Long‐term changes in liana abundance and forest dynamics in undisturbed Amazonian forests

Abstract

Lianas (climbing woody vines) are important structural parasites of tropical trees and may be increasing in abundance in response to global-change drivers. We assessed long-term (-14-year) changes in liana abundance and forest dynamics within 36 1-ha permanent plots spanning -600 km2 of undisturbed rainforest in central Amazonia. Within each plot, we counted each liana stem (> or = 2 cm diameter) and measured its diameter at 1.3 m height, and then used these data to estimate liana aboveground biomass. An initial liana survey was completed in 1997-1999 and then repeated in 2012, using identical methods. Liana abundance in the plots increased by an average of 1.00% +/- 0.88% per year, leading to a highly significant (t = 6.58, df = 35, P < 0.00001) increase in liana stem numbers. Liana biomass rose more slowly over time (0.32% +/- 1.37% per year) and the mean difference between the two sampling intervals was nonsignificant (t = 1.46, df = 35, P = 0.15; paired t tests). Liana size distributions shifted significantly (chi2 = 191, df = 8, P < 0.0001; Chi-square test for independence) between censuses, mainly as a result of a nearly 40% increase in the number of smaller (2-3 cm diameter) lianas, suggesting that lianas recruited rapidly during the study. We used long-term data on rainfall and forest dynamics from our study site to test hypotheses about potential drivers of change in liana communities. Lianas generally increase with rainfall seasonality, but we found no significant trends over time (1997-2012) in five rainfall parameters (total annual rainfall, dry-season rainfall, wet-season rainfall, number of very dry months, CV of monthly rainfall). However, rates of tree mortality and recruitment have increased significantly over time in our plots, and general linear mixed-effect models suggested that lianas were more abundant at sites with higher tree mortality and flatter topography. Rising concentrations of atmospheric CO2, which may stimulate liana growth, might also have promoted liana increases. Our findings clearly support the view that lianas are increasing in abundance in old-growth tropical forests, possibly in response to accelerating forest dynamics and rising CO2 concentrations. The aboveground biomass of trees was lowest in plots with abundant lianas, suggesting that lianas could reduce forest carbon storage and potentially alter forest dynamics if they continue to proliferate.

Apparent environmental synergism drives the dynamics of Amazonian forest fragments

“…4). This difference suggests that the changes in liana abundance in intact forest might have had a different cause than those in fragments: one not directly related to increasing forest dynamics, such as, for instance, rising CO 2 levels (there is no evidence that droughts increased during our study; Laurance et al 2014). In fragments, however, a combination of elevated tree mortality (Fig.…”

“…By physically stressing trees and competing for light, nutrients, and water, liana infestations can reduce tree growth, fecundity, survival, and recruitment (Putz 1984, Stevens 1987, Schnitzer et al 2000, Schnitzer and Carson 2010, Yorke et al 2013. As a result, lianas can have a considerable impact on forest dynamics, tree-species composition, and carbon storage , 2014, Schnitzer and Bongers 2002, Ko¨rner 2004). …”

Effects of Understory Liana Trachelospermum jasminoides on Distributions of Litterfall and Soil Organic Carbon in an Oak Forest in Central China

“…Liana thus has the potential to alter forest C storage, by reducing tree growth and survival [18]. It has been widely reported that tree aboveground biomass is negatively correlated with liana abundance [10,18,35], which indicates the increase in liana under climate change [36,37] may reduce C storage of forest by the inhibition of growth. However, the positive effects of liana on litter accumulation and SOC found in this study may temper the negative influence of liana on forest C storage at the ecosystem level.…”

“…Well-developed root systems of lianas [16] could impact soil physicochemical property, such as soil texture and C substrate availability during root growth and turnover [17,18]. For example, it has been found that soil organic C (SOC) and total nitrogen (TN) content were increased because of root turnover and rhizodeposition in an agricultural vineyard [19].…”

Dinâmica, anatomia, biomecânica e condutividade hídrica de lianas da Floresta Amazônica

“…O aumento da abundância de lianas tem um efeito negativo no aumento da biomassa arbórea, reduzindo o crescimento e sobrevivência das árvores, assim como uma redução do armazenamento de carbono da floresta (Laurance et al 2014, Schnitzer & Bonger 2011, Phillips et al 2002. Como mencionado por Laurance et al (2014), três hipóteses têm sido propostas para explicar o aumento da abundância de lianas nas florestas maduras. A primeira é referente às estações secas que podem ter aumentado nas regiões tropicais, possibilitando uma mudança regional e global do clima.…”