Understory plant diversity assessment of Eucalyptus plantations over three vegetation types in Yunnan, China

Abstract

Biodiversity in managed plantations has become an important issue for longterm sustainability of ecosystems. The environmental effects of plantations comprised of fast-growing introduced trees have been vigorously debated. On one hand, monocultures have been said to exhaust resources, resulting in decreased biodiversity. Conversely, it has been stated that monocultures may favor regeneration of undergrowth plants from surrounding forests, increasing biodiversity. In order to clarify the effects of planting Eucalyptus trees on species composition, diversity, and functional type of understory vegetation in Yunnan province, a field trial was implemented to compare Eucalyptus plantations (EPs) with two other local current vegetation types (secondary evergreen forests (SEs), and abandoned farmlands (AFs)). Each vegetation type was sampled in each of three elevational ranges (low = 1,000-1,400 meters above sea level (masl), medium = 1,400-1,800 masl, and high = 1,800-2,200 masl). Sample sites within each elevational range had similar environmental characteristics (slope, aspect, etc.). Thus, we sampled three vegetation types at each of three sites at each of three elevations for a total of 27 plots. We calculated relative abundance and importance value of species and diversity indexes to evaluate differences among local current vegetation types and elevational ranges, employing multivariate ordination analyses and other methods such as Analyses of Variance (ANOVA) and Indicator Species Analysis. We found that fast growing introduced Eucalyptus plantations led to reduced plant diversity in the study area, and that rare or threatened species were recorded almost exclusively in the SE plots, being essentially absent from the EP and AF plots. The understory plant diversity did not correlate with the altitude gradient significantly. Eucalyptus plantations (EPs) have a simpler community structure than that of either secondary evergreen forests (SEs; similar to natural state) or abandoned farmlands (AFs). No variable significantly explained variation of the understory shrub layer, but soil moisture-holding capacity and overstory coverage were significant in explaining variation of the understory herb layer, suggesting that the study of soil physical properties is necessary for better understanding of their importance in Eucalyptus plantations and other local current vegetation types.

Should Exotic Eucalyptus be Planted in Subtropical China: Insights from Understory Plant Diversity in Two Contrasting Eucalyptus Chronosequences

“…They reported that the Wang et al (2011) indicated that Eucalyptus plantations reduced several woody plants compared with secondary evergreen forests, which is supported by our findings. The marginal effects of first rotation on plant diversity in the understory were also found in a 6-yearperiod experiment, wherein the introduced Eucalyptus did not significantly change the plant diversity (Fabião et al 2002).…”

“…The reasons for the plant diversity dynamics are unknown because few studies were conducted in these regions. We first speculated that the soil seed bank did not change in the short time-scale although some sensitive plants would disappear (Gaertner et al 2011;Wang et al 2011). Because the Zhangzhou chronosequence was established from native Chinese fir forests, it should have the similar soil seed bank under the same site preparation.…”

Soil stoichiometry and carbon storage in long-term afforestation soil affected by understory vegetation diversity

“…Zhang et al, 2010). In addition, plant diversity in the plantation understory plays important roles in improving stimulating the soil nutrient cycling and maintaining soil quality after afforestation (Halpern 1995;Wang et al, 2011). Brockerhoff et al (2003) reported that wider tree spacing during plantation establishment supports better maintenance of understorey vegetation.…”

Understory Structure and Vascular Plant Diversity in Naturally Regenerated Deciduous Forests and Spruce Plantations on Similar Clear-Cuts: Implications for Forest Regeneration Strategy Selection

“…The conflicting results presented in the literature regarding species richness and understory vegetation structure are due to several inconsistent factors used when making comparisons: different historical origins of previous vegetation [12], distinct initial site condition [22,23], different successional stage or forest age [16,24,25], target tree identity and mixture [10,11], and site degradation intensity and management [11,12,14,22]. To reach reliable conclusions on the effects of different regeneration methods on understory vascular plant composition and diversity requires controlling variability among study sites.…”