Litter decomposition:Effects of white pine invasion of old fields on biogeochemical processes

Woody plants are invading many grassland regions of the central US. At Cedar Creek, white pine (/Pinus strobus/) is successfully invading many old fields. This project aims to determine the influence of white pine invasion on biogeochemical processes. Specifically, we are testing the hypothesis that white pine reduces soil pH and base cation availability, while accelerating rates of net N mineralization and decomposition. We are testing this hypothesis by sampling soil pH; total and exchangeable base cations; total soil C, N and P; potential net N mineralization; and leaf litter decomposition under white pines and in adjacent grassy openings in 5 old fields where white pine is currently invading.

木本植物正在入侵美国中部的诸多草原区域。在锡达溪（Cedar Creek）区域，北美乔松（Pinus strobus）正成功入侵多处弃耕地。本研究旨在阐明北美乔松入侵对生物地球化学过程（biogeochemical processes）的影响。具体而言，我们将验证下述假说：北美乔松会降低土壤pH值与碱基阳离子（base cation）有效性，同时加快净氮矿化（net N mineralization）与分解过程的速率。为验证该假说，我们在5处当前正遭受北美乔松入侵的弃耕地中，分别于北美乔松林下及邻近的草本开阔地开展采样，测定的指标包括：土壤pH值、总碱基阳离子与交换性碱基阳离子含量、土壤总碳、总氮与总磷含量、潜在净氮矿化速率，以及叶片凋落物分解速率。