Rainfall Changes Over Tropical Montane Cloud Forests of Southern
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RESEARCH COMMUNICATIONS 15. Hirsch, R., Ternes, T., Haberer, K. and Kratz, K. L., Occurrence especially during summer monsoon season. The high- of antibiotics in the aquatic environment. Sci. Total Environ., est level of reduction for summer monsoon season was 1999, 225, 109–118. observed at Gavi rainforest station (>20 mm/14 years) 16. Hartmann, A., Golet, E. M., Gartiser, S., Alder, A. C., Koller, T. in Kerala followed by Venniyar (>20 mm/20 years) and Widmer, R. M., Primary DNA damage but not mutagenicity site in Tamil Nadu. Average annual and total precipi- correlates with ciprofloxacin concentrations in German hospital wastewater. Arch. Environ. Contam. Toxicol., 1999, 36, 115–119. tation increased during the study period irrespective 17. Jarnheimer, P. A. et al., Fluoroquinolone antibiotics in a hospital of the seasons over Periyar area, and the greatest sewage line; occurrence, distribution and impact on bacterial resis- values were recorded for season 2 (>25 mm/28 years). tance. Scand. J. Infect. Dis., 2004, 36, 752–755. Positive trends for winter monsoon rainfall has been 18. Hartmann, A., Alder, A. C., Koller, T. and Widmer, R. M., Identi- observed for three stations (Periyar, High wavys and fication of fluoroquinolone antibiotics as the main source of umuC Venniyar) except Gavi, and the trend was positive and genetoxicity in native hospital wastewater. Environ. Toxicol. significant (90%) for Periyar and High wavys. Chem., 1998, 17, 377–382. Increase in summer monsoon rainfall was observed 19. Kummerer, K., Significance of antibiotics in the environment. J. for Periyar site and the trend was found to be signifi- Antimicrob. Chemother., 2003, 2, 5–7. cant (95%). ACKNOWLEDGEMENTS. We thank Swedish Research Council, Keywords: Meghamalai, montane cloud forest, precipi- Stockholm, Sweden, for funding the research project; Dr V. K. Ma- tation change. hadik of UCTH and CRGH for useful suggestions; Management of UCTH and CRGH for allowing the conduct of this study; Karin Tonderski, from IFM, Linköping University, Sweden for useful discus- TROPICAL montane cloud forests (TMCFs) occur where sions, and Vivek Parashar and Dinesh Damde for assistance during mountains are frequently enveloped by trade wind- sampling. derived orographic clouds and mist in combination with convective rainfall1. One of the most important direct im- Received 11 March 2009; revised accepted 23 November 2009 pacts of frequent cloud cover is the deposition of cloud droplets through soil and vegetation surfaces (horizontal precipitation) which has immense hydrological impor- tance in the cloud forest ecosystems2. Data collected from Rainfall changes over tropical around the world show that horizontal precipitation can montane cloud forests of southern account for up to 14–18% and 15–100% of total precipi- tation during the wet and dry season respectively. A high Western Ghats, India annual deforestation rate in tropical mountain forests caused by harvesting fuel wood, resource logging and Muthusamy Murugan1,*, agricultural conversion is increasingly threatening cloud 3,4 Paddu Krishnappa Shetty1, Auvudai Anandhi2, forest worldwide . Although cloud forests provide habi- Raju Ravi3, Subbiah Alappan4, tats to many of the endangered species, most TMCFs are Muhund Vasudevan5 and Sreeja Gopalan1 in the mountain ranges as the core of tropical biodiversity ‘hotspots’ that occupy approximately 0.4% of Earth’s 1 School of Natural Sciences and Engineering, land surface while supporting about 20% and 16% of National Institute of Advanced Studies, 5 Indian Institute of Science Campus, Bangalore 560 012, India Earth’s plants and vertebrates correspondingly . There- 2CUNY Institute for Sustainable Cities, Hunter College, fore, the conversion status of these unique ecosystems is City University of New York, New York, USA critical and precarious as they are among the most endan- 3Department of Materials Engineering, gered of all forest types6. Indian Institute of Science, Bangalore 560 012, India India has only two TMCF mountain regions, which are 4Spices and Plantation Crops Advisory Services, Cumbum 625 556, India located in north-eastern Indian states and southern West- 5Department of Atmospheric Sciences, ern Ghats bordering the states of Tamil Nadu and Kerala. Jawaharlal Nehru Centre of Advanced Scientific Research, Most of the southern Western Ghats seasonal montane Bangalore 560 064, India cloud forests are located around the cardamom hills which are exposed to trade winds during the monsoon The southern Western Ghats tropical montane cloud seasons. Among TMCF regions of the world, the Indian forest sites (Gavi, Periyar, High wavys and Venniyar), TMCFs are the least studied climatologically and which are characterized by frequent or seasonal cloud cover at the vegetation level, are considered one of the explored biological wealth. Of all the types of tropical forest, tropical montane cloud forests are especially most threatened ecosystems in India and the world. 