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Changes in dissolved organic carbon and total dissolved nitrogen fluxes across subtropical forest ecosystems at different successional stages
Author(s) -
Yan Junhua,
Li Kun,
Wang Wantong,
Zhang Deqiang,
Zhou Guoyi
Publication year - 2015
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2015wr016912
Subject(s) - environmental science , dissolved organic carbon , ecological succession , forest ecology , surface runoff , temperate forest , ecosystem , flux (metallurgy) , nitrogen , terrestrial ecosystem , hydrology (agriculture) , temperate rainforest , ecology , chemistry , biology , geology , geotechnical engineering , organic chemistry
Lateral transports of carbon and nitrogen are important processes linking terrestrial ecosystems and aquatic systems. Most previous studies made in temperate forests found that fluxes of carbon and nitrogen by runoff water varied in different forests, but few studies have been made in subtropical forests. This study was to investigate dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) fluxes at the catchment scale along a subtropical forest succession gradient from pine forest (pioneer) to coniferous and broadleaved mixed forest (transitional) to broadleaved forest (mature). Our results showed that DOC concentration significantly decreased ( p <0.001) while TDN concentration significantly increased ( p <0.001) in runoff water from pioneer to mature forests, which in turn resulted in a decrease in DOC flux and an increase in TDN flux, as mean annual runoff did not vary significantly among three succession forest catchments. The mean (±standard deviation) annual DOC flux was 118.1±43.6, 88.3±16.7 and 77.2±11.7 kg ha −1 yr −1 for pioneer, transitional and mature forest catchments, respectively; and the mean annual TDN flux was 9.9 ±2.7, 18.2±3.0 and 21.2 ±4.5 kg ha −1 yr −1 for pioneer, transitional and mature forest catchments, respectively. The mature forest reduced DOC flux by increased soil chemical adsorption and physical protection. An increase in TDN flux from pioneer to mature forests was consistent with the previous finding that mature forest was nitrogen saturated while pioneer forest was nitrogen limited. Therefore large‐scale conversion of pioneer forests to transitional or mature forests in subtropical China will reduce DOC concentration and increase TDN concentration in the down‐stream water, which may have significant impact on its water quality and aquatic biological activities.