Journal of Environmental Biology

Time scale influence on water and soil conservation effect of plot trees

in Southern China

WU Xiao-Xia¹, GU Zhu-Jun¹*, LIU Zhen-Bo² and ZHU Gao-Long³

¹School of Environmental Science, Nanjing Xiaozhuang University, Nanjing-211 171, China

²School of Geography and Remote Sensing, Nanjing University of Information Science and Technology, Nanjing-210 044, China

³Department of Geography, Minjiang University, Fuzhou-350 108, China

*Corresponding Author E-mail: zhujungu@163.com

Publication Data

Paper received:

14 October 2015

Revised received:

11 December 2015

Accepted:

26 December 2015

Abstract

The vegetative effect on water and soil conservation is a key matter worldwide for water and soil loss research and management. However, few quantitative studies concerning these effects over multiple time scales have been conducted. In the present study, rainfall characteristics, vegetation fractional coverage (VFC), runoff and soil loss of five tree plots (Pinus massoniana) in Hetian Town, Changting County of Fujian Province, a typical water-eroded area in Southern China, resulting from each of the 144 natural erosive rainfall events that occurred from 2007 to 2010 were measured. VFC and water/soil conservation effect (RE/SE) quadratic polynomial regression models were established for various time scales, including each rainfall event, month, season and year.? RE/SE was used to represent the runoff depth/soil loss ratio of tree plots to control plot. The models and their respective model determination coefficients (R2) were analyzed in order to compare the effects of the water and soil conservation measures over different time scales. The results indicated that both RE and SE exhibited linearly descending (DS), descending-ascending (DA), ascending-descending (AD), and linearly ascending (AS) trends as vegetation fractional coverage increased. Four of the effect types exhibited similar trends over individual event and monthly time scale and gradually decreased over larger time scales. The AS trends diminished over seasonal scale, and DA trends were most prominent over the yearly scale. The runoff/soil loss weight coefficients (contributions) of DS and DA trends were higher, with sum ranging from 50% to 80%, and increased as time scales became larger. Most of the mean R² values of VFC-RE/SE models exceeded 0.6. As time scale increased, the mean R² values of VFC-RE models either descended linearly or initially ascended then descended. Maximum mean R² values of AD and DA trends occurred over seasonal scales. The mean R² values of VFC-SE models either ascended linearly or initially ascended then decreased as time scale increased. Maximum mean R² values of DS, DA, and AD trends also occurred over seasonal scale. Therefore, individual event and monthly time scales were optimal for observing various vegetative effects of water and soil conservation measures, while seasonal time scales were most suitable for evaluating the effect of water and soil conservation measures on tree plots. These results could be used as a reference for vegetative reconstruction research and management in water-eroded areas.    

 Key words

Runoff, Soil loss, Time scale, Vegetation fractional coverage, Water and soil conservation effect

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