7 Three out of four montane cloud forest sites studied in vulnerable to climate change . The formation of cloud the southern Western Ghats had experienced dimin- bank is affected not only by global climate change; there ishing trends of seasonal average and total rainfall, is also evidence that regional and local land-use change can have significant influence. Climatologists found that *For correspondence. (e-mail: [email protected]) deforested Caribbean lowlands of Costa Rica remained CURRENT SCIENCE, VOL. 97, NO. 12, 25 DECEMBER 2009 1755 RESEARCH COMMUNICATIONS relatively cloud-free in dry season whilst adjacent for- tage of using non-parametric over parametric tests is that ested regions had well-developed cumulus clouds. These they are more suitable for non-normally distributed and forested lowlands are upwind of the Monteverde cloud censored data which are frequently encountered in meteo- forests, where reduced cloud cover had already been rological time series10. Mann–Kendall test reliably identi- documented6. fies monotonic linear and nonlinear trends with outliers11. Overall, global land precipitation has increased by One of the difficulties encountered in the interpretation of about 2% over the 20th century8. This increase is neither the climate data is the quantification of trends (e.g. calcu- spatially nor temporally uniform. This general increase lation of slope). To quantify the slope we used Sen’s non- contrasts with decreases in the northern subtropics. parametric estimator of slope12. This method estimates Record low precipitation has been observed in equatorial the slope of each trend as median of all pair-wise slopes. regions in the 1990s. Small increases are observed in the The significance of the test was evaluated using two- southern sub-tropical landmasses9. Since precipitation is tailed Z-test. The significant level was varied from 1 to the main driver of ecosystem function and structure we 10. In addition, LOESS procedure was used to reduce the have tried to reveal the precipitation variability and noise inherent in climate data to allow qualitative visual change in one of the most vulnerable tropical montane examinations of temporal changes in these data. LOESS cloud forest systems so that this information on climate uses a least square regression approach to consider the variation can be useful to tropical montane cloud forest user defined proportion of the data to weigh each regres- conservation communities interested in addressing the sion point. A p-value of <0.05 was used to indicate statis- climate change issues. tical significance, using two-tailed Z-test. The data was The location of stations studied is given in Figure 1. smoothed using a five-point binomial filter. The trend Daily rainfall amounts were summed up to obtain values were obtained from a linear regression. The sig- monthly, seasonal and annual values. Five statistics were nificance of the trend (at 90% and 95%) was tested using analysed on these climatic variables and are reported the F statistic. The geographical locations of rain gauge here: (1) Arithmetic mean of precipitation at annual, sea- stations have been furnished in Table 1. sonal (season 1 represents January to May; season 2 Analysis of observed precipitation data across stations comprises June to September, and season 3 pertains to of TMCFs area in southern India showed greater varia- October–December) and monthly time-scale. (2) Tempo- tions. At the rainforest site of Gavi, the average and total ral trends were evaluated at annual, seasonal and monthly rainfall at seasonal scale changed downwards, which was time-scale using Mann–Kendall method. (3) Slope of each significant for the study period 1994–2007 (Figure 2 b). trend was identified by Sen slope method as a median of Seasons 1 and 2 had a slight increase in average and total all pair-wise slopes. (4) Variation in daily temperature rainfall for the period (Figure 2 a). Monthly total rainfall range Mo. (5) Significant trends were identified at annual, of July, August, November, January and February regis- seasonal and monthly scale in using two tailed Z-test. (6) tered decreasing trend while other months have reported Locally weighted scatter plot smooth (LOESS) procedure positive values. In Periyar Tiger Reserve at Periyar sta- was used to reduce the noise inherent in climate data tion, the annual average and total precipitation showed to allow quantitative visual examination of temporal linear positive trends for the period under study (1980– changes in these data. Temporal trends