Various response of Pinus tabulaeformis Carr. regeneration in artifical gaps

Zhibin Wang,Lvyi Ma,Haijiao Yang,Kuangji Zhao,Zhongkui Jia

doi:10.1038/s41598-017-15322-8

Abstract

Understanding the influence of gaps in promoting canopy recruitment will help to maintain structural stability and achieve continuous forest cover. We established three control plots and experimental plots with three replications each (gap sizes L-I, L-II, L-III, and L-IV) in a Chinese pine (Pinus tabulaeformis Carr.) plantation to test the short-term effects of gap size on the age distribution, density and growth, and annual height and ground diameter growth for regeneration established before (REBG) and after (REAG) gap creation. Age distribution exhibited an approximately normal distribution, with the numbers of REBG and REAG decreasing and increasing, respectively, as the age increased. Although there was no difference in density among gap size classes, regeneration growth positively responded to gap size, with maximum values observed in class L-III. Annual average height growth after (AAH-A) gap creation was significantly greater than that before (AAH-B) gap creation for REBG among gap sizes, suggesting that gaps promote the rapid growth of regeneration. However, the responses of height and ground diameter growth in REBG to gap size were not immediate and exhibited a response delay of 2–4 years. Similarly, for the height and ground diameter growth of REAG, significant differences were first observed within years 2–4 after germination in the same growing season for all gap size classes.

Highlights

In recent decades, forest management practices have resulted in the transformation of even-aged forests, especially coniferous forests, into uneven-aged or mixed forests[1,2]
To better understand the extent to which gap size affects regeneration in a Chinese pine plantation, the Chinese pine regeneration in gaps was divided into two categories: REBG refers to Chinese pine regeneration established before gap creation, and REAG refers to Chinese pine regeneration established after gap creation
A frequency histogram of regeneration age for the different gap size classes exhibited an approximately normal distribution, with the peak at the age of seven (Fig. 1a–d) for all classes except class L-IV, where the peak occurred at the age of eight after the creation of gaps (Fig. 1e)

Summary

Introduction

Forest management practices have resulted in the transformation of even-aged forests, especially coniferous forests, into uneven-aged or mixed forests[1,2]. Chinese pine (Pinus tabulaeformis Carr.) is an endemic species with strong adaptability in China It can mix with some broadleaf trees to form a good stand structure and be treated as the main timber species, and it plays an important role in soil and water conservation and vegetation restoration in northern China[11,12]. Wang and Liu[2] illustrated that opening gaps increased the regeneration density and led to some regeneration becoming dominant in specific gap sizes These findings were similar to those of Dong et al.[14], who tested the responses of natural regeneration to gap sizes (4–40 m2) in a stand with a canopy density of 0.7 and found that density, height and ground diameter of regeneration in gaps were 2.5–7.0, 1.0–1.7 and 1.0–1.6 times greater than that which occurred under the canopy, respectively. The objectives of this research were to: (i) assess the age distribution of regeneration in different gap sizes, (ii) identify changes in density and growth of REAG and REBG in response to different gap sizes, and (iii) determine whether the height and ground diameter growth of REAG and REBG respond immediately to the creation of gaps

Objectives

Methods

Results

Discussion

Conclusion