Climate change impacts of legume-grass swards: implications for organic farming in the Federal State of Brandenburg, Germany

Abstract

Multispecies legume-grass swards (LGS) within crop rotations are the primary source for nitrogen and livestock forage in organic farming systems (OFS) in Europe. At the same time, LGS are very susceptible to the effects of climate change on OFS in dryer regions. In order to predict changes in annual and seasonal LGS yields, the number and dates of LGS cuts and drought impact, an empirical statistical yield model based on alfalfa (A) and red clover (B) was applied to two of the driest areas within Germany: the 'Spreewald' (SP), with sandy soils only suited for red clover and the 'Uckermark' (UM) with sandy loams. Weather data series from 1972 to 2008 and two regional warming scenarios for 2062-2092, namely 'Dry' and 'Wet', were used to calculate the impacts. Only the scenario 'Dry' predicts an annual yield reduction (about 20 %), for both regions. This impact can be attributed to (1) the first cut is early by four weeks (decreasing the yield by 0.5 t ha -1 ), (2), the third cut is often delayed (caused by water deficiency) and (3) eventual impracticality of a fourth cut. In contrast, the second cut increased by 1 t ha -1 for 'Wet'. In SP, frequent severe drought impacts are predicted for red clover LGS. This deleterious impact of the 'Dry' scenario can be partially compensated only in UM when alfalfa is used, which showed lower susceptibility to drought. Along with the predicted yield reduction, an increased vulnerability of organic farms in both study regions cannot be prevented.

Droughts in forested ecoregions in cold and continental climates: A review of vulnerability concepts and factors in socio‐hydrological systems

“…Some of these models did, however, incorporate different forms of vulnerability indices such as drought resistance indices (Zamora‐Pereira et al, 2021), drought resilience indices (Sidor et al, 2019; Zamora‐Pereira et al, 2021), and different forms of drought threshold values (Boucher et al, 2020; Lochhead et al, 2019) for forestry, or the water depletion index (Ahopelto et al, 2019) for assessing vulnerability to water supply. Other articles using simulation models focused instead on the modeled impacts based on different model parameters (e.g., Albert et al, 2015; Bloch et al, 2015). Qualitative approaches (16% of all articles) were also used by incorporating stakeholder knowledge and opinions through interviews (Disch et al, 2012; Hurlbert & Montana, 2015), surveys (e.g., Kruse & Seidl, 2013; Olesen et al, 2011), workshops (Hill et al, 2014; Kruse & Seidl, 2013), or focus groups (McMartin et al, 2018).…”

Tree Species Selection in the Face of Drought Risk—Uncertainty in Forest Planning

“…Impact Research created three regional scale climate projections using the regional climate model STARS (Statistical Analogue Resampling Scheme) [35] by downscaling the global circulation models INM-CM4 [36], ECHAM6 [37] and ACCESS1.0 [38]. Although under debate [39,40] the climate model STARS is still recommended for climate impact assessments (e.g., [41] The projected daily mean temperature and precipitation sum of all climate stations within a 20-km distance of the respective location are interpolated to obtain climate values for each selected stand using WaSiM-ETH's distance-weighted regression model [42,43].…”

Is Biomass Accumulation in Forests an Option to Prevent Climate Change Induced Increases in Nitrate Concentrations in the North German Lowland?

“…Despite the model limitations, Wechsung and Wechsung [87] recommend STARS-based climate projections for vulnerability and uncertainty studies. For example, Bloch et al [88] assessed the regional impact of drought events on the yield of legume-grass swards under STARS climate projections for the period 2062 to 2092 and derived conclusions for future management. In any case, a possible precipitation bias introduced by STARS should be taken into account when interpreting the results.…”