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The distributions of long chain n-alkanes and their hydrogen isotope values (delta H-2(alk)) can be used to investigate paleoclimatic changes, but, as yet, the degree to which plant types, temperature and/or hydrology may drive such variations, cannot be discriminated. Seven co-occurring herbaceous plants (angiosperms) were studied in climate-controlled growing conditions in an open-top chamber located in Naqu, Tibet, in 2015 and 2017, using generalized n-alkane parameters, viz. n-alkane concentrations (Conc(alk)), the carbon preference index (CPI) and the average chain length (ACL), and delta H-2(alk) values. These plants were subjected to warming (W, spanning a < 4 degrees C mean annual temperature (MAT) gradient) and the amount of water that plants received (100% precipitation differences) conditions in 2015 and 2017, respectively. Growth experiments showed that: (1) No significant relationships were found between n-alkane parameters (Conc(alk), ACL and CPI) and temperature (a 4 degrees C difference) or precipitation (100% precipitation differences); (2) The delta H-2(alk) increased ca. 10-30 parts per thousand during W 4 degrees C conditions, with differences in the sensitivity of responses to W between different species. During P treatments, the variability in delta H-2(alk) values was close to that caused by a W 4 degrees C response; and 3) the interspecies variability in n-alkane distributions and delta H-2(alk) (ca. 30-50 parts per thousand) was higher than that caused by these P and W responses. These results highlight the importance of the potential impact of any changes in the floral assemblage when interpreting sedimentary n-alkane distributions and delta H-2(alk) records. (C) 2019 Elsevier Ltd. All rights reserved.