (54% of the 3,840 mm annual rainfall) and each reaching a maxi- fall was air dried for 2 days and then oven-dried at 60°C for mum wind velocity greater than 33 m/s. Sinlaku occurred 48 hr. The dried litterfall was ground using a grinder machine between 11 and 16 September and had the highest mean wind (GRINDER DJ4S Yuantaichi, Taipei, Taiwan) for chemical analy- velocity (32 m/s) and precipitation (860 mm) among the four ses of C, N, P, K, Ca and Mg. The contents of C and N in litter- typhoons. Fungwong occurred between 26 and 29 July and had fall were analyzed using CHNS-Elemental Analyzer, while P, K, the lowest mean wind velocity (19 m/s) and precipitation Ca, Mg were analyzed with ICP-AES. We split each litterfall sam- (210 mm) (Table 2). ple into two subsamples. Samples were re-analyzed if the differ- ence between the two subsamples was more than 5 percent. Data TEMPORAL PATTERNS OF LITTERFALL.—Temporal patterns of litter- from four of the 144 samples were excluded from statistical anal- fall can be divided into one high period (July–October) and two yses because the differences between their subsamples remained low periods (May–June preceding the high period and November more than 5 percent even after the re-analysis. One of the four to the next April following the high period; Fig. 1). The typhoons samples was from one trap in the natural hardwood forest in Jan- were correlated with greater fluctuations of monthly litterfall in uary 2009 and the other three were from the Chinese-fir planta- the Chinese-fir plantation (90–2000 kg/ha/mo) than in the natu- tion in October 2008, January and February 2009 (two different ral hardwood forest (280–2010 kg/ha/mo; Fig. 1). Monthly litter- traps). fall was significantly and consistently higher in the natural hardwood forest than in the Chinese-fir plantation (paired t-test DATA ANALYSIS.—One-way ANOVA was used to compare stand t = 5.49, P < 0.001). Annual litterfall of the natural hardwood characteristics between the natural hardwood forest and the Chi- forest, 11,400 kg/ha/yr, was 54 percent higher than that of the nese-fir plantation, as well as litterfall element concentrations Chinese-fir plantation, 7400 ka/ha/yr. The typhoon period con- between typhoon period and non-typhoon period (April–June tributed 59 percent (6630 kg/ha) of the annual litterfall in the 2008 and November–December 2009). Paired t-tests were used natural hardwood forest and 81 percent (6000 kg/ha) in the Chi- to compare monthly quantities, element concentrations, and ele- nese-fir plantation, indicating that typhoons largely increased lit- ment fluxes of litterfall between the natural hardwood forest and terfall in both forests and even more so in the Chinese-fir Chinese-fir plantation. Pearson’s simple correlation was used to plantation. examine the relationship between monthly precipitation and Although it is not possible to separate the influences of wind monthly litterfall quantity. and rain on typhoon-induced litterfall, total precipitation during a typhoon period seems to be a better predictor of litterfall quan- RESULTS tity than maximum wind velocity. Monthly litterfall in the four typhoon-affected months was more closely related to typhoon STAND PROPERTIES.—The natural hardwood forest had signifi- precipitation (r = 0.85, P = 0.008, N = 8, natural forest and cantly higher tree density (1480 Æ 120 tree/ha) at a = 0.10 and plantation combined) than maximum wind velocity (r = À0.31, biomass (260 Æ 27 kg/ha) at a = 0.05 than Chinese-fir plantation P = 0.46, N = 8). (stand density 1160 Æ 55 tree/ha, biomass 107 Æ 7.4 kg/ha), The proportion of branches in total litterfall was higher in although dbh was not significantly different between the the natural hardwood forest (27%) than in the Chinese-fir planta- hardwood forest 15 Æ 0.68 cm, and the Chinese-fir plantation tion (15%), but this may be an artifact of not separating branch- 17 Æ 0.83 cm (P = 0.11). lets from leaves in the Chinese fir. On a monthly basis, the 544 Wang, Wang, Lin, Shaner, and Lin

A cantly higher, and concentration of C was significantly lower in the natural hardwood forest than in the Chinese-fir plantation (paired t-test, all t > 3.42, P < 0.01). There were no differences between the two forests in P concentration (paired t-test t = À0.71, P = 0.50; Fig. 2). Monthly element concentrations of leaf litter did not fluctu- ate as much as monthly litterfall (Fig. 2). Notably, concentrations of N and P were significantly higher during the typhoon period than during the non-typhoon period in the natural hardwood for- est (Table 3). Concentration of Ca and C:N ratio were, on the other hand, lower during the typhoon period than during the non-typhoon period in the natural hardwood forest (Table 3). In the Chinese-fir plantation, only K showed a significant difference between the two periods with higher concentration in the typhoon period (Table 3). B Patterns of monthly litterfall nutrient fluxes were similar to the patterns of monthly litterfall quantities in both forests, with the typhoon period having much greater litterfall nutrient fluxes than the non-typhoon period (Fig. 3). The typhoon period con- tributed 54–61 percent of the annual total litterfall nutrient flux in the natural hardwood forest and 76–84 percent in the Chi- nese-fir plantation, which is comparable to their contributions to litterfall quantities, 59 percent and 81 percent in the natural hard- wood forest and the Chinese-fir plantation forest, respectively. The natural hardwood forest had consistently higher monthly nutrient fluxes than the Chinese-fir plantation for all nutrients (paired t-test, all t > 3.02, P < 0.05; Fig. 3). The higher fluxes of N, K, Ca and Mg in the natural hardwood forest resulted from the higher litter element concentrations (Fig. 2) and litterfall quantities (Fig. 1). The higher C flux in the natural hard- FIGURE 1. Monthly litterfall from natural hardwood forest (A) and Chinese- wood forest, however, resulted solely from the higher litter quan- fir plantation (B) at the Lienhuachi Experimental Forest from May 2008 to tity (Fig. 1) because carbon concentration was actually lower in April 2009. Each arrow indicates the approximate time of the occurrence of a the natural hardwood forest than in the Chinese-fir plantation typhoon event. (Fig. 2). DISCUSSION contribution of branches to litterfall was much higher in the TYPHOONS AND VARIATION IN LITTERFALL.—In regions without typhoon period (640 kg/ha/mo, 40%) than in the non-typhoon annual disturbances, the seasonal pattern of litterfall is closely period (57 kg/ha/mo, 10%). Although leaf litter contributed the linked to tree phenology and often peaks during the dry season highest proportion to the annual litterfall in both forests, in the when drought-induced senescence leads to large quantity of litter- first typhoon-affected month (July), the contribution of branches fall (Stocker et al. 1995, Wood et al. 2005, Pandey et al. 2007). (1290 kg/ha) to total litterfall (2280 kg/ha) was greater than that For example, a study in the southeastern China beyond the reach of leaf litter (980 kg/ha) in the natural hardwood forest. In the of typhoons documented that annual peaks of litterfall typically Chinese-fir plantation, although the quantity of branches was also occurred in the dry season between March and May in a natural higher during the typhoon period, leaf litter always had a higher hardwood forest and no major peaks in a Chinese-fir plantation contribution than non-leaf litter (Fig. 1). The monthly litterfall of (Yang et al. 2004a). Several studies of litterfall of Chinese-fir plan- hardwood species in the Chinese-fir plantation varied consider- tations in southern and southeastern China, also beyond the ably (41–215 kg/ha/mo), but was generally higher in the typhoon reach of typhoons, reported that litterfall peaked in the dry sea- period (with a mean of 160 kg/ha/mo or 11% between July and son between November and May (Ma et al. 2002, Wang et al. October) than in the non-typhoon period (with a mean of 2008). 63 kg/ha/mo but 37% in the non-typhoon period; Fig. 1). The dry season at Lienhuachi occurs between October and February with rainfall less than 10 percent of the annual total. LITTERFALL NUTRIENT CONCENTRATION AND NUTRIENT RETURN.— The greater amount of litterfall during the typhoon period than Concentrations of N, K, Ca and Mg of leaf litter were signifi- during the dry season, however, suggests that typhoon distur- Litterfall and Typhoon Disturbance 545

FIGURE 2. Monthly element concentrations of leaf litter of the natural hardwood forest and Chinese-fir plantation at the Lienhuachi Experimental Forest from May 2008 to April 2009. The shaded areas indicate the periods affected by typhoons. Monthly element concentrations were significantly different between the two forests for all elements (paired t-test, all t > 3.42, P < 0.05) except P (paired t-test t = À0.71, P = 0.50).

TABLE 3. Leaf litter element concentrations (mean Æ standard error, mg/g). The typhoon period includes July–October 2008 and the non-typhoon period, May–June and November– December 2008 and January–April 2009.

Natural hardwood forest Chinese-fir plantation

Element Typhoon Non-typhoonP-value Typhoon Non-typhoon P-value

C 520 Æ 1.3 520 Æ 1.1 0.41 540 Æ 2.6 530 Æ 3.9 0.35 N20Æ 0.40 16 Æ 0.27 < 0.001 13 Æ 0.41 13 Æ 0.42 0.62 C:N 26 Æ 0.50 32 Æ 0.53 < 0.001 42 Æ 1.2 43 Æ 1.9 0.92 P 0.83 Æ 0.028 0.58 Æ 0.018 < 0.001 0.73 Æ 0.016 0.67 Æ 0.026 0.16 K 5.0 Æ 0.23 5.1 Æ 0.46 0.84 3.3 Æ 0.24 2.0 Æ 0.27 0.011 Ca 5.9 Æ 0.25 6.6 Æ 0.067 0.007 4.7 Æ 0.075 5.3 Æ 0.21 0.12 Mg 2.2 Æ 0.095 2.3 Æ 0.046 0.34 1.9 Æ 0.08 1.8 Æ 0.057 0.21 bances had a much greater influence on litterfall than phenologi- The large contributions of typhoons to litterfall nutrient flux cal effects. A 2009 study of litterfall in evergreen hardwood for- (approximately 60% in the natural hardwood forest and 80 ests along an elevational gradient in central Taiwan including percent in the Chinese-fir plantation) suggest that typhoon Lienhuachi also found that the only litterfall peak was in August disturbance plays an important role in nutrient cycling through during typhoon Morakot (Lu & Liu 2012), further supporting the generation of litterfall pulses. Although the effects of tropical our conclusion that typhoons could drive litterfall dynamics in cyclones on forest structures and regeneration have been inten- forest ecosystems experiencing frequent disturbances. sively studied in various regions (Brokaw & Walker 1991, Yih 546 Wang, Wang, Lin, Shaner, and Lin

FIGURE 3. Monthly litterfall element fluxes of the natural hardwood forest and Chinese-fir plantation at the Lienhuachi Experimental Forest from May 2008 to April 2009. The shaded areas indicate the periods affected by typhoons. Monthly element fluxes are significantly higher in the hardwood forest than in the Chi- nese-fir plantation for all elements (paired t-test, all t > 3.02, P < 0.05). et al. 1991, Mabry et al. 1998, Saito 2002, Boutet & Weishampel developed and vulnerable to abscission, resulting in high litterfall. 2003), few studies have examined their effects on nutrient cycling. Following that loss of leaves, new leaves were produced to The higher N and P contents in typhoon period in the natural replace the lost leaves, but these new leaves were not advanced hardwood forest most likely resulted from the lower retransloca- enough to be shed in litterfall during the second typhoon. They tion rates in typhoon-induced litterfall as retranslocation is an were fully expanded by the third typhoon, however, and so the adaptation to predictable phenology, but not unpredictable distur- pattern of high and low litterfall was repeated in the third and bances. Increased nitrate concentrations in stream water caused fourth typhoons. by high flows during and following typhoons/hurricanes have The effects of a on ecosystems are closely been reported in Puerto Rico and Taiwan, and were attributed to related to the intensity of the cyclone, which is conventionally increased leaching from soil and litterfall (McDowell 2001, Lin defined by the wind velocity (Scatena & Larsen 1991, Whigham et al. 2011). The lower retranslocation rates of N and P during et al. 1991, Saito 2002, Van Bloem et al. 2005). Our study indi- typhoon periods, which typically have high litterfall and high pre- cates that there is a need to include precipitation into studies of cipitation may lead to the leaching loss of these two most com- cyclone effects on ecosystems. Although each of the four mon limiting nutrients. The long-term effects of such nutrient typhoons brought a pulse of litterfall, the quantity differed by loss on ecosystem nutrient budgets and primary productivity more than twofold (minimum = 990 kg/ha/mo, maximum = should be explored further. 2,010 kg/ha/mo). Thus, our study highlights the importance of Although high winds are expected to cause physical damages tracking repeated cyclones in improving our overall understanding to trees and thus increase litterfall quantities, our study indicates of cyclone effects. that wind velocity is not a good predictor of litterfall increases during typhoons. The momentum of the intense rainfall probably COMPARISON OF FOREST TYPES.—The higher litterfall quantity in plays a more important role in promoting litterfall. In addition, the natural hardwood forest than in the Chinese-fir plantation the timing of the typhoon may be important. One explanation partly reflects their differences in biomass which is to a large for our findings of differences in litterfall among typhoons is the degree related to their difference in age. A study of litterfall and following: At the time of the first typhoon, leaves were fully litterfall nutrient flux in Chinese-fir plantations of different ages Litterfall and Typhoon Disturbance 547

in southeastern China indicates that annual litterfall increased experimental analyses and Dr. Jyhmin Chinag for comments on from 110 kg/ha/yr in an 8-yr stand to 3 l0 kg/ha/yr in a 12-yr the earlier versions of the manuscript. stand and 420 kg/ha/yr in a 24-yr stand. Although our 26-yr Chinese-fir plantation is generally considered mature, it is still SUPPORTING INFORMATION much younger than the natural hardwood forest (> 100 yr). Not surprisingly, we found that the biomass was 2.4 times and annual Additional Supporting Information may be found in the online litterfall was 1.5 times higher in the natural hardwood forest than version of this article: in the Chinese-fir plantation. The proportionally higher litterfall (81% of annual total) from the typhoon period in the Chinese-fir FIGURE S1. Location of Lienhuachi (LHC) Experimental For- plantation than in the natural hardwood forest (59%), however, est in central Taiwan. suggests that typhoon disturbance had a greater influence on lit- FIGURE S2. Rainfall (mm) and temperature (C) between terfall in the Chinese-fir plantation than in the natural hardwood May 2008 and April 2009 from Sun-Moon Lake Weather Station, forest. Yet, it is not clear how the age difference between the two 7 km southeast of the Lienhuachi Experimental Forest. forests might have contributed to their differences in typhoon- induced litterfall. LITERATURE CITED A study of litter decomposition in a natural hardwood for- est, a secondary hardwood forest and a Chinese-fir plantation ABER,J.D.,AND J. M. MELILLO. 2001. Terrestrial Ecosystems. Harcourt Aca- demic Press, New York, USA. 40 km west of our study site found higher litter decomposition BEARD, K. H., K. A. 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LIN. 2007. tionally used to classify typhoon intensity, it may not be a good Precipitation chemistry at the Lienhuachi experimental forest in central predictor of typhoon effects on important ecosystem processes Taiwan. Taiwan J. For. Sci. 22: 1–13. such as litterfall dynamics; rainfall, on the other hand, may serve KANG, R. L., T. C. LIN,J.F.JAN, AND J. L. HWONG. 2005. Changes in the nor- malized difference vegetation index (NDVI) at the Fushan experimen- as a better predictor. tal forest in relation to of 2000. Taiwan J. For. Sci. 20: 73–87. ACKNOWLEDGMENTS KNUTSON, T. R., J. L. MCBRIDE,J.CHAN,K.EMANUEL,G.HOLLAND,C.LANG- SEA,I.HELD,J.P.KOSSIN,A.K.SRIVASTAVA, AND M. SUGI. 2010. Trop- – The study was supported in part by National Science Council ical cyclones and climate change. Natural Geoscience 3(3): 157 163. LAM,P.K.S.,AND D. D UDGEON. 1985. Seasonal effects on litterfall in a Hong (NSC100-2321-B-003-002). We thank Lienhuachi research center Kong mixed forest. J. Trop. 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