Wire 2 SPRUCE-specific orphan caches into SPRUCE community (#62)

* Wire 2 more SPRUCE-specific orphan caches into SPRUCE community

Both orphan papers explicitly cite the SPRUCE Spruce and Peatland
Responses Under Changing Environments experiment in northern
Minnesota that is the namesake of SPRUCE_Peatland_Methane_Cycling_
Community.

- PMID:34836550 (ter Horst et al. 2021 Microbiome, "Minnesota peat
  viromes reveal terrestrial and aquatic niche partitioning"):
  87 metagenomes + 5 viromes from the SPRUCE warming experiment
  and surrounding bog. Wired as evidence on the methanogenic
  archaea taxon - the SPRUCE viral community interacts with the
  methanogenic populations already characterized in the community.
- PMID:38515239 (Bourgault et al. 2024 New Phytologist, "Responses
  of vascular plant fine roots and associated microbial communities
  to whole-ecosystem warming and elevated CO2 in northern
  peatlands"): explicitly uses SPRUCE (+0 to +9 deg C warming and
  eCO2) to characterize the fine-root rhizosphere microbiome. Wired
  as additional evidence on the existing whole-ecosystem warming
  environmental factor.

Both papers were orphan caches with full PubMed abstracts on disk
but no community citing them; their abstracts mention SPRUCE by
name in their first paragraph, so the citation match is unambiguous.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Address Copilot review on PR #62

- Move the PMID:34836550 evidence off the methanogenic-archaea
  taxon and onto the Acidic-organic-rich-peat-chemistry
  environmental factor. The original snippet was about site
  sampling, not methanogens, so the taxon placement was a
  scope mismatch. The replacement snippet ("viral community
  composition was significantly correlated with peat depth,
  water content, and carbon chemistry, including CH4 and CO2
  concentrations") directly supports peat chemistry as a driver
  of community composition, which is the central claim of that
  environmental factor.
- Author attribution: "ter Horst" -> "Ter Horst" at sentence start
  to match citation formatting.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: realmarcin

kb/communities/SPRUCE_Peatland_Methane_Cycling_Community.yaml

@@ -139,6 +139,16 @@ environmental_factors:
     snippet: The Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment, combines
       air and peat warming in a whole-ecosystem manipulation experiment
     explanation: Supports the major experimental perturbation applied to the natural peatland community.
+  - reference: PMID:38515239
+    supports: SUPPORT
+    evidence_source: IN_VIVO
+    snippet: the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment,
+      to explore the effects of a whole-ecosystem warming gradient (+0°C to 9°C) and
+      eCO2 on vascular plant fine roots and their associated microbes
+    explanation: Bourgault et al. 2024 New Phytologist independently confirms the SPRUCE
+      warming/+eCO2 design and extends it to vascular plant fine roots and their
+      associated rhizosphere microbes - linking the manipulation to the plant-root side
+      of the same peatland system.
 - name: Acidic organic-rich peat chemistry
   value: pH 3.42 average outflow; total organic carbon 85.83 mg C/L
   description: The bog porewater chemistry is acidic and organic-carbon rich, consistent with an oligotrophic
@@ -149,6 +159,15 @@ environmental_factors:
     evidence_source: IN_VIVO
     snippet: the pH was 3.42 and total organic carbon was 85.83 mg C/L.
     explanation: Supports acidic, organic-rich conditions in the SPRUCE peatland system.
+  - reference: PMID:34836550
+    supports: SUPPORT
+    evidence_source: COMPUTATIONAL
+    snippet: viral community composition was significantly correlated with peat depth,
+      water content, and carbon chemistry, including CH4 and CO2 concentrations
+    explanation: Ter Horst et al. 2021 link the resident dsDNA viral community at SPRUCE
+      to the peatland's CH4/CO2 carbon-chemistry gradient and depth/water structure -
+      reinforcing peat chemistry (alongside the existing pH/TOC quantification) as a
+      principal driver of community composition.
 associated_datasets:
 - name: SPRUCE peat metagenomes
   dataset_type: METAGENOME