Relationship between Net Primary Productivity and Forest Stand Age under Different Site Conditions and Its Implications for Regional Carbon Cycle Study

Bin Wang,Mingze Li,Jing Chen,Ying Yu,Wenyi Fan

doi:10.3390/f9010005

Abstract

Net primary productivity (NPP) is a key component in the terrestrial ecosystem carbon cycle, and it varies according to stand age and site class index (SCI) for different forest types. Here we report an improved method for describing the relationships between NPP and stand age at various SCI values for the main forest types and groups in Heilongjiang Province, China, using existing yield tables, biomass equations, and forest inventory data. We calculated NPP as the sum of four components: Annual accumulation of live biomass, annual mortality of biomass, foliage turnover, and fine root turnover in soil. We also consider the NPP of understory vegetation or moss. These NPP-age relationships under different site conditions indicate that the NPP values of broadleaved and coniferous, as well as broadleaved mixed forests increase rapidly and reach a maximum when in young forests. However, for coniferous forest types, the maximum NPP generally occurs in mature forests. In addition, a higher SCI leads to a higher NPP value. Finally, we input these NPP-age relationships at various SCI values into the Integrated Terrestrial Ecosystem Carbon (InTEC) model to modify NPP modeling to estimate NPP in Heilongjiang Province in China from 2001 to 2010. All of the results showed that the methods reported in this study provide a reliable approach for estimating regional forest carbon budgets.

Highlights

Net primary production (NPP) reflects biological properties and stand structures for a forest ecosystem, and describes the influence of environmental factors on forest growth [1].Growth is substantially affected by CO2 fertilization, climate variability, nitrogen (N) deposition [2,3], and disturbance factors, such as wildfires, harvesting, and insects [4,5,6]
Our results showed that NPP varied with stand age and site class index (SCI), presenting a generally consistent trend of NPP-age relationships at various SCI values for different forest types and groups across the Heilongjiang Province, China
We developed a specific method for estimating the relationships between NPP and age, at different SCI values for 12 forest types and groups, based on data from yield tables, biomass equations, and forest inventories

Summary

Introduction

Net primary production (NPP) reflects biological properties and stand structures for a forest ecosystem, and describes the influence of environmental factors on forest growth [1]. Growth is substantially affected by CO2 fertilization, climate variability, nitrogen (N) deposition [2,3], and disturbance factors, such as wildfires, harvesting, and insects [4,5,6]. Disturbances are major determinants of forest carbon stocks and uptake They generally reduce land carbon stocks and initiate a regrowth legacy that contributes substantially to the contemporary rate of carbon stock increase in forestlands [7]. NPP is affected by forest age, and by factors related to environmental site conditions.

Objectives

Methods

Results

Discussion

Conclusion