Long-term standardized forest phenology in Sweden: a climate change indicator

Ola Langvall,Mikaell Ottosson Löfvenius

doi:10.1007/s00484-019-01817-8

Ola Langvall, Mikaell Ottosson Löfvenius

Open Access

https://doi.org/10.1007/s00484-019-01817-8

Copy DOI

Abstract

Because climate change alters patterns of vegetative growth, long-term phenological measurements and observations can provide important data for analyzing its impact. Phenological assessments are usually made as records of calendar dates when specific phase changes occur. Such assessments have benefits and are used in Citizen Science monitoring. However, these kinds of data often have low statistical precision when describing gradual changes. Frequent monitoring of the phenological traits of forest trees and berries as they undergo gradual change is needed to acquire good temporal resolution of transitions relative to other factors, such as susceptibility to frosts, insects, and fungi, and the use of berries as a food resource. Intensive weekly monitoring of the growth of apical and branch buds and the elongation of shoots and leaves on four tree species, and the abundance of flowers and berries of bilberry and lingonberry, has been performed in Sweden since 2006. Here, we present quantitative methods for interpolating such data, which detail the gradual changes between assessments in order to describe average rates of development and amount of interannual variation. Our analysis has shown the active growth period of trees to differ with latitude. We also observed a change in the timing of the maximum numbers of ripening berries and their successive decline. Data from tree phenology assessments can be used to recommend best forestry practice and to model tree growth, while berry data can be used to estimate when food resources for animals are most available.

Highlights

One of the most profound effects of a global climate change is how it changes patterns of vegetative growth
We present quantitative methods for interpolating such data, which detail the gradual changes between assessments in order to describe average rates of development and amount of interannual variation
The phenology of forest vegetation, represented here by below-canopy berries and long-lived standing trees, takes places over a period that includes both short-term weather effects as well as long-term gradual changes related to the climatic time scale

Summary

Introduction

One of the most profound effects of a global climate change is how it changes patterns of vegetative growth. Vegetation and soil together provide our principal and most essential needs of food and freshwater. Vegetative growth is highly dependent on a number of factors: a plant’s immediate general environment; its biome, characterized by the site biota; the abiotic conditions such as soil type; water availability; and in particular the local meteorological conditions. Climate is generally defined as the average state of the atmosphere and, importantly, the normal range of deviations from it (Dunlop 2001). There needs to be, a minimum number of samples taken in order to derive a suitably precise estimate of an average value for a variable and its deviation. The period over which samples are taken should ideally be long enough to include events and extremes

Methods

Results

Discussion

Conclusion