The Effect Of Tending On The Undergrowth And Regeneration Of Pinus Tabulaeformis Plantations In The Loess Plateau

Pinus tabuliformis had strong adaptability and resistance.It can keep soil and water,conserve water and improve soil well.Plantation of P.tabuliformis was an important part of vegetation in Loess Plateau.Undergrowth was composed of shrubs and herbs,which was an important part of forest ecosystem and directly affected the ecological benefits of plantation.Tending was one of the measures of forest management,which was the artificial disturbance to natural forest and artificial forest under the guidance of human purposeful behavior.Tending had an important impact on the growth of forest trees and the development and distribution of undergrowth vegetation because it can adjust the forest structure,change the light,temperature and soil nutrients,water and other resources in the forest.How could the artificial tending measures(sanitation cutting)affect the growth and regeneration of undergrowth in the P.tabulaeformis plantation on Loess Plateau?How would the biomass of undergrowth change after tending?What reasonable tending measures and intensity would be taken to promote the development of understory vegetation?How undergrowth to response to the short-term tending?However,there were less researches to these questions.In March 2015,the artificial P.tabuliformis forest in Qingshuigou conservation of Malan forest area was tended by the Xunyi County Forestry Bureau.The main measure was sanitation cutting(The windfall,dead and dying tree and disease wood were cut off,and all the brush under the forest was cut off on the ground,and the artificial pruning of the tree body of P.tabuliformis below 3-4 m was carried out.).To study the short-term impact of tending measures on the growth status of the undergrowth of the artificial P.tabuliformis forest,we studied the tending and non-tending areas of a 45-year-old artificial P.tabuliformis forest on Loess Plateau.Changes on vegetation structure,regeneration and biomass of understory plants were detected after tending.This study aimed to provide theoretical basis for the scientific tending of P.tabuliformis plantation on Loess Plateau and empirical data for studies of long-term dynamic.Main conclusions in this paper were:(1)There were 33 families,57 genera and 67 species of understory vegetation.The number of families,genera,and species increased after tending,which suggested that tending can increase the richness of undergrowth.The density and coverage of the herbs increased significantly while that of the shrubs decreased after tending.(2)Under-forest light and conditions such as temperature,humidity,and soil improved.Due to the removal of all shrubs,the competitive pressure from the shrubs decreased,the growth and nutrient space of herbs increased.The biomass of herbs increased significantly.The shrubs have a long renewal time,and the shrubs cleared in a short period of time after tending have not fully recovered.As a result,the biomass of shrubs and total undergrowth biomass decreased significantly.The belowground and aboveground mass ratio of the herbs decreased after tending.The shrubs still not recovered,the stems and leaves were less renewed,so the belowground and aboveground mass ratio of the shrubs increased.The allocation of biomass in different species in undergrowth was significantly changed by tending measures.The proportion of biomass contribution of heliophytes and hygrophytes increased after tending.(3)There were significant correlatios among the six kinds of shrubs in tending plots and non-tending plots,which reaeched to extremely significant levels.The models were well-fitted.The best biomass estimating models of shrub spieces were polynomials and power functions,and D2H,D,H,were the best model parameters,they had highly correlation.(4)The species richness,Simpson index,Shannon index,and Pielou index of the understory seedlings in the tending and non-tending plots all showed significant differences,showing tending area>non-tending area.The species richness of understory saplings showed the non-tending area>tending area.The Simpson index,Shannon index and Pielou index all increased after sanitation cutting.Sanitation cutting in tending plots improved the growth environment of seedlings and saplings under the forest,and promoted the regeneration of understory seedlings and saplings.The density,height and coverage of understory seedlings showed the non-tending area<tending area.The density of saplings between tending and non-tending areas was not significantly different.The differences in height and coverage of saplings were significant,showing the non-tending area>tending area.(5)The saplings at 150-300cm height were significantly reduced,and the saplings at 30-50cm height were significantly increased.Seedlings at heights of 1-5 cm and heights of 26-30 cm increased significantly after tending.Tending promoted the process of the development from seeds to seedlings,the number of saplings developed through seedling,and the number of saplings developed into mature trees.Saplings with a steam diameter of 1-5 cm increased significantly,while 15-30 cm saplings significantly decreased by tending.In general,the number of saplings decreased as the steam diameter increased.In the tending area,seedlings accounted for 93.9%of the total number of seedlings,which accounted for 98.4%of the total number of seedlings in the non-tending areas.Sprouting seedlings accounted for 6.1%of the total number in the tending area,which accounted for 1.6%of the total number in the non-tending area.The main regeneration type was seedling.