Highly invasive species of Japanese knotweed (Fallopia japonica) greatly reduces plant biodiversity and creates dense thickets that degrade wildlife and affect overall ecosystem health. With principles of an aggressive root system, this species has greatly affected North America in recent years. Litter decomposition is a fundamental ecosystem process that plays key roles in nutrient cycling, primary productivity, and maintaining biodiversity. Leaf litter decomposition rates are affected by a multitude of factors. In this study, the nutrient content of the leaves and the number of invertebrates present were examined for their role in leaf decomposition. The primary objective of this research study was to examine whether decomposition rates differ depending on the colour of the leaves as this may relate to the nutrient content in the leaves. Leaf litter bags were filled with 4.0 grams of air dried leaves, with the categorization of yellow and green done through the smartphone application Color Analysis Lite was used. Using bricks and stakes, bags were placed into Clayburn Creek at the Upper and Lower sites for a total of 3 months, with removal occurring every week. The strings were cut and the bags were brought back to the lab where the leaves were cleaned and weighed, in addition to the collection and identification of the macroInvertebrates. Additionally, measurements were taken for nitrate and phosphate levels in the stream. Lastly, research results for leaf nutrient content were used to aid in understanding the decomposition rates.
Results/Conclusions
Decomposition rates were found to be highest for yellow leaves from lower Clayburn. Within both sites, there was faster decomposition of yellow leaves than green leaves. Overall, decomposition rates followed a similar trend to previous year’s datas. In contrast, no visible trends for species abundance was present and this may be due to various factors, such as large fluctuations in temperature, precipitation, and canopy coverage throughout and between the years. Additionally, comparison of different feeding types signified that the green leaves had more scrapers than the yellow leaves, indicating that the green leaves may have provided favourable conditions for algal growth. In conclusion, this study provides further insight on how colour affects decomposition rates of Japanese Knotweed leaves in freshwater ecosystems of the Fraser Valley, British Columbia.