Effects of stand age, richness and density on productivity in subtropical forests in China

Abstract

Forest productivity may be determined not only by biodiversity but also by environmental factors and stand structure attributes. However, the relative importance of these factors in determining productivity is still controversial for subtropical forests. Based on a large dataset from 600 permanent forest inventory plots across subtropical China, we examined the relationship between biodiversity and forest productivity and tested whether stand structural attributes (stand density in terms of trees per ha, age and tree size) and environmental factors (climate and site conditions) had larger effects on productivity. Furthermore, we quantified the relative importance of environmental factors, stand structure and diversity in determining forest productivity. Diversity, together with stand structure and site conditions, regulated the variability in forest productivity. The relationship between diversity and forest productivity did not vary along environmental gradients. Stand density and age were more important modulators of forest productivity than diversity. Synthesis. Diversity had significant and positive effects on productivity in species‐rich subtropical forests, but the effects of stand density and age were also important. Our work highlights that while biodiversity conservation is often important, the regulation of stand structure can be even more important to maintain high productivity in subtropical forests.

Stability in subtropical forests: The role of tree species diversity, stand structure, environmental and socio‐economic conditions

“…This might be attributable to the favourable temperature conditions of our study region, with an average annual air temperature of 16–18°C (Huang et al., 2014). Moreover, the magnitude of variation in annual air temperature was not large enough to lead to significant changes in forest productivity in our study region (Ouyang et al., 2019). Our results reveal that stability is highly sensitive to fluctuations in rainfall, which mainly affect stability via increasing the variability in productivity.…”

“…After the total stock volume for each plot was calculated, the total biomass was estimated using the biomass expansion factor method, which is an accurate method for estimation of forest biomass at large scales (Fang et al., 2014). The forest productivity was then determined as biomass increments between two inventories (Ouyang et al., 2019).…”

“…Subtropical forests are an important hotspot of tree species richness, often in heterogeneous environments (Liu et al., 2018; Xiang et al., 2016). These forests have a high capacity for carbon (C) storage and have the potential to sequester huge amounts of C in the future (Liu et al., 2018; Ouyang et al., 2019). Nevertheless, anthropogenic disturbances (e.g., logging, agriculture and urban expansion) have resulted in drastic changes in ecological conditions that have caused biodiversity loss and reduced the capacity of these forests to maintain important ecosystem functions and services (Liu et al., 2018).…”

“…In order to study the effects of such factors on stability, the statistical replication of biomass or productivity should be sufficiently large (e.g., Jucker et al., 2014; del Rio et al, 2017). Large‐scale estimates of biomass have been derived successfully from national forest inventory (NFI) data and have provided important insights into large‐scale forest biomass stock and productivity dynamics (Fang et al., 2014; Ouyang et al., 2019; Pan et al., 2011).…”

Patterns of Density and Production in the Community Forests of the Sierra Madre Occidental, Mexico

“…On the other hand, dominant height has the advantage of being hardly influenced by stand management measures such as thinning [38], although it can be affected by very low or very high stand densities [45]. In addition, forest structural attributes, such as number of trees and average tree size, may affect biomass productivity in natural forests [46]. Production in multispecies natural forests normally depends on site conditions, structural attributes, species composition, and forest density, as well as the interaction between these factors [47][48][49].…”