CBES 601- Project 1- Kipuka system-Hilo, Hawaii
T D Kularatna
06/19/2019
The Abundance of Pink knot-weed (Persicaria capitata) in the Kipuka Plant Critical Habitat
Introduction
‘O ka lā‘au o ke kula e noho ana i ka ‘āina, o ka lā‘au o ka ‘āina e nalowale aku ana’
In the history of Hawaii, the prophecy of Kalaunuiohua mentioned that ‘trees from the faraway lands and beyond the sea will grow here and the native plants of this island will be vanished by the meantime. Ever since the arrival of the Polynesians, more than 100 (Nagata 1985) plant species were introduced into the Hawaiian Islands, as crops and ornamental. Many of these introduced plants escaped from the introduced areas and distributed around the island (Smith 1985). More than 100 plant species have now become naturalized (Cuddihy and Stone 1990) and more than 80 out of them can create serious ecological problems in native forest habitats. Therefore, native flora in the Hawaiian Islands is under a serious threat of extinction due to changes in the ecological structure and functions created by these exotic plant species.
This project was finding the impact of Persicaria capitata Kipuka system and the surrounded lava flow in the montane wet forest between upper Waiakea and Mauna Loa Forest Reserve. Persicaria capitata was introduced to Hawaii as an ornamental dicot in 1960 (Western 1992), which is a herbaceous vascular plant well known for its ability to form an ornamental ground cover. The distribution of this plant can be seen in the Kipuka system, which is home for more than 20 endemic species such as Ohia, ohelo, pukiawe, and native fern species. There has been a growing interest in the effects of transportation corridors on plant species composition, particularly in the spread and establishment of invasive non-native plant species. (Hansen and Clevenger 2005). Therefore, this study focuses on examining there is a relationship between the distance from the Saddle road and the abundance of P. capitata.
fig 1. The red flags indicates the study area inbetween the Kipuka habitats and the Saddle road.
Methodology
- A random number generator were used to find where we were going to stop off of the side of saddle road to select the transects.
2.Total of 20 transects were selected along the Saddle road. Each selected transect, were extending 30m into the Kipukas (fig 2).
fig 2. The transects are extending 30m into the lava flow and the Kipuka vegetation.
Along the 30m transect, the percent cover of P. capitata was estimated by using a quadrant (1m X 1m) (fig 3).
A random number generator was used to select the random spots along the 30 meter transect.
5.Recorded the data of each one-meter by one-meter plot.
fig 3. The percent cover of P. capitata was estimated by using a quadrant (1m X 1m).
fig 4. The figure indicates the locations of transects (tansect 15 to 20)with the study area.
Data Analysis
pc<- read.csv("Perscicaria Capitata Data.csv")
head(pc)## Transect_NO Distance Present_absent Percent_Cover
## 1 1 23 Absent 0
## 2 1 13 Present 20
## 3 1 18 Present 20
## 4 1 20 Absent 0
## 5 1 10 Present 70
## 6 2 9 Present 10#Number of transects- 1 to 20
#Distance from the road to the vegetation
#0- Pink knot weed is not present, 1- Pink knot weed is present
#Present coversummary(pc)## Transect_NO Distance Present_absent Percent_Cover
## Min. : 1.00 Min. : 0.00 Absent :51 Min. : 0.00
## 1st Qu.: 5.75 1st Qu.: 6.00 Present:49 1st Qu.: 0.00
## Median :10.50 Median :11.50 Median : 0.00
## Mean :10.50 Mean :12.54 Mean :10.74
## 3rd Qu.:15.25 3rd Qu.:20.00 3rd Qu.:12.00
## Max. :20.00 Max. :34.00 Max. :97.00Visualizing the relationships among the variables
plot(pc, col="dark blue",pch = 19, las=1) #pairs(pc)#
fig 5. There are relationships among the varibles of Transect, Distance and Percent_Cover.
library(scatterplot3d)## Warning: package 'scatterplot3d' was built under R version 3.5.2# Change color by groups
# add grids and remove the box around the plot
# Change axis labels: xlab, ylab and zlab
scatterplot3d(pc$Distance,pc$Transect_NO,pc$Percent_Cover , pch = 19, color= "blue",
grid = TRUE, box = FALSE, xlab = "Distance (m)",
ylab = "Transect Number", zlab = "Percent Cover %")
fig 6. The graph indicates how the percent cover changes within the distance in each Transect.
library("car")## Warning: package 'car' was built under R version 3.5.3## Loading required package: carData## Warning: package 'carData' was built under R version 3.5.3#The below funtion was not called here
#scatterplot(pc$Percent_Cover~pc$Distance|pc$Present_or_not , data = pc, smoother = FALSE, grid = FALSE, frame = FALSE)par(mfrow=c(3,3))
cor.test(pc$Distance, pc$Percent_Cover)##
## Pearson's product-moment correlation
##
## data: pc$Distance and pc$Percent_Cover
## t = -4.2157, df = 98, p-value = 5.549e-05
## alternative hypothesis: true correlation is not equal to 0
## 95 percent confidence interval:
## -0.5461892 -0.2116764
## sample estimates:
## cor
## -0.3918044##______________________________________________________________________________
scatterplot(Percent_Cover~Distance, data = pc)
library(ggplot2)## Warning: package 'ggplot2' was built under R version 3.5.3
ggplot(data = pc, mapping = aes(x =pc$Distance , y = pc$Percent_Cover))+ geom_point(alpha=0.3, color="blue")+
labs(y="Percent cover %", x = "Distance from the road (m)", title = "Distance Vs percent cover")+ stat_smooth(method="lm", se=FALSE, col="red") 
# regression line (y~x)fig 7. The distance and the percent cover has a negative correlation (r= -0.39, df= 98, t= -4.2157). The percent cover of P. capitata decreases when the distance from the road to vegetation increases.
library(ggplot2)boxplot(pc$Distance~pc$Present_absent , frame = TRUE, xlab = "Pink knot-weed present/absent in each quadrant", ylab = "Distance (m)", main = "Distance vs Present/absent ",las=1,
col = c("#999999", "#E69F00", "#56B4E9"))
fig 8. The graph indicates existing P. capitata at different distances.
Findings
The abundance of the P. capitata was decreasing away (fig 7) from the Saddle road. The highest distribution range was shown between 2m to 10m (fig 8). However, the distribution of this invasive plant was not seen beyond 23m away from the Saddle road (fig 8).
Conclusion
According to the researches, P.capitata was recognized as semi shade tolerant plant (Benitez et al 2018). However, during the research period, it has not been found within the Kipuka forest fragments. Therefore,it is assumed that the dense forest canopy of the kipuka act as a physical barrier for the further dispersal of P. capitata into the forest by minimize the sunlight infiltration into the ground (Hansen and Clevenger 2005).
On the other hand transportation corridors has a potential to remove the possible barriers while alters the micro-climate favorable to the growth and dispersal of non-native species. At the same time, vehicle traffic associated with the transport corridors can form air turbulence disperse the non-native exotic species to the surrounding habitats (Hansen and Clevenger 2005). However, a larger sample size is required to do a statistical analysis in order to find that Saddle road deliberately influence in the dispersal of P. capitata around the area. Therefore, further researches must be done in order to prove this.
Acknowledgement
-Mahalo for all of my group members, Trisha, Alex and Kelsey who worked together.
-Special thank goes for the professors of TCBES Masters program.