McPherson G R, Boutton T W, Midwood A J
Forest-Watershed Sciences Program, School of Renewable Natural Resources, University of Arizona, 85721, Tucson, AZ, USA.
Department of Rangeland Ecology and Management, Texas A & M University, 77843, College Station, TX, USA.
Oecologia. 1993 Feb;93(1):95-101. doi: 10.1007/BF00321197.
In southeastern Arizona, Prosopis juliflora (Swartz) DC. and Quercus emoryi Torr. are the dominant woody species at grassland/woodland boundaries. The stability of the grassland/woodland boundary in this region has been questioned, although there is no direct evidence to confirm that woodland is encroaching into grassland or vice versa. We used stable carbon isotope analysis of soil organic matter to investigate the direction and magnitude of vegetation change along this ecotone. δC values of soil organic matter and roots along the ecotone indicated that both dominant woody species (C) are recent components of former grasslands (C), consistent with other reports of recent increases in woody plant abundance in grasslands and savannas throughout the world. Data on root biomass and soil organic matter suggest that this increase in woody plant abundance in grasslands and savannas may increase carbon storage in these ecosystems, with implications for the global carbon cycle.
在亚利桑那州东南部，牧豆树（Prosopis juliflora (Swartz) DC.）和埃默里栎（Quercus emoryi Torr.）是草地/林地边界的主要木本物种。尽管没有直接证据证实林地正在侵入草地或反之亦然，但该地区草地/林地边界的稳定性受到了质疑。我们利用土壤有机质的稳定碳同位素分析来研究沿着这个生态交错带植被变化的方向和幅度。沿着生态交错带的土壤有机质和根系的δC值表明，两种主要木本物种（C）都是前草地（C）的近期组成部分，这与世界各地草地和稀树草原木本植物丰度近期增加的其他报道一致。关于根系生物量和土壤有机质的数据表明，草地和稀树草原木本植物丰度的这种增加可能会增加这些生态系统中的碳储存，对全球碳循环产生影响。
