The change of soil carbon stocks and fine root dynamics after land use change from a native pasture to a pine plantation

Abstract

A published meta-analysis of worldwide data showed soil carbon decreasing following land use change from pasture to conifer plantation. A paired site (a native pasture with Themeda triandra dominant, and an adjacent Pinus radiata plantation planted onto the pasture 16 years ago) was set up as a case study to assess the soil carbon reduction and the possible reason for the reduction under pine, including the change in fine root (diameter <2 mm) dynamics (production and mortality). Soil analysis confirmed that soil carbon and nitrogen stocks to 100 cm under the plantation were significantly less than under the pasture by 20 and 15%, respectively. A 36% greater mass of fine root was found in the soil under the pasture than under the plantation and the length of fine root was about nine times greater in the pasture. Much less fine root length was produced and roots died more slowly under the plantation than under the pasture based on observations of fine root dynamics in minirhizotrons. The annual inputs of fine root litter to the top 100 cm soil, estimated from soil coring and minirhizotron observations, were 6.3 Mg dry matter ha −1 year −1 (containing 2.7 Mg C and 38.9 kg N) under the plantation, and 9.7 Mg ha −1 year −1 (containing 3.6 Mg C and 81.4 kg N) under the pasture. The reduced amount of carbon, following afforestation of the pasture, in each depth-layer of the soil profile correlated with the lower length of dead fine roots in the layer under the plantation compared with the pasture. This correlation was consistent with the hypothesis that the soil carbon reduction after land use change from pasture to conifer plantation might be related to change of fine root dynamics, at least in part.

Above- and belowground patterns in a subalpine grassland-shrub mosaic

“…The only soil property correlated with R. ferrugineum cover was C content. Other studies also reported higher contents of organic C in forest than in grasslands (Guo et al 2007;Guidi et al 2014). As a consequence of reduced soil temperature and moisture following forest succession (Hiltbrunner et al 2013), the decomposition of organic matter is slowed down, leading to a decreased incorporation of C into soil aggregates (Gregorich et al 2006).…”

White Spruce Plantations on Abandoned Agricultural Land: Are They More Effective as C Sinks than Natural Succession?

“…Soil C stocks generally increase on depleted ex-croplands, and remain unchanged or decrease on ex-grasslands and ex-pastures with the progressive disappearance of their abundant root litter [42][43][44][45][46]. For example, Guo et al [47] observed, in an afforested pasture with pines, that the loss of soil C was positively correlated with the mortality volume of fine roots. However, fine root dynamic (production and mortality) was not measured in our study.…”

Variabilidade espacial dos atributos químicos do solo, associada ao microrrelevo

“…Isto altera atributos químicos, físicos e biológicos e esta alteração pode ser intensificada com práticas de manejo do solo (Guo et al, 2007). Assim, o estudo dessas superfícies torna-se premissa básica nos levantamentos pedológicos, na tomada de decisões em relação ao manejo do solo, intensidade e frequência de amostragem e gerenciamento de práticas agrícolas e avaliação dos efeitos da agricultura sobre a qualidade ambiental (Corá et al, 2004).…”