Health Assessment Of Trees In Residential Areas Of Beijing

Healthy urban forests not only provide a pleasant natural landscape,but also promote the physical and mental health of urban residents.The living environment and living quality of urban residents depend on the function of urban trees.In this study,we aimed to identify the variations and factors determining tree health in residential areas of Beijing,and provide recommendations to tree health managements,by investigating 85 residential areas in Beijing.In order to reveal tree health problem of residential areas,trees structure,situation of management and protection,growth circumstance conditions were analyzed from different districts,different origins,different periods and different greenbelts.Tree health assessment model was built from individual and population,and then,trees health precision management measures was put forward in residential areas of Beijing.The main conclusions are as follows:1.Characteristics of forest structure in residential areasTree species in residential areas of Beijing are richer.Proportion of number,frequency and important value of Sophora japonica are highest than other species of residential areas.The ratio of native tree species and exotic tree species is 3.8:1.Although exotic tree species are abundant,they are few.There was no obvious rule of trees diversity index in residential areas with different regions and origins.The variation of trees diversity index in residential areas of different periods was basically same and showed a decreasing trend.Trees diversity index of different greenbelt is the best in housing greenbelt and the worst in road greenbelt.The average density of tree species in residential areas was 192 numbers/hm~2,and basal area per hectare was 9.32m~2/hm~2.Trees in residential areas of Beijing are mainly medium and young,and the DBH and height of the trees are normally distributed on the left,with an average DBH of 21.6m and an average height of 9.9m.With expansion of ring road and passage of period,tree DBH and height showed a decreasing trend.The rate of branch and leaf diseases of different degrees was 8.68%,but incidence of trunk diseases was fewer,only 1.87%.About 5.98%of trees were affected by insect pests of branches and leaves to varying degrees,with light insect pests of trunk(1.65%).The phenomenon of dead branches was more common,with 63.07%of dead branches of different degrees,most of which were small branches,and 13.07%of serious dead branches.There were dead shoots in 2.74%of the trees.The proportion of trunk mechanical injury was 4.09%.More than half of the trees were overly pruned when planting,while 23.96%of the pruning when protection.59.33 percent of trees was effectively managed.The organic surface cover of trees accounted for 13.53%,green covers was 19.61%,proportion of ecological brick covers was the largest,no covers was 22.65%,and hard pavement was(0.28%)the least.2.Trees individual health assessment of residential areas in BeijingTrees individual health indices in all residential areas of Beijing tested were 0.54?0.77,and tree health was characteristic of a near normal distribution.Healthy trees accounted for2.38%,sub-healthy trees accounted for 39.00%,medium-healthy trees accounted for 50.25%,unhealthy trees accounted for 7.97%,and dying trees accounted for 0.40%.Tree health indices were not significantly different(P>0.05)between residential areas in different districts,while differences between different assessment periods and origins were significant(P<0.05).Ranks of trees health indices in difference types of residential area are presented:4th-5th ring road>3rd-4th ring road>5th-6th ring road>2nd-3rd ring road>within2nd ring road;commodity apartment>welfare housing>social security housing;2009-2013>2003-2008>1998-2002>1991-1997>1956-1990;garden greenbelt>housing greenbelt>road greenbelt.3.Trees population health assessment of residential areas in BeijingTrees population health levels in all residential areas of Beijing tested were judged as sub-healthy state.Healthy state accounted for 17.65%,sub-healthy state accounted for 52.94%,medium-healthy state accounted for 22.35%,unhealthy state accounted for 4.71%,and dying state accounted for 2.35%.Tree population health indices were not significantly different(P>0.05)between residential areas in different districts and origins,as well as different periods.Ranks of trees population health indices in difference types of residential area are presented:within 2nd ring road>3rd-4th ring road>4th-5th ring road>2nd-3rd ring road>5th-6th ring road;welfare housing>commodity apartment>social security housing;2009-2013>1956-1990>1991-1997>2003-2008>1998-2002.In view of the current situation of healthy growth of trees in residential communities of Beijing,this paper puts forward reasonable suggestions on trees health problems of residential areas in different districts,different sources,different periods as well as different greenbelts of residential areas